Light-emitting device, imaging apparatus, electronic apparatus, and movable body

Abstract

To provide a technique advantageous for preventing a reduction in light emission quality involved in a conversion operation of a DA converter in a light-emitting device.SOLUTION: A light-emitting device comprises: a plurality of luminous elements that are arranged to form a plurality of rows and a plurality of columns; a signal output circuit that drives the plurality of luminous elements; and a voltage generation circuit that outputs a pair of voltage signals. The signal output circuit includes a plurality of column circuits that respectively drives the plurality of columns. Each column circuit has a voltage holding circuit that holds a voltage according to the pair of voltage signals supplied from the voltage generation circuit, and a digital-analog converter that converts an input digital signal into an analog signal on the basis of the voltage held by the voltage holding circuit.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] Some light-emitting devices having liquid crystal display elements or organic EL elements include a pixel portion in which pixels are arranged in a matrix and a drive circuit that drives the pixels. There is a drive circuit equipped with a digital interface drive circuit including a digital-to-analog converter (hereinafter referred to as a "DA converter"). Patent Document 1 describes a display device provided with a reference voltage selection type DA converter that controls a switch based on input digital display data to select a reference voltage and converts the digital display data into an analog signal. In the display device of Patent Document 1, a plurality of reference voltage lines for supplying a voltage signal serving as a conversion reference to the DA converter are arranged.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a conversion operation by a plurality of DA converters arranged corresponding to columns of pixels occurs, the potential of the wiring that supplies a voltage signal serving as a conversion reference to the DA converters may fluctuate. Also, switching noise associated with the DA conversion operation may occur. The potential fluctuation and noise may become crosstalk between columns and may cause a factor in deteriorating the light-emitting quality.

[0005] An object of the present invention is to provide a light-emitting device having a circuit that is advantageous for suppressing a deterioration in light-emitting quality associated with the conversion operation of a DA converter in the light-emitting device.

Means for Solving the Problems

[0006] One aspect of the present invention includes a plurality of light-emitting elements arranged to form a plurality of rows and a plurality of columns, a signal output circuit that drives the plurality of light-emitting elements, and a voltage generation circuit that outputs a set of voltage signals. The signal output circuit includes a plurality of column circuits that drive the plurality of columns respectively. Each column circuit includes a voltage holding circuit that holds a voltage corresponding to the set of voltage signals supplied from the voltage generation circuit, and a digital-to-analog converter that converts an input digital signal into an analog signal based on the voltage held by the voltage holding circuit. The present invention relates to a light-emitting device.

Advantages of the Invention

[0007] According to the present disclosure, it is possible to provide a light-emitting device having a circuit that is advantageous for suppressing a decrease in light-emitting quality associated with the conversion operation of a DA converter in the light-emitting device.

Brief Description of the Drawings

[0008]

Figure 1

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Embodiments for Carrying Out the Invention

[0009] 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.

[0010] <First Embodiment> Examples of a light-emitting device according to the present invention will be described with reference to FIGS. 1 to 7. Note that the following embodiments each show an example of the present invention, and numerical values, shapes, materials, components, the arrangement and connection form of the components, etc. do not limit the present invention. In the embodiments described below, as an example of the light-emitting device, a display device that uses image data as an input signal will be mainly described. However, the light-emitting device in each embodiment is not limited to a display device. Examples of using the light-emitting device of this embodiment include a lighting device and a luminaire.

[0011] FIG. 1 is a block diagram showing one form of a light-emitting device according to the present invention. In the pixel array 100, a plurality of pixels 101 are arranged over a plurality of rows and columns (two-dimensionally). Control signals are input to each pixel 101 from the vertical scanning circuit 200 via the scanning lines 210, and luminance signal voltages corresponding to the image signals are input from the signal output circuit 300 via the signal lines 310. The vertical scanning circuit 200 and the signal output circuit 300 are controlled by the control circuit 400 via the control lines 410 and 420. The pixel 101 includes, for example, an organic light-emitting element (organic electroluminescence element, or also referred to as an organic light-emitting element) as a light-emitting element, and emits light with a light emission amount corresponding to the input luminance signal voltage. Here, the pixel is not limited to one including an organic light-emitting element. As long as the light emission of the pixel is controlled according to the input voltage, the pixel may include a light-emitting diode or a liquid crystal element. Further, each pixel 101 may have a plurality of sub-pixels arranged for each color. In this case, the signal lines 310 may be arranged for each column of sub-pixels with reference to each sub-pixel. For example, when one pixel includes three sub-pixels, three signal lines 310 may be arranged in one pixel column.

[0012] The signal output circuit 300 includes a horizontal scanning circuit 301, and a voltage holding circuit 302, a DA converter 303, and a driver circuit 304 arranged over a plurality of columns. In the present embodiment, when the number of columns is n, one voltage holding circuit 302-m (where m is an integer of 1 or more and n or less), one DA converter 303-m, and one column driver circuit 303-m are arranged for each column. The voltage holding circuit 302-m, the DA converter 303-m, and the column driver circuit 303-m are included in a column circuit that processes signals for one column.

[0013] The horizontal scanning circuit 301 scans each column and supplies, to each column, image data corresponding to the luminance signal voltage via the DA converter control line 320. The image data input via the DA converter control signal line 320 is converted into an analog voltage by the voltage holding circuit 302 and the DA converter 303. This analog voltage is input to the driver circuit 304 via the DA converter output line 340. The analog voltage input from the DA converter 303 is output via the column driver circuit 304. The voltage generation circuit 500 generates a set of voltage signals Vref (256 analog voltages when the image data is an 8-bit digital signal) corresponding to the number of the image data, and supplies it to the signal output circuit 300 via the voltage signal line 510. Further, the voltage generation circuit 500 may generate a reference voltage used for variation correction of the signal output circuit 300 and the pixel 101. At this time, the reference voltage for correction may be supplied to the pixel 101 via the column driver circuit 304 and the signal line 310.

[0014] FIG. 2 is an equivalent circuit diagram of the voltage generation circuit 500 according to the present invention, and is a configuration example in which the image data is 8 bits. 256 voltage signals Vref (Vref-1 to Vref-256) are generated by a resistor string composed of resistors R1 to R255 between the reference voltage VT and the reference voltage VB, and are output from the voltage signal line 510. The reference voltage VT and the reference voltage VB may be supplied from outside the light emitting device, or may be generated inside the light emitting device. In the present embodiment, the reference voltage VT and the reference voltage VB generated by a reference voltage generation circuit (not shown) are connected to the resistor string via the buffer circuit 501. One voltage signal Vref is selected according to the image data for each column and output to the column driver 304.

[0015] For comparison with this embodiment, a column circuit of a conventional configuration will be described with reference to FIG. 3. A plurality of voltage signal lines 510 (510-1 to 510-256) are connected to the DA converter 303 without passing through the voltage holding circuit 302 shown in FIG. 1. Image data corresponding to the luminance signal is supplied to a decoder circuit (not shown) in the DA converter 303. The bit values of the image data are supplied to the DA converter via the DA converter control line 320, decoded, and used to control the switch SW. For example, when the image data is an 8-bit digital signal, the decoder controls the switch SW based on the 8-bit digital signal to select a voltage signal Vref corresponding to the image data from among 256 (equivalent to 8 bits) voltage signals.

[0016] At this time, the potential of the voltage signal Vref selected by the switch SW fluctuates transiently due to the potential difference with the DA converter output line 340, the switching noise due to the operation of the switch SW, and the coupling with the DA converter control signal line 320 that controls the switch. In order for the voltage signal Vref from the voltage signal line 510 to settle, a response time based on the time constant determined by the resistance value of the resistor string, the wiring parasitic resistance and wiring parasitic capacitance of the voltage signal line 510, the input parasitic capacitance of the column driver circuit 304, etc. is required. Also, since the voltage signal Vref is shared by a plurality of column DA converters 303, the same voltage signal Vref may be selected in a plurality of columns depending on the image data. If the number of simultaneously selected DA converters 303 is large, the transient potential fluctuation amount associated with the DA conversion operation of the DA converter 303 increases, and the input parasitic capacitance of the driver circuit 304 also increases by the number of columns, so the required settling time increases.

