JP4477400B2 - LIGHT EMITTING DEVICE AND ELECTRONIC DEVICE - Google Patents

Description

  The present invention relates to an electronic device using a light emitting device, and particularly to a portable electronic device.

  In addition to a display device for displaying images, portable electronic devices represented by mobile phones and electronic notebooks are required to have various functions such as sending and receiving mail, voice recognition, and capturing video with a small camera. On the other hand, user needs for downsizing and weight reduction are still strong. Therefore, it is necessary to mount more ICs having a larger circuit scale and memory capacity in the limited volume of portable electronic devices. The key point is how to make the flat panel display thinner and lighter in order to increase the functionality by securing a space to accommodate the IC, and to reduce the size and weight of portable electronic devices. It becomes.

  For example, in the case of a liquid crystal display device that is used relatively frequently in portable electronic devices, a light source, a light guide plate, and the like are required for a transmissive type, which hinders reduction in thickness and weight. In addition, the reflective type that uses external light makes it difficult to recognize images in the dark, and it does not take full advantage of portable electronic devices that can be used anywhere. Therefore, in recent years, mounting of a light emitting device using a light emitting element as a display element on a portable electronic device has been studied and is being put into practical use. Since the light emitting element emits light by itself, unlike a liquid crystal display device, a clear image can be displayed in a dark place without providing a light source. Therefore, the use of backlight components such as a light source and a light guide plate can be omitted, and the display device can be reduced in thickness and weight.

  By using the light-emitting device in this way, it is possible to improve the functionality, size, and weight of portable electronic devices, but on the other hand, there is also a problem of how to enlarge the screen to be displayed. . One of the reasons is that it is necessary to display more information as the functionality of portable electronic devices increases. In addition, the demand for portable electronic devices for elderly people who can increase the size of characters to be displayed is growing due to the increase in the population of elderly people, which is another reason for increasing the screen size.

  In view of the above-described problems, an object of the present invention is to propose an electronic device, particularly a portable electronic device, capable of realizing a large screen while achieving weight reduction and downsizing.

  In the present invention, in order to solve the above-mentioned problems, the following measures are taken. A structure in which light from the light emitting element is emitted from both sides of the light emitting device is used, and an area in which an image can be displayed is doubled by combining the front and back sides. When different images are displayed on both sides, video signals corresponding to two screens are alternately input. By using a light-emitting device that can display on both sides in this manner, it is possible to expand the area in which an image can be displayed, while reducing the size and weight of the light-emitting device.

  Note that the light-emitting device includes a light-emitting panel in which a light-emitting element is sealed, and a module in which an IC or the like including a controller is mounted on the panel.

  Further, a full color image is displayed on at least one screen of the light emitting device. Specifically, a white light emitting element is used for each pixel, and light emitted from the light emitting element is passed through a color filter to obtain a full color image. Full color display using color filters is an existing technology established in liquid crystal display devices, and has the advantage of being easily diverted to light emitting devices. Compared to the method of full color using light emitting elements corresponding to each of the three primary colors, it is not necessary to precisely separate the electroluminescent material with a shadow mask, and the luminance change over time is uniform for all colors. There is also an advantage. Like the CCM system that converts blue light into green or red using a color conversion material (CCM) made of a fluorescent material, the purity of red is low due to low color conversion efficiency, or the color conversion material itself is fluorescent. Since it is a body, there is no problem that the pixel emits light due to external light such as sunlight and the contrast is lowered.

  When a white light emitting element is used, a color filter is provided only on one screen, so that a full color image can be displayed on one screen and a monochrome image can be displayed on the other screen. In this case, the number of pixels for displaying monochrome can be tripled compared to other full-color display methods. Note that since the transmittance of the color filter is different for each color, the luminance of the light-emitting element obtained through the color filter may vary for each color. In this case, if the voltage applied to the light emitting element is changed for each color in order to correct the color, the deterioration is easily promoted in the light emitting element having the highest applied voltage, and the deterioration is suppressed in the light emitting element having the lowest applied voltage. For this reason, the luminance tends to vary with the lapse of the light emission time. Therefore, in the present invention, when a monochrome image is displayed on the surface opposite to the surface provided with the color filter, the image is displayed using a light emitting element having the lowest applied voltage. With the above structure, variation in deterioration of the light-emitting element due to a difference in applied voltage can be suppressed.

  By the way, TFTs using polysilicon have a problem that their characteristics are likely to vary due to defects formed in crystal grain boundaries. When the threshold voltage of the TFT varies, the luminance of the light emitting element in which the flowing current is controlled by the TFT also varies. In addition, there is a problem in that the luminance of the light emitting element decreases with the deterioration of the electroluminescent material. Even if the current supplied to the light emitting element is constant, the luminance decreases as the electroluminescent material deteriorates. Since the degree of deterioration depends on the light emission time and the amount of flowing current, if the gradation for each pixel differs depending on the image to be displayed, the deterioration of the light emitting element of each pixel will be different and the luminance will vary. End up.

  In addition, by operating a transistor for controlling a current value supplied to the light emitting element in a saturation region, it is possible to suppress a decrease in luminance due to deterioration of the electroluminescent layer to some extent. However, since the drain current in the saturation region greatly affects the flowing current with respect to a slight change in the gate-source voltage Vgs, the gate-source voltage Vgs changes during the period in which the light emitting element emits light. You need to be careful not to. For that purpose, it is necessary to increase the capacitance of the capacitor provided between the gate and the source of the transistor, or to suppress the off-state current of the transistor that controls the input of the video signal to the pixel. There is also a problem that Vgs of a transistor that controls a current value supplied to the light-emitting element changes with switching of other transistors, a change in potential of a signal line, a scanning line, or the like. This is due to the parasitic capacitance at the gate of the transistor.

  Therefore, in the present invention, in addition to the above-described means, the pixel configuration described below may be used for a light emitting device.

  First, in addition to a transistor for supplying current to the light emitting element (driving transistor), a transistor functioning as a switching element (current control transistor) is connected in series to the driving transistor. The gate potential of the driving transistor is fixed, and the driving transistor is operated in the saturation region so that a current can always flow. The current control transistor operates in a linear region, and a video signal is input to the gate of the current control transistor.

  Since the current control transistor operates in a linear region, its source-drain voltage (drain voltage) Vds is very small with respect to the voltage Vel applied to the light emitting element, and the gate-source voltage (gate voltage) Vgs is a little. The fluctuation does not affect the current flowing through the light emitting element. Since the driving transistor operates in the saturation region, the drain current is not changed by the drain voltage Vds, but is determined only by Vgs. That is, the current control transistor only selects whether to supply current to the light emitting element, and the value of the current flowing through the light emitting element is determined by the driving transistor operating in the saturation region. Therefore, the light emitting element can be obtained without increasing the capacity of the capacitor provided between the gate and the source of the current control transistor or suppressing the off current of the transistor for controlling the input of the video signal to the pixel. It does not affect the current flowing through. Further, the current flowing through the light emitting element is not affected by the parasitic capacitance attached to the gate of the current control transistor. For this reason, variation factors can be reduced and the image quality can be greatly improved. Further, by operating the driving transistor in the saturation region, the drain current value is kept relatively constant even when Vds is reduced instead of Vel being increased as the light emitting element is deteriorated. Accordingly, a reduction in luminance can be suppressed even when the light emitting element is deteriorated. In addition, since it is not necessary to optimize the process in order to keep the off-state current of the transistor that controls the input of the video signal to the pixel low, the transistor manufacturing process can be simplified, which greatly contributes to cost reduction and yield improvement. be able to.

  Further, the drive transistor L may be longer than W, and the current control transistor L may be equal to or shorter than W. More preferably, the ratio of L to W of the driving transistor is 5 or more. With the above structure, variation in luminance of the light-emitting element between pixels due to a difference in characteristics of the driving transistor can be suppressed.

