JP2000148088A - Drive assembly for organic el display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To embody a drive assembly of an organic display device which may be driven with simple constitution by providing the drive assembly of the organic EL display device which enables gradation control of a sufficiently large number of gradations and the drive assembly of the organic EL display device with which high-grade images are obtainable even when the display having many variations in light emission thresholds is driven. SOLUTION: The drive assembly of the organic EL display device arranged with organic EL elements in a matrix form is constituted as the drive assembly of the organic EL display device which executes the gradation control by varying the number of selection times of data electrodes j1 to j4 without changing the frame frequencies for driving scanning electrodes k1 to k3 among the signals to be impressed to the organic EL elements, thereby varying pulse densities. Namely, the assigning of multiple intensity levels is embodied by repeating the selection and non-selection of the data electrodes during the period when the arbitrary scanning electrodes are selected with the matrix-form display device to be linearly scanned.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device having an emission gradation control function for an organic EL display device in which organic EL elements are arranged in a matrix.

[0002]

2. Description of the Related Art A display device in which self-luminous elements such as a light emitting diode (LED), a laser diode (LD), an inorganic EL element, an organic EL element and the like are arranged in a segment shape, a matrix shape, or a mixture thereof is thin. It is expected as a next-generation display device (display) having features such as high brightness, high viewing angle, and high definition, and has been actively researched and developed for practical use and high performance. The display device,
As a display device having a constant luminance is being put to practical use, if a light emission gradation function can be added, it can be used as a display device corresponding to a multi-tone monochrome image, a color image, and the like.

As technical means for performing gradation display using self-luminous elements such as LEDs, LDs, inorganic EL elements, and organic EL elements, the following three types of methods have been mainly devised.

[0004] 1. Pulse amplitude control method The current driving element can control the instantaneous luminance by the current value, and the voltage driving element can control the instantaneous luminance by the voltage value. Therefore, gradation display can be performed by using the gradation signal as a current value flowing through the element or a voltage applied to the element. (Hereinafter, PHM method) 2. Pulse width modulation method The self-luminous element can change the luminous luminance luminously by the integrated value of the instantaneous luminance per unit time. Therefore, gradation display is possible by setting the gradation signal to the light emission time per unit time. (Hereinafter, PWM method) Pulse number modulation method The self-luminous element can change the luminous luminance luminously by the integrated value of the instantaneous luminance per unit time. Therefore, gradation display is possible by setting the gradation signal to the number of times of light emission per unit time. (Hereinafter, FRM method)

The PHM method is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-636.
As disclosed in Japanese Patent Application Laid-Open No. 91-301, a method of using a current value as a gray-scale signal, and a method of obtaining a gray-scale signal with a voltage applied to an element as disclosed in Japanese Patent Application Laid-Open No. 5-30351 are disclosed. is there. Either method can be applied to an organic EL device in the sense of amplitude modulation.

In driving the organic EL element, there is a problem that the voltage level (threshold) at which the organic EL element starts emitting light has a large variation. That is, at a signal level that gives relatively bright light emission, there is no problem, but at a low signal level that gives dark light emission, the variation in light emission luminance at the same voltage (current) level is enlarged (the visual acuity is less sensitive to dark images). Higher) and image quality is greatly impaired. However, in the case of current driving, it is difficult to stably manufacture an accurate constant current source having a large number of outputs, generally, though not limited thereto. Therefore, the constant current source is more expensive than the constant voltage source, and driving with the constant voltage source is desirable in terms of cost.

The PWM method is disclosed in Japanese Patent Application Laid-Open No. 54-50224, Japanese Patent Application Laid-Open No. 61-117598,
No. 301355. In the PWM method, since the voltage or current is controlled for a duration time, a voltage sufficiently higher than the threshold value or a current can be applied, and the variation in the threshold value depends on the variation in the threshold value as in the PHM method. There is an advantage that a dark image can be obtained with high quality without being performed.