[0017] If the settling time cannot be ensured sufficiently, it may be a factor that prevents an accurate level of light emission operation based on the image data. Also, when there are a plurality of column DA converters 303 that select the same voltage signal Vref, an accurate level of light emission operation cannot be achieved. For example, it may be observed as horizontal stripes or horizontal smear typified by the influence of crosstalk between column circuits. These degrade the quality of the light-emitting image.

[0018] FIG. 4 is an equivalent circuit diagram of the voltage holding circuit 302 and the DA converter 303 for one column of the signal output circuit 300 according to the present embodiment. Compared with FIG. 3, the voltage signal line 510 is connected to the voltage holding circuit 302, and a plurality of voltage signals Vref are supplied to the column DA converter 303 via the holding voltage output line 330. The voltage holding circuit 302 includes a switch SWH controlled by a control signal 420 and a holding capacitor CH. The holding capacitor CH can be configured by a capacitive element such as a MOS capacitor or a MIM capacitor. The switch SWH can control the connection between the voltage generation circuit 500 and the holding capacitor CH, and can connect or disconnect between the voltage generation circuit 500 and the holding capacitor CH.

[0019] FIG. 5 is a diagram for explaining the operation timing of the voltage holding circuit 302 and the column DA converter 303 in FIG. 4, showing the horizontal synchronization signal which is the period of the line scan, the switching of the image data D1 and D2, and the operation timing of the switch SWH and the switch SW. The switch SWH and the switch SW are turned on when the control signal is high and turned off when the control signal is low. Hereinafter, the same applies to other switches. In the operation per line, the switch SW is controlled based on the previous image data D1. After turning off the switch SW, the switch SWH is turned on to connect each holding capacitor CH and each corresponding voltage signal line 510. When the switch SWH is turned off, the voltage signal Vref is held in the holding capacitor CH. As a result, the connection between the holding capacitor CH and the voltage signal line 510 is disconnected and the voltage signal Vref is held in the holding capacitor CH. After holding the voltage signal Vref in the holding capacitor CH, the switch SW is controlled to be turned on according to the timing of the image data D2 in the next line. By this operation, since the voltage signal line 510 and the holding capacitor CH are blocked by the switch SWH, even when the same voltage signal Vref is selected between the column DA converters 303, crosstalk between the column DA converters 303 can be reduced. Also, the parasitic load component connected to the DA converter output line 340 can be reduced as compared with the configuration in FIG. 3. As a result, when the number of pixels increases or for the pattern of the image data, the dependence of the settling time of the transient fluctuation associated with the operation of the column DA converter 303 can be reduced, and the influence on the quality deterioration of the light-emitting image can be reduced. Note that the capacitance value of the capacitive element constituting the holding capacitor CH is set in consideration of the emission period, the settling period, and the allowable time constant as one index.

[0020] FIG. 6 is a diagram for explaining another operation timing of the voltage holding circuit 302 in FIG. 4. Switches SWH-1 and SWH-2 indicate that the switch SWH of the voltage holding circuit 302 is controlled at different timings. For example, the control of the switch SWH is shifted in units of a plurality of columns, such as every even-numbered column and every odd-numbered column, to hold the voltage signal Vref in the holding capacitor CH. Since the switching noise caused by the simultaneous operation of all columns of the switch SWH can be a factor in the transient fluctuation of the voltage signal Vref, the switching noise can be reduced by dispersing the operation timing of the switch SWH. In this example, two examples of different timings are described. The number of different timings may be increased. The number of timings can be determined in consideration of the settling time to the holding capacitor.

[0021] FIG. 7 is a diagram for explaining another control of the voltage holding circuit 302. Although switches SWH are arranged for a plurality of voltage signals Vref connected to each column, for example, the switches SWH are controlled differently for each voltage signal Vref. In FIG. 7, the switches SWH connected to the voltage signal lines 510-1 and 510-2 perform on / off control as in FIGS. 5 and 6, and the switches SWH connected to the voltage signal lines 510-255 and 510-256 are always on. Crosstalk may not be noticeable during specific luminance emission, for example, during high-luminance emission. In FIG. 7, by controlling the switches SWH in the on state for the voltage signal lines 510-255 and 510-256 to which the voltage signal Vref corresponding to a specific luminance is connected, switching noise and power reduction associated with the switching operation can be achieved. Also, a configuration in which the holding capacitor CH and the switch SWH are not arranged in the wiring of a specific voltage signal Vref may be used.

[0022] As described above, in this embodiment, the voltage signal Vref shared by the plurality of column DA converters 303 is held in the holding capacitor CH including the capacitive element provided in the voltage holding circuit 302. Thereafter, based on the image data, the voltage signal Vref input to the driver circuit 304 via the DA converter output line 340 by the column DA converter 303 is selected. With this configuration, crosstalk between the column DA converters 303 via the voltage signal line 510 associated with the operation of the column DA converter 303 can be reduced. Also, since the transient fluctuation amount and the required settling time of the voltage signal Vref can be reduced, the quality of the light-emitting image can be improved without depending on an increase in the number of pixels or the pattern of the image.

[0023] <Second Embodiment> FIG. 8 is an equivalent circuit diagram of the voltage holding circuit 302 and the column DA converter 303 according to the present invention. In this embodiment, a configuration includes a precharge circuit that connects a switch SWPS to the DA converter output line 340 of the column DA converter 303 of the first embodiment and supplies a preset voltage Vps. The description will focus on the differences from the first embodiment.

[0024] In the first embodiment, the voltage signal Vref held in the holding capacitor CH is output to the DA converter output line 340 via the switch SW. The potential V on the DA converter output line 340 after the switch SW is turned on DA is expressed by Equation (1) assuming the capacitance C of the holding capacitor CH cH , the parasitic capacitance Cp on the DA converter output line 340, and the potential Vp held on the DA converter output line 340 before the switch SW is turned on.

[0025] V DA =(C CH xVref + CpxVp) / (C CH + Cp) ··· (1) Here, since the potential Vp is a potential that can change based on image data, the relationship between the potential Vp and the voltage signal Vref may not always be constant. This means that for the change in the voltage signal corresponding to a certain image data, the luminance signal voltage is affected by the potential Vp and fluctuates, which can be a factor causing fluctuations in the emission luminance. FIG. 9 is a diagram for explaining the operation timing of the column DA converter 303 in FIG. 8. The switch SWPS is configured to be controlled by the control signal 420 in the same manner as the switch SWH, but it may also be configured to be controlled by another control signal and timing. When the switch SWH is on and the switch SW is off, the switch SWPS is turned on to supply the preset voltage Vps to the DA converter output line 340. After turning off the switches SWH and SWPS, the switch SW is turned on. This allows the parasitic capacitance Cp to be pre-charged to a predetermined voltage before turning on the switch SW. By the pre-charge, the potential V of the DA converter output line 340 DA becomes as shown in Equation (2).

[0026] V DA =(CHxVref + CpxVps) / (C CH + Cp) ···(2) Since the preset voltage Vps is a constant voltage, it is possible to suppress variations in luminance with respect to changes in the voltage signal corresponding to a certain image data. For example, if the preset voltage Vps is set to the intermediate value of a set of voltage signals, the voltage change when the switch SW is turned on can be averaged.

[0027] As described above, in this embodiment, before the input image data is switched to the next image data, the DA converter output line 340 is set to the preset voltage Vps. By doing so, the voltage signal Vref has a constant relationship with the potential held on the DA converter output line 340 before the switch SW is turned on. As a result, the same effect as in the first embodiment can be obtained, and variations in luminance for each emission corresponding to the image data can be suppressed.

