JPH1187053A - Driving device for organic el display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the luminance adjustment while driving a device with a simple circuit by driving each internal resistor (Rel) of a light emitting element of an organic EL display and an external resistor (Ro) connected in series to the light emitting element in the specified condition. SOLUTION: A condition that Rel/Ro>=35 is set. At the time of constant voltage drive, influence to the light emitting luminance is increased, as a value of an external resistor Ro is larger, and influence of the external resistor Ro is reduced, as a value of an internal resistor Rel of the light emitting element is larger. Consequently, dispersion of the light emitting luminance is restricted at the predetermined value or less by setting the Rel/Ro at 35 or more, desirably at 75 or more. Relative luminance change to the maximum light emitting luminance is desirably set within ±20%, and in the case of exceeding 20%, visibility is lowered. Area of the light emitting element is desirably set at 0.001-20 mm<2> , and an electrode driving means desirably has a display control unit and an auxiliary switch to be operated by the electrode driving signal so as to drive the organic EL display.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to home appliances, automobiles, information display panels used for audio and the like, instrument panels for automobiles, displays for displaying moving images and still images, and the like.
The present invention relates to a driving device for an organic EL display, which is used for a motorcycle electric component and is configured using an organic compound.

[0002]

2. Description of the Related Art In recent years, organic EL devices have been actively studied,
It is being put to practical use. In this method, a hole transport material such as triphenyldiamine (TPD) is formed into a thin film on a transparent electrode (hole injection electrode) such as tin-doped indium oxide (ITO) by vapor deposition, and then an aluminum quinolinol complex (A
1q3) as a light emitting layer, and a metal electrode such as Mg having a small work function (electron injection electrode)
This element has a basic structure and has a very high luminance of several hundreds to several tens of thousands cd / m ² at a voltage of about 10 V, and thus has attracted attention as a display for home electric appliances, automobiles, motorcycle electric components and the like.

[0003] Such an organic EL element is, for example, in the case of a character display or a simple matrix type display, for example, a scanning (common line) electrode usually serving as a negative electrode and data (segment line) usually serving as an anode (transparent electrode). Having an electrode and an organic layer (e.g., a light-emitting layer);
An organic layer is sandwiched between the electrodes, and is disposed between transparent (glass) substrates (sealing plates). When a potential difference is applied between the scanning electrode and the data electrode of this organic EL display, an electric field is generated in the organic layer, and electrons accelerated by the electric field generate electron-hole pairs or excite electrons at the emission center. Light is emitted when the electron-hole pair disappears or when the excited state returns to the steady state.

[0004] The character display as described above,
When driving a matrix type display, the character data such as numbers and characters to be displayed and the image data such as figures are expanded into data corresponding to a specific segment of the character display or a specific position on the matrix, and the display is displayed. A control or drive is required to be displayed above. The control device or the drive device analyzes, for example, character data and image data, and specifies data of a specific segment, an arithmetic circuit or a processor for developing the data into matrix data, and bitmap image data for the processor and the like. , A memory for providing bitmap address data and the like.

A scanning electrode driving signal or a data electrode driving signal for driving a scanning electrode or a data electrode provided from such a driving device includes a specific segment on a display given by a pair of signals or a specific segment. Drive the pixel at the coordinate point. The driven pixel emits light corresponding to a predetermined division time in the case of the time division control method.

The organic EL display having such a structure emits light by holes and electrons injected from the electrodes as described above. Therefore, the emission luminance of the organic EL display has a current-dependent characteristic that changes in proportion to the current density. Further, each light emitting element has a predetermined resistance, but since the light emitting surface corresponds to a current path, an apparent resistance value changes according to its area. That is, when the area of the light emitting element is large, the apparent resistance is low, and when the light emitting area is small, the apparent resistance is increased. Such an organic EL
When driving a display, you need to
Light-emitting elements having different light-emitting areas of more than one kind may be included in one screen. If this light emitting element is driven as it is, the internal resistance of each light emitting element is different, so that the light emission luminance is different, and it is not possible to obtain uniform light emission luminance.

