JP5089026B2 - LIGHT EMITTING DEVICE AND ELECTRONIC DEVICE - Google Patents

Description

  The present invention relates to a light emitting device having a light emitting element and means for supplying current to the light emitting element in each of a plurality of pixels.

  One driving method of a light emitting device is a time gray scale method in which a gray scale is displayed by controlling a length of light emission of a pixel in one frame period using a binary voltage of a digital video signal. In general, it can be said that the time gray scale method is more suitable because the electroluminescent material has a higher response speed than liquid crystal. Specifically, when displaying by the time gray scale method, one frame period is divided into a plurality of subframe periods. Then, in accordance with the video signal, the pixels are caused to emit light or not in each subframe period. With the above structure, the total length of a period during which a pixel actually emits light during one frame period can be controlled by a video signal, and gradation can be displayed.

  However, when displaying by the time gray scale method, there is a problem that a pseudo contour is displayed in the pixel portion depending on the frame frequency. Pseudo contour is an unnatural contour line that is often seen when intermediate gray levels are displayed by the time gray scale method, and is mainly caused by fluctuations in perceived luminance caused by human visual characteristics. .

  The pseudo contour includes a moving image pseudo contour generated when a moving image is displayed and a still image pseudo contour generated when a still image is displayed. In a pseudo-contour, a subframe period included in a previous frame period and a subframe period included in a subsequent frame period are visually recognized by human eyes as a continuous frame period. It happens by being done. In other words, a moving image pseudo contour is an unnatural bright line or dark line that is displayed on the pixel portion when the number of gradations different from the number of gradations that should be displayed in the original frame period is recognized by the human eye. Corresponds to a line. The generation mechanism of the still image pseudo contour is the same as that of the moving image pseudo contour. When displaying a still image, a still image pseudo-contour shows that a moving image is displayed on the pixels near the boundary because the human viewpoint slightly moves left and right and up and down at the boundary between regions with different numbers of tones. Occurs by appearing to be. In other words, a still image pseudo-contour corresponds to an unnatural bright line or dark line that appears to move around the boundary by generating a moving picture pseudo-contour at a pixel near the boundary of an area having different gradation levels. .

  In order to prevent the above-described pseudo contour, it is effective to increase the frame frequency or further divide the subframe period into a plurality of parts. Japanese Patent Application Laid-Open No. 2004-228561 describes a technique for dividing a subframe period into a plurality of periods and preventing a period in which pixels emit light or a period in which pixels do not emit light from continuing continuously.

JP 2002-149113 A

  When the subframe period is divided into a plurality of divisions, the generation of pseudo contours can be more reliably suppressed as the number of divisions increases. However, the greater the number of divisions, the shorter the length of the divided subframe period. Similarly, when increasing the frame frequency, it is necessary to shorten the length of each subframe period.

  In the case of an active matrix light-emitting device, a video signal must be input to pixels in all rows in each subframe period or divided subframe period. Therefore, when the length of the subframe period or the divided subframe period is shortened, the next subframe period or the divided subframe period is changed before the video signal is completely input to all the rows of the pixel portion. Will be started. However, a general active matrix light-emitting device usually includes a light-emitting element, a transistor that controls input of a video signal to a pixel (switching transistor), and a transistor that controls a current value supplied to the light-emitting element ( Driving transistor) is provided in each pixel. Therefore, video signals cannot be input in parallel to pixels in two or more rows in the pixel portion.

  Therefore, even when the subframe period or the divided subframe period is shortened, the video signal is completely input to all the rows of the pixel portion before the next subframe period or the divided subframe period is started. Therefore, it is necessary to increase the driving frequency of the driving circuit. However, considering the reliability of the drive circuit, it is not preferable to increase the drive frequency unnecessarily.

  In view of the above-described problems, an object of the present invention is to propose a light-emitting device that can increase the frame frequency and suppress the generation of pseudo contours while suppressing the drive frequency of the drive circuit. Another object of the present invention is to propose a light emitting device that can suppress the generation of pseudo contours by suppressing the driving frequency of the driving circuit, increasing the number of divisions in the subframe period.

  If it is difficult for the inventor to input video signals in parallel to two or more rows of pixels, the inventor can input a plurality of bits of video signals in parallel to one row of pixels, thereby subframe periods or divisions. We thought that it was possible to shorten the length of the subframe period.

  Therefore, in the present invention, a switching transistor and a driving transistor are provided in each pixel according to the number of bits so that a plurality of bits of video signals can be input to the pixel in parallel. When the display is actually performed in the pixel, a transistor (data selection transistor) for selecting the video signal is provided in each pixel so that the video signal of each bit can be selected in the pixel.

  In the light-emitting device of the present invention, the voltage between the gate and the source (gate voltage) is controlled by the light-emitting element, the n switching transistors that control the input of the video signal to the pixel, and the voltage of the input video signal. And a plurality of data selection transistors for controlling the supply of drain current of one of the n driving transistors to the light emitting element.

  Note that the number of data selection transistors may be any number as long as the supply of the drain current of one of the n driving transistors to the light emitting element can be controlled.

  With the above configuration, n-bit video signals can be input to the pixels in parallel. In the present invention, after the video signal is input to the pixel, the video signal is sequentially selected by the data selection transistor, so that the light emitting element can be sequentially turned on or off according to the video signal of each bit. .

  Note that in this specification, a light-emitting element includes an element whose luminance is controlled by current or voltage, specifically, an OLED (Organic Light Emitting Diode) or a FED (Field Emission Display). MIM type electron source elements (electron emitting elements) and the like are included.

  An OLED (Organic Light Emitting Diode), which is one of the light emitting elements, includes a layer (hereinafter referred to as an electroluminescent layer) containing an electroluminescent material from which luminescence generated by applying an electric field is obtained, an anode, And a cathode. The electroluminescent layer is provided between the anode and the cathode, and is composed of a single layer or a plurality of layers. In some cases, these layers contain an inorganic compound. Luminescence in the electroluminescent layer includes light emission (fluorescence) when returning from the singlet excited state to the ground state and light emission (phosphorescence) when returning from the triplet excited state to the ground state.

  In this specification, of the two electrodes of the anode and the cathode, one electrode whose potential can be controlled by the driving transistor is a first electrode, and the other electrode is a second electrode.

  The light-emitting device includes a panel in which the light-emitting element is sealed, and a module in which an IC including a controller or the like is mounted on the panel. Furthermore, the present invention relates to an element substrate corresponding to one mode before the light emitting element is completed in the process of manufacturing the light emitting device.

  Specifically, the element substrate may be in a state where only the first electrode of the light-emitting element is formed, or after the conductive film to be the first electrode is formed and patterned to form the first electrode The state before the electrode is formed may be used, and all forms are applicable.

  Note that as a transistor used in the light-emitting device of the present invention, a polycrystalline semiconductor, a microcrystalline semiconductor (including a semi-amorphous semiconductor), or a thin film transistor using an amorphous semiconductor can be used. It is not limited to a thin film transistor. A transistor formed using single crystal silicon or a transistor using SOI may be used. Further, a transistor using an organic semiconductor or a transistor using carbon nanotubes may be used. In addition, the transistor provided in the pixel of the light-emitting device of the present invention may have a single gate structure, a double gate structure, or a multi-gate structure having more gates.

A semi-amorphous semiconductor is a film containing a semiconductor having an intermediate structure between amorphous and crystalline structures (including single crystal and polycrystal). This semi-amorphous semiconductor is a semiconductor having a third state which is stable in terms of free energy, and is a crystalline one having a short-range order and having a lattice strain, and having a grain size of 0.5 to 20 nm. It can be dispersed in a single crystal semiconductor. The semi-amorphous semiconductor has its Raman spectrum shifted to a lower wavenumber than 520 cm ⁻¹ , and diffraction peaks of (111) and (220), which are considered to be derived from the Si crystal lattice in X-ray diffraction, are observed. . Further, hydrogen or halogen is contained at least 1 atomic% or more as a neutralizing agent for dangling bonds. Here, for convenience, such a semiconductor is referred to as a semi-amorphous semiconductor (SAS). Further, by adding a rare gas element such as helium, argon, krypton, or neon to further promote lattice distortion, stability is improved and a good semi-amorphous semiconductor can be obtained.

  With the above configuration, the present invention can input a plurality of bits of video signals in parallel to each row in the pixel portion, and can sequentially select and display the input plurality of bits of video signals. Therefore, even if the length of the subframe period or the divided subframe period is shorter than the period until the video signal is input to all the rows in the pixel portion, the pixel portion is parallel to two or more rows of pixels. Therefore, it is not necessary to input a video signal, and it is not necessary to forcibly increase the driving frequency of the driving circuit.

  Therefore, in the light emitting device of the present invention, it is possible to increase the frame frequency and suppress the generation of the pseudo contour while suppressing the drive frequency of the drive circuit. In the light-emitting device of the present invention, the number of divisions in the subframe period can be increased while suppressing the drive frequency of the drive circuit, and the occurrence of pseudo contour can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different modes, and those skilled in the art can easily understand that the modes and details can be variously changed without departing from the spirit and scope of the present invention. Is done. Therefore, the present invention is not construed as being limited to the description of this embodiment mode.

