JP2018040869A - Display device, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device in which reflection under external light is suppressed, and a display device in which power consumption is reduced.SOLUTION: A display device includes a first liquid crystal element, a second liquid crystal element, a first transistor, and a second transistor. The first liquid crystal element includes a first electrode, a second electrode, and a first liquid crystal layer. The second liquid crystal element includes a third electrode, a fourth electrode, and a second liquid crystal layer. Further, one of the first and second electrodes has a function of reflecting visible light and the other has a function of transmitting the visible light. Both of the third and fourth electrodes have functions of transmitting the visible light. The first and second liquid crystal layers have an overlapping region. The first liquid crystal element is controlled by the first transistor, and the second liquid crystal element is controlled by the second transistor.SELECTED DRAWING: Figure 1

Description

  One embodiment of the present invention relates to a display device and an electronic device including the display device.

  Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. Alternatively, one embodiment of the present invention relates to a process, a machine, a manufacture, or a composition (composition of matter).

  Electronic devices typified by mobile devices such as personal computers (PCs), notebook PCs, electronic books, tablets, and smartphones are widespread. Mobile devices are required to display suitable for the brightness of the environment used such as the outdoor environment and indoor environment.

  As a display device included in an electronic apparatus, a display device in which a reflective liquid crystal display device and a transmissive liquid crystal display device are combined is proposed. For example, as a liquid crystal display device that takes advantage of the reflective liquid crystal display device and enables use in an environment where ambient illumination light is weak, a part of the incident light is transmitted and the remaining incident light is reflected. A liquid crystal display device using a so-called semi-transmissive reflective film has been proposed (see Patent Document 1).

JP 2002-372710 A

  Under external light such as in an outdoor environment, an electronic device typified by a mobile device has a problem that visibility is deteriorated due to reflection or the like. In addition, electronic devices typified by mobile devices and the like are required to reduce power consumption.

  Moreover, in the conventional liquid crystal display device using a semi-transmissive reflective film as shown in Patent Document 1, a reflective liquid crystal display device and a transmissive liquid crystal display device are realized by using one liquid crystal layer. Therefore, a step may occur in the liquid crystal layer. When a step is formed in the liquid crystal layer, problems such as a decrease in aperture ratio, a decrease in visibility, or an increase in power consumption occur. In the case of the configuration shown in Patent Document 1, a reflective liquid crystal display element and a transmissive liquid crystal display element are controlled by a single FET, so that the reflective liquid crystal display element and the transmissive liquid crystal display element are controlled. There was a problem that the display elements could not be controlled independently. Further, in the case of the configuration shown in Patent Document 1, there is a problem that the light from the backlight cannot be collected.

  In view of the above problems, an object of one embodiment of the present invention is to provide a display device in which reflection under external light is suppressed. Another object of one embodiment of the present invention is to provide a display device with low power consumption. Another object of one embodiment of the present invention is to provide a novel display device. Another object of one embodiment of the present invention is to provide a novel electronic device.

  Note that the description of these problems does not disturb the existence of other problems. Note that one embodiment of the present invention does not have to solve all of these problems. Issues other than these will be apparent from the description of the specification, drawings, claims, etc., and other issues can be extracted from the descriptions of the specification, drawings, claims, etc. It is.

  One embodiment of the present invention is a display device including a first liquid crystal element, a second liquid crystal element, a first transistor, and a second transistor. The first liquid crystal element has a function of reflecting visible light. The second liquid crystal element has a function of transmitting visible light. The first liquid crystal element is controlled by a first transistor, and the second liquid crystal element is controlled by a second transistor.

  Since the first liquid crystal element has a function of reflecting visible light, a display device in which external light is not reflected or external light is extremely small can be provided. In the display device of one embodiment of the present invention, power consumption can be reduced because the first liquid crystal element performs idling / stop driving (described later). Therefore, by using the display device of one embodiment of the present invention, a display device in which reflection under external light is suppressed and power consumption is suppressed can be provided.

  Another embodiment of the present invention is a display device including a first liquid crystal element, a second liquid crystal element, a first transistor, and a second transistor. The first liquid crystal element includes a first electrode, a second electrode, and a first liquid crystal layer. The second liquid crystal element includes a third electrode, a fourth electrode, and a second liquid crystal layer. One of the first electrode and the second electrode has a function of reflecting visible light, and the other of the first electrode and the second electrode has a function of transmitting visible light. Further, both the third electrode and the fourth electrode have a function of transmitting visible light. In addition, the first liquid crystal layer and the second liquid crystal layer each have an overlapping region. The first liquid crystal element is controlled by a first transistor, and the second liquid crystal element is controlled by a second transistor.

  In the above, any one or both of the first transistor and the second transistor preferably include a metal oxide in the semiconductor layer.

  In the above, it is preferable that the first transistor and the second transistor are arranged on the same plane.

  In the above, the specific resistance of the first liquid crystal layer preferably has a region equal to or greater than the specific resistance of the second liquid crystal layer.

In the above, it is preferable that the specific resistance of the first liquid crystal layer has a region of 1.0 × 10 ¹⁴ Ω · cm or more.

  Another embodiment of the present invention is a display device including a light emitting device, an input / output device, a first liquid crystal element, a second liquid crystal element, a first transistor, and a second transistor. It is. The first liquid crystal element has a function of reflecting visible light. The second liquid crystal element has a function of transmitting visible light. A first liquid crystal element and a second liquid crystal device are provided between the light emitting device and the input / output device. Further, the second liquid crystal element is disposed on the light emitting portion side, and the first liquid crystal element is disposed on the input / output side. One or both of the first transistor and the second transistor are disposed between the first liquid crystal element and the second liquid crystal element. The first liquid crystal element is controlled by a first transistor, and the second liquid crystal element is controlled by a second transistor.

  In the above, it is preferable that a first structure body be further provided between the first liquid crystal element and the second liquid crystal element. At this time, it is preferable that the light emitted from the light emitting device is emitted to the first liquid crystal element side through the first structure. At this time, it is preferable that the second structure body overlap the first structure body on the first structure body. At this time, it is preferable that the light emitted from the light emitting device is emitted to the first liquid crystal element side through the first structure body and the second structure body. The first structure preferably has a reflective film.

  In the above, it is preferable that the first transistor and the second transistor are driven within the same period.

  In the above, the first liquid crystal element is preferably driven at a frame frequency of 0.1 Hz to less than 60 Hz.

  In the above, it is preferable that the second liquid crystal element is driven by a time gray scale method in conjunction with a light emitting device.

  According to one embodiment of the present invention, a display device in which reflection under external light is suppressed can be provided. Alternatively, according to one embodiment of the present invention, a display device with reduced power consumption can be provided. Alternatively, according to one embodiment of the present invention, a novel display device can be provided. Alternatively, according to one embodiment of the present invention, a novel electronic device can be provided.

  Note that the description of these effects does not disturb the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. It should be noted that the effects other than these are naturally obvious from the description of the specification, drawings, claims, etc., and it is possible to extract the other effects from the descriptions of the specification, drawings, claims, etc. It is.

Sectional drawing which shows an example of a display apparatus. Sectional drawing which shows an example of a display apparatus. Sectional drawing which shows an example of a display apparatus. 10A and 10B are a schematic diagram and a state transition diagram illustrating a configuration example of a display device. 6A and 6B are a circuit diagram and a timing chart illustrating a configuration example of a display device. The perspective view which shows an example of a display apparatus. FIG. 14 illustrates a block diagram of a display device and a pixel unit. FIG. 6 illustrates a pixel unit of a display device. FIG. 14 illustrates a block diagram of a display device and a pixel unit. FIG. 14 illustrates a block diagram of a display device and pixels. FIG. 6 is a circuit diagram illustrating an example of a display device. FIG. 6 is a circuit diagram illustrating an example of a display device. 6 is a timing chart illustrating an operation method of a display device. The figure which shows an example of a display module. FIG. 14 illustrates an example of an electronic device.

  Hereinafter, embodiments will be described with reference to the drawings. However, the embodiments can be implemented in many different modes, and it is easily understood by those skilled in the art that the modes and details can be variously changed without departing from the spirit and scope thereof. . Therefore, the present invention should not be construed as being limited to the description of the following embodiments.

  In addition, the ordinal numbers “first”, “second”, and “third” used in the present specification are attached to avoid confusion between components, and are not limited numerically. Appendices.

  In addition, in this specification, terms indicating arrangement such as “above” and “below” are used for convenience to describe the positional relationship between components with reference to the drawings. Moreover, the positional relationship between components changes suitably according to the direction which draws each structure. Therefore, the present invention is not limited to the words and phrases described in the specification, and can be appropriately rephrased depending on the situation.

  In addition, in this specification and the like, “electrically connected” includes a case of being connected via “thing having some electric action”. Here, the “thing having some electric action” is not particularly limited as long as it can exchange electric signals between connection targets. For example, “thing having some electric action” includes electrodes, wiring, switching elements such as transistors, resistance elements, inductors, capacitors, and other elements having various functions.

  In this specification and the like, the term “leakage current” may be used in the same meaning as off-state current. In this specification and the like, off-state current may refer to current that flows between a source and a drain when a transistor is off, for example.

  In this specification and the like, even when expressed as “semiconductor”, for example, when the conductivity is sufficiently low, the semiconductor device may have characteristics as an “insulator”. Further, the boundary between “semiconductor” and “insulator” is ambiguous, and there is a case where it cannot be strictly distinguished. Therefore, the “semiconductor” in this specification and the like can be called an “insulator” in some cases. Similarly, an “insulator” in this specification and the like can be called a “semiconductor” in some cases. Alternatively, the “insulator” in this specification and the like can be referred to as a “semi-insulator” in some cases.

  In this specification and the like, even when expressed as “semiconductor”, for example, when the conductivity is sufficiently high, the semiconductor device may have characteristics as a “conductor”. Further, the boundary between the “semiconductor” and the “conductor” is ambiguous, and there are cases where it cannot be strictly distinguished. Therefore, a “semiconductor” in this specification and the like can be called a “conductor” in some cases. Similarly, a “conductor” in this specification and the like can be called a “semiconductor” in some cases.

(Embodiment 1)
In this embodiment, a display device of one embodiment of the present invention and a method for driving the display device will be described.

  The display device of one embodiment of the present invention is a display device in which a first display element that reflects visible light and a second display element that transmits visible light are mixed.

  The display device has a function of displaying an image using one or both of first light reflected by the first display element and second light transmitted by the second display element. Alternatively, the display device expresses gradation by controlling the amount of the first light reflected by the first display element and the amount of the second light transmitted by the second display element, respectively. It has a function.

  In addition, the display device controls the first pixel that expresses gradation by controlling the amount of reflected light from the first display element, and the gradation by controlling the amount of transmitted light from the second display element. A structure including the second pixel to be expressed is preferable. A plurality of first pixels and second pixels are arranged in a matrix, for example, and constitute a display unit.

  In addition, it is preferable that the first pixels and the second pixels are arranged in the display area with the same number and the same pitch. At this time, the adjacent first pixel and second pixel can be collectively referred to as a pixel unit.

  Furthermore, it is preferable that the first pixel and the second pixel are arranged in a mixed manner in the display region of the display device. Thereby, as will be described later, both the image displayed only with the plurality of first pixels, the image displayed only with the plurality of second pixels, and the plurality of first pixels and the plurality of second pixels. Each of the images displayed in can be displayed in the same display area.