[0028] <Third Embodiment> FIG. 10 is an equivalent circuit diagram of the voltage holding circuit 302 and the column DA converter 303 according to the present embodiment. In the present embodiment, a buffer circuit 305 is arranged with respect to the voltage holding circuit 302 of the first embodiment, and the voltage signal Vref held in the holding capacitor CH is output via the buffer circuit 305. The description will focus on the differences from the first embodiment.

[0029] As described in the second embodiment, the emission luminance may change in response to a change in certain image data depending on the relationship between the voltage signal Vref and the potential Vp held on the DA converter output line 340. This is because the potential of the DA converter output line 340 is determined by the capacitive division between the parasitic capacitor Cp and the holding capacitor CH. In the present embodiment, the voltage signal Vref held in the holding capacitor CH is supplied to the DA converter output line 340 via the buffer circuit 305. As a result, the DA converter output line 340 can become a constant voltage signal Vref based on the image data without depending on the parasitic capacitor Cp and the potential Vp.

[0030] As described above, in the present embodiment, the voltage signal Vref held in the holding capacitor CH is supplied to the DA converter output line 340 via the buffer circuit 305. By passing through the buffer circuit, the same effect as in the first embodiment can be obtained, and good emission with respect to the image data becomes possible.

[0031] <Fourth Embodiment> FIG. 11 is an equivalent circuit diagram of the voltage holding circuit 302 and the two-column DA converters 303-1 and 303-2 according to the present invention. In the present embodiment, with respect to the arrangement of the voltage holding circuit 302 and the column DA converter 303 of the first embodiment, one voltage holding circuit 302 is shared by two column DA converters 303. The description will focus on the differences from the first embodiment.

[0032] In the first embodiment, one voltage holding circuit 302 and one column DA converter 303 are arranged. For the switches SW, SWH, and the holding capacitor CH, the number of voltage signals Vref corresponding to the number of columns and the number of bits of the image data needs to be arranged. Therefore, the ratio of the areas of the voltage holding circuit 302 and the column DA converter 303 in the area of the signal output circuit 300 may increase. Also, for example, when the voltage signal Vref is multi-bit, it is necessary to double the number of switches SW, SWH, and the holding capacitor CH for each additional bit, which may be a factor in increasing the chip size. Or, even when the pixel size is shrunk, it is necessary to shrink the voltage holding circuit 302 and the column DA converter 303 in the horizontal direction, increasing the vertical size of the signal output circuit 300, which may be a factor in increasing the chip size.

[0033] In this embodiment, by sharing the voltage holding circuit 302 with two column DA converters 303-1 and 303-2, the area of the voltage holding circuit 302 in the signal output circuit 300 can be reduced to 1 / 2 compared with the first embodiment. Also, an increase in the chip size can be suppressed compared with the first embodiment for multi-bit conversion of the voltage signal Vref and shrinkage of the pixel size. In this embodiment, a configuration is adopted in which two column DA converters 303 share one voltage holding circuit 302, but a configuration in which three or more column DA converters 303 share the voltage holding circuit 302 may also be used. Also, the arrangement relationship of the shared column DA converters 303 may be a configuration in which sharing is performed at a specific period, such as for every adjacent multiple columns, every even-numbered column, or every odd-numbered column.

[0034] As described in the first embodiment, when the voltage signal Vref is shared by a plurality of column DA converters 303, when the number of column DA converters 303 that select the same voltage signal Vref is large, the transient fluctuation of the voltage signal Vref due to the switch SW becomes large. Similarly, by sharing the voltage holding circuit 302 among a plurality of column DA converters 303, crosstalk occurs between the column DA converters 303, and transient fluctuations of the voltage signal Vref may occur. In the configuration of this embodiment, it is advisable to determine the capacitance value of the capacitive element and the number of column DA converters 303 that share the voltage holding circuit 302 in consideration of the allowable amount of transient fluctuation and the settling time. Alternatively, in terms of the quality of the light-emitting image, the number of column DA converters 303 that share the voltage holding circuit 302 and the arrangement relationship of the shared column DA converters 303 may be determined so that horizontal stripes and horizontal smear cannot be visually recognized.

[0035] As described above, in this embodiment, by sharing one voltage holding circuit 302 among a plurality of column DA converters 303, the same effect as that of the first embodiment can be obtained, and an increase in chip size can be suppressed.

[0036] <Fifth Embodiment> FIG. 12 is an equivalent circuit diagram of the voltage holding circuit 302 and the column DA converter 303 according to the present invention. In this embodiment, with respect to the voltage holding circuit 302 and the column DA converter 303 of the first embodiment, voltage signal lines 510-1, 510-256 are connected to the voltage holding circuit, and a resistor string is arranged in the column DA converter 303. The description will focus on the differences from the first embodiment.

[0037] In the first embodiment, a plurality of voltage signals Vref are generated by the voltage generation circuit 500. In this embodiment, the voltage signals Vref-1, Vref-256 are held in the holding capacitor CH, and two voltage signals input to the DA converter 303 are divided by a resistor string to generate a plurality of voltage signals Vref-2 to Vref-255. The switch SW selected according to the image data input to the decoder is connected to the node of the resistor string where the corresponding voltage signal Vref is generated.

[0038] In the first embodiment, the plurality of voltage signals Vref are supplied to the column DA converters 303 of all columns through the plurality of voltage signal lines 510. As described in the first embodiment, the settling time of the transient fluctuation of the voltage signal Vref is determined by the time constant due to the resistance string in the voltage generation circuit 500, the wiring parasitic resistance of the voltage signal line 510, and the resistance and capacitance components including the wiring parasitic capacitance. Therefore, it is necessary to reduce the resistance value of the resistance string in the voltage generation circuit 500. Similarly, the wiring width of the voltage signal line 510 needs to be increased to reduce the resistance, and the wiring space needs to be widened to reduce the parasitic capacitance, which may increase the chip size. Also, similar to the fourth embodiment, when the voltage signal Vref is made multi-bit, it is necessary to increase the number of wirings of the voltage signal line 510, which may increase the chip size.

[0039] In this embodiment, by arranging a resistance string in the column DA converter 303, the voltage signal line 510 can be composed of two wirings, and the wiring area can be reduced. Also, since the resistance string itself can be made of a high resistance, the resistance element can be made small from the viewpoints of accuracy and allowable current per unit resistance, and even if a resistance string is arranged in each column DA converter 303, an increase in area and power consumption can be suppressed. Note that a configuration in which the resistance strings arranged in the voltage holding circuits 302 and DA converters 303 are shared among a plurality of columns as in the fourth embodiment may also be used. In this case, for example, the number of DA converters 303 to be shared can be determined in consideration of the quality of the light-emitting image and power consumption. Also, similar to the first embodiment, the switches SWH provided in the voltage signal line 510-1 and the voltage signal line 510-2 may be controlled to be on, off, or always on, either one or both.

[0040] FIG. 13 is an equivalent circuit diagram of another voltage holding circuit 302 and column DA converter 303 of this embodiment, and a configuration in which a buffer circuit 305 is arranged in the voltage holding circuit 302 as in the third embodiment may also be used.

[0041] As described above, in this embodiment, a resistor string is arranged in the column DA converter 303, and the voltage supplied from the voltage holding circuit is divided in the column DA converter 303 to generate a plurality of voltage signals Vref. By performing voltage division in the DA converter 303, the number of wirings of the voltage signal line 510 can be reduced. As a result, the same effect as that of the first embodiment can be obtained, and an increase in chip size can be suppressed.

[0042] <Sixth Embodiment> FIG. 14 is an equivalent circuit diagram of the voltage holding circuit 302 and the column DA converter 303 according to the present invention. In this embodiment, with respect to the fifth embodiment, voltage signal lines 510-1, 510-256, and 511 are connected to the voltage holding circuit 302 to supply three different levels of voltages, and switches SWH1 and SWH2 are arranged. Further, a resistor string composed of resistors R1 to 128 is arranged in the column DA converter 303. The description will focus on the differences from the fifth embodiment.

