Light-emitting device, display device, photoelectric conversion device, electronic apparatus, lighting device, and movable body

Abstract

To reduce the number of elements in a pixel circuit for providing a specific function.SOLUTION: A light-emitting device comprises a light-emitting element, a drive transistor and a switching transistor respectively arranged on a route through which current for causing the light-emitting element to emit light flows, a writing transistor arranged on a route connecting a signal line through which pixel signals are supplied and a gate of the drive transistor, and a capacitive transistor for maintaining the gate-source voltage of the drive transistor. A gate of the capacitive transistor is connected with the gate of the drive transistor. A source and a drain of the capacitive transistor are respectively connected with a source of the drive transistor. The capacitive transistor and the switching transistor are formed in the same impurity region. The conductivity type of the capacitive transistor is the same as the conductivity type of the drive transistor.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a light-emitting device, a display device, a photoelectric conversion device, an electronic device, a lighting device, and a moving body.

Background Art

[0002] Development of an active matrix type display device in which a driving transistor for controlling a current flowing through a light-emitting element is arranged in a pixel circuit has been carried out. The pixel circuit of the display device described in Patent Document 1 includes a capacitive element that connects the source and gate of the driving transistor, and another capacitive element that connects the source of the driving transistor and a power line. Patent Document 2 describes a technique for forming one of two capacitive elements in a semiconductor substrate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the display device described in Patent Document 1, one pixel circuit includes two capacitive elements. If a specific function provided by the pixel circuit can be realized with fewer elements, it can lead to a reduction in pixel size and cost. Some aspects of the present invention aim to reduce the number of elements in a pixel circuit for providing a specific function.

Means for Solving the Problems

[0005] According to one embodiment, there is provided a light-emitting device including a light-emitting element, a driving transistor and a switching transistor disposed on a path through which a current for causing the light-emitting element to emit light flows, a writing transistor disposed on a path connecting a signal line to which a pixel signal is supplied and a gate of the driving transistor, and a capacitive transistor for holding a gate-source voltage of the driving transistor. A gate of the capacitive transistor is connected to the gate of the driving transistor, each of a source and a drain of the capacitive transistor is connected to the source of the driving transistor, the capacitive transistor and the switching transistor are formed in the same impurity region, and a conductivity type of the capacitive transistor is the same as that of the driving transistor.

Advantages of the Invention

[0006] According to the above embodiment, the number of elements in a pixel circuit for providing a specific function can be reduced.

Brief Description of the Drawings

[0007]

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Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant descriptions are omitted.

[0009] <First Embodiment> Referring to FIG. 1, a configuration example of a light-emitting device 100 according to the first embodiment will be described. As will be described later, the light-emitting device 100 may be used in a display device. For example, the light-emitting device 100 may be used in a flat-panel (which may also be called a flat panel type) display device. The numerical values, shapes, materials, types of components, arrangement and connection forms of components, etc. used in the description of the embodiment are examples and do not limit the present invention.

[0010] The light-emitting device 100 may include a plurality of pixel circuits 101, a writing and scanning circuit 103, a signal output circuit 104, and a light-emitting scanning circuit 105. The plurality of pixel circuits 101 are arranged in a two-dimensional array (that is, so as to form a plurality of rows and a plurality of columns) in the pixel array section 102. Alternatively, the plurality of pixel circuits 101 may be arranged in a one-dimensional array. In the example of FIG. 1, the plurality of pixel circuits 101 are arranged in m rows and n columns (m and n are integers of 1 or more). The pixel circuit 101 may simply be called a pixel.

[0011] The writing and scanning circuit 103, the signal output circuit 104, and the light-emitting scanning circuit 105 are arranged around the pixel array section 102. The writing and scanning circuit 103, the signal output circuit 104, and the light-emitting scanning circuit 105 are an example of circuits constituting the driving section of the light-emitting device 100. The writing and scanning circuit 103 and the light-emitting scanning circuit 105 constitute a scanning drive system. The signal output circuit 104 constitutes a signal supply system. In the layout shown in FIG. 1, the writing and scanning circuit 103 is arranged on the left side of the pixel array section 102, and the light-emitting scanning circuit 105 is arranged on the right side of the pixel array section 102. Alternatively, other layouts may be used. For example, the writing and scanning circuit 103 and the light-emitting scanning circuit 105 may be opposite to the example of FIG. 1 with respect to the pixel array section 102, or the writing and scanning circuit 103 and the light-emitting scanning circuit 105 may be arranged on the same side with respect to the pixel array section 102. Also, a layout in which each of the writing and scanning circuit 103 and the light-emitting scanning circuit 105 is arranged in a pair on both the left and right sides of the pixel array section 102 may be used.

[0012] One pixel of the image displayed by the light-emitting device 100 may be displayed by one pixel circuit 101, or may be displayed by a plurality of pixel circuits 101. When one pixel of the image is displayed by a plurality of pixel circuits 101, this pixel may be represented as having a plurality of sub-pixels. Each of the plurality of sub-pixels may be displayed by one pixel circuit 101. For example, one pixel may be composed of three sub-pixels: a sub-pixel that emits red (R) light, a sub-pixel that emits green (G) light, and a sub-pixel that emits blue (B) light. Alternatively, one pixel may be composed of these three primary-color sub-pixels and one or more sub-pixels of other colors. The one or more sub-pixels of other colors may include a sub-pixel that emits white (W) light for improving luminance, or may include one or more sub-pixels that emit complementary-color light for expanding the color reproduction range.

[0013] In the pixel array unit 102, m write scanning lines 106-1 to 106-m and m emission scanning lines 108-1 to 108-m are arranged along a pixel row (that is, a row formed by a plurality of pixels arranged horizontally in FIG. 1). In the pixel array unit 102, n signal lines 107-1 to 107-n are arranged along a pixel column (that is, a column formed by a plurality of pixels arranged vertically in FIG. 1). In the following description, the m write scanning lines 106-1 to 106-m are collectively referred to as the write scanning line 106. The description of the write scanning line 106 may apply to any one of the one or more write scanning lines 106-1 to 106-m. The write scanning line 106 may represent any one of the one or more write scanning lines 106-1 to 106-m or a specific one determined by the context. The same applies to other components collectively referred to below. The m emission scanning lines 108-1 to 108-m are collectively referred to as the emission scanning line 108, and the n signal lines 107-1 to 107-n are collectively referred to as the signal line 107. One write scanning line 106 and one emission scanning line 108 may be arranged for one pixel row. One signal line 107 may be arranged for one pixel column.

[0014] The writing scan line 106 is connected to the corresponding output terminal among the m output terminals of the writing scan circuit 103. The light emission scan line 108 is connected to the corresponding output terminal among the m output terminals of the light emission scan circuit 105. The signal line 107 is connected to the corresponding output terminal among the n output terminals of the signal output circuit 104.