However, the brightness gradation has a minimum pulse width,
Limited by the ratio of the maximum pulse width. For this reason, in the case of moving image display, for example, when the simplest pixels are sequentially scanned one by one, even a normal television image has a size of about 0.25 μm per pixel.
Only s can take the signal time. Therefore, it is difficult to drive this signal with a signal obtained by further dividing the time from the viewpoint of light emission response speed.

Further, when performing gradation display by the PWM method, a driver for directly driving a display panel constituted by light emitting elements is different from a binary driver in that a gradation generation clock signal and a frequency-divided clock signal are generated. A circuit that generates a control signal and a decoder that generates a pulse width of a driving pulse based on the generated control signal are required.

That is, in the case of a conventional driver as shown in FIG. 6, for example, the data electrode driving IC 300a comprises an enable controller 301 and a data controller 3
02, a bidirectional shift register 303, and a latch 304
, A level shifter 305, and a driver 306. The enable controller 301 has terminals EIO1,
The bidirectional shift register 303 is controlled to an enabled state or a disabled state by an enable signal transmitted and received through the EIO2. Data controller 3
02 captures the display data signal transmitted and received via the terminals D0 to D3 and D4 to D7, and provides the display data signal to the bidirectional shift register 303 at a predetermined timing.

The bidirectional shift register 303 has a terminal XS
Data is fetched from the data controller 302 by a control signal input through the CL, and the data shift direction is changed by a control signal input through the terminal SHL. Then, the display data supplied from the data controller 302 is output to a predetermined position of the latch 304. That is, the latch 304 and the level shifter 30
5, the data amount (for example, 80 bits) handled by the driver 306 and the data amount (for example, 8 bits) input from the data controller 302 at one time are different, and the former is much larger. Therefore, the data amount of both is adjusted using a bidirectional shift register. The latch 304 latches an output from the bidirectional shift register 303 in accordance with a latch signal provided via a terminal LP. In addition, the state may be inhibited by a control signal provided from the terminal INH. The level shifter 305 converts the output (voltage) of the decoder 308 into an optimal signal level (voltage) for driving the driver 306. The driver 306
The current or power required to drive the organic EL element is controlled by a signal from the level shifter, and the organic EL element is driven.

The latch 304 and the level shifter 3
A gray scale controller 309 that supplies a gray scale signal to this decoder is connected to a decoder 308 located between the decoder 305 and the decoder 305.

A gray scale controller 309 supplies a gray scale signal supplied via a terminal GCP to a decoder 308 at a predetermined timing. The decoder 308 decodes the applied gray scale signal and controls the time during which the output signal of the latch 304 is applied to the level shifter 305 according to the obtained data. That is,
The output time of the display data signal supplied from the latch 304 to the level shifter 305 is controlled by the gray scale signal, so that the time width (signal width) of the output signal can be controlled.

Therefore, when a data electrode drive signal having a different signal width is provided, a gray scale signal having the signal width may be provided.

As described above, in the conventional PWM method, an inexpensive binary driver having a simple configuration cannot be used. In particular, in the case of an organic EL display device driven by current, there are almost no current drivers capable of performing PWM as described above in commercially available products.

The FRM system is disclosed in Japanese Patent Laid-Open No. 60-129793.
And Japanese Patent Application Laid-Open No. 62-172396. In this method, a frame forming one screen is driven in a time-division manner into a plurality of fields, and a gray scale is obtained by the number of times of light emission per unit time.

However, for example, the frame frequency 6
In the case of driving at 0 Hz, if the display is performed at 4 gradations, and if the driving is not performed at the field frequency of 180 Hz, flicker is noticeable and image quality is significantly impaired. For this reason,
As the number of gradations increases, it is necessary to control the frame of the display device at high speed. Here, like an organic EL element,
When the load is capacitive, it has a time constant, which makes it difficult to control the frame at a particularly high speed.

As a method for solving this problem, a subframe method as described in Japanese Patent No. 85756 and Japanese Patent No. 950837 has been devised. This method realizes multiple gray scales by lowering the frame (field) frequency and changing the pulse width of the drive signal in each field.

