Light emitting device for display device miniaturizing pixels and suppressing degradation in image quality

A light emitting device comprising a plurality of pixels is provided. Each of the plurality of pixels includes a light emitting element, a first transistor having a drain region connected to the light emitting element, and a second transistor having a drain region connected to a gate electrode of the first transistor. The plurality of pixels include a first pixel and a second pixel, which are adjacent to each other in a first direction. A source region of the second transistor of the first pixel and a source region of the second transistor of the second pixel share one diffusion region, and a source region, a gate electrode, and the drain region of the first transistor of the first and second pixels are sequentially arranged in one of a positive direction and a negative direction in the first direction.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a light emitting device, a display device, a photoelectric conversion device, an electronic device, an illumination device, and a mobile device.

Description of the Related Art

There is known a light emitting device in which pixels each including a light emitting element such as an organic EL (electroluminescence) element that emits light with luminance corresponding to a current flowing through the element are arranged. In Japanese Patent Laid-Open No. 2014-186258, FIG. 38 shows a state in which write transistors WSTr of two pixels adjacent to each other in a row direction are connected to the same data line DTL arranged in a column direction.

If transistors are formed in a circuit arrangement described in Japanese Patent Laid-Open No. 2014-186258, a diffusion region forming the main terminals, connected to the data line, of the write transistors of the two pixels is shared, and thus miniaturization of pixel is possible. As miniaturization of pixel advances, the influence when the positional relationship between a diffusion region and a gate electrode deviates due to alignment accuracy of a mask pattern at the time of forming transistors or the like may become large. If the positional relationship between the diffusion region and the gate electrode deviates among pixels, the electrical characteristic may change in a driving transistor for causing the light emitting element to emit light with luminance corresponding to luminance information, thereby degrading display image quality. The positional relationship between the diffusion region and the gate electrode may deviate in the same direction among transistors formed with the same exposure.

SUMMARY OF THE INVENTION

Some embodiments of the present invention provide a technique advantageous in miniaturizing pixels and suppressing degradation in image quality in a light emitting device.

According to some embodiments, a light emitting device comprising a plurality of pixels arranged on a substrate in an array in a first direction and a second direction intersecting the first direction, wherein each of the plurality of pixels includes a light emitting element, a first transistor having a drain region connected to an anode of the light emitting element, and a second transistor having a drain region connected to a gate electrode of the first transistor, the plurality of pixels include a first pixel and a second pixel, which are adjacent to each other in the first direction, a source region of the second transistor of the first pixel and a source region of the second transistor of the second pixel share one diffusion region, and a source region, a gate electrode, and the drain region of the first transistor of the first pixel and a source region, a gate electrode, and the drain region of the first transistor of the second pixel are sequentially arranged in one of a positive direction and a negative direction in the first direction, is provided.

DESCRIPTION OF THE EMBODIMENTS

The structure of a light emitting device according to the first embodiment of the present invention will be described with reference toFIGS.1to5.FIG.1is a view showing an example of the arrangement of a light emitting device101according to this embodiment.FIG.2is a circuit diagram showing an example of the arrangement of one pixel102of the light emitting device101shown inFIG.1.FIG.3is a circuit diagram showing the connection relationship between two adjacent pixels102.

In this specification, a case will be described in which a driving transistor202is connected to the anode of a light emitting element201and all transistors arranged in the pixel102are p-type transistors. However, the arrangement of the light emitting device101is not limited to this. The polarity of the light emitting element201and the conductivity types of the transistors arranged in the pixel102may all be reversed. Alternatively, for example, the driving transistor202may be a p-type transistor and the remaining transistors may be n-type transistors. Supplied potentials and connection are changed appropriately in accordance with the polarity and conductive types so that the light emitting element201emits light in a predetermined light amount. Therefore, for example, the “drain region” and “source region” of each transistor may be reversed.

As shown inFIG.1, an organic EL light emitting device as an example of the light emitting device101includes a pixel array portion103and a driving unit arranged in the periphery of the pixel array portion103. In the pixel array portion103, the plurality of pixels102are arranged on a substrate in an array in an X direction and a Y direction intersecting the X direction, as shown inFIG.1. As shown inFIG.1, the X and Y directions may be orthogonal to each other. As shown inFIG.2, each pixel102includes the light emitting element201. The light emitting element201includes an organic layer with a light emitting layer between the anode and the cathode. The organic layer may appropriately include one or more of a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer in addition to the light emitting layer.

The driving unit is a circuit for driving each pixel102. For example, the driving unit includes a vertical scanning circuit104and a signal output circuit105. In the pixel array portion103, a scanning line106is arranged for each pixel row in a row direction (the Y direction inFIG.1). In the pixel array portion103, a signal line107is arranged for each pixel column in a column direction (the X direction inFIG.1). Each scanning line106is connected to the output terminal of a corresponding row of the vertical scanning circuit104. Each signal line107is connected to the output terminal of a corresponding column of the signal output circuit105. The vertical scanning circuit104supplies a write control signal to the scanning line106at the time of writing a video signal in each pixel102of the pixel array portion103. The signal output circuit105outputs a luminance signal with a voltage corresponding to luminance information.

As shown inFIG.2, each pixel102includes the light emitting element201, the driving transistor202, and a write transistor203. More specifically, one (a drain region in the arrangement shown inFIG.2) of the two main terminals of the driving transistor202is connected to the anode of the two electrodes of the light emitting element201. The other (a source region in the arrangement shown inFIG.2) of the two main terminals of the driving transistor202is connected to a power supply potential Vdd. The cathode of the two electrodes of the light emitting element201is connected to a power supply potential Vss. The power supply potential Vss may be, for example, a ground potential. The main terminal of the transistor indicates a diffusion region functioning as the source or drain region of the transistor. The control terminal of the transistor indicates the gate electrode of the transistor.

One (a drain region in the arrangement shown inFIG.2) of the two main terminals of the write transistor203is connected to the control terminal (gate electrode) of the driving transistor202. The other (a source region in the arrangement shown inFIG.2) of the two main terminals of the write transistor203is connected to the signal line107. The gate electrode of the write transistor203is connected to the scanning line106.

The total number of transistors, the total number of capacitive elements (to be described later), and a combination of the conductivity types of the transistors are merely examples, and the present invention is not limited to this arrangement. In the following description, when a transistor is connected between elements A and B, one of the main terminals of the transistor is connected to element A and the other of the main terminals of the transistor is connected to element B. That is, when a transistor is connected between elements A and B, a case in which the control terminal of the transistor is connected to element A, one of the main terminals is not connected to element A, and the other of the main terminals is not connected to element B is excluded.

The driving transistor202supplies a current from the power supply potential Vdd to the light emitting element201, thereby causing the light emitting element201to emit light. More specifically, the driving transistor202supplies a current corresponding to the signal voltage of the signal line107to the light emitting element201. This current-drives the light emitting element201to emit light.

The write transistor203is rendered conductive in response to a write control signal applied to the gate electrode of the write transistor203from the vertical scanning circuit104via the scanning line106. Thus, the write transistor203writes, in the pixel102, the signal voltage of a video signal corresponding to luminance information supplied from the signal output circuit105via the signal line107. The written signal voltage is applied to the gate electrode of the driving transistor202.

An organic EL (Organic Electroluminescent) element can be used as the light emitting element201. When the light emitting element201emits light, the amount of a current flowing through the driving transistor202changes in accordance with the signal voltage applied to the gate electrode of the driving transistor202from the signal line107via the write transistor203. This charges the capacitance between the anode and the cathode of the light emitting element201to a predetermined potential, and a current corresponding to the potential difference flows. Thus, the light emitting element201emits light with predetermined luminance.