[0015] The signal output circuit 104 supplies the pixel signals SIG_1 to SIG_n to the n signal lines 107. In the following description, the n pixel signals SIG_1 to SIG_n are collectively referred to as the pixel signal SIG. The pixel signal SIG can take a signal potential Vsig corresponding to the luminance information supplied from a signal source (not shown). The signal potential Vsig output from the signal output circuit 104 is written to a plurality of pixel circuits 101 in row units via the signal line 107. Such writing may be called line sequential writing.

[0016] The writing scan circuit 103 is constituted by a shift register or the like that sequentially shifts start pulses in synchronization with a clock pulse. When writing the pixel signal SIG to each pixel circuit 101, the writing scan circuit 103 supplies the writing scan signals SEL_1 to SEL_m to the m writing scan lines 106, thereby sequentially scanning a plurality of pixel circuits 101 in row units. Such scanning may be called line sequential scanning. In the following description, the m writing scan signals SEL_1 to SEL_m are collectively referred to as the writing scan signal SEL. The pixel signal SIG may be called an image signal when an image is displayed by the light emitting device 100, or may be called a video signal when a video is displayed by the light emitting device 100.

[0017] The light emission scan circuit 105 is constituted by a shift register or the like that sequentially shifts start pulses in synchronization with a clock pulse. The light emission scan circuit 105 controls whether each pixel circuit 101 emits light or not by supplying the light emission scan signals SW_1 to SW_m to the m light emission scan lines 108 in synchronization with the line sequential scan by the writing scan circuit 103. In the following description, the m light emission scan signals SW_1 to SW_m are collectively referred to as the light emission scan signal SW.

[0018] Referring to FIG. 2, a configuration example of the pixel circuit 101 will be described. The pixel circuit 101 may include a light-emitting element 201, a driving transistor 202, a writing transistor 203, a switching transistor 204, and a capacitive transistor 205. The light-emitting element 201 may be a current-driven electro-optical element whose emission luminance changes according to the amount of current flowing through the light-emitting element 201. The light-emitting element 201 may be, for example, a light-emitting diode (LED) or an organic electroluminescence (EL) element. The driving transistor 202, the writing transistor 203, the switching transistor 204, and the capacitive transistor 205 constitute a driving circuit for driving the light-emitting element 201. The light-emitting element 201 may have an anode and a cathode. The cathode of the light-emitting element 201 is connected to the power supply line 207. The power supply line 207 is commonly arranged for a plurality of pixel circuits 101. A potential Vcath is supplied to the power supply line 207. All the transistors included in the pixel circuit 101 may be P-channel type transistors. Instead of this, some or all of the transistors included in the pixel circuit 101 may be N-channel type transistors.

[0019] The driving transistor 202 may be, for example, a P-channel type transistor. The conductivity type of the capacitive transistor 205 may be the same as the conductivity type of the driving transistor 202 (for example, both are P-channel type). The capacitive transistor 205 and the switching transistor 204 may be formed on the same semiconductor substrate. Further, the capacitive transistor 205 and the switching transistor 204 may be formed in the same N-type impurity region (for example, a well region) formed in a P-type semiconductor substrate. Instead of this, the capacitive transistor 205 and the switching transistor 204 may be formed in an N-type impurity region which is a part of an N-type semiconductor substrate.

[0020] The drive transistor 202 is a transistor for adjusting the amount of current flowing through the light-emitting element 201. The current flowing through the light-emitting element 201 may also be called the drive current. Since the light-emitting element 201 emits light when the drive current flows, the drive current is the current for causing the light-emitting element 201 to emit light. The drive transistor 202 is arranged on the path through which the drive current flows (in the example of FIG. 2, on the path from the power supply line 206 through the switching transistor 204, the drive transistor 202, and the light-emitting element 201 to the power supply line 207). In the example of FIG. 2, the drive transistor 202 is arranged on the path connecting the light-emitting element 201 and the switching transistor 204. The drive transistor 202 is connected in series with the light-emitting element 201. In the example of FIG. 2, one of the two main terminals of the drive transistor 202 (for example, the drain) is connected to the anode of the light-emitting element 201.

[0021] The write transistor 203 is a transistor for switching whether to write the pixel signal supplied from the signal output circuit 104 to the pixel circuit 101 through the signal line 107 to the gate of the drive transistor. The write transistor 203 is arranged on the path connecting the signal line 107 and the gate of the drive transistor 202. The gate of the write transistor 203 is connected to the write scan line 106. One of the two main terminals of the write transistor 203 (for example, the source) is connected to the signal line 107. The other of the two main terminals of the write transistor 203 (for example, the drain) is connected to the gate of the drive transistor 202. A write scan signal SEL is supplied to the gate of the write transistor 203 from the write scan circuit 103 through the write scan line 106.

[0022] The switching transistor 204 is a transistor for switching whether or not to cause the light-emitting element 201 to emit light. The switching transistor 204 is arranged on the path through which the drive current flows. In the example of FIG. 2, the switching transistor 204 is arranged on the path connecting the source of the drive transistor 202 and the power supply line 206. The gate of the switching transistor 204 is connected to the light-emitting scanning line 108. One of the two main terminals of the switching transistor 204 (for example, the source) is connected to the power supply line 206. A positive power supply potential PVDD is supplied to the power supply line 206. The power supply potential PVDD supplied to the power supply line 206 may be higher than the potential Vcath supplied to the power supply line 207. The other of the two main terminals of the switching transistor 204 (for example, the drain) is connected to the main terminal (for example, the source) of the two main terminals of the drive transistor 202 that is not connected to the light-emitting element 201. The back gate of the switching transistor 204 is connected to the power supply line 206. A light-emitting scanning signal SW is supplied from the light-emitting scanning circuit 105 to the gate of the switching transistor 204 through the light-emitting scanning line 108.

[0023] The capacitance transistor 205 is a transistor for holding the gate-source voltage of the drive transistor 202. The gate of the capacitance transistor 205 is connected to the gate of the drive transistor 202. Each of the two main terminals (for example, the source and the drain) of the capacitance transistor 205 is connected to the main terminal (for example, the source) of the two main terminals of the drive transistor 202 that is not connected to the light-emitting element 201. The back gate of the capacitance transistor 205 is connected to the power supply line 206. That is, the back gate of the capacitance transistor 205 and the source of the switching transistor 204 are connected to the same power supply line 206.

[0024] As described above, in the circuit configuration of FIG. 2, the gate of the drive transistor 202, one main terminal (for example, the drain) of the write transistor 203, and the gate of the capacitor transistor 205 are connected to the same node 208. One main terminal (for example, the source) of the drive transistor 202, one main terminal (for example, the drain) of the switching transistor 204, and each of the two main terminals (for example, the source and the drain) of the capacitor transistor 205 are connected to the same node 209.