  As the first display element included in the first pixel, an element that reflects external light for display can be used. Since such an element does not have a light source, power consumption during display can be extremely reduced.

  As the first display element, a reflective liquid crystal element can be typically used. Alternatively, as a first display element, in addition to a shutter-type MEMS (Micro Electro Mechanical System) element, an optical interference-type MEMS element, a microcapsule type, an electrophoretic method, an electrowetting method, and an electronic powder fluid (registered trademark) An element to which a method or the like is applied can be used.

  The second display element included in the second pixel can be an element that displays light by transmitting light from a light source. As the display element included in the second pixel, a combination of a backlight which is a light source and a transmissive liquid crystal element which controls the amount of transmitted light from the backlight can be used.

  The first pixel can include a sub-pixel that exhibits, for example, white (W), or a sub-pixel that exhibits three colors of light, for example, red (R), green (G), and blue (B). . Similarly, the second pixel has a sub-pixel that exhibits, for example, white (W), or a sub-pixel that exhibits light of three colors, for example, red (R), green (G), and blue (B). can do. Note that the subpixels included in each of the first pixel and the second pixel may have four or more colors. As the number of subpixels increases, power consumption can be reduced and color reproducibility can be improved.

  According to one embodiment of the present invention, a first mode in which an image is displayed with a first pixel, a second mode in which an image is displayed with a second pixel, and an image is displayed with the first pixel and the second pixel. The third mode can be switched.

  The first mode is a mode in which an image is displayed using reflected light from the first display element. The first mode is a driving mode with extremely low power consumption because no light source is required. For example, it is effective when the illuminance of outside light is sufficiently high and the outside light is white light or light in the vicinity thereof. The first mode is a display mode suitable for displaying character information such as books and documents. In addition, since the reflected light is used, it is possible to perform display that is kind to the eyes, and the effect that the eyes are less tired is achieved. Note that the first mode may be referred to as a reflection type display mode because it displays using reflected light.

  In the second mode, an image is displayed using light transmitted by the second display element. Therefore, an extremely vivid display (high contrast and high color reproducibility) can be performed regardless of the illuminance and chromaticity of external light. For example, it is effective when the illuminance of outside light is extremely small, such as at night or in a dark room. Further, when the outside light is dark, the user may feel dazzled when performing bright display. In order to prevent this, it is preferable to perform display with reduced luminance in the second mode. Thereby, in addition to suppressing glare, power consumption can also be reduced. The second mode is a mode suitable for displaying a vivid image or a smooth moving image. Note that the second mode may be referred to as a transmissive display mode (transmission mode) because display is performed using transmitted light.

  The third mode is a mode in which display is performed using both reflected light from the first display element and transmitted light from the second display element. Specifically, driving is performed so as to express one color by mixing light emitted by the first pixel and light emitted by the second pixel adjacent to the first pixel. While displaying more vividly than in the first mode, it is possible to suppress power consumption as compared with the second mode. For example, it is effective when the illuminance of outside light is relatively low, such as under room lighting or in the morning or evening hours, or when the chromaticity of outside light is not white.

  Note that in this specification and the like, display in which the first display element and the second display element are combined, that is, the third mode can be referred to as a hybrid display mode (HB display mode). Alternatively, the third mode may be referred to as a display mode (TR-Hybrid mode) in which a transmissive display mode and a reflective display mode are combined.

  Here, as a structure of the display device, a structure having a display panel including the first pixel and the second pixel and a control unit can be employed. The control unit generates and outputs a first gradation value to be output to the first pixel and a second gradation value to be output to the second pixel based on image information input from the outside. Here, the image information is information including gradation values corresponding to each pixel unit, and examples thereof include video signals such as video signals.

  Note that the control unit may have a function of selecting the display mode described above based on the illuminance of external light or the like.

  In the display device, the first pixel includes a first transistor electrically connected to the first display element, and the second pixel is electrically connected to the second display element. It is preferable to have a second transistor.

  At this time, it is preferable that the first transistor and the second transistor are formed on the same surface. At this time, either the first display element or the second display element is preferably electrically connected to the first transistor or the second transistor through an opening provided in the insulating layer. . Accordingly, since the first transistor and the second transistor can be manufactured in the same process, the process can be simplified.

  In addition, by adopting a structure in which the first display element, the second display element, and each transistor are sandwiched between a pair of substrates, a thin and lightweight display device can be realized.

  The second display element using transmitted light can have a structure in which a backlight and a transmissive display element are combined. At this time, by using a light source that emits white light as a backlight and the second display element has a colored layer (color filter), a structure capable of color display can be obtained.

  The second display element may have a structure for performing color display by a time gray scale method (also referred to as a field sequential method). At this time, a red (R), green (G), and blue (B) light can be dispersed as a backlight and a light source capable of repeatedly emitting light can be used. That is, color display can be performed by the time gray scale method by interlocking the second display element and the backlight.

  At this time, in order to prevent a change in luminance from being perceived as flicker (flicker), it is preferable to increase a cycle (also referred to as a drive frequency or a subframe frequency) for changing the color of light of the backlight. For example, the driving frequency can be 30 Hz to 720 Hz, preferably 60 Hz to 360 Hz, more preferably 60 Hz to 240 Hz, typically 180 Hz.

  Hereinafter, more specific examples of one embodiment of the present invention will be described with reference to the drawings.

<Specific examples of the first to third modes>
Here, a specific example in the case where the above-described first to third modes are used will be described with reference to FIGS.

  Hereinafter, a case where the first to third modes are automatically switched according to the illuminance will be described. In addition, when switching automatically according to illumination intensity, an illumination sensor etc. can be provided in a display apparatus, for example, and a display mode can be switched based on the information from the said illumination intensity sensor.

  4A, 4 </ b> B, and 4 </ b> C are schematic diagrams of pixels for explaining display modes that the display device of this embodiment can take.

  4A, 4B, and 4C, the first display element 501, the second display element 502, the opening 503, the reflected light 504 reflected from the first display element 501, and the second display The transmitted light 505 emitted from the element 502 through the opening 503 is clearly shown. 4A is a diagram for explaining the first mode, FIG. 4B is a diagram for explaining the second mode, and FIG. 4C is a diagram for explaining the third mode. It is.

  4A, 4B, and 4C, a reflective liquid crystal element is used as the first display element 501, and a transmissive liquid crystal element is used as the second display element 502.

  In the first mode shown in FIG. 4A, grayscale display can be performed by adjusting the intensity of reflected light by driving a reflective liquid crystal element which is the first display element 501. For example, as shown in FIG. 5A, gradation display is performed by adjusting the intensity of reflected light 504 with a liquid crystal layer using a reflective electrode included in a reflective liquid crystal element which is the first display element 501. be able to.

  In the second mode illustrated in FIG. 4B, grayscale display can be performed by adjusting the intensity of transmitted light by driving a transmissive liquid crystal element which is the second display element 502. Note that light emitted from the second display element 502 passes through the opening 503 and is extracted to the outside as transmitted light 505.

  The third mode shown in FIG. 4C is a display mode in which the first mode and the second mode described above are combined. For example, the reflective electrode included in the reflective liquid crystal element which is the first display element 501 is used to perform gradation display by adjusting the intensity of the reflected light 504 with the liquid crystal layer. Further, the intensity of the transmitted light of the transmissive liquid crystal element, which is the second display element 502, in this case, the intensity of the transmitted light 505 is adjusted in the same period as the period during which the first display element 501 is driven. Displays the key.

<State transition in first to third modes>
Next, state transition in the first to third modes will be described with reference to FIG. FIG. 4D is a state transition diagram of the first mode, the second mode, and the third mode. The state C1 shown in FIG. 4D corresponds to the first mode, the state C2 corresponds to the second mode, and the state C3 corresponds to the third mode.

  As shown in FIG. 4D, from the state C1 to the state C3, a display mode in any state can be taken according to the illuminance. For example, when the illuminance is high, such as outdoors, the state C1 can be taken. In addition, when the illuminance is low, such as when moving from outdoors to indoors, the state changes from state C1 to state C2. Further, when the illuminance is low even outdoors, and the gradation display by reflected light is not sufficient, the state C2 is changed to the state C3. Of course, a transition from state C3 to state C1, a transition from state C1 to state C3, a transition from state C3 to state C2, or a transition from state C2 to state C1 also occurs.

  In FIG. 4D, the sun symbol is illustrated as the first mode image, the moon symbol is illustrated as the second mode image, and the cloud symbol is illustrated as the third mode image. It is.

  As shown in FIG. 4D, in the state C1 to the state C3, when there is no change in illuminance or when the change in illuminance is small, without changing to another state, the original state is continued. Should be maintained.

  As described above, with the configuration in which the display mode is switched according to the illuminance, it is possible to reduce the frequency of gradation display of a transmissive liquid crystal element that requires a light source such as a backlight with relatively high power consumption. Therefore, power consumption of the display device can be reduced. The display device can further switch the operation mode according to the remaining capacity of the battery, the content to be displayed, or the illuminance of the surrounding environment. In the above description, the case where the display mode is automatically switched according to the illuminance is illustrated, but the present invention is not limited to this, and the user may manually switch the display mode.

<Operation mode>
Next, operation modes that can be performed in the first display element will be described with reference to FIGS.

  In the following, a normal operation mode (Normal mode) that operates at a normal frame frequency (typically 60 MHz to 240 MHz or less) and an idling stop (IDS) drive mode that operates at a low frame frequency will be exemplified. To explain.

  Note that the idling stop (IDS) driving mode refers to a driving method in which rewriting of image data is stopped after image data writing processing is executed. Once the image data is written and then the interval until the next image data is written is extended, the power consumption required for writing the image data during that time can be reduced. The idling stop (IDS) drive mode can be set to a frame frequency about 1/100 to 1/10 of the normal operation mode, for example.

5A, 5B, and 5C are circuit diagrams and timing charts for explaining the normal drive mode and the idling stop (IDS) drive mode. Note that FIG. 5A clearly shows the first display element 501 (here, a reflective liquid crystal element) and a pixel circuit 506 electrically connected to the first display element 501. 5A, the signal line SL, the gate line GL, the transistor M1 connected to the signal line SL and the gate line GL, and the capacitor Cs _LC connected to the transistor M1 Is illustrated.

  As the transistor M1, a transistor including a metal oxide in a semiconductor layer is preferably used. When the metal oxide has at least one of an amplifying function, a rectifying function, and a switching function, the metal oxide is referred to as a metal oxide semiconductor or an oxide semiconductor, or OS for short. be able to. Hereinafter, a transistor including an oxide semiconductor (OS transistor) will be described as a typical example of a transistor. Since the OS transistor has a very low leakage current (off-state current) in a non-conduction state, electric charge can be held in the pixel electrode of the liquid crystal element by making the OS transistor non-conduction.

Note that in the circuit diagram shown in FIG. 5 (A), the liquid crystal element LC is the leak path of the data _{D 1.} Therefore, in order to appropriately perform idling stop driving, it is preferable that the resistivity of the liquid crystal element LC is 1.0 × 10 ¹⁴ Ω · cm or more.

