JP4149494B2 - Active matrix display device. - Google Patents

Description

  The present invention relates to a display device that performs gradation display by an amount of current, such as an organic electroluminescent element.

  Since the organic light emitting element is a self light emitting element, a backlight required for a liquid crystal display device is unnecessary, and it is expected as a next generation display device from the advantages such as a wide viewing angle.

  Unlike organic light-emitting devices, the light emission intensity of the device and the electric field applied to the device are not proportional, and the light emission intensity of the device and the current density flowing through the device are proportional. In contrast to the variation in signal value, the variation in emission intensity can be reduced by performing gradation display by current control.

  When used in a portable information terminal or the like, low power driving is required because the capacity of the power source is limited. In general, the period of no external input (standby period) is longer than the period of key input operation, telephone call, etc., so devising a method of reducing power consumption in the standby period is to extend the drive time. It can be said that it is effective.

  As a method for this, there is a mode called a partial display mode in which only a part of the screen is displayed in the liquid crystal display device, and as shown in FIG. There is a method in which only the minimum necessary information at the time of standby is displayed in the display area 55a, 55c.

  In some cases, a foldable terminal is also provided with a small display unit that can recognize reception of mail in a closed state. Therefore, as shown in FIG. 22, there is a method in which a hole 61 is provided instead of a small display unit and the display on the display unit 60 is viewed through the hole 61. In this case, the display unit 60 may perform partial display of only 60b.

  Thus, the partial display in the portable information terminal is an indispensable condition for effectively using a limited power source.

  Similarly, in a display device using an organic light emitting element, considering the reduction of power by providing the non-display area 55b, the advantage that the power consumption is almost zero in the non-display state by taking advantage of the characteristics of the organic light emitting element. Devise the system configuration to be used.

  In order to solve the above problems, the active matrix display device of the present invention is characterized in that the power supply voltage or the current flowing through the pixel is reduced in both the display portion and the non-display portion during standby.

  It has a function of applying a reverse voltage from the viewpoint of extending the lifetime at the same time as reducing the current flowing through the non-display pixel.

  In addition, when a portable information terminal is created in a transmissive liquid crystal display device, there is a method of turning off the backlight and reducing power if no key operation is performed for a certain period of time, but also in a display device using an organic light emitting element Similarly, after a certain period, the luminance is lowered to reduce the power.

  As described above, according to the present invention, the current blocking means is provided between the driving transistor for adjusting the current from the EL power supply line and the EL element, and the luminance of the non-display portion does not increase with respect to the current change of the driving transistor. In this way, black display is possible without writing black in non-display rows. As a result, crosstalk in the non-display area can be prevented.

  In addition, the lifetime can be extended by adopting a configuration in which a reverse voltage can be applied to the EL element while the current path between the driving transistor and the EL element is cut off.

  When the number of display colors is small, it is possible to reduce power consumption by changing the method of gradation or lowering the power supply voltage, lowering the brightness after a certain period by a timer, or installing multiple oscillators, The power can be reduced by changing the drive frequency using different oscillators depending on the display color and display area.

  According to the present invention, it is possible to prevent an increase in the black luminance of the non-display portion, extend the life, and reduce the power consumption.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 2 is a block diagram of the display device according to the first embodiment of the present invention.

  A display area storage unit 12 is provided so that the size and position of the display area of the display unit 16 can be changed, and the partial switching unit 13 can select the full screen display mode or the partial display mode.

  The display area storage unit 12 stores the size of the display area designated by the controller 11 and the start line.

  The output of the partial switching unit 13 is input to the source driver 15 and the gate driver 17 so as to change the horizontal scanning period according to the number of display rows, and information on the display area is transmitted.

  Further, the gate driver 17 produces different outputs for non-display lines and display lines.

  For example, as shown in FIG. 3, the display unit 16 has pixels arranged in a matrix, and the configuration of each pixel is formed by one of the pixel configurations shown in FIGS. 1, 4, 5, 6, and 7, for example. Has been.

