JP2005309068A - Method and device for driving organic el panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To drive a passive matrix drive type organic EL light emitting element so that the quantity of light emission can be prevented from decreasing owing to a leak current between its anodes. <P>SOLUTION: In the method for driving the organic EL panel 6 which has a plurality of anodes 21 and a plurality of cathodes 23 extending across the anodes 21, also in which organic EL light emitting elements R1, R2, R3, ..., G1, G2, G3, ..., and B1, B2, B3, ..., are formed, and a voltage or current corresponding to image data is applied between selected anodes 21 and cathodes 23 to makes organic EL light emitting elements illuminates with the quantity of light emission corresponding to the image data, the image data for the respective organic EL light emitting elements are corrected so that the quantity of light emission increases by the value obtained by multiplying difference between the quantity of light emission that the image data represent and the quantity of light emission that the image data represent as to adjacent elements by the ratio of the leak current Ir between the anodes to the driving current Id of the organic EL light emitting elements. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for driving an organic EL panel in which a plurality of organic EL light emitting elements are arranged in parallel.

  Conventionally, as shown in, for example, Patent Document 1, a plurality of anodes and a plurality of cathodes extending across the anodes are arranged facing each other in a state in which the intersecting portions are arranged in a matrix. 2. Description of the Related Art A passive matrix driving type organic EL panel in which an organic EL (electroluminescence) light emitting element composed of the electrode and a light emitting layer disposed therebetween is formed at each crossing portion is known. In this passive matrix drive type organic EL panel, one of the anode and the cathode is a scanning electrode and the other is a pixel electrode, and a scanning electrode selected line-sequentially and a current or voltage corresponding to image data is applied. The light emitting layer at the intersection with the pixel electrode emits light with a light emission amount corresponding to the image data.

In addition to constituting a display device, this type of organic EL panel is also considered to be used for constituting an exposure device as disclosed in Patent Document 2, for example. The exposure apparatus disclosed in Patent Document 2 uses an organic EL panel in which organic EL light emitting elements are arranged two-dimensionally, and is mainly composed of a plurality of organic EL light emitting elements arranged in one direction of the panel. In addition to scanning, the organic EL panel and the photosensitive member are relatively moved in a direction substantially perpendicular to this direction to perform sub-scanning. In addition, if an organic EL panel in which organic EL light emitting elements are two-dimensionally arranged in the main scanning direction and the sub-scanning direction is used, the organic EL panel and the photosensitive member are not moved relative to each other. A two-dimensional image can also be exposed.
Japanese Patent No. 2911552 JP 2001-356422 A

  By the way, in the passive matrix driving type organic EL panel, there is a problem that a current to be passed through the light emitting layer of a certain organic EL light emitting element leaks to the anode side of the adjacent element. This inter-anode leakage current basically occurs only when the potential of the anode of the adjacent element is lower than the potential of the anode of the element, and the larger the potential difference, the larger the value of the leakage current. In this way, when current leaks from a certain organic EL light emitting element to the adjacent element side, the current flowing through the element decreases, and the light emission amount of the element decreases accordingly.

  In a display device composed of an organic EL panel, even if the light emission amount of the organic EL light emitting element due to the leakage current between the anodes is reduced, the decrease in luminance of the pixel composed of the element is generally clearly visible. Not as noticeable.

  However, in an exposure apparatus configured using an organic EL panel, a decrease in the amount of light emitted from the organic EL light-emitting element due to a leakage current between anodes causes a decrease in exposure density, and image quality deterioration due to this is often clearly recognized. In other words, in this case, the density of the pixel exposed by the organic EL light emitting element in which current leaked to the adjacent element becomes low and approaches the density of the pixel exposed by the adjacent element, so that the sharpness of the exposed image is reduced. Become. For example, in the case of an apparatus that exposes a silver salt instant film, a leakage current between anodes of about 2.5 nA may be generated for an organic EL light emitting element driving current of 1.4 μA. In this example, the ratio of the leakage current between the anodes to the drive current reaches 1.8%, and the decrease in concentration due to the leakage current between the anodes cannot be ignored.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a driving method and a driving device for an organic EL panel capable of preventing a decrease in light emission amount due to leakage current between anodes of an organic EL light emitting element. To do.

  A driving method of an organic EL panel according to the present invention is characterized in that a decrease in light emission due to a leakage current between anodes of each organic EL light emitting element is predicted in advance, and image data is corrected to compensate for the decrease in light emission. To do.