  Note that an In—Ga—Zn oxide, an In—Zn oxide, or the like can be preferably used for the channel region of the OS transistor, for example. As the In—Ga—Zn oxide, a composition in the vicinity of In: Ga: Zn = 4: 2: 4.1 [atomic ratio] can be typically used.

FIG. 5B is a timing chart showing waveforms of signals supplied to the signal line SL and the gate line GL in the normal drive mode. In the normal drive mode, it operates at a normal frame frequency (for example, 60 Hz). When one frame period is represented by periods T ₁ to T ₃ , an operation of applying a scanning signal to the gate line GL and writing data D ₁ from the signal line SL in each frame period is performed. This operation is the same even when writing the same data D ₁ in the period T ₁ to T ₃ or writing different data.

On the other hand, FIG. 5C is a timing chart showing waveforms of signals applied to the signal line SL and the gate line GL in the idling stop (IDS) driving mode. The idling stop (IDS) drive operates at a low frame frequency (for example, 1 Hz). Represents one frame period in the period T _1, representing the period T _W a write period of data _therein, the data retention period in the period T _RET. Idling stop (IDS) drive mode, it provides a scan signal to the gate line GL in a period _{T W,} write data _{D 1} of the signal line SL, and a gate line GL is fixed to the low level of the voltage in the period _{T RET,} transistor performs an operation of holding temporarily the data D ₁ is written M1 as a non-conductive state. Note that the low-speed frame frequency may be, for example, 0.1 Hz or more and less than 60 Hz.

  The idling stop (IDS) drive mode is effective because it can further reduce power consumption by combining with the first mode or the third mode described above.

  As described above, the display device of this embodiment can perform display by switching the first mode to the third mode. Therefore, it is possible to realize a display device or an all-weather display device that is highly visible and convenient regardless of the surrounding brightness.

  In addition, the display device of this embodiment preferably includes a plurality of first pixels each including a first display element and a plurality of second pixels each including a second display element. In addition, the first pixel and the second pixel are preferably arranged in a matrix.

  Each of the first pixel and the second pixel can include one or more subpixels. For example, the pixel has a configuration having one subpixel (white (W), etc.), a configuration having three subpixels (red (R), green (G), and blue (B), etc.), Alternatively, a configuration having four subpixels (red (R), green (G), blue (B), white (W), or red (R), green (G), blue (B), Yellow (Y) and the like can be applied. Note that the color elements included in the first pixel and the second pixel are not limited to the above, and cyan (C), magenta (M), and the like may be combined as necessary.

  In the display device of this embodiment, both the first pixel and the second pixel can perform full color display. Alternatively, the display device in this embodiment can have a structure in which the first pixel performs monochrome display or grayscale display, and the second pixel performs full color display. The monochrome display or grayscale display using the first pixel is suitable for displaying information that does not require color display, such as document information.

<Schematic perspective view of display device>
Next, the display device of this embodiment will be described with reference to FIG. FIG. 6 is a schematic perspective view of the display device 510.

  The display device 510 has a structure in which a substrate 511 and a substrate 512 are attached to each other. In FIG. 6, the substrate 512 is clearly indicated by a broken line.

  The display device 510 includes a display portion 514, a circuit 516, a wiring 518, and the like. FIG. 6 shows an example in which an IC 520 and an FPC 522 are mounted on the display device 510. Therefore, the structure illustrated in FIG. 6 can also be referred to as a display module including the display device 510, the IC 520, and the FPC 522.

  As the circuit 516, for example, a scan line driver circuit can be used.

  The wiring 518 has a function of supplying a signal and power to the display portion 514 and the circuit 516. The signal and power are input to the wiring 518 from the outside through the FPC 522 or from the IC 520.

  FIG. 6 illustrates an example in which the IC 520 is provided on the substrate 511 by a COG (Chip On Glass) method, a COF (Chip on Film) method, or the like. As the IC 520, for example, an IC having a scan line driver circuit, a signal line driver circuit, or the like can be used. Note that the display device 510 may have a structure in which the IC 520 is not provided. Further, the IC 520 may be mounted on the FPC by a COF method or the like.

  FIG. 6 shows an enlarged view of a part of the display unit 514. In the display portion 514, electrodes 524 included in the plurality of display elements are arranged in a matrix. The electrode 524 has a function of reflecting visible light and functions as a reflective electrode of the liquid crystal element 550 (described later).

  As shown in FIG. 6, the electrode 524 has an opening 526. Further, the display portion 514 includes a transmissive liquid crystal element 570 closer to the substrate 511 than the electrode 524. Light from the liquid crystal element 570 is emitted to the substrate 512 side through the opening 526 of the electrode 524. The area of the transmission region of the liquid crystal element 570 and the area of the opening 526 may be equal. One of the area of the transmissive region of the liquid crystal element 570 and the area of the opening 526 is larger than the other, which is preferable because a margin for positional deviation is increased.

  Hereinafter, specific cross-sectional structures of the display device of one embodiment of the present invention will be described with reference to FIGS. 1 to 3 are cross-sectional views illustrating an example of a display device of one embodiment of the present invention.

  1 is a cross-sectional view illustrating the display device 100A, FIG. 2 is a cross-sectional view illustrating the display device 100B, and FIG. 3 is a cross-sectional view illustrating the display device 100C.

<Cross-section configuration example 1>
First, the display device 100A will be described with reference to FIG.

  The display device 100 </ b> A includes a first substrate 102 and a second substrate 104. Between the first substrate 102 and the second substrate 104, the first liquid crystal element 106 and the second substrate 104 are provided. The liquid crystal element 108 is sandwiched.

  In addition, the first liquid crystal element 106 includes a first electrode 106PE, a second electrode 106CE, and a first liquid crystal layer 106LC located between the first electrode 106PE and the second electrode 106CE. . In addition, the second liquid crystal element 108 includes a third electrode 108PE, a fourth electrode 108CE, and a second liquid crystal layer 108LC located between the third electrode 108PE and the fourth electrode 108CE. .

  In addition, an element layer 110 is provided between the first liquid crystal element 106 and the second liquid crystal element 108. In this embodiment mode, a first transistor 111 and a second transistor 112 are formed in the element layer 110.

  In addition, the first transistor 111 is disposed so as to overlap with the first electrode 106PE, and partly separated from the first electrode 106PE with an insulating film (here, a plurality of insulating films) interposed therebetween. Is done. Note that the first electrode 106PE and the first transistor 111 are electrically connected to each other through the first opening 114 formed in the insulating film and the electrode 116 formed in the first opening 114. Is done. The electrode 116 may be referred to as a connection electrode or a through electrode.

  In addition, the second transistor 112 is disposed so as to overlap with the third electrode 108PE, and partly separated from the third electrode 108PE with an insulating film (here, a plurality of insulating films) interposed therebetween. Be placed. Note that the third electrode 108PE and the second transistor 112 are electrically connected through the second opening 118 formed in the insulating film.

  Note that the first liquid crystal element 106 has a function of displaying an image by reflecting light, and the second liquid crystal element 108 has a function of displaying an image by transmitting light. In other words, the first liquid crystal element 106 is a reflective liquid crystal element, and the second liquid crystal element 108 is a transmissive liquid crystal element.

  A light emitting device 122 is disposed below the second substrate 104 with a polarizing plate 120 interposed therebetween. The light emitting device 122 has a function as a so-called backlight unit, and includes an edge light 122E, a light guide plate 122G, a light extraction unit 122R, and the like.

  In FIG. 1, light emitted from the edge light 122E is indicated by a dotted arrow. In the light emitting device 122, the light emitted from the edge light 122E passes through the light guide plate 122G, is collected by the light extraction unit 122R, and is emitted to the second liquid crystal element 108 side. That is, the light extraction portion 122R has a function as a so-called lens (also referred to as a microlens).

  In addition, the first structural body 124 is provided in the element layer 110 that overlaps the light extraction portion 122R. The first structure 124 has at least a reflective film 124R. The light that has passed through the light extraction portion 122R is further collected by the reflective film 124R included in the first structure 124, and is emitted to the first substrate 102 side.

  The reflective film 124R included in the first structure 124 has a shape such that the inner wall continuously decreases in width from the incident side (substrate 104 side) to the emission side (substrate 102 side). For example, you may have the shape which cut off a part of cone. In particular, it is preferable that the inner wall has a constricted three-dimensional curved surface shape (for example, a trumpet shape). In addition, the inner wall of the reflective film 124R preferably has a shape close to a hyperbola in the surface of a pair of opposed inner walls in a cross section perpendicular to the substrate 104 or the like.

  Since the first structure 124 has the shape as described above, light emitted from the light extraction unit 122R and transmitted through the second liquid crystal element 108 is incident on the first structure 124 in an oblique direction. Is reflected by the reflective film 124R of the first structure 124, thereby increasing the luminance (light flux per unit area).

  The smaller the opening area on the exit side of the reflection film 124R of the first structure 124 is, the more the inclination angle of the side surface of the reflection film 124R (the angle formed between the side surface and the surface of the substrate 102, etc.). The closer to 90 degrees and the higher the reflectivity of the reflective film 124R, the higher the luminance of the light transmitted through the first structure 124 can be.

  In addition, the region surrounded by the reflective film 124R of the first structure 124 preferably has a high light transmittance. For example, it is preferable to use a material containing aluminum or silver. In addition, the region preferably has a high refractive index. For example, it is preferable to use a material having an absolute refractive index greater than 1 and 2.5 or less, preferably 1.2 or more and 2.0 or less, and more preferably 1.3 or more and 1.9 or less.

  The second structure 126 is provided above the first structure 124 and between the first electrode 106PE and the second electrode 106CE. The second structure 126 has a function of controlling the distance between the first electrode 106PE and the second electrode 106CE. That is, the second structure body 126 has a function as a so-called gap spacer or cell gap spacer.

  The second structure 126 preferably transmits visible light. The light condensed by the first structure 124 is emitted to the first substrate 102 side through the second structure 126. In addition, by providing the second structure body 126 above the first structure body 124, the light emitted from the edge light 122E has a function of suppressing absorption by the first liquid crystal layer 106LC.

  In addition, a diffusion film 128, an input / output device 130 on the diffusion film 128, and a polarizing plate 132 on the input / output device 130 are provided above the first substrate 102.

  The input / output device 130 functions as a so-called touch panel or touch sensor.

<Cross-section configuration example 2>
Next, the display device 100B will be described with reference to FIG. Note that the display device 100B is a modification of the display device 100A described above.

  In addition to the structure of the display device 100A described above, the display device 100B includes an insulating layer 134, a coloring layer 136, and an insulating layer 138 between the second electrode 106CE and the substrate 102.

  The colored layer 136 has a function as a so-called color filter. The insulating layer 138 has a function of controlling the thickness of the colored layer 136.

  For example, as illustrated in FIG. 2, the insulating layer 138 is provided in a portion overlapping with the first liquid crystal element 106 and has an opening in a portion overlapping with the second liquid crystal element 108. Accordingly, the colored layer 136 provided so as to cover the insulating layer 138 can be formed so that the portion overlapping the second liquid crystal element 108 is thicker than the portion overlapping the first liquid crystal element 106. Accordingly, the thickness of the colored layer 136 positioned on the optical path is different between the first liquid crystal element 106 that is a reflective liquid crystal element and the second liquid crystal element 108 that is a transmissive liquid crystal element. be able to.