However, in this method, since the pulse width of each field of the FRM is different, a false contour phenomenon occurs in a moving image, and the accurate display function is impaired.

As described above, when gradation display is performed by a display device including self-luminous elements such as organic EL elements, the conventional driving method and driving circuit using PHM, PWM, and FRM require accurate luminance adjustment. There are problems that it is difficult, that a sufficient number of gradations cannot be obtained, that the gradation varies depending on the quality of the display device, and that the circuit scale is complicated and expensive.

Further, when the organic EL display device is driven in a time-division manner, the scanning electrode COM1 which is turned on at the time of selection and at the L level is turned off at the time of non-selection, and is returned to the H level at the time of non-selection. The delay time is caused by the time constant given by This delay time overlaps with the selection period of the next scan electrode after the selection of a certain scan electrode, and depending on the condition of the data line, light is emitted for this delay time despite being a non-selected pixel. It will be. Such erroneous light emission deteriorates the contrast or is recognized as abnormal light emission, which significantly reduces the quality of the display and causes image disturbance.

[0022]

SUMMARY OF THE INVENTION An object of the present invention is to provide a driving apparatus for an organic EL display device capable of controlling a sufficiently large number of gradations.

Another object of the present invention is to provide a driving device for an organic EL display device which can obtain a high-quality image even when driving a display having a large variation in light emission threshold.

Another object of the present invention is to realize a driving device for an organic display device which can be driven with a simple configuration.

[0025]

A display device comprising an organic EL element has a relatively high response speed of an organic EL element as a constituent element, and has a pulse width of an applied voltage or a current, in particular, the number of pulses, that is, a unit. Depending on the pulse density per hour,
A gradation display is possible. Therefore, by varying the driving frequency of the data electrode and adjusting the density of the pulse applied to the organic EL element, multi-gradation display can be performed. More specifically, for example, in a matrix-shaped display device that is line-scanned, multi-gradation display can be realized by repeating selection and non-selection of data electrodes during a period in which an arbitrary scanning electrode is selected. Note that the form of the display device is not limited to a matrix.

In the driving method of the present invention, since the gray scale display is realized by the pulse density, the problem that the quality of the gray scale is influenced by the quality of the display device as seen in the PHM system does not occur. .

Further, since the pulse density is controlled not by the pulse width but by the number of pulses, there is no need to provide a multi-stage output as in the PWM method, so that the circuit configuration is simplified and the cost is reduced. Is also possible.

Also, since the number of pulses is varied without dividing the frame frequency into fields, the response speed of the display device (in the case of a capacitive load such as an organic EL element, Since the data electrode capacitance is much smaller than the scan electrode capacitance, the response speed of the scan electrode is slower), so that the problem that a sufficient number of gradations cannot be obtained does not occur.

That is, the above object is achieved by the following constitution. (1) Organic E in which organic EL elements are arranged in a matrix
What is claimed is: 1. A driving device for an L display device, wherein among signals applied to an organic EL element, a pulse density is varied without changing a frame frequency for driving a scanning electrode and gradation control is performed. (2) The organic EL display device according to (1), wherein the organic EL display device has a scanning electrode and a data electrode, and performs gradation control by changing the number of data electrode selections during each scanning electrode selection period of the scanning side electrode. A driving device for an organic EL display device. (3) The driving device for an organic EL display device according to (2), wherein the frame frequency and the driving frequency of the data electrode are different. (4) The driving device for an organic EL display device according to any one of (2) to (3), wherein the driving frequency of the data electrode is higher than the frame frequency. (5) When the number of selections of the data electrode is a plurality of times, the selection of the data electrode is continuously performed.
The driving device for the organic EL display device according to any one of (4). (6) The driving device for an organic EL display device according to (5), wherein the leading pulse width when the data electrodes are continuously selected is wider than the other pulse widths.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION A driving device for an organic EL display device according to the present invention comprises a matrix-shaped, segment-shaped organic EL element,
Or, a driving device of an organic EL display device arranged in a hybrid molding method, wherein among signals applied to the organic EL device, the pulse density applied to the organic EL device without changing the frame frequency for driving the scanning electrode is changed. The gradation is controlled variably.