That is, more specifically, the driving method of the organic EL panel according to the present invention is as follows.
As described above, a plurality of anodes and a plurality of cathodes extending across the anodes are arranged facing each other in a state where the intersecting portions are arranged in a matrix, and for each intersecting portion of these electrodes, A method of driving a passive matrix driving type organic EL panel in which an organic EL light emitting element comprising electrodes and a light emitting layer disposed between them is formed,
In a method for driving an organic EL panel, a voltage or current corresponding to image data is applied between a selected anode and cathode, and the organic EL light emitting element emits light with a light emission amount corresponding to the image data.
The ratio of the leakage current between anodes to the drive current of the organic EL light emitting element is set to the difference between the light emitting amount indicated by the image data and the light emitting amount indicated by the image data of the adjacent element. The light emission amount is corrected so as to increase by the multiplied value.

  In addition, as a ratio of the leakage current between anodes with respect to the driving current, for example, it is desirable to use a value measured for each organic EL light emitting element.

  Moreover, as a ratio of the leakage current between anodes with respect to the drive current, a value measured for one representative organic EL light emitting element in each organic EL panel, or a representative in one organic EL panel representing a plurality of organic EL panels. A value measured for a typical organic EL light emitting element, or a value predicted from the design conditions of the organic EL panel can also be used.

The inter-anode leakage current Ir for obtaining the above ratio is, for example,
One of the plurality of scanning electrodes, which is one of the anode and the cathode, is set in an ON state, and one of the plurality of signal electrodes, which is the other of the anode and the cathode, is set in an ON state. The light emitting element is driven to light with a set drive current Id,
At that time, the current If flowing between the scanning electrode line sequential selection switching circuit and the ON voltage source is measured by the current measuring means,
It can be obtained as Ir = (Id−If) / 2.

  In addition, when the image data for each organic EL light emitting element and the light emission amount indicated by the image data are in a linear relationship, the difference between the image data for each organic EL light emitting element and the image data for adjacent elements is the difference. It is desirable to use the difference.

Furthermore, when the driving method of the present invention is applied to an organic EL panel in which the organic EL light emitting element is driven by pulse width modulation driving or voltage intensity modulation driving,
When the lighting pulse width or driving voltage of the organic EL light emitting element and the image data D indicating the lighting pulse width or driving voltage are in a linear relationship with each other,
The image data regarding the kth organic EL light emitting element is D _k , and the image data regarding two adjacent elements in the anode arrangement direction with respect to the kth organic EL light emitting element are D _k−1 and D _{k + 1} , respectively. K (D _k −D _k−1 ) is added to the image data D _k only when D _k−1 <D _k , and the image data D only when D _{k + 1} <D _k. it is desirable to perform the process of adding the _{K (D k -D k + 1} ) to _k as the correction.

On the other hand, the organic EL panel driving device according to the present invention is:
A plurality of anodes and a plurality of cathodes extending across the anodes are arranged facing each other in a state in which the intersecting portions are arranged in a matrix, and for each of the intersecting portions of these electrodes, the electrodes and the gap therebetween An apparatus for driving a passive matrix driving type organic EL panel in which an organic EL light emitting element composed of a light emitting layer disposed on the substrate is formed,
A drive device for an organic EL panel comprising means for applying a voltage or current corresponding to image data between the selected anode and cathode and causing the organic EL light emitting element to emit light with a light emission amount corresponding to the image data In
The ratio of the leakage current between anodes to the drive current of the organic EL light emitting element is set to the difference between the light emitting amount indicated by the image data and the light emitting amount indicated by the image data of the adjacent element. It is characterized by comprising correction means for correcting the light emission amount so as to increase by the multiplied value.

  In addition, the above-mentioned “apply voltage or current corresponding to image data” may be applied by changing the value of voltage or current according to image data when modulating the light emission intensity of the organic EL light emitting element. In addition, when the organic EL light emitting element is driven by pulse width modulation, the voltage and current values are constant, and the pulse width is changed according to the image data and applied.

  When the current to be passed through a certain organic EL light emitting element leaks to the anode side of the adjacent element, the light emission intensity of the organic EL light emitting element decreases. The light emission amount that decreases in the organic EL light emitting element is determined by the light emission amount desired for the element (for example, the pulse width in the case of pulse width modulation and the voltage value in the case of voltage intensity modulation). ) And the amount of light emission desired for the adjacent element. Further, the leak current value per drive current takes a value specific to each element according to the distance between the anodes of each organic EL light emitting element. Therefore, the amount of light emission that decreases due to the leak current between the anodes of each organic EL light-emitting element is the difference between the light emission quantity indicated by the image data related to the element and the light emission quantity indicated by the image data for the adjacent element, and the drive specific to the element It is obtained by multiplying the ratio of the leakage current between anodes to the current.

  Based on the above knowledge, in the method and apparatus for driving an organic EL panel according to the present invention, the image data for each organic EL light-emitting element includes the light-emission amount indicated by the image data and the light-emission amount indicated by the image data for adjacent elements. Is corrected so as to increase the amount of light emission by a value obtained by multiplying the difference between the difference between the above and the drive current of the organic EL light emitting element by the ratio of the leakage current between the anodes. The decrease is compensated by the correction of the image data, and a desired light emission amount corresponding to the image data before the correction can be obtained.