Next, the two adjacent pixels102will be described with reference toFIG.3. As shown inFIG.3, the plurality of pixels102arranged in the pixel array portion103include pixels102aand102badjacent to each other in the X direction. When indicating a specific one of the pixels102, a suffix such as “a” or “b” is appended to a reference numeral like “pixel102“a””. When any pixel is possible without specifying it, “pixel102” is simply used. The same applies to the remaining components.

The pixel102aincludes a light emitting element201a, a driving transistor202a, and a write transistor203a. The pixel102bincludes a light emitting element201b, a driving transistor202b, and a write transistor203b. The source region of the write transistor203aof the pixel102aand the source region of the write transistor203bof the pixel102bare connected via the signal line107. In this way, the two pixels102aand102bin which the source regions of the write transistors203are connected to each other form one pixel group301.

FIG.4shows an example of the arrangement of the transistors of the circuit shown inFIG.3.FIG.4shows four pixel groups301each formed by the pixels102aand102b. In each pixel group301, the write transistor203aof the pixel102aand the write transistor203bof the pixel102bare arranged between the driving transistor202aof the pixel102aand the driving transistor202bof the pixel102b.

The write transistor203aincludes a p-type diffusion region401, a gate electrode402a, and a p-type diffusion region403a. The write transistor203bincludes the p-type diffusion region401, a gate electrode402b, and a p-type diffusion region403b. As shown inFIG.4, the write transistors203aand203bshare the diffusion region401connected to the signal line107. In other words, the source region of the write transistor203aof the pixel102aand the source region of the write transistor203bof the pixel102bshare one diffusion region401. This makes it possible to miniaturize the pixels102(pixel groups301), as compared with a case in which a diffusion region forming the source region of the write transistor203aand a diffusion region forming the source region of the write transistor203bare separately arranged in the X direction.

The driving transistor202aof the pixel102aincludes a p-type diffusion region404a, a gate electrode405a, and a p-type diffusion region406a. The diffusion region404ais connected to the power supply potential Vdd to function as the source region of the driving transistor202a. The diffusion region406ais connected to the anode of the light emitting element201ato function as the drain region of the driving transistor202a. The driving transistor202bof the pixel102bincludes a p-type diffusion region404b, a gate electrode405b, and a p-type diffusion region406b. The diffusion region404bis connected to the power supply potential Vdd to function as the source region of the driving transistor202b. The diffusion region406bis connected to the anode of the light emitting element201bto function as the drain region of the driving transistor202b.

As described above, the source region (diffusion region404a), the gate electrode405a, and the drain region (diffusion region406a) of the driving transistor202aof the pixel102aand the source region (diffusion region404b), the gate electrode405b, and the drain region (diffusion region406b) of the driving transistor202bof the pixel102bare sequentially arranged in the positive X direction. That is, a direction in which a current flows from the power supply potential Vdd to the power supply potential Vss through the driving transistor202and the light emitting element201is the same between the pixels102aand102b. The positive direction corresponds to a direction indicated by an arrow as the X direction inFIG.4. Although the source region, gate electrode, and drain region of each of the driving transistors202aand202bof the pixels102aand102bare sequentially arranged in the positive X direction inFIG.4, the present invention is not limited to this. For example, the source region, gate electrode, and drain region of each of the driving transistors202aand202bmay be arranged in the negative X direction.

As miniaturization of the pixel102(pixel group301) advances, the positional relationship between the diffusion region and the gate electrode may deviate from design due to alignment accuracy of a mask pattern at the time of forming the pixel. If the positional relationship between the diffusion region and the gate electrode deviates, the electrical characteristic of the formed transistor may change from a design value. In addition, as transistor miniaturizing advances, the influence when the positional relationship between the diffusion region and the gate electrode deviates may become conspicuous. The positional relationship between the diffusion region and the gate electrode may deviate in the same direction among transistors formed with the same exposure. At this time, consider a case in which currents flow in the opposite directions in the driving transistor202aof the pixel102aand the driving transistor202bof the pixel102b. In this case, since the positional relationship between the diffusion region and the gate electrode deviates in the same direction, if a current larger than a design value flows through the driving transistor202a, a current flowing through the driving transistor202bmay become smaller than a design value. Therefore, a luminance unevenness may occur between the pixels102aand102b, thereby degrading the display image quality.

On the other hand, in this embodiment, the directions of currents for causing the light emitting elements201to emit light, which flow through the driving transistor202aof the pixel102aand the driving transistor202bof the pixel102b, are the same. Therefore, if a current larger than the design value flows through the driving transistor202a, a current larger than the design value also flows through the driving transistor202b. Thus, in the light emitting device101according to this embodiment, a difference in electrical characteristic of the driving transistor202between the pixels102can be reduced, thereby suppressing degradation in display image quality. For example, in all the pixels102arranged in the pixel array portion103of the light emitting device101, the source regions, gate electrodes, and drain regions of the driving transistors202may be arranged in the same direction.

FIG.5is a sectional view of the pixel group301shown inFIG.4, which is taken along a line Y1-Y1′. The light emitting element201includes an electrode501(to also be referred to as a lower electrode hereinafter), an organic layer502including a light emitting layer, and an electrode503(to also be referred to as an upper electrode hereinafter). The electrode501is arranged for each light emitting element201. As shown inFIG.5, an electrode501ais arranged in the light emitting element201a, and an electrode501bis arranged in the light emitting element201b. The organic layer502and the electrode503can be shared by the plurality of light emitting elements201. For example, the light emitting element201of all the pixels102arranged in the pixel array portion103may share the organic layer502and the electrode503.

As shown inFIG.5, a bank portion504may be arranged in an end portion of the electrode501. The bank portion504can be arranged to surround the outer circumference of the electrode501. The bank portion504can reduce leakage of a current flowing between the electrode501aand the electrode503into the adjacent pixel102. The electrode501and the diffusion region406functioning as the source region of the driving transistor202are connected via a via505and a wiring layer506.

Each transistor described above is formed on a substrate510. The substrate510can be a semiconductor substrate of, for example, p-type doped silicon. An n-type well layer507is arranged on a p-type semiconductor layer509of the substrate510, and the diffusion regions401,403,404, and406are formed in the well layer507. The well layer507is connected to the power supply potential Vdd. Each transistor is separated by an insulator isolation portion508. The insulator isolation portion508electrically isolates each transistor by an appropriate method such as STI (Shallow Trench Isolation), LOCOS (Local Oxidation Of Silicon), or n-type diffusion region isolation.

FIG.5shows only one wiring layer506between the diffusion regions401,403,404, and406and the layer in which the electrodes501are arranged. The present invention, however, is not limited to this, and a plurality of wiring layers may be arranged. In this case, the diffusion regions401,403,404, and406may be respectively connected to wiring patterns arranged in different wiring layers or wiring patterns arranged in the same wiring layer.

The structure of a light emitting device according to the second embodiment of the present invention will be described with reference toFIGS.6to13. In this embodiment, as compared with the above-described first embodiment, a light emission control transistor is connected between a power supply potential Vdd and a driving transistor202. Components different from the above-described first embodiment will mainly be described below.

FIG.6is a view showing an example of the arrangement of a light emitting device101according to this embodiment. As shown inFIG.6, in a pixel array portion103, a scanning line601is arranged for each pixel row in the Y direction in addition to the above-described first embodiment. Each scanning line601is connected to the output terminal of a corresponding row of a vertical scanning circuit104, and supplies a light emission control signal to each pixel102.