  Note that the transistor used in the light-emitting device of the present invention may be a transistor formed using single crystal silicon, a transistor using SOI, or polycrystalline silicon or amorphous silicon. It may be a thin film transistor. 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 gate electrodes.

  By using a light-emitting device capable of displaying on both sides for the present invention, the area in which an image can be displayed can be expanded while the light-emitting device is reduced in size and weight. Further, full-color display using a color filter is an existing technology established in a liquid crystal display device, and has an advantage that it can be easily used for a light-emitting device. Compared to the method of full color using light emitting elements corresponding to each of the three primary colors, it is not necessary to precisely separate the electroluminescent material with a shadow mask, and the luminance change over time is uniform for all colors. There is also an advantage. Like the CCM system that converts blue light into green or red using a color conversion material (CCM) made of a fluorescent material, the purity of red is low due to low color conversion efficiency, or the color conversion material itself is fluorescent. Since it is a body, there is no problem that the pixel emits light due to external light such as sunlight and the contrast is lowered.

  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.

(Embodiment 1)
A specific configuration of the present invention will be described with reference to FIG. FIG. 1A illustrates one mode of a cross-sectional structure of a light-emitting device of the present invention. A light-emitting device of the present invention illustrated in FIG. 1A includes a light-emitting panel 101 including a light-emitting element in each pixel, two color filters 102 and 103 existing between the light-emitting panel 101, and the light-emitting panel 101. And two polarizing plates 104 and 105 existing with the color filters 102 and 103 interposed therebetween.

  The light-emitting panel 101 has a configuration in which light from the light-emitting element is emitted from both surfaces as indicated by white arrows. Specifically, each light-emitting element has a property of transmitting light (translucent light). The electrode having a property) is used as an anode and a cathode. The light emitting element is characterized in that the color of light emitted is white. Of the light emitted from both surfaces of the light emitting panel 101, light in a specific wavelength region is transmitted through the color filters 102 and 103, and only light having a specific deflection component is transmitted through the polarizing plates 104 and 105.

  The polarizing plates 104 and 105 are arranged so that the deflection angles transmitted from each other are different, more preferably the deflection angles are different from each other by 90 degrees, thereby preventing external light from being transmitted through the light emitting panel. FIG. 2A shows the direction of external light that passes through the light-emitting panel 201 when no polarizing plate is provided. FIG. 2B shows the direction of light emitted from the light-emitting panel 201 when the light-emitting panel 201 is sandwiched between two polarizing plates 202 and 203 having different deflection angles.

  In the case where a polarizing plate is not provided as illustrated in FIG. 2A, the light-emitting element included in the light-emitting panel 201 has a light-transmitting property in both an anode and a cathode. Accordingly, since external light passes through the light-emitting panel 201, the other side of the light-emitting panel 201 can be seen through to human eyes. On the other hand, when the polarizing plates 202 and 203 are provided as shown in FIG. 2B, only one of the two polarizing plates 202 and 203 transmits external light. Therefore, it is possible to prevent the other side of the light emitting panel 201 from being seen through, and to increase the contrast of the image. However, light emitted from the light-emitting panel 201 is transmitted through the polarizing plates 202 and 203, respectively, so that light can be obtained from both surfaces.

  FIG. 1B shows a different form of the cross-sectional structure of the light-emitting device of the present invention from FIG. A light-emitting device of the present invention illustrated in FIG. 1B includes a light-emitting panel 111 including a light-emitting element in each pixel, two color filters 112 and 113 that are interposed between the light-emitting panels 111, and the light-emitting panel 111. And two liquid crystal panels 114 and 115 existing between the color filters 112 and 113, respectively.

  As in FIG. 1A, the light-emitting panel 111 has a structure in which light from a light-emitting element is emitted from both surfaces. Specifically, each light-emitting element has an electrode having a light-transmitting property as an anode. And used as a cathode. The light emitting element is characterized in that the color of light emitted is white. Of the light emitted from both sides of the light emitting panel 111, light in a specific wavelength region is transmitted through the color filters 112 and 113, and light is transmitted through only one side of the liquid crystal panels 114 and 115.

  The liquid crystal panels 114 and 115 each include a pixel electrode, a counter electrode, and a liquid crystal provided between the pixel electrode and the counter electrode, and further include a polarizing plate and the like. In the liquid crystal panels 114 and 115, light transmittance is controlled by a voltage applied between the pixel electrode and the counter electrode. The two liquid crystal panels 114 and 115 control the driving so that one transmits light while the other does not transmit light. With the above structure, it is possible to prevent external light from being transmitted through the light-emitting panel 111.

  1A and 1B, a color filter is provided separately from the light-emitting panels 101 and 111; however, a film functioning as a color filter may be provided inside the light-emitting panel.

  FIG. 3A illustrates a state of a light-emitting device in which light is transmitted through the liquid crystal panel 302 among the two liquid crystal panels 302 and 303 existing with the light-emitting panel 301 interposed therebetween. FIG. 3B illustrates a light-emitting device in which light is transmitted through the liquid crystal panel 303 among the two liquid crystal panels 302 and 303 existing with the light-emitting panel 301 interposed therebetween.

  As shown in FIGS. 3A and 3B, when one of the liquid crystal panels 302 and 303 transmits light, the other is driven so that the other shields the light. Therefore, the light emitted from the light emitting element 304 of the light emitting panel 301 is transmitted only on one surface side, as indicated by the white arrows. With the above structure, it is possible to prevent a situation in which the other side of the light-emitting panel 301 is seen through to the human eye by transmitting external light, and it is possible to increase contrast. Further, the video signal may be switched in synchronization with the switching of the transmittance of the liquid crystal panels 302 and 303. Specifically, regardless of which liquid crystal panel transmits light, a video signal having image information on the light transmitting side is always input to the light emitting panel 301. With the above configuration, different images can be displayed on both sides of the light-emitting panel 301 in parallel.

  1A and 1B, the color filters are provided on both sides of the light-emitting panel, but may be provided only on one side. In this case, a monochrome image is displayed on the side of the light emitting panel where no color filter is provided. In the case of full color display, for example, the inter-color is expressed by three pixels corresponding to the three primary colors of red (R), green (G), and blue (B). Specifically, display can be performed with one pixel. However, the achromatic color cannot be expressed by one pixel in the method of performing full color using light emitting elements corresponding to the three primary colors or the CCM method. Therefore, in these two methods, an image is displayed with three pixels as a unit on a surface for monochrome display as well as a surface for full color display. On the other hand, in the present invention, since a white light emitting element is used, monochrome display can be performed with one pixel by not providing a color filter on one surface side.

  Note that in this embodiment mode, the light-emitting panel may be either an active matrix type or a passive matrix type.

  As described in this embodiment mode, the light-emitting device of the present invention can display images on both sides of the light-emitting panel, so that the light-emitting device can be reduced in size and weight, and the image display area can be expanded. Can do. The configuration of the present invention is particularly effective for portable electronic devices where emphasis is placed on miniaturization and weight reduction.

(Embodiment 2)
FIG. 4A illustrates one mode of a pixel included in the light-emitting device of the present invention. 4A controls a light-emitting element 401, a transistor (switching transistor) 402 used as a switching element for controlling input of a video signal to the pixel, and a current value flowing through the light-emitting element 401. The pixel illustrated in FIG. A driving transistor 403 and a current control transistor 404 for selecting whether or not to supply current to the light emitting element 401 are included. Further, as in this embodiment, a capacitor 405 for holding the potential of the video signal may be provided in the pixel.

  The driving transistor 403 and the current control transistor 404 have the same polarity. Although both are p-type in FIG. 4A, both may be n-type. In the present invention, the driving transistor 403 is operated in the saturation region, and the current control transistor 404 is operated in the linear region. Further, the channel length L of the driving transistor 403 may be longer than the channel width W, and L of the current control transistor 404 may be equal to or shorter than W. More preferably, the ratio of L to W of the driving transistor 403 is 5 or more. The driving transistor 403 may be an enhancement type transistor or a depletion type transistor.