  In the light-emitting device of the present invention, the voltage between the gate and the source (gate voltage) is controlled by the light-emitting element, n switching transistors for controlling the input of the video signal to the pixel, and the voltage of the input video signal. N drive transistors, and a plurality of data selection transistors for controlling the supply of drain current of one of the n drive transistors to the light emitting element.

  FIG. 1 is a circuit diagram illustrating one mode of a pixel included in the light-emitting device of the present invention, taking the case of n = 2 as an example. 1 includes a light-emitting element 101, a first switching transistor 102 (1), a second switching transistor 102 (2), a first driving transistor 103 (1), and a second driving transistor. 103 (2), a first data selection transistor 104 (1), a second data selection transistor 104 (2), a first capacitor element 106 (1), and a second capacitor element 106 (2). doing.

  The light-emitting element 101 includes an anode, a cathode, and an electroluminescent layer provided between the anode and the cathode. One of the anode and the cathode is used as the first electrode, and the other is used as the second electrode.

  The gates of the first switching transistor 102 (1) and the second switching transistor 102 (2) are all connected to Gj (j = 1 to y), which is one of the scanning lines G1 to Gy. Has been. One of the source and drain of the first switching transistor 102 (1) is one of the first signal lines S (1) 1 to S (1) x, and S (1) i (i = 1) To x), and the other is connected to the gate of the first driving transistor 103 (1). One of the source and drain of the second switching transistor 102 (2) is one of the second signal lines S (2) 1 to S (2) x. S (2) i (i = 1) To x), and the other is connected to the gate of the second driving transistor 103 (2).

  Further, the first driving transistor 103 (1) and the first data selection transistor 104 (1) have a current supplied from Vi (i = 1 to x) which is one of the power supply lines V1 to Vx, The power source line Vi and the light emitting element 101 are connected so that the drain currents of the first driving transistor 103 (1) and the first data selection transistor 104 (1) are supplied to the light emitting element 101.

  Specifically, in FIG. 1, the source of the first driving transistor 103 (1) is the power supply line Vi, and the drain of the first driving transistor 103 (1) is the first data selection transistor 104 (1). Connected to the source. The drain of the first data selection transistor 104 (1) is connected to the first electrode of the light emitting element 101.

  In addition, the second driving transistor 103 (2) and the second data selection transistor 104 (2) have a current supplied from Vi (i = 1 to x) which is one of the power supply lines V1 to Vx, The power source line Vi and the light emitting element 101 are connected so that the drain currents of the second driving transistor 103 (2) and the second data selection transistor 104 (2) are supplied to the light emitting element 101.

  Specifically, in FIG. 1, the source of the second driving transistor 103 (2) is the power source line Vi, and the drain of the second driving transistor 103 (2) is the second data selection transistor 104 (2). Connected to the source. The drain of the second data selection transistor 104 (2) is connected to the first electrode of the light emitting element 101.

  The gates of the first data selection transistor 104 (1) and the first data selection transistor 104 (2) are connected to a selection line Dj (j = 1 to y) which is one of the selection lines D1 to Dy. Has been.

  Note that the first capacitor 106 (1) and the second capacitor 106 (2) are not necessarily provided. In FIG. 1, one of the two electrodes of the first capacitor 106 (1) is connected to the gate of the first driving transistor 103 (1) and the other is connected to the power supply line Vi. One of two electrodes of the second capacitor 106 (2) is connected to the gate of the second driving transistor 103 (2) and the other is connected to the power supply line Vi.

  When the power supply line Vi and the second electrode of the light emitting element 101 are electrically connected between the power supply line Vi (i = 1 to x) and the second electrode of the light emitting element 101, the light emitting element A voltage is applied to 101 such that a forward bias current is supplied.

  Although FIG. 1 shows an example in which the first driving transistor 103 (1) is connected between the first data selection transistor 104 (1) and the power supply line Vi, the present invention has this configuration. It is not limited to. FIG. 1 shows an example in which the second driving transistor 103 (2) is connected between the second data selection transistor 104 (2) and the power supply line Vi, but the present invention has this configuration. It is not limited to. As shown in FIG. 7, the first data selection transistor 104 (1) may be connected between the first driving transistor 103 (1) and the power supply line Vi. As shown in FIG. 7, the second data selection transistor 104 (2) may be connected between the second driving transistor 103 (2) and the power supply line Vi.

  1 illustrates an example in which a pixel includes a first data selection transistor 104 (1) and a second data selection transistor 104 (2). In FIG. 1, the number of data selection transistors is It is not limited to two. The data selection transistors may be provided in n or more pixels.

  FIG. 1 shows an example in which the first data selection transistor 104 (1) is a p-channel type, and the second data selection transistor 104 (2) is an n-channel type. It is not limited to. As shown in FIG. 1, when the gates of the first data selection transistor 104 (1) and the second data selection transistor 104 (2) are connected to one selection line Dj, the first data selection transistor The polarities of the transistor 104 (1) and the second data selection transistor 104 (2) may be different from each other. Therefore, in FIG. 1, when the first data selection transistor 104 (1) is an n-channel type, the second data selection transistor 104 (2) may be a p-channel type.

  In the present invention, as shown in FIG. 1, the gates of the plurality of data selection transistors are not necessarily connected to one selection line. As shown in FIG. 8, the first selection line D (1) j, where the gate of the first data selection transistor 104 (1) and the gate of the second data selection transistor 104 (2) are different from each other, When connected to the second selection line D (2) j, the first data selection transistor 104 (1) and the second data selection transistor 104 (2) have the same polarity. Either may be different.

  Further, FIG. 1 illustrates the case where the first switching transistor 102 (1) and the second switching transistor 102 (2) are all n-channel type, but the present invention is not limited to this structure. . The first switching transistor 102 (1) and the second switching transistor 102 (2) may have the same polarity. Therefore, the first switching transistor 102 (1) and the second switching transistor 102 (2) may all be p-channel type. However, when the gates of the plurality of switching transistors included in the pixel are connected to different scanning lines, the polarity of all the switching transistors may not be the same.

  1 illustrates the case where the first driving transistor 103 (1) and the second driving transistor 103 (2) are p-channel transistors, the present invention is not limited to this structure. The first driving transistor 103 (1) and the second driving transistor 103 (2) may be an n-channel type. Note that in the case where the first driver transistor 103 (1) and the second driver transistor 103 (2) are p-channel transistors, the first electrode included in the light-emitting element 101 is an anode, and the second electrode is a cathode. Some are desirable. On the other hand, when the first driver transistor 103 (1) and the second driver transistor 103 (2) are n-channel transistors, the first electrode included in the light-emitting element 101 is a cathode, and the second electrode is The anode is desirable.

  Next, the operation of the pixel shown in FIG. 1 will be described. The light emitting device of the present invention operates by dividing one frame period into a plurality of subframe periods. In addition, the light emitting device of the present invention may operate by dividing one subframe period into a plurality of parts. When attention is paid to n consecutive subframe periods or divided subframe periods, the operation of the pixel can be described by being divided into a writing period and a holding period.

  FIG. 2A illustrates the operation of the pixel in the writing period. 2 and 3, in order to make the operation of the pixel easy to understand, the first switching transistor 102 (1), the second switching transistor 102 (2), and the first data selection transistor are used. 104 (1) and the second data selection transistor 104 (2) are simply shown as switches.

  In the writing period, the scanning lines G1 to Gy are selected in order. When the scanning line Gj is selected, all of the first switching transistor 102 (1) and the second switching transistor 102 (2) whose gates are connected to the scanning line Gj (j = 1 to y) Turn on. Then, the video signal input to the first signal line S (1) i (i = 1 to x) is turned on by the first switching transistor 102 (1), so that the first driving transistor is turned on. 103 (1). In addition, the video signal input to the second signal line S (2) i (i = 1 to x) is turned on by the second switching transistor 102 (2), so that the second driving transistor 103 (2).

  In the present invention, the video signal input to the first signal line S (1) i and the video signal input to the second signal line S (2) i can be set to different bits. In FIG. 2A, for example, a k-bit video signal is input to the first signal line S (1) i, and a t-bit video signal is input to the second signal line S (2) i. Assume that

  In the writing period, a signal that turns on only one of the plurality of data selection transistors is sequentially input to the selection lines D1 to Dy. Specifically, in FIG. 2A, the first data selection transistor 104 (1) is turned on by a signal input to the selection line Dj (j = 1 to y), and the second data selection transistor is turned on. 104 (2) is turned off.

  When the first driving transistor 103 (1) is turned on in accordance with the voltage of the video signal of the k-th bit, the power line Vi and the first electrode of the light-emitting element 101 are electrically connected, so that light emission A forward bias current is supplied to the element 101. The current supplied to the light-emitting element 101 is determined by the drain current of the first driving transistor 103 (1) and the voltage-current characteristics of the light-emitting element 101. Then, the light emitting element 101 emits light with a luminance with a height corresponding to the supplied current. On the other hand, when the first driving transistor 103 (1) is turned off in accordance with the voltage of the video signal of the k-th bit, the supply of current to the light-emitting element 101 is stopped and the light-emitting element 101 enters a non-light-emitting state.