[0025] Subsequently, with reference to FIG. 3, a configuration example of the capacitor transistor 205 will be described. FIG. 3 is a cross-sectional view of the capacitor transistor 205. The capacitor transistor 205 is formed in an N-type well region 301 formed in a P-type substrate 300. The well region 301 is a well-type impurity region used as a substrate conductive layer of a CMOS (Complementary Metal-Oxide-Semiconductor) transistor. P-type impurity regions 302 and 303 are formed in the well region 301. The impurity regions 302 and 303 may also be referred to as impurity diffusion regions or diffusion regions. A gate electrode 304 is formed so as to cover a portion between the impurity region 302 and the impurity region 303 in the well region 301. A gate insulating film (not shown) is formed between the gate electrode 304 and the well region 301. An element isolation portion 305 is formed outside the impurity regions 302 and 303.

[0026] The impurity region 302 functions as one of the two main terminals (for example, the source) of the capacitor transistor 205. The impurity region 303 functions as the other of the two main terminals (for example, the drain) of the capacitor transistor 205. The gate electrode 304 functions as the gate of the capacitor transistor 205. A power supply potential PVDD is supplied to the well region 301 from a power supply line 206 through a well contact (not shown).

[0027] A capacitor 306 is formed between the impurity region 302 and the gate electrode 304. A capacitor 307 is formed between the impurity region 303 and the gate electrode 304. A capacitor 308 is formed between the impurity region 302 and the well region 301. A capacitor 309 is formed between the impurity region 303 and the well region 301. Thus, a plurality of capacitors are formed by the capacitive transistor 205.

[0028] Referring to FIG. 4, an equivalent circuit of the pixel circuit 101 in FIG. 2 will be described. Since the impurity regions 302 and 303 function as two main terminals of the capacitive transistor 205, the impurity regions 302 and 303 are connected to the node 209. Since the gate electrode 304 functions as the gate of the capacitive transistor 205, the gate electrode 304 is connected to the node 208. Therefore, the capacitor 306 and the capacitor 307 are combined to form a capacitor 401 that connects the node 208 and the node 209 (i.e., connects the gate and the source of the driving transistor 202). Also, since the well region 301 functions as the back gate of the capacitive transistor 205, the well region 301 is connected to the power supply line 206. Therefore, the capacitor 308 and the capacitor 309 are combined to form a capacitor 402 that connects the power supply line 206 and the node 209. Thus, one capacitive transistor 205 functions as two capacitors 401 and 402.

[0029] The conductive state and the non-conductive state of the writing transistor 203 are switched according to the scanning signal SEL. When the writing transistor 203 is in the conductive state, the pixel signal SIG supplied from the signal output circuit 104 through the signal line 107 is supplied to the gate of the driving transistor 202, and this pixel signal SIG is held in the capacitor 401 of the capacitive transistor 205. The pixel signal SIG is set to take two values, the reference potential Vcal and the signal potential Vsig, within one horizontal period. The signal potential Vsig can be a value corresponding to the luminance information.

[0030] The conduction state and non-conduction state of the switching transistor 204 are switched according to the light-emitting scanning signal SW. When the switching transistor 204 is in the conduction state, current flows from the power supply line 206 to the driving transistor 202. As a result, the driving transistor 202 can cause the light-emitting element 201 to emit light. Specifically, the driving transistor 202 supplies a driving current corresponding to the signal potential Vsig held in the capacitance 401 of the capacitance transistor 205 to the light-emitting element 201. The light-emitting element 201 emits light due to this driving current. When the switching transistor 204 is in the non-conduction state, no current flows from the power supply line 206 to the driving transistor 202. Therefore, the driving transistor 202 cannot cause the light-emitting element 201 to emit light.

[0031] By the switching operation of the switching transistor 204, the light-emitting device 100 can control the ratio of the light-emitting period and the non-light-emitting period of the light-emitting element 201. Such control can be called duty control. By this duty control, since the afterimage associated with the pixel circuit 101 emitting light over one frame period can be reduced, the quality of the image (particularly, a moving image) displayed by the light-emitting device 100 is improved.

[0032] With reference to FIGS. 5 and 6, an operation example of the light-emitting device 100 will be described. The timing chart of FIG. 5 shows the waveforms of the write scanning signal SEL, the light-emitting scanning signal SW, and the pixel signal SIG, and the changes in the source potential Vs of the driving transistor 202 and the gate potential Vg of the driving transistor 202. The gate potential Vg is equal to the potential of the node 208. The source potential Vs is equal to the potential of the node 209. In FIG. 6, for simplicity, the write transistor 203 and the switching transistor 204 are shown by switch symbols. The write transistor 203 turns on (i.e., is in the conduction state) while the write scanning signal SEL is at the low level, and turns off (i.e., is in the non-conduction state) while the write scanning signal SEL is at the high level. The switching transistor 204 turns on while the light-emitting scanning signal SW is at the low level, and turns off while the light-emitting scanning signal SW is at the high level.

[0033] In the example of FIG. 5, one frame period ends at time t1, and the next frame period starts from time t1. One frame period includes a light emission period during which the light emitting element 201 emits light and a non-light emission period during which the light emitting element 201 does not emit light. The start of one frame period may be a non-light emission period. In the example of FIG. 5, the light emission period of one frame period ends at time t1. The lengths from time t1 to each of times t2 to t10 may be preset values.

[0034] Before time t1, since the light emission scanning signal SW is at a low level, the switching transistor 204 is on. Also, since the writing scanning signal SEL is at a high level, the writing transistor 203 is off. As a result, as indicated by arrow 601 in FIG. 6(a), a drive current Ids1 corresponding to the gate-source voltage Vgs of the drive transistor 202 is supplied from the power supply line 206 to the light emitting element 201 through the drive transistor 202. The light emitting element 201 emits light with a luminance corresponding to the current value of the drive current Ids1.

[0035] At time t1, the light emission scanning circuit 105 turns off the switching transistor 204 by switching the light emission scanning signal SW from a low level to a high level, as shown in FIG. 6(b). As a result, no current is supplied from the power supply line 206 to the light emitting element 201, and the light emitting element 201 turns off. When no current is supplied to the light emitting element 201, the anode potential of the light emitting element 201 converges to the sum of the threshold voltage Vthel of the light emitting element 201 and the cathode potential Vcath (i.e., Vthel + Vcath). At time t1, the writing transistor 203 and the switching transistor 204 remain off.

[0036] At time t2, the signal output circuit 104 switches the value of the pixel signal SIG to the reference potential Vcal. The period during which this reference potential Vcal is supplied becomes the horizontal period.

[0037] At time t3, the writing scan circuit 103 turns on the writing transistor 203 as shown in FIG. 6(c) by switching the writing scan signal SEL from a high level to a low level. As a result, as indicated by arrow 602, the reference potential Vcal supplied to the signal line 107 is written to the gate of the driving transistor 202 through the writing transistor 203.

[0038] At time t4, the emission scan circuit 105 turns on the switching transistor 204 as shown in FIG. 6(d) by switching the emission scan signal SW from a high level to a low level. As a result, the source potential Vs of the driving transistor 202 becomes equal to the power supply potential PVDD. As a result, the gate-source voltage Vgs (i.e., |Vcal - PVDD|) of the driving transistor 202 at this point in time is held in the capacitance 401 of the capacitance transistor 205.