  The gate of the switching transistor 402 is connected to the scanning line Gj (j = 1 to y). One of the source and the drain of the switching transistor 402 is connected to the signal line Si (i = 1 to x), and the other is connected to the gate of the current control transistor 404. The gate of the driving transistor 403 is connected to the second power supply line Wi (i = 1 to x). In the driving transistor 403 and the current control transistor 404, the current supplied from the first power supply line Vi (i = 1 to x) is used as the drain current of the driving transistor 403 and the current control transistor 404. Is connected to the first power supply line Vi (i = 1 to x) and the light emitting element 401. In this embodiment mode, the source of the current control transistor 404 is connected to the first power supply line Vi (i = 1 to x), and the drain of the driving transistor 403 is connected to the pixel electrode of the light emitting element 401.

  Note that the source of the driving transistor 403 may be connected to the first power supply line Vi (i = 1 to x), and the drain of the current control transistor 404 may be connected to the pixel electrode of the light-emitting element 401. In this case, the driving transistor 403 is a depletion type transistor.

  The light emitting element 401 includes an anode, a cathode, and an electroluminescent layer provided between the anode and the cathode. As shown in FIG. 4A, when the anode is connected to the driving transistor 403, the anode is a pixel electrode and the cathode is a counter electrode. A potential difference is provided between the counter electrode of the light emitting element 401 and each of the first power supply lines Vi (i = 1 to x) so that a forward bias current is supplied to the light emitting element 401.

  One of the two electrodes of the capacitor 405 is connected to the first power supply line Vi (i = 1 to x), and the other is connected to the gate of the current control transistor 404. The capacitor 405 is provided to hold a potential difference between the electrodes of the capacitor 405 when the switching transistor 402 is in a non-selected state (off state). Note that FIG. 4A illustrates a structure in which the capacitor 405 is provided; however, the present invention is not limited to this structure, and the capacitor 405 may not be provided.

  In FIG. 4A, the driving transistor 403 and the current control transistor 404 are p-channel transistors, and the drain of the driving transistor 403 and the anode of the light-emitting element 401 are connected. Conversely, if the driving transistor 403 and the current control transistor 404 are n-channel transistors, the source of the driving transistor 403 and the cathode of the light emitting element 401 are connected. In this case, the cathode of the light emitting element 401 is a pixel electrode, and the anode is a counter electrode.

  Next, a method for driving the pixel illustrated in FIG. The operation of the pixel illustrated in FIG. 4A can be described by being divided into a writing period and a holding period. First, when the scanning line Gj (j = 1 to y) is selected in the writing period, the switching transistor 402 whose gate is connected to the scanning line Gj (j = 1 to y) is turned on. The video signals input to the signal lines S1 to Sx are input to the gate of the current control transistor 404 via the switching transistor 402. Note that the driving transistor 403 is always on because the gate is connected to the first power supply line Vi (i = 1 to x).

  When the current control transistor 404 is turned on by a video signal, a current is supplied to the light emitting element 401 through the first power supply line Vi (i = 1 to x). At this time, since the current control transistor 404 operates in the linear region, the current flowing through the light-emitting element 401 is determined by the voltage-current characteristics of the driving transistor 403 and the light-emitting element 401 operating in the saturation region. The light-emitting element 401 emits light with a luminance corresponding to the supplied current. When the current control transistor 404 is turned off by the video signal, no current is supplied to the light emitting element 401 and the light emitting element 401 does not emit light.

  In the holding period, the switching transistor 402 is turned off by controlling the potential of the scanning line Gj (j = 1 to y), and the potential of the video signal written in the writing period is held. When the current control transistor 404 is turned on in the writing period, the potential of the video signal is held by the capacitor 405, so that supply of current to the light-emitting element 401 is maintained. On the other hand, when the current control transistor 404 is turned off in the writing period, the potential of the video signal is held by the capacitor 405, so that no current is supplied to the light-emitting element 401.

  Since the current control transistor 404 operates in a linear region, its source-drain voltage (drain voltage) Vds is very small with respect to the voltage Vel applied to the light emitting element, and is slightly smaller than the gate-source voltage (gate voltage) Vgs. Such fluctuations do not affect the current flowing through the light emitting element 401. Since the driving transistor 403 operates in the saturation region, the drain current is not changed by the drain voltage Vds but is determined only by Vgs. For this reason, the current control transistor 404 only selects whether or not current is supplied to the light emitting element 401, and the value of the current flowing through the light emitting element 401 is determined by the driving transistor 403 operating in the saturation region. . Therefore, a change in the current flowing through the light-emitting element 401 can be achieved without increasing the capacitance of the capacitor 405 provided between the gate and the source of the current control transistor 404 or suppressing the off-state current of the switching transistor 402 to be low. Can be suppressed. In addition, by operating the driving transistor 403 in the saturation region, the drain current value is kept relatively constant even when Vds decreases instead of Vel increasing as the light emitting element 401 deteriorates. Accordingly, a reduction in luminance can be suppressed even when the light-emitting element 401 is deteriorated.

  Further, the drive transistor L may be longer than W, and the current control transistor L may be equal to or shorter than W. More preferably, the ratio of L to W of the driving transistor is 5 or more. With the above structure, variation in luminance of the light-emitting element between pixels due to a difference in characteristics of the driving transistor can be suppressed.

  In order to achieve white balance, the gate potential of the driving transistor 403 may be changed for each of R, G, and B. In the case where the gate potential of the driving transistor 403 may be the same for all pixels, the second power supply line is formed in parallel with the scan line, and the pixel sharing the scan line is the second power supply line. May also be shared.

(Embodiment 3)
In this embodiment, a mode different from that in FIG. 4A of a pixel included in the light-emitting device of the present invention will be described.

  4B includes a light-emitting element 411, a switching transistor 412, a driving transistor 413, a current control transistor 414, and a transistor for erasing the potential of a written video signal (erasing transistor). Transistor) 416. In addition to the above elements, a capacitor 415 may be provided in the pixel. The driving transistor 413 and the current control transistor 414 have the same polarity. In the present invention, the driving transistor 413 is operated in the saturation region, and the current control transistor 414 is operated in the linear region. Further, L of the driving transistor 413 may be longer than W, and L of the current control transistor 414 may be equal to or shorter than W. More preferably, the ratio of L to W of the driving transistor 413 is 5 or more.

  The driving transistor 413 may be an enhancement type transistor or a depletion type transistor.

  The gate of the switching transistor 412 is connected to the first scanning line Gaj (j = 1 to y). One of the source and the drain of the switching transistor 412 is connected to the signal line Si (i = 1 to x), and the other is connected to the gate of the current control transistor 414. The gate of the erasing transistor 416 is connected to the second scanning line Gbj (j = 1 to y), and one of the source and the drain is connected to the first power supply line Vi (i = 1 to x). Is connected to the gate of the current control transistor 414. The gate of the driving transistor 413 is connected to the second power supply line Wi (i = 1 to x). In the driving transistor 413 and the current control transistor 414, the current supplied from the first power supply line Vi (i = 1 to x) is used as the drain current of the driving transistor 413 and the current control transistor 414. Are connected to the first power supply line Vi (i = 1 to x) and the light emitting element 411. In this embodiment mode, the source of the current control transistor 414 is connected to the first power supply line Vi (i = 1 to x), and the drain of the driving transistor 413 is connected to the pixel electrode of the light emitting element 411. Note that the source of the driving transistor 413 may be connected to the first power supply line Vi (i = 1 to x), and the drain of the current control transistor 414 may be connected to the pixel electrode of the light emitting element 411.

  The light emitting element 411 includes an anode, a cathode, and an electroluminescent layer provided between the anode and the cathode. When the anode is connected to the driving transistor 413 as shown in FIG. 4B, the anode is a pixel electrode and the cathode is a counter electrode. A potential difference is provided between the counter electrode of the light emitting element 411 and each of the first power supply lines Vi (i = 1 to x) so that a forward bias current is supplied to the light emitting element 411.