FIG.7is a circuit diagram showing an example of the arrangement of one pixel102of the light emitting device101shown inFIG.6. As shown inFIG.7, a light emission control transistor701is connected between the power supply potential Vdd and the driving transistor202in addition to the above-described first embodiment. One (a drain region in the arrangement shown inFIG.7) of the two main terminals of the light emission control transistor701is connected to one (a source region in the arrangement shown inFIG.7) of the two main terminals of the driving transistor202. The other (a source region in the arrangement shown inFIG.7) of the two main terminals of the light emission control transistor701is connected to the power supply potential Vdd. The control terminal (gate electrode) of the light emission control transistor701is connected to the scanning line601. Furthermore, a capacitive element702is connected between the gate electrode and the source electrode of the driving transistor202, and a capacitive element703is connected between the power supply potential Vdd and the source electrode of the driving transistor202.

The light emission control transistor701is rendered conductive in response to the light emission control signal applied from the vertical scanning circuit104to the gate electrode via the scanning line601, thereby allowing a current to be supplied from the power supply potential Vdd to the driving transistor202. This allows the driving transistor202to drive a light emitting element201. That is, by controlling the conductive state of the current path, the light emission control transistor701functions as a switch element that controls light emission or non-light emission of the light emitting element201.

As described above, a switching operation of the light emission control transistor701can provide a period (non-emission period) during which the light emitting element201is in a non-emission state, and control the ratio between the non-emission period and an emission period during which the light-emitting element201emits light (so-called duty control). This duty control can reduce afterimage blurring accompanying light emission from the light emitting element201of each pixel102over a period of one frame, and further improve the image quality of a moving image in particular.

FIG.8is a circuit diagram showing the connection relationship between two adjacent pixels102. As shown inFIG.8, the plurality of pixels102arranged in the pixel array portion103include pixels102aand102badjacent to each other in the X direction. Similar to the above-described first embodiment, the source region of a write transistor203aof the pixel102aand the source region of a write transistor203bof the pixel102bare connected via the signal line107to form one pixel group801. The pixel102aincludes a light emission control transistor701a, a capacitive element702a, and a capacitive element703a, in addition to the pixel102aaccording to the first embodiment. The pixel102bincludes a light emission control transistor701b, a capacitive element702b, and a capacitive element703b, in addition to the pixel102baccording to the first embodiment.

FIG.9shows an example of the arrangement of the transistors of the circuit shown inFIG.8.FIG.9shows four pixel groups801each formed by the pixels102aand102b. In each pixel group801, the write transistor203aof the pixel102aand the write transistor203bof the pixel102bare arranged between a driving transistor202aof the pixel102aand a driving transistor202bof the pixel102b. In addition, the light emission control transistor701aof the pixel102ais arranged between the driving transistor202aand the write transistor203aof the pixel102ain the X direction. The light emission control transistor701bof the pixel102bis arranged on the side, opposite to the pixel102a, of the driving transistor202bof the pixel102bin the X direction.

As shown inFIG.9, the light emission control transistor701aincludes a p-type diffusion region901a, a gate electrode902a, and a p-type diffusion region404a. The diffusion region901ais connected to the power supply potential Vdd to function as the source region of the light emission control transistor701a. The drain region of the light emission control transistor701aand the source region of the driving transistor202ashare one diffusion region404a. This can miniaturize the pixel102(pixel group801), as compared with a case in which the diffusion region forming the drain region of the light emission control transistor701aand the diffusion region forming the source region of the driving transistor202aare separately arranged in the X direction. Similarly, the light emission control transistor701bincludes a p-type diffusion region901b, a gate electrode902b, and a p-type diffusion region404b. The diffusion region901bis connected to the power supply potential Vdd to function as the source region of the light emission control transistor701b. The drain region of the light emission control transistor701band the source region of the driving transistor202bshare one diffusion region404b.

In this embodiment as well, the source region (diffusion region404a), a gate electrode405a, and the drain region (diffusion region406a) of the driving transistor202aof the pixel102aand the source region (diffusion region404b), a gate electrode405b, and the drain region (diffusion region406b) of the driving transistor202bof the pixel102bare sequentially arranged in the positive X direction. Thus, similar to the above-described first embodiment, in the light emitting device101, a difference in electrical characteristic of the driving transistor202between the pixels102can be reduced, thereby suppressing degradation in display image quality. Furthermore, in this embodiment, the source region (diffusion region901a), the gate electrode902a, the drain region (diffusion region404a) of the light emission control transistor701aof the pixel102aand the source region (diffusion region901b), the gate electrode902b, and the drain region (diffusion region404b) of the light emission control transistor701bof the pixel102bare sequentially arranged in the positive X direction. Thus, in the light emitting device101, a difference in electrical characteristic of the light emission control transistor701between the pixels102can be reduced, thereby suppressing degradation in display image quality. As shown inFIG.9, in the pixel102, the arrangement order of the source region, gate electrode, and drain region of the driving transistor202in the positive X direction may be the same as that of the source region, gate electrode, and drain region of the light emission control transistor701. For example, with respect to each of the light emission control transistors701aand701b, the source region, gate electrode, and drain region may be arranged in this order in the negative X direction.

In this embodiment, the light emission control transistor701aof the pixel102aand the light emission control transistor701bof the pixel102bare arranged so that currents flow in the same direction. However, the present invention is not limited to this, and currents need not flow in the same direction. For example, the light emission control transistor701aarranged in the pixel102aand the light emission control transistor701barranged in the pixel102bmay be designed so that currents flow in the opposite directions. This is implemented when the driving transistor202causes a current to flow in response to a luminance signal with a voltage corresponding to luminance information while the light emission control transistor701controls light emission or non-light emission of the light emitting element201. Thus, the control accuracy of the light emission control transistor701may be lower than that of the driving transistor202. Therefore, in accordance with the arrangement of the pixels102and the pixel groups801, the flow direction of a current in each light emission control transistor701may be decided appropriately.

Next, a wiring pattern903for connecting the gate electrode405of the driving transistor202and the diffusion region403forming the drain region of the write transistor will be described. In the above-described first embodiment, as shown inFIG.4, the distance between the gate electrode405of the driving transistor202and the diffusion region403forming the drain region of the write transistor is almost the same. Therefore, the length of the wiring pattern903is almost the same between the pixels102aand102b, and the parasitic capacitance of the wiring pattern903is almost the same between the pixels102aand102b. On the other hand, in the arrangement shown inFIG.9, the distance between the gate electrode405of the driving transistor202and the diffusion region403forming the drain region of the write transistor is different between the pixels102aand102b. A wiring pattern indicates a conductor wiring for electrically connecting two or more target objects. A wiring of the same shape need not always be used repeatedly.

A wiring pattern903ais a wiring pattern for connecting the gate electrode405aof the driving transistor202aand the diffusion region403aforming the drain region of the write transistor203a. A wiring pattern903bis a wiring pattern for connecting the gate electrode405bof the driving transistor202band the diffusion region403bforming the drain region of the write transistor203b. A length904ais a length between the gate electrode405aof the driving transistor202aand the contact portion of the diffusion region403aforming the drain region of the write transistor203a. Similarly, a length904bis a length between the gate electrode405bof the driving transistor202band the contact portion of the diffusion region403bforming the drain region of the write transistor203b. A length905ais the length of a portion where the wiring pattern903aoverlaps the gate electrode405aof the driving transistor202a. Similarly, a length905bis the length of a portion where the wiring pattern903boverlaps the gate electrode405bof the driving transistor202b.

In the arrangement shown inFIG.9, the length904aof the pixel102ais longer than the length904bof the pixel102b. To the contrary, the length905aof the pixel102ais shorter than the length905bof the pixel102b. This can increase the parasitic capacitance of the wiring pattern903bto be almost equal to the parasitic capacitance of the wiring pattern903a. As a result, the gate-source capacitance of the driving transistor202afor holding a voltage corresponding to luminance information is almost equal to that of the driving transistor202b, thereby reducing the difference in electrical characteristic between the pixels102aand102b. This can reduce a luminance unevenness between the pixels102aand102b, thereby suppressing degradation in display image quality.