[0039] At time t5, the emission scan circuit 105 turns off the switching transistor 204 as shown in FIG. 6(e) by switching the emission scan signal SW from a low level to a high level. As a result, as indicated by arrow 604, current flows from the capacitance transistor 205 through the driving transistor 202 to the light emitting element 201. As a result, as shown in FIG. 5, although the gate potential Vg of the driving transistor 202 is maintained at the reference potential Vcal, the source potential Vs of the driving transistor 202 decreases from the power supply potential PVDD. Thereby, the gate-source voltage Vgs of the driving transistor 202 becomes smaller and converges to the threshold voltage of the driving transistor 202 over time.

[0040] At time t6, the writing scan circuit 103 turns off the writing transistor 203 by switching the writing scan signal SEL from a low level to a high level. As a result, the gate-source voltage Vgs (i.e., the threshold voltage of the driving transistor 202) of the driving transistor 202 at this point in time is held in the capacitance 401 of the capacitance transistor 205.

[0041] The operation from time t5 to t6 may be called a threshold voltage correction operation because it is an operation for correcting the variation in the threshold voltage of the drive transistors 202 among the plurality of pixel circuits 101. Also, the operation from time t3 to t5 may be called a correction preparation operation because it is an operation for preparing for the threshold voltage correction operation. The period of the threshold voltage correction operation (i.e., the length from time t5 to t6) may be a length in which the gate-source voltage Vgs of the drive transistor 202 sufficiently converges to the threshold voltage of the drive transistor 202. For example, the period of the threshold voltage correction operation may be longer than the period in which both the write transistor 203 and the switching transistor 204 are on (i.e., the length from time t4 to t5).

[0042] In order to appropriately execute the threshold voltage correction operation, the value of the reference potential Vcal may be set so that the gate-source voltage Vgs (i.e., |Vcal - PVDD|) of the drive transistor 23 at time t5 is greater than the threshold voltage Vth of the drive transistor 23.

[0043] Since current flows through the light-emitting element 201 by the correction preparation operation and the threshold voltage correction operation, the light-emitting element 201 emits light. However, by setting the lengths of the correction preparation operation and the threshold voltage correction operation to be sufficiently short with respect to one frame period, the influence of such light emission can be minimized.

[0044] At time t7, the signal output circuit 104 switches the value of the pixel signal SIG to the signal potential Vsig. At time t8, the write scan circuit 103 turns on the write transistor 203 by switching the write scan signal SEL from a high level to a low level. As a result, the signal potential Vsig supplied to the signal line 107 is written to the gate of the drive transistor 202 through the write transistor 203. Thereby, the gate-source voltage Vgs of the drive transistor 202 changes. Assuming that the capacitance value of the capacitor 401 is C1 and the capacitance value of the capacitor 402 is C2, the amount of change in the gate-source voltage Vgs is given by C2×(Vsig - Vcal) / (C1 + C2).

[0045] At time t9, the writing scanning circuit 103 turns off the writing transistor 203 by switching the writing scanning signal SEL from a low level to a high level. As a result, the gate-source voltage Vgs of the driving transistor 202 at this time is held in the capacitance 401 of the capacitance transistor 205.

[0046] At time t10, the light-emitting scanning circuit 105 turns on the switching transistor 204 by switching the light-emitting scanning signal SW from a high level to a low level, as shown in FIG. 6(f). As a result, the driving transistor 202 can supply current from the power supply line 206 to the light-emitting element 201. Specifically, as indicated by the arrow 605, a driving current Ids2 corresponding to the gate-source voltage Vgs of the driving transistor 202 is supplied from the power supply line 206 to the light-emitting element 201 through the driving transistor 202. Therefore, the light-emitting element 201 emits light with a luminance corresponding to the current value of the driving current Ids2.

[0047] In the pixel circuit 101 described above, the conductivity type of the capacitance transistor 205 may be the same as that of the driving transistor 202 (for example, both are P-channel types). The effects of this configuration will be described below. FIG. 7 shows a circuit diagram of a pixel circuit 700 having an N-channel capacitance transistor 701 instead of the P-channel capacitance transistor 205. The back gate of the capacitance transistor 701 is connected to the power supply line 207. Therefore, the capacitance of the capacitance transistor 701 is connected between the power supply line 207 and the node 209. In this configuration, for example, during the light-emitting period, noise from the power supply line 207 may be input to the gate of the driving transistor 202 through the capacitance of the capacitance transistor 701. As a result, image quality degradation such as unevenness and shading may be caused. On the other hand, in the pixel circuit 101, since the capacitance 402 of the capacitance transistor 205 is connected between the node 209 and the power supply line 206, such image quality degradation does not occur.

[0048] Furthermore, all of the plurality of transistors included in the pixel circuit 101 may be transistors of the same conductivity type (for example, P-channel transistors). This can reduce the man-hours in the manufacturing process of the light-emitting device 100, thereby realizing cost reduction.

[0049] The capacitance transistor 205 and the driving transistor 202 may be formed such that the threshold voltage of the capacitance transistor 205 is smaller than the threshold voltage of the driving transistor 202. Thus, even when the gate-source potential Vgs of the driving transistor 202 is small (for example, during low-gray-scale display), as shown in FIG. 8, a channel 800 is formed in the capacitance transistor 205. When the channel 800 is formed in the capacitance transistor 205, the values of the capacitances 401 and 402 of the capacitance transistor 200 increase. Therefore, during low-gray-scale display such as black display, for example, the gate potential Vg of the driving transistor 202 is less affected by the leakage of the writing transistor 203. As a result, a uniform image quality with little luminance variation can be obtained.

[0050] To realize the relationship of the threshold voltages as described above, the capacitance transistor 205 and the driving transistor 202 may be formed such that the channel concentration of the capacitance transistor 205 is higher than the channel concentration of the driving transistor 202. The channel concentration may be the impurity concentration in the region where the channel (for example, the channel 800 in FIG. 8) is formed.

[0051] The above relationship of the threshold voltage may be realized by other methods instead of or in addition to being realized by the difference in channel concentration. For example, in order to realize the relationship of the threshold voltage as described above, the capacitive transistor 205 and the driving transistor 202 may be formed such that the conductivity type of the gate of the capacitive transistor 205 is different from the conductivity type of the gate of the driving transistor 202. Thereby, since the threshold voltage increases only by the difference in work function, the threshold voltage of the capacitive transistor 205 becomes smaller than the threshold voltage of the driving transistor 202. Specifically, the conductivity type (polarity) of the gate of the capacitive transistor 205 may be P-type, and the conductivity type (polarity) of the gate of the driving transistor 202 may be N-type. The above relationship of the threshold voltage may be realized by a method different from the above example.