  In a non-display row, a transistor connected to an EL element among the transistors of each pixel is always in a non-conductive state, whereby a current does not flow through the EL element and a non-light emitting state can be obtained. The operation will be described below using five pixel configurations as an example.

  In FIG. 4, a signal indicating conduction is applied to the gate signal line 1 (22) in one horizontal scanning period of one frame, and the driving transistor 27a is programmed to flow the same current as the current flowing through the source signal line 21. In the remaining period, the gate signal line 1 (22) is turned off, the gate signal line 2 (23) is turned on, and the current flowing through the driving transistor 27a is supplied to the EL element 26. Gradation control is performed by changing the value of the current flowing through the source signal line.

  As shown in FIG. 8, in the partial display in which only a part of the screen is displayed, a current representing black may be supplied to the non-display portion in the above scanning. However, in order to easily form the non-display portion, In the display region, the gate signal line 2 (23) may be turned off during the entire period of one frame so that no current flows through the EL element 26. Similarly, the gate signal line 1 (22) is turned off.

  As a result, a non-conducting signal always flows through the gate signal lines 1 (22) and 2 (23), so that power due to charging and discharging of the stray capacitance existing in the gate signal line is eliminated.

  When black is written in the non-display portion, a current due to the source signal line 21 is small during black writing, and the apparent resistance of the driving transistor 27a is increased. Due to the influence of rounding, it is possible to avoid the problem that a current indicating black can not be sufficiently written, and display with low luminance during black display is possible.

  Even in the luminance change due to the off-leakage current of the transistor generated in the liquid crystal display device, the EL element 26 has a current flowing through the transistor 27d of several nA at most, which is smaller than the current value emitted from the EL element 26. There is an advantage that the luminance does not change with respect to the current.

  In order to perform such display, the gate driver 17 of the present invention is characterized in that it can output as shown in FIG. 9 during partial display.

  In FIG. 9, the non-display rows are from the (i + 1) -th row to the j-th row. During this period, a non-conduction signal is supplied to the gate signal lines 1 and 2, and the other display rows are sequentially scanned.

  In this example, all rows are not selected while selecting the (j + 1) th row, which is the next display row of the ith row, but the horizontal scanning period is changed and the next row of the ith row is changed. Immediately, the (j + 1) th row may be selected.

  An example of a circuit for generating such a gate signal line is shown in FIG. FIG. 10A shows a latch unit 227 using a transfer gate, and FIG. 10B shows a block diagram for outputting each gate signal line.

  The clock cycle is the same as the length of one horizontal scanning period, and the clock A 221a and the clock B 221b are output inverted from each other. The enable signal 222 is high active, and a high level is input to a non-display row and a low level is input to a display row.

  The selection unit 228 selects whether to output the gate signal line from the latch unit 227 or the enable signal 222, and selects the output of the latch unit 227 for the display row and the output based on the enable signal 222 for the non-display row. To do. Note that the output based on the enable signal 222 outputs a level at which the gate signal line 1 and the gate signal line 2 are turned off. If the configuration of FIG. 10B is the same as the number of gate signal lines existing in one pixel, the waveform of FIG. 9 can be realized. In the waveform of FIG. 9, the enable signal 222 is input only to the selection unit 228, and the enable signal of the latch unit 227 is not necessary. On the other hand, when scanning the j + 1th row in the next horizontal scanning period of the ith row, the enable signal 222 of the latch unit 227 is used so that the latch unit 227 of the non-display unit delivers data without latching. do it.

  Note that the circuit shown in FIG. 10 is an example, and the present invention can be implemented as long as the circuit can output such a waveform.

  In FIG. 5, a switching transistor 47e is arranged in parallel with the switching transistor 47d for controlling the connection of current from the driving transistor 47a to the EL element 46, and the EL element 46 is supplied from the reverse bias power line 48 via the switching transistor 47e. 1 shows a pixel configuration in which a voltage can be applied.