Therefore, when driving a character display or the like having a different light emitting area by the conventional constant current driving method, it is necessary to adjust an appropriate current value for each segment. However, if the constant current is set for each segment, the circuit configuration becomes too complicated and not practical.
In addition, if a constant voltage system is used in which each element is driven by a single drive voltage, the circuit configuration is simplified, but it is difficult to correct the variation in luminance. For this reason, in order to obtain uniform light emission, an external resistor is added to adjust the light emission luminance in the display.

However, the internal resistance of an organic EL display varies slightly depending on the material, manufacturing method, and the like, and it is difficult to provide an appropriate resistance value to the internal resistance at the design stage. On the other hand, a method of measuring the internal resistance one by one to obtain an appropriate resistance value is also conceivable, but it is not realistic to perform such an operation in a mass production process.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a driving apparatus for an organic EL display which can be driven by a simple circuit configuration, does not need to add a complicated circuit, and does not need to measure and adjust the internal resistance one by one. It is to provide a driving method.

The brightness can be adjusted by a simple operation.
Further, it is an object of the present invention to provide a low-cost organic EL display driving device.

[0011]

The above object is achieved by the following constitutions (1) to (3). (1) It has at least one set of a hole injection electrode, an electron injection electrode, and an organic EL layer existing between the electrodes.
An organic EL display in which one circuit is formed through a set of hole injection electrodes and electron injection electrodes; and electrode driving means for driving the hole injection electrodes and electron injection electrodes; A driving device for an organic EL display that drives under the condition that Rel / Ro ≧ 35, where the internal resistance of the light emitting element of the EL display = Rel and the external resistance connected in series with the light emitting element = Ro. (2) The driving device for an organic EL display according to (1), wherein the organic EL display has a light emitting element area of 0.001 to 20 mm ² . (3) The electrode driving means includes: a display control unit that controls the organic EL display to display predetermined data; and an auxiliary switch element that operates in response to an electrode driving signal from the display control unit to drive the organic EL display. The organic EL according to the above (1) or (2),
Display drive.

[0012]

When two or more types of characters having different light emitting areas per element are present in the display, the variation in the luminance of the light emitting elements is kept within a certain range. It is necessary to calculate the current density (current per unit area), calculate the light emission luminance in each area, and adjust the light emission luminance between elements having different areas. In an actual circuit or the like, light emission is controlled by an external switch element or the like. Therefore, it is necessary to consider an equivalent circuit when the light emitting element emits light.

For example, as shown in FIG. 4, consider a circuit comprising a drive power supply Vcc, an organic EL element EL, a switch element Tr, and a current limiting resistor (protective resistor) Rr.
It becomes an equivalent series circuit as shown in FIG. In an actual circuit, the power supply side is usually connected to GND with an organic EL element interposed therebetween.
The organic EL element is driven by arranging a switch element on each side and operating the two switch elements in synchronization with each other. However, here, it is assumed that the number of switch elements is one. That is, if the external switch element is an FET, Ron (FET: drain-source ON resistance) becomes an equivalent series resistance Ro connected in series with the light emitting element EL, and if it is a transistor, it depends on the collector current Ic. The resistance component of the switch element is calculated from the collector-emitter voltage Vce, and this is calculated as the light emitting element EL.
Is connected to the external resistor Ro in series. When an external resistor Rr is provided externally for the purpose of adjusting the variation of FETs and transistors, protecting against short circuits, etc., this is connected in series as an external resistor Ro. In addition, organic EL
The internal resistance per element of the display is calculated from the current density-luminance characteristic and the current density-voltage characteristic of the element.