  When the writing period ends, the holding period starts next. During the n subframe periods or divided subframe periods, n holding periods are provided. Therefore, when n = 2, the first holding period and the second holding period appear. FIG. 2B shows operation of the pixel in the first holding period.

  In all the holding periods, the selection of the scanning line Gj (j = 1 to y) is completed, and the first switching transistor 102 (1) and the second switching transistor 102 (2) are all turned off. The voltage of the video signal input to the pixel in the writing period is held by the first capacitor element 106 (1) and the second capacitor element 106 (2) in the holding period.

  In the first holding period, the first data selection transistor 104 (1) is turned on by the signal input to the selection line Dj (j = 1 to y), and the second data selection transistor 104 (2). Remains off. Therefore, when the first driver transistor 103 (1) is on in the writing period, the light-emitting element 101 emits light because the first driver transistor 103 (1) remains on in the first holding period. Maintain the state. On the other hand, when the first driving transistor 103 (1) is off in the writing period, the first driving transistor 103 (1) remains off in the first holding period, so that the light-emitting element 101 has The non-light emitting state is maintained.

  FIG. 3 shows the operation of the pixel in the second holding period. In the second holding period, only one data selection transistor different from that in the first holding period is turned on by a signal input to the selection line Dj (j = 1 to y). Specifically, in FIG. 3, the first data selection transistor 104 (1) is turned off and the second data selection transistor 104 (2) is turned on.

  When the second driving transistor 103 (2) is turned on in accordance with the voltage of the video signal of the s-th bit, the power supply line Vi and the first electrode of the light emitting element 101 are electrically connected. Therefore, a forward bias current is supplied to the light emitting element 101. The current supplied to the light-emitting element 101 is determined by the drain current of the second driving transistor 103 (2) and the voltage-current characteristics of the light-emitting element 101. Then, the light emitting element 101 emits light with a luminance with a height corresponding to the supplied current. On the other hand, when the second driving transistor 103 (2) is turned off in accordance with the voltage of the video signal of the s bit, the supply of current to the light emitting element 101 is stopped and the light emitting element 101 is in a non-light emitting state. Become.

  With the above-described series of operations, n subframe periods or divided subframe periods can appear continuously. Specifically, in FIGS. 2 and 3, the writing period and the first holding period correspond to a subframe period corresponding to a k-bit video signal or a divided subframe period. The second holding period corresponds to a subframe period corresponding to an s-bit video signal or a divided subframe period.

  When all the subframe periods or divided subframe periods within one frame period appear, an image having a gradation can be displayed. The number of gradations can be determined by controlling the total time of the subframe period in which the light emitting element emits light or the divided subframe period within one frame period.

  In the above operation, the light emission of the light emitting element 101 is controlled according to the video signal, but the present invention is not limited to this configuration. For example, a non-display period may be provided in which the supply of current to the light emitting elements 101 is stopped regardless of the video signal, and all the light emitting elements 101 are forcibly brought into a non-light emitting state.

  In the non-display period, a signal for forcibly turning off the driving transistor is input to the signal line instead of the video signal in the writing period, and the light-emitting element is forcibly set in the non-light-emitting state in the corresponding holding period. It ’s fine. Specifically, in the non-display period, a signal (blank) that turns off the first driving transistor 103 (1) or the second driving transistor 103 (2) is supplied to the first signal line in the writing period. The signal is input to S (1) i or the second signal line S (2) i. With the above structure, the light-emitting element 101 can be forcibly brought into a non-light-emitting state in the first holding period or the second holding period.

  Note that the non-display period is not necessarily provided. However, if the total length of n subframe periods or divided subframe periods that appear in order is shorter than the period until video signals are input to all rows of the pixel portion, the non-display period is It is necessary to provide it. By providing the non-display period, it is not necessary to input a video signal in parallel to two or more rows of pixels in the pixel portion.

  Conventionally, it is necessary to provide a non-display period when the length of each subframe period or divided subframe period is shorter than the period until video signals are input to all rows of the pixel portion. It was. Therefore, even if the drive frequency is the same, it can be said that the total length of the non-display period that appears in one frame period can be reduced as much as possible in the present invention, compared to the conventional case. Accordingly, since the duty ratio can be increased, the contrast of the image displayed on the pixel portion can be increased.

FIG. 4 shows a timing chart in the case of displaying 6-bit gradation using the pixel shown in FIG. In FIG. 4, the horizontal axis indicates the length of a subframe period that appears in one frame period or divided subframe periods (SF _{1 to} SF ₆ ), and the vertical axis indicates the scanning line selection order. . When displaying 64 gradations with a 6-bit video signal, at least six subframe periods are required. When the number of gradations is changed linearly, the ratio of the lengths of the _six subframe periods (SF _{1 to} SF ₆ ) is 2 ⁵ : 2 ⁴ : 2 ³ : 2 ² : 2 ¹ : 2 ⁰ . .

In FIG. 4, divides a subframe periods SF ₁ to 4, divided into three subframe periods SF _2, it shows an example of dividing the sub-frame period SF ₃ into two. However, the present invention is not limited to this configuration, and it is not always necessary to divide the subframe period, and even in the case of division, the number of divisions is not limited to FIG.

  FIG. 4 shows a timing chart of signals input to the scanning line G1 and the selection line D1 in each subframe period. FIG. 4 also shows timings of signals input to the first signal line S (1) 1 and the second signal line S (2) 1.

In FIG. 4, first, in order to input the first and second bits of the 6-bit video signal from the pixels in the first row, one of the divided subframe periods SF ₁ is divided into the divided subframe periods SF _1. one of the frame period SF ₂ but appear in the order. Next, since the first and second bit video signals are input again from the pixels in the first row, one of the divided subframe periods SF ₁ and one of the divided subframe periods SF ₂ appear in order. . Next, since the first and second bit video signals are input again from the pixels in the first row, one of the divided subframe periods SF ₁ and one of the divided subframe periods SF ₂ appear in order. . Next, in order to enter the first bit and the third bit of the video signal from the first row of pixels, one of the divided sub-frame periods SF _1, one of the sub-frame period SF ₃ divided but appear in sequence. Next, since a video signal of 4 bits and a blank signal (blank) for forcibly turning off the light emitting element from a pixel in the first row are input, a subframe period SF ₄ , a non-display period (BL) appears in order. Then the video signal of the third bit, the blank signal for the state of forcing non-emitting light-emitting element (blank), for inputting from the first row of pixels, divided sub-frame period SF ₃ One non-display period (BL) appears in order. Next, since a video signal of 5 bits and a blank signal (blank) for forcibly setting the light emitting element to a non-light emitting state are input from the pixels in the first row, the subframe period SF ₅ , the non-display period (BL) appears in order. Next, since a 6-bit video signal and a blank signal (blank) for forcibly turning off the light emitting element are input from the pixels in the first row, the subframe period SF ₆ , the non-display period (BL) appears in order.

  Note that FIG. 4 illustrates the operation of the pixel illustrated in FIG. 1, but the pixel of the present invention is not limited to n = 2. Depending on the value of n to be set, the total length of the non-display period occupying one frame period can be shortened as much as possible, and finally can be set to zero.

  FIG. 5 is a circuit diagram illustrating one mode of a pixel included in the light-emitting device of the present invention when n is generalized. 5 includes a light-emitting element 201, first to n-th switching transistors 202 (1) to 202 (n), first to n-th driving transistors 203 (1) to 203 (n), The first to nth data selection transistors 204 (1) to 204 (n) and the first to nth capacitor elements 206 (1) to 206 (n) are included.

  The light-emitting element 201 includes an anode, a cathode, and an electroluminescent layer provided between the anode and the cathode. One of the anode and the cathode is used as the first electrode, and the other is used as the second electrode.

  The gates of the first to nth switching transistors 202 (1) to 202 (n) are all connected to the scanning line Gj (j = 1 to y). In the first to n-th switching transistors 202 (1) to 202 (n), any one of a source and a drain has a first signal line S (1) i to an n-th signal line S (n) i. (I = 1 to x) are connected to each other, and the other is connected to the gates of the first to nth driving transistors 203 (1) to 203 (n).

  The first to nth driving transistors 203 (1) to 203 (n) and the first to nth data selection transistors 204 (1) to 204 (n) are in pairs. That is, the first driving transistor 203 (1) and the first data selection transistor 204 (1), the second driving transistor 203 (2) and the second data selection transistor 204 (2),. . . The n-th driving transistor 203 (n) and the n-th data selection transistor 204 (n) are in pairs. The currents supplied from the power supply lines Vi (i = 1 to x) are paired such that the currents are supplied to the light emitting element 201 as the drain currents of the paired driving transistor and data selection transistor. The driving transistor and the data selection transistor are connected to the power supply line Vi and the light emitting element 201.

  The gates of the first to nth data selection transistors 204 (1) to 204 (n) are connected to the first selection lines D (1) j to D (n) j (j = 1 to y), respectively. Has been.

