JP2020183968A - Luminance compensation method and display - Google Patents

Abstract

To provide a luminance compensation method for a display including a vertical organic light-emitting transistor in which variation in luminance is suppressed for a long time, and a display.SOLUTION: A luminance compensation method for a display including a plurality of vertical organic light-emitting transistors and a storage unit that stores characteristic information of the vertical organic light-emitting transistors includes a step (A) of applying voltage for luminance inspection to a gate electrode of the vertical organic light-emitting transistor to be corrected, a step (B) of measuring current flowing in a current supply line where current is supplied to a source electrode of the vertical organic light-emitting transistor by applying the voltage for the luminance inspection to a gate electrode of the vertical organic light-emitting transistor to be corrected, and a step (C) of determining a correction value of the voltage to be applied to the gate electrode of the vertical organic light-emitting transistor on the basis of a current value measured in the step (B) and the characteristic information of the vertical organic light-emitting transistor stored in the storage unit.SELECTED DRAWING: Figure 1

Description

The present invention relates to a display luminance compensation method and a display.

In recent years, displays using organic semiconductor elements such as organic light emitting diodes as light source elements have been put into practical use and are now on the market. In the development of displays that use organic semiconductor devices as light sources, studies such as higher brightness, higher definition, lower power consumption, and longer life are still being conducted in order to further improve performance. There is.

Conventionally, a light emitting element of an organic EL display is composed of an organic light emitting diode (also referred to as "OLED") and a transistor that controls a current flowing through the organic light emitting diode. An organic light emitting diode is a device that emits light in response to a current input from a thin film transistor (also referred to as "TFT") formed on a substrate in an organic EL layer sandwiched between an anode electrode and a cathode electrode. is there.

However, with respect to this configuration, Patent Document 1 below describes the current that flows by controlling the voltage applied to the gate electrode as an element for reducing the number of control elements and increasing the light emitting area to increase the brightness. A vertical organic light emitting transistor (also referred to as “VOLET”) that emits light according to the amount of current flowing through the transistor itself is described. Further, Patent Document 2 below describes a display using a vertical organic light emitting transistor, and is expected to significantly increase the brightness of the display.

International Publication No. 2009/036071 Japanese Patent Application Laid-Open No. 2014-505324

Like the field effect transistor, the vertical organic light emitting transistor includes a source electrode, a gate electrode, and a drain electrode, and the source electrode corresponds to the anode electrode and the drain electrode corresponds to the cathode electrode. An EL element and an organic semiconductor layer are formed between the source electrode and the drain electrode, and each electrode is configured to emit light by passing a current through the EL element and the organic semiconductor layer. At least one of the source electrode and the drain electrode is configured to be transparent so that the light obtained by the above can be emitted to the outside.

It is known that when the organic light emitting diode used in the conventional configuration is continuously lit for a long period of time, the deterioration progresses according to the injected current, and the brightness gradually decreases. It is considered that this is due to changes in the interlayer injection efficiency due to chemical changes and charge accumulation at the interface of each organic layer in the organic light emitting diode. The same applies to the EL element sandwiched between the source electrode corresponding to the anode electrode and the drain electrode corresponding to the cathode electrode, and the vertical organic light emitting transistor that emits light by passing a current through the organic semiconductor layer. Is.

However, the present inventor has found through diligent research that a display using a vertical organic light emitting transistor has the following problems. In the vertical organic light emitting transistor, when a voltage is applied to the gate electrode in order to pass a current through the EL element and the organic semiconductor layer to generate an EL, the interface between the gate electrode and the gate insulating film layer, Charges are accumulated at the interface between the source electrode and the organic semiconductor layer, the surface layer, etc., and at each of the gate insulating film layer and the surface layer. Due to the accumulation of electric charges at these interfaces, the vertical organic light emitting transistor is equivalent to the state just manufactured for the organic semiconductor layer or the factory default even when a predetermined voltage is applied to the gate electrode. Since the phenomenon that the electric charge is not injected occurs, the decrease in brightness progresses faster than that of the organic light emitting diode. Therefore, a display using a vertical organic light emitting transistor tends to fluctuate in characteristics in a short period of time and has a short life, so that reliability as a product becomes an issue.