In the arrangement shown inFIG.9, the length904ais longer than the length904b, and thus the length905ais shorter than the length905b. However, if the length904ais shorter than the length904b, the length905ais made longer than the length905b. As shown inFIG.9, the wiring pattern903is arranged in the X direction on the gate electrode405. However, the wiring pattern903may be arranged to bend from the X direction to the Y direction. Furthermore, as shown inFIG.9, the wiring pattern903bmay extend from the gate electrode405bon the side opposite to the pixel102a.

FIG.10is a sectional view of the pixel group801shown inFIG.9, which is taken along a line Y2-Y2′. As shown inFIG.10, an electrode501and a diffusion region406forming the source region of the driving transistor202are connected via a via505and wiring layers506,1001, and1002. The capacitive element702has a structure that includes an insulating layer between an electrode1003arranged in the wiring layer1001and an electrode1004. The capacitive element703has a structure that includes an insulating film between an electrode1005arranged in the wiring layer1002and an electrode1006. However, the arrangement of the pixel group801is not limited to this. For example, a wiring layer may be arranged in addition to the wiring layers506,1001, and1002, a wiring layer including the electrode1004, and a wiring layer including the electrode1006. The arrangements of the capacitive elements702and703are not limited to them, and an electrode may be formed in another wiring layer.

FIG.11shows a modification of the wiring pattern903shown inFIG.9. As described above, the length904aof the pixel102ais longer than the length904bof the pixel102b. To the contrary, in the arrangement shown inFIG.11, an area in the pixel102awhere the wiring pattern903aoverlaps the gate electrode405aof the driving transistor202ais smaller than an area in the pixel102bwhere the wiring pattern903boverlaps the gate electrode405bof the driving transistor202b. To implement this, the width of a portion, extending in the X direction, of the wiring pattern903aof the pixel102amay be smaller than the width of a portion, extending in the X direction, of the wiring pattern903bof the pixel102b.

This can increase the parasitic capacitance of the wiring pattern903bto be almost equal to the parasitic capacitance of the wiring pattern903a. As a result, the gate-source capacitance of the driving transistor202afor holding a voltage corresponding to luminance information is almost equal to that of the driving transistor202b, thereby reducing the difference in electrical characteristic between the pixels102aand102b. Thus, in the arrangement shown inFIG.11as well, it is possible to reduce a luminance unevenness between the pixels102aand102b, thereby suppressing degradation in display image quality.

In the arrangement shown inFIG.11, since the length904ais longer than the length904b, an area where the wiring pattern903aand the gate electrode405aoverlap each other is smaller than an area where the wiring pattern903band the gate electrode405boverlap each other. On the other hand, if the length904ais shorter than the length904b, the area where the wiring pattern903aand the gate electrode405aoverlap each other is made larger than the area where the wiring pattern903band the gate electrode405boverlap each other. In this case, the width of a portion, extending in the X direction, of the wiring pattern903aof the pixel102amay be larger than that of a portion, extending in the X direction, of the wiring pattern903bof the pixel102b.

FIG.12shows another modification of the wiring pattern903shown inFIG.9or11. The portion, extending in the X direction, of the wiring pattern903aof the pixel102aincludes a portion1202aof a length1201aarranged on the side of the pixel102bwith respect to a portion extending in the Y direction. Similarly, the portion, extending in the X direction, of the wiring pattern903bof the pixel102bincludes a portion1202bof a length1201barranged on the side of the pixel102awith respect to a portion extending in the Y direction. As described above, the length904aof the pixel102ais longer than the length904bof the pixel102b. To the contrary, in the arrangement shown inFIG.12, the length1201aof the portion1202ais shorter than the length1201bof the portion1202b.

This can increase the parasitic capacitance of the wiring pattern903bto be almost equal to the parasitic capacitance of the wiring pattern903a. As a result, the gate-source capacitance of the driving transistor202afor holding a voltage corresponding to luminance information is almost equal to that of the driving transistor202b, thereby reducing the difference in electrical characteristic between the pixels102aand102b. Thus, in the arrangement shown inFIG.12as well, it is possible to reduce a luminance unevenness between the pixels102aand102b, thereby suppressing degradation in display image quality.

In the arrangement shown inFIG.12, since the length904ais longer than the length904b, the length1201ais shorter than the length1201b. However, if the length904ais shorter than the length904b, the length1201ais made longer than the length1201b. As shown inFIG.12, the portion1202of the wiring pattern903extends in the X direction. The present invention, however, is not limited to this. The portion1202of the wiring pattern903may be arranged to bend from the X direction to the Y direction, or a portion extending in the Y direction of the wiring pattern903shown inFIG.12may be extended to one or both sides in the Y direction, and may be adjusted in length. For example, the portion extending in the Y direction of the wiring pattern903may protrude rightward inFIG.12from the portion extending in the X direction.

FIG.13shows a modification of the arrangement of the transistors shown inFIG.9. In each pixel group801, the write transistor203aof the pixel102aand the write transistor203bof the pixel102bare arranged between the driving transistor202aof the pixel102aand the driving transistor202bof the pixel102b. Furthermore, the light emission control transistor701aof the pixel102aand the light emission control transistor701bof the pixel102bare arranged between the driving transistor202aof the pixel102aand the driving transistor202bof the pixel102bin the X direction. The source region of the light emission control transistor701aof the pixel102aand the source region of the light emission control transistor701bof the pixel102bshare one diffusion region1301. The write transistors203aand203bof the pixels102aand102band the light emission control transistors701aand701bof the pixels102aand102bare arranged side by side in the Y direction. The write transistors203aand203bof the pixels102aand102band the light emission control transistors701aand701bof the pixels102aand102bmay be reversed, as compared with the arrangement shown inFIG.13.

As shown inFIG.13, the light emission control transistor701aincludes the p-type diffusion region1301, a gate electrode902a, and a p-type diffusion region1302a. Similarly, the light emission control transistor701bincludes the p-type diffusion region1301, a gate electrode902b, and a p-type diffusion region1302b. As shown inFIG.13, the source region of the light emission control transistor701aand the source region of the light emission control transistor701bshare one diffusion region1301connected to the power supply potential Vdd. This can miniaturize the pixels102(pixel groups801), as compared with a case in which the diffusion region forming the source region of the light emission control transistor701aand the diffusion region forming the source region of the light emission control transistor701bare separately arranged in the X direction.

The structure of a light emitting device according to the third embodiment of the present invention will be described with reference toFIGS.14to22. In this embodiment, as compared with the above-described first and second embodiments, a reset transistor is connected between the anode of a light emitting element201and a power supply potential Vss. Components different from the above-described first and second embodiments will mainly be described below.

FIG.14is a view showing an example of the arrangement of a light emitting device101according to this embodiment. As shown inFIG.14, in a pixel array portion103, a scanning line1401is arranged for each pixel row in the Y direction in addition to the above-described first and second embodiments. Each scanning line1401is connected to the output terminal of a corresponding row of a vertical scanning circuit104, and supplies a reset signal to each pixel102.