[0043] In the fifth embodiment, the voltage signals Vref-2 to 255 are generated by the voltage signals Vref-1, Vref-256, and the resistor string. In this configuration, when the voltage signal Vref is made multi-bit, the number of resistors and switches SW increases exponentially, and the area of the column DA converter 303 increases.

[0044] In this embodiment, switches SWH1 and SWH2 are controlled in a first mode and a second mode according to image data. Also, the voltage signal line 511 is configured to supply an intermediate potential between the reference voltages VT and VB. In the first mode, switch SWH1 is turned on and switch SWH2 is turned off to generate a voltage signal Vref with the voltage signal line 510-1, the voltage signal line 511, and a resistor string. In the second mode, switch SWH2 is turned on and switch SWH1 is turned off to generate a voltage signal Vref with the voltage signal line 511, the voltage signal line 510-256, and a resistor string. In the configuration of this embodiment, if the number of bits of the voltage signal Vref is the same 8 bits as in the fourth embodiment, the number of resistors in the resistor string can be reduced from 255 to 128, and the number of switches SW can be reduced from 256 to 128, to approximately 1 / 2 of that in the fourth embodiment. Usually, the resistance values of the resistors used in the resistor string are all designed as R. However, in order to maintain the 8-bit monotonic increase property, the resistance value of resistor R128 may be set to 1 / 2·R in the first mode, and the resistance R may be variable such that the resistance of resistor R1 is 1 / 2·R in the second mode. Alternatively, the reference voltage supplied from the voltage signal line 511 may be variable according to the first and second modes. Also, in this embodiment, the control of switches SW, SWH1, and SWH2 is configured such that the control circuit 400 can switch the mode according to the image data and control the horizontal scanning circuit 301.

[0045] In this embodiment, a configuration is adopted in which three voltage signal lines 510-1, 510-256, and 511 are connected to generate a voltage signal Vref with three reference voltages, but a configuration in which a voltage signal Vref is generated with four or more reference voltages may also be used. Also, similar to the third embodiment, a configuration in which a buffer circuit 305 is arranged between the holding capacitor CH and the resistor string may be used.

[0046] As described above, in this embodiment, a voltage signal Vref is generated by combining a resistor string composed of resistors R1 to 128 and three reference voltages, and the number of resistors R and switches SW to be configured can be reduced. Thereby, the same effects as in the first and fifth embodiments can be obtained, and an increase in chip size can be further suppressed compared to the fifth embodiment.

[0047] <Seventh Embodiment> The light-emitting devices described in the above Embodiments 1 to 6 can be used as constituent members of a display device or a lighting device of an apparatus by taking advantage of their light-emitting characteristics. In this embodiment, application examples of the light-emitting device of the present invention will be described. Prior to that, as an example of a light-emitting element, the configuration of an organic light-emitting element will be described in detail.

[0048] The organic light-emitting element that can be used in the light-emitting device of this embodiment will be described. The organic light-emitting element according to this embodiment has a first electrode, a second electrode, and an organic compound layer disposed between these electrodes. One of the first electrode and the second electrode is an anode and the other is a cathode. In the organic light-emitting element of this embodiment, the organic compound layer may be a single layer as long as it has a light-emitting layer, or may be a laminate composed of a plurality of layers. Here, when the organic compound layer is a laminate composed of a plurality of layers, the organic compound layer may have, in addition to the light-emitting layer, a hole injection layer, a hole transport layer, an electron blocking layer, a hole / exciton blocking layer, an electron transport layer, an electron injection layer, and the like. Further, the light-emitting layer may be a single layer or a laminate composed of a plurality of layers. When the light-emitting layer is composed of a plurality of layers, a charge generation layer may be provided between the light-emitting layers. The charge generation layer may be composed of a compound whose LUMO is lower than that of the hole transport layer, and the LUMO of the charge generation layer may be lower than the HOMO of the hole transport layer. Here, the molecular orbital energy of the organic compound layer may be the molecular orbital energy of the organic compound having the largest weight ratio in the organic compound layer.

[0049] Here, HOMO and LUMO are described as "higher" the closer they are to the vacuum level. That the LUMO of the charge generation layer is lower than the HOMO of the hole transport layer means that the LUMO of the charge generation layer is closer to the vacuum level than the HOMO of the hole transport layer.

[0050] In this specification, HOMO and LUMO can be calculated using molecular orbital calculations. The molecular orbital calculations may be performed by the density functional theory (DFT) or the like, and the functional may be B3LYP, and the basis function may be 6-31G* or the like.The molecular orbital calculation can be performed, for example, using Gaussian09 (Gaussian09, Revision C.01, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, O. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, and D. J. Fox, Gaussian, Inc., Wallingford CT, 2010.).

[0051] In this specification, HOMO and LUMO can be calculated using ionization potential and band gap. HOMO can be estimated by measuring the ionization potential. The ionization potential can be measured by dissolving the compound to be measured in a solvent such as toluene and measuring it with a measuring device such as AC-3. The band gap can be measured by dissolving the compound to be measured in a solvent such as toluene and performing a measurement with excitation light applied. The band gap can be measured by measuring the absorption edge of the excitation light. Alternatively, the compound to be measured can be vapor-deposited on a substrate such as glass, and the measurement can be performed by applying excitation light to the vapor-deposited film. The measurement can measure the band gap by measuring the absorption edge of the absorption spectrum absorbed by the vapor-deposited film with the excitation light.

[0052] LUMO can be calculated using the values of the band gap and ionization potential. Subtracting the value of the ionization potential from the band gap can estimate LUMO.

[0053] LUMO can also be estimated from the reduction potential. For example, the one-electron reduction potential is estimated using cyclic voltammetry (CV) measurement. The CV measurement can be performed, for example, in a DMF solution of 0.1 M tetrabutylammonium perchlorate, with a reference electrode of Ag / Ag⁺, a counter electrode of Pt, and a working electrode of glassy carbon. LUMO can be estimated by adding the difference between the reduction potential of the obtained compound and the reduction potential of ferrocene to -4.8 eV.

[0054] In the organic light-emitting element that can be used in the light-emitting device of this embodiment, when an organic compound is included in the light-emitting layer, the light-emitting layer may be a layer composed only of the organic compound or a layer composed of an organometallic complex and other compounds.

[0055] [Configuration of Organic Light-Emitting Element] An organic light-emitting device is provided by forming an insulating layer, a first electrode, an organic compound layer, and a second electrode on a substrate. A protective layer, a color filter, a microlens, etc. may be provided on the cathode. When providing a color filter, a planarization layer may be provided between the protective layer. The planarization layer can be composed of an acrylic resin or the like. The same applies when providing a planarization layer between the color filter and the microlens.

[0056] [Substrate] Examples of the substrate include quartz, glass, silicon wafers, resins, metals, etc. Further, the substrate may be provided with a switching element such as a transistor and wiring thereon, and an insulating layer thereon. As the insulating layer, any material may be used as long as a contact hole can be formed so that wiring can be formed between the insulating layer and the first electrode, and insulation from non-connected wiring can be ensured. For example, resins such as polyimide, silicon oxide, silicon nitride, etc. can be used.

[0057] [Electrode] A pair of electrodes can be used for the electrodes. The pair of electrodes may be an anode and a cathode. When an electric field is applied in the light-emitting direction of the organic light-emitting device, the electrode with the higher potential is the anode and the other is the cathode. Also, it can be said that the electrode that supplies holes to the light-emitting layer is the anode and the electrode that supplies electrons is the cathode.

[0058] As the constituent material of the anode, it is preferable to use a material with as large a work function as possible. For example, single metals such as gold, platinum, silver, copper, nickel, palladium, cobalt, selenium, vanadium, tungsten, etc., and mixtures containing these can be used. Alternatively, alloys combining these, metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide, etc. can be used. Also, conductive polymers such as polyaniline, polypyrrole, polythiophene, etc. can be used.

[0059] These electrode materials may be used alone or in combination of two or more. Also, the anode may be composed of one layer or a plurality of layers.