Therefore, the current flowing through the series circuit is limited by the resistors Rel, Ron, and Rr.
As described above, the internal resistance Rel of the light emitting element (organic EL element) depends on the size of the element area such as a character, and increases as the area decreases. Also, the internal resistance R of the switch element
When on is sufficiently small, the effect can be ignored regardless of the value of the internal resistance Rel of the light emitting element, that is, the screen of any size. However, when the internal resistance Ron is large to some extent, the effect cannot be ignored when the internal resistance Rel of the light emitting element becomes small. Here, the light-emitting element includes, as the external resistance Ro, an on-resistance Ron of the switch element and another external resistance Rr (including a resistance component connected in series to the light-emitting element in addition to the internal resistance of the switch element). The light emission luminance is regulated in relation to these resistance values. For this reason, in the present invention, the internal resistance R
The variation in light emission luminance will be described based on the relationship between el and the external resistance Ro.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An organic EL display driving apparatus according to the present invention has at least one set of hole injection electrodes, an electron injection electrode, and an organic EL layer existing between the electrodes. 1 through the electrode and the electron injection electrode
An organic EL display on which two circuits are formed, and electrode driving means for driving the hole injection electrode and the electron injection electrode, wherein the electrode driving means has an internal resistance of a light emitting element of the organic EL display = Rel, a light emitting element When the external resistance connected in series with the power supply is Ro, driving is performed under the condition that Rel / Ro ≧ 35. Here, the light emitting element is organic E
L is equivalent to one pixel of the display, and one light emitting unit of organic E
Refers to the L element portion.

The internal resistance Rel of the light emitting element and the external resistance Ro
Is not less than a predetermined value, it is possible to suppress the variation of the light emission luminance to a predetermined value or less. As described above, in constant voltage driving or the like, the larger the value of the external resistance Ro, the greater the effect on the light emission luminance. Further, the larger the value of the internal resistance Rel of the light emitting element is, the less the influence of the external resistance Ro is. Therefore, R defined by these ratios
By setting el / Ro to be 35 or more, preferably 75 or more, it is possible to make the variation of the light emission luminance equal to or less than a predetermined value. The variation in light emission luminance is such that a change in relative luminance with respect to the maximum light emission luminance is preferably within ± 20%, more preferably within ± 10%. 20% variation in relative luminance
When it exceeds, visibility deteriorates. If the variation in relative luminance is within 10%, the difference in light emission luminance is hardly recognized. FIG. 1 shows the relationship between the relative luminance of the light emitting element and Rel / Ro. As is clear from FIG. 1, Rel / Ro
It can be seen that as the value of becomes larger, the relative luminance approaches 1, and the variation in the luminance decreases. In this example, when Rel / Ro becomes 1000 or more, the relative luminance converges to near 1.

Further, as described above, when the light emitting area increases, the internal resistance Rel of the light emitting element decreases, and the light emission luminance tends to decrease. Therefore, in consideration of the case such that the light emitting elements having different emission areas within one display are mixed, the light emitting area is preferably 35 mm ² or less, more preferably 0.001～20Mm ^2, especially 0.001～15Mm ² is preferable. FIG. 2 shows the relationship between the light emitting area and the relative luminance. As is clear from FIG. 2, the variation in the relative luminance increases as the light emitting area increases. In addition, when a light emitting element having a large light emitting area and a light emitting element having a small light emitting area are mixed, it is found that the larger the difference in the size of the light emitting area is, the larger the luminance variation becomes.

An external resistor Ro connected in series with the light emitting element
Is not particularly limited as long as the Rel / Ro ratio is within the above range, but is preferably 20Ω or less, more preferably 15Ω or less, and particularly preferably 11Ω or less. External resistance R
The value of o is preferably as small as possible, and its lower limit may be 0Ω, but it is usually governed by the on-resistance Ron of the switch element. The ON resistance Ron per switch element is preferably 50 mΩ to 20 Ω, more preferably 50 mΩ to
A range of 15Ω, especially 50 mΩ to 11Ω is preferred. Although the ON resistance Ron of the switch element is preferably as small as possible, it has an ON resistance Ron inherent to the semiconductor material and the element structure, and the lower limit thereof is about 50 mΩ. When the organic EL elements are driven by the switching elements arranged on the power supply side and the GND side, the on resistance Ron of each switching element is added to the external resistance Ro.