  One of the two electrodes of the capacitor 415 is connected to the first power supply line Vi (i = 1 to x), and the other is connected to the gate of the current control transistor 414.

  In FIG. 4B, the driving transistor 413 and the current control transistor 414 are p-channel transistors, and the drain of the driving transistor 413 and the anode of the light-emitting element 411 are connected. Conversely, if the driving transistor 413 and the current control transistor 414 are n-channel transistors, the source of the driving transistor 413 and the cathode of the light emitting element 411 are connected. In this case, the cathode of the light emitting element 411 is a pixel electrode, and the anode is a counter electrode.

  The operation of the pixel illustrated in FIG. 4B can be described by being divided into a writing period, a holding period, and an erasing period. The operations of the switching transistor 412, the driving transistor 413, and the current control transistor 414 in the writing period and the holding period are similar to those in FIG.

  In the erasing period, the second scanning line Gbj (j = 1 to y) is selected and the erasing transistor 416 is turned on, and the potentials of the first power supply lines V1 to Vx are used for current control via the erasing transistor 416. Provided to the gate of transistor 414. Accordingly, since the current control transistor 414 is turned off, a state where no current is forcibly supplied to the light-emitting element 411 can be created.

  In this example, an example of a structure of a light-emitting element used for the display device of the present invention will be described.

FIG. 5A schematically illustrates a cross-sectional structure of a light-emitting element included in the light-emitting device of the present invention. As the structure of the element, copper phthalocyanine (CuPc) is used as the hole injection layer 502 and 4,4′-bis [N- (1- (1)] is used as the first light emitting layer 503 on the anode 501 formed of ITO which is a transparent conductive film. Naphthyl) -N-phenyl-amino] -biphenyl (abbreviation α-NPD), 4,4′-N, N′-dicarbazolyl-biphenyl (abbreviation CBP) as a guest material as the second light-emitting layer 504, and host material A cathode 507 made of Pt (ppy) acac, BCP as the electron transport layer 505, and CaF ₂ and Al as the electron injection layer 506 is laminated in this order. Pt (ppy) acac is represented by the following structural formula 1.

  In the present invention, double-sided light emission can be realized by making the cathode 507 thin enough to transmit light, specifically about 20 nm thick.

  In the second light-emitting layer 504 of the light-emitting element illustrated in FIG. 5A, CBP that is a phosphorescent material is dispersed as a guest material in Pt (ppy) acac that is a host material at a concentration of 10 wt% or more. The phosphorescent light emission and the light emission from the excimer state of the phosphorescent material are emitted together. Specifically, it is preferable that the phosphorescent material emits light having two or more peaks in a region of 500 nm to 700 nm, and one of the two or more peaks is excimer light emission. The first light-emitting layer 503 exhibits blue light emission in which the maximum peak of the light emission spectrum is located in the region of 400 nm or more and 500 nm or less, and the blue light emission is mixed with the light emission from the second light-emitting layer, so that the color purity is more zero. White light close to can be obtained. Further, since only one kind of material to be doped is used, stable white light can be supplied without changing the shape of the emission spectrum even when the current density is changed or when it is continuously driven. Note that the first light-emitting layer may have a structure in which a guest material that emits blue light and has a maximum peak of an emission spectrum in a region of 400 nm to 500 nm is dispersed in a host material.

Next, FIG. 5B schematically shows a cross-sectional structure of the light-emitting element included in the light-emitting device of the present invention, which is different from that in FIG. As a structure of the element, on the anode 511 formed of ITO which is a transparent conductive film, polythiophene is used as the hole injection layer 512, and N, N′-bis (3-methylphenyl) -N, N ′ is used as the hole transport layer 513. -Diphenyl-1,1'-biphenyl-4,4'-diamine (abbreviated as TPD), rubrene as a guest material as the first light-emitting layer 514, TPD as the host material, and coumarin as a guest material as the second light-emitting layer 515 6. A cathode 516 made of Alq ₃ which is a host material and Al is laminated in order.

  In FIG. 5B as well, white double-sided light emission can be realized by making the cathode 516 thin enough to transmit light, specifically, about 20 nm thick.

Next, FIG. 5C schematically illustrates a cross-sectional structure of the light-emitting element included in the light-emitting device of the present invention, which is different from that in FIG. As the structure of the element, on the anode 521 formed of ITO which is a transparent conductive film, the HIM 34 as the hole injection layer 522, the tetraallyl benzidine derivative as the hole transport layer 523, and the naphthacene derivative as the guest material as the first light emitting layer 524 A tetraallylbenzidine derivative and a phenylanthracene derivative as a host material, a styrylamine derivative as a guest material as the second light-emitting layer 525, a tetraallylbenzidine derivative and a phenylanthracene derivative as a host material, a phenylanthracene derivative as the electron transport layer 526, Alq _{3 is} stacked as the electron injection layer 527, CsI is stacked as the first cathode 528, and MgAg is stacked as the second cathode 529 in this order.

  In FIG. 5C as well, when the total thickness of the first cathode 528 and the second cathode 529 is thin enough to transmit light, specifically about 20 nm, white double-sided light emission. Can be realized.

  Note that the stacked structure of the light-emitting elements in this embodiment is not limited to the structure shown in FIG. In order to obtain light from the cathode side, there is a method of using ITO whose work function is reduced by adding Li in addition to the method of reducing the film thickness. The light-emitting element used in the present invention may be configured so that light is emitted from both the anode side and the cathode side.

  In this example, one example of a pixel of the light-emitting device of the present invention described in Embodiment Mode 1 is described.

  FIG. 6A shows a circuit diagram of the pixel of this embodiment. In FIG. 6A, reference numeral 601 denotes a switching transistor. The gate of the switching transistor 601 is connected to the scanning line Gj (j = 1 to y). One of the source and the drain of the switching transistor 601 is connected to the signal line Si (i = 1 to x), and the other is connected to the gate of the driving transistor 602. One of the source and the drain of the driving transistor 602 is connected to the power supply line Vi (i = 1 to x), and the other is connected to the pixel electrode of the light emitting element 603.

  The light emitting element 603 includes an anode, a cathode, and an electroluminescent layer provided between the anode and the cathode. In the case where the anode is connected to the source or drain of the driving transistor 602, the anode serves as a pixel electrode and the cathode serves as a counter electrode. Conversely, when the cathode is connected to the source or drain of the driving transistor 602, the cathode serves as the pixel electrode and the anode serves as the counter electrode. Note that in the case where the source or the drain of the driving transistor 602 is connected to the anode of the light-emitting element 603, the driving transistor 602 is preferably a p-channel transistor. In the case where the source or drain of the driving transistor 602 is connected to the cathode of the light emitting element 603, the driving transistor 602 is preferably an n-channel transistor.

  A voltage is applied from the power source to the counter electrode of the light emitting element 603 and the power supply line Vi. The voltage difference between the counter electrode and the power supply line is maintained at such a value that a forward bias voltage is applied to the light emitting element when the driving transistor is turned on.

  One of two electrodes of the capacitor 604 is connected to the power supply line Vi, and the other is connected to the gate of the driving transistor 602. The capacitor 604 is provided to hold the gate voltage of the driving transistor 602 when the switching transistor 601 is in a non-selected state (off state). Note that FIG. 6A illustrates a structure in which the capacitor 604 is provided; however, the present invention is not limited to this structure, and the capacitor 604 may not be provided.

  When the switching transistor 601 is turned on by the potential of the scanning line Gj, the potential of the video signal input to the signal line Si is applied to the gate of the driving transistor 602. The gate voltage (voltage difference between the gate and the source) of the driving transistor 602 is determined according to the potential of the input video signal. Then, the drain current of the driving transistor 602 that flows according to the gate voltage is supplied to the light-emitting element 603, and the light-emitting element 603 emits light by the supplied current.