  In addition, if the organic EL panel driving method and apparatus according to the present invention are applied to the organic EL panel used in the exposure apparatus as described above, it is possible to prevent the sharpness of the exposed image from being deteriorated due to the leakage current between the anodes. Of course, it is also possible to prevent a slight reduction in sharpness of a display image due to a leakage current between anodes by applying to an organic EL panel used in a display device.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a vertical sectional shape of an exposure apparatus having an organic EL panel driving apparatus according to an embodiment of the present invention. FIG. 2 shows a plan shape of an exposure head 1 constituting the exposure apparatus. Show. As shown in the drawing, this exposure apparatus conveys the exposure head 1 and the color photosensitive material 3 held at the position where the exposure light 2 emitted from the exposure head 1 is irradiated at a constant speed in the direction of arrow Y in FIG. For example, it comprises sub-scanning means 40 such as a nip roller.

  The exposure head 1 is disposed at a position for receiving the organic EL panel 6 and the exposure light 2 emitted from the organic EL panel 6, and has a refractive index for forming an image of the exposure light 2 on the color photosensitive material 3. A distributed lens array 30 and holding means 50 for holding the lens array 30 and the organic EL panel 6 are provided. The gradient index lens array 30 includes a large number of minute gradient index lenses arranged in parallel in the main scanning direction (arrow X direction) orthogonal to the sub-scanning direction Y.

  The exposure apparatus of this example exposes a color image on the color photosensitive material 3, and the organic EL panel 6 constituting the exposure head 1 includes a red line-shaped light emitting element array 6R arranged in the sub-scanning direction Y, a green color. The line-shaped light-emitting element array 6G and the blue line-shaped light-emitting element array 6B are configured. Each of these linear light emitting element arrays 6R, 6G, and 6B has a large number of red organic EL light emitting elements, green organic EL light emitting elements, and blue organic EL light emitting elements in the main scanning direction (arrow X direction) orthogonal to the sub-scanning direction Y. Are arranged side by side. In the present embodiment, the number n of light emitting elements in the main scanning direction is n = 7800, and the number of light emitting elements in the sub scanning direction is 3, which is 1 in total in each of the line-shaped light emitting element arrays 6R, 6G, and 6B.

  In FIG. 1, the light emitting element is typically shown as an organic EL light emitting element 20. Each organic EL light emitting element 20 is formed by sequentially laminating a transparent anode 21, an organic compound layer 22 including a light emitting layer, and a metal cathode 23 on a transparent substrate 10 made of glass or the like. Then, red light emitting elements, green light emitting elements, and blue light emitting elements are respectively applied as the light emitting layers, thereby forming red organic EL light emitting elements, green organic EL light emitting elements, and blue organic EL light emitting elements, respectively.

  The line-shaped light emitting element arrays 6R, 6G, and 6B are connected to a three-channel cathode driver 7 and to a 244 channel anode driver 8, and are exposed images by a so-called passive matrix line sequential selection driving method. Is driven on the basis of predetermined image data. The cathode driver 7 and the anode driver 8 constitute a part of the drive circuit 60 shown in FIG. In this embodiment, the number of cathode drivers 7 is one and the number of anode drivers 8 is sixteen.

  Elements constituting the organic EL light emitting element 20 are arranged in a sealing member 25 made of, for example, a stainless steel can. That is, the edge of the sealing member 25 and the transparent substrate 10 are bonded, and the organic EL light emitting element 20 is sealed in the sealing member 25 filled with dry nitrogen gas.

  In the organic EL light emitting device 20 having the above configuration, when a predetermined voltage is applied between the metal cathode 23 and the transparent anode 21 extending across the metal cathode 23, an organic compound is formed at each intersection of the electrodes to which the voltage is applied. A current flows through the layer 22, and the light emitting layer contained therein emits light. This emitted light is emitted outside the element through the transparent anode 21 and the transparent substrate 10. Note that such an organic EL light emitting device 20 has a characteristic of excellent wavelength stability.

  Here, the transparent anode 21 preferably has a light transmittance of at least 50 percent or more, preferably 70 percent or more, in the visible light wavelength region of 400 nm to 700 nm. As the material of the transparent anode 21, conventionally known compounds such as tin oxide, indium tin oxide (ITO), and zinc indium oxide can be used as appropriate, but other metals having a high work function such as gold and platinum. You may use the thin film which consists of. In addition, organic compounds such as polyaniline, polythiophene, polypyrrole, or derivatives thereof can also be used. Supervised by Yutaka Sawada, “New Development of Transparent Conductive Film”, published by CMC Co., Ltd. (1999), there is a detailed description of the transparent conductive film, and what is shown there can be applied to the present invention. It is. The transparent anode 21 can be formed on the transparent substrate 10 by a vacuum deposition method, a sputtering method, an ion plating method, or the like.