Normally, in the case of a controller IC as a display control means, a drive IC as a drive means, or an integrated IC, the on-resistance of a built-in switch element is 60Ω to 80 kΩ. It is difficult to use in the above preferred range.
This is also due to the fact that such an IC does not assume a current-driven device. For this reason, in the present invention, it is preferable to provide an external auxiliary switching element so as to keep the on-resistance Ron low. The ON resistance of such an auxiliary switch element is preferably 50
The range is preferably from mΩ to 20Ω, more preferably from 50 mΩ to 15Ω, particularly preferably from 50 mΩ to 11Ω. In addition, as such an auxiliary switch element, a semiconductor element such as an FET and a bipolar transistor which can operate at high speed, an IC in which these semiconductor elements are modularized, and an element array can be preferably exemplified.

As described above, the internal resistance of the light emitting element of the organic EL display varies depending on the light emitting area and the structure thereof, and is not particularly limited.
MΩ, preferably 600 to 1.5 MΩ, more preferably 600 to 1 MΩ. The external resistor Rr provided for protection or the like is provided as necessary depending on the circuit design, the display to be used, and the like, but is preferably not provided if possible. When an external resistor is provided,
Use about 100Ω.

Next, an example of the configuration of the driving device for an organic EL display of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram showing a basic configuration of a driving device for an organic EL display of the present invention.

In FIG. 1, the driving device for an organic EL display of the present invention converts display data given from outside via a bus 1 or display data stored in a storage medium connected to the bus 1. The display control unit 2 sends a scan electrode drive signal for driving the scan electrode and data electrode of the organic EL display and a data electrode drive signal accordingly. Further, the scanning electrode driving signal and the data electrode driving signal from the display control section 2 cause the organic EL
It has an auxiliary switch element 3 for driving a scanning electrode and a data electrode of the display 4 under the conditions of the present invention. The organic EL display 4 includes one or more sets of scanning electrodes and data electrodes arranged in a matrix and an organic EL layer (organic EL element) existing between the electrodes.

The display controller 2 is provided with a bus 1
It analyzes display data and the like given through the, searches data stored in the storage means and the like as necessary, and converts the display data into matrix data to be displayed at a predetermined position on the organic EL display. 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. Occur.
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 unit 2 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 the control circuit. A timing signal generating circuit (oscillation circuit) for supplying a display timing signal, a read / write timing signal to an external storage means, a storage element control circuit for transmitting and receiving display data from an external storage means, and an external storage element. A drive signal sending circuit that sends out display data that is read out, given externally, or obtained by processing this as a drive signal, and stores data related to a display function provided from outside, a display to be displayed, control commands, and the like. And various registers.

As a device having such a function for driving a display, there is an LCD (liquid crystal display) driving (control) IC, which has been widely used conventionally. Therefore, if such an LCD drive IC (LCD driver) can be used as the display control unit 2, the display control unit 2 can be easily obtained, which is preferable. In other words, it takes a great deal of cost and time to manufacture the display control means 2 having the above function as an element, but by using the above element which has the same function and is inexpensive and can be supplied in large quantities. In addition, the manufacturing cost and time of the device can be greatly reduced, and the manufacturing cost of the display can be reduced.

Such a commercially available LCD driving IC is, for example, SED12 manufactured by Seiko Epson Corporation.
30, SED1278, etc., manufactured by Hitachi, Ltd .: HD
66717, HD66727, etc., manufactured by Toshiba Corporation: T7
934, JT6B03-AS, T6B20, etc., manufactured by NEC Corporation: μPD16306B, μPD16432B
Etc., manufactured by JRC Corporation: NJU6427, NJU642
4 etc., manufactured by Oki Electric Industry Co., Ltd .: MSM6555B-0
2, MSM6665-01 and the like.

By the way, L which is widely used as described above
Since a control device or a drive device of a CD drives a liquid crystal which is a voltage control element, a switch element of a drive circuit having a high on-resistance Ro is often used. Therefore, it is extremely difficult to drive the organic EL display under the above conditions if the organic EL display is directly driven by such an LCD control device or drive device. Therefore, in the present invention, the auxiliary switch element 3 is preferably provided outside, and the light emitting element is turned on / off via the auxiliary switch element 3. By setting the on-resistance of the auxiliary switch element within the above range, driving can be performed under the above conditions.