Even if the current flowing through the vertical organic light emitting transistor changes, it is possible to configure a circuit that performs feedback control so that the desired current flows, but a complicated circuit configuration will be added and elements will be arranged. The area to be used is required. That is, the light emitting region becomes small, which hinders the increase in brightness.

In view of the above problems, it is an object of the present invention to provide a brightness compensation method and a display for a display using a vertical organic light emitting transistor that suppresses fluctuations in brightness for a long period of time without adding a complicated circuit configuration.

The display brightness compensation method of the present invention
A brightness compensation method for a display including a plurality of vertical organic light emitting transistors and a storage unit for storing characteristic information of the vertical organic light emitting transistors.
The step (A) of applying a voltage for luminance inspection to the gate electrode of the vertical organic light emitting transistor to be corrected, and
A step of measuring the current flowing through a current supply line that supplies a current to the source electrode of the vertical organic light emitting transistor by applying a voltage for brightness inspection to the gate electrode of the vertical organic light emitting transistor to be corrected. (B) and
Correction of the voltage applied to the gate electrode of the vertical organic light emitting transistor based on the current value measured in the step (B) and the characteristic information of the vertical organic light emitting transistor stored in the storage unit. It is characterized by including a step (C) of determining a value.

The storage unit stores characteristic information of the vertical organic light emitting transistor in the state where the display has just been manufactured or when the display is shipped from the factory. Here, the characteristic information of the vertical organic light emitting transistor is, for example, electron mobility (μ), conductance (gm = Id / Vg), threshold voltage (Vt), and the like. Id indicates the current value flowing between the source electrode and the drain electrode of the vertical organic light emitting transistor, and Vg indicates the voltage applied to the gate electrode of the vertical organic light emitting transistor.

As described above, the current value of the current flowing through the current supply line or each vertical organic light emitting transistor is confirmed, and each vertical organic light emitting transistor is stored in the storage unit so as to flow at a desired current value. The voltage applied to the gate electrode is corrected based on the characteristic information. That is, the current supplied to the organic semiconductor layer of the vertical organic light emitting transistor for a long period of time is adjusted to be a desired current value. Therefore, the fluctuation of the brightness due to the deterioration of the vertical organic light emitting transistor itself is suppressed, and the brightness is compensated for a long time.

The current value may be measured individually for each vertical organic light emitting transistor, or collectively for the vertical organic light emitting transistors arranged in a specific region or on the same line. May be good. By measuring the current value of the current flowing through the source electrode of each vertical organic light emitting transistor and adjusting the voltage applied to the gate electrode, the current flowing through the source electrode can be accurately corrected and the desired brightness can be obtained. Can be done.

However, since a display with a large number of pixels is composed of millions to tens of millions of vertical organic light emitting transistors, it takes a long time to correct all the vertical organic light emitting transistors when corrections are made individually. Resulting in. Then, there is a difference in brightness between the portion where the voltage applied to the gate electrode is corrected and the portion where the correction is not performed, and the image quality tends to be uneven. Therefore, it is preferable that the correction is performed collectively in a short time for the vertical organic light emitting transistors arranged in a specific region or on the same line.

The step (A) of the brightness compensation method may include a step (A1) of cutting off the current supply to the vertical organic light emitting transistor which is not the target of correction.

When performing the steps (A) and (B), the voltage for brightness inspection is applied instead of the voltage corresponding to the image displayed on the gate electrode of the vertical organic light emitting transistor, so that the screen is displayed only for a moment. Unintended display will be performed. At this time, if a bright screen is displayed momentarily, the person looking at the display is likely to feel the flickering of the screen. Therefore, it is preferable to use a dark screen as much as possible.

By using the above method, it is possible to block the path that is the source of the current flowing through the vertical organic light emitting transistor, perform the correction process on a darker screen, and measure the current more accurately. can do.