  Note that the first to nth capacitor elements 206 (1) to 206 (n) are not necessarily provided. In FIG. 5, one of the two electrodes included in each of the first to nth capacitor elements 206 (1) to 206 (n) is the first to nth driving transistors 203 (1) to 203 (n). The other is connected to the gate and the power supply line Vi.

  5 illustrates an example in which a pixel includes first to nth data selection transistors 204 (1) to 204 (n). However, in FIG. 5, the number of data selection transistors is limited to n. Not. The data selection transistors may be provided in n or more pixels. FIG. 5 shows an example in which the first to nth data selection transistors 204 (1) to 204 (n) are all p-channel type, but the present invention is not limited to this configuration. The first to nth data selection transistors 204 (1) to 204 (n) may all be n-type. Further, as shown in FIG. 5, when the gates of a plurality of data selection transistors are connected to different selection lines, the polarity of all the data selection transistors may be the same or different.

  5 illustrates the case where all of the first to n-th switching transistors 202 (1) to 202 (n) are n-channel types, the present invention is not limited to this configuration. The first to n-th switching transistors 202 (1) to 202 (n) may have the same polarity. Therefore, all of the first to n-th switching transistors 202 (1) to 202 (n) may be p-channel type. However, when the gates of the plurality of switching transistors included in the pixel are connected to different scanning lines, the polarity of all the switching transistors may not be the same.

  5 illustrates the case where the first to nth driving transistors 203 (1) to 203 (n) are p-channel transistors, the present invention is not limited to this structure. The first to nth driving transistors 203 (1) to 203 (n) may be n-channel type. However, in the case where the first to n-th driving transistors 203 (1) to 203 (n) are p-channel transistors, the first electrode included in the light-emitting element 201 is an anode, and the second electrode is a cathode. desirable. On the other hand, when the first to n-th driving transistors 203 (1) to 203 (n) are n-channel transistors, the first electrode of the light-emitting element 201 is a cathode and the second electrode is an anode. Is preferable.

FIG. 6 shows a timing chart in the case where n = 6 is assumed in the pixel shown in FIG. 5 and 6-bit gradation is displayed. In FIG. 6, the horizontal axis indicates the length of subframe periods (SF _{1 to} SF ₆ ) that appear in one frame period, and the vertical axis indicates the selection order of scanning lines. When displaying 64 gradations with a 6-bit video signal, at least six subframe periods are required. When the number of gradations is changed linearly, the ratio of the lengths of the _six subframe periods (SF _{1 to} SF ₆ ) is 2 ⁵ : 2 ⁴ : 2 ³ : 2 ² : 2 ¹ : 2 ⁰ . .

  FIG. 6 shows a timing chart of signals input to the scanning line G1 and the first to sixth selection lines D (1) 1 to D (6) 1 in each subframe period. In addition, timings of signals input to the first to sixth signal lines S (1) 1 to S (6) 1 are also shown in FIG.

In FIG. 6, first, all 6-bit video signals are input from the pixels in the first row in the writing period. Therefore, after one writing period, the subframe periods SF _{1 to} SF ₆ can appear successively in sequence.

  As shown in FIG. 6, when all the bits are input to the pixel in one writing period, display can be performed without providing a non-display period. Accordingly, since the duty ratio can be increased, the contrast of the image displayed on the pixel portion can be increased.

  Note that FIG. 6 shows a timing chart in the case of displaying 6-bit gradation using six subframe periods, but the present invention is not limited to this configuration. The display may be performed by dividing a subframe period having a long period into a plurality of times, and increasing the total number of subframe periods and divided subframe periods to more than six.

  In this embodiment mode, the power supply line Vi and the second electrode of the light emitting element 101 are electrically connected between the power supply line Vi and the second electrode of the light emitting element 101 even in the writing period. Although a voltage that can supply a forward bias current is applied to the light emitting element 101, the present invention is not limited to this configuration. The supply of current to the light-emitting element 101 may be stopped until the writing period ends in all rows. Specifically, the potential difference between the second electrode of the light-emitting element 101 and the power supply line Vi may be close to 0. Alternatively, when the light emitting element 101 is regarded as a diode, a potential difference between the second electrode and the power supply line Vi is set so that a reverse bias voltage is applied between the pair of electrodes included in the light emitting element 101. good. Alternatively, the path of the current flowing through the light emitting element 101 may be blocked by a switch or the like.

FIG. 16 shows a timing chart in the case of displaying 6-bit gradations assuming that n = 6 in the pixel shown in FIG. However, in FIG. 16, supply of current to the light-emitting element 101 is stopped until the writing period ends in all rows. In FIG. 16, the horizontal axis indicates the length of subframe periods (SF _{1 to} SF ₆ ) appearing in one frame period, and the vertical axis indicates the selection order of scanning lines.

  In the driving method illustrated in FIG. 16, pixels in all rows can be displayed simultaneously in each subframe period.

  Note that FIG. 16 shows a timing chart in the case of displaying 6-bit gradation using six subframe periods, but the present invention is not limited to this configuration. The display may be performed by dividing a subframe period having a long period into a plurality of times, and increasing the total number of subframe periods and divided subframe periods to more than six.

  In this example, a layout of a pixel included in the light-emitting device of the present invention is described. However, in this embodiment, the case where the first capacitor element 106 (1) and the second capacitor element 106 (2) are not provided in FIG. 1 is described as an example.

  FIG. 9 shows a top view of the pixel shown in FIG. 1 as an example. In FIG. 9, part of the scan line Gj functions as a gate 903 included in the first switching transistor 102 (1) and a gate 904 included in the second switching transistor 102 (2).

  In FIG. 9, the first driving transistor 103 (1) and the first data selection transistor 104 (1) share the active layer 905. In FIG. 9, the second driving transistor 103 (2) and the second data selection transistor 104 (2) share the active layer 906.

  In FIG. 9, part of the selection line Dj functions as a gate 907 included in the first data selection transistor 104 (1) and a gate 908 included in the second data selection transistor 104 (2).

  Note that FIG. 9 illustrates only the first electrode 901 and a region 902 where the first electrode 901 actually overlaps the electroluminescent layer and the second electrode in the light-emitting element 101.

  In this embodiment, a driver circuit used in the light emitting device of the present invention will be described. FIG. 10 shows a block diagram of the light emitting device of this embodiment. The light-emitting device illustrated in FIG. 10 includes a pixel portion 1111 having a plurality of pixels each including a light-emitting element, a scanning line driver circuit 1112 that selects each pixel, and a signal line driver that controls input of a video signal to the selected pixel. A circuit 1113 and a selection line driver circuit 1120 for controlling the potential of the selection line are included.

  In FIG. 10, the signal line driver circuit 1113 includes a shift register 1114, a latch A 1115, and a latch B 1116. A clock signal (SCLK), a start pulse signal (SSP), and a switching signal (L / R) are input to the shift register 1114. When the clock signal (SCLK) and the start pulse signal (SSP) are input, a timing signal is generated in the shift register 1114. Further, the order of appearance of the pulses of the timing signal is switched by the switching signal (L / R). The generated timing signals are sequentially input to the first-stage latch A1115. When a timing signal is input to the latch A 1115, video signals are sequentially written and held in the latch A 1115 in synchronization with the pulse of the timing signal. In this embodiment, video signals are sequentially written in the latch A 1115, but the present invention is not limited to this configuration. A plurality of stages of latches A1115 may be divided into several groups, and so-called divided driving may be performed in which video signals are input in parallel for each group. Note that the number of groups at this time is called the number of divisions. For example, when the latches are divided into groups every four stages, it can be said that the driving is divided into four.

  The time until video signal writing to all the latches of the latch A 1115 is completed is called a row selection period. Actually, the row selection period may include a period in which a horizontal blanking period is added to the row selection period.

  When the one row selection period ends, a latch signal (Latch Signal) is supplied to the second-stage latch B 1116, and the video signal held in the latch A 1115 is simultaneously written to the latch B 1116 in synchronization with the latch signal. , Retained. In the latch A 1115 that has finished sending the video signal to the latch B 1116, the next video signal is sequentially written again in synchronization with the timing signal from the shift register 1114. During this second row selection period, the video signal written and held in the latch B 1116 is input to the pixel portion 1111.

  Instead of the shift register 1114, another circuit capable of selecting a signal line such as a decoder may be used.

  Next, the configuration of the scan line driver circuit 1112 is described. The scan line driver circuit 1112 includes a shift register 1119 and a buffer 1118. In some cases, a level shifter may be provided. In the scan line driver circuit 1112, a clock (GCLK) and a start pulse signal (G1SP) are input to the shift register 1119, so that a selection signal is generated. The generated selection signal is buffered and amplified in the buffer 1118 and supplied to the corresponding scanning line. The gates of the switching transistors of the pixels for one row are connected to the scanning lines. Since the switching transistors of the pixels for one row must be turned on all at once, a buffer 1118 that can flow a large current is used.

  Instead of the shift register 1119, another circuit capable of selecting a signal line such as a decoder may be used.