The pulse density applied to the organic EL device is as follows.
It is determined by the amount and magnitude of the pulse applied to the organic EL element per unit time, and can be considered as an integrated value of the total amount (time amount) of the pulse applied per unit time and its intensity.

That is, it is controlled by the number and width of the voltage and current applied to the organic EL element, in particular, by the number of pulses. In this case, the frame frequency, which is the period of the scanning signal applied to the scanning electrode, is not normally changed. Organic E
In the case of the L element, the response speed is relatively fast, but since it has a capacitance component, the apparent parasitic capacitance particularly on the scanning electrode side increases. Therefore, if the frame frequency is varied in order to perform the gradation control on the scanning electrode side, the high gradation control becomes difficult due to the influence of the capacitance component at the time of driving at a high cycle.

The operation speed of the data electrode can be obtained from the capacitance ratio. For example, when the ratio of the number of scanning electrodes to the number of data electrodes is 3: 4, the capacitance ratio is the aspect ratio 3/4... The capacitance ratio, data electrode / scanning electrode = 3/4. Further, when the screen is divided into upper and lower parts, the capacitance ratio becomes the upper and lower part of the screen.... Further, if it is assumed that data electrodes are provided for each of R, G, and B for color display, the RGB color display,..., The capacitance ratio is ３. Therefore, when driving this display device, the capacitance ratio between the data electrode and the scanning electrode becomes 1/8. Thus, when the other conditions are the same, the driving of the data electrode can be performed at least eight times as fast as the scanning electrode.

Here, in the display device in the driving state, the capacitance component may be negligible. That is, when the next driving is performed in a state where the potential difference between both ends of the organic EL element does not change from the previous driving, or when the organic EL element which is a non-selected element is driven.
When electric charge has already been charged to the capacitance component of the L element, it is not necessary to newly charge the electric charge, so that the capacitance component can be almost ignored. Generally, when the capacitance component cannot be neglected, there is only one element existing at the intersection with the selected scanning electrode in the data electrode, and the scanning electrode is an element existing at the intersection with the non-selected data electrode.
When meaningful data is displayed on the display device, almost no state occurs in which all the organic EL elements corresponding to one selected scanning electrode are turned on in the display device. On the contrary, a state where all the organic EL elements corresponding to one selected scanning electrode are not turned on exists in a normal use state.
Therefore, in practice, it is considered that the capacitance component of the non-selected scanning electrode can be almost ignored. For example, if the data electrode is 10
In a display device having zero lines, the effect of the capacitance component is as small as 1/100 of the data electrode with respect to the scanning electrode, and high speed operation of 100 times at the maximum is possible.

The number of divisions of the signal for driving the data electrode is preferably 2 to 16, more preferably 2 to 64, and particularly preferably 2 to 256. As the frame frequency,
Usually, 60 Hz or more, especially about 60 to 150 Hz is preferable. The driving frequency of the data electrode is determined by the frame frequency and the duty ratio.

Next, the driving device of the organic EL display device of the present invention will be described with reference to the drawings. For example, consider a matrix circuit of scan electrodes k1 to k3 and data electrodes j1 to j3 as shown in FIG. In FIG. 1, a waveform shown on the left side of the matrix circuit is a drive voltage waveform applied to each of the scan electrodes k1 to k3, and a waveform shown below the matrix circuit is a drive voltage waveform applied to the data electrodes j1 to j3. is there.