The step (A) and the step (B) of the luminance compensation method are performed between image update intervals.

The characteristics of the vertical organic light emitting transistor are easily affected by the temperature, and the current value that flows even if the same voltage is applied to the gate electrode of the vertical organic light emitting transistor during operation when the temperature rises compared to when the power is turned on different. Therefore, it is necessary to measure and correct the current value at the operating temperature.

By the above method, the display is applied to the gate electrode of the vertical organic light emitting transistor so as to have a desired brightness while the display starts operating and the temperature rises and the operating temperature rises. By correcting the voltage, it is possible to emit light with the corrected desired brightness. In addition, after the power is turned on, the correction value is determined by one current measurement, the offset voltage of each vertical organic light emitting transistor is obtained and stored, and the gate of the vertical organic light emitting transistor is stored according to the passage of time and temperature. It can also be controlled to offset the voltage applied to the electrodes.

In addition, liquid crystal displays and displays can reduce afterimages when switching from the previous image to the next image by inserting a screen different from the displayed image for a moment during the update interval of the displayed image. It also has an effect.

The step (B) of the brightness compensation method may include a step (B1) of storing the current value measured in the step (B) in the storage unit.

By using the above method, not only the initial characteristic information of each vertical organic light emitting transistor stored in the storage unit but also the difference between the current value measured in the previous process and the corrected voltage value can be adjusted. Can be corrected to do so. Therefore, even immediately after the power is turned on, the image or moving image is displayed in a corrected state based on the current value at the time of the last correction without measuring the current value to the source electrode of the vertical organic light emitting transistor. Can be displayed.

The display of the present invention
Multiple vertical organic light emitting transistors arranged in an array,
A data line that supplies a voltage for controlling the gate electrodes of the plurality of vertical organic light emitting transistors,
A current supply line that supplies current to the source electrodes of the plurality of vertical organic light emitting transistors, and
A first thin film transistor that is connected between the gate electrode of each of the vertical organic light emitting transistors and the data line and controls the voltage supply to the gate electrode of the vertical organic light emitting transistor.
A first gate line connected to the gate electrode of the first thin film transistor and controlling the first thin film transistor,
At least a control unit that controls the voltage applied to the first gate line,
A current measuring unit that measures the current flowing through the current supply line,
It includes a storage unit in which characteristic information of each of the vertical organic light emitting transistors is stored.
The control unit
Controlled so as to apply a voltage for luminance inspection to the gate electrode of the vertical organic light emitting transistor to be corrected.
The current measuring unit
When a voltage for luminance inspection is applied to the gate electrode of the vertical organic light emitting transistor to be corrected, the current flowing through the source electrode of the vertical organic light emitting transistor is measured, and the measured current value is stored in the storage unit. Store in
The control unit
The correction value of the voltage applied to the gate electrode of the vertical organic light emitting transistor is determined based on the measured current value and the characteristic information of the vertical organic light emitting transistor stored in the storage unit. It is a feature.

For example, the control unit controls the voltage of the first gate line so as to turn on the first thin film transistor connected to the vertical organic light emitting transistor to be corrected, and in this on state, the current measuring unit measures the voltage. The correction value of the voltage applied to the data line is determined from the current value of the current supply line and the characteristic information of the vertical organic light emitting transistor stored in the storage unit. As a result, the brightness of the vertical organic light emitting transistor to be corrected can be corrected.

According to the above configuration, the voltage applied to the data line to display the desired image can be adjusted. As a result, the current value flowing through the vertical organic light emitting transistor is corrected, a display whose image quality and brightness do not fluctuate even when used for a long time can be configured, and the brightness can be compensated for lighting for a long time.

In the display, a dielectric layer may be formed between the gate electrode and the source electrode of the vertical organic light emitting transistor.