FIG.15is a circuit diagram showing an example of the arrangement of one pixel102of the light emitting device101shown inFIG.14. As shown inFIG.15, a reset transistor1501is connected between the anode of the light emitting element201(the drain of a driving transistor202) and the power supply potential Vss, in addition to the above-described first and second embodiments. One (a source region in the arrangement shown inFIG.15) of the two main terminals of the reset transistor1501is connected to the anode of the light emitting element201and one (a drain region in the arrangement shown inFIG.15) of the main terminals of the driving transistor202. The other (a drain region in the arrangement shown inFIG.15) of the two main terminals of the reset transistor1501is connected to the power supply potential Vss. The control terminal (gate electrode) of the reset transistor1501is connected to the scanning line1401. When the reset transistor1501is rendered conductive during a non-light emission period, the anode of the light emitting element201is connected to the power supply potential Vss to short-circuit the two terminals of the light emitting element201. This can reset the light emitting element201(sets the light emitting element201in a non-light emission state) (reset operation). By providing the reset transistor1501in the pixel102, the light emitting element201is caused to surely perform black display during the non-light emission period, thereby implementing the light emitting device101with a high contrast ratio.FIGS.14and15show the arrangement in which a light emission control transistor701is arranged. The present invention, however, is not limited to this. For example, the light emission control transistor701need not be arranged.

FIG.16is a circuit diagram showing the connection relationship between two adjacent pixels102. As shown inFIG.16, the plurality of pixels102arranged in the pixel array portion103include pixels102aand102badjacent to each other in the X direction. Similar to the above-described first and second embodiments, the source region of a write transistor203aof the pixel102aand the source region of a write transistor203bof the pixel102bare connected via a signal line107to form one pixel group1601. The pixel102aincludes a reset transistor1501a, in addition to the pixel102aaccording to the first or second embodiment. The pixel102bincludes a reset transistor1501b, in addition to the pixel102baccording to the first or second embodiment.

FIG.17shows an example of the arrangement of the transistors of the circuit shown inFIG.16.FIG.17shows four pixel groups1601each formed by the pixels102aand102b. In each pixel group1601, a write transistor203aof the pixel102aand a write transistor203bof the pixel102bare arranged between a driving transistor202aof the pixel102aand a driving transistor202bof the pixel102b. In addition, a light emission control transistor701aof the pixel102aand the reset transistor1501bof the pixel102bare arranged between the driving transistor202aof the pixel102aand the driving transistor202bof the pixel102bin the X direction. The reset transistor1501aof the pixel102ais arranged on the side, opposite to the pixel102b, of the driving transistor202aof the pixel102a. The light emission control transistor701bof the pixel102bis arranged on the side, opposite to the pixel102a, of the driving transistor202bof the pixel102b. In the arrangement shown inFIG.17, the write transistors203aand203bof the pixels102aand102band the light emission control transistor701aof the pixel102aand the reset transistor1501bof the pixel102bare arranged side by side in the Y direction. The write transistors203aand203bof the pixels102aand102band the light emission control transistor701aof the pixel102aand the reset transistor1501bof the pixel102bmay be reversed, as compared with the arrangement shown inFIG.17.

As shown inFIG.17, the reset transistor1501aincludes a p-type diffusion region406a, a gate electrode1701a, and a p-type diffusion region1702a. The diffusion region1702ais connected to the power supply potential Vss to function as the drain region of the reset transistor1501a. The source region of the reset transistor1501aand the drain region of the driving transistor202ashare one diffusion region406a. This can miniaturize the pixels102(pixel groups1601), as compared with a case in which the diffusion region forming the source region of the reset transistor1501aand the diffusion region forming the drain region of the driving transistor202aare separately arranged in the X direction. Similarly, the reset transistor1501bincludes a p-type diffusion region406b, a gate electrode1701b, and a p-type diffusion region1702b. The diffusion region1702bis connected to the power supply potential Vss to function as the drain region of the reset transistor1501b. The source region of the reset transistor1501band the drain region of the driving transistor202bshare one diffusion region406b.

In this embodiment as well, the source region (diffusion region404a), a gate electrode405a, and the drain region (diffusion region406a) of the driving transistor202aof the pixel102aand the source region (diffusion region404b), a gate electrode405b, and the drain region (diffusion region406b) of the driving transistor202bof the pixel102bare sequentially arranged in the positive X direction. Thus, similar to the above-described first and second embodiments, in the light emitting device101, a difference in electrical characteristic of the driving transistor202between the pixels102can be reduced, thereby suppressing degradation in display image quality. Furthermore, in this embodiment, the source region (diffusion region406a), the gate electrode1701a, and the drain region (diffusion region1702a) of the reset transistor1501aarranged in the pixel102aand the source region (diffusion region406b), the gate electrode1701b, and the drain region (diffusion region1702b) of the reset transistor1501barranged in the pixel102bare sequentially arranged in the positive X direction. Thus, in the light emitting device101, a difference in electrical characteristic of the reset transistor1501between the pixels102can be reduced, thereby suppressing degradation in display image quality. As shown inFIG.17, in the pixel102, the arrangement order of the source region, gate electrode, and drain region of the driving transistor202in the positive X direction may be the same as that of the source region, gate electrode, and drain region of the reset transistor1501. For example, with respect to each of the reset transistors1501aand1501b, the source region, gate electrode, and drain region may be arranged in this order in the negative X direction.

In this embodiment, the reset transistor1501aof the pixel102aand the reset transistor1501bof the pixel102bare arranged so that currents flow in the same direction. However, the present invention is not limited to this, and currents need not flow in the same direction. For example, the reset transistor1501aarranged in the pixel102aand the reset transistor1501barranged in the pixel102bmay be designed so that currents flow in the opposite directions. This is implemented when the driving transistor202causes a current to flow in response to a luminance signal with a voltage corresponding to luminance information while the reset transistor1501resets the light emitting element201. Thus, the control accuracy of the reset transistor1501may be lower than that of the driving transistor202. Therefore, in accordance with the arrangement of the pixels102and the pixel groups1601, the flow direction of a current in each reset transistor1501may be decided appropriately.

In this embodiment as well, if the distance between the gate electrode405of the driving transistor202and a diffusion region403forming the drain region of the write transistor is different between the pixels102aand102b, the shape of a wiring pattern903may be different between the pixels102aand102b, similar to the above-described second embodiment. In the arrangement shown inFIG.17, a length1703ais a length between the gate electrode405aof the driving transistor202aand the contact portion of a diffusion region403aforming the drain region of the write transistor203ain the pixel102a. Similarly, a length1703bis a length between the gate electrode405bof the driving transistor202band the contact portion of a diffusion region403bforming the drain region of the write transistor203bin the pixel102b. A length1704ais the length of a portion where the wiring pattern903aoverlaps the gate electrode405aof the driving transistor202a. Similarly, a length1704bis the length of a portion where the wiring pattern903boverlaps the gate electrode405bof the driving transistor202b.

In the arrangement shown inFIG.17, the length1703aof the pixel102ais shorter than the length1703bof the pixel102b. To the contrary, the length1704aof the pixel102ais longer than the length1704bof the pixel102b. This can increase the parasitic capacitance of the wiring pattern903ato be almost equal to the parasitic capacitance of the wiring pattern903b. As a result, the gate-source capacitance of the driving transistor202afor holding a voltage corresponding to luminance information is almost equal to that of the driving transistor202b, thereby reducing the difference in electrical characteristic between the pixels102aand102b. Thus, in this embodiment as well, it is possible to reduce a luminance unevenness between the pixels102aand102b, thereby suppressing degradation in display image quality.

In the arrangement shown inFIG.17, the length1703ais shorter than the length1703b, and thus the length1704ais shorter than the length1704b. However, if the length1703ais longer than the length1703b, the length1704ais made shorter than the length1704b. As shown inFIG.17, the wiring pattern903is arranged in the X direction on the gate electrode405. However, the wiring pattern903may be arranged to bend from the X direction to the Y direction. Furthermore, as shown inFIG.17, a wiring pattern903amay extend from the gate electrode405aon the side opposite to the pixel102b. In addition, the positions of the write transistors203aand203bare adjusted so that the distance between the gate electrode405of the driving transistor202and the diffusion region403forming the drain region of the write transistor becomes the same between the pixels102aand102b. In this case, the wiring pattern903aand a wiring pattern903bmay have equal lengths and areas. For example, the wiring patterns903aand903bmay have line-symmetric shapes with respect to a line, in the Y direction, which passes through the center of the diffusion region401in the X direction.