  When the switching transistor 47d is a P-type transistor, by making the switching transistor 47e an N-type transistor, when the gate signal line 2 (43) is at a low level, a current flowing through the driving transistor 47a is caused to flow through the EL element 46. At the level, a reverse bias voltage can be applied.

  When a waveform similar to that in FIG. 9 is applied to the gate signal line, the switching transistor 47d is non-conductive and the switching transistor 47e is non-conductive in the non-display row, so that the reverse bias power supply line 48 has a higher potential than the cathode potential of the EL element 46. By applying a low voltage, a reverse voltage can be applied, and the life can be extended. It is known in the literature (Applied Physics Letters, Vol. 69, No. 15, P.2160 to 2162, 1996) that the life is extended by applying a reverse voltage.

  Therefore, the use of the configuration of FIG. 5 has the advantage that the lifetime can be extended in addition to the power reduction and the luminance reduction of the non-display portion in the configuration of FIG.

  As in FIG. 4, FIG. 6 controls the charge of the storage capacitor 84 by the current flowing through the source signal line 81, and controls the current flowing through the driving transistors 87a and 87c, thereby changing the luminance of the EL element 86. This circuit performs gradation display.

  In the display row, the gate signal lines 1 (82), 2 (83), and 3 (88) are as shown in FIG. 11A, and signals indicating the conductive state of the gate signal lines 1 and 2 in one horizontal scanning period. And a current is passed from the source signal line 81 to the storage capacitor 84 (selection period). Next, in a non-conductive state, the charge stored in the storage capacitor 84 is held, a signal indicating the conductive state is output to the gate signal line 3, and a current is passed through the EL element 86 through the switching transistor 87 e.

  On the other hand, in the non-display row, a signal indicating the non-conduction state is output to the three gate signal lines as shown in FIG. 11B, so that the current flowing through the EL element 86 is substantially eliminated, and the non-display state is set.

  Also in this method, when the gate signal line is output to the non-display portion in the same manner as the display portion and a black display current is supplied to the source signal line, the apparent resistance of the driving transistor 87a is large. Since the rounding of the waveform due to the product of the stray capacitance becomes larger than that of the white signal, an incorrect value of charge is accumulated in the storage capacitor 84 without changing a predetermined current value within one horizontal scanning period, thereby causing luminance. There is a problem of rising.

  By adding the gate signal line 3 and the switching transistor 87e according to the present invention and making the switching transistor 87e non-conductive at the time of non-display, the above-mentioned problems can be solved and display with blackened color can be realized. Further, by making it possible to connect a reverse bias power source to the anode electrode of the EL element 86 as in FIG. 5, it is possible to always apply a reverse bias voltage in non-display rows and to prolong the life. .

  FIG. 1 shows the case where the voltage of the source signal line 121 is stored in the storage capacitor 124, and the current flowing through the driving transistor 127a changes depending on the amount of stored charge, and the luminance of the EL element 126 is changed to perform gradation display. It shows a pixel configuration. The present invention is characterized in that a switching transistor 127c is provided.

  In order to form a non-display row in the conventional configuration, it is necessary to store a signal voltage for displaying black at least every 10 frames in the storage capacitor 124. This is because, for example, even if a voltage indicating black is once accumulated in the storage capacitor 124 and the switching transistor 127b is turned off, a leakage current (off-leakage current) flows through the switching transistor 127b even when the switching transistor 127b is turned off. This is because the voltage applied to the capacitor 124 (= the gate voltage of the driving transistor 127a) changes so as to be equal to the voltage of the source signal line 121. Accordingly, when a voltage indicating white is applied to the source signal line 121, the gate potential of the driving transistor 127a gradually changes to a voltage value indicating white due to the leakage current of the switching transistor 127b, and the EL element 126 is identical to white. Since gradation current flows, there arises a problem that the luminance of the non-display portion changes in accordance with the video signal of the display portion.