  Next, the configuration of the selection line driver circuit 1120 will be described. The selection line driver circuit 1120 includes a shift register 1121 and a buffer 1122. In some cases, a level shifter may be provided. In the selection line driver circuit 1120, a selection signal is generated by inputting a clock (GCLK) and a start pulse signal (G2SP) to the shift register 1121. The generated selection signal is buffered and amplified in the buffer 1122 and supplied to the corresponding selection line. The selection line is connected to the gates of the data selection transistors of the pixels for one row. Since the data selection transistors of pixels for one row must be turned on all at once, a buffer 1122 that can flow a large current is used.

  Note that another circuit that can select a signal line such as a decoder may be used instead of the shift register 1121.

  Note that the scan line driver circuit 1112, the signal line driver circuit 1113, and the selection line driver circuit 1120 may be formed over the same substrate as the pixel portion 1111 or over a different substrate.

  In this embodiment, a cross-sectional structure of a pixel when a driving transistor is a p-type is described with reference to FIGS. Note that FIG. 11 illustrates the case where the first electrode is an anode and the second electrode is a cathode; however, the first electrode may be a cathode and the second electrode may be an anode.

  FIG. 11A is a cross-sectional view of a pixel in the case where the driving transistor 6001 and the data selection transistor 6002 are p-type and light emitted from the light-emitting element 6003 is extracted from the first electrode 6004 side. In FIG. 11A, the first electrode 6004 of the light-emitting element 6003 and the data selection transistor 6002 are electrically connected; however, the first electrode 6004 of the light-emitting element 6003 and the driving transistor 6001 are electrically connected. May be connected.

  The driving transistor 6001 and the data selection transistor 6002 are covered with an interlayer insulating film 6007, and a partition wall 6008 having an opening is formed over the interlayer insulating film 6007. A part of the first electrode 6004 is exposed in the opening of the partition wall 6008, and the first electrode 6004, the electroluminescent layer 6005, and the second electrode 6006 are sequentially stacked in the opening.

  The interlayer insulating film 6007 is formed using an organic resin film, an inorganic insulating film, or an insulating film including a Si—O—Si bond (hereinafter referred to as a siloxane-based insulating film) formed using a siloxane-based material as a starting material. Can do. The siloxane insulating film may have at least one of fluorine, an alkyl group, and aromatic hydrocarbon in addition to hydrogen as a substituent. A material called a low dielectric constant material (low-k material) may be used for the interlayer insulating film 6007.

  The partition wall 6008 can be formed using an organic resin film, an inorganic insulating film, or a siloxane-based insulating film. For example, acrylic resin, polyimide, polyamide, or the like can be used for the organic resin film, and silicon oxide, silicon nitride oxide, or the like can be used for the inorganic insulating film. In particular, a photosensitive organic resin film is used for the partition wall 6008, an opening is formed on the first electrode 6004, and the side wall of the opening is formed to have an inclined surface formed with a continuous curvature. Thus, the connection between the first electrode 6004 and the second electrode 6006 can be prevented.

  The first electrode 6004 is formed using a light-transmitting material or film thickness, and is formed using a material suitable for use as an anode. For example, another light-transmitting oxide conductive material such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), or zinc oxide added with gallium (GZO) is used for the first electrode 6004. Is possible. In addition, indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO), or indium oxide containing silicon oxide mixed with 2 to 20% zinc oxide (ZnO) is used as the first electrode 6004. It may be used. In addition to the light-transmitting oxide conductive material, for example, a single layer film made of one or more of TiN, ZrN, Ti, W, Ni, Pt, Cr, Ag, Al, etc., titanium nitride and aluminum are used. The first electrode 6004 can be formed using a stack including a main component film, a three-layer structure including a titanium nitride film, an aluminum main component film, and a titanium nitride film. Note that in the case where a material other than the light-transmitting oxide conductive material is used, the first electrode 6004 is formed with a thickness enough to transmit light (preferably, about 5 nm to 30 nm).

The second electrode 6006 can be formed using a material and a film thickness that reflect or shield light, and can be formed using a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like with a low work function. Specifically, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds thereof ( In addition to CaF ₂ and CaN, rare earth metals such as Yb and Er can be used. When an electron injection layer is provided, other conductive layers such as Al can be used.

  The electroluminescent layer 6005 is composed of one or more layers. When composed of a plurality of layers, these layers can be classified into a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and the like from the viewpoint of carrier transport characteristics. In the case where the electroluminescent layer 6005 includes any of a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer in addition to the light emitting layer, the first electrode 6004 to the positive hole injection layer, A hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer are laminated in this order. Note that the boundaries between the layers are not necessarily clear, and there are cases where the materials constituting the layers are partially mixed and the interface is unclear. For each layer, an organic material or an inorganic material can be used. As the organic material, any of a high molecular weight material, a medium molecular weight material, and a low molecular weight material can be used. The medium molecular weight material corresponds to a low polymer having a number of repeating structural units (degree of polymerization) of about 2 to 20. The distinction between a hole injection layer and a hole transport layer is not necessarily strict, and these are the same in the sense that hole transportability (hole mobility) is a particularly important characteristic. For convenience, the hole injection layer is a layer in contact with the anode, and the layer in contact with the hole injection layer is referred to as a hole transport layer to be distinguished. The same applies to the electron transport layer and the electron injection layer. The layer in contact with the cathode is called an electron injection layer, and the layer in contact with the electron injection layer is called an electron transport layer. The light emitting layer may also serve as an electron transport layer, and is also referred to as a light emitting electron transport layer.

  In the case of the pixel shown in FIG. 11A, light emitted from the light-emitting element 6003 can be extracted from the first electrode 6004 side as shown by a hollow arrow.

  Next, FIG. 11B is a cross-sectional view of a pixel in the case where the driving transistor 6011 and the data selection transistor 6012 are p-type and light emitted from the light-emitting element 6013 is extracted from the second electrode 6016 side. In FIG. 11B, the first electrode 6014 of the light-emitting element 6013 and the data selection transistor 6012 are electrically connected; however, the first electrode 6014 of the light-emitting element 6013 and the driving transistor 6011 are electrically connected. May be connected. In addition, an electroluminescent layer 6015 and a second electrode 6016 are sequentially stacked over the first electrode 6014.

  The first electrode 6014 is formed using a material and a film thickness that reflect or shield light, and is formed using a material that is suitable for use as an anode. For example, in addition to a single layer film made of one or more of TiN, ZrN, Ti, W, Ni, Pt, Cr, Ag, Al, etc., a laminate of titanium nitride and a film mainly composed of aluminum, a titanium nitride film A three-layer structure of a film mainly containing aluminum and aluminum and a titanium nitride film can be used for the first electrode 6014.

The second electrode 6016 can be formed using a light-transmitting material or film thickness, and can be formed using a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like with a low work function. Specifically, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds thereof ( In addition to CaF ₂ and CaN, rare earth metals such as Yb and Er can be used. When an electron injection layer is provided, other conductive layers such as Al can be used. Then, the second electrode 6016 is formed with a thickness enough to transmit light (preferably, about 5 nm to 30 nm). Note that other light-transmitting oxide conductive materials such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), and zinc oxide to which gallium is added (GZO) can also be used. Alternatively, indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO) or indium oxide containing silicon oxide mixed with 2 to 20% zinc oxide (ZnO) may be used. In the case of using a light-transmitting oxide conductive material, it is preferable to provide an electron injection layer in the electroluminescent layer 6015.

  The electroluminescent layer 6015 can be formed in a manner similar to that of the electroluminescent layer 6005 in FIG.

  In the case of the pixel shown in FIG. 11B, light emitted from the light-emitting element 6013 can be extracted from the second electrode 6016 side as shown by a hollow arrow.

  Next, FIG. 11C illustrates the case where the driving transistor 6021 and the data selection transistor 6022 are p-type, and light emitted from the light-emitting element 6023 is extracted from the first electrode 6024 side and the second electrode 6026 side. A cross-sectional view of a pixel is shown. In FIG. 11C, the first electrode 6024 of the light-emitting element 6023 and the data selection transistor 6022 are electrically connected; however, the first electrode 6024 of the light-emitting element 6023 and the driving transistor 6021 are electrically connected. May be connected. Further, an electroluminescent layer 6025 and a second electrode 6026 are sequentially stacked over the first electrode 6024.

  The first electrode 6024 can be formed in a manner similar to that of the first electrode 6004 in FIG. The second electrode 6026 can be formed in a manner similar to that of the second electrode 6016 in FIG. The electroluminescent layer 6025 can be formed in a manner similar to that of the electroluminescent layer 6005 in FIG.

  In the case of the pixel shown in FIG. 11C, light emitted from the light-emitting element 6023 can be extracted from the first electrode 6024 side and the second electrode 6026 side as indicated by white arrows.

  In this embodiment, a cross-sectional structure of a pixel in the case where an n-type driving transistor is described with reference to FIG. Note that FIG. 12 illustrates the case where the first electrode is a cathode and the second electrode is an anode, but the first electrode may be an anode and the second electrode may be a cathode.

  FIG. 12A is a cross-sectional view of a pixel in the case where the driving transistor 6031 and the data selection transistor 6032 are n-type and light emitted from the light-emitting element 6033 is extracted from the first electrode 6034 side. In FIG. 12A, the first electrode 6034 of the light-emitting element 6033 and the data selection transistor 6032 are electrically connected; however, the first electrode 6034 of the light-emitting element 6033 and the driving transistor 6031 are electrically connected. May be connected. Further, an electroluminescent layer 6035 and a second electrode 6036 are sequentially stacked over the first electrode 6034.