  In FIG. 2, the liquid crystal layer 108 LC has a configuration in which both ends thereof are surrounded by the resin layer 142. The resin layer 142 includes, for example, a resin and a liquid crystal material included in the liquid crystal layer 108LC. By having the resin layer 142, the adhesiveness between the element layer 110 and the substrate 104 is increased, and the mechanical strength of the display device 100B can be increased.

<Cross-section configuration example 3>
Next, the display device 100C will be described with reference to FIG. The display device 100C is a modification of the display device 100A and the display device 100B described above.

  In the display device 100C, the transistor 111 and the transistor 112 are formed over different insulating surfaces.

  More specifically, the transistor 112 is provided over the substrate 104. Further, the transistor 111 and the transistor 112 are positioned so as to sandwich the second liquid crystal element 108.

  In addition, the coloring layer 140 is provided between the second liquid crystal element 108 and the first structure body 124. The light emitted from the light extraction portion 122R and transmitted through the second liquid crystal element 108 passes through the colored layer 140, the first structure body 124, and the second structure body 126, and is emitted toward the substrate 102 side.

<Components>
Next, each component shown in FIGS. 1 to 3 will be described below.

[substrate]
As the substrates 102 and 104, a light-transmitting substrate can be used. For example, glass substrates such as barium borosilicate glass, alumino borosilicate glass, alkali-free glass, soda lime glass, potash glass, crystal glass, aluminosilicate glass, tempered glass, chemically tempered glass, sapphire glass, quartz substrate, plastic substrate, resin A film or the like can be used.

Note that aluminosilicate glass, tempered glass, chemically tempered glass, sapphire, or the like can be suitably used for the second substrates 102 and 104 disposed on the side closer to the user of the display panel. Thereby, it is possible to prevent the display panel from being damaged or damaged due to use. The substrate can be made of, for example, a material having a thickness of 0.7 mm or less and a thickness of 0.1 mm or more. Specifically, a material polished to a thickness of about 0.1 mm can be used.

[electrode]
As the first electrode 106PE, a reflective conductive film that reflects visible light can be used. For example, tungsten (W), molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), cobalt (Co), nickel (Ni ), Titanium (Ti), platinum (Pt), aluminum (Al), copper (Cu), silver (Ag), palladium (Pd), or other metals, or alloys thereof, or metal nitrides thereof. It can be formed using seeds. The light-transmitting conductive film may be stacked with the reflective conductive film. Further, unevenness may be provided on the surfaces of the second pixel electrode layers 167a and 167b. Thereby, incident light can be reflected in various directions to display white.

  As the second electrode 106CE, the third electrode 108PE, and the fourth electrode 108CE, a light-transmitting conductive film that transmits visible light can be used. For example, In-Sn oxide, In-Zn oxide, In-Si-Sn oxide, In-W oxide, In-W-Zn oxide, In-Ti oxide, In-Ti-Sn oxide, Graphene or the like can be used.

[Liquid crystal layer]
As the first liquid crystal layer 106LC and the second liquid crystal layer 108LC, for example, a nematic liquid crystal or a liquid crystal material exhibiting a blue phase can be used. Further, a negative liquid crystal or a positive liquid crystal can be used. For example, a negative liquid crystal can be used for a VA mode display element, and a positive liquid crystal can be used for a TN mode display element.

  In addition, a liquid crystal material including a polymer network can be used for the first liquid crystal layer 106LC and the second liquid crystal layer 108LC. For example, a composite material including a liquid crystal material and a polymer phase-separated from the liquid crystal material can be used for the first liquid crystal layer 106LC and the second liquid crystal layer 108LC. Specifically, a polymer that is phase-separated from the liquid crystal material can be produced by a method of photopolymerizing a mixture containing the monomer and the liquid crystal material.

  Note that in the drawing, although not shown, an alignment film may be formed in contact with the first liquid crystal layer 106LC and the second liquid crystal layer 108LC. As the alignment film, for example, a material containing polyimide or the like can be used. Specifically, a material formed using a rubbing process or a photo-alignment technique so that the liquid crystal material is aligned in a predetermined direction can be used.

[Transistor]
As the first transistor 111 and the second transistor 112, various metal oxides such as a metal oxide containing indium or a metal oxide containing indium, gallium, and zinc can be used for the semiconductor layer. Note that as the first transistor 111 and the second transistor 112, a semiconductor containing silicon can be used for a semiconductor layer. For example, single crystal silicon, polysilicon, microcrystalline silicon, amorphous silicon, or the like can be used.

  However, it is preferable to use a metal oxide containing indium, gallium, and zinc for the semiconductor layer. A transistor using a metal oxide as a semiconductor film has an advantage of low leakage current in an off state. Therefore, the time during which the pixel circuit can hold the image signal can be extended. Specifically, the selection signal can be supplied at a frequency of less than 30 Hz, preferably less than 1 Hz, and more preferably less than 0.1 Hz while suppressing the occurrence of flicker. As a result, fatigue accumulated in the user of the display device can be reduced. In addition, power consumption associated with driving can be reduced.

  The transistor includes a conductive layer that functions as a gate electrode, a semiconductor layer, a conductive layer that functions as a source electrode, a conductive layer that functions as a drain electrode, and an insulating layer that functions as a gate insulating layer. The above shows the case where a bottom-gate transistor is applied.

  Note that there is no particular limitation on the structure of the transistor included in the display device of one embodiment of the present invention. For example, a planar transistor, a staggered transistor, or an inverted staggered transistor may be used. Further, a top-gate or bottom-gate transistor structure may be employed. Alternatively, gate electrodes may be provided above and below the channel.

  There is no particular limitation on the crystallinity of the semiconductor material used for the transistor, and either an amorphous semiconductor or a semiconductor having crystallinity (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor partially including a crystal region) is used. May be used. It is preferable to use a crystalline semiconductor because deterioration of transistor characteristics can be suppressed.

  As a semiconductor material used for the transistor, a metal oxide having an energy gap of 2 eV or more, preferably 2.5 eV or more, more preferably 3 eV or more can be used. Typically, a metal oxide containing indium, for example, a CAC-OS described later can be used.

  A transistor using a metal oxide having a wider band gap and lower carrier density than silicon retains charges accumulated in a capacitor connected in series with the transistor for a long period of time due to its low off-state current. Is possible.

  The semiconductor layer is represented by an In-M-Zn-based oxide containing indium, zinc, and M (metal such as aluminum, titanium, gallium, germanium, yttrium, zirconium, lanthanum, cerium, tin, neodymium, or hafnium). It can be a membrane.

  When the metal oxide composing the semiconductor layer is an In-M-Zn-based oxide, the atomic ratio of the metal element of the sputtering target used for forming the In-M-Zn oxide is In ≧ M, Zn It is preferable to satisfy ≧ M. As the atomic ratio of the metal elements of such a sputtering target, In: M: Zn = 1: 1: 1, In: M: Zn = 1: 1: 1.2, In: M: Zn = 3: 1: 2, In: M: Zn = 4: 2: 3, 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 etc. are preferable. Note that the atomic ratio of the semiconductor layer to be formed includes a variation of plus or minus 40% of the atomic ratio of the metal element contained in the sputtering target.

  The bottom-gate transistor described in this embodiment is preferable because the number of manufacturing steps can be reduced. In addition, by using a metal oxide at this time, the wiring under the semiconductor layer can be formed at a temperature lower than that of polycrystalline silicon, and a material having low heat resistance can be used as an electrode material and a substrate material. Can widen the choice of materials. For example, a glass substrate having an extremely large area can be suitably used.

As the semiconductor layer, a metal oxide film with low carrier density is used. For example, the semiconductor layer has a carrier density of 1 × 10 ¹⁷ / cm ³ or less, preferably 1 × 10 ¹⁵ / cm ³ or less, more preferably 1 × 10 ¹³ / cm ³ or less, more preferably 1 × 10 ¹¹ / cm 3. ³ or less, more preferably less than 1 × ^{10 10} / cm ^3, it is possible to use a 1 × ¹⁰ -9 / cm ³ metal oxide or more carrier density. Such metal oxides are referred to as high purity intrinsic or substantially high purity intrinsic metal oxides. Accordingly, it can be said that the metal oxide has stable characteristics because the impurity concentration is low and the density of defect states is low.

  Note that the composition is not limited thereto, and a transistor having an appropriate composition may be used depending on required semiconductor characteristics and electrical characteristics (such as field-effect mobility and threshold voltage) of the transistor. In addition, in order to obtain the required semiconductor characteristics of the transistor, it is preferable that the semiconductor layer have appropriate carrier density, impurity concentration, defect density, atomic ratio of metal element to oxygen, interatomic distance, density, and the like. .

If the metal oxide constituting the semiconductor layer contains silicon or carbon which is one of the Group 14 elements, oxygen vacancies increase in the semiconductor layer and become n-type. Therefore, the concentration of silicon or carbon in the semiconductor layer (concentration obtained by secondary ion mass spectrometry) is 2 × 10 ¹⁸ atoms / cm ³ or less, preferably 2 × 10 ¹⁷ atoms / cm ³ or less.

In addition, when alkali metal and alkaline earth metal are combined with a metal oxide, carriers may be generated, which may increase the off-state current of the transistor. Therefore, the concentration of alkali metal or alkaline earth metal obtained by secondary ion mass spectrometry in the semiconductor layer is set to 1 × 10 ¹⁸ atoms / cm ³ or less, preferably 2 × 10 ¹⁶ atoms / cm ³ or less.

In addition, when nitrogen is contained in the metal oxide constituting the semiconductor layer, electrons as carriers are generated, the carrier density is increased, and the n-type is easily obtained. As a result, a transistor using a metal oxide containing nitrogen is likely to be normally on. For this reason, it is preferable that the nitrogen concentration obtained by secondary ion mass spectrometry in the semiconductor layer is 5 × 10 ¹⁸ atoms / cm ³ or less.

  The semiconductor layer may have a non-single crystal structure, for example. The non-single-crystal structure includes, for example, a CAAC-OS (C-Axis Crystalline Oxide Semiconductor) having a crystal oriented in the c-axis, a polycrystalline structure, a microcrystalline structure, or an amorphous structure. In the non-single-crystal structure, the amorphous structure has the highest density of defect states, and the CAAC-OS has the lowest density of defect states.

  An amorphous metal oxide film has, for example, disordered atomic arrangement and no crystal component. Alternatively, an amorphous oxide film has, for example, a completely amorphous structure and does not have a crystal part.

  Note that the semiconductor layer may be a mixed film including two or more of an amorphous structure region, a microcrystalline structure region, a polycrystalline structure region, a CAAC-OS region, and a single crystal structure region. Good. For example, the mixed film may have a single-layer structure or a stacked structure including any two or more of the above-described regions.

<Configuration of CAC-OS>
A structure of a CAC (Cloud Aligned Composite) -OS that can be used for the transistor disclosed in one embodiment of the present invention is described below.

  In this specification and the like, a metal oxide is a metal oxide in a broad expression. Metal oxides are classified into oxide insulators, oxide conductors (including transparent oxide conductors), oxide semiconductors (also referred to as oxide semiconductors or simply OS), and the like. For example, when a metal oxide is used for an active layer of a transistor, the metal oxide may be referred to as an oxide semiconductor. That is, in the case of describing as an OS FET, it can be said to be a transistor including a metal oxide or an oxide semiconductor.