[0060] When used as a reflective electrode, for example, chromium, aluminum, silver, titanium, tungsten, molybdenum, or alloys thereof, laminated materials, etc. can be used. With the above materials, it is also possible to function as a reflective film without having the role of an electrode. When used as a transparent electrode, oxide transparent conductive layers such as indium tin oxide (ITO) and indium zinc oxide can be used, but it is not limited thereto. For the formation of the electrode, photolithography technology can be used.

[0061] On the other hand, as the constituent material of the cathode, those with a small work function are preferable. For example, alkali metals such as lithium, alkaline earth metals such as calcium, metal elements such as aluminum, titanium, manganese, silver, lead, chromium, or mixtures containing these can be mentioned. Alternatively, alloys combining these metal elements can also be used. For example, magnesium-silver, aluminum-lithium, aluminum-magnesium, silver-copper, zinc-silver, etc. can be used. The use of metal oxides such as indium tin oxide (ITO) is also possible. These electrode materials may be used alone or in combination of two or more. Also, the cathode may have a single-layer structure or a multi-layer structure. Among them, it is preferable to use silver, and in order to reduce the aggregation of silver, it is more preferable to use a silver alloy. As long as the aggregation of silver can be reduced, the ratio of the alloy does not matter. For example, silver: other metals may be 1:1, 3:1, etc.

[0062] The cathode may be a top-emission element using an oxide conductive layer such as ITO, or a bottom-emission element using a reflective electrode such as aluminum (Al), and is not particularly limited. As the formation method of the cathode, although not particularly limited, it is more preferable to use the DC and AC sputtering methods, etc., because the film coverage is good and the resistance is easily reduced.

[0063] [Pixel isolation layer] The pixel isolation layer is formed of a silicon nitride (SiN) film, a silicon oxynitride (SiON) film, or a silicon oxide (SiO) film formed using a chemical vapor deposition (CVD) method. In order to increase the in-plane resistance of the organic compound layer, the film thickness of the organic compound layer, particularly the hole transport layer, is preferably formed thinner on the sidewalls of the pixel isolation layer. Specifically, by increasing the taper angle of the sidewalls of the pixel isolation layer and the film thickness of the pixel isolation layer, and increasing the peeling during evaporation, the film thickness of the sidewalls can be formed thinner.

[0064] On the other hand, it is preferable to adjust the sidewall taper angle and the film thickness of the pixel isolation layer so that voids are not formed in the protective layer formed thereon. Since no voids are formed in the protective layer, the occurrence of defects in the protective layer can be reduced. Since the occurrence of defects in the protective layer is reduced, it is possible to reduce the occurrence of dark spots and the degradation of reliability such as the occurrence of poor conduction of the second electrode.

[0065] In the light-emitting element applicable to this embodiment, even if the taper angle of the sidewalls of the pixel isolation layer is not steep, it is possible to effectively suppress the charge leakage to adjacent pixels. As a result of this study, it was found that if the taper angle is in the range of 60 degrees or more and 90 degrees or less, it can be sufficiently reduced. The film thickness of the pixel isolation layer is desirably 10 nm or more and 150 nm or less. Further, the same effect can be obtained even if it is composed only of a pixel electrode without a pixel isolation layer. However, in this case, it is preferable to make the film thickness of the pixel electrode less than half of the organic layer or to make the end of the pixel electrode a forward taper of less than 60° in order to reduce the short circuit of the organic light-emitting element.

[0066] [Organic compound layer] The organic compound layer may be formed as a single layer or as multiple layers. When there are multiple layers, depending on their functions, they may be referred to as a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer. The organic compound layer is mainly composed of organic compounds, but may also contain inorganic atoms or inorganic compounds. For example, it may have copper, lithium, magnesium, aluminum, iridium, platinum, molybdenum, zinc, etc. The organic compound layer may be disposed between the first electrode and the second electrode and may be arranged in contact with the first electrode and the second electrode.

[0067] When there are multiple light-emitting layers, a charge generation relaxation part may be provided between the first light-emitting layer and the second light-emitting layer. The charge generation part may have an organic compound with a lowest unoccupied molecular orbital energy (LUMO) of -5.0 eV or less. The same applies when there is a charge generation part between the second light-emitting layer and the third light-emitting layer.

[0068] [Protective layer] A protective layer may be provided on the second electrode. For example, by adhering glass provided with a moisture absorbent on the second electrode, the intrusion of water or the like into the organic compound layer can be reduced, and the occurrence of display defects can be reduced. As another embodiment, a passivation film such as silicon nitride may be provided on the cathode to reduce the intrusion of water or the like into the organic compound layer. For example, after forming the cathode, it may be transported to another chamber without breaking the vacuum, and a silicon nitride film with a thickness of 2 μm may be formed by CVD method to serve as a protective layer. A protective layer using atomic layer deposition (ALD method) may be provided after the film formation by CVD method. The material of the film by ALD method is not limited, but may be silicon nitride, silicon oxide, aluminum oxide, etc. Silicon nitride may be further formed by CVD method on the film formed by ALD method. The film by ALD method may have a smaller film thickness than the film formed by CVD method. Specifically, it may be 50% or less, and further 10% or less.

[0069] [Color filter] A color filter may be provided on the protective layer. For example, a color filter considering the size of the organic light-emitting element may be provided on another substrate and bonded to the substrate provided with the organic light-emitting element, or the color filter may be patterned using photolithography technology on the protective layer shown above. The color filter may be composed of a polymer.

[0070] [Planarization layer] A planarization layer may be provided between the color filter and the protective layer. The planarization layer is provided for the purpose of reducing the unevenness of the underlying layer. Without limiting the purpose, it may sometimes be called a material resin layer. The planarization layer may be composed of an organic compound, and may be a low molecule or a polymer, but preferably a polymer.

[0071] The planarization layer may be provided above and below the color filter, and its constituent materials may be the same or different. Specifically, examples include polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicon resin, urea resin, etc.

[0072] [Micro lens] The organic light-emitting device may have an optical member such as a micro lens on its light-emitting side. The micro lens can be composed of an acrylic resin, an epoxy resin, etc. The micro lens may be for the purpose of increasing the amount of light extracted from the organic light-emitting device and controlling the direction of the extracted light. The micro lens may have a hemispherical shape. When having a hemispherical shape, among the tangents in contact with the hemisphere, there is a tangent parallel to the insulating layer, and the contact point between the tangent and the hemisphere is the apex of the micro lens. The apex of the micro lens can be determined similarly in any cross-sectional view. That is, among the tangents in contact with the semi-circle of the micro lens in the cross-sectional view, there is a tangent parallel to the insulating layer, and the contact point between the tangent and the semi-circle is the apex of the micro lens.

[0073] In addition, the midpoint of the microlens can also be defined. In the cross-section of the microlens, a line segment from the point where the arc shape ends to the point where another arc shape ends can be imagined, and the midpoint of this line segment can be called the midpoint of the microlens. The cross-section for discriminating the vertex and the midpoint may be a cross-section perpendicular to the insulating layer.

[0074] The microlens has a first surface with a convex portion and a second surface opposite to the first surface. It is preferable that the second surface is arranged closer to the functional layer side than the first surface. To adopt such a configuration, it is necessary to form a microlens on the light-emitting device. When the functional layer is an organic layer, it is preferable to avoid processes that become high temperature in the manufacturing process. Further, when adopting a configuration in which the second surface is arranged closer to the functional layer side than the first surface, it is preferable that the glass transition temperatures of all the organic compounds constituting the organic layer are 100°C or higher, and more preferably 130°C or higher.

[0075] [Counter substrate] A counter substrate may be provided on the planarization layer. Since the counter substrate is provided at a position corresponding to the aforementioned substrate, it is called a counter substrate. The constituent material of the counter substrate may be the same as that of the aforementioned substrate. When the aforementioned substrate is used as the first substrate, the counter substrate may be the second substrate.