  In the present invention, switching is performed by inserting the gate signal line 2 (123) and the switching transistor 127c into the current path between the driving transistor 127a and the EL element 126 and making the switching transistor 127c nonconductive in the non-display row. Black display is possible without being affected by the change in the current value of the driving transistor 127a due to the off-leakage current of the transistor 127b. FIG. 12 shows gate signal line waveforms in the display area row and the non-display area row.

  Even if an off-leakage current is generated in the switching transistor 127c, the value is about several nA, and black display is possible. As described above, by adding the switching transistor 127c, it is possible to prevent the display quality from being deteriorated due to the off-leakage current.

  In this pixel configuration as well, as shown in FIG. 13, the switching transistor 237 and the reverse bias power supply line 238 are arranged so that a reverse voltage can be applied to the EL element 126 when the switching transistor 127c is non-conductive. It is possible to extend the life by applying a reverse voltage to. In this configuration, the switching transistors 237 and 127c are simply configured as N-type and P-type, respectively, but may be reversed, and both are N-type or P-type, and the other inverted signal is input to the gate input of one switching transistor. May be included.

  FIG. 7 shows a configuration in which a capacitor 108 is provided and corrected so that the same drain current flows even if the conduction threshold voltage of the driving transistor 107a varies between pixels. The display row is shown in FIG. A current flows through the EL element 106 in accordance with the charge stored in the storage capacitor 104.

  In the non-display row, as shown in FIG. 14B, the gate signal line 3 (108) makes the switching transistor 107d non-conductive so that no current flows through the EL element 106, thereby displaying black in the non-display portion. Can be made.

  Also in this pixel configuration, by providing a transistor operating exclusively with the switching transistor 107d between the EL element 106 and the reverse bias power source, a reverse voltage can be applied to the EL element 106 in the non-display row, The service life can be extended.

(Embodiment 2)
FIG. 15 shows a circuit configuration for realizing low power consumption during partial display.

  The output of the partial switching unit 144 for selecting whether the source driver 146 and the gate driver 147 perform full screen display or display the row stored in the display area storage unit 143 is output to the EL power source unit 145, and the full screen is displayed. The voltage value of the EL power source was changed between display and partial display. The EL power supply unit 145 is connected to an EL power supply line connected to each pixel, and a voltage applied to the EL element is supplied from the EL power supply unit 145 via a driving transistor. Excluding the voltage drop in the driving transistor, a voltage is applied to the EL element 152 as shown in FIG. 16B, and the power supply voltage Vdd (151) is changed by changing the output of the EL power supply unit 145.

  FIG. 16A shows current-luminance (153 (a)) and current-voltage (154) characteristics of a typical EL element. Assuming that the required luminance is up to the maximum Lw, the current flowing in the EL element 152 at that time becomes Iw from the straight line 153 (a), and the voltage applied to the EL element 152 at that time becomes Vw. Accordingly, the voltage necessary for the power supply voltage Vdd (151) is at least Vw, and is about Vdd1 in view of a margin such as variations in EL elements.

  Here, assuming that the power supply voltage Vdd (151) is lowered to Vdd2, no luminance is generated when the voltage applied to the EL element 152 is Vdd2 or higher, and as shown by the one-dot chain line of 153 (b), the luminance exceeds a certain luminance. Even if you raise the value, it does not rise. That is, the gradation near white has almost the same luminance.

  Since only the minimum necessary information is often displayed at the time of partial display, the number of display gradations is 2 to 8 gradations, which is smaller than the maximum displayable gradation number of 64 gradations. The luminance change per key is large, and even if the current-luminance characteristic as indicated by the one-dot chain line of 153 (b) is obtained by adjusting Vdd2, the display is not affected. Further, by adjusting the gradation method necessary for partial display, it is possible to increase the Vdd2 range that does not affect the display. In this way, low power driving can be realized by reducing the power supply voltage.