  Next, FIG. 6B illustrates a structure of a pixel which is different from that in FIG. In FIG. 6B, reference numeral 611 denotes a switching transistor. The gate of the switching transistor 611 is connected to the first scanning line Gaj (j = 1 to y). One of the source and the drain of the switching transistor 611 is connected to the signal line Si (i = 1 to x), and the other is connected to the gate of the driving transistor 612. The gate of the erasing transistor 614 is connected to the second scanning line Gbj (j = 1 to y). One of the source and the drain of the erasing transistor 614 is connected to the power supply line Vi (i = 1 to x), and the other is connected to the gate of the driving transistor 612. One of a source and a drain of the driving transistor 612 is connected to the power supply line Vi, and the other is connected to a pixel electrode included in the light emitting element 613.

  The light-emitting element 613 includes an anode, a cathode, and an electroluminescent layer provided between the anode and the cathode. In the case where the anode is connected to the source or drain of the driving transistor 612, the anode serves as a pixel electrode and the cathode serves as a counter electrode. Conversely, when the cathode is connected to the source or drain of the driving transistor 612, the cathode serves as the pixel electrode and the anode serves as the counter electrode. In the case where the anode is a pixel electrode, the driving transistor 612 is preferably a p-channel transistor. In the case where the cathode is a pixel electrode, the driving transistor 612 is preferably an n-channel transistor. A voltage is applied to the counter electrode of the light emitting element 613 and the power supply line Vi from the power supply. The voltage difference between the counter electrode and the power supply line is maintained at such a value that a forward bias voltage is applied to the light emitting element when the driving transistor is turned on.

  One of the two electrodes of the capacitor 615 is connected to the power supply line Vi, and the other is connected to the gate of the driving transistor 612. The capacitor 615 is provided to hold the gate voltage of the driving transistor 612 when the switching transistor 611 is in a non-selected state (off state). Note that FIG. 6B illustrates a structure in which the capacitor 615 is provided; however, the present invention is not limited to this structure, and the capacitor 615 may not be provided.

  When the switching transistor 611 is turned on by the potential of the first scanning line Gaj, the potential of the video signal input to the signal line Si is applied to the gate of the driving transistor 612. The gate voltage (voltage difference between the gate and the source) of the driving transistor 612 is determined according to the potential of the input video signal. Then, the drain current of the driving transistor 612 that flows according to the gate voltage is supplied to the light-emitting element 613, and the light-emitting element 613 emits light by the supplied current.

  Further, when the erasing transistor 614 is turned on by the potential of the second scanning line Gbj, the potential of the power supply line Vi is applied to both the gate and the source of the driving transistor 612, so that the driving transistor 612 is turned off, and the light emitting element The light emission 613 is forcibly terminated.

  Note that when the pixels shown in FIG. 6 are used, the video signal may be analog or digital. In the case of digital, gradation can be displayed by controlling a light emission period (light emission period) of the light emitting element. However, the light-emitting element illustrated in FIG. 5A is advantageous for analog driving because the shape of the emission spectrum does not change even when the current density is changed and stable white light can be supplied. It can be said.

  Note that the structure shown in this embodiment is an example of the light-emitting device of the present invention, and the present invention is not limited to this structure. In FIG. 6, the video signal is input by voltage, but the present invention can also be used for a light-emitting device that inputs video signal by current.

  A cross-sectional structure of a pixel of the light-emitting device of the present invention will be described with reference to FIG. In FIG. 7, the transistor 6001 is formed over the substrate 6000. The transistor 6001 is covered with a first interlayer insulating film 6002, and is electrically connected to the transistor 6001 through a contact hole with a color filter 6003 formed of resin or the like over the first interlayer insulating film 6002. A wiring 6004 is formed.

  A second interlayer insulating film 6005 is formed on the first interlayer insulating film 6002 so as to cover the color filter 6003 and the wiring 6004. Note that the first interlayer insulating film 6002 or the second interlayer insulating film 6005 can be formed using a single layer or a stacked layer of silicon oxide, silicon nitride, or silicon oxynitride films by a plasma CVD method or a sputtering method. . A film in which a silicon oxynitride film having a higher oxygen molar ratio than nitrogen is stacked over a silicon oxynitride film having a higher nitrogen molar ratio than oxygen is used as the first interlayer insulating film 6002 or the second interlayer insulating film 6005. It may be used as Alternatively, an organic resin film may be used as the first interlayer insulating film 6002 or the second interlayer insulating film 6005, or an insulating film including a Si—O—Si bond (hereinafter referred to as a starting material) that is formed using a siloxane-based material as a starting material. Or a siloxane-based insulating film) may be used. The siloxane insulating film may have at least one of fluorine, an alkyl group, and aromatic hydrocarbon in addition to hydrogen as a substituent.

  Over the second interlayer insulating film 6005, a wiring 6006 electrically connected to the wiring 6004 through a contact hole and an anode 6007 electrically connected to the wiring 6006 are formed. The anode 6007 is formed at a position overlapping the color filter 6003 with the second interlayer insulating film 6005 interposed therebetween.

  Further, an organic resin film 6008 used as a partition is formed over the second interlayer insulating film 6005. The organic resin film 6008 has an opening, and the anode 6007, the electroluminescent layer 6009, and the cathode 6010 overlap with each other in the opening to form a light-emitting element 6011. The electroluminescent layer 6009 has a structure in which a light emitting layer alone or a plurality of layers including a light emitting layer are stacked. Note that a protective film may be formed over the organic resin film 6008 and the cathode 6010. In this case, the protective film is a film that is less likely to transmit a substance that causes deterioration of the light emitting element such as moisture and oxygen as compared with other insulating films. Typically, it is desirable to use, for example, a DLC film, a carbon nitride film, a silicon nitride film formed by an RF sputtering method, or the like. In addition, the above-described film that hardly transmits a substance such as moisture or oxygen and a film that easily allows a substance such as moisture or oxygen to pass through can be stacked to be used as a protective film.

The organic resin film 6008 is heated in a vacuum atmosphere in order to remove adsorbed moisture, oxygen, and the like before the electroluminescent layer 6009 is formed. Specifically, heat treatment is performed in a vacuum atmosphere at 100 ° C. to 200 ° C. for about 0.5 to 1 hour. Desirably, it is 3 × 10 ⁻⁷ Torr or less, and if possible, it is most desirably 3 × 10 ⁻⁸ Torr or less. And when forming an electroluminescent layer after heat-processing to an organic resin film in a vacuum atmosphere, reliability can be improved more by keeping under a vacuum atmosphere until just before film-forming.

  In addition, the end portion of the opening of the organic resin film 6008 may be rounded so that the electroluminescent layer 6009 formed to partially overlap the organic resin film 6008 does not have a hole in the end portion. desirable. Specifically, it is desirable that the radius of curvature of the curve drawn by the cross section of the organic resin film in the opening is about 0.2 to 2 μm.

  With the above structure, coverage of an electroluminescent layer and a cathode to be formed later can be improved, and a short circuit between the anode 6007 and the cathode 6010 in a hole formed in the electroluminescent layer 6009 can be prevented. Further, by relaxing the stress of the electroluminescent layer 6009, defects called shrink, in which a light emitting region is reduced, can be reduced, and reliability can be improved.

  Note that FIG. 7 illustrates an example in which a positive photosensitive acrylic resin is used as the organic resin film 6008. The photosensitive organic resin includes a positive type in which a portion exposed to energy rays such as light, electrons, and ions is removed, and a negative type in which the exposed portion remains. In the present invention, a negative organic resin film may be used. Alternatively, the organic resin film 6008 may be formed using photosensitive polyimide. When the organic resin film 6008 is formed using negative acrylic, an end portion of the opening has an S-shaped cross-sectional shape. At this time, it is desirable that the radius of curvature at the upper end and the lower end of the opening is 0.2 to 2 μm.