The first electrode 6034 can be formed using a light-transmitting material or film thickness, and can be formed using a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like with a low work function. Specifically, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds thereof ( In addition to CaF ₂ and CaN, rare earth metals such as Yb and Er can be used. When an electron injection layer is provided, other conductive layers such as Al can be used. Then, the first electrode 6034 is formed with a thickness enough to transmit light (preferably, about 5 nm to 30 nm). Further, a light-transmitting conductive layer is formed using a light-transmitting oxide conductive material so as to be in contact with or under the conductive layer having a thickness enough to transmit light, and the first electrode 6034 is formed. The sheet resistance may be suppressed. Note that only conductive layers using other light-transmitting oxide conductive materials such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), and zinc oxide to which gallium is added (GZO) should be used. Is also possible. Alternatively, indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO) or indium oxide containing silicon oxide mixed with 2 to 20% zinc oxide (ZnO) may be used. In the case of using a light-transmitting oxide conductive material, it is preferable to provide an electron injection layer in the electroluminescent layer 6035.

  The second electrode 6036 is formed of a material and a film thickness that reflect or shield light, and is formed using a material that is suitable for use as an anode. For example, in addition to a single layer film made of one or more of TiN, ZrN, Ti, W, Ni, Pt, Cr, Ag, Al, etc., a laminate of titanium nitride and a film mainly composed of aluminum, a titanium nitride film A three-layer structure of a film containing aluminum and aluminum as main components and a titanium nitride film can be used for the second electrode 6036.

  The electroluminescent layer 6035 can be formed in a manner similar to that of the electroluminescent layer 6005 in FIG. However, in the case where the electroluminescent layer 6035 includes any one of a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer in addition to the light emitting layer, the first electrode 6034 to the electron injection layer The electron transport layer, the light emitting layer, the hole transport layer, and the hole injection layer are laminated in this order.

  In the case of the pixel shown in FIG. 12A, light emitted from the light-emitting element 6033 can be extracted from the first electrode 6034 side as shown by a hollow arrow.

  Next, FIG. 12B is a cross-sectional view of a pixel in the case where the driving transistor 6041 and the data selection transistor 6042 are n-type and light emitted from the light-emitting element 6043 is extracted from the second electrode 6046 side. In FIG. 12B, the first electrode 6044 of the light-emitting element 6043 and the data selection transistor 6042 are electrically connected; however, the first electrode 6044 of the light-emitting element 6043 and the driving transistor 6041 are electrically connected. May be connected. Further, an electroluminescent layer 6045 and a second electrode 6046 are sequentially stacked over the first electrode 6044.

The first electrode 6044 can be formed using a material and a film thickness that reflect or shield light, and can be formed using a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like with a low work function. Specifically, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds thereof ( In addition to CaF ₂ and CaN, rare earth metals such as Yb and Er can be used. When an electron injection layer is provided, other conductive layers such as Al can be used.

  The second electrode 6046 is formed using a light-transmitting material or film thickness, and is formed using a material suitable for use as an anode. For example, another light-transmitting oxide conductive material such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), or zinc oxide added with gallium (GZO) is used for the second electrode 6046. Is possible. In addition, indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO), indium oxide containing silicon oxide, and further mixed with 2 to 20% zinc oxide (ZnO) are used as the second electrode 6046. It may be used. In addition to the light-transmitting oxide conductive material, for example, a single layer film made of one or more of TiN, ZrN, Ti, W, Ni, Pt, Cr, Ag, Al, etc., titanium nitride and aluminum are used. The second electrode 6046 can be formed using a stack of a main component film, a three-layer structure including a titanium nitride film, an aluminum main component film, and a titanium nitride film. Note that in the case where a material other than the light-transmitting oxide conductive material is used, the second electrode 6046 is formed with a thickness enough to transmit light (preferably, about 5 nm to 30 nm).

  The electroluminescent layer 6045 can be formed in a manner similar to that of the electroluminescent layer 6035 in FIG.

  In the case of the pixel shown in FIG. 12B, light emitted from the light-emitting element 6043 can be extracted from the second electrode 6046 side as shown by a hollow arrow.

  Next, FIG. 12C illustrates the case where the driving transistor 6051 and the data selection transistor 6052 are n-type, and light emitted from the light-emitting element 6053 is extracted from the first electrode 6054 side and the second electrode 6056 side. A cross-sectional view of a pixel is shown. In FIG. 12C, the first electrode 6054 of the light-emitting element 6053 and the data selection transistor 6052 are electrically connected; however, the first electrode 6054 of the light-emitting element 6053 and the driving transistor 6051 are electrically connected. May be connected. Further, an electroluminescent layer 6055 and a second electrode 6056 are stacked over the first electrode 6054 in this order.

  The first electrode 6054 can be formed in a manner similar to that of the first electrode 6034 in FIG. The second electrode 6056 can be formed in a manner similar to that of the second electrode 6046 in FIG. The electroluminescent layer 6055 can be formed in a manner similar to that of the electroluminescent layer 6035 in FIG.

  In the case of the pixel shown in FIG. 12C, light emitted from the light-emitting element 6053 can be extracted from the first electrode 6054 side and the second electrode 6056 side as indicated by white arrows.

  The light-emitting device of the present invention can be formed by a screen printing method, a printing method typified by an offset printing method, or a droplet discharge method. The droplet discharge method means a method of forming a predetermined pattern by discharging droplets containing a predetermined composition from the pores, and includes an ink jet method and the like in its category. By using the above printing method and droplet discharge method, various wirings typified by signal lines, scanning lines, selection lines, TFT gates, and light emitting element electrodes can be formed without using an exposure mask. Is possible. However, it is not necessary to use a printing method or a droplet discharge method for all the steps of forming a pattern. Therefore, for example, a printing method or a droplet discharge method is used in at least a part of the process, for example, a printing method or a droplet discharge method is used for forming a wiring and a gate, and a lithography method is used for patterning a semiconductor film. As long as it is, a lithography method may be used in combination. A mask used for patterning may be formed by a printing method or a droplet discharge method.

  FIG. 13 shows, as an example, a cross-sectional view of a light-emitting device of the present invention formed using a droplet discharge method. In FIG. 13, 1301 is a data selection transistor, 1302 is a driving transistor, 1303 is a switching transistor, and 1304 is a light emitting element. In FIG. 13, the data selection transistor 1301 is electrically connected to the first electrode of the light-emitting element 1304; however, the present invention is not limited to this structure. The driving transistor 1302 may be electrically connected to the first electrode 1350 of the light-emitting element 1304. The driving transistor 1302 is preferably n-type, and in this case, the first electrode 1350 is preferably a cathode, and the second electrode 1331 is preferably an anode.

  The switching transistor 1303 includes a gate 1310, a first semiconductor film 1311 including a channel formation region, a gate insulating film 1317 formed in the gate 1310 and the first semiconductor film 1311, and a second functioning as a source or a drain. Semiconductor films 1312 and 1313, a wiring 1314 connected to the second semiconductor film 1312, and a wiring 1315 connected to the second semiconductor film 1313.

  The data selection transistor 1301 includes a gate 1320, a first semiconductor film 1321 including a channel formation region, a gate insulating film 1317 formed in the gate 1320 and the first semiconductor film 1321, and a first functioning as a source or a drain. 2 semiconductor films 1322 and 1323, a wiring 1324 connected to the second semiconductor film 1322, and a wiring 1325 connected to the second semiconductor film 1323.

  The driving transistor 1302 includes a gate 1330, a first semiconductor film 1321 including a channel formation region, a gate insulating film 1317 formed in the gate 1330 and the first semiconductor film 1321, and a second functioning as a source or a drain. The semiconductor films 1323 and 1333, the wiring 1325 connected to the second semiconductor film 1323, and the wiring 1335 connected to the second semiconductor film 1333 are included.

  The wiring 1314 corresponds to a signal line, and the wiring 1315 is electrically connected to the gate 1320 of the data selection transistor 1301. The wiring 1335 corresponds to a power supply line, and the gate 1330 is connected to the power supply line (not shown).

  By forming a pattern using a droplet discharge method or a printing method, a series of steps such as photoresist film formation, exposure, development, etching, and peeling performed by a lithography method can be simplified. Further, unlike the lithography method, the droplet discharge method and the printing method do not waste material that is removed by etching. Further, it is not necessary to use an expensive exposure mask, so that the cost for manufacturing the light-emitting device can be suppressed.

  Further, unlike the lithography method, it is not necessary to perform etching to form the wiring. Therefore, the time spent for the process of forming the wiring can be significantly shortened compared to the case of the lithography method. In particular, when the wiring thickness is 0.5 μm or more, and more desirably 2 μm or more, the wiring resistance can be suppressed. Therefore, the wiring accompanying the increase in the size of the light-emitting device while suppressing the time spent in the wiring manufacturing process. An increase in resistance can be suppressed.