  On the other hand, the organic compound layer 22 may have a single-layer structure composed of only a light emitting layer, or other layers such as a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer in addition to the light emitting layer. A stacked structure may be used as appropriate. Specific layer structures of the organic compound layer 22 and the electrode include an anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode structure, and an anode / light emitting layer / electron transport layer / cathode, anode. / Hole transport layer / light-emitting layer / electron transport layer / cathode and the like. A plurality of light emitting layers, hole transport layers, hole injection layers, and electron injection layers may be provided.

  The metal cathode 23 is formed of a metal material such as an alkali metal such as Li or K having a low work function, an alkaline earth metal such as Mg or Ca, and an alloy or a mixture of these metals with Ag or Al. Is preferred. In order to achieve both storage stability and electron injectability at the cathode, the electrode formed of the above material may be further coated with Ag, Al, Au, or the like having a high work function and high conductivity. Note that, similarly to the transparent anode 21, the metal cathode 23 can also be formed by a known method such as a vacuum deposition method, a sputtering method, or an ion plating method.

  Next, the organic EL panel 6 and the cathode driver 7 and the anode driver 8 for driving the organic EL panel 6 will be described in detail with reference to FIG. In the figure, the organic EL light emitting elements 20 formed at each intersection of the transparent anode 21 and the metal cathode 23 are diodes R1, R2, R3,... Rn for the red line light emitting element array 6R. The green line light emitting element array 6G is shown as diodes G1, G2, G3... Gn, and the blue line light emitting element array 6B is shown as diodes B1, B2, B3. . As described above, in this example, n = 7800. Further, in the figure, actually, 16 anode drivers 8 are schematically shown as one.

  The three metal cathodes 23 constituting the red line light emitting element array 6R, the green line light emitting element array 6G and the blue line light emitting element array 6B are connected to the switching portions S21, S22 and S23 of the cathode driver 7, respectively. Yes. These switching units S21, S22, and S23 are connected to, for example, a line counter / decoder (not shown) that receives a line clock and a line clear signal, and open / close based on the instructions, thereby switching one of the metal cathodes 23. Are sequentially and selectively connected to ground. As a result, the one metal cathode 23 is set from the OFF voltage (Voff) to the ON voltage, and a current can flow through the intersection of the metal cathode 23 and the transparent anode 21.

  On the other hand, the n transparent anodes 21 are connected to the switching units S11, S12, S13... S1n of the anode driver 8, respectively. These switching units S11, S12, S13... S1n are connected to a PWM (pulse width modulation) circuit (not shown), and open / close based on a pulse voltage signal for 7800 pixels per line output from the PWM circuit. Operate. This voltage signal has a pulse width changed based on the image data D shown in FIG. 1, and the switching units S11, S12, S13... S1n are transparent anodes during the period when the voltage signal is input. 21 are connected to constant current sources Q1, Q2, Q3... Qn, respectively.

  The image data D shown in FIG. 1 is subjected to correction for compensating for a decrease in the amount of light emission due to the leakage current between the anodes in the correction circuit 61, converted into corrected image data DD, and then input to the drive circuit 60. The correction will be described later.

  The operation of the exposure apparatus having the above configuration will be described below. When the color photosensitive material 3 shown in FIG. 1 is subjected to image exposure, the color photosensitive material 3 is conveyed by the sub scanning means 40 at a constant speed in the arrow Y direction. This transport direction is a direction from top to bottom in FIG. Further, in synchronism with the conveyance of the color photosensitive material 3, one of the three metal cathodes 23 is sequentially and selectively connected to the ground by the switching units S21, S22 and S23 of the cathode driver 7 shown in FIG. . FIG. 3 shows a state in which the first metal cathode 23 of the red line-shaped light emitting element array 6R is selected.

  In this way, the switching portions S11, S12, S13,... S1n of the anode driver 8 within the period when the first metal cathode 23, that is, the metal cathode 23 constituting the red line light emitting element array 6R is selected. In addition, a voltage signal having a pulse width corresponding to the image data D indicating the red density of the first, second, third,..., Nth pixels of the first main scanning line is input. The switching units S11, S12, S13... S1n connect the transparent anode 21 to the constant current sources Q1, Q2, Q3... Qn for the duration of the pulse width, so that the transparent anode 21 and the first metal are connected. A constant current flows through the organic compound layer 22 (see FIG. 1) between the cathode 23 and red light is emitted from the organic compound layer 22.

  The red light emitted from the red line-shaped light emitting element array 6R in this way is condensed on the color photosensitive material 3 by the lens array 30, whereby the first and first scan lines constituting the first main scanning line are formed on the color photosensitive material 3. The 2, 3... N th pixel is exposed with red light.