For example, during a period T1 in which the scanning electrode k1 is selected, pulse trains t11 to t15 corresponding to the gray scale of the display data are continuously applied to the data electrodes j1 to j4.
Perform gradation display. Here, the pulse width applied to the data electrode is simply the scanning electrode k when performing 6-gradation display.
This is a pulse width obtained by dividing one selection period T1 into six equal parts. Then, these pulse trains are given during a period Tc which is a driving cycle of the data electrode.

However, when the pulse widths applied to the data electrodes are equal, the number of divisions of the scanning period increases as the number of gradations increases, so that a high-speed operation of the data electrode driving circuit is required. Therefore, in order to alleviate this, by setting the pulse width to a different width, the data electrode drive frequency can be suppressed to a lower value even when the number of gradations is increased.

For example, as shown in FIG. 2, data electrode driving pulse trains provided during a period Tc which is a driving period of the data electrode are prepared with different pulse widths from t101 to t106. By giving them in combination, it is possible to control a higher gradation even with a small number of divisions. In this case, even if the pulse widths of the respective time divisions are different, since the same width pulse is used for each output (for each data electrode), there is no need to change the pulse width. Unlike the PWM method, the circuit is different from the PWM method. Simple things will be fine.

When there are two or more divided pulses,
Preferably they are applied continuously. For the first pulse, the pulse width may be increased by the time required to charge the capacitance component of the organic EL element. That is, when the number of divisions of the data electrode is increased, the capacitance component of the organic EL element becomes a problem. For example, when a driving waveform as shown in FIG. 3 is considered, the current value does not reach the emission current to charge the capacitance component of the organic EL element during a certain period from the fall of the voltage, and the delay period Td is No light is emitted. However, when two or more divided pulses are applied, they are applied continuously after the first pulse, so that there is no need to charge as described above, and such a delay time does not occur. Therefore, it is only necessary to increase the pulse width of only the first pulse of the continuous pulse train.

Next, the driving device of the present invention will be described in more detail.

As shown in FIG. 4, for example, the drive device of the present invention has main control means 111 for providing data to be displayed on a display and data relating to display. And a display control means 112 for transmitting a scan electrode drive signal and a data electrode drive signal which are signals for driving scan electrodes and data electrodes of the organic EL display. Further, it is connected to the display control means 112, and is used for expanding display data provided from the main control means 111 and the like into matrix data, bitmap data, etc., and display data for storing data of predetermined display contents and the like. The organic EL device is operated by the storage means 113 and the scan electrode drive signal and the data electrode drive signal from the display control means 112.
Scanning electrode driving means 114 for driving the scanning electrodes and data electrodes of the structure (organic EL display main body) 116;
Data electrode driving means 115.

The main control means 111 includes the organic EL structure 11
6, display data to be displayed, or designation of display data stored in the display data storage unit 113,
Gives timing and control data necessary for display.
The control means 111 can be generally constituted by a general-purpose microprocessor (MPU) and a control algorithm on a storage medium (ROM, RAM, etc.) connected to the MPU. The control means 11 includes CISC, RI
It can be used irrespective of the mode of the processor such as SC and DSP, and may be configured by a combination of logic circuits such as ASIC. In this example, the main control unit 111 is provided independently, but the display control unit 112,
It may be integrated with the control means of the device provided with the display.

The display control means 112 analyzes display data and the like provided from the main control means 111 and the like, searches data stored in the display data storage means 113 as necessary, and stores the display data on the organic EL display. Is converted into matrix data to be displayed at a predetermined position. That is, when the image (image or character) data to be displayed is dot data in pixel units of the organic EL element given at the intersection of each matrix, a signal for driving the scanning electrode and the data electrode giving the dot coordinates is provided. appear. In addition, driving in units of frames as described above, driving ratio (duty) control between the scanning electrodes and the data electrodes, and the like are also performed.