In the image displayed on the display, the on / off state of the first thin film transistor connected to each vertical organic light emitting transistor is sequentially switched, and the desired voltage is applied to the gate electrode of the vertical organic light emitting transistor according to each pixel. Is applied to update. At this time, after the voltage application of the gate electrode of the vertical organic light emitting transistor is completed and the first thin film transistor is switched to the off state, the vertical organic light emitting transistor must maintain its brightness for a predetermined time. .. That is, in order to maintain the current flowing through the vertical organic light emitting transistor, it is necessary to maintain the voltage between the gate electrode and the source electrode of the vertical organic light emitting transistor.

For that purpose, an element that maintains an electric charge, such as a capacitor, must be connected between the gate electrode and the source electrode of the vertical organic light emitting transistor. If a capacitor configured as a semiconductor circuit is used to obtain a capacitance value for maintaining a voltage, the element becomes very large and the light emitting region is compressed.

Therefore, with the above configuration, a capacitor can be configured as a parasitic element in the vertical organic light emitting transistor which is formed large in order to increase the light emitting region. That is, since it is not necessary to separately connect a capacitor for maintaining voltage and the light emitting region is not pressed, a display having higher brightness can be configured.

In the vertical organic light emitting transistor of the display, the source electrode and / or the drain electrode may be formed of a conductive material containing carbon.

Further, in the vertical organic light emitting transistor of the display, the source electrode and / or the drain electrode may be formed of carbon nanotubes (also referred to as “CNT”).

Conductive materials containing carbon, particularly carbon nanotubes, can form a conductive film having high current density resistance and translucency with respect to visible light. Therefore, by using the above-mentioned material, it is possible to construct a vertical organic light emitting transistor which has transparency to visible light and can pass a large current. In addition, since carbon nanotubes have high mechanical strength, it is possible to form a flexible display.

The above display is
A second thin film transistor that is connected between the source electrode of the vertical organic light emitting transistor and the current supply line and controls the current supply to the source electrode of the vertical organic light emitting transistor.
A second gate line connected to the gate electrode of the second thin film transistor and controlling the second thin film transistor is provided.
The control unit may control the second thin film transistor connected to the vertical organic light emitting transistor, which is not the target of correction, to be in the off state.

Further, the second thin film transistor of the display may be made of an oxide semiconductor.

During normal operation, the second thin film transistor, which is in the on state, is switched to the off state, so that the supply path of the current flowing through the vertical organic light emitting transistor can be cut off. Further, by forming the second thin film transistor with an oxide semiconductor having a small minute current (leakage current) that flows even in the off state, the current flowing through the vertical organic light emitting transistor that is not the correction target can be further reduced. Can be done.

According to the present invention, a brightness compensation method and a display for a display using a vertical organic light emitting transistor that suppresses fluctuations in brightness for a long period of time are realized without adding a complicated circuit configuration.

It is a schematic block diagram of a part of one Embodiment of a display. It is a circuit diagram of the light emitting part of FIG. It is a block diagram of the control part of FIG. It is the top view of the typical element composition of the light emitting part constructed on a substrate. It is a side view of the light emitting part of FIG. It is a flowchart which shows the brightness correction procedure of a display. It is a schematic block diagram of a part of another embodiment of a display.

Hereinafter, the configuration of the display of the present invention will be described with reference to the drawings. In addition, each of the following drawings is schematically illustrated, and the dimensional ratio and the number on the drawings do not always match the actual dimensional ratio and the number.

[Constitution]
First, the configuration of the display will be described. FIG. 1 is a schematic configuration diagram of a part of an embodiment of the display 1. As shown in FIG. 1, the display 1 of the present embodiment includes a light emitting unit 10 including vertical organic light emitting transistors arranged in an array, and a data line 11 for supplying a current to a gate electrode of the vertical organic light emitting transistors. , A current supply line 12 that supplies a current to the source electrode of the vertical organic light emitting transistor, a first gate line 13 that controls the first thin film transistor, a second gate line 14 that controls the second thin film transistor, and a control unit 15. A current measuring unit 16 for measuring the current flowing through the current supply line 12 and a storage unit 17 are provided.