  A transparent conductive film can be used for the anode 6007. In addition to ITO, a transparent conductive film in which 2 to 20% zinc oxide (ZnO) is mixed with indium oxide, indium tin oxide containing ITO and silicon oxide, or the like may be used. In FIG. 7, ITO is used as the anode 6007. The anode 6007 may be polished by CMP or wiping using a polyvinyl alcohol-based porous material so that the surface thereof is planarized. Further, after polishing using the CMP method, the surface of the anode 6007 may be subjected to ultraviolet irradiation, oxygen plasma treatment, or the like.

  The cathode 6010 has a thickness enough to transmit light, and other known materials are used as long as the conductive film has a low work function. For example, Ca, Al, CaF, MgAg, AlLi, etc. are desirable. In order to obtain light from the cathode side, there is a method of using ITO whose work function is reduced by adding Li in addition to the method of reducing the film thickness. The light-emitting element used in the present invention may be configured so that light is emitted from both the anode side and the cathode side.

  In actuality, when completed up to FIG. 7, packaging is performed with a protective film (laminate film, ultraviolet curable resin film, etc.) or a light-transmitting cover material 6012 that is highly airtight and less degassed so as not to be exposed to the outside air. (Encapsulation) is preferable. At that time, if the inside of the cover material is made an inert atmosphere or a hygroscopic material (for example, barium oxide) is arranged inside, the reliability of the OLED is improved. In the present invention, a color filter 6013 is provided on the cover material 6012.

  Note that the present invention is not limited to the manufacturing method described above, and can be manufactured using a known method.

  In this example, the structure of the light-emitting device of the present invention will be described. FIG. 8A shows a block diagram of the light emitting device of this embodiment. A light-emitting device illustrated in FIG. 8A controls a pixel portion 801 including a plurality of pixels each including a light-emitting element, a scan line driver circuit 802 that selects each pixel, and input of a video signal to the selected pixel. A signal line driver circuit 803.

  In FIG. 8A, the signal line driver circuit 803 includes a shift register 804, a level shifter 805, and a buffer 806. A clock signal (CLK), a start pulse signal (SP), and a switching signal (L / R) are input to the shift register 804. When the clock signal (CLK) and the start pulse signal (SP) are input, a timing signal is generated in the shift register 804 and input to the level shifter 805. Further, the order of appearance of the pulses of the timing signal is switched by the switching signal (L / R).

  The level of the timing signal is adjusted by the level shifter 805, and the timing signal is input to the buffer 806. The buffer 806 samples a video signal in synchronization with a pulse of the input timing signal and inputs the sampled video signal to the pixel portion 801 through a signal line.

  Next, the configuration of the scan line driver circuit 802 is described. The scan line driver circuit 802 includes a shift register 807 and a buffer 808. In some cases, a level shifter may be provided. In the scan line driver circuit 802, when the clock CLK and the start pulse signal SP are input to the shift register 807, a selection signal is generated. The generated selection signal is buffered and amplified in the buffer 808 and supplied to the corresponding scanning line. The gate of the transistor of the pixel for one line is connected to the scanning line. Since the transistors of the pixels for one line must be turned on all at once, a buffer 808 that can flow a large current is used.

  Instead of the shift registers 804 and 806, another circuit capable of selecting a signal line such as a decoder circuit may be used.

  The signal line driver circuit for driving the light-emitting device of the present invention is not limited to the structure shown in this embodiment.

  In this example, the structure of the light-emitting device of the present invention will be described. FIG. 8B is a block diagram of the light emitting device of this embodiment. A light-emitting device illustrated in FIG. 8B controls a pixel portion 811 including a plurality of pixels each including a light-emitting element, a scan line driver circuit 812 that selects each pixel, and input of a video signal to the selected pixel. And a signal line driver circuit 813.

  In FIG. 8B, the signal line driver circuit 813 includes a shift register 814, a latch A 815, and a latch B 816. A clock signal (CLK), a start pulse signal (SP), and a switching signal (L / R) are input to the shift register 814. When the clock signal (CLK) and the start pulse signal (SP) are input, a timing signal is generated in the shift register 814. Further, the order of appearance of the pulses of the timing signal is switched by the switching signal (L / R). The generated timing signal is sequentially input to the first-stage latch A815. When a timing signal is input to the latch A815, video signals are sequentially written and held in the latch A815 in synchronization with the pulse of the timing signal. In this embodiment, video signals are sequentially written in the latch A 815, but the present invention is not limited to this configuration. A plurality of stages of latches A815 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 for every four stages, it is said that the driving is divided into four.

  The time until video signal writing to all the latches of the latch A 815 is completed is called a line period. Actually, the line period may include a period in which a horizontal blanking period is added to the line period.

  When one line period ends, a latch signal (Latch Signal) is supplied to the second-stage latch B816, and the video signals held in the latch A815 in synchronization with the latch signal are simultaneously written to the latch B816, Retained. In the latch A 815 that has finished sending the video signal to the latch B 816, the next video signal is sequentially written in synchronization with the timing signal from the shift register 814 again. During the second line period, the video signal written and held in the latch B 816 is input to the pixel portion 811 through the signal line.

  Instead of the shift register 814, another circuit that can select a signal line such as a decoder circuit may be used.

  The signal line driver circuit for driving the light emitting device of the present invention is not limited to the structure shown in this embodiment.

  Next, switching of the scanning direction and the video signal when switching the display from one surface to the other surface will be described.

  In general, in a light-emitting panel in which a plurality of pixels are arranged in a matrix, pixels are selected row by row and a video signal is input. A driving method in which video signals are sequentially input to selected one row of pixels is referred to as dot sequential driving. A driving method in which video signals are simultaneously input to all pixels in one row is called line sequential driving. In any driving method, the video signal input to each pixel always has image information corresponding to the pixel.

  FIG. 9A shows a plurality of pixels provided in a matrix on the light-emitting panel and image information (D1 to D35) input to each pixel. Further, it is assumed that the light-emitting panel shown in FIG. 9A is dot-sequentially driven, and the scanning direction of the scanning line is the row scanning direction, and the order of the pixels to which the video signal is input is indicated by a solid line arrow. A broken line arrow indicates the scanning direction.

  FIG. 9B illustrates a state where the light-emitting panel illustrated in FIG. 9A is viewed from the opposite side. In FIG. 9A, the column scanning direction is from right to left, whereas on the opposite surface, the column scanning direction is from left to right as shown in FIG. 9B. ing. Therefore, the order in which video signals are input in one row of pixels is reversed.

  Therefore, when switching the screen to be displayed, it is necessary to take either means of switching the column scanning direction to the opposite, or changing the image information included in the video signal so as to be horizontally reversed in accordance with the column scanning direction. There is.

  Note that when the image information is switched so as to be reversed left and right, the configuration of the drive circuit can be simplified. In addition, when switching the column scanning direction to the opposite direction, the configuration of the controller that processes the video signal in accordance with the scanning direction of the light emitting panel can be simplified, and the burden on the controller during driving can be further reduced. Can do.

  For example, it is assumed that the light emitting panel is inverted in the row scanning direction in order to display an image on the opposite surface of the light emitting panel. At this time, on the opposite surface, as shown in FIG. 9C, the row scanning direction is in the direction opposite to that in FIG. Therefore, the order in which video signals are input in the pixels in one row is reversed. Also in this case, as in the case of FIG. 9B, either the row scanning direction is switched to the opposite direction, or the image information included in the video signal is changed so as to be vertically inverted in accordance with the row scanning direction. It is necessary to take.

  In this embodiment, the case of dot sequential driving has been described. Similarly, in the case of line sequential driving, when switching the screen, the scanning direction is switched, or the image information included in the video signal is shifted left and right or up and down. Just reverse it.

  In this embodiment, a specific structure of a signal line driver circuit having a function of switching a scanning direction and a scanning line driver circuit will be described.