[0052] The capacitive transistor 205 may be formed on the same semiconductor substrate as the driving transistor 202. Instead of this, the capacitive transistor 205 may be formed on a semiconductor substrate different from the driving transistor 202. By forming the capacitive transistor 205 on a semiconductor substrate different from the driving transistor 202, the areas of the driving transistor 202 and the capacitive transistor 205 can be increased. Generally, the larger the area of the transistor, the smaller the tendency of the characteristic variation. That is, if the area of the driving transistor 202 is increased, the characteristic variation thereof can be reduced. Furthermore, by increasing the area of the capacitive transistor 205, the values of the capacitances 401 and 402 of the capacitive transistor 205 can be increased. As a result, for example, when displaying a low gradation such as black display, the gate potential of the driving transistor 202 is less affected by the leakage of the writing transistor 203, and the image quality is improved.

[0053] FIG. 9 is a circuit diagram in which the transistors included in the pixel circuit 101 are arranged at positions corresponding to their layouts. Referring to FIG. 10, an example of the layouts of the switching transistor 204, the capacitor transistor 205, and the driving transistor 202 will be described. FIG. 10(a) shows a plan view of these transistors, and FIG. 10(b) shows a cross-sectional view taken along line A-A of FIG. 10(a). As shown in FIG. 10, the switching transistor 204, the capacitor transistor 205, and the driving transistor 202 may be formed in the same active region 1000. Thereby, the layout efficiency of these transistors can be improved, and the high definition of the light-emitting device 100 can be achieved.

[0054] Specifically, four impurity regions 1001, 1003, 1007, and 1009 are formed in the active region 1000. Also, three gate electrodes 1002, 1005, and 1008 are formed so as to cover a part of the active region 1000. A gate insulating film (not shown) is formed between each gate electrode and the active region 1000. The impurity region 1003 and the impurity region 1007 are electrically connected by a conductive member 1004. The gate electrode 1005 and the gate electrode 1008 are electrically connected by a conductive member 1006.

[0055] The impurity region 1001 functions as the source of the switching transistor 204. The gate electrode 1002 functions as the gate of the switching transistor 204. The impurity region 1003 functions as the drain of the switching transistor 204 and the source of the capacitor transistor 205. The gate electrode 1005 functions as the gate of the capacitor transistor 205. The impurity region 1007 functions as the drain of the capacitor transistor 205 and the source of the driving transistor 202. The gate electrode 1008 functions as the gate of the driving transistor 202. The impurity region 1009 functions as the drain of the driving transistor 202.

[0056] Referring to FIG. 11, a pixel circuit 1100, which is a modified example of the above-described pixel circuit 101, will be described. The pixel circuit 1100 differs from the pixel circuit 101 in that it further includes a capacitive element 1101, and other points may be the same. The capacitive element 1101 connects the gate of the driving transistor 202 and the source of the driving transistor 202. The capacitive element 1101 may have, for example, a MIM (Metal-Insulator-Metal) structure. The capacitive element 1101 may be formed on the same semiconductor substrate as the driving transistor 202, or may be formed on a different semiconductor substrate. By further including the capacitive element 1101, the value of the capacitance between the gate and the source of the driving transistor 202 can be increased. As a result, for example, a change in the gate potential of the driving transistor 202 due to leakage of the writing transistor 203 during the light emission period can be reduced, and the image quality is improved.

[0057] Referring to FIG. 12, a pixel circuit 1200, which is a modified example of the above-described pixel circuit 101, will be described. The pixel circuit 1200 differs from the pixel circuit 101 in that it further includes a capacitive element 1201, and other points may be the same. The capacitive element 1201 connects the gate of the driving transistor 202 and the power supply line 206. The capacitive element 1201 may have, for example, a MIM structure. The capacitive element 1201 may be formed on the same semiconductor substrate as the driving transistor 202, or may be formed on a different semiconductor substrate. By further including the capacitive element 1201, the value of the capacitance between the gate of the driving transistor 202 and the power supply line 206 can be increased. As a result, during signal writing, the fluctuation of the source potential of the driving transistor 202 can be reduced, and the signal amplitude can be reduced. Thereby, low power consumption of the driving power is realized.

[0058] The pixel circuit 1200 may further include the capacitive element 1101 shown in FIG. 11. Thereby, both the effect obtained by the capacitive element 1101 and the effect obtained by the capacitive element 1201 are realized.

[0059] In the above-described embodiment, the switching transistor 204, the driving transistor 202, and the light-emitting element 201 are connected in series such that the driving transistor 202 is disposed on the path between the switching transistor 204 and the light-emitting element 201. The connection order of the switching transistor 204, the driving transistor 202, and the light-emitting element 201 is not limited to this, and they may be arranged in other orders.

[0060] According to the above-described embodiment, the capacitance for connecting the gate and the source of the driving transistor 202 and the capacitance for connecting the gate of the driving transistor 202 and the power supply line 206 can be realized by one capacitive transistor 205. Thereby, since the number of elements included in the pixel circuit 101 can be limited, for example, reduction of the pixel size and reduction of the cost can be realized. Further, according to the configuration of the pixel circuit 101 in FIG. 2, since the threshold voltage correction operation as described with reference to FIGS. 5 and 6 can be executed, the influence of variations in the threshold voltage of the driving transistor 202 can be reduced, and a high-definition light-emitting device 100 can be realized.

[0061] <Second Embodiment> With reference to FIG. 13, a configuration example of a light-emitting device 1300 according to the second embodiment will be described. The light-emitting device 1300 is different from the light-emitting device 100 in that it has an initialization scanning circuit 1302, has a pixel circuit 1301 instead of the pixel circuit 101, and further has one or more initialization scanning lines 1303-1 to 1303-m, and other points may be the same.

[0062] The initialization scanning circuit 1302 is disposed around the pixel array section 102. The initialization scanning circuit 1302 is an example of a circuit that constitutes a driving section of the light-emitting device 100. The initialization scanning circuit 1302, together with the writing scanning circuit 103 and the light-emitting scanning circuit 105, constitutes a scanning drive system. In the layout shown in FIG. 13, the initialization scanning circuit 1302 is disposed on the right side of the pixel array section 102. Instead of this, other layouts may be used. For example, the initialization scanning circuit 1302 may be disposed on the left side of the pixel array section 102. Also, a layout in which a pair of initialization scanning circuits 1302 are disposed on both the left and right sides of the pixel array section 102 may be used.

[0063] The m initialization scanning lines 1303-1 to 1303-m are disposed in the pixel array section 102 along the pixel rows. The m initialization scanning lines 1303-1 to 1303-m are collectively referred to as the initialization scanning line 1303. One initialization scanning line 1303 may be disposed for one pixel row.

[0064] The initialization scanning line 1303 is connected to a corresponding output terminal among the m output terminals of the initialization scanning circuit 1302. The initialization scanning circuit 1302 is constituted by, for example, a shift register that sequentially shifts start pulses in synchronization with a clock pulse. The initialization scanning circuit 1302 supplies initialization signals RES_1 to RES_m (collectively referred to as the initialization signal RES) to the anodes of the light-emitting elements 201 in synchronization with the line sequential scanning by the writing scanning circuit 103. The initialization signal RES is used to initialize the potential of the anodes of the light-emitting elements 201.