  Note that the first semiconductor films 1311 and 1321 may be either an amorphous semiconductor or a semi-amorphous semiconductor (SAS).

An amorphous semiconductor can be obtained by glow discharge decomposition of a silicide gas. Typical silicide gases include SiH ₄ and Si ₂ H ₆ . This silicide gas may be diluted with hydrogen, hydrogen and helium.

SAS can also be obtained by glow discharge decomposition of silicide gas. A typical silicide gas is SiH ₄ , and in addition, Si ₂ H ₆ , SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ , SiF _{4 and the} like can be used. In addition, it is easy to form a SAS by diluting and using this silicide gas with hydrogen or a gas obtained by adding one or more kinds of rare gas elements selected from helium, argon, krypton, and neon to hydrogen. It can be. It is preferable to dilute the silicide gas at a dilution rate in the range of 2 to 1000 times. Furthermore, a carbide gas such as CH ₄ or C ₂ H ₆ , a germanium gas such as GeH ₄ or GeF ₄ , F ₂ or the like is mixed in the silicide gas, so that the energy bandwidth is 1.5-2. You may adjust to 4 eV or 0.9-1.1 eV. A TFT using SAS as the first semiconductor film can obtain a mobility of 1 to 10 cm ² / Vsec or more.

  The first semiconductor films 1311 and 1321 may be formed using a semiconductor obtained by laser crystallization of an amorphous semiconductor or a semi-amorphous semiconductor (SAS).

  In this example, the appearance of a panel corresponding to one embodiment of the light-emitting device of the present invention will be described with reference to FIG. 14 is a top view of a panel in which a transistor and a light-emitting element formed over the first substrate are sealed with a sealant between the second substrate and FIG. 14B. This corresponds to a cross-sectional view taken along line AA ′ in FIG.

  A sealant 4005 is provided so as to surround the pixel portion 4002, the signal line driver circuit 4003, the scan line driver circuit 4004, and the selection line driver circuit 4020 provided over the first substrate 4001. A second substrate 4006 is provided over the pixel portion 4002, the signal line driver circuit 4003, the scan line driver circuit 4004, and the selection line driver circuit 4020. Accordingly, the pixel portion 4002, the signal line driver circuit 4003, the scan line driver circuit 4004, and the selection line driver circuit 4020 are combined with the filler 4007 by the first substrate 4001, the sealant 4005, and the second substrate 4006. Sealed.

  In addition, the pixel portion 4002, the signal line driver circuit 4003, the scan line driver circuit 4004, and the selection line driver circuit 4020 provided over the first substrate 4001 each include a plurality of transistors. ) Illustrates a transistor 4008 included in the signal line driver circuit 4003, and a driving transistor 4009 and a data selection transistor 4010 included in the pixel portion 4002.

  Reference numeral 4011 corresponds to a light-emitting element, and a part of the wiring 4017 connected to the drain of the driving transistor 4009 functions as a first electrode of the light-emitting element 4011. The transparent conductive film 4012 functions as the second electrode of the light-emitting element 4011. Note that the structure of the light-emitting element 4011 is not limited to the structure shown in this embodiment. The structure of the light-emitting element 4011 can be changed as appropriate depending on the direction of light extracted from the light-emitting element 4011, the polarity of the driving transistor 4009, or the like.

  Note that although an example in which the driving transistor 4009 is connected to the first electrode of the light emitting element 4011 is shown in this embodiment, the data selection transistor 4010 is connected to the first electrode of the light emitting element 4011. Also good.

  Further, various signals and voltages supplied to the signal line driver circuit 4003, the scan line driver circuit 4004, or the pixel portion 4002 are not shown in the cross-sectional view in FIG. 14B, but are routed through lead wirings 4014 and 4015. It is supplied from the connection terminal 4016.

  In this embodiment, the connection terminal 4016 is formed using the same conductive film as the first electrode included in the light-emitting element 4011. Further, the lead wiring 4014 is formed of the same conductive film as the wiring 4017. The lead wiring 4015 is formed of the same conductive film as the gates of the driving transistor 4009 and the transistor 4008.

  The connection terminal 4016 is electrically connected to a terminal included in the FPC 4018 through an anisotropic conductive film 4019.

  Note that as the first substrate 4001 and the second substrate 4006, glass, metal (typically stainless steel), ceramics, or plastic can be used. As the plastic, an FRP (Fiberglass-Reinforced Plastics) plate, a PVF (polyvinyl fluoride) film, a mylar film, a polyester film, or an acrylic resin film can be used. A sheet having a structure in which an aluminum foil is sandwiched between PVF films or mylar films can also be used.

  Note that the second substrate 4006 must have a light-transmitting property with respect to the substrate positioned in the light extraction direction from the light-emitting element 4011. In that case, a light-transmitting material such as a glass plate, a plastic plate, a polyester film, or an acrylic film is used.

  As the filler 4007, in addition to an inert gas such as nitrogen or argon, an ultraviolet curable resin or a thermosetting resin can be used. PVC (polyvinyl chloride), acrylic, polyimide, epoxy resin, silicon resin, PVB (Polyvinyl butyral) or EVA (ethylene vinyl acetate) can be used. In this example, nitrogen was used as the filler.

  This embodiment can be implemented in combination with any of Embodiments 1 to 5.

  Since the light-emitting device of the present invention can prevent a pseudo contour or increase contrast, it is most suitable for an electronic apparatus having a display unit for viewing an image such as a display device or a goggle type display.

  Other electronic devices that can use the light emitting device of the present invention include a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, a sound reproduction device (car audio, audio component, etc.), and a notebook type personal computer. A game machine, a portable information terminal (mobile computer, mobile phone, portable game machine, electronic book or the like), an image playback device equipped with a recording medium (typically a DVD: Digital Versatile Disc or the like, And a device having a display capable of displaying the image). Specific examples of these electronic devices are shown in FIGS.

  FIG. 15A illustrates a personal digital assistant (PDA), which includes a main body 2101, a display portion 2102, operation keys 2103, a speaker portion 2104, and the like. The light emitting device of the present invention can be used for the display portion 2102.

  FIG. 15B illustrates a goggle type display device, which includes a main body 2201, a display portion 2202, earphones 2203, and a support portion 2204. The light emitting device of the present invention can be used for the display portion 2202. The support unit 2204 may be a type that fixes the goggle type display device to the head itself, or may be a type that fixes the goggle type display device to a portion other than the head of the user's body.

  FIG. 15C illustrates a display device, which includes a housing 2401, a display portion 2402, a speaker portion 2403, and the like. The light emitting device of the present invention can be used for the display portion 2402. Since the light-emitting device is a self-luminous type, a backlight is not necessary and a display portion thinner than a liquid crystal display can be obtained. The display devices include all information display devices for computers, for receiving TV broadcasts, for displaying advertisements, and the like. Note that in the case where a light-emitting device is used for the display device, a polarizing plate is provided in order to prevent external light from being reflected by the first electrode or the second electrode included in the light-emitting element to cause an image to be projected like a mirror surface. You can keep it.

  As described above, the applicable range of the present invention is so wide that it can be used for electronic devices in various fields. In addition, the electronic device of this embodiment may use the light emitting device having any structure shown in Embodiments 1 to 6.

FIG. 6 is a circuit diagram of a pixel included in the light-emitting device of the present invention. The figure which shows operation | movement of the pixel of FIG. The figure which shows operation | movement of the pixel of FIG. 2 is a timing chart showing the operation of the pixel in FIG. 1. FIG. 6 is a circuit diagram of a pixel included in the light-emitting device of the present invention. 6 is a timing chart illustrating an operation when n = 6 in the pixel illustrated in FIG. 5. FIG. 6 is a circuit diagram of a pixel included in the light-emitting device of the present invention. FIG. 6 is a circuit diagram of a pixel included in the light-emitting device of the present invention. FIG. 2 is a top view of the pixel in FIG. 1. FIG. 6 is a block diagram illustrating a structure of a driving circuit included in the light emitting device of the invention. 4 is a cross-sectional view of a pixel included in a light-emitting device of the present invention. FIG. 4 is a cross-sectional view of a pixel included in a light-emitting device of the present invention. FIG. 4 is a cross-sectional view of a pixel included in a light-emitting device of the present invention. FIG. 2A and 2B are a top view and a cross-sectional view of a light-emitting device of the present invention. FIG. 14 is a diagram of an electronic device using the light-emitting device of the present invention. 6 is a timing chart illustrating an operation when n = 6 in the pixel illustrated in FIG. 5.