The display control means 112 includes, for example,
A processor or a complex logic circuit having a predetermined arithmetic function, a buffer for the processor or the like to exchange data with an external main control unit or the like, a timing signal to a control circuit,
A timing signal generating circuit (oscillation circuit) for giving a display timing signal and reading / writing to external storage means and a writing timing signal, a storage element control circuit for sending and receiving display data and the like from an external storage means, and reading from an external storage element Or a drive signal transmission circuit for transmitting display data, which is supplied from the outside or obtained by processing the data, as a drive signal, and stores data relating to a display function and a display to be externally supplied, control commands, and the like. It can be composed of various registers and the like.

The display data storage means 113 stores data (conversion table) for developing image data supplied from the outside as matrix data on a display,
Data in which predetermined character data and image data are directly expanded into matrix data and the like are stored, and can be read (written) by designating a storage position (address) as necessary.
Such a display data storage means is a RAM (VR
AM), and a semiconductor storage element such as a ROM can be preferably mentioned, but the present invention is not limited to this, and a storage medium using light or magnetism may be used.

The scanning electrode driving means 114 and the data electrode driving means 115 drive the scanning electrodes and the data electrodes according to the scanning electrode driving signal and the data electrode driving signal given from the display control means 112. The organic EL element constituting the organic EL display is a light emitting element that emits light by current driving. Therefore, the scan electrode drive signal and the data electrode drive signal, which are usually given as voltage signals, are converted into signals of a predetermined current value, and the signals are supplied to predetermined scan electrodes and data electrodes for driving. The driving current is usually preferably about 0.001 to 100 mA, particularly preferably about 0.01 to 50 mA. However, if a current suitable for light emission can be obtained, a voltage signal may be given to a predetermined electrode.

More specifically, a scan electrode and a data electrode at predetermined positions are driven by using a voltage-current conversion element having a necessary current capacity, an amplification element (power amplification), or the like. Such a driving circuit includes an open drain, an open collector circuit, a push-pull circuit, and the like. As a voltage-current conversion element or an amplification element,
Although a contact device such as a relay may be used, a transistor, an FET, and a semiconductor element having the same function as these are preferable in consideration of high-speed operation and reliability. These may be integrated circuits such as ICs. These semiconductor elements connect a scan electrode and a data electrode to either the power supply side or the ground side. here,
The power supply side and the ground side include not only a case where the power supply side and the ground side are directly connected to a power supply and a ground line, but also a case where the connection is made via elements such as a current limiting resistor, a protection device, and a regulator.

The organic EL structure 116 is arranged so that a plurality of scanning electrodes and data electrodes intersect, and a specific pixel (organic EL element) is driven by a drive signal applied between these two arbitrary electrodes. Emits light.
The number of scanning electrodes and the number of data electrodes in the matrix portion are appropriately determined depending on the size and definition of the display, but usually the number of scanning electrodes is 1 to 768 and the number of data electrodes is 1 to 1
The number is about 024.

In the present invention, among the above-mentioned circuit components, in particular, in the display control means 112, when forming the drive signals for the scanning electrodes and the data electrodes, the data electrode drive signals are divided into a plurality of pulse signals, It is preferable to perform the gradation control by dividing the driving means 115.

The above circuit is merely an example of a circuit configuration for driving the organic EL structure (organic EL display main body), and other circuit configurations may be employed as long as they have equivalent functions. Further, the display control means, the scan electrode driving means, the data electrode driving means and the like may be completely integrated without being clearly divided. Note that these circuit devices are generally configured as one or more types of ICs and peripheral components thereof.

A commercially available IC or LSI such as an LCD controller, a thermal head driver, or a PDP driver may be used for the display control means, scan electrode drive means, and data electrode drive means of the present invention. The LCD controller, the thermal head driver, and the PDP driver can be configured by using an arithmetic circuit combining logic circuits as described above, a processor, a memory such as a RAM or a ROM, or the like, but are commercially available. It is preferred to use By using a commercially available IC, development costs and development time can be saved, and low-cost, rapid product development becomes possible.