FIG. 2 is a circuit diagram of the light emitting unit 10 of FIG. As shown in FIG. 2, the light emitting unit 10 includes a vertical organic light emitting transistor 20, a first thin film transistor 21 that controls voltage supply to the gate electrode of the vertical organic light emitting transistor 20, and a source of the vertical organic light emitting transistor 20. It includes a second thin film transistor 22 that controls the current supply to the electrodes, and a capacitor 23 that is connected between the source electrode and the gate electrode of the vertical organic light emitting transistor 20.

The data line 11 is for applying a voltage to the gate electrode of the vertical organic light emitting transistor 20 via the first thin film transistor 21 in order to adjust the light emission brightness of the vertical organic light emitting transistor 20 according to the image to be displayed. It is wiring. The current supply line 12 is a wiring for supplying a current to the source electrode of the vertical organic light emitting transistor 20 via the second thin film transistor 22.

The first gate line 13 is connected to the gate electrode of the first thin film transistor 21 and controls the on / off of the first thin film transistor 21, that is, controls the energization between the gate electrode of the vertical organic light emitting transistor 20 and the data line 11. To do. The second gate line 14 is connected to the gate electrode of the second thin film transistor 22 to control the on / off of the second thin film transistor 22, that is, energize the source electrode of the vertical organic light emitting transistor 20 and the current supply line 12. Control.

The current measuring unit 16 is arranged so as to measure the total value of the amount of current flowing through the light emitting unit 10 (vertical organic light emitting transistor 20) connected to the same current supply line 12.

FIG. 3 is a configuration diagram of the control unit 15 of FIG. As shown in FIG. 3, the control unit 15 includes a plurality of gate drivers 15a for driving the data line 11, a plurality of source drivers 15b for driving the current supply line 12, the voltage of the first gate line 13, and the second gate line 14. A plurality of gate controllers 15c for controlling the voltage of the above, a data input / output circuit 15d that receives the current value measured by the current measuring unit 16 and stores it in the storage unit 17, and a current value and a storage unit measured by the current measuring unit 16. The arithmetic processing circuit 15e for calculating the correction value of the voltage applied to the gate electrode of the vertical organic light emitting transistor 20 from the characteristic information of the vertical organic light emitting transistor 20 stored in 17 is provided. Details regarding control will be described later in the item of control method.

The specific configuration of each block constituting the control unit 15 is composed of a dedicated circuit, a processor controlled by a software program, or a combination thereof. For example, the dedicated circuit is a logic circuit that generates a control signal configured on the same substrate as the vertical organic light emitting transistor 20, a driver circuit for driving each vertical organic light emitting transistor 20, or each line (11, 12). , 13, 14) and programmable devices (PLD, CPLD, FPGA) that can be constructed so that they can be electrically connected to a dedicated integrated circuit (Application Special Integrated Circuit, abbreviated as ASIC) or a dedicated circuit can be constructed by programming. ) Etc. may be used.

The processor may be a central processing unit (abbreviated as Central Processing Unit, CPU), another general-purpose processor, a digital signal processor (abbreviated as Digital Signal Processor, DSP), an ASIC, or the like. Further, the general-purpose processor may be a microprocessor, and the processor may be any standard processor or the like. The steps of the various processes may be executed directly by the hardware processor, or may be executed by a combination of hardware and software (or software function modules) in the processor. Further, a control device such as a microcontroller may be used.

The storage unit 17 may include a high-speed RAM memory, and may be realized by any type of volatile or non-volatile storage device or a combination thereof. For example, static random access memory (SRAM), electrically erasable programming read-only memory (EEPROM), erasable programming read-only memory (EPROM), programming read-only memory (PROM), read-only memory (ROM), magnetic memory. , Flash memory, magnetic disk, optical disk and the like.

The capacitor 23 is arranged to maintain the displayed image for a predetermined time while the first thin film transistor 21 is in the off state, and is a voltage between the gate electrode and the source electrode of the vertical organic light emitting transistor 20. It is a holding element.