[0076] [Organic layer] The organic compound layers (hole injection layer, hole transport layer, electron blocking layer, light-emitting layer, hole blocking layer, electron transport layer, electron injection layer, etc.) constituting the organic light-emitting element that can be used in the light-emitting device of this embodiment are formed by the following methods.

[0077] For the organic compound layers constituting the organic light-emitting element that can be used in the light-emitting device of this embodiment, dry processes such as vacuum evaporation, ionization evaporation, sputtering, and plasma can be used. Also, instead of the dry process, a wet process in which the layer is formed by dissolving it in an appropriate solvent and using a known coating method (for example, spin coating, dipping, casting method, LB method, inkjet method, etc.) can also be used.

[0078] When a layer is formed by a vacuum evaporation method, a solution coating method, or the like, crystallization or the like hardly occurs and the stability over time is excellent. When forming a film by a coating method, a film can also be formed in combination with an appropriate binder resin.

[0079] Examples of the binder resin include polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, urea resin, etc. However, it is not limited thereto.

[0080] In addition, these binder resins may be used alone as a homopolymer or copolymer, or two or more kinds may be mixed and used. Further, additives such as known plasticizers, antioxidants, and ultraviolet absorbers may be used in combination as necessary. [Pixel Circuit] The light-emitting device may have a pixel circuit connected to the light-emitting element. The pixel circuit may be an active matrix type that independently controls the light emission of the first light-emitting element and the second light-emitting element. The active matrix type circuit may be voltage programming or current programming. The driving circuit has a pixel circuit for each pixel. The pixel circuit may have a light-emitting element, a transistor for controlling the light emission luminance of the light-emitting element, a transistor for controlling the light emission timing, a capacitor for holding the gate voltage of the transistor for controlling the light emission luminance, and a transistor for connecting to GND without passing through the light-emitting element.

[0081] The light-emitting device has a display area and a peripheral area arranged around the display area. The display area has a pixel circuit, and the peripheral area has a display control circuit. The mobility of the transistors constituting the pixel circuit may be smaller than the mobility of the transistors constituting the display control circuit.

[0082] The slope of the current-voltage characteristics of the transistors constituting the pixel circuit may be smaller than the slope of the current-voltage characteristics of the transistors constituting the display control circuit. The slope of the current-voltage characteristics can be measured by the so-called Vg-Ig characteristics.

[0083] The transistor constituting the pixel circuit is a transistor connected to a light-emitting element such as a first light-emitting element.

[0084] [Pixel] The organic light-emitting device has a plurality of pixels. Each pixel has sub-pixels that emit different colors from each other. The sub-pixels may have, for example, emission colors of RGB respectively.

[0085] In the pixel, a region also called a pixel aperture emits light. This region is the same as the first region. The pixel aperture may be 15 μm or less and may be 5 μm or more. More specifically, it may be 11 μm, 9.5 μm, 7.4 μm, 6.4 μm, etc.

[0086] The distance between sub-pixels may be 10 μm or less. Specifically, it may be 8 μm, 7.4 μm, 6.4 μm.

[0087] In a plan view, the pixel can take a known arrangement form. For example, it may be a stripe arrangement, a delta arrangement, a pentile arrangement, or a Bayer arrangement. The shape of the sub-pixel in the plan view may take any known shape. For example, it may be a rectangle, a quadrilateral such as a rhombus, a hexagon, etc. Of course, even if it is not an exact figure but a shape close to a rectangle, it is included in the rectangle. The shape of the sub-pixel and the pixel arrangement can be used in combination.

[0088] [Use of the organic light-emitting element according to an embodiment] The organic light-emitting element according to the embodiment can be used as a component of a display device or a lighting device. In addition, there are applications such as an exposure light source of an electrophotographic image forming device, a backlight of a liquid crystal display device, and a light-emitting device having a color filter for a white light source.

[0089] The display device may be an image information processing device that has an image input unit for inputting image information from an area CCD, a linear CCD, a memory card, etc., has an information processing unit for processing the input information, and displays the input image on a display unit.

[0090] In addition, the display unit included in the imaging device or the inkjet printer may have a touch panel function. The driving method of this touch panel function may be an infrared method, a capacitance method, a resistive film method, or an electromagnetic induction method, and is not particularly limited. Further, the display device may be used for the display unit of the multifunction printer.

[0091] Next, the display device according to the present embodiment will be described with reference to the drawings.

[0092] FIG. 15 is a schematic cross-sectional view showing an example of a display device having an organic light-emitting element and a transistor connected to the organic light-emitting element. The transistor is an example of an active element. The transistor may be a thin film transistor (TFT).

[0093] FIG. 15(a) is an example of a pixel which is a component of the display device according to the present embodiment. The pixel has sub-pixels. The sub-pixels are divided into 10R, 10G, and 10B according to their light emission. The emission color may be distinguished by the wavelength emitted from the light-emitting layer, or the light emitted from the sub-pixel may be selectively transmitted or color-converted by a color filter or the like. Each sub-pixel has a reflective electrode 2 which is a first electrode on the interlayer insulating layer 1, an insulating layer 3 covering the edge of the reflective electrode 2, an organic compound layer 4 covering the first electrode and the insulating layer, a transparent electrode 5, a protective layer 6, and a color filter 7.

[0094] A transistor and a capacitor element may be arranged under or inside the interlayer insulating layer 1. The transistor and the first electrode may be electrically connected via a contact hole or the like (not shown).

[0095] The insulating layer 3 is also called a bank or a pixel isolation film. It covers the edge of the first electrode and is arranged surrounding the first electrode. The portion where the insulating layer is not arranged is in contact with the organic compound layer 4 and becomes a light-emitting region.

[0096] The organic compound layer 4 has a hole injection layer 41, a hole transport layer 42, a first light-emitting layer 43, a second light-emitting layer 44, and an electron transport layer 45.

[0097] The second electrode 5 may be a transparent electrode, a reflective electrode, or a transflective electrode.

[0098] The protective layer 6 reduces the penetration of moisture into the organic compound layer. Although the protective layer is shown as a single layer, it may be a plurality of layers. Each layer may be an inorganic compound layer or an organic compound layer.

[0099] The color filter 7 is divided into 7R, 7G, and 7B according to its color. The color filter may be formed on a planarization film (not shown). Further, it may have a resin protective layer (not shown) on the color filter. Also, the color filter may be formed on the protective layer 6. Or it may be bonded after being provided on a counter substrate such as a glass substrate.

[0100] The display device 10 in FIG. 15(b) describes an organic light-emitting element 26 and a TFT 18 as an example of a transistor. A substrate 11 such as glass or silicon and an insulating layer 12 are provided on the upper part thereof. An active element 18 such as a TFT is arranged on the insulating layer, and a gate electrode 13, a gate insulating film 14, and a semiconductor layer 15 of the active element are arranged. The TFT 18 is further composed of a semiconductor layer 15, a drain electrode 16, and a source electrode 17. An insulating film 19 is provided on the upper part of the TFT 18. The anode 21 constituting the organic light-emitting element 26 and the source electrode 17 are connected through a contact hole 20 provided in the insulating film.

[0101] Note that the electrical connection method between the electrodes (anode, cathode) included in the organic light-emitting element 26 and the electrodes (source electrode, drain electrode) included in the TFT is not limited to the mode shown in FIG. 1(b). That is, any one of the anode or the cathode and any one of the TFT source electrode or the drain electrode may be electrically connected. The TFT refers to a thin-film transistor.

[0102] In the display device 10 of FIG. 15(b), the organic compound layer is illustrated as if it were a single layer, but the organic compound layer 22 may be a plurality of layers. On the cathode 23, a first protective layer 24 and a second protective layer 25 for reducing the deterioration of the organic light-emitting element are provided.

[0103] In the display device 10 of FIG. 15(b), a transistor is used as the switching element, but other switching elements may be used instead.

[0104] Also, the transistor used in the display device 10 of FIG. 15(b) is not limited to a transistor using a single-crystalline silicon wafer, and may be a thin-film transistor having an active layer on an insulating surface of a substrate. Examples of the active layer include non-single-crystalline silicon such as single-crystalline silicon, amorphous silicon, and microcrystalline silicon, and non-single-crystalline oxide semiconductors such as indium zinc oxide and indium gallium zinc oxide. Note that the thin-film transistor is also called a TFT element.