FIG.18shows a modification of the wiring pattern903shown inFIG.17. Similar to the above-described arrangement shown inFIG.11, the parasitic capacitance of the wiring pattern903may be adjusted by the area where the wiring pattern903overlaps the gate electrode405of the driving transistor202. In the arrangement shown inFIG.18, the length1703ais shorter than the length1703b, and thus the area where the wiring pattern903aand the gate electrode405aoverlap each other is larger than the area where the wiring pattern903band the gate electrode405boverlap each other. This can increase the parasitic capacitance of the wiring pattern903ato be almost equal to the parasitic capacitance of the wiring pattern903b. At this time, as shown inFIG.18, the parasitic capacitance of the wiring pattern903may be adjusted by differentiating the width of a portion, extending in the X direction, of the wiring pattern903between the pixels102aand102b.

FIG.19shows another modification of the wiring pattern903shown inFIG.17or18. A length1901aindicates the length of a portion1902aarranged on the side of the pixel102bwith respect to a portion extending in the Y direction of a portion, extending in the X direction, of the wiring pattern903a. Similarly, a length1901bindicates the length of a portion1902barranged on the side of the pixel102awith respect to a portion extending in the Y direction of a portion, extending in the X direction, of the wiring pattern903b. At this time, similar to the above-described arrangement shown inFIG.12, the parasitic capacitance of the wiring pattern903may be adjusted by adjusting the lengths1901aand1901b. In the arrangement shown inFIG.19, the length1703ais shorter than the length1703b, and thus the length1901ais longer than the length1901b. This can increase the parasitic capacitance of the wiring pattern903ato be almost equal to the parasitic capacitance of the wiring pattern903b.

FIG.20shows a modification of the arrangement of the transistors shown inFIG.17. In each pixel group1601, the write transistor203aof the pixel102aand the write transistor203bof the pixel102bare arranged between the driving transistor202aof the pixel102aand the driving transistor202bof the pixel102b. Furthermore, the reset transistor1501aof the pixel102aand the reset transistor1501bof the pixel102bare arranged between the driving transistor202aof the pixel102aand the driving transistor202bof the pixel102bin the X direction. The light emission control transistor701aof the pixel102ais arranged between the driving transistor202aof the pixel102aand the write transistor203aof the pixel102a. The light emission control transistor701bof the pixel102bis arranged on the side, opposite to the pixel102a, of the driving transistor202bof the pixel102b. The drain region of the reset transistor1501aof the pixel102aand the drain region of the reset transistor arranged in the pixel102bshare one diffusion region2001connected to the power supply potential Vss. This can miniaturize the pixels102(pixel groups1601), as compared with a case in which the diffusion region forming the drain region of the reset transistor1501aand the diffusion region forming the drain region of the reset transistor1501bare separately arranged in the X direction.

The write transistors203aand203bof the pixels102aand102band the reset transistors1501aand1501bof the pixels102aand102bare arranged side by side in the Y direction. The write transistors203aand203bof the pixels102aand102band the reset transistors1501aand1501bof the pixels102aand102bmay be reversed, as compared with the arrangement shown inFIG.20.

FIG.21is a circuit diagram showing the connection relationship among four adjacent pixels102. The plurality of pixels102further include a pixel102carranged adjacent to the pixel102ain the Y direction and a pixel102darranged adjacent to the pixel102cin the X direction and adjacent to the pixel102bin the Y direction. Similar to each of the above-described embodiments, the source region of the write transistor203aof the pixel102aand the source region of the write transistor203bof the pixel102bare connected via a signal line107ab. The source region of a write transistor203cof the pixel102cand the source region of a write transistor203dof the pixel102dare connected via a signal line107cd. Furthermore, in the pixels102aand102cadjacent to each other in the Y direction, the drain region of the reset transistor1501aof the pixel102aand the drain region of a reset transistor1501cof the pixel102care connected to the same node connected to the power supply potential Vss. Similarly, in the pixels102band102dadjacent to each other in the Y direction, the drain region of the reset transistor1501bof the pixel102band the drain region of a reset transistor1501dof the pixel102dare connected to the same node connected to the power supply potential Vss. The pixels102a,102b,102c, and102dform a pixel group2101.

FIG.22shows an example of the arrangement of the transistors of the circuit shown inFIG.21. As shown inFIG.22, the reset transistor1501aof the pixel102aincludes a p-type diffusion region2201, a gate electrode2202a, and the p-type diffusion region1702a. The reset transistor1501bof the pixel102bincludes the diffusion region2201, a gate electrode2202b, and the p-type diffusion region1702b. The reset transistor1501cof the pixel102cincludes the diffusion region2201, a gate electrode2202c, and a p-type diffusion region1702c. The reset transistor1501dof the pixel102dincludes the diffusion region2201, a gate electrode2202d, and a type diffusion region1702d. That is, the drain regions of the reset transistors1501a,1501b,1501c, and1501dof the pixels102a,102b,102c, and102dshare one diffusion region2201. This can miniaturize the pixels102(pixel groups2101).

The light emitting element201will now be described. The light emitting element201is provided by forming an anode, an organic compound layer, and a cathode on a substrate. A protection layer, a color filter, or the like may be provided on the cathode. If a color filter is provided, a planarizing layer may be provided between the protection layer and the color filter. The planarizing layer can be made of acrylic resin or the like.

In each of the above-described embodiments, a semiconductor substrate of silicon or the like is used as a substrate. However, the present invention is not limited to this, and quartz, glass, a silicon wafer, a resin, a metal, or the like may be used as a substrate. As in each of the above-described embodiments, a switching element such as a transistor and a wiring may be provided on the substrate, and an insulating layer may be provided thereon. The insulating layer may be made of any material as long as a contact hole for ensuring conductivity between the anode of the light emitting element201and the transistor formed on the substrate can be formed and insulation from the unconnected wiring pattern can be ensured. For example, a resin such as polyimide, silicon oxide, silicon nitride, or the like can be used.

A pair of electrodes (the above-described electrodes501and503) can be used as electrodes. The pair of electrodes may be an anode and a cathode. When an electric field is applied in the direction in which the light emitting element201emits light, the electrode having a high potential is the anode, and the other is the cathode. It can also be said that the electrode that supplies holes to the light emitting layer of the light emitting element201is the anode and the electrode that supplies electrons is the cathode.

As the constituent material of the anode, a material having a large work function can be used. For example, a metal such as gold, platinum, silver, copper, nickel, palladium, cobalt, selenium, vanadium, or tungsten, a mixture containing some of them, an alloy obtained by combining some of them, or a metal oxide such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), or zinc indium oxide can be used as the anode. Furthermore, a conductive polymer such as polyaniline, polypyrrole, or polythiophene can also be used as the anode.

One of these electrode materials may be used singly, or two or more of them may be used in combination. The anode may be formed by a single layer or a plurality of layers.

When the anode is used as a reflective electrode, for example, chromium, aluminum, silver, titanium, tungsten, molybdenum, an alloy thereof, a stacked layer thereof, or the like can be used. When the anode is used as a transparent electrode, an oxide transparent conductive layer made of indium tin oxide (ITO), indium zinc oxide, or the like can be used, but the present invention is not limited thereto. A photolithography technique can be used to form the electrode.