  In this specification, in a case where a region having a function of a conductor is mixed with a region having a function of a dielectric in the metal oxide and the metal oxide as a whole functions as a semiconductor, a CAC (Cloud Aligned Composite) -OS (Oxide Semiconductor) or CAC-metal oxide.

  The CAC-OS is one structure of a material in which elements forming a metal oxide are unevenly distributed with a size of 0.5 nm to 10 nm, preferably 1 nm to 2 nm, or the vicinity thereof. In the following, in the metal oxide, one or more metal elements are unevenly distributed, and the region having the metal element has a size of 0.5 nm to 10 nm, preferably 1 nm to 2 nm, or the vicinity thereof. The state mixed with is also referred to as a mosaic or patch.

  The physical characteristics of a region where a specific element is unevenly distributed are determined by the properties of the element. For example, a region in which elements that tend to become insulators are relatively uneven among the elements constituting the metal oxide is a dielectric region. On the other hand, a region in which elements that tend to be conductors are relatively uneven among the elements constituting the metal oxide is a conductor region. In addition, when the conductor region and the dielectric region are mixed in a mosaic, the material functions as a semiconductor.

  Note that the metal oxide preferably contains indium. At this time, it is preferable that indium and zinc are included. In addition to them, element M (M is gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium. , One or more selected from tantalum, tungsten, or magnesium). Alternatively, the metal oxide may not include indium but may include zinc or zinc and M.

For example, a CAC-OS in In-Ga-Zn oxide (In-Ga-Zn oxide among CAC-OSs may be referred to as CAC-IGZO in particular) is an indium oxide (hereinafter referred to as InO). _X1 (X1 is greater real than 0) and.), or indium zinc oxide _{(hereinafter, in X2 Zn Y2 O Z2 (} X2, Y2, and Z2 is larger real than 0) and a.), gallium An oxide (hereinafter referred to as GaO _X3 (X3 is a real number greater than 0)) or a gallium zinc oxide (hereinafter referred to as Ga _X4 Zn _Y4 O _Z4 (where X4, Y4, and Z4 are greater than 0)) to.) and the like, the material becomes mosaic by separate into, mosaic _{InO X1} or _in X2 _Zn Y2 _{O Z2,} is a configuration in which uniformly distributed in the film (hereinafter Also referred to as a cloud-like.) A.

That, CAC-OS includes a region _{GaO X3} is the main _component, and In _{X2 Zn} Y2 _{O Z2,} or _{InO X1} is the main component region is a composite metal oxide having a structure that is mixed. Note that in this specification, for example, the first region indicates that the atomic ratio of In to the element M in the first region is larger than the atomic ratio of In to the element M in the second region. It is assumed that the concentration of In is higher than that in the second region.

Note that IGZO is a common name and may refer to one compound of In, Ga, Zn, and O. As a typical example, 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) A crystalline compound may be mentioned.

  The crystalline compound has a single crystal structure, a polycrystalline structure, or a CAAC structure. The CAAC structure is a crystal structure in which a plurality of IGZO nanocrystals have c-axis orientation and are connected without being oriented in the ab plane.

  On the other hand, CAC-OS relates to a material structure of a metal oxide. CAC-OS refers to a region observed in the form of nanoparticles mainly composed of Ga in a material structure including In, Ga, Zn and O, and nanoparticles mainly composed of In. The region observed in a shape is a configuration in which the regions are randomly dispersed in a mosaic shape. Therefore, in the CAC-OS, the crystal structure is a secondary element.

  Note that the CAC-OS does not include a stacked structure of two or more kinds of films having different compositions. For example, a structure composed of two layers of a film mainly containing In and a film mainly containing Ga is not included.

Incidentally, a region _{GaO X3} is the main _component, and In _{X2 Zn} Y2 _{O Z2} or _{InO X1} is the main component region, in some cases clear boundary can not be observed.

  In place of gallium, aluminum, yttrium, copper, vanadium, beryllium, boron, silicon, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, or magnesium are selected. In the case where one or a plurality of types are included, the CAC-OS includes a region that is observed in a part of a nanoparticle mainly including the metal element and a nanoparticle mainly including In. The region observed in the form of particles refers to a configuration in which each region is randomly dispersed in a mosaic shape.

  The CAC-OS can be formed by a sputtering method under a condition where the substrate is not intentionally heated, for example. In the case where a CAC-OS is formed by a sputtering method, any one or more selected from an inert gas (typically argon), an oxygen gas, and a nitrogen gas may be used as a deposition gas. Good. Further, the flow rate ratio of the oxygen gas to the total flow rate of the deposition gas during film formation is preferably as low as possible. For example, the flow rate ratio of the oxygen gas is 0% to less than 30%, preferably 0% to 10%. .

  The CAC-OS is characterized in that no clear peak is observed when it is measured using a θ / 2θ scan by the out-of-plane method, which is one of the X-ray diffraction (XRD) measurement methods. Have. That is, it can be seen from X-ray diffraction that no orientation in the ab plane direction and c-axis direction of the measurement region is observed.

  In addition, in the CAC-OS, in an electron beam diffraction pattern obtained by irradiating an electron beam with a probe diameter of 1 nm (also referred to as a nanobeam electron beam), a ring-shaped high luminance region and a plurality of regions in the ring region are provided. A bright spot is observed. Therefore, it can be seen from the electron beam diffraction pattern that the crystal structure of the CAC-OS has an nc (nano-crystal) structure having no orientation in the planar direction and the cross-sectional direction.

In addition, for example, in a CAC-OS in an In—Ga—Zn oxide, GaO _X3 is a main component by EDX mapping obtained by using energy dispersive X-ray spectroscopy (EDX: Energy Dispersive X-ray spectroscopy). It can be confirmed that the region and the region mainly composed of In _X2 Zn _Y2 O _Z2 or InO _X1 are unevenly distributed and mixed.

The CAC-OS has a structure different from that of the IGZO compound in which the metal element is uniformly distributed, and has a property different from that of the IGZO compound. That is, in the CAC-OS, a region in which GaO _X3 or the like is a main component and a region in which In _X2 Zn _Y2 O _Z2 or InO _X1 is a main component are phase-separated from each other, and each region is mainly composed of each element. Has a mosaic structure.

Here, the region containing In _X2 Zn _Y2 O _Z2 or InO _X1 as a main component is a region having higher conductivity than a region containing GaO _X3 or the like as a main component. _That, In _{X2 Zn} Y2 _{O Z2} or _{InO X1,} is an area which is the main component, by carriers flow, expressed the conductivity of the oxide semiconductor. Therefore, a region where In _X2 Zn _Y2 O _Z2 or InO _X1 is a main component is distributed in a cloud shape in the metal oxide, so that high field-effect mobility (μ) can be realized.

On the other hand, areas such as _{GaO X3} is the main _component, as compared to the In _{X2 Zn} Y2 _{O Z2} or _{InO X1} is the main component area, it is highly regions insulating. That is, since the region mainly composed of GaO _X3 or the like is distributed in the metal oxide, a leakage current can be suppressed and a good switching operation can be realized.

Therefore, when CAC-OS is used for a semiconductor element, the insulating property caused by GaO _{X3 and the} like and the conductivity caused by In _X2 Zn _Y2 O _Z2 or InO _X1 act complementarily, thereby increasing the An on-current (I _on ) and high field effect mobility (μ) can be realized.

  In addition, a semiconductor element using a CAC-OS has high reliability. Therefore, the CAC-OS is optimal for various semiconductor devices including a display.

  Alternatively, silicon may be used for the semiconductor in which the channel of the transistor is formed. Although amorphous silicon may be used as silicon, it is particularly preferable to use silicon having crystallinity. For example, microcrystalline silicon, polycrystalline silicon, single crystal silicon, or the like is preferably used. In particular, polycrystalline silicon can be formed at a lower temperature than single crystal silicon, and has higher field effect mobility and higher reliability than amorphous silicon.

  The bottom-gate transistor described in this embodiment is preferable because the number of manufacturing steps can be reduced. At this time, since amorphous silicon can be used at a lower temperature than polycrystalline silicon, it is possible to use a material having low heat resistance as the electrode material and substrate material for the wiring below the semiconductor layer. Can widen the choice of materials. For example, a glass substrate having an extremely large area can be suitably used. On the other hand, a top-gate transistor is preferable because an impurity region can be easily formed in a self-aligning manner and variation in characteristics can be reduced. At this time, it is particularly suitable when polycrystalline silicon, single crystal silicon or the like is used.

[Insulating film]
The insulating film included in the blue 1 transistor 111 and the second transistor 112 or the insulating film in the vicinity of the first transistor 111 and the second transistor 112 can be formed using a sputtering method, a CVD method, or the like as appropriate. . As the material for the insulating film, a silicon oxide film, a gallium oxide film, a gallium zinc oxide film, a zinc oxide film, an aluminum oxide film, a silicon nitride film, a silicon oxynitride film, an aluminum oxynitride film, or a silicon nitride oxide film is used. Can be formed. Further, as a material of the gate insulating film, hafnium oxide, yttrium oxide, hafnium silicate (HfSi _x O _y (x> 0, y> 0)), hafnium silicate to which nitrogen is added (HfSiO _x N _y (x> 0, y) > 0)), hafnium aluminate (HfAl _x O _y (x> 0, y> 0)), and high-k materials such as lanthanum oxide can be used to reduce gate leakage current. Further, the gate insulating film 438 may have a single-layer structure or a stacked structure.

  Further, as the material of the insulating film, an organic material that functions as a planarization insulating film may be used. As the material, an organic material such as a polyimide resin or an acrylic resin can be used by a wet process such as spin coating or a printing method. In addition to the organic material, a low dielectric constant material (low-k material) or the like can be used. Note that the planarization insulating film may be formed by stacking a plurality of insulating films formed using these materials.

[Polarizer]
As the polarizing plates 120 and 132, for example, circular polarizing plates may be used. Although not shown in the drawings, an optical member such as a reflection plate or a diffusion plate may be provided in the vicinity of the polarizing plates 120 and 132. In addition, an antireflection film, a polarizing film, a retardation film, a light diffusing film, a condensing film, or other functional film, an antistatic film that suppresses the adhesion of dirt, and dirt are less likely to adhere to the polarizing plates 120 and 132 A functional film including a water-repellent film and a hard coat film that suppresses generation of scratches associated with use may be provided.

  Note that by providing the polarizing plate 132, reflection from external light can be suppressed and a display device with high visibility can be obtained.

[Light emission device]
The light emitting device 122 can be used as a light source. As the light source, a cold cathode tube such as a backlight or a sidelight or a white diode can be used.

[Colored layer]
The colored layer 140 is formed of a material that transmits only the colored light in order to function as a color filter. As the color element, red, green, blue, or the like can be used. Further, cyan, magenta, yellow (yellow), or the like may be used. The phrase “transmitting only colored light” means that the light transmitted through the colored layer has a peak at the wavelength of the chromatic light.

[Structure]
The first structure body 124 and the second structure body 126 include a material that transmits at least light. In addition, a reflective material may be used for the reflective film 124 </ b> R included in the first structure body 124. Note that the second structure body 126 may also be provided with a reflective film.