[0105] The transistor included in the display device 10 of FIG. 15(b) may be formed in a substrate such as a Si substrate. Here, forming in the substrate means manufacturing a transistor by processing the substrate itself such as a Si substrate. That is, having a transistor in the substrate can also be regarded as the substrate and the transistor being integrally formed.

[0106] The organic light-emitting element according to this embodiment has its emission luminance controlled by a TFT which is an example of a switching element, and an image can be displayed by the emission luminance of each organic light-emitting element provided in a plurality of planes. Note that the switching element according to this embodiment is not limited to a TFT, and may be a transistor formed of low-temperature polysilicon or an active matrix driver formed on a substrate such as a Si substrate. Forming on the substrate can also mean forming in the substrate. Whether to provide a transistor in the substrate or use a TFT is selected according to the size of the display portion. For example, if the size is about 0.5 inches, it is preferable to provide the organic light-emitting element on the Si substrate.

[0107] (Application Examples of the Light-Emitting Device) Examples of applying the light-emitting devices according to Embodiments 1 to 6 to equipment will be described below. FIG. 16 is a schematic diagram showing an example of a display device that can use the light-emitting devices according to Embodiments 1 to 6. The display device 1000 may include a touch panel 1003, a display panel 1005, a frame 1006, a circuit board 1007, and a battery 1008 between an upper cover 1001 and a lower cover 1009. The touch panel 1003 and the display panel 1005 are connected to flexible printed circuits FPC1002 and 1004. A transistor is printed on the circuit board 1007. The battery 1008 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.

[0108] The display device according to the present embodiment may have a color filter having red, green, and blue. The color filter may have the red, green, and blue arranged in a delta array.

[0109] The display device according to the present embodiment may be used for the 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.

[0110] The display device according to the present embodiment may be used for the display unit of an imaging device having 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 have 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 the viewfinder. The imaging device may be a digital camera or a digital video camera.

[0111] FIG. 17(a) is a schematic diagram showing an example of an imaging device according to the present embodiment. The imaging device 1100 may include a viewfinder 1101, a rear display 1102, an operation unit 1103, and a housing 1104. The viewfinder 1101 may include a 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 shielded by an object, and the like.

[0112] Since the timing suitable for imaging is only a short period of time, it is better to display information as soon as possible. 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 liquid crystal display devices, for which a display speed is required.

[0113] The imaging device 1100 has an optical unit (not shown). The optical unit has a plurality of lenses and forms an image on an image sensor housed in the housing 1104. 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 a photoelectric conversion device. The photoelectric 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.

[0114] FIG. 17(b) is a schematic diagram showing an example of an electronic device according to the present embodiment. The electronic device 1200 includes a display unit 1201, an operation unit 1202, and a housing 1203. The housing 1203 may include a circuit, a printed circuit board having the circuit, a battery, and a communication unit. The operation unit 1202 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 and performs unlocking 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 personal computer.

[0115] FIG. 18 is a schematic diagram showing an example of a display device according to the present embodiment. FIG. 18(a) shows a display device such as a TV monitor or a PC monitor. The display device 1300 has a frame 1301 and a display unit 1302. The light-emitting device according to the present embodiment may be used for the display unit 1302.

[0116] The frame 1301 has a base 1303 that supports the display unit 1302. The base 1303 is not limited to the form shown in FIG. 18(a). The lower side of the frame 1301 may also serve as the base.

[0117] Further, the frame 1301 and the display unit 1302 may be curved. The radius of curvature may be 5000 mm or more and 6000 mm or less.

[0118] FIG. 18(b) is a schematic diagram showing another example of the display device according to the present embodiment. The display device 1310 in FIG. 18(b) is configured to be foldable and is a so-called foldable display device. The display device 1310 includes a first display unit 1311, a second display unit 1312, a housing 1313, and a bending point 1314. The first display unit 1311 and the second display unit 1312 may include a light-emitting device according to the present embodiment. The first display unit 1311 and the second display unit 1312 may be a single seamless display device. The first display unit 1311 and the second display unit 1312 can be separated at the bending point. The first display unit 1311 and the second display unit 1312 may display different images, or may display a single image together with the first and second display units.

[0119] FIG. 19(a) is a schematic diagram showing an example of the lighting device according to the present embodiment. The lighting device 1400 may include a housing 1401, a light source 1402, a circuit board 1403, an optical film 1404, and a light diffusing unit 1405. The light source may include an organic light-emitting element according to the present embodiment. The optical filter may be a filter that improves the color rendering property of the light source. The light diffusing unit 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 unit may be provided on the light-emitting side of the lighting. If necessary, a cover may be provided on the outermost side.

[0120] The lighting device is, for example, a device for lighting an interior. The lighting device may emit any color from white, warm white, or other colors from 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 has a color temperature of 4200K and warm white has a color temperature of 5000K. The lighting device may have a color filter.

[0121] In addition, the lighting device according to the present embodiment may have a heat radiating part. The heat radiating part 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.

[0122] FIG. 19(b) is a schematic diagram of an automobile which is an example of the mobile body according to this embodiment. The automobile has a tail lamp which is an example of a lighting device. The automobile 1500 may have a tail lamp 1501 and may be configured to turn on the tail lamp when a braking operation or the like is performed.

[0123] The tail lamp 1501 may have an organic light-emitting element according to this 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.

[0124] The automobile 1500 may have a vehicle body 1503 and a window 1502 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 this embodiment. In this case, the constituent materials such as the electrodes of the organic light-emitting element are made of transparent members.

[0125] The mobile body according to this embodiment may be a ship, an aircraft, a drone or the like. The mobile body may have a fuselage and a lighting device provided on the fuselage. The lighting device may emit light for indicating the position of the fuselage. The lighting device has an organic light-emitting element according to this embodiment.

[0126] With reference to FIG. 20, application examples of the display device of each of the above embodiments will be described. The display device can be applied to a system wearable as a wearable device such as smart glasses, an HMD, or smart contacts. The imaging display device used in such an application example has an imaging device capable of photoelectrically converting visible light and a display device capable of emitting visible light.

[0127] FIG. 20(a) illustrates glasses 1600 (smart glasses) according to one application example. An imaging device 1602 such as a CMOS sensor or a SPAD is provided on the front surface side of the lens 1601 of the glasses 1600. Also, a display device of each of the above-described embodiments is provided on the back surface side of the lens 1601.

[0128] The glasses 1600 further include a control device 1603. The control device 1603 functions as a power supply that supplies power to the imaging device 1602 and the display device according to each embodiment. Also, the control device 1603 controls the operations of the imaging device 1602 and the display device. An optical system for condensing light onto the imaging device 1602 is formed in the lens 1601.

[0129] FIG. 20(b) illustrates glasses 1610 (smart glasses) according to one application example. The glasses 1610 have a control device 1612. An imaging device corresponding to the imaging device 1602 and a display device are mounted on the control device 1612. An optical system for projecting the light emitted from the display device in the control device 1612 is formed in the lens 1611, and an image is projected onto the lens 1611. The control device 1612 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 to the eyeball of the user who is gazing at the display image. The imaging unit having a light receiving element detects the reflected light of the emitted infrared light from the eyeball, and thus an imaging image of the eyeball is obtained. By having a reducing means for reducing the light from the infrared light emitting unit to the display unit in a plan view, a decrease in image quality is reduced.

[0130] 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.

[0131] 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.

[0132] The display device according to the present embodiment may include an imaging device having a light receiving element, and may control the display image of the display device based on the user's gaze information from the imaging device.

[0133] 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 the control device of the display device, or may be received from 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 viewing area.

[0134] Further, 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 viewing area and the second viewing area may be determined by the control device of the display device, or may be received from 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.

[0135] 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 the 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.