On the other hand, as the constituent material of the cathode, a material having a small work function can be used. Examples of the material include an alkali metal such as lithium, an alkaline earth metal such as calcium, a metal such as aluminum, titanium, manganese, silver, lead, or chromium, and a mixture containing some of them. Alternatively, an alloy obtained by combining these metals can also be used. For example, a magnesium-silver alloy, an aluminum-lithium alloy, an aluminum-magnesium alloy, a silver-copper alloy, a zinc-silver alloy, or the like can be used as the cathode. A metal oxide such as indium tin oxide (ITO) can also be used. One of these electrode materials may be used singly, or two or more of them may be used in combination. The cathode may have a single-layer structure or a multilayer structure. For the cathode, silver may be used, or a silver alloy may be used to suppress aggregation of silver. The ratio of the alloy is not limited as long as aggregation of silver can be suppressed. For example, the ratio between silver and a material other than silver may be 1:1.

The cathode may be a top emission element using an oxide conductive layer made of ITO or the like, or may be a bottom emission element using a reflective electrode made of aluminum (Al) or the like, and is not particularly limited. The method of forming the cathode is not particularly limited, but if direct current sputtering or alternating current sputtering is used, the good film coverage is provided and the resistance is easily lowered.

A protection layer may be provided on the cathode. For example, by adhering glass provided with a moisture absorbing agent on the cathode, permeation of water or the like into the light emitting layer such as an organic EL layer can be suppressed and occurrence of display defects can be suppressed. Furthermore, as another embodiment, a passivation film made of silicon nitride or the like may be provided on the cathode to suppress permeation of water or the like into the light emitting layer. For example, after forming the cathode and transferring it to another chamber without breaking the vacuum, a silicon nitride film having a thickness of 2 μm may be formed by a chemical vapor deposition method (CVD method), thereby obtaining the protection layer. The protection layer may be provided using an atomic deposition method (ALD method) after forming a film using the CVD method.

A color filter may be provided on the protection layer. For example, a color filter considering the size of the light emitting element201may be provided on another substrate, and the substrate with the color filter provided thereon may be bonded to the substrate with the light emitting element201provided thereon. Alternatively, a color filter may be patterned on the above-described protection layer using a photolithography technique. The color filter may be formed from a polymeric material.

A planarizing layer may be provided between the color filter and the protection layer. The planarizing layer may be formed from an organic compound, and may be made of a low-molecular material or a polymeric material. For example, the planarizing layer can be formed from a polymeric organic compound.

The planarizing layers may be provided above and below the color filter, and the same or different materials may be used for them. More specifically, examples of the material include polyvinyl carbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, and urea resin.

A counter substrate may be provided on the planarizing layer. The counter substrate is called a counter substrate because it is provided at a position corresponding to the above-described substrate. The constituent material of the counter substrate may be the same as that of the above-described substrate.

The organic layer502(hole injection layer, hole transport layer, electron blocking layer, light emitting layer, hole blocking layer, electron transport layer, electron injection layer, and the like) forming the light emitting element201according to an embodiment of the present invention is formed by the method to be described below. The organic layer502can be formed by a dry process using a vacuum deposition method, an ionization deposition method, a sputtering method, a plasma method, or the like. Instead of the dry process, a wet process that forms a layer by dissolving a solute in an appropriate solvent and using a well-known coating method (for example, a spin coating method, a dipping method, a casting method, an LB method, an inkjet method, or the like) can be used.

Here, when the organic layer502is formed by a vacuum deposition method, a solution coating method, or the like, crystallization or the like hardly occurs and excellent temporal stability is obtained. Furthermore, when the organic layer502is formed using a coating method, it is possible to form the film in combination with a suitable binder resin.

Examples of the binder resin include polyvinyl carbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, and urea resin. However, the binder resin is not limited to them.

One of these binder resins may be used singly as a homopolymer or a copolymer, or two or more of them may be used in combination. Furthermore, additives such as a well-known plasticizer, antioxidant, and an ultraviolet absorber may also be used as needed.

Next, a light emitting device according to this embodiment will be described with reference to the accompanying drawings.FIG.23is a schematic sectional view showing an example, different from those shown inFIGS.5and10described above, of the light emitting device including a light emitting element as an example of the above-described light emitting element201and a TFT element connected to the light emitting element. The TFT element is an example of an active element.

A light emitting device2310shown inFIG.23is provided with a substrate2311of glass, silicon, or the like and an insulating layer2312thereon. An active element such as a TFT2318is arranged on the insulating layer2312, and a gate electrode2313, a gate insulating film2314, and a semiconductor layer2315of the TFT2318are arranged. The TFT2318shown inFIG.23is an example of the above-described driving transistor202. The TFT2318further includes the semiconductor layer2315, a drain electrode2316, and a source electrode2317. An insulating film2319is provided on the TFT2318. The source electrode2317and an anode2321forming the light emitting element are connected via a contact hole2320formed in the insulating film2319.

Note that a method of electrically connecting the electrodes (anode and cathode) included in the light emitting element and the electrodes (source electrode and drain electrode) included in the TFT is not limited to the that shown inFIG.23. That is, one of the anode and cathode and one of the source electrode and drain electrode of the TFT2318are electrically connected. The TFT indicates a thin-film transistor.

In the light emitting device2310shown inFIG.23, an organic layer2322is illustrated as one layer. However, the organic layer2322may include a plurality of layers. Protection layers2324and2325are provided on a cathode2323to suppress the degradation of the light emitting element.

A transistor is used as a switching element in the light emitting device2310shown inFIG.23but may be used as another switching element.

The transistor used in the light emitting device2310shown inFIG.23is not limited to a transistor using a single-crystal silicon wafer, and may be a thin-film transistor including an active layer on an insulating surface of a substrate. Examples of the active layer include single-crystal silicon, amorphous silicon, non-single-crystal silicon such as microcrystalline silicon, and a non-single-crystal oxide semiconductor such as indium zinc oxide and indium gallium zinc oxide. Note that the thin-film transistor is also called a TFT element.

The transistor included in the light emitting device2310shown inFIG.23may be formed in a substrate such as an Si substrate. Here, being formed in a substrate means that a transistor is formed by processing the substrate itself such as an Si substrate. In other words, including a transistor in a substrate can be regarded as integrally forming the substrate and the transistor.

The light emission luminance of the light emitting element according to this embodiment is controlled by the TFT which is an example of a switching element, and the light emitting elements are provided in a plurality of planes to display an image with the light emission luminances of the respective elements. Note that the switching element according to this embodiment is not limited to the TFT, and may be a transistor formed from low-temperature polysilicon or an active matrix driver formed on the substrate such as an Si substrate. The term “on the substrate” may mean “in the substrate”. Whether to provide a transistor in the substrate or use a TFT is selected based on the size of the display unit. For example, if the size is about 0.5 inch, the organic light emitting element may be provided on the Si substrate.

Application examples in which the light emitting device101of each of the above-described embodiments is applied to a display device, a photoelectric conversion device, an electronic device, an illumination device, and a mobile device will be explained below with reference toFIGS.24to29. In addition, the light emitting device101is applicable to the exposure light source of an electrophotographic image forming device, the backlight of a liquid crystal display device, a light emitting device including a color filter in a white light source, and the like. The display device may be an image information processing device that includes an image input unit for inputting image information from an area CCD, a linear CCD, a memory card, or the like, and an information processing unit for processing the input information, and displays the input image on a display unit. In addition, a display unit included in a camera or an inkjet printer may have a touch panel function. The driving type of the touch panel function may be an infrared type, a capacitance type, a resistive film type, or an electromagnetic induction type, and is not particularly limited. The display device may be used for the display unit of a multifunction printer.