(Embodiment 3)
When the number of display gradations is smaller in partial display than in full screen display, the amount of change in luminance between gradations is large. This is because, even when the power supply voltage Vdd (151) is Vdd2 in FIG. For example, when the number of display gradations is reduced to a quarter, only a quarter of the gradations have the same luminance. Therefore, even if the current value is lowered as the number of colors is reduced, display deterioration due to the characteristics of the one-dot chain line of 153 (b) is reduced, so that the power supply voltage can be lowered.

  In general, each power supply of a display device is generated by boosting or dropping a certain reference voltage value several times. If the value of the EL power supply value is an integral multiple of the reference voltage value, the power of the entire display device can be used effectively. Therefore, if the voltage value of the power supply voltage Vdd (151) is one of an integral multiple of the reference power supply and a voltage having a smaller magnification than that of the full screen display is used during partial display, the power supply voltage is generated. Therefore, extra power required is reduced, and power consumed by the EL element 152 can be reduced.

(Embodiment 4)
FIG. 17 shows a block diagram and a one-pixel circuit showing a fourth embodiment of the present invention.

  A voltage value corresponding to the data is applied to the source signal line 201 through the digital-analog converter 209 and the output buffer 203 according to the input data. At this time, the maximum voltage value applied to the source signal line is determined by Vref output from the voltage generator 204. The Vdd output from the voltage generator 204 is applied to the EL power supply line 208.

  At the time of partial display, since the necessary minimum information needs to be displayed with as little power as possible, the luminance at the time of white display may be lower than that at the time of full screen display.

  Lowering the luminance requires increasing the source signal line voltage if the voltage of the EL power supply line 208 is equal. On the other hand, even if the EL power supply line 208 and Vref are lowered by the same voltage value, the same luminance can be obtained. If the luminance is reduced, the voltage applied to the EL element 206 is also reduced, and display is possible. In order to reduce the voltage of all the power supplies, the reference power supply V1 input to the voltage generator may be reduced. If the output of the partial switching unit 200a and the data format detection means 200b is used as the control signal input for the reference power supply, the power supply voltage can be changed depending on the size of the display area and the number of colors, etc. When the number is small, the reference power supply V1 can be made the lowest. Thereby, it is possible to realize a display device capable of switching and displaying image quality priority and power priority.

  Note that the data format detection means 200b detects a control bit or packet for the input data. For example, if data is sent as shown in FIG. 18, the content of the color number information 183 is determined. It is possible to identify the number of colors.

(Embodiment 5)
FIG. 19 shows a block diagram according to the sixth embodiment of the present invention. The present invention is characterized by having a plurality of oscillators 161 and a switching circuit 162 and a frequency dividing circuit 163 for selecting one of them.

  The output of the switching circuit 162 and the frequency dividing circuit 163 is controlled by the partial switching unit 167, the oscillation frequency can be changed during full screen display and partial display, and the frame frequency and the horizontal scanning period can be varied.

  Lowering the frame frequency can lower the charge / discharge power of each signal line.

  Further, the frame frequency can be the same, and the horizontal scanning period can be lengthened according to the change in the number of display rows. This is particularly the case when performing gradation display of EL elements according to the current value of the source signal line, for example, in the display device having the pixel configuration of FIG. In contrast to the fact that the time constant due to the product increases and it is difficult to stand up within the horizontal scanning period, increasing the horizontal scanning period by changing the oscillation frequency according to the present invention makes it easy to display a predetermined luminance. It is effective against. Also in the pixel configuration of FIG. 6, since the apparent resistance value of the driving transistor 87a is high, the effect of the present invention can be similarly obtained.

  Generally, the number of display colors is smaller during partial display than during full screen display. In this case, when the frame rate control method (FRC) is used as a gradation display method, the minimum frame frequency at which flicker-free display is possible differs between full screen display and partial display. 80 Hz at the time of screen display (if the display color at the time of full screen display increases, the frame frequency naturally increases). In the present invention, the oscillator 1 (161a) is an oscillator for full-screen display, the oscillator 2 (161b) is an oscillator for partial display, and the optimal oscillation frequency can be used to reduce the frame frequency during partial display. it can.