The auxiliary switch element 3 is operated by a signal for driving the scan electrode and the data electrode of the display control unit 2, and similarly drives the scan electrode and the data electrode of the organic EL display. Although omitted in the illustrated example, a plurality of auxiliary switch elements are used to drive a plurality of scanning electrodes and data electrodes, and are arranged, integrated, modularized, and driven. An IC or the like may be used. This auxiliary switch element 3
Although there is no particular limitation as long as the above-mentioned ON resistance Ro is obtained, a semiconductor element such as a transistor or an FET is usually used, and the mode of use is arbitrary. Organic EL
The organic EL element constituting the display is a light emitting element that emits light by current driving. For this reason, a scan electrode drive signal and a 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.

More specifically, a scan electrode and a data electrode at a predetermined position are driven by using a voltage-current conversion element having a necessary current capacity, an amplification element (power amplification), or the like. Examples of such a driving circuit include an open drain circuit and an open collector circuit, and the driving means preferably used in the present invention is an organic EL display which is driven by an organic EL display in response to a driving pulse (scanning electrode driving signal, data electrode driving signal). The connection of the electrodes of the EL display is switched to the power supply side or the ground side. That is, a drive circuit that is connected to the power supply side (ground side) during non-operation if it is connected to the ground side (power side) during operation is preferable. in this way,
By stabilizing the non-operating portion, for example, even if there is a defective portion in the matrix, the scanning electrode (data electrode) side of that portion is maintained at the H level (L level), thereby preventing generation of a leak current. can do.

As means for switching the connection to the electrode,
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. A plurality (two or more) of these semiconductor elements are provided corresponding to the respective conduction directions so as to be connected to either the power supply side or the ground side, and when one is in an operating state (conductive state), the other is provided. They are connected and arranged to be in a non-operation state (non-conduction state). As such a connection and arrangement method, a totem pole (push-pull) connection is generally known. 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 power supply side and the ground side are connected via elements such as a current limiting resistor and a protection diode.

When the above-described LCD control device or drive device is used as a display control unit, an inversion drive voltage or a plurality of different drive voltages may be applied in view of characteristics inherent to the liquid crystal and wiring efficiency. There is one that adopts a driving method that performs the following. That is, for example, a drive pulse waveform includes two or more voltage levels that change in a plurality of time units with respect to a reference voltage, and outputs a complex rectangular wave. Such a driving pulse is
It is a very effective driving means to drive LCD,
In an organic EL display in which the light emission luminance changes according to the current density, the luminance changes according to the waveform, which is not practical. Therefore, when these elements are used as a control device or a driving device of such an LCD, it is preferable to provide the following signal conversion means.

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 an LCD drive pulse output from an LCD drive IC, and drives an organic EL display in accordance with a state of a signal detected at the plurality of detection levels. Output a signal. Even if the condition of the LCD drive pulse detected at a plurality of detection levels is H level (positive logic),
The signal may be at an L level (negative logic), or may be obtained by inverting any of the outputs after detection. Further, the number of detection levels may be one.

The means for detecting the signal level of the LCD driving pulse is not particularly limited, and a commonly used signal detection method is sufficient. For example, a detection voltage level including a certain error range is set for each of a plurality of signal level voltages of the LCD driving pulse, and output is performed when the signal voltage is detected or not detected at this voltage level. And so on. Whether signal detection is positive logic or negative logic, and whether the output signal corresponding to the detected signal is positive logic,
Whether to use negative logic depends on the LCD driving means 1 or organic EL used.
What is necessary is just to determine suitably according to the kind of a display, etc. Also,
Normally, the signal is converted so that the organic EL display emits light in the signal state for display on the LCD. However, in the display state, the signal may be further displayed in a time division manner.

The means for setting the detection level is not particularly limited either. For example, a power supply voltage or the like is divided by a resistor or the like to obtain a reference voltage, or an impedance element, a diode, a zener diode, or the like may be used instead of the resistor. May be used. Further, a voltage generating device such as a battery may be used, or digital data may be set as digital data for an A / D converted signal.