[Light extraction part]
As the light extraction portion 122R, a minute lens-like structure such as a microlens can be used. A material that transmits visible light can be used for the light extraction portion 122R. Alternatively, a material having a refractive index of 1.3 to 2.5 can be used for the light extraction portion 122R. For example, an inorganic material or an organic material can be preferably used.

  Specifically, the light extraction portion 122R includes cerium oxide, hafnium oxide, lanthanum oxide, magnesium oxide, niobium oxide, tantalum oxide, titanium oxide, yttrium oxide, zinc oxide, an oxide containing indium and tin, or indium and gallium. An oxide containing zinc and zinc can be used. Alternatively, zinc sulfide or the like may be used.

  Alternatively, a material including a resin can be used for the light extraction portion 122R. Specifically, a resin into which chlorine, bromine or iodine is introduced, a resin into which heavy metal atoms are introduced, a resin into which an aromatic ring is introduced, a resin into which sulfur is introduced, or the like can be used. Alternatively, a resin including a resin and nanoparticles of a material having a higher refractive index than the resin can be used. Titanium oxide or zirconium oxide can be used for the nanoparticles.

  This embodiment can be implemented in appropriate combination with at least part of the other embodiments described in this specification.

(Embodiment 2)
Hereinafter, structural examples of the display device of one embodiment of the present invention will be described.

[Configuration example of display device]
FIG. 7A shows a block diagram of the display device 10. The display device 10 includes a display unit 14.

  The display unit 14 includes a plurality of pixel units 30 arranged in a matrix. The pixel unit 30 includes a first pixel 31p and a second pixel 32p.

  In FIG. 7A, the first pixel 31p has a display element corresponding to white (W), and the second pixel 32p has three colors of red (R), green (G), and blue (B). An example in the case of having a corresponding display element is shown.

  The first pixel 31p includes a display element 31W corresponding to white (W). The display element 31W is a display element that utilizes reflection of external light.

  The second pixel 32p includes a display element 32R corresponding to red (R), a display element 32G corresponding to green (G), and a display element 32B corresponding to blue (B). The display elements 32R, 32G, and 32B are display elements that transmit light from the light source.

[Configuration example of pixel unit]
FIG. 7B is a schematic diagram illustrating a configuration example of the pixel unit 30.

  The first pixel 31p has a display element 31W. The display element 31W is an element that reflects and displays external light. The display element 31W reflects external light and emits white light Wr to the display surface side.

  The second pixel 32p includes a display element 32R, a display element 32G, and a display element 32B. The display element 32R, the display element 32G, and the display element 32B are elements that transmit visible light. The display element 32R emits red light Rt to the display surface side. Similarly, the display element 32G and the display element 32B respectively emit green light Gt or blue light Bt to the display surface side.

  Subsequently, a display mode by the pixel unit 30 will be described with reference to FIGS.

  FIG. 8A corresponds to a mode (first mode) in which display is performed using only reflected light by driving the first pixel 31p. For example, when the illuminance of external light is sufficiently high, the pixel unit 30 does not drive the second pixel 32p, and uses only the light from the first pixel 31p to generate the light 35r that is reflected light. It can be emitted to the display surface side. Thereby, driving with extremely low power consumption can be performed. In addition, display that is kind to the eyes can be performed.

  FIG. 8B corresponds to a mode (second mode) in which display is performed using only transmitted light by driving the second pixels 32p. For example, when the illuminance of outside light is extremely small, the pixel unit 30 does not drive the first pixel 31p, and only mixes light (light Rt, light Gt, and light Bt) from the second pixel 32p. By doing so, light 35t of a predetermined color can be emitted to the display surface side. Thereby, a vivid display can be performed. Further, by reducing the luminance when the illuminance of outside light is small, it is possible to suppress glare that the user feels and to reduce power consumption.

  FIG. 8C corresponds to a mode (third mode) in which display is performed by driving both the first pixel 31p and the second pixel 32p within the same period. The pixel unit 30 emits light 35tr of a predetermined color in which reflected light and transmitted light are mixed to the display surface side by mixing the light Wr, the light Rt, the light Gt, and the light Bt. be able to.

[Modification]
In the above example, the first pixel 31p has a display element corresponding to white, and the second pixel 32p has a display element corresponding to three colors of red (R), green (G), and blue (B). However, the present invention is not limited to this. Below, the example of a structure different from the above is shown.

  9A and 9B illustrate an example in which the first pixel 31p includes display elements corresponding to three colors of red (R), green (G), and blue (B). ing.

  The first pixel 31p includes a display element 31R, a display element 31G, and a display element 31B. The display element 31R, the display element 31G, and the display element 31B are elements that reflect and display external light. The display element 31R reflects external light and emits red light Rr to the display surface side. Similarly, the display element 31G and the display element 31B respectively emit green light Gr or blue light Br to the display surface side.

  FIG. 9B corresponds to a mode (third mode) in which display is performed by driving both the first pixel 31p and the second pixel 32p. The pixel unit 30 displays light 35tr of a predetermined color in which reflected light and transmitted light are mixed by mixing the six lights of light Rr, light Gr, light Br, light Rt, light Gt, and light Bt. Can be injected to the surface side.

  At this time, there are many combinations of the brightness of each of the six lights, light Rr, light Gr, light Br, light Rt, light Gt, and light Bt, so that the light 35tr becomes light of a predetermined brightness and chromaticity. To do. Therefore, among the combinations of the luminance (gradation) of each of the six lights that realize the light 35tr having the same luminance and chromaticity, the luminance (gradation) of the light Rr, the light Gr, and the light Br emitted from the first pixel 31p. It is preferable to select a combination that yields the largest value. Thereby, power consumption can be reduced without sacrificing color reproducibility.

  This embodiment can be implemented in appropriate combination with at least part of the other embodiments described in this specification.

(Embodiment 3)
Examples of display panels that can be used for the display portion of the display device of one embodiment of the present invention are described below. The display panel exemplified below is a display panel that includes both a reflective liquid crystal element and a transmissive liquid crystal element, and can display in both a transmissive mode and a reflective mode.

[Configuration example]
FIG. 10A is a block diagram illustrating an example of a structure of the display device 800. The display device 800 includes a plurality of pixels 810 arranged in a matrix in the display portion 801. The display device 800 includes a circuit GD and a circuit SD. In addition, a plurality of pixels 810 arranged in the direction R, and a plurality of wirings G1, a plurality of wirings G2, a plurality of wirings ANO, and a plurality of wirings CSCOM electrically connected to the circuit GD are provided. In addition, a plurality of pixels 810 arranged in the direction C and a plurality of wirings S1 and a plurality of wirings S2 electrically connected to the circuit SD are provided.

  Note that, here, for the sake of simplicity, a configuration including one circuit GD and one circuit SD is shown; however, the circuit GD and the circuit SD that drive the liquid crystal element and the circuit GD and the circuit SD that drive the light emitting element are separately provided. May be provided.

  The pixel 810 includes a reflective liquid crystal element and a transmissive liquid crystal element.

  FIG. 10B1 illustrates a configuration example of the electrode 861 included in the pixel 810. The electrode 861 functions as a reflective electrode of a reflective liquid crystal element in the pixel 810. The electrode 861 is provided with an opening 851.

  In FIG. 10B1, a transmissive liquid crystal element 860 positioned in a region overlapping with the electrode 861 is illustrated by a broken line. The transmissive liquid crystal element 860 is disposed so as to overlap with the opening 851 of the electrode 861. Accordingly, light transmitted through the transmissive liquid crystal element 860 is emitted to the display surface side through the opening 851.

  FIG. 10B1 illustrates two pixels 810 arranged in the direction C. One electrode 861 has one opening 851. At this time, the transmissive liquid crystal element 860 is driven by a time gray scale method to emit light such as red (R), green (G), and blue (B) dispersed in time through the opening 851. Can be injected.

  FIG. 10B2 illustrates an example in which one electrode 861 includes three openings 851. At this time, a transmissive liquid crystal element 860 that transmits different colors is stacked in each opening 851. Thereby, light of different colors is emitted from the transmissive liquid crystal elements 860 to the display surface side through the three openings 851.

  If the ratio of the total area of the opening 851 to the total area of the non-opening is too large, the display using the reflective liquid crystal element becomes dark. In addition, if the ratio of the total area of the opening 851 to the total area of the non-opening is too small, the display using the transmissive liquid crystal element 860 becomes dark.

  In addition, when the area of the opening 851 provided in the electrode 861 functioning as the reflective electrode is too small, the efficiency of light that can be extracted from the light emitted from the transmissive liquid crystal element 860 is reduced.

  The shape of the opening 851 can be, for example, a polygon, a rectangle, an ellipse, a circle, a cross, or the like. Moreover, it is good also as an elongated streak shape, a slit shape, and a checkered shape. Further, the opening 851 may be arranged close to adjacent pixels.

[Circuit configuration example]
FIG. 11 is a circuit diagram illustrating a configuration example of the pixel 810. In FIG. 11, two adjacent pixels 810 are shown.

  The pixel 810 includes a switch SW1, a capacitor C1, a liquid crystal element 840, a switch SW2, a switch SW2, a capacitor C2, a liquid crystal element 860, and the like. In addition, the pixel 810 is electrically connected to a wiring G1, a wiring G2, a wiring CSCOM, a wiring S1, and a wiring S2. In FIG. 11, a wiring VCOM1 electrically connected to the liquid crystal element 840 and a wiring VCOM2 electrically connected to the liquid crystal element 860 are illustrated.

  FIG. 11 shows an example in which transistors are used for the switch SW1 and the switch SW2.

  The switch SW1 has a gate connected to the wiring G1, one of a source and a drain connected to the wiring S1, and the other of the source and the drain connected to one electrode of the capacitor C1 and one electrode of the liquid crystal element 840. Yes. The other electrode of the capacitor C1 is connected to the wiring CSCOM. The other electrode of the liquid crystal element 840 is connected to the wiring VCOM1.

  The switch SW2 has a gate connected to the wiring G2, a source or drain connected to the wiring S2, and the other source or drain connected to one electrode of the capacitor C2 and one electrode of the liquid crystal element 860. Yes. The other electrode of the capacitor C2 is connected to the wiring CSCOM. The other electrode of the liquid crystal element 860 is connected to the wiring VCOM2.

  A signal for controlling the switch SW1 to be in a conductive state or a non-conductive state can be supplied to the wiring G1. A predetermined potential can be applied to the wiring VCOM1. A signal for controlling the alignment state of the liquid crystal included in the liquid crystal element 840 can be supplied to the wiring S1. A predetermined potential can be applied to the wiring CSCOM.

  A signal for controlling the switch SW2 to be in a conductive state or a non-conductive state can be supplied to the wiring G2. A predetermined potential can be applied to the wiring VCOM2. A signal for controlling the alignment state of the liquid crystal included in the liquid crystal element 860 can be supplied to the wiring S2.

  For example, in the case of performing reflection mode display, the pixel 810 illustrated in FIG. 11 can be driven by a signal supplied to the wiring G1 and the wiring S1 and can display using optical modulation by the liquid crystal element 840. Further, in the case where display is performed in the transmissive mode, display can be performed using a signal supplied to the wiring G2 and the wiring S2 and using optical modulation by the liquid crystal element 860. In the case of driving in both modes, the driving can be performed by signals given to the wiring G1, the wiring G2, the wiring S1, and the wiring S2.