[0136] When performing display control based on visual recognition, it can be preferably applied to smart glasses that further include an imaging device for imaging the outside. The smart glasses can display the captured external information in real time.

[0137] FIG. 21 shows an image forming apparatus according to the present embodiment. FIG. 21(a) is a schematic diagram of an image forming apparatus 36 according to the present embodiment. The image forming apparatus includes a photoreceptor, an exposure light source, a developing unit, a charging unit, a transferrer, a conveyance roller, and a fixing unit.

[0138] Light 29 is irradiated from the exposure light source 28, and an electrostatic latent image is formed on the surface of the photoreceptor 27. This exposure light source has an organic light emitting element according to the present invention. The developing unit 31 has toner and the like. The charging unit 30 charges the photoreceptor. The transferrer 32 transfers the developed image onto the recording medium 34. The conveyance unit 33 conveys the recording medium 34. The recording medium 34 is, for example, paper. The fixing unit 35 fixes the image formed on the recording medium.

[0139] FIGS. 21(b) and 21(c) are schematic diagrams showing a state in which a plurality of light emitting units 38 are arranged on a long substrate in the exposure light source 28. 37 is a direction parallel to the axis of the photoreceptor and represents the column direction in which the organic light emitting elements are arranged. This column direction is the same as the direction of the axis around which the photoreceptor 27 rotates. This direction can also be called the major axis direction of the photoreceptor.

[0140] FIG. 21(b) shows a form in which the light emitting units are arranged along the major axis direction of the photoreceptor. FIG. 21(c) shows a form different from FIG. 21(b), in which the light emitting units are alternately arranged in the column direction in each of the first column and the second column. The first column and the second column are arranged at different positions in the row direction.

[0141] In the first column, a plurality of light emitting units are arranged at intervals. The second column has light emitting units at positions corresponding to the intervals between the light emitting units in the first column. That is, also in the row direction, a plurality of light emitting units are arranged at intervals.

[0142] The arrangement in Fig. 21(c) can be, for example, in a state of being arranged in a grid pattern, in a staggered grid arrangement, or can be rephrased as a checkerboard pattern.

[0143] As described above, by using the device using the organic light-emitting element according to the present embodiment, it is possible to achieve a good image quality and a stable display even for a long-time display.

[0144] (Other Embodiments) The disclosure of this specification includes the following photoelectric conversion devices and equipment. (Item 1) A plurality of light-emitting elements arranged to form a plurality of rows and a plurality of columns, A signal output circuit for driving the plurality of light-emitting elements, A voltage generation circuit for outputting a set of voltage signals, comprising: The signal output circuit includes a plurality of column circuits for driving the plurality of columns respectively, Each column circuit has a voltage holding circuit for holding a voltage corresponding to the set of voltage signals supplied from the voltage generation circuit, and a digital-to-analog converter for converting an input digital signal into an analog signal based on the voltage held by the voltage holding circuit. The voltage holding circuit is connected to the voltage generation circuit, holds a voltage corresponding to the set of voltage signals, then disconnects the connection, and supplies the held voltage to the digital-to-analog converter. A light-emitting device characterized by this.

[0145] (Item 2) The light-emitting device according to Item 1, further comprising a precharge circuit for precharging the output of the digital-to-analog converter to a predetermined voltage before the held voltage is supplied to the digital-to-analog converter.

[0146] (Item 3) The light-emitting device according to Item 1 or 2, wherein the voltage holding circuit holds a voltage corresponding to the set of voltage signals in a plurality of capacitive elements.

[0147] (Item 4) The light-emitting device according to item 3, wherein the set of voltage signals is supplied to the plurality of capacitive elements at different timings.

[0148] (Item 5) The voltage holding circuit is connected to the voltage generation circuit, holds a voltage corresponding to the set of voltage signals, then disconnects the connection, and supplies the held voltage to the digital-to-analog converter. The light-emitting device according to any one of claims 1 to 4.

[0149] (Item 6) The light-emitting device according to any one of items 1 to 5, wherein the set of voltage signals includes a plurality of voltage signals.

[0150] (Item 7) The light-emitting device according to any one of items 1 to 6, wherein the voltage holding circuit is shared by at least two of the plurality of column circuits.

[0151] (Item 8) The light-emitting device according to any one of items 1 to 7, wherein the digital-to-analog converter includes a resistor string that divides the set of voltage signals.

[0152] (Item 9) The light-emitting device according to any one of items 1 to 8, wherein the voltage holding circuit supplies the held voltage to the digital-to-analog converter via a buffer circuit.

[0153] (Item 10) An optoelectronic conversion device having 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 captured by the imaging element, wherein the display unit has the light-emitting device according to any one of items 1 to 9.

[0154] (Item 11) A display unit having the light-emitting device according to any one of Items 1 to 9, a housing provided with the display unit, and a communication unit provided in the housing and communicating with the outside. An electronic device characterized by comprising these components.

[0155] (Item 12) A lighting device characterized by comprising a light source having the light-emitting device according to any one of Items 1 to 9, and a light diffusing portion or an optical film that transmits light emitted by the light source.

[0156] (Item 13) A moving body characterized by comprising a lighting fixture having the light-emitting device according to any one of Items 1 to 9, and a body provided with the lighting fixture.

[0157] 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.

Description of Reference Numerals

[0158] 302: Voltage holding circuit 303: DA converter 320: DA converter control line 330: Holding voltage output line 340: DA converter output signal line 420: Control signal 510-1 to 510-256: Voltage signal lines SW: Switch SWH: Switch CH: Holding capacitor

Claims

1. A plurality of light-emitting elements arranged to form a plurality of rows and a plurality of columns, A signal output circuit for driving the plurality of light-emitting elements, A voltage generation circuit for outputting a set of voltage signals, and comprising: The signal output circuit includes a plurality of column circuits for driving the plurality of columns respectively, Each column circuit has a voltage holding circuit for holding a voltage corresponding to the set of voltage signals supplied from the voltage generation circuit, and a digital-to-analog converter for converting an input digital signal into an analog signal based on the voltage held by the voltage holding circuit. A light-emitting device characterized by that.

2. The light-emitting device according to claim 1, further comprising a precharge circuit for precharging the output of the digital-to-analog converter to a predetermined voltage before the held voltage is supplied to the digital-to-analog converter.

3. The light-emitting device according to claim 1, wherein the voltage holding circuit holds a voltage corresponding to the set of voltage signals in a plurality of capacitive elements.

4. The light-emitting device according to claim 3, wherein the set of voltage signals is supplied to the plurality of capacitive elements at different timings.

5. The light-emitting device according to claim 1, wherein the voltage holding circuit is connected to the voltage generation circuit, holds a voltage corresponding to the set of voltage signals, then disconnects the connection, and supplies the held voltage to the digital-to-analog converter.

6. The light-emitting device according to claim 1, wherein the set of voltage signals includes a plurality of voltage signals.

7. The light-emitting device according to claim 1, wherein the voltage holding circuit is shared by at least two of the plurality of column circuits.

8. The light-emitting device according to claim 1, wherein the digital-to-analog converter includes a resistor string for dividing the set of voltage signals.

9. The light-emitting device according to claim 1, wherein the voltage holding circuit supplies the held voltage to the digital-to-analog converter via a buffer circuit.

10. An optical unit having a plurality of lenses, an imaging element for receiving light that has passed through the optical unit, and a display unit for displaying an image captured by the imaging element, wherein the display unit has the light-emitting device according to any one of claims 1 to 9. A photoelectric conversion device characterized by that.

11. An electronic device comprising: a display unit having the light-emitting device according to any one of claims 1 to 9; a housing provided with the display unit; and a communication unit provided in the housing and communicating with the outside.

12. An illumination device comprising: a light source having the light-emitting device according to any one of claims 1 to 9; and a light diffusing unit or an optical film that transmits light emitted by the light source.

13. A moving body comprising: a lighting fixture having the light-emitting device according to any one of claims 1 to 9; and a body provided with the lighting fixture.

Images