The set detection level is compared with the LCD driving pulse by comparing means or the like, and is detected as a signal exceeding or lower than this. The comparing means is not particularly limited either. A comparator combining an OP amplifier IC, an operational amplifier applied, an A / D
A processor or the like that compares the converted signal with reference data can be used. Alternatively, a signal level to be detected may be extracted by dividing the LCD drive pulse into a plurality of parts, and may be processed by a logic circuit or the like.

The driving signal of the organic EL display output from the signal conversion means is a driving signal for driving the organic EL display in a single H level state (VH) or L level state (VL) suitable for driving the organic EL display. It becomes a pulse.

Next, the organic EL display 4 used in the present invention will be described.

The organic EL display used in the present invention has, for example, one or more sets of scanning electrodes and data electrodes arranged in a matrix on a substrate, and a hole injection electrode (anode) and a hole are provided between these electrodes. An injection / transport layer, a light emission / electron injection / transport layer, an electron injection electrode (cathode), and a protective layer, if necessary, are laminated, and a sealing plate such as glass is disposed thereon.

The organic EL display of the present invention is not limited to the above configuration examples, but may be of various configurations, and may be of a segment type. For example, a single light emitting layer is provided, and A structure in which an electron injection / transport layer is interposed between the electron injection electrode and the electron injection electrode may be employed. If necessary, the hole injecting / transporting layer and the light emitting layer may be mixed.

The electron injection electrode is formed by sputtering or vacuum evaporation, and the organic layer such as the light emitting layer is formed by vacuum evaporation or the like.
The hole injection electrode can be formed by vapor deposition, sputtering, or the like.Each of these films is patterned by a method such as etching after mask vapor deposition or film formation as necessary, thereby forming a desired light emitting pattern. Obtainable. After forming the electrode, a protective film using an inorganic material such as SiO _X or an organic material such as Teflon may be formed. The protective film may be transparent or opaque,
The thickness of the protective film is about 50 to 1200 nm. The protective film may be formed by a sputtering method, an evaporation method, or the like.

Further, it is preferable to form a sealing layer on the device in order to prevent oxidation of the organic layers and electrodes of the device. The sealing layer is made of an adhesive resin layer such as a commercially available low-moisture-absorbing light-curing adhesive, an epoxy-based adhesive, a silicone-based adhesive, and a cross-linked ethylene-vinyl acetate copolymer adhesive sheet to prevent moisture from entering. Is used to adhere and seal a sealing plate such as a glass plate. Besides a glass plate, a metal plate, a plastic plate or the like can be used.

The light emitting layer has a function of injecting holes (holes) and electrons, a function of transporting them, and a function of generating excitons by recombination of holes and electrons. It is preferable to use a relatively electronically neutral compound for the light emitting layer.

The hole injecting / transporting layer has a function of facilitating the injection of holes from the hole injecting electrode, a function of stably transporting holes, and a function of hindering electrons. These layers have the function of facilitating the injection of electrons, the function of stably transporting electrons, and the function of hindering holes. These layers increase and confine holes and electrons injected into the light emitting layer, and reduce the recombination region. Optimize and improve luminous efficiency.

The thickness of the light emitting layer, the thickness of the hole injecting and transporting layer, and the thickness of the electron injecting and transporting layer are not particularly limited, and vary depending on the forming method.
The thickness is preferably from 0 to 300 nm.

The thickness of the hole injecting / transporting layer and the thickness of the electron injecting / transporting layer depend on the design of the recombination / light emitting region, but may be about the same as the thickness of the light emitting layer or about 1/10 to 10 times. When the injection layer and the transport layer for holes or electrons are separated from each other, the injection layer is preferably 1 nm or more, and the transport layer is preferably 20 nm or more. At this time, the upper limit of the thickness of the injection layer and the transport layer is usually about 500 nm for the injection layer and 5 for the transport layer.
It is about 00 nm. Such a film thickness is the same when two injection / transport layers are provided.