  Next, during the period when the second metal cathode 23, that is, the metal cathode 23 constituting the green line-shaped light emitting element array 6G is selected, the switching portions S11, S12, S13. A voltage signal having a pulse width corresponding to the image data D indicating the green density of the first, first, second,..., Nth pixels of the first main scanning line is input. The switching units S11, S12, S13... S1n connect the transparent anode 21 to the constant current sources Q1, Q2, Q3... Qn for the duration of the pulse width, so that the transparent anode 21 and the first metal are connected. A constant current flows through the organic compound layer 22 between the cathode 23 and green light is emitted from the organic compound layer 22.

  The green light emitted from the green line-shaped light emitting element array 6G in this way is condensed on the color photosensitive material 3 by the lens array 30, and thereby the first and first scan lines constituting the first main scanning line on the color photosensitive material 3. The 2, 3... N th pixel is exposed with green light. Since the color photosensitive material 3 is conveyed at a constant speed as described above, the green light is irradiated onto a portion of the color photosensitive material 3 that has already been exposed to red light.

  Next, during the period when the third metal cathode 23, that is, the metal cathode 23 constituting the blue line-shaped light emitting element array 6B is selected, the switching parts S11, S12, S13. A voltage signal having a pulse width corresponding to the image data D indicating the blue density of the first, first, second,..., Nth pixels of the first main scanning line is input. The switching units S11, S12, S13... S1n connect the transparent anode 21 to the constant current sources Q1, Q2, Q3... Qn for the duration of the pulse width, so that the transparent anode 21 and the first metal are connected. A constant current flows through the organic compound layer 22 between the cathode 23 and blue light is emitted from the organic compound layer 22.

  The blue light emitted from the blue line-shaped light emitting element array 6B in this way is condensed on the color photosensitive material 3 by the lens array 30, and thereby the first and first scan lines constituting the first main scanning line are formed on the color photosensitive material 3. The 2, 3... N th pixel is exposed with blue light. Since the color photosensitive material 3 is conveyed at a constant speed as described above, the blue light is irradiated onto the portion of the color photosensitive material 3 that has already been exposed to red light and green light. By performing the above operation, the first color main scanning line is exposed and recorded on the color photosensitive material 3.

  Next, the line sequential selection of the metal cathodes returns to the first metal cathode 23, and within the period when the first metal cathode 23, that is, the metal cathode 23 constituting the red line light emitting element array 6R is selected. The switching portions S11, S12, S13... S1n of the anode driver 8 have pulse widths corresponding to the image data D indicating the red density of the first, second, third,. A voltage signal is input. The switching units S11, S12, S13... S1n connect the transparent anode 21 to the constant current sources Q1, Q2, Q3... Qn for the duration of the pulse width, so that the transparent anode 21 and the first metal are connected. A constant current flows through the organic compound layer 22 between the cathode 23 and red light is emitted from the organic compound layer 22.

  The red light emitted from the red line-shaped light emitting element array 6R in this way is condensed on the color photosensitive material 3 by the lens array 30, and thereby the first and first lines constituting the second main scanning line are formed on the color photosensitive material 3. The 2, 3... N th pixel is exposed with red light.

  In the following, the same operation is repeated to expose the second color main scanning line. Further, such color main scanning lines are successively exposed in the sub-scanning direction Y, and a large number of main scanning lines are exposed on the color photosensitive material 3. A two-dimensional color image consisting of scanning lines is exposed. In the present embodiment, as described above, each color exposure light is subjected to pulse width modulation, and the amount of emitted light is controlled corresponding to the image data, whereby a color gradation image is exposed.

  Next, the point of compensating for the anode leakage current will be described. First, the leakage current between anodes will be described with reference to FIG. FIG. 4 shows a state in which the second metal cathode 23 is connected to the ground via the switching unit S22, and only the second transparent anode 21 among the n transparent anodes 21 is connected to the constant current source Q2. Is shown. In this state, when the drive current Id flows from the constant current source Q2 to the organic EL light emitting element G2 through the path indicated by the broken arrow in the figure, the transparent anode 21 of the adjacent elements G1 and G3 is connected from the switching portions S11 and S13. Since it is connected to the ground, a part of the current leaks to the ground side through the first and third transparent anodes 21. A path through which the anode leakage current Ir flows in this way toward the ground is indicated by a dashed-dotted arrow in the figure. Further, the inter-anode leakage current Ir flows through a resistance existing between adjacent anodes, but this resistance is conceptually shown as a resistance NR in the drawing.