Next, the structure of each element formed on the substrate will be described. FIG. 4 is a top view of a schematic element configuration of the light emitting unit 10 configured on the substrate 30. FIG. 5 is a side view of the light emitting unit 10 of FIG. As shown in FIGS. 4 and 5, the vertical organic light emitting transistor 20, the first thin film transistor 21 and the second thin film transistor 22 are separated by a data line 11, a current supply line 12, a first gate line 13, and a second gate line 14. It is formed in the area.

For the substrate 30, a glass material or a material such as PET (Poly Ethylene Terephthalate), PEN (Poly Ethylene Naphthalate), or a plastic material such as polyimide can be adopted.

In the following description, the direction in which the data line 11 and the current supply line 12 are wired is the X direction, the direction in which the first gate line 13 and the second gate line 14 are wired is the Y direction, and the direction orthogonal to these is defined. The Z direction will be described as the upper layer side in the direction away from the substrate 30 (+ Z direction).

The configuration of the vertical organic light emitting transistor 20 is a conductive material containing carbon on the surfaces of the drain electrode layer 20d corresponding to the cathode electrode, the organic EL layer 20c, the organic semiconductor layer 20a, and the surface layer 31 from the upper layer (in the present embodiment). , Carbon nanotubes) are applied to the source electrode layer 20s, and a gate electrode layer 20g is formed below the source electrode layer 20s via a gate insulating film layer 20h composed of a dielectric material. When a voltage is applied to the gate electrode layer 20g, the Schottky barrier between the organic semiconductor layer 20a and the source electrode layer 20s changes, and when a predetermined threshold is exceeded, the source electrode layer 20s to the organic semiconductor layer 20a A current flows and the vertical organic light emitting transistor 20 emits light.

In the display 1 of the present embodiment, the substrate 30 is made of a material that is transparent to visible light, and the gate electrode layer 20 g and the source electrode layer 20s are configured to have a gap through which visible light can pass. By doing so, the light emitted from the organic semiconductor layer 20a passes through the substrate 30 and is emitted to the outside to display an image. As described above, the method of passing light through the substrate 30 to emit light is also called a "bottom emission method", and has an advantage that wiring connection between electrodes is easy and manufacturing is easy.

In the first thin film transistor 21 and the second thin film transistor 22, the source electrode layer (21s, 22s) and the drain electrode layer (21d, 22d) are connected via the oxide semiconductor layer (21a, 22a), respectively, and the oxide semiconductor layer (21d, 22d) is connected. A gate electrode layer (21 g, 22 g) is formed in the lower layer of 21a, 22a) via an insulating layer or a dielectric layer. When a voltage is applied to the gate electrode layers (21 g, 22 g), channels are formed in the oxide semiconductor layers (21a, 22a), respectively, and the source electrode layer (21s, 22s) and the drain electrode layer (21d, 22d) are formed. Is energized.

In the first thin film transistor 21, the source electrode layer 21s is connected to the data line 11, and the drain electrode layer 21d is connected to the gate electrode layer 20g of the vertical organic light emitting transistor 20. In the second thin film transistor 22, the source electrode layer 22s is connected to the current supply line 12, and the drain electrode layer 22d is connected to the source electrode layer 20s of the vertical organic light emitting transistor 20. In the first thin film transistor 21, the source electrode layer 21s may be connected to the gate electrode layer 20g of the vertical organic light emitting transistor 20, and the drain electrode layer 21d may be connected to the data line 11.

As shown in FIG. 4, the vertical organic light emitting transistor 20 is formed so that the light emitting region is as large as possible in order to realize high brightness, and the first thin film transistor 21 and the second thin film 22 are vertical organic light emitting transistors. It is formed as small as possible at the corners of the divided regions so that the influence on the 20 light emitting regions is small.

Although the capacitor 23 is not shown in FIGS. 4 and 5, as shown in FIG. 5, in the vertical organic light emitting transistor 20 of the present embodiment, the source electrode layer 20s and the gate electrode layer 20g are the gate insulating film layer 20h. A capacitor 23 as a parasitic element is provided by being arranged so as to face each other via the above. If the capacitance value of the capacitor 23 of such a parasitic element is insufficient, another capacitor may be additionally formed.