(Embodiment 6)
When gradation control is performed using the current value of the source signal line, for example, a pixel configuration as shown in FIG. By operating the gate signal line 1 (22), the potential of the contact 28A is changed so that the same current as the current flowing in the source signal line flows in the driving transistor 27a in one horizontal scanning period. At this time, the charge for changing the potential of the contact 28A is supplied through the driving transistor 27a. When the current flowing through the source signal line is several μA or less, the apparent resistance value derived from the current-voltage characteristics of the driving transistor 27a is very large. Therefore, the product of the stray capacitance is large, and the time required for the change is large. 250 μsec or longer. Therefore, there is a problem that gradation display cannot be performed for input data at a frame frequency of 60 Hz with 220 rows.

  As a method for solving this, a current that is X times a predetermined gradation (where X is a natural number of 2 or more) is passed, the apparent resistance value of the driving transistor 27a is lowered, and the change in the source signal line current is reduced. I tried to make it faster. Adjustment to the predetermined luminance was performed by adjusting the pulse width applied to the gate signal line 2 (23) and controlling the period during which current flows through the EL element 26. The waveforms of the source signal line and the gate signal line at this time are shown in FIG.

  In the fifth embodiment in which the horizontal scanning period can be extended during partial display, the time required for changing the current value of the source signal line may be delayed. If the frame frequency is constant, the horizontal scanning period is approximately doubled if the number of display lines is half.

  Here, if the partial display line is approximately one-third or less of the full screen, even if the frame frequency is 60 Hz, one horizontal scanning period is 230 μsec or more. Can be reduced. If one horizontal scanning period is 250 μsec or more, writing may be performed according to a predetermined current. If this method is used, the current value required for writing decreases, and if the current value flowing through the EL element decreases in a certain time, the voltage applied to the EL element also decreases. Therefore, the voltage value applied to the EL power supply line 25 The power consumption can be reduced. For example, when writing with 10 times the current but writing with a predetermined current, the EL power supply voltage was reduced by about 30%, thereby reducing the power consumption by 30%.

(Embodiment 7)
FIG. 21 shows an input data processing unit and a source signal line output unit for carrying out the seventh embodiment of the present invention.

  The feature of the present invention is that the setting of the current value sent to the source signal line can be changed by the conversion table 176 for the data sent from the data RAM 174, and the operation of the conversion table 176 is the timer 175 and the data format detecting means. 173, which can be changed by the output of the partial switching unit 172.

  For example, the timer 175 detects a signal when a button operation is performed on the information terminal shown in FIGS. 8 and 22, and displays the signal with a predetermined luminance after the button operation. , And the method of selecting the current source 177 with respect to the display data value can be changed so as to be narrowed down to 10% to 60% of the predetermined luminance. As a result, a limited power supply is provided by performing gradation display with display priority when an operation is performed by the user, reducing luminance after a certain period of time, and enabling low-power driving by reducing the current value. Can be used effectively.

  In addition, this method can be applied to a power saving mode by using it for a monitor or the like other than a portable information device, and it is useful for global environment conservation because power consumption is reduced.

  The data format detection unit 173 detects input display data and determines the number of colors, a moving image still image, and the like. For example, if data is transmitted as shown in FIG. 18, by detecting the flag part 181 indicating the start of each packet, and further detecting the values of the header part 182, the number of colors 183, and the control signal 184, Judgment is possible.

  The determination result is output to the data RAM 174 and the conversion table 176. In the data RAM 174, based on the output of the data format detection means 173, a method of storing in the RAM according to the number of colors or the like is selected, and a limited capacity can be used effectively.

  On the other hand, in the conversion table 176, the gradation-luminance characteristic can be changed according to the number of display gradations detected by the data format detection means 173. This makes it possible to obtain optimum gradation characteristics for each display gradation.