Note that the LCD controller driver is
It outputs LCD drive pulses of two or more different signal levels required to drive the LCD. The LCD drive pulse has, for example, a reference voltage and a plurality of signal levels with respect to the reference voltage, and is output as a pulse waveform of each level synthesized. The cycle and signal level of these pulse waveforms are arbitrary, and are appropriately determined according to the LCD driving method (1/2, 1/3 division, etc.), the display mode (simple matrix type, segment type, etc.), and the like. Therefore, the organic EL display used is
What is equal to or approximate to these LCD modes may be appropriately selected.

However, when the organic EL element is driven using such a drive pulse having a plurality of voltage levels in a stepwise manner, the light emission luminance changes according to the current density, which is not practical. Therefore, this LCD driving pulse is applied to the organic EL.
It is preferable to use signal conversion means for converting the signal into a signal for an element.
The signal conversion means has one or more different detection levels. For example, it has a plurality of detection levels corresponding to a plurality of signal levels of the LCD drive pulse output from the LCD drive means, and drives the organic EL display drive signal in accordance with the state of the signal detected at the plurality of detection levels. Output.

Next, the detailed configuration of the data electrode driving means of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram showing a configuration example of the data driving means used in the present invention. In this example, the data electrode driving means has one I
C (LSI).

Referring to FIG. 4, data electrode driving means 300
Has an enable controller 301, a data controller 302, a bidirectional shift register 303, a latch 304, a level shifter 305, and a driver 306. The enable controller 301 has a terminal EIO
The bi-directional shift register 303 is controlled to an enabled state or a disabled state by an enable signal transmitted and received through the EIO1 and EIO2. The data controller 302 captures a display data signal transmitted and received via the terminals D0 to D3 and D4 to D7, and supplies the display data signal to the bidirectional shift register 303 at a predetermined timing.

The bidirectional shift register 303 has a terminal XS
Data is fetched from the data controller 302 by a control signal input through the CL, and the data shift direction is changed by a control signal input through the terminal SHL. Then, the display data supplied from the data controller 302 is output to a predetermined position of the latch 304. That is, the latch 304 and the level shifter 30
5, the data amount (for example, 80 bits) handled by the driver 306 and the data amount (for example, 8 bits) input from the data controller 302 at one time are different, and the former is much larger. Therefore, using a bidirectional shift register,
The data amount of both is adjusted. The latch 304
The output from the bidirectional shift register 303 is latched in accordance with the latch signal supplied via the terminal LP, and is supplied to the level shifter 305. In addition, the state may be inhibited by a control signal provided from the terminal INH. The level shifter 305 converts the output (voltage) of the latch 304 into an optimal signal level (voltage) for driving the driver 306. The driver 306 controls a current or a power required to drive the organic EL element by a signal from the level shifter, and drives the organic EL element.

Data electrode driving means 30 having such a configuration
At 0, the latch signal given to the terminal LP may be given at a cycle faster than the conventional drive timing by the number of divisions so as to have a predetermined number of divisions. That is, if the data electrode drive signal is divided into six, the latch pulse may be given at a cycle six times faster.

[0059]

Embodiment <Embodiment 1> The size of one pixel is 300 μm ×
An organic EL display device having a size of 300 μm and having 256 × 64 dots was driven by the present invention. Organic EL at this time
The threshold voltage of each pixel of the device had a variation of about 3.1 to 3.6 V.

The driving conditions are as follows: display data is transferred in 8-bit parallel at a transfer rate of 10 MHz, the frame frequency is 60 Hz, the scanning electrode selection period is about 260 μS, the data electrode driving frequency is about 960 Hz, and the minimum data electrode driving pulse width is 1
The uniform width was 6 μS, and the driving voltage was 9 V. Under these conditions, the number of gradations was 16.

When the driven organic EL display device was observed, it was confirmed that high-quality display without variation in light emission was possible even at low luminance.

<Embodiment 2> The size of one pixel is 300 μm
An organic EL display device having a size of 300 μm and a vertical division of 256 × 64 dots was driven by the present invention. At this time, the threshold voltage of each pixel of the organic EL element is 3.1 to
It had a variation of about 3.6V.