  In this case, the current that actually flows through the second metal cathode 23, that is, the current If supplied to the organic EL light emitting element G2, is a value obtained by subtracting 2 × Ir from the drive current Id. Therefore, if the current measuring device 62 is inserted between the wiring commonly connected to the lower terminals of the three switching portions S21, S22 and S23 of the cathode driver 7 and the ground, and the current If flowing therethrough is measured. , Ir = (Id−If) / 2, the anode leakage current Ir can be obtained.

  In addition, as described above, one transparent anode 21 used for measuring the leakage current between anodes is set to ON, and n transparent anodes 21 are divided into two groups, right and left, and m transparent anodes 21 in one group. It is also possible to measure the leakage current between the anodes with the ON setting and the other (n−m) transparent anodes 21 set to OFF. In that case, the measurement accuracy is lower than in the above case, but the inter-anode leakage current Ir can be obtained basically based on the relationship Ir = m · Id−If.

  As the current measuring device 62, a general circuit configuration as shown in FIG. 5, for example, can be applied. This circuit comprises a sense resistor 63, a current-voltage conversion circuit using an operational amplifier 64, and an A / D converter 65 for digitizing the analog output of the operational amplifier 64. In this circuit configuration, the voltage drop at the sense resistor 63 needs to be within a range that does not affect the light emission of the organic EL light emitting element 20.

Next, variation in the light emission amount of each organic EL light emitting element 20 due to the leak current between anodes will be described. In this embodiment, the organic EL light emitting element 20 is driven by pulse width modulation, and the light emission amount of each element is changed by changing the light emission time of each element according to the image data. Here, among the n organic EL light emitting elements 20 arranged in parallel in the main scanning direction X in the line-shaped light emitting element array 6R, 6G or 6B, the (k-1) th, kth and (k + 1) th. The light emission time of the kth element is examined by indicating the light emission times of the _kth element as T _k−1 , T _k and T _{k + 1} , respectively.

When the kth organic EL light emitting element 20 emits light, if the adjacent (k−1) th (k + 1) th organic EL light emitting element 20 emits light in the same manner, this kth organic EL light emitting element 20 emits light. Since there is no potential difference between the organic EL light emitting element 20 and the transparent anode 21 of the adjacent element, no leakage current between the anodes occurs. That is, the anode leakage current is generated when T _k−1 <T _k and T _{k + 1} <T _k . Here, assuming that the pulsed drive current is Id, the anode leakage current is Ir, and the ratio of the anode leakage current to the drive current Ir / Id is K, T _k-1 <T _k and T _{k + 1} <T _k In this case, the light emission amount E _k of the _kth organic EL light emitting element 20 is expressed as follows:
E _k = j · Id · T _k −j · Ir (T _k −T _k−1 ) −j · Ir (T _k −T _{k + 1} )
It becomes. That is, the second term and the third term on the right side of this equation are the amount of light emission that decreases due to the leakage current between the anodes. When the above equation is transformed,
E _k = j · Id {T _k −K (T _k −T _k−1 ) −K (T _k −T _{k + 1} )}
Therefore, if the image data input to the drive circuit 60 is corrected in advance so that the light emission time is increased by K (T _k −T _k−1 ) + K (T _k −T _{k + 1} ), It is possible to compensate for the decrease in the light emission amount due to the leak current. Therefore, when the image data D and the light emission time T is in a linear relation to each other, when the image data relating to the k-th organic EL element 20 is represented as D _k, the image data D _k K (D _k -D If correction for adding ( _k−1 ) + K (D _k −D _{k + 1} ) is performed, a decrease in the light emission amount due to the leakage current between the anodes is compensated. This compensation is necessary when T _k-1 <T _k or T _{k + 1} <T _k as described above, that is, when D _k-1 <D _k or D _{k + 1} <D _k here. Therefore, if D _k−1 ≧ D _k , (D _k −D _k−1 ) should be replaced with 0 (zero), and similarly if D _{k + 1} ≧ D _k (D _k −D _{k + 1} ) should be replaced with 0.

FIG. 6 shows in detail the correction circuit 61 (see FIG. 1) that performs the correction described above. The correction circuit 61 constitutes a driving device according to the present invention together with the driving circuit 60. In the correction circuit 61, digital image data D for n pixels related to one main scanning line is D-type flip-flops 70 and 71. Therefore, the image data D _k−1 and D _k whose timings are aligned with each other are input to the subtracter 72, and the image data D _k and D _{k + 1} are input to the subtractor 73. The subtracter 72 performs subtraction D _k −D _k−1 and inputs a difference (D _k −D _k−1 ) and a code bit indicating the sign of the difference to the data selector 74. The data selector 74 outputs a difference (D _k −D _k−1 ) when the difference indicated by the sign bit is a positive value, and replaces the difference when the difference indicated by the sign bit is a negative value or 0. Outputs a “0” value. The subtractor 73 performs subtraction D _k −D _{k + 1} and inputs a difference (D _k −D _{k + 1} ) and a code bit indicating the sign of this difference to the data selector 75. The data selector 75 outputs a difference (D _k −D _{k + 1} ) when the difference indicated by the sign bit is a positive value, and replaces the difference when the difference indicated by the sign bit is a negative value or 0. Outputs a “0” value.