The light emitting layer contains a fluorescent substance which is a compound having a light emitting function. As such a fluorescent substance, for example, at least one kind selected from compounds such as quinacridone, rubrene, styryl dyes and the like as disclosed in JP-A-63-264692 is exemplified. A quinoline derivative such as a metal complex dye having 8-quinolinol or a derivative thereof as a ligand, such as tris (8-quinolinolato) aluminum;
Tetraphenylbutadiene, anthracene, perylene,
Coronene, 12-phthaloperinone derivatives, and the like. Further, a phenylanthracene derivative disclosed in Japanese Patent Application No. 6-110569 and a tetraarylethene derivative disclosed in Japanese Patent Application No. 6-114456 can be used.

Further, it is preferable to use in combination with a host substance capable of emitting light by itself, and it is preferable to use it as a dopant. In such a case, the content of the compound in the light emitting layer is 0.01 to 10% by weight, and more preferably 0.1 to 10% by weight.
It is preferably 1 to 5% by weight. When used in combination with a host substance, the emission wavelength characteristics of the host substance can be changed, light emission shifted to a longer wavelength becomes possible, and the luminous efficiency and stability of the device are improved.

As a substrate material, a transparent or translucent material such as glass, quartz, and resin is used. Further, the emission color may be controlled by using a color filter film, a color conversion film containing a fluorescent substance, or a dielectric reflection film on the substrate.

As the color filter film, a color filter used in a liquid crystal display or the like may be used.
The characteristics of the color filter may be adjusted in accordance with the light emitted from the organic EL to optimize the extraction efficiency and the color purity.

When a color filter capable of cutting off short-wavelength external light that is absorbed by the EL element material or the fluorescent conversion layer is used, the light resistance of the element and the display contrast are improved.

Further, an optical thin film such as a dielectric multilayer film may be used instead of the color filter.

The color conversion film absorbs EL light and emits light from the phosphor in the color conversion film to convert the color of the emitted light. The composition includes a binder,
It is formed from a fluorescent material and a light absorbing material.

The organic EL display is a direct current drive type,
Used as AC drive or pulse drive. The applied voltage for driving is usually about 2 to 20V.

[0054]

As described above, according to the present invention, it is possible to finely adjust the luminance without requiring an additional circuit, a control system, and the like. It has become possible to provide a driving device and a driving method for an organic EL display which can adjust the luminance and have no screen flicker.

The brightness can be adjusted by a simple operation.
In addition, a low-cost organic EL display driving device can be provided.

[Brief description of the drawings]

FIG. 1 shows relative luminance and internal resistance Rel / of an organic EL element.
5 is a graph showing a relationship with an external resistance Ro.

FIG. 2 is a graph showing a relationship between relative luminance and a light emitting area.

FIG. 3 is a block diagram showing a configuration example of a driving device of an organic EL display of the present invention.

FIG. 4 is a diagram showing a series circuit connected to elements of an organic EL display.

FIG. 5 is a diagram showing an equivalent circuit of the circuit of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bus 2 Display control part 3 Auxiliary switch element 4 Organic EL display

Continued on the front page (72) Inventor Mitsunari Suzuki 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation

Claims (3)

[Claims] 1. A circuit comprising at least one set of hole injection electrodes, an electron injection electrode, and an organic EL layer existing between the electrodes, and one circuit formed through at least one set of the hole injection electrodes and the electron injection electrodes. And an electrode driving means for driving the hole injection electrode and the electron injection electrode, wherein the electrode driving means is connected in series with the internal resistance of the light emitting element of the organic EL display = Rel and the light emitting element. A driving device for an organic EL display that is driven under a condition satisfying Rel / Ro ≧ 35, where external resistance = Ro. 2. The organic EL display according to claim 1, wherein the organic EL display has a light emitting element area of 0.001 to 20 mm ^2.
Drive device for L display. 3. An electrode drive unit comprising: a display control unit for controlling an organic EL display to display predetermined data; and an auxiliary switch for driving the organic EL display by operating in accordance with an electrode drive signal from the display control unit. 3. The organic EL device according to claim 1, further comprising an element.
Display drive.