The driving conditions are as follows: display data is transferred in 8-bit parallel at a transfer rate of 10 MHz, the frame frequency is 60 Hz, the scanning electrode selection period is about 260 μS, the data electrode driving frequency is about 3.84 kHz, and the minimum data electrode driving pulse width is 4 μS. The width was uniform and the driving voltage was 9 V. Under these conditions,
The number of gradations was 64.

When the driven organic EL display device was observed, it was confirmed that high-quality display with no variation in light emission was possible even at low luminance.

<Embodiment 3> In the embodiment 1, the driving conditions include a frame frequency of 63 Hz and a scanning electrode selection period of about 2 hours.
The driving voltage was 48 μs and the driving voltage was 9 V. Further, the data electrode driving pulse width is set to 128 μs, 64 μs, 32 μs, 16 μs.
s and 8 μs, and output them in combination. Under these conditions, the number of gradations was 32.

When the driven organic EL display device was observed, high-quality display without variation in light emission was possible even at low luminance, and the number of gradations was higher than in Example 1, and high-quality image quality was obtained. Was.

<Embodiment 4> In Embodiment 1, the driving conditions are such that the frame frequency is 60 Hz and the scanning electrode selection period is about 2 hours.
60 μS, data electrode drive frequency about 15.6 kHz, minimum data electrode drive pulse width 1 μS uniform width, drive voltage 9 V
And At this time, the initial drive pulse is changed to the organic E
The pulse width was set to be wider by the time required to charge the capacitance component of the L element, and the others were set to the uniform pulse width described above. Under these conditions, the number of gradations was 256 or more.

[0068]

As described above, according to the present invention, it is possible to provide a driving device for an organic EL display device capable of controlling a sufficiently large number of gradations.

Further, it is possible to provide a driving device for an organic EL display device capable of obtaining a high-quality image even when a display having a large variation in the light emission threshold is driven.

Further, it is possible to realize a driving device for an organic display device which can be driven with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a diagram showing an operation of a driving device of an organic EL display device of the present invention.

FIG. 2 is a waveform diagram showing a state where the signal width of a divided data electrode drive signal is changed.

FIG. 3 is a diagram showing a current waveform flowing through an organic EL element and a voltage waveform of a scanning electrode.

FIG. 4 is a block diagram showing a basic configuration of a driving device of the organic EL display device of the present invention.

FIG. 5 is a block diagram illustrating a configuration example of a data electrode driving unit.

FIG. 6 is a block diagram illustrating a configuration example of a conventional PWM type driver.

[Explanation of symbols]

 k1 to k3 scan electrode j1 to j4 data electrode 111 main control means 112 display control means 113 display data storage device 114 scan electrode drive means 115 data electrode drive means 116 organic EL structure

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K007 AB00 AB18 BA06 DA00 GA02 GA04 5C080 AA06 BB05 CC03 DD01 DD27 EE29 EE30 FF12 GG09 GG12 JJ02 JJ04

Claims (6)

[Claims] 1. A driving device for an organic EL display device in which organic EL elements are arranged in a matrix, wherein a pulse density of signals applied to the organic EL elements is changed without changing a frame frequency for driving a scanning electrode. A driving device for an organic EL display device that performs variable gradation control. 2. The method according to claim 1, wherein the organic EL display device has a scanning electrode and a data electrode, and performs gradation control by changing the number of data electrode selections during each scanning electrode selection period of the scanning side electrode.
Of the organic EL display device. 3. The driving device for an organic EL display device according to claim 2, wherein the frame frequency and the driving frequency of the data electrode are different. 4. The driving device for an organic EL display device according to claim 2, wherein the driving frequency of the data electrode is higher than the frame frequency. 5. The driving device for an organic EL display device according to claim 2, wherein when the number of selections of the data electrode is plural, the selection of the data electrode is continuously performed. 6. The head pulse width when selecting the data electrodes continuously is wider than the other pulse widths.
Of the organic EL display device.