The outputs of the data selectors 74 and 75 are added in an adder 76, and the addition result is then multiplied by the ratio K in a multiplier 77. The multiplication result and the image data D _k are added by an adder 78. By the above operation, the image data D _k in _{K (D k -D k-1} ) + K (D k -D k + 1) corrected image data DD _k correction has been made to add to obtain. As is apparent from the above description, the corrected image data DD _k may be the uncorrected image data D _k itself.

If the image data D _k is corrected as described above and the organic EL panel 6 is driven based on the corrected image data DD _k , a decrease in the amount of light emission due to the leak current between the anodes of each organic EL light emitting element 20 is compensated.

  As described above with reference to FIG. 4, the ratio K is obtained by calculating the ratio of the leakage current Ir between the anodes as Ir = (Id−If) / 2 and the drive current Id at that time. Can be sought. As such a ratio K = Ir / Id, for example, a value measured for each organic EL light emitting element 20, a value measured for one typical organic EL light emitting element 20 in the organic EL panel 6, or a plurality of organic EL elements A value measured for one typical organic EL light emitting element 20 in one organic EL panel 6 representing the EL panel can be used, and further, prediction is made from design conditions of the organic EL panel 6 without performing actual measurement. The value to be used can also be used. In addition, when obtaining the value of K = Ir / Id based on the above-described measurement, the measurement may be performed only once before shipment of the organic EL panel, and the value of K may be fixed thereafter. Alternatively, in order to be able to cope with changes over time, measurements should be taken periodically or whenever necessary when the organic EL panel is in actual use or when it is in a predetermined state (for example, when the power is turned on), and the value of K is reset each time. Also good.

  As described above, the embodiment applied to the organic EL panel using the cathode as the scanning electrode and the anode as the signal electrode has been described. However, the present invention, on the contrary, uses the cathode as the signal electrode and the anode as the scanning electrode. It is also possible to apply to. FIG. 7 shows an example of an organic EL panel configured as described above. In FIG. 7, the same elements as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted unless particularly necessary.

  In the configuration of FIG. 7, the cathode driver 7 'is the same as the anode driver 8 of FIG. 4, and the anode driver 8' is the same as the cathode driver 7 of FIG. In FIG. 7, the second transparent anode 21 among the three transparent anodes 21 is selected to be in the ON state, and only the second metal cathode 23 of the n metal cathodes 23 is used as the constant current source Q2. The connected state is shown. Even in this state, when the drive current Id flows through the organic EL light emitting element G2 through the path indicated by the broken line arrow in the figure, the transparent anode 21 of the adjacent element is connected to the ground from the switching portions S21 and S23. The current leaks to the ground side through the anodes of adjacent elements, that is, the first and third transparent anodes 21. A path through which the anode leakage current Ir flows in this way toward the ground is indicated by a dashed-dotted arrow in the figure.

  Also in this configuration, the current that actually flows through the second metal cathode 23, that is, the current If supplied to the organic EL light emitting element G2, is a value obtained by subtracting 2 × Ir from the drive current Id. Therefore, the current measuring device 62 is inserted between the wiring connected in common to the upper terminals of the three switching units S21, S22 and S23 and the anode ON voltage (Vcc in the figure) point, and the current If flowing therethrough , The leakage current between anodes Ir can be obtained as Ir = (Id−If) / 2.

  As described above, the embodiment applied to the organic EL panel 6 in which the organic EL light emitting element 20 is driven by pulse width modulation has been described, but an intensity modulation method in which the organic EL light emitting element 20 is driven by a voltage or current corresponding to image data is adopted. In this case, the same correction is possible. Since the leakage current between the anodes is substantially proportional to the potential difference between the anodes, when the voltage intensity modulation driving method is adopted, the image data may be corrected similarly to the case where the pulse width modulation driving method described above is adopted.

  On the other hand, when the current intensity modulation driving method is adopted, since the voltage-current characteristics of the organic EL light emitting element are generally not linear, the same correction method as that when the pulse width modulation driving method is adopted performs accurate correction. It is difficult. Therefore, when the current intensity modulation driving method is adopted, the image data indicating the driving current value of the organic EL light emitting element is subjected to current-voltage conversion using a conversion table such as LUT (lookup table), and then the converted image. When the pulse width modulation drive method is adopted by performing the same correction on the data as when the pulse width modulation drive method is adopted, and then adding the process of converting the corrected image data to a current value by voltage-current conversion The same correction method can be applied.