  FIG. 10 shows a circuit diagram of the signal line driver circuit of this embodiment. The signal line driver circuit shown in FIG. 10 corresponds to an analog video signal. In FIG. 10, reference numeral 1201 denotes a shift register, which generates a timing signal that determines the timing for sampling a video signal by using a clock signal CK, an inverted clock signal CKb obtained by inverting the clock signal CK, and a start pulse signal SP.

  The shift register 1201 is provided with a plurality of flip-flops 1210 and a plurality of transmission gates 1211 and 1212 corresponding to each flip-flop 1210. The switching of the transmission gates 1211 and 1212 is controlled by a switching signal L / R, and when one is on, the other is off.

  When the transmission gate 1211 is on, the start pulse signal is supplied to the leftmost flip-flop 1210, so that it functions as a right shift type shift register. Conversely, when the transmission gate 1212 is on, the start pulse signal is supplied to the rightmost flip-flop 1210, so that it functions as a left shift type shift register.

  The timing signal generated by the shift register 1201 is buffered and amplified by a plurality of inverters 1202 and sent to the transmission gate 1203. In FIG. 10, only one of the outputs of the shift register is shown with a subsequent circuit (in this case, an inverter 1202 and a transmission gate 1203), but actually, a plurality of subsequent circuits corresponding to other outputs are provided. ing.

  The transmission of the transmission gate 1203 is controlled by a buffered timing signal. When the transmission gate 1203 is on, the video signal is sampled and supplied to each pixel in the pixel portion. When the shift register 1201 functions as a right shift type, the column scanning direction is from left to right, and when the shift register 1201 functions as a left shift type, the column scanning direction is from right to left. I'm heading.

  Next, FIG. 11 shows a circuit diagram of the signal line driver circuit of this embodiment. The signal line driver circuit shown in FIG. 11 corresponds to a digital video signal. In FIG. 11, reference numeral 1301 denotes a shift register, which has the same configuration as the shift register 1201 shown in FIG. 10, and switching of the scanning direction is controlled by a switching signal L / R.

  The timing signal generated in the shift register 1301 is buffered and amplified in the inverter 1302 and then input to the latch 1303. In FIG. 11, only the output of the shift register 1301 is shown as a subsequent circuit (in this case, an inverter 1302, a latch 1303, and a latch 1304), but in reality, a subsequent circuit corresponding to another output is shown. A plurality are provided.

  A latch 1303 latches the video signal according to the timing signal. Although only one latch 1303 is shown in FIG. 11, a plurality of latches 1303 are actually provided, and video signals are sequentially latched according to the timing signal. The order of the latches can be switched from left to right latch 1303 or from right to left latch 1303 by a switching signal L / R.

  When the video signals are latched in all the latches 1303, the video signals held in the latches 1303 are simultaneously sent to the subsequent latch 1304 and latched according to the latch signal LAT and its inverted signal LATb. Then, the video signal latched in the latch 1304 is supplied to the corresponding pixel.

  Next, FIG. 12 shows a circuit diagram of the scanning line driving circuit of this embodiment. In FIG. 12, reference numeral 1401 denotes a shift register, which has the same configuration as the shift register 1201 shown in FIG. 10, and switching of the scanning direction is controlled by a switching signal L / R. However, the timing signal generated in the shift register 1401 is used to select pixels in each row.

  The timing signal generated in the shift register 1401 is buffered and amplified in the inverter 1402 and then input to the pixel. In FIG. 12, only one of the outputs of the shift register 1401 shows a subsequent circuit (in this case, an inverter 1402), but actually, a plurality of subsequent circuits corresponding to other outputs are provided.

  Note that the driver circuit described in this embodiment is an embodiment of a driver circuit that can be used in the light-emitting device of the present invention, and the present invention is not limited to this.

  FIG. 13A illustrates a structure of a mobile phone which is one of the electronic devices of the present invention. A cellular phone module illustrated in FIG. 13A includes a printed wiring board 930, a controller 901, a CPU 902, a memory 911, a power supply circuit 903, an audio processing circuit 929, a transmission / reception circuit 904, a resistor, a buffer, a capacitor, and the like. These elements are mounted. In addition, the light emitting panel 900 is mounted on the printed wiring board 930 by the FPC 908. The light-emitting panel 900 includes a pixel portion 905 in which a light-emitting element is provided in each pixel, a scanning line driver circuit 906 that selects a pixel included in the pixel portion 905, and a signal line driver that supplies a video signal to the selected pixel. A circuit 907 is provided.

  The power supply voltage to the printed wiring board 930 and various signals input from the keyboard or the like are supplied via a printed wiring board interface (I / F) 909 in which a plurality of input terminals are arranged. An antenna port 910 for transmitting and receiving signals to and from the antenna is provided on the printed wiring board 930.

  Note that in this embodiment, the printed wiring board 930 is mounted on the light-emitting panel 900 using the FPC 908, but the present invention is not necessarily limited to this configuration. The controller 901, the sound processing circuit 929, the memory 911, the CPU 902, or the power supply circuit 903 may be directly mounted on the light-emitting panel 900 using a COG (Chip on Glass) method.

  Further, in the printed wiring board 930, noise may occur in the power supply voltage or the signal, or the rise of the signal may become dull due to the capacitance formed between the drawn wirings or the resistance of the wiring itself. Therefore, by providing various elements such as a capacitor and a buffer on the printed wiring board 930, it is possible to prevent noise from being applied to the power supply voltage and the signal and the rise of the signal from being slowed down.

  FIG. 13B shows a block diagram of the module shown in FIG.

  In this embodiment, the memory 911 includes a VRAM 932, a DRAM 925, a flash memory 926, and the like. The VRAM 932 stores image data to be displayed on the light-emitting panel 900, the DRAM 925 stores image data or audio data, and the flash memory 926 stores various programs.

  In the power supply circuit 903, a power supply voltage to be supplied to the light emitting panel 900, the controller 901, the CPU 902, the sound processing circuit 929, the memory 911, and the transmission / reception circuit 904 is generated. Depending on the specifications of the light-emitting panel 900, the power supply circuit 903 may be provided with a current source.

  The CPU 902 includes a control signal generation circuit 920, a decoder 921, a register 922, an arithmetic circuit 923, a RAM 924, an interface 935 for the CPU, and the like. Various signals input to the CPU 902 via the interface 935 are once held in the register 922 and then input to the arithmetic circuit 923, the decoder 921, and the like. The arithmetic circuit 923 performs an operation based on the input signal and designates a place to send various commands. On the other hand, the signal input to the decoder 921 is decoded and input to the control signal generation circuit 920. The control signal generation circuit 920 generates a signal including various instructions based on the input signal, and a location designated by the arithmetic circuit 923, specifically, a memory 911, a transmission / reception circuit 904, an audio processing circuit 929, a controller 901, and the like. Send to.

  The memory 911, the transmission / reception circuit 904, the audio processing circuit 929, and the controller 901 operate according to the received commands. The operation will be briefly described below.

  A signal input from the keyboard 931 is sent to the CPU 902 mounted on the printed wiring board 930 via the interface 909. The control signal generation circuit 920 converts the image data stored in the VRAM 932 into a predetermined format according to the signal sent from the keyboard 931, and sends it to the controller 901.

  The controller 901 performs data processing on a signal including image data sent from the CPU 902 in accordance with the specification of the light emitting panel 900 and supplies the processed signal to the light emitting panel 900. In addition, the controller 901 generates an Hsync signal, a Vsync signal, a clock signal CLK, an AC voltage (AC Cont), and a switching signal L / R based on the power supply voltage input from the power supply circuit 903 and various signals input from the CPU. It is generated and supplied to the light emitting panel 900.

  In the transmission / reception circuit 904, signals transmitted / received as radio waves in the antenna 933 are processed. Specifically, high-frequency signals such as isolators, bandpass filters, VCOs (Voltage Controlled Oscillators), LPFs (Low Pass Filters), couplers, and baluns are used. Includes circuitry. A signal including audio information among signals transmitted and received in the transmission / reception circuit 904 is sent to the audio processing circuit 929 in accordance with a command from the CPU 902.