[0065] Referring to FIG. 14, a configuration example of the pixel circuit 1301 will be described. The pixel circuit 1301 is different from the pixel circuit 101 in that it further includes an initialization transistor 1401 and a power supply line 1402, and may be the same in other respects.

[0066] The initialization transistor 1401 is disposed on a path connecting the drain of the drive transistor 202 and the power supply line 1402. In the example of FIG. 14, the initialization transistor 1401 is a P-channel transistor. Alternatively, the initialization transistor 1401 may be an N-channel transistor.

[0067] One of the two main terminals of the initialization transistor 1401 (for example, the source) is connected to the drain of the drive transistor 202. The other of the two main terminals of the initialization transistor 1401 (for example, the drain) is connected to the power supply line 1402. The gate of the initialization transistor 1401 is connected to the initialization scan line 1303.

[0068] The negative power supply potential VSS is supplied to the power supply line 1402. Let the threshold voltage of the light emitting element 201 be Vthel, and let the power supply potential supplied to the power supply line 207 to which the cathode of the light emitting element 201 is connected be Vcath. In this case, the power supply potential VSS is set so as to satisfy the condition VSS < Vthel + Vcath. Thereby, a reverse bias is applied to the light emitting element 201 while the initialization transistor 1401 is in the conductive state. The power supply potential VSS may be the same value as the power supply potential Vcath, or may be a different value. By making the power supply potential VSS and the power supply potential Vcath the same value, the power supply line 207 can be used instead of the power supply line 1402, so that the number of wirings can be reduced.

[0069] The initialization scan circuit 1302 writes the power supply potential VSS to the anode of the light emitting element 201 by turning on the initialization transistor 1401 before the timing of inputting the signal potential Vsig to the gate of the drive transistor 202. As a result, since the anode of the light emitting element 201 becomes VSS during the threshold voltage correction operation, no current flows through the light emitting element 201 during the threshold voltage correction operation. As a result, a phenomenon such as so-called black floating does not occur when displaying a black image, and good contrast can be obtained.

[0070] FIG. 15 is a circuit diagram in which the transistors included in the pixel circuit 1301 are arranged at positions corresponding to their layouts. Referring to FIG. 16, an example of the layouts of the switching transistor 204, the capacitor transistor 205, the driving transistor 202, and the initialization transistor 1401 will be described. FIG. 15 shows a plan view of these transistors. Since the cross-sectional views of these transistors can be inferred from FIG. 10(b), they are omitted.

[0071] As shown in FIG. 15, the switching transistor 204, the capacitor transistor 205, the driving transistor 202, and the initialization transistor may be formed in the same active region 1000. Thereby, the layout efficiency of these transistors can be improved, and the high definition of the light-emitting device 100 can be achieved.

[0072] Specifically, in addition to the four impurity regions 1001, 1003, 1007, and 1009, an impurity region 1601 is formed in the active region 1000. Further, in addition to the three gate electrodes 1002, 1005, and 1008 that cover a part of the active region 1000, a gate electrode 1600 is formed. The impurity region 1009 functions as the drain of the driving transistor 202 and the source of the initialization transistor 1401. The gate electrode 1600 functions as the gate of the initialization transistor 1401. The impurity region 1601 functions as the drain of the initialization transistor 1401.

[0073] Also in the second embodiment, similar to the first embodiment, the pixel circuit 1301 may include either or both of the capacitor elements 1101 and 1201. Also in the second embodiment, similar to the first embodiment, the switching transistor 204, the driving transistor 202, and the light-emitting element 201 may be arranged in another order.

[0074] Also in the second embodiment, the number of elements included in the pixel circuit having the initialization function of the light-emitting element 201 can be reduced.

[0075] <Other Embodiments> FIG. 17 is a schematic diagram showing an example of a display device according to the present embodiment. The display device 1700 may include a touch panel 1703, a display panel 1705, a frame 1706, a circuit board 1707, and a battery 1708 between an upper cover 1701 and a lower cover 1709. Flexible printed circuits FPC 1702 and 1704 are connected to the touch panel 1703 and the display panel 1705. Transistors are printed on the circuit board 1707. The battery 1708 may not be provided if the display device is not a portable device, or may be provided at another position even if it is a portable device.

[0076] The display device according to the present embodiment may include a color filter having red, green, and blue. The red, green, and blue may be arranged in a delta array in the color filter.

[0077] The display device according to the present embodiment may be used as a display unit of a portable terminal. In that case, it may have both a display function and an operation function. Examples of the portable terminal include mobile phones such as smartphones, tablets, and head-mounted displays.

[0078] The display device according to the present embodiment may be used as a display unit of an imaging device including an optical unit having a plurality of lenses and an imaging element that receives light that has passed through the optical unit. The imaging device may include a display unit that displays information acquired by the imaging element. Further, the display unit may be a display unit exposed to the outside of the imaging device or a display unit disposed in a viewfinder. The imaging device may be a digital camera or a digital video camera.

[0079] FIG. 18(a) is a schematic diagram showing an example of the imaging device according to the present embodiment. The imaging device 1800 may include a viewfinder 1801, a rear display 1802, an operation unit 1803, and a housing 1804. The viewfinder 1801 may include the display device according to the present embodiment. In that case, the display device may display not only the image to be captured but also environmental information, imaging instructions, and the like. The environmental information may include the intensity of external light, the direction of external light, the speed at which the subject moves, the possibility that the subject is blocked by an obstacle, and the like.

[0080] Since the timing suitable for imaging is only a short period of time, it is better to display the information earlier. Therefore, it is preferable to use the display device using the organic light-emitting element of the present invention. This is because the organic light-emitting element has a high response speed. The display device using the organic light-emitting element can be more preferably used than these devices, such as a liquid crystal display device, for which a display speed is required.

[0081] The imaging device 1800 has an optical unit (not shown). The optical unit has a plurality of lenses and forms an image on an imaging element housed in the housing 1804. The plurality of lenses can adjust the focus by adjusting their relative positions. This operation can also be performed automatically. The imaging device may be called an optoelectronic conversion device. The optoelectronic conversion device may include, as imaging methods, a method of detecting the difference from a previous image instead of sequentially imaging, a method of cutting out from an image that is always recorded, and the like.

[0082] Figure 18(b) is a schematic diagram showing an example of an electronic device according to this embodiment. The electronic device 1850 includes a display unit 1851, an operation unit 1852, and a housing 1853. The housing 1853 may include a circuit, a printed circuit board having the circuit, a battery, and a communication unit. The operation unit 1852 may be a button or a reaction unit using a touch panel method. The operation unit may be a biometric recognition unit that recognizes a fingerprint to unlock or the like. An electronic device having a communication unit can also be called a communication device. The electronic device may further have a camera function by including a lens and an imaging device. An image captured by the camera function is displayed on the display unit. Examples of the electronic device include a smartphone and a notebook computer.

[0083] Figure 19 is a schematic diagram showing an example of a display device according to this embodiment. Figure 19(a) shows a display device such as a TV monitor or a PC monitor. The display device 1900 has a frame 1901 and a display unit 1902. The light-emitting device according to this embodiment may be used for the display unit 1902.