The materials used for each layer are listed below as examples.

Drain electrode layer 20d of the vertical organic light emitting transistor 20 is a single layer or a multi-graphene, carbon nanotubes, aluminum (Al), lithium fluoride (LiF), molybdenum oxide (Mo _X O _Y), indium tin oxide (ITO), Zinc oxide (ZnO) or the like can be adopted.

The gate electrode layer 20 g of the vertical organic light emitting transistor 20 is made of zinc oxide (ZnO) doped with a metal such as aluminum (Al), tin (Sn), yttrium (Y), scandium (Sc), gallium (Ga), etc. Metal-dopeds such as indium oxide (In ₂ O ₃ ), tin dioxide (SnO ₂ ), cadmium oxide (CdO), non-doped transparent conductive oxides and materials containing these combinations, or aluminum (Al), gold ( Au), silver (Ag), platinum (Pt), cadmium (Cd), nickel (Ni) and tantalum (Ta), and combinations thereof, as well as p or n-doped silicon (Si) and gallium arsenic (GaAs). Etc. can be adopted.

The gate insulating film layer 20h between the surface layer 31 of the vertical organic light emitting transistor 20 and the gate electrode layer 20 g is made of silicon oxide (SiO _X ), aluminum oxide (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), and the like. Yttrium oxide (Y ₂ O ₃ ), lead titanate (PbTiO _X ), aluminum titanate (AlTIO _X ), glass and parylene polymers, polystyrene, polyimide, polyvinylphenol, polymethylmethacrylate, fluoropolymers and other organic compounds are used. Can be done.

The organic semiconductor layer 20a of the vertical organic light emitting transistor 20 includes linear condensed polycyclic aromatic compounds (or acene compounds) such as naphthalene, anthracene, rubrene, tetracene, pentacene, hexacene, and derivatives thereof, and, for example, copper phthalocyanine ( CuPc) -based compounds, azo compounds, perylene-based compounds, and pigments such as derivatives thereof, and pigments such as hydrazone compounds, triphenylmethane-based compounds, diphenylmethane-based compounds, stillben-based compounds, allylvinyl compounds, pyrazoline-based compounds, triphenylamine. Derivatives (TPD), allylamine compounds, low molecular weight amine derivatives (a-NPD), 2,2', 7,7'-tetrakis (diphenylamino) -9,9'-spirobifluorene (spiro-TAD), N, N'-di (1-naphthyl) -N, N'-diphenyl-4,4'-diamonobiphenyl (spiro-NPB), 4,4', 4 "-tris [N-3-methylphenyl-N- Phenylamino] Triphenylamine (mMTDATA), 2,2', 7,7'-tetrakis (2,2-diphenylvinyl) -9,9-spirobifluorene (spiro-DPVBi), 4,4'-bis ( 2,2-Diphenylvinyl) biphenyl (DPVBi), (8-quinolinolato) aluminum (Alq), tris (8-quinolinolato) aluminum (Alq3), tris (4-methyl-8 quinolinolato) aluminum (Almq3), and these. Low molecular weight compounds such as derivatives and, for example, polythiophene, poly (p-phenylene vinylene) (PPV), biphenyl group-containing polymers, dialkoxy group-containing polymers, alkoxyphenyl PPV, phenyl PPV, phenyl / dialkoshiki PPV copolymers, poly ( 2-methoxy-5- (2'-ethylhexyloxy) -1,4-phenylene vinylene) (MEH-PPV), poly (ethylenedioxythiophene) (PEDOT), poly (styrene sulfonic acid) (PSS), poly ( Aniline) (PAM), poly (N-vinylcarbazole), poly (N-vinylcarbazole), poly (vinylpyrene), poly (vinylanthracene), pyreneformaldehyde resin, ethylcarbazoleformaldehyde halide resin, and modified products thereof. Such polymer compounds and, for example, 5,5_-diperfluorohexylcarbonyl-2,2_: 5_, 2_: 5_, 2_-quaterthiophene (DFHCO-4). T), DFH-4T, DFCO-4T, P (NDI2OD-T2), PDI8-CN2, PDIF-CN2, F16CuPc, and n-type transport organic small molecules, oligomers such as fullerene, naphthalene, perylene, and oligothiophene derivatives. Or polymers, as well as thieno [3,2-b] thiophene, dinaphthyl [2,3-b: 2', 3'-f] thieno [3,2-b] thiophene (DNTT), 2-decyl- Aromatic compounds having a thiophene ring such as 7-phenyl [1] benzothioeno [3,2-b] [1] benzothiophene (BTBT) can be adopted.