1 is a side view of an exposure apparatus including an organic EL panel driving apparatus according to an embodiment of the present invention. Schematic plan view of an organic EL panel applied to the apparatus of FIG. Circuit diagram showing the organic EL panel and its drive circuit FIG. 3 is a circuit diagram showing the path of the leakage current between anodes and the measuring means thereof added to the circuit of FIG. Circuit diagram showing in detail the means for measuring the leakage current between the anodes Circuit diagram showing a part of the organic EL panel drive device The circuit diagram which shows the drive circuit of the organic electroluminescent panel by another embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exposure head 2 Exposure light 3 Color photosensitive material 7, 7 'Cathode driver 8, 8' Anode driver
20 Organic EL light emitting device
21 Transparent anode
22 Organic compound layer
23 Metal cathode
40 Sub-scanning means
60 Drive circuit
61 Correction circuit
62 Current measuring instrument

Claims (9)

A plurality of anodes and a plurality of cathodes extending across the anodes are arranged facing each other in a state in which the intersecting portions are arranged in a matrix, and for each of the intersecting portions of these electrodes, the electrodes and the gap therebetween A method of driving a passive matrix driving type organic EL panel in which an organic EL light emitting element composed of a light emitting layer disposed on a substrate is formed,
In a method for driving an organic EL panel, a voltage or current corresponding to image data is applied between a selected anode and cathode, and the organic EL light emitting element emits light with a light emission amount corresponding to the image data.
The ratio of the leakage current between anodes to the drive current of the organic EL light emitting element is set to the difference between the light emitting amount indicated by the image data and the light emitting amount indicated by the image data of the adjacent element. A method of driving an organic EL panel, wherein the light emission amount is corrected so as to increase by the multiplied value.   2. The method of driving an organic EL panel according to claim 1, wherein a value measured for each organic EL light emitting element is used as a ratio of the leakage current between anodes to the driving current.   2. The method of driving an organic EL panel according to claim 1, wherein a value measured for one typical organic EL light emitting element in each organic EL panel is used as a ratio of the leakage current between anodes to the driving current.   2. The value measured for one typical organic EL light emitting element in one organic EL panel representing a plurality of organic EL panels is used as the ratio of the leakage current between anodes to the driving current. Driving method of organic EL panel.   2. The method of driving an organic EL panel according to claim 1, wherein a value predicted from a design condition of the organic EL panel is used as a ratio of an anode leakage current to the driving current. One of the plurality of scanning electrodes, which is one of the anode and the cathode, is set in an ON state, and one of the plurality of signal electrodes, which is the other of the anode and the cathode, is set in an ON state. The light emitting element is driven to light with a set drive current Id,
At that time, the current If flowing between the scanning electrode line sequential selection switching circuit and the ON voltage source is measured by the current measuring means,
6. The organic EL panel driving method according to claim 1, wherein an inter-anode leakage current Ir for obtaining the ratio is obtained as Ir = (Id−If) / 2. 6.   The difference between image data for each organic EL light emitting element and image data for an adjacent element is used as the difference when the image data and a light emission amount indicated by the image data are in a linear relationship. Item 7. A method for driving an organic EL panel according to any one of Items 1 to 6. In the organic EL panel that drives the organic EL light-emitting element by pulse width modulation driving or voltage intensity modulation driving,
When the lighting pulse width or driving voltage of the organic EL light emitting element and the image data D indicating the lighting pulse width or driving voltage are in a linear relationship with each other,
The image data regarding the kth organic EL light emitting element is D _k , and the image data regarding two adjacent elements in the anode arrangement direction with respect to the kth organic EL light emitting element are D _k−1 and D _{k + 1} , respectively. K (D _k −D _k−1 ) is added to the image data D _k only when D _k−1 <D _k , and the image data D only when D _{k + 1} <D _{k. k} in _{K (D k -D k + 1} ) driving method of the organic EL panel according to claim 1 to 7 or 1, wherein said by performing processing as the correction for adding. A plurality of anodes and a plurality of cathodes extending across the anodes are arranged facing each other in a state in which the intersecting portions are arranged in a matrix, and for each of the intersecting portions of these electrodes, the electrodes and the gap therebetween An apparatus for driving a passive matrix driving type organic EL panel in which an organic EL light emitting element composed of a light emitting layer disposed on the substrate is formed,
A drive device for an organic EL panel comprising means for applying a voltage or current corresponding to image data between the selected anode and cathode and causing the organic EL light emitting element to emit light with a light emission amount corresponding to the image data In
The ratio of the leakage current between anodes to the drive current of the organic EL light emitting element is set to the difference between the light emitting amount indicated by the image data and the light emitting amount indicated by the image data of the adjacent element. An organic EL panel drive device comprising correction means for correcting the light emission amount so as to increase by the multiplied value.

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