[0084] It has a frame 1901 and a base 1903 that supports the display unit 1902. The base 1903 is not limited to the form shown in Figure 19(a). The lower side of the frame 1901 may also serve as the base.

[0085] In addition, the frame 1901 and the display unit 1902 may be curved. The radius of curvature may be 5000 mm or more and 6000 mm or less.

[0086] FIG. 19(b) is a schematic diagram showing another example of the display device according to this embodiment. The display device 1950 in FIG. 19(b) is configured to be foldable and is a so-called foldable display device. The display device 1950 includes a first display unit 1951, a second display unit 1952, a housing 1953, and a bending point 1954. The first display unit 1951 and the second display unit 1952 may include the light-emitting device according to this embodiment. The first display unit 1951 and the second display unit 1952 may be a single seamless display device. The first display unit 1951 and the second display unit 1952 can be separated at the bending point. The first display unit 1951 and the second display unit 1952 may display different images, or may display a single image together with the first and second display units.

[0087] FIG. 20(a) is a schematic diagram showing an example of the lighting device according to this embodiment. The lighting device 2000 may include a housing 2001, a light source 2002, a circuit board 2003, an optical film 2004, and a light diffusing portion 2005. The light source may include the organic light-emitting element according to this embodiment. The optical filter may be a filter that improves the color rendering property of the light source. The light diffusing portion can effectively diffuse the light of the light source, such as lighting up, and deliver the light to a wide range. The optical filter and the light diffusing portion may be provided on the light-emitting side of the lighting. If necessary, a cover may be provided on the outermost side.

[0088] The lighting device is, for example, a device for lighting an interior. The lighting device may emit any color from white, day white, or other blue to red. It may have a dimming circuit for dimming them. The lighting device may include the organic light-emitting element of the present invention and a power supply circuit connected thereto. The power supply circuit is a circuit that converts an AC voltage into a DC voltage. Also, white means a color temperature of 4200K and day white means a color temperature of 5000K. The lighting device may have a color filter.

[0089] Also, the lighting device according to this embodiment may have a heat radiating portion. The heat radiating portion releases the heat inside the device to the outside of the device, and examples thereof include a metal with a high specific heat and liquid silicon.

[0090] Figure 20(b) is a schematic diagram of an automobile, which is an example of a moving body according to the present embodiment. The automobile has a tail lamp, which is an example of a lighting device. The automobile 2050 may have a tail lamp 2051 and may be configured to turn on the tail lamp when a braking operation or the like is performed.

[0091] The tail lamp 2051 may have an organic light-emitting element according to the present embodiment. The tail lamp may have a protective member for protecting the organic EL element. The protective member has a certain degree of strength and may be made of any material as long as it is transparent, but is preferably made of polycarbonate or the like. A phthalic acid derivative, an acrylonitrile derivative, or the like may be mixed into the polycarbonate.

[0092] The automobile 2050 may have a vehicle body 2053 and a window 2052 attached thereto. The window may be a transparent display as long as it is not a window for checking the front and rear of the automobile. The transparent display may have an organic light-emitting element according to the present embodiment. In this case, constituent materials such as electrodes of the organic light-emitting element are made of transparent members.

[0093] The moving body according to the present embodiment has a driving unit such as an engine and a motor, and a moving unit such as wheels, a propeller, and tires. For example, the moving body may be an automobile, a ship, an aircraft, a drone, a bicycle, a railway vehicle, or the like. The moving body may have a body and a lighting device provided on the body. The lighting device may emit light to indicate the position of the body. The lighting device has an organic light-emitting element according to the present embodiment.

[0094] With reference to Figure 21, application examples of the display device of each of the above embodiments will be described. The display device can be applied to a system that can be worn as a wearable device such as smart glasses, an HMD, or smart contacts. The imaging display device used in such application examples has an imaging device capable of photoelectrically converting visible light and a display device capable of emitting visible light.

[0095] FIG. 21(a) illustrates glasses 2100 (smart glasses) according to one application example. An imaging device 2102 such as a CMOS sensor or a SPAD is provided on the front surface side of the lens 2101 of the glasses 2100. Also, a display device according to each of the above-described embodiments is provided on the back surface side of the lens 2101.

[0096] The glasses 2100 further include a control device 2103. The control device 2103 functions as a power supply that supplies power to the imaging device 2102 and the display device according to each embodiment. Also, the control device 2103 controls the operations of the imaging device 2102 and the display device. An optical system for condensing light onto the imaging device 2102 is formed in the lens 2101.

[0097] FIG. 21(b) illustrates glasses 2150 (smart glasses) according to one application example. The glasses 2150 have a control device 2152. An imaging device corresponding to the imaging device 2102 and a display device are mounted on the control device 2152. An optical system for projecting the light emitted by the display device in the control device 2152 is formed in the lens 2151, and an image is projected onto the lens 2151. The control device 2152 functions as a power supply that supplies power to the imaging device and the display device, and controls the operations of the imaging device and the display device. The control device may have a gaze detection unit that detects the wearer's gaze. Infrared rays may be used for gaze detection. The infrared light emitting unit emits infrared light toward the eyeball of the user who is gazing at the display image. An imaging unit having a light receiving element detects the reflected light of the emitted infrared light from the eyeball, thereby obtaining an imaging image of the eyeball. By having a reduction unit that reduces the light from the infrared light emitting unit to the display unit in a plan view, a decrease in image quality is reduced.

[0098] The user's gaze with respect to the display image is detected from the imaging image of the eyeball obtained by imaging infrared light. Any known method can be applied to gaze detection using the imaging image of the eyeball. As an example, a gaze detection method based on a Purkinje image by reflection of irradiation light on the cornea can be used.

[0099] More specifically, a gaze detection process based on the pupil corneal reflex method is performed. Using the pupil corneal reflex method, a gaze vector representing the orientation (rotation angle) of the eyeball is calculated based on the image of the pupil and the Purkinje image included in the captured image of the eyeball, thereby detecting the user's gaze.

[0100] A display device according to an embodiment of the present invention may include an imaging device having a light receiving element, and may control a display image of the display device based on user gaze information from the imaging device.

[0101] Specifically, the display device determines a first display area that the user is gazing at and a second display area other than the first display area based on the gaze information. The first display area and the second display area may be determined by a control device of the display device, or the display device may receive those determined by an external control device. In the display area of the display device, the display resolution of the first display area may be controlled to be higher than that of the second display area. That is, the resolution of the second display area may be made lower than that of the first display area.

[0102] Also, the display area has a first display area and a second display area different from the first display area, and based on the gaze information, an area with a higher priority is determined from the first display area and the second display area. The first display area and the second display area may be determined by a control device of the display device, or the display device may receive those determined by an external control device. The resolution of the area with a higher priority may be controlled to be higher than that of the area other than the area with a higher priority. That is, the resolution of the area with a relatively lower priority may be made lower.