Explanation of symbols

101 Light-Emitting Element 102 (1) Switching Transistor 102 (2) Switching Transistor 103 (1) Driving Transistor 103 (2) Driving Transistor 104 (1) Data Selection Transistor 104 (2) Data Selection Transistor 106 (1 ) Capacitor element 106 (2) Capacitor element 201 Light emitting element 202 (1) Switching transistor 202 (2) Switching transistor 202 (n) Switching transistor 203 (1) Driving transistor 203 (2) Driving transistor 203 (n ) Driving transistor 204 (1) Data selection transistor 204 (2) Data selection transistor 204 (n) Data selection transistor 206 (1) Capacitance element 206 (2) Capacitance element 206 (n) Capacitance element 90 1 Electrode 902 Region 903 Gate 904 Gate 905 Active layer 906 Active layer 907 Gate 908 Gate 1111 Pixel portion 1112 Scan line driver circuit 1113 Signal line driver circuit 1114 Shift register 1115 Latch A
1116 Latch B
1118 Buffer 1119 Shift register 1120 Select line drive circuit 1121 Shift register 1122 Buffer 1301 Data selection transistor 1302 Drive transistor 1303 Switching transistor 1304 Light emitting element 1310 Gate 1311 Semiconductor film 1312 Semiconductor film 1313 Semiconductor film 1314 Wire 1315 Wire 1317 Gate insulating film 1320 Gate 1321 Semiconductor film 1322 Semiconductor film 1323 Semiconductor film 1324 Wiring 1325 Wiring 1330 Wiring 1331 Electrode 1333 Semiconductor film 1335 Wiring 1350 Electrode 2101 Main body 2102 Display section 2103 Operation key 2104 Speaker section 2201 Main body 2202 Display section 2203 Earphone 2204 Support section 2401 Housing 2402 Display portion 2403 Speaker portion 4001 Substrate 002 pixel portion 4003 signal line driver circuit 4004 scanning line driver circuit 4005 sealant 4006 substrate 4007 filler 4008 transistors 4009 driver transistor 4010 data selecting transistor 4011 emitting element 4012 transparent conductive film 4014 lines 4015 lines 4016 connect terminals 4017 wiring 4018 FPC
4019 Anisotropic conductive film 4020 Selection line driver circuit 6001 Driving transistor 6002 Data selection transistor 6003 Light emitting element 6004 Electrode 6005 Electroluminescent layer 6006 Electrode 6007 Interlayer insulating film 6008 Partition 6011 Driving transistor 6012 Data selecting transistor 6013 Light emitting element 6014 Electrode 6015 Electroluminescent layer 6016 Electrode 6021 Driving transistor 6022 Data selecting transistor 6023 Light emitting element 6024 Electrode 6025 Electroluminescent layer 6026 Electrode 6031 Driving transistor 6032 Data selecting transistor 6033 Light emitting element 6034 Electrode 6035 Electroluminescent layer 6036 Electrode 6041 Driving Transistor 6042 Data selection transistor 6043 Light emitting element 6044 Electrode 6045 Electroluminescent layer 60 6 electrode 6051 driving transistor 6052 data selecting transistor 6053 emitting element 6054 electrodes 6055 electroluminescent layer 6056 electrodes

Claims (8)

A light emitting element;
A first signal line, a second signal line, a power supply line, and a selection line;
A first switch and a second switch;
A first transistor, a second transistor, a third transistor, and a fourth transistor;
The third transistor and the fourth transistor have different polarities,
One electrode of the first switch is electrically connected to the first signal line,
The other electrode of the first switch is electrically connected to the gate of the first transistor;
One electrode of the second switch is electrically connected to the second signal line,
The other electrode of the second switch is electrically connected to the gate of the second transistor;
One of a source or a drain of the first transistor and one of a source or a drain of the second transistor are electrically connected to the power supply line;
The other of the source and the drain of the first transistor is electrically connected to one of the source and the drain of the third transistor;
The other of the source and the drain of the second transistor is electrically connected to one of the source and the drain of the fourth transistor;
A gate of the third transistor and a gate of the fourth transistor are electrically connected to the selection line;
The other of the source and the drain of the third transistor and the other of the source and the drain of the fourth transistor are electrically connected to the light emitting element;
A first period in which the first switch and the second switch are on, and video signals of different bits are input to the first signal line and the second signal line;
After the first period, the first switch and the second switch are off, and a second period in which current from the power supply line is supplied to the light emitting element through the third transistor When,
After the second period, a third period in which the first switch and the second switch are off and a current from the power supply line is supplied to the light emitting element through the fourth transistor. And a light-emitting device. A light emitting element;
A first signal line, a second signal line, a power supply line, and a selection line;
A first switch and a second switch;
A first transistor, a second transistor, a third transistor, and a fourth transistor;
A first capacitive element and a second capacitive element;
The third transistor and the fourth transistor have different polarities,
One electrode of the first switch is electrically connected to the first signal line,
The other electrode of the first switch is electrically connected to the gate of the first transistor and one electrode of the first capacitor;
One electrode of the second switch is electrically connected to the second signal line,
The other electrode of the second switch is electrically connected to the gate of the second transistor and one electrode of the second capacitor,
The other electrode of the first capacitor element and the other electrode of the second capacitor element are electrically connected to the power line,
One of a source or a drain of the first transistor and one of a source or a drain of the second transistor are electrically connected to the power supply line;
The other of the source and the drain of the first transistor is electrically connected to one of the source and the drain of the third transistor;
The other of the source and the drain of the second transistor is electrically connected to one of the source and the drain of the fourth transistor;
A gate of the third transistor and a gate of the fourth transistor are electrically connected to the selection line;
The other of the source and the drain of the third transistor and the other of the source and the drain of the fourth transistor are electrically connected to the light emitting element;
A first period in which the first switch and the second switch are on, and video signals of different bits are input to the first signal line and the second signal line;
After the first period, the first switch and the second switch are off, and a second period in which current from the power supply line is supplied to the light emitting element through the third transistor When,
After the second period, a third period in which the first switch and the second switch are off and a current from the power supply line is supplied to the light emitting element through the fourth transistor. And a light-emitting device. A light emitting element;
A first signal line, a second signal line, a power supply line, and a selection line;
A first switch and a second switch;
A first transistor, a second transistor, a third transistor, and a fourth transistor;
The third transistor and the fourth transistor have different polarities,
One electrode of the first switch is electrically connected to the first signal line,
The other electrode of the first switch is electrically connected to the gate of the first transistor;
One electrode of the second switch is electrically connected to the second signal line,
The other electrode of the second switch is electrically connected to the gate of the second transistor;
One of the source or drain of the first transistor and one of the source or drain of the second transistor are electrically connected to the light emitting element,
The other of the source and the drain of the first transistor is electrically connected to one of the source and the drain of the third transistor;
The other of the source and the drain of the second transistor is electrically connected to one of the source and the drain of the fourth transistor;
A gate of the third transistor and a gate of the fourth transistor are electrically connected to the selection line;
The other of the source and the drain of the third transistor and the other of the source and the drain of the fourth transistor are electrically connected to the power supply line;
A first period in which the first switch and the second switch are on, and video signals of different bits are input to the first signal line and the second signal line;
After the first period, the first switch and the second switch are off, and a second period in which current from the power supply line is supplied to the light emitting element through the third transistor When,
After the second period, a third period in which the first switch and the second switch are off and a current from the power supply line is supplied to the light emitting element through the fourth transistor. And a light-emitting device. A light emitting element;
A first signal line, a second signal line, a power supply line, and a selection line;
A first switch and a second switch;
A first transistor, a second transistor, a third transistor, and a fourth transistor;
A first capacitive element and a second capacitive element;
The third transistor and the fourth transistor have different polarities,
One electrode of the first switch is electrically connected to the first signal line,
The other electrode of the first switch is electrically connected to the gate of the first transistor and one electrode of the first capacitor;
One electrode of the second switch is electrically connected to the second signal line,
The other electrode of the second switch is electrically connected to the gate of the second transistor and one electrode of the second capacitor,
The other electrode of the first capacitor element and the other electrode of the second capacitor element are electrically connected to the power line,
One of the source or drain of the first transistor and one of the source or drain of the second transistor are electrically connected to the light emitting element,
The other of the source and the drain of the first transistor is electrically connected to one of the source and the drain of the third transistor;
The other of the source and the drain of the second transistor is electrically connected to one of the source and the drain of the fourth transistor;
A gate of the third transistor and a gate of the fourth transistor are electrically connected to the selection line;
The other of the source and the drain of the third transistor and the other of the source and the drain of the fourth transistor are electrically connected to the power supply line;
A first period in which the first switch and the second switch are on, and video signals of different bits are input to the first signal line and the second signal line;
After the first period, the first switch and the second switch are off, and a second period in which current from the power supply line is supplied to the light emitting element through the third transistor When,
After the second period, a third period in which the first switch and the second switch are off and a current from the power supply line is supplied to the light emitting element through the fourth transistor. And a light-emitting device. In claim 1 or 2,
The light emitting element includes an anode, a cathode, and an electroluminescent layer provided between the anode and the cathode,
The first transistor and the second transistor are p-channel type,
The other electrode of the third transistor and the other electrode of the fourth transistor are electrically connected to the anode. In claim 1 or 2,
The light emitting element includes an anode, a cathode, and an electroluminescent layer provided between the anode and the cathode,
The first transistor and the second transistor are n-channel type,
The other electrode of the third transistor and the other electrode of the fourth transistor are electrically connected to the cathode. In any one of Claims 1 thru | or 6,
The first transistor and the third transistor share an active layer;
The light emitting device, wherein the second transistor and the fourth transistor share an active layer. An electronic apparatus comprising the light emitting device according to claim 1.

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