  In addition, by combining the timer 175 and the data format detection unit 173, when the number of display gradations is small, the user can change the display brightness after a predetermined time when the user looks at the display screen, such as when operating a key. Is possible. For example, as shown in FIG. 23, when four gradation display is performed in a display device capable of displaying 16 gradations, in addition to gradations 0 and 15, two gradations are often used. The gradation is obtained in this way during a key operation or a certain period after the key operation, and after the certain period, for example, a four gradation display of gradations 0 to 3 is performed by the timer 175. If this operation is performed, the maximum current value flowing through the EL element can be reduced from I15 to I3, so that low power driving is possible. Note that since luminance and power are in a trade-off relationship, the method of taking four gradations may be changed according to power and required luminance.

  As another method for reducing power consumption, it can be realized by reducing each current value of the current source 177. A timer 175 and a data format detection means 173 are used as means for determining whether to reduce the current value. In this case, since the maximum luminance can be reduced regardless of the number of display gradations, the power can be reduced.

(Embodiment 8)
In the configuration of FIG. 21, the output of the partial switching unit 172 is sent to the source driver and gate driver as shown in FIG. 2 and also sent to the data RAM 174 and the conversion table 176, thereby effectively utilizing the data RAM 174 area at the time of partial display. be able to. For example, assuming that data for one screen can be stored in the data RAM 174, data for a plurality of screens can be stored according to the display ratio for the entire screen during partial display. This eliminates the need to transfer display data from the outside to the data RAM 174, thereby reducing power consumption.

  Also in the conversion table 176, the current source 177 to be selected can be changed with respect to the same gradation data having the same display gradation number during full screen display and partial display. Settings can be made such that image quality is prioritized during display and power is prioritized during partial display.

  Although not shown in FIG. 21, an external adjustment unit may be provided so that the time setting of the timer 175 and the setting of the conversion table 176 can be adjusted from the outside.

  In any of the embodiments of the present invention, the source driver 71 and the gate driver 70 shown in FIG. 3 may be formed on a glass substrate of a display device using low-temperature polysilicon. Alternatively, the source driver 71 and the gate driver 70 may be formed as semiconductor circuits and combined with the display panel. Alternatively, one driver may be formed of low-temperature polysilicon on the glass substrate of the display device, the other is formed as a semiconductor circuit, and combined with the display panel.

  Further, the driver IC may be mounted in one direction as shown in FIG. Mounting in this way has an advantage that the display unit can be arranged symmetrically with respect to the device as compared with the portable information terminal shown in FIG. 8 or FIG.

  In this example, a P-channel switching element is described as an example of the switching element. However, an N-channel switching element or a combination thereof can be similarly realized. For example, in the case of the pixel configuration shown in FIG. 4, when an N-channel switching element is used as a voltage value to be applied to the gate signal line 1 (22) and the gate signal line 2 (23), considering the logic level, P channel An inversion signal of the signal of the switching element may be input, and the current flowing through the source signal line 21 is reversed, and the voltage supplied from the EL power supply line 25 is set to the lowest potential on the pixel circuit. This is shown in FIG. 25A, and the gate signal line waveform in the non-display row is shown in FIG. The other configurations of FIGS. 1, 6 and 7 in FIG. 4 can also be realized by using N-channel transistors.

  In the present invention, the transistor used as the switching element has been described using a thin film transistor as an example. However, the same effect can be obtained by using a varistor, a thyristor, a ring diode, a thin film diode (TFD, MIM) or the like without being limited to a thin film transistor. can get.

  Further, although an EL element has been described as a display element, an organic electroluminescence element, an inorganic electroluminescence element, a light emitting diode, or the like may be used.