[0103] Note that AI may be used to determine the first display area or the area with a higher priority. AI may be a model configured to estimate the angle of the gaze and the distance to the target at the tip of the gaze from an image of the eyeball using the image of the eyeball and the direction in which the eyeball in the image is actually looking as teacher data. The AI program may be possessed by the display device, the imaging device, or an external device. When an external device has it, it is transmitted to the display device via communication.

[0104] When performing display control based on visual recognition, it can be preferably applied to smart glasses further having an imaging device for imaging the outside. The smart glasses can display the imaged external information in real time.

[0105] <Summary of Embodiment> [Item 1] A light-emitting device, a light-emitting element, a driving transistor and a switching transistor respectively arranged on a path through which a current for causing the light-emitting element to emit light flows, a writing transistor arranged on a path connecting a signal line to which a pixel signal is supplied and the gate of the driving transistor, a capacitive transistor for holding the voltage between the gate and source of the driving transistor, comprising: the gate of the capacitive transistor is connected to the gate of the driving transistor, each of the source and drain of the capacitive transistor is connected to the source of the driving transistor, the capacitive transistor and the switching transistor are formed in the same impurity region, a light-emitting device in which the conductivity type of the capacitive transistor is the same as that of the driving transistor. [Item 2] The driving transistor according to item 1, wherein the driving transistor is arranged on a path connecting the light-emitting element and the switching transistor. [Item 3] The light-emitting device according to item 1 or 2, wherein the threshold voltage of the capacitive transistor is smaller than the threshold voltage of the driving transistor. [Item 4] The light-emitting device according to item 3, wherein the channel concentration of the capacitive transistor is higher than the channel concentration of the driving transistor. [Item 5] The light-emitting device according to item 3 or 4, wherein the conductivity type of the gate of the capacitive transistor is different from the conductivity type of the gate of the driving transistor. [Item 6] The light-emitting device according to any one of Items 1 to 5, wherein the switching transistor, the capacitor transistor, and the driving transistor are formed in the same active region. [Item 7] The light-emitting device according to any one of Items 1 to 6, wherein the capacitor transistor is formed on a semiconductor substrate different from the driving transistor. [Item 8] The light-emitting device according to any one of Items 1 to 7, further comprising a first capacitor element that connects the gate of the driving transistor and the source of the driving transistor. [Item 9] The light-emitting device according to any one of Items 1 to 8, further comprising a second capacitor element that connects the source of the driving transistor and a power supply line. [Item 10] The light-emitting device according to any one of Items 1 to 9, further comprising an initialization transistor disposed on a path connecting the drain of the driving transistor and the power supply line. [Item 11] The light-emitting device according to Item 10, wherein the switching transistor, the capacitor transistor, the driving transistor, and the initialization transistor are formed in the same active region. Arrangement. [Item 12] The light-emitting device according to any one of Items 1 to 11, wherein the back gate of the capacitor transistor and the source of the switching transistor are connected to the same power supply line. [Item 13] A display device, comprising: the light-emitting device according to any one of Items 1 to 12; and an active element connected to the light-emitting device. [Item 14] An optoelectronic conversion device, comprising: an optical unit having a plurality of lenses; an imaging element that receives light that has passed through the optical unit; and a display unit that displays an image, wherein the display unit is a display unit that displays an image captured by the imaging element, and has the light-emitting device according to any one of Items 1 to 12. [Item 15] It has a housing provided with a display unit, and a communication unit provided in the housing for communicating with the outside. The electronic device is characterized in that the display unit has the light-emitting device according to any one of Items 1 to 12. [Item 16] An illumination device having a light source and at least one of a light diffusion part and an optical film. The illumination device is characterized in that the light source has the light-emitting device according to any one of Items 1 to 12. [Item 17] A moving body having a body and a lighting fixture provided on the body. The moving body is characterized in that the lighting fixture has the light-emitting device according to any one of Items 1 to 12.

[0106] The invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, claims are attached to disclose the scope of the invention.

Explanation of Signs

[0107] 100 Light-emitting device, 101 Pixel circuit, 205 Capacitance transistor

Claims

1. 1. A light emitting device, comprising: A light-emitting element; a driving transistor and a switching transistor, each of which is disposed on a path through which a current flows for causing the light-emitting element to emit light; a write transistor disposed on a path connecting a signal line to which a pixel signal is supplied and the gate of the drive transistor; a capacitance transistor for holding a gate-source voltage of the drive transistor; a gate of the capacitance transistor is connected to the gate of the drive transistor; The source and drain of the capacitance transistor are each connected to the source of the drive transistor; the capacitance transistor and the switching transistor are formed in the same impurity region, A light emitting device, wherein the capacitance transistor has the same conductivity type as the drive transistor.

2. The light emitting device according to claim 1 , wherein the driving transistor is disposed on a path connecting the light emitting element and the switching transistor.

3. The light emitting device according to claim 1 , wherein a threshold voltage of the capacitance transistor is lower than a threshold voltage of the drive transistor.

4. The light emitting device according to claim 3 , wherein a channel concentration of the capacitance transistor is higher than a channel concentration of the drive transistor.

5. The light emitting device according to claim 3 , wherein the gate of the capacitance transistor has a different conductivity type from the gate of the drive transistor.

6. The light emitting device according to claim 1 , wherein the switching transistor, the capacitance transistor, and the drive transistor are formed in a same active region.

7. The light emitting device according to claim 1 , wherein the capacitance transistor is formed on a semiconductor substrate separate from the drive transistor.

8. The light emitting device according to claim 1 , further comprising a first capacitance element connecting the gate of the driving transistor and the source of the driving transistor.

9. The light emitting device according to claim 1 , further comprising a second capacitive element connecting a source of the driving transistor and a power supply line.

10. The light emitting device according to claim 1 , further comprising an initialization transistor disposed on a path connecting the drain of the drive transistor and a power supply line.

11. The light emitting device according to claim 10 , wherein the switching transistor, the capacitance transistor, the drive transistor, and the initialization transistor are formed in a same active region. Place.

12. The light emitting device according to claim 1 , wherein a back gate of the capacitance transistor and a source of the switching transistor are connected to a same power supply line.

13. A display device comprising: a light-emitting device according to claim 1 ; and an active element connected to the light-emitting device.

14. The imaging device includes an optical unit having a plurality of lenses, an image sensor that receives light that has passed through the optical unit, and a display unit that displays an image, A photoelectric conversion device, comprising: the display unit for displaying an image captured by the imaging element; and the light-emitting device according to claim 1 .

15. A display device having a housing and a communication unit provided in the housing for communicating with an external device, 13. An electronic device, comprising: a display unit comprising the light-emitting device according to claim 1.

16. A lighting device having a light source and at least one of a light diffusion unit and an optical film, 13. An illumination device, characterized in that the light source comprises a light emitting device according to claim 1.

17. A moving body having a body and a lighting device provided on the body, A moving body, comprising: a lighting device comprising the light-emitting device according to claim 1 .

Images