  Note that FIG. 11 illustrates an example in which one pixel 810 includes one liquid crystal element 840 and one liquid crystal element 860. By driving the liquid crystal element 860 by a time gray scale method, a full color display is possible with one pixel 810 when displaying in the transmissive mode or both modes.

  12 illustrates an example in which one pixel 810 includes one reflective liquid crystal element 840 and three transmissive liquid crystal elements (a liquid crystal element 860r, a liquid crystal element 860g, and a liquid crystal element 860b). The liquid crystal element 860r, the liquid crystal element 860g, and the liquid crystal element 860b are transmissive liquid crystal elements that transmit red (R), green (G), and blue (B) light, respectively. The pixel 810 shown in FIG. 12 can perform full color display with three transmissive liquid crystal elements when displaying in the transmissive mode or both modes.

  This embodiment can be implemented in appropriate combination with at least part of the other embodiments described in this specification.

(Embodiment 4)
A pixel driving method that can be used for the display device of one embodiment of the present invention is described below.

  In the driving method exemplified below, the backlight is a light emitting element that emits a red (R) color, a light emitting element that produces a green (G) color, or an LED of a light emitting element that produces a blue (B) color. The full color display is performed by switching the color of light emitted from each LED to a different color for each unit period (also referred to as a field sequential method). This driving method is a full-color display method different from a method of performing full-color display using a white LED and a color filter provided in a liquid crystal display device. In particular, a field sequential method that can suppress the color breakup phenomenon and improve the image quality of the display image will be described below.

The backlight includes red (R), green (G), and blue (B) LEDs, and includes a plurality of light emitting diode groups arranged in a plurality of rows.

In the field sequential driving method described in this embodiment, the input operation and the light emitting operation are repeated Z times (Z is a natural number of 3 or more).

In the input operation, different display selection signal pulses are sequentially input to the pixels in each row. For example, a plurality of display regions are divided into one or more rows of pixels and one or more rows of light emitting diode groups, and different display selection signal pulses are sequentially input to the pixels of each row in each of the plurality of display regions.

For example, in the case where the scan line driver circuit includes a shift register, a pulse of a start pulse signal is input to the shift register, and pulses are sequentially output from the plurality of pulse signals of the shift register. Further, by inputting the pulse of the start pulse signal again while the pulses are sequentially output in the plurality of pulse signals of the shift register, different display selection signal pulses are applied to the pixels in each row in the plurality of display areas. The sequential input operation can be repeated.

While the display selection signal pulse is input to the pixel, the display data signal is input to the pixel, and the pixel is in a writing state (also referred to as a state wt). Further, after the display selection signal pulse is input, the pixel is in a display state (also referred to as a state hld) corresponding to the input display data.

In the light emitting operation, each time a display selection signal pulse is input to one or more rows of pixels, one or more of a red light emitting diode, a green light emitting diode, and a blue light emitting diode are caused to emit light. For example, each time a display selection signal pulse is input to one or more rows of pixels, one of the red light emitting diodes, the green light emitting diodes, and the blue light emitting diodes of the light emitting diode groups in different rows in each of the plurality of display regions. One or a plurality of light emitting diodes that exhibit different colors in a plurality of display areas are caused to emit light. As a result, light from the light emitting diode group is sequentially irradiated onto the pixels to which the display selection signal pulse is input.

In addition, when the input operation and the light emission operation are repeated a plurality of times, the light emission operation of the Kth time (K is a natural number of 2 or more and Z or less) emits light emitting diodes that exhibit colors different from those of the K-1th light emission operation. Let For example, in the Kth light emitting operation, a light emitting diode that emits a color different from that in the K-1th light emitting operation in each of the plurality of display areas is caused to emit light.

FIG. 13 is a timing chart for explaining an example of a field sequential driving method described in this embodiment.

Here, a region composed of a plurality of pixels is divided into 15 pixels from the first group of pixels (also referred to as pixels PIX_G (1)) to the 15th group of pixels (also referred to as pixels PIX_G (15)) for each row. Divide into groups. Further, each group is divided into three groups every five. The first group of pixels (also referred to as pixels PIX_G (1)) to the fifth group of pixels (also referred to as pixels PIX_G (5)) divided in this manner are used as the first display area and the sixth group. Pixels (also referred to as pixels PIX_G (6)) to tenth group of pixels (also referred to as pixels PIX_G (10)) are referred to as the second display area, and pixels of the eleventh group (also referred to as pixels PIX_G (11)) to the tenth. Fifteen groups of pixels (also referred to as pixels PIX_G (15)) are defined as a third display region. Note that the number of rows of pixels in each group is not limited to five.

Further, the input operation and the light emission operation are repeated.

In the input operation, in each display region, the pixels in each group are sequentially set to the writing state (state wt) from the first group of pixels. At this time, in each group, the pixels are sequentially written from the first row of pixels to the display state (state hld) corresponding to the input display data. In addition, a light emitting diode group included in the backlight is appropriately turned off (also referred to as a state off) so that light is not emitted from the light emitting diode to a pixel in which a writing operation is performed.

Further, in the light emitting operation, in each of the first display area to the third display area, the red LED, the green LED, and Light is emitted from the backlight for each pixel of the group in which display data is input by emitting LEDs having different colors in each of the first display area to the third display area among one or a plurality of blue LEDs. Irradiate.

For example, as shown in FIG. 13, for each input operation, the LEDs in the light emitting diode groups in each row are caused to emit light in the order of red, green, and blue in the first display area, and blue, red, The light emitting operation may be performed by causing the LEDs in the light emitting diode groups in each row to emit light in the order of green, and causing the LEDs in the light emitting diode groups in each row to emit in the order of green, blue, and red in the third display region. Note that the color and order of the LEDs to be emitted are not limited thereto.

With the above structure, the data writing operation for the display data signal to the pixels is performed in parallel for each of the plurality of groups, so that the data writing time for all the pixels can be shortened. Therefore, it is easy to increase the number of times display data is written, and it is easy to reduce the color breakup phenomenon.

In addition, with the above structure, display data signal data can be written to the pixel circuits of another group while irradiating light to pixels of a certain group, so that the minimum required operation time is shortened. be able to. Therefore, it is easy to increase the number of times display data is written, and it is easy to reduce the color breakup phenomenon.

This embodiment can be implemented in appropriate combination with at least part of the other embodiments described in this specification.

(Embodiment 5)
In this embodiment, a display module using the display device according to one embodiment of the present invention will be described. A display module 8000 illustrated in FIG. 14A includes a display panel 8006, a frame 8009, a printed board 8010, and a battery 8011 which are connected to an FPC 8005 between an upper cover 8001 and a lower cover 8002.

For example, the display device according to one embodiment of the present invention can be used for the display panel 8006. Thereby, a display module with less fatigue and good comfort can be manufactured.

The shapes and dimensions of the upper cover 8001 and the lower cover 8002 can be changed as appropriate in accordance with the size of the display panel 8006.

Further, a touch sensor may be provided over the display panel 8006. As the touch sensor, a resistive touch sensor or a capacitive touch sensor can be used so as to overlap with the display panel 8006. In addition, it is possible to provide the display panel 8006 with a touch sensor function without providing a touch sensor.

The frame 8009 has a function as an electromagnetic shield for blocking electromagnetic waves generated by the operation of the printed board 8010 in addition to a protective function of the display panel 8006. The frame 8009 may have a function as a heat sink.

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

The display module 8000 may be additionally provided with a member such as a polarizing plate, a retardation plate, or a prism sheet.

FIG. 14B is a schematic cross-sectional view of a display module 8000 including an optical touch sensor.

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

The display panel 8006 is provided so as to overlap the printed board 8010 and the battery 8011 with a frame 8009 interposed therebetween. The display panel 8006 and the frame 8009 are fixed to the light guide unit 8017a and the light guide unit 8017b.

Light 8018 emitted from the light emitting unit 8015 passes through the upper part of the display panel 8006 by the light guide unit 8017a and reaches the light receiving unit 8016 through the light guide unit 8017b. For example, the light 8018 is blocked by a detection object such as a finger or a stylus, whereby a touch operation can be detected.

For example, a plurality of light emitting units 8015 are provided along two adjacent sides of the display panel 8006. A plurality of light receiving portions 8016 are provided at positions facing the light emitting portion 8015 with the display panel 8006 interposed therebetween. Thereby, the information on the position where the touch operation is performed can be acquired.

The light emitting unit 8015 can use a light source such as an LED element. In particular, as the light emitting unit 8015, it is preferable to use a light source that emits infrared rays that are not visually recognized by the user and are harmless to the user.

The light receiving unit 8016 can be a photoelectric element that receives light emitted from the light emitting unit 8015 and converts the light into an electrical signal. Preferably, a photodiode capable of receiving infrared light can be used.

As the light guide portion 8017a and the light guide portion 8017b, a member that transmits at least 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 arranged below the display panel 8006, and external light reaches the light receiving portion 8016 and the touch sensor malfunctions. Can be suppressed. In particular, it is preferable to use a resin that absorbs visible light and transmits infrared rays. Thereby, malfunction of a touch sensor can be controlled more effectively.

This embodiment can be implemented in appropriate combination with at least part of the other embodiments described in this specification.

(Embodiment 6)
In this embodiment, examples of electronic devices using the display device and the like disclosed in this specification and the like will be described.

As an electronic device using a semiconductor device according to one embodiment of the present invention, a display device such as a television or a monitor, a lighting device, a desktop or laptop personal computer, a word processor, or a DVD (Digital Versatile Disc) is stored in a recording medium Playback device for playing back still images or moving images, portable CD player, radio, tape recorder, headphone stereo, stereo, table clock, wall clock, cordless telephone cordless handset, transceiver, car phone, mobile phone, personal digital assistant, tablet High-frequency heating of fixed terminals such as portable terminals, portable game machines, pachinko machines, calculators, electronic notebooks, electronic book terminals, electronic translators, voice input devices, video cameras, digital still cameras, electric shavers, microwave ovens, etc. Equipment, electric rice cooker, electric Air washing machine, electric vacuum cleaner, water heater, electric fan, hair dryer, air conditioner, humidifier, dehumidifier, etc., dishwasher, dish dryer, clothes dryer, futon dryer, electric refrigerator, electric freezer , Electric refrigerator-freezers, DNA storage freezers, flashlights, tools such as chainsaws, medical devices such as smoke detectors and dialysis machines. Further examples include industrial equipment such as guide lights, traffic lights, belt conveyors, elevators, escalators, industrial robots, power storage systems, power storage devices for power leveling and smart grids. In addition, an engine using fuel, a moving body driven by an electric motor using electric power from a power storage body, and the like may be included in the category of electronic devices. Examples of the moving body include an electric vehicle (EV), a hybrid vehicle (HEV) having both an internal combustion engine and an electric motor, a plug-in hybrid vehicle (PHEV), a tracked vehicle in which these tire wheels are changed to an endless track, and electric assist. Examples include motorbikes including bicycles, motorcycles, electric wheelchairs, golf carts, small or large ships, submarines, helicopters, aircraft, rockets, artificial satellites, space probes, planetary probes, and space ships.