The figure which showed the example which provided the current cutting means between the drive transistor and EL element in the case of the pixel structure which performs gradation control by a source signal line voltage The figure which showed the control signal block required for full screen or partial display switching by the 1st Embodiment of this invention The figure which showed the structure of the display apparatus of this invention The figure which showed one form of the pixel structure which can be applied to this invention The figure which showed the example of the pixel structure which can apply a reverse bias voltage to EL element The figure which showed the pixel structure for implementing this invention in a current mirror pixel structure A diagram showing an example of a pixel configuration in which gradation control is performed using a source signal line voltage and a function for correcting a variation in threshold voltage of a driving transistor is included. The figure which showed the example which applied the partial display in a portable information terminal The figure which showed the waveform of the gate signal line at the time of performing partial display using the pixel structure shown in FIG. 4, and the form of this invention 1 is a block diagram of an example for realizing a gate signal line generation unit according to a first embodiment of the present invention. The figure which showed the waveform of the gate signal line of the display row and non-display row in the current mirror pixel configuration The figure which showed the gate signal line waveform in the case of the pixel structure of FIG. 1 using the form of this invention A diagram showing a pixel configuration in which a reverse voltage can be applied to an EL element when gradation display is performed according to a voltage flowing through a source signal line. FIG. 7 is a view showing gate signal line waveforms of display rows and non-display rows according to the embodiment of the present invention in the circuit configuration of FIG. Block diagram for enabling the EL power supply voltage to be changed depending on the size of the display area The figure which showed the current-voltage-luminance characteristic of EL element The figure which showed the relationship between a reference voltage, a voltage generation part, a voltage output, a source signal line, and a pixel. Figure showing an example of display data input format 1 is a block diagram in which an oscillation frequency that is one embodiment of the present invention can be varied. The figure which showed the application pattern of the source and the gate signal line at the time of full screen display and partial display in Embodiment 6 A diagram that allows different current outputs to be selected for the same input data depending on the number of gradations, the size of the display area, and time The figure which showed the example which performs the partial display in a foldable portable information terminal Diagram showing the relationship between gradation and current value The figure which showed the example which has arrange | positioned the drive semiconductor circuit in the display device Diagram when configured with N-channel transistors

Explanation of symbols

11 Controller 12 Display Area Storage Unit 13 Partial Switching Unit 14 Data RAM
15 Source Driver 16 Display 17 Gate Driver 21 Source Signal Line 22 Gate Signal Line 1
23 Gate signal line 2
24 Storage Capacitor 25 EL Power Line 26 EL Element 27 Transistor 28 Contact 121 Source Signal Line 122 Gate Signal Line 1
123 Gate signal line 2
124 Storage Capacitance 125 EL Power Supply Line 126 EL Element 127 Transistor

Claims (4)

  An active matrix display device having a display screen in which a plurality of pixels are arranged in a matrix, and an organic light emitting element that emits light according to current is arranged for each pixel,
  A source driver that outputs video signals;
  A driving transistor that is formed for each pixel and supplies a current corresponding to the video signal to the organic light emitting element;
  A first switching element formed in a current path of a current flowing through the organic light emitting element;
  A second switching element formed in the video signal path from the source driver to the driving transistor for each pixel;
  A gate driver for turning on and off the first switching element according to display and non-display of the pixel;
A control unit for setting and switching the display area;
Comprising
  A voltage is applied to the pixel via an EL power line,
  The gate driver is configured to receive an enable signal;
  The control unit controls the gate driver and the source driver to switch between full screen display with the entire display screen as a display area and partial display with a part of the display screen as a display area,
In the partial display, the first switching element is made conductive in the display area, and at least the first switching element is set to 1 in an area other than the display area based on an enable signal input to the gate driver. Non-conducting for the entire duration of the frame,
  The active matrix display device, wherein a voltage applied to the EL power supply line in the partial display is lower than a voltage applied to the EL power supply line in the full screen display.   The gate driver includes a selection unit and a latch unit corresponding to a pixel row of the display screen,
  The active matrix display device according to claim 1, wherein the selection unit is configured to receive the enable signal.   The horizontal scanning period for selecting one pixel row is different in the first display region by a first display row number and a second display row number different from the first display row number. Item 6. An active matrix display device according to Item 1.   2. The active matrix display according to claim 1, wherein the magnitude of the video signal output from the source driver circuit is made different between the first display line number and the second display line number displayed on the display screen. apparatus.

Images