  A signal including audio information sent in accordance with a command from the CPU 902 is demodulated into an audio signal by the audio processing circuit 929 and sent to the speaker 928. The audio signal sent from the microphone 927 is modulated by the audio processing circuit 929 and sent to the transmission / reception circuit 904 in accordance with a command from the CPU 902.

  The controller 901, the CPU 902, the power supply circuit 903, the sound processing circuit 929, and the memory 911 can be mounted as a package of the present invention. The present invention can be applied to any circuit other than a high-frequency circuit such as an isolator, a band pass filter, a VCO (Voltage Controlled Oscillator), an LPF (Low Pass Filter), a coupler, and a balun.

  In this example, a light-emitting device of the present invention using a flexible substrate will be described. In addition to being thin and lightweight, a light-emitting device using a flexible substrate can be used for a display with a curved surface, a show window, or the like. Therefore, the application is not limited to portable devices, and the range of applications is diverse.

  FIG. 14 illustrates a curved light emitting device formed using a flexible substrate. A pixel portion 5002, a scanning line driver circuit 5003, and a signal line driver circuit 5004 are formed over the substrate 5001. A material that can withstand a processing temperature in a later step is used for the substrate 5001.

  Note that various semiconductor elements used for the pixel portion 5002, the scan line driver circuit 5003, and the signal line driver circuit 5004 are not directly formed over the substrate 5001, but once formed on a heat-resistant substrate and then separately prepared. Alternatively, the image may be transferred onto a flexible substrate. In this case, the transfer is performed by a method in which a metal oxide film is provided between the substrate and the semiconductor element, the metal oxide film is weakened by crystallization, the semiconductor element is peeled off, and transferred. A method in which a crystalline silicon film is provided and the amorphous silicon film is removed by laser light irradiation or etching to separate and transfer the substrate and the semiconductor element, or the substrate on which the semiconductor element is formed is mechanically deleted or Various methods such as a method of separating and transferring a semiconductor element from a substrate by removing it by etching with a solution or gas can be used.

  The light-emitting device of the present invention can be used for various electronic devices. However, in particular, in the case of portable electronic devices, usability is dramatically improved by increasing the screen size while reducing the weight and size. It is very useful to use the light emitting device of the present invention. FIG. 15 shows an example of an electronic apparatus of the present invention.

  FIG. 15A illustrates a personal digital assistant (PDA) which includes a main body 2101, a housing 2102, a display portion 2103, operation keys 2104, an antenna 2105, and the like. As shown in FIG. 15A, the display portion 2103 uses the double-sided light emitting device of the present invention. By rotating the housing 2102 around the hinge 2106, the back side of the display portion 2103 is displayed. Can be exposed. Further, a display portion 2107 using another light-emitting device may be provided in a portion overlapping the housing 2102 of the main body 2101.

  FIG. 15B illustrates a cellular phone, which includes a main body 2201, a housing 2202, display portions 2203 and 2204, a voice input portion 2205, a voice output portion 2206, operation keys 2207, an antenna 2208, and the like. In FIG. 15B, the display devices 2203 and 2204 can use the dual emission light-emitting device of the present invention.

  FIG. 15C illustrates an electronic book, which includes a main body 2301, a housing 2302, a display portion 2303, operation keys 2304, and the like. A modem may be incorporated in the main body 2301. The display portion 2303 uses the double-sided light emitting device of the present invention.

  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 configuration shown in Embodiments 1 to 9.

The figure which shows the cross-section of a light-emitting device. FIG. 11 illustrates a structure of a light-emitting device using a polarizing plate. FIG. 14 illustrates a structure of a light-emitting device using a liquid crystal panel. FIG. 6 is a circuit diagram of a pixel of a light-emitting device. FIG. 9 illustrates a cross-sectional structure of a light-emitting element. FIG. 6 is a circuit diagram of a pixel of a light-emitting device. FIG. 14 illustrates a cross-sectional structure of a pixel of a light-emitting device. FIG. 3 is a block diagram illustrating a structure of a light-emitting device. The figure which shows switching of a scanning direction. FIG. 6 is a circuit diagram of a signal line driver circuit. FIG. 6 is a circuit diagram of a signal line driver circuit. FIG. 6 is a circuit diagram of a scanning line driving circuit. The figure which shows the structure of the module of the light-emitting device with which the mobile telephone was equipped. The figure of the light emission panel using the board | substrate which has flexibility. The figure of the electronic device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Light emitting panel 102 Color filter 103 Color filter 104 Polarizing plate 105 Polarizing plate 111 Light emitting panel 112 Color filter 113 Color filter 114 Liquid crystal panel 115 Liquid crystal panel

Claims (13)

A light-emitting element, a first transistor that determines a value of a current flowing through the light-emitting element, a second transistor that selects whether or not the light-emitting element emits light, and either the anode or the cathode side of the light-emitting element A provided color filter, and two polarizing plates existing between the light emitting element and the color filter,
The anode and the cathode have translucency,
The two polarizing plates have different deflection angles.
The light obtained from the light emitting element is white,
The first transistor and the second transistor are electrically connected in series between the light emitting element and a second power source,
The gate of the first transistor is electrically connected to a third power source;
The light emitting device, wherein the first transistor operates in a saturation region and the second transistor operates in a linear region. A light-emitting element; a first transistor that determines a value of a current flowing through the light-emitting element; a second transistor that selects whether the light-emitting element emits light; and two color filters existing between the light-emitting elements And two polarizing plates present with the light emitting element and the two color filters in between,
The anode and the cathode have translucency,
The two polarizing plates have different deflection angles.
The light obtained from the light emitting element is white,
The first transistor and the second transistor are electrically connected in series between the light emitting element and a second power source,
The gate of the first transistor is electrically connected to a third power source;
The light emitting device, wherein the first transistor operates in a saturation region and the second transistor operates in a linear region. A light-emitting panel having a light-emitting element; a first transistor that determines a current value flowing through the light-emitting element; a second transistor that selects whether or not the light-emitting element emits light; Two color filters, and two light-emitting panels and two liquid crystal panels existing between the two color filters.
The anode and the cathode have translucency,
The light obtained from the light emitting element is white,
The first transistor and the second transistor are electrically connected in series between the light emitting element and a second power source,
The gate of the first transistor is electrically connected to a third power source;
The light emitting device, wherein the first transistor operates in a saturation region and the second transistor operates in a linear region. In any one of Claim 1 thru | or 3 ,
The light emitting device is characterized in that the second transistor is electrically connected to the light emitting element through the first transistor. In any one of Claims 1 thru | or 4 ,
The light-emitting device, wherein the first transistor and the second transistor have the same polarity. In any one of Claims 1 thru | or 5 ,
The channel length of the first transistor is longer than the channel width of the first transistor, and the channel length of the second transistor is the same as the channel width of the second transistor or more than the channel width of the second transistor. A light emitting device characterized by being short. In any one of Claims 1 thru | or 6 ,
The light-emitting element includes a first light-emitting layer that emits blue light, a phosphorescent material dispersed in a host material at a concentration of 10 wt% or more, and phosphorescence emission from the phosphorescence material and emission from an excimer state of the phosphorescence material. And a second light emitting layer that emits together. In claim 7 ,
The maximum peak of the emission spectrum from the first light emitting layer is located in a region of 400 nm to 500 nm. In claim 7 or claim 8 ,
The light-emitting device, wherein the phosphorescent material emits light having two or more peaks in a region of 500 nm to 700 nm, and any one of the two or more peaks is excimer light emission. In any one of Claims 1 thru | or 9 ,
The light emitting device is formed on a flexible substrate. In any one of Claims 1 thru | or 10 ,
An electronic apparatus comprising one or a plurality of the light emitting devices. In claim 11 ,
The electronic device is a portable information terminal, a mobile phone, an electronic book, or a display. In claim 12 ,
The display is a display having a curved surface, and the light emitting device provided in the display is formed on a flexible substrate.