FIG.24is a schematic view showing an example of the display device using the light emitting device101according to this embodiment. A display device2400can include a touch panel2403, a display panel2405, a frame2406, a circuit board2407, and a battery2408between an upper cover2401and a lower cover2409. Flexible printed circuits (FPCs)2402and2404are respectively connected to the touch panel2403and the display panel2405. Active elements such as transistors are arranged on the circuit board2407. The battery2408is unnecessary if the display device2400is not a portable device. Even when the display device2400is a portable device, the battery2408need not be provided in this position. The above-described light emitting device101in which the light emitting layer of the organic layer502contains an organic light emitting material such as an organic EL is applicable to the display panel2405. The light emitting device101that functions as the display panel2405operates by being connected to the active elements such as transistors arranged on the circuit board2407.

The display device2400shown inFIG.24may also be used as a display unit of a photoelectric conversion device (imaging device) including an optical unit having a plurality of lenses, and an imaging element for receiving light having passed through the optical unit and photoelectrically converting the light into an electrical signal. The photoelectric conversion device can have a display unit for displaying information acquired by the imaging element. In addition, the display unit can be either a display unit exposed outside the photoelectric conversion device, or a display unit arranged in the finder. The photoelectric conversion device may also be a digital camera or a digital video camera.

FIG.25is a schematic view showing an example of the photoelectric conversion device using the light emitting device101according to this embodiment. A photoelectric conversion device2500can include a viewfinder2501, a rear display2502, an operation unit2503, and a housing2504. The photoelectric conversion device2500can also be referred to as an imaging device. The above-described light emitting device101in which the light emitting layer of the organic layer502contains the organic light emitting material is applicable to the viewfinder2501as a display unit. In this case, the light emitting device101can display not only an image to be captured but also environment information, imaging instructions, and the like. Examples of the environment information are the intensity and direction of external light, the moving velocity of an object, and the possibility that an object is covered with an obstacle.

The timing suitable for imaging is often a very short time, so the information is preferably displayed as soon as possible. Accordingly, the above-described light emitting device101in which the light emitting layer of the organic layer502contains the organic light emitting material can be used as the viewfinder2501. This is so because the organic light emitting material has a high response speed. For the light emitting device101using the organic light emitting material, a display speed is obtained. The light emitting device101is more suitable for these devices than a liquid crystal display device.

The photoelectric conversion device2500includes an optical unit (not shown). This optical unit has a plurality of lenses, and forms an image of light having passed through the optical unit on a photoelectric conversion element (not shown) that is accommodated in the housing2504and receives the light. The focal points of the plurality of lenses can be adjusted by adjusting the relative positions. This operation can also automatically be performed.

The above-described light emitting device101in which the light emitting layer of the organic layer502contains the organic light emitting material may be applied to the display unit of the electronic device. At this time, the light emitting device101can have both a display function and an operation function. Examples of the portable terminal are a portable phone such as a smartphone, a tablet, and a head mounted display.

FIG.26is a schematic view showing an example of the electronic device using the light emitting device101according to this embodiment. An electronic device2600includes a display unit2601, an operation unit2602, and a housing2603. The housing2603can accommodate a circuit, a printed board having this circuit, a battery, and a communication unit. The operation unit2602can be either a button or a touch-panel-type reaction unit. The operation unit2602can also be a biometric authentication unit that performs unlocking or the like by authenticating the fingerprint. A portable device including a communication unit can also be regarded as a communication device. The above-described light emitting device101in which the light emitting layer of the organic layer502contains the organic light emitting material is applicable to the display unit2601.

FIGS.27A and27Bare schematic views showing examples of the display device using the light emitting device101according to this embodiment.FIG.27Ashows a display device such as a television monitor or a PC monitor. A display device2700includes a frame2701and a display unit2702. The above-described light emitting device101in which the light emitting layer of the organic layer502contains the organic light emitting material is applicable to the display unit2702. The display device2700may also include a base2703that supports the frame2701and the display unit2702. The base2703is not limited to the form shown inFIG.27A. For example, the lower side of the frame2701may also function as the base2703. In addition, the frame2701and the display unit2702can be bent. The radius of curvature in this case can be 5,000 (inclusive) to 6,000 (inclusive) mm.

FIG.27Bis a schematic view showing another example of the display device using the light emitting device101according to this embodiment. A display device2710shown inFIG.27Bcan be folded, that is, the display device2710is a so-called foldable display device. The display device2710includes a first display unit2711, a second display unit2712, a housing2713, and a bending point2714. The above-described light emitting device101in which the light emitting layer of the organic layer502contains the organic light emitting material is applicable to each of the first display unit2711and the second display unit2712. The first display unit2711and the second display unit2712can also be one seamless display device. The first display unit2711and the second display unit2712can be divided by the bending point. The first display unit2711and the second display unit2712can display different images, and can also display one image together.

FIG.28is a schematic view showing an example of the illumination device using the light emitting device101according to this embodiment. An illumination device2800can include a housing2801, a light source2802, a circuit board2803, an optical film2804, and a light-diffusing unit2805. The above-described light emitting device101in which the light emitting layer of the organic layer502contains the organic light emitting material is applicable to the light source2802. The optical film2804can be a filter that improves the color rendering of the light source. When performing lighting-up or the like, the light-diffusing unit2805can throw the light of the light source over a broad range by effectively diffusing the light. The illumination device2800can also include a cover on the outermost portion, as needed. The illumination device2800can include both the optical film2804and the light-diffusing unit2805, and can also include only one of them.

The illumination device2800is a device for illuminating the room or the like. The illumination device2800can emit white light, natural white light, or light of any color from blue to red. The illumination device2800can also include a light control circuit for controlling these light components. The illumination device2800can also include a power supply circuit to be connected to the light emitting device101that functions as the light source2802. This power supply circuit can be a circuit for converting an AC voltage into a DC voltage. “White” has a color temperature of 4,200 K, and “natural white” has a color temperature of 5,000 K. The illumination device2800may also have a color filter. In addition, the illumination device2800can have a heat radiation unit. The heat radiation unit radiates the internal heat of the device to the outside of the device, and examples are a metal having a high specific heat and liquid silicon.

FIG.29is a schematic view of an automobile including a taillight as an example of a vehicle lighting appliance using the light emitting device101according to this embodiment. An automobile2900has a taillight2901, and the taillight2901may be turned on when performing a braking operation or the like. The light emitting device101according to this embodiment may be used as a headlight serving as a vehicle lighting appliance. The automobile is an example of a mobile device, and the mobile device may be a ship, a drone, an airplane, a railway vehicle, or the like. The mobile device can include a main body and a lighting appliance installed in the main body. The lighting appliance may also be a device that sends a notification of the current position of the main body.

The above-described light emitting device101in which the light emitting layer of the organic layer502contains the organic light emitting material is applicable to the taillight2901. The taillight2901can have a protection member for protecting the light emitting device101that functions as the taillight2901. The material of the protection member is not limited as long as the material is a transparent material with a strength that is high to some extent, and can be polycarbonate. The protection member can also be formed by mixing a furandicarboxylic acid derivative or an acrylonitrile derivative in polycarbonate.

The automobile2900can include a body2903, and a window2902attached to the body2903. This window can be a window for checking the front and back of the automobile, and can also be a transparent display. The above-described light emitting device101in which the light emitting layer of the organic layer502contains the organic light emitting material can be used as this transparent display. In this case, the constituent materials such as the electrodes of the light emitting device101are formed by transparent members.

Some embodiments of the present invention can provide a technique advantageous in miniaturizing pixels and suppressing degradation in image quality in a light emitting device.

This application claims the benefit of Japanese Patent Application No. 2019-188006, filed Oct. 11, 2019 which is hereby incorporated by reference herein in its entirety.