A portable game machine 2900 illustrated in FIG. 15A includes a housing 2901, a housing 2902, a display portion 2903, a display portion 2904, a microphone 2905, a speaker 2906, an operation switch 2907, and the like. In addition, the portable game machine 2900 includes an antenna, a battery, and the like inside the housing 2901. Note that although the portable game machine illustrated in FIG. 15A includes two display portions 2903 and 2904, the number of display portions is not limited thereto. The display portion 2903 is provided with a touch screen as an input device and can be operated with a stylus 2908 or the like.

An information terminal 2910 illustrated in FIG. 15B includes a housing 2911 including a display portion 2912, a microphone 2917, a speaker portion 2914, a camera 2913, an external connection portion 2916, an operation switch 2915, and the like. The display portion 2912 includes a display panel using a flexible substrate and a touch screen. In addition, the information terminal 2910 includes an antenna, a battery, and the like inside the housing 2911. The information terminal 2910 can be used as, for example, a smartphone, a mobile phone, a tablet information terminal, a tablet personal computer, an electronic book terminal, or the like.

A laptop personal computer 2920 illustrated in FIG. 15C includes a housing 2921, a display portion 2922, a keyboard 2923, a pointing device 2924, and the like. The laptop personal computer 2920 includes an antenna, a battery, and the like inside the housing 2921.

A video camera 2940 illustrated in FIG. 15D includes a housing 2941, a housing 2942, a display portion 2944, operation switches 2944, a lens 2945, a connection portion 2946, and the like. The operation switch 2944 and the lens 2945 are provided on the housing 2941, and the display portion 2944 is provided on the housing 2942. In addition, the video camera 2940 includes an antenna, a battery, and the like inside the housing 2941. The housing 2941 and the housing 2942 are connected to each other by a connection portion 2946. The angle between the housing 2941 and the housing 2942 can be changed by the connection portion 2946. Depending on the angle of the housing 2942 with respect to the housing 2941, the orientation of the image displayed on the display portion 2943 can be changed, and display / non-display of the image can be switched.

FIG. 15E illustrates an example of a bangle information terminal. The information terminal 2950 includes a housing 2951, a display portion 2952, and the like. In addition, an antenna, a battery, and the like are provided inside the information terminal 2950 and the housing 2951. The display portion 2952 is supported by a housing 2951 having a curved surface. Since the display portion 2952 includes a display panel using a flexible substrate, an information terminal 2950 that is flexible, light, and easy to use can be provided.

FIG. 15F illustrates an example of a wristwatch type information terminal. The information terminal 2960 includes a housing 2961, a display portion 2962, a band 2963, a buckle 2964, an operation switch 2965, an input / output terminal 2966, and the like. Further, an antenna, a battery, and the like are provided inside the information terminal 2960 and the housing 2961. The information terminal 2960 can execute various applications such as mobile phone, e-mail, text browsing and creation, music playback, Internet communication, and computer games.

The display surface of the display portion 2962 is curved, and display can be performed along the curved display surface. The display portion 2962 includes a touch sensor and can be operated by touching the screen with a finger, a stylus, or the like. For example, an application can be started by touching an icon 2967 displayed on the display unit 2962. The operation switch 2965 can have various functions such as time setting, power on / off operation, wireless communication on / off operation, manner mode execution and release, and power saving mode execution and release. . For example, the function of the operation switch 2965 can be set by an operating system incorporated in the information terminal 2960.

In addition, the information terminal 2960 can execute short-range wireless communication that is a communication standard. For example, it is possible to talk hands-free by communicating with a headset capable of wireless communication. Further, the information terminal 2960 includes an input / output terminal 2966, and can directly exchange data with other information terminals. Charging can also be performed via the input / output terminal 2966. Note that the charging operation may be performed by wireless power feeding without using the input / output terminal 2966.

FIG. 15G illustrates a tablet personal computer, which includes a housing 5301, a housing 5302, a display portion 5303, an optical sensor 5304, an optical sensor 5305, a switch 5306, and the like. The display portion 5303 is supported by a housing 5301 and a housing 5302. Since the display portion 5303 is formed using a flexible substrate, the display portion 5303 has a function of flexibly bending the shape. By changing the angle between the housing 5301 and the housing 5302 at the hinges 5307 and 5308, the display portion 5303 can be folded so that the housing 5301 and the housing 5302 overlap with each other. Although not shown, an open / close sensor may be incorporated, and the change in the angle may be used as information on the use condition in the display portion 5303.

FIG. 15H is a perspective view illustrating the television device 9100. A television device 9100 includes a housing 9000, a display portion 9001, a speaker 9003, operation keys 9005 (including a power switch or an operation switch), a connection terminal 9006, a sensor 9007 (a function of measuring distance, light, temperature, and the like). 1), a microphone 9008, and the like. The television device 9100 can incorporate a display device of, for example, 50 inches or more, or 100 inches or more into the display portion 9001.

The display device of one embodiment of the present invention is mounted on the display portion of the electronic device described in this embodiment. By using the display device and the driving method according to one embodiment of the present invention for the display portion of the electronic device, an electronic device with extremely low power consumption can be realized.

This embodiment can be implemented in appropriate combination with at least part of the other embodiments described in this specification.

DESCRIPTION OF SYMBOLS 10 Display apparatus 14 Display part 30 Pixel unit 31B Display element 31G Display element 31R Display element 31W Display element 31p Pixel 32R Display element 32B Display element 32G Display element 32p Pixel 35r Light 35t Light 35tr Light 100A Display apparatus 100B Display apparatus 100C Display apparatus 102 Substrate 104 Substrate 106 Liquid crystal element 106CE Electrode 106LC Liquid crystal layer 106PE Electrode 108 Liquid crystal element 108CE Electrode 108LC Liquid crystal layer 108PE Electrode 110 Element layer 111 Transistor 112 Transistor 114 Opening 116 Electrode 118 Opening 120 Polarizing plate 122 Light emitting device 122E Edge light 122G Conductive Optical plate 122R part 124 structure 124R reflection film 126 structure 128 diffusion film 130 input / output device 132 polarizing plate 134 insulating layer 136 colored layer 138 Edge layer 140 a colored layer 142 resin layer 501 display device 502 display device 503 opening 504 reflected light 505 transmitted light 506 pixel circuit 510 display unit 511 substrate 512 substrate 514 display unit 516 circuit 518 wiring 520 IC
522 FPC
524 Electrode 526 Opening 550 Liquid crystal element 570 Liquid crystal element 800 Display device 801 Display unit 810 Pixel 840 Liquid crystal element 851 Opening 860 Liquid crystal element 860b Liquid crystal element 860g Liquid crystal element 860r Liquid crystal element 861 Electrode 2900 Portable game machine 2901 Case 2902 Case 2903 Display unit 2904 Display unit 2905 Microphone 2906 Speaker 2907 Operation switch 2908 Stylus 2910 Information terminal 2911 Housing 2912 Display unit 2913 Camera unit 2914 Speaker unit 2915 Operation switch 2916 External connection unit 2917 Microphone 2920 Notebook personal computer 2921 Housing 2922 Display unit 2923 Keyboard 2924 Pointing device 2940 Video camera 2941 Housing 2942 Housing 2943 Display unit 2944 Operation Switch 2945 Lens 2946 Connection unit 2950 Information terminal 2951 Case 2952 Display unit 2960 Information terminal 2961 Case 2962 Display unit 2963 Band 2964 Operation switch 2966 Input / output terminal 2967 Icon 5301 Case 5302 Case 5303 Display unit 5304 Optical sensor 5305 Optical sensor 5306 Switch 5307 Hinge 8000 Display module 8001 Upper cover 8002 Lower cover 8005 FPC
8006 Display panel 8009 Frame 8010 Printed circuit board 8011 Battery 8015 Light emitting unit 8016 Light receiving unit 8017a Light guiding unit 8017b Light guiding unit 8018 Light 9000 Case 9001 Display unit 9003 Speaker 9005 Operation key 9006 Connection terminal 9007 Sensor 9008 Microphone 9100 Television apparatus

Claims (13)

A first liquid crystal element, a second liquid crystal element, a first transistor, and a second transistor;
The first liquid crystal element has a function of reflecting visible light,
The second liquid crystal element has a function of transmitting visible light,
The first liquid crystal element is controlled by the first transistor, and the second liquid crystal element is controlled by the second transistor.
A display device characterized by that. A first liquid crystal element, a second liquid crystal element, a first transistor, and a second transistor;
The first liquid crystal element includes a first electrode, a second electrode, and a first liquid crystal layer,
The second liquid crystal element includes a third electrode, a fourth electrode, and a second liquid crystal layer,
One of the first electrode and the second electrode has a function of reflecting visible light, and the other of the first electrode and the second electrode has a function of transmitting visible light,
Both the third electrode and the fourth electrode have a function of transmitting visible light,
The first liquid crystal layer and the second liquid crystal layer each have an overlapping region,
The first liquid crystal element is controlled by the first transistor, and the second liquid crystal element is controlled by the second transistor.
A display device characterized by that. In claim 2,
One or both of the first transistor and the second transistor are
Having a metal oxide in the semiconductor layer,
A display device characterized by that. In claim 2 or claim 3,
The first transistor and the second transistor are disposed on the same plane.
A display device characterized by that. In any one of Claims 2 thru | or 4,
The specific resistance of the first liquid crystal layer has a region equal to or greater than the specific resistance of the second liquid crystal layer.
A display device characterized by that. In any one of Claims 2 thru | or 5,
The specific resistance of the first liquid crystal layer has a region of 1.0 × 10 ¹⁴ Ω · cm or more.
A display device characterized by that. A display device having a light emitting device, an input / output device, a first liquid crystal element, a second liquid crystal element, a first transistor, and a second transistor,
The first liquid crystal element has a function of reflecting visible light,
The second liquid crystal element has a function of transmitting visible light,
Between the light emitting device and the input / output device, the first liquid crystal element and the second liquid crystal device,
The second liquid crystal element is disposed on the light emitting part side,
The first liquid crystal element is disposed on the input / output side;
Either one or both of the first transistor and the second transistor is disposed between the first liquid crystal element and the second liquid crystal element,
The first liquid crystal element is controlled by the first transistor, and the second liquid crystal element is controlled by the second transistor.
A display device characterized by that. In claim 7,
A first structure is further provided between the first liquid crystal element and the second liquid crystal element,
The light emitted from the light emitting device is emitted to the first liquid crystal element side through the first structure.
A display device characterized by that. In claim 8,
On the first structure, further has a second structure that overlaps the first structure,
The light emitted from the light emitting device is emitted to the first liquid crystal element side through the first structure and the second structure.
A display device characterized by that. In claim 8 or claim 9,
The first structure has a reflective film;
A display device characterized by that. In any one of Claims 7 to 10,
The first transistor and the second transistor are each driven within the same period;
A display device characterized by that. In any one of Claims 7 to 11,
The first liquid crystal element is driven at a frame frequency of 0.1 Hz to less than 60 Hz;
A display device characterized by that. In any one of Claims 7 to 12,
The second liquid crystal element is driven by a time gray scale method in conjunction with the light emitting device.
A display device characterized by that.

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