Here, the vertical organic light emitting transistor 20 has a hole injection layer, a hole transport layer, an organic EL layer, which are used as standard in an OLED display by appropriately selecting an organic semiconductor having a matching energy level. An electron transport layer, an electron injection layer, or the like can be preferably used. Then, the color of the light emitted to the outside is adjusted so as to emit light of colors such as red, green, and blue by selecting the material constituting the above-mentioned organic EL layer 20c. Further, the vertical organic light emitting transistor 20 may be configured to emit white light, and the same vertical organic light emitting transistor 20 may be used to select and emit light of a desired color with a color filter. You can also do it.

The surface layer 31 is a layer formed on the gate insulating film layer 20h for the purpose of fixing the source electrode layer 20s (particularly, the CNT layer). The material for forming the surface layer 31 can be formed by applying a composition containing a binder resin formed of a silane coupling material, an acrylic resin, or the like.

The oxide semiconductor layers (21a, 22a) composed of the first thin film 21 and the second thin film 22 are In-Ga-Zn-O-based semiconductors, Zn-O-based semiconductors (ZnO), and In-Zn-O-based semiconductors. (IZO®), Zn-Ti-O-based semiconductor (ZTO), Cd-Ge-O-based semiconductor, Cd-Pb-O-based semiconductor, CdO (cadmium oxide), Mg-Zn-O-based semiconductor, In -Sn-Zn-O-based semiconductors (for example, In ₂ O ₃ -SnO _2- ZnO), In-Ga-Sn-O-based semiconductors, and the like can be adopted.

In the present embodiment, the first thin film transistor 21 and the second thin film transistor 22 are thin film transistors made of oxide semiconductors, but thin film transistors made of amorphous silicon may be used. Further, it may be either p-type or n-type. Further, as a specific configuration, any configuration such as a staggered type, an inverted staggered type, a coplanar type, and an inverted coplanar type can be adopted.

As the vertical organic light emitting transistor 20, the vertical organic light emitting transistor 20 described in Patent Documents 1 and 2 can also be adopted.

[Control method]
Finally, a display control method will be described. In the present embodiment, as shown in FIG. 1, the light emitting units 10 are arranged in an array, and the columns in the vertical direction in FIG. 1 share the data line 11 and the current supply line 12, and the columns in the horizontal direction in FIG. The first gate line 13 and the second gate line 14 are shared.

In the following description, on the premise of the above configuration, the light emitting unit 10 to be corrected at one time will be described with a combination of one row in the horizontal direction in FIG. 1 sharing the first gate line 13 and the second gate line 14. However, the light emitting unit 10 to be corrected at one time may be corrected at the same time by a plurality of combinations in the lateral direction in FIG. 1 sharing the first gate line 13, or the light emitting unit 10 alone may be corrected in order. Absent.

Further, the luminance compensation method in the present embodiment is performed between the displayed image and the update interval of the image for displaying the next image while the display 1 is displaying the image. The brightness compensation method described below may be performed at any timing, or may be performed at regular time intervals from the time when the power is turned on or when the power is turned on.

FIG. 5 is a flowchart showing a brightness correction procedure of the display 1. As shown in FIG. 5, when the correction control is started from the state where the display 1 is performing a normal image display, the gate controller 15c of the control unit 15 is connected to the vertical organic light emitting transistor 20 to be corrected. The second thin film transistor 22 is turned on, and the second thin film transistor 22 connected to the vertical organic light emitting transistor 20 that is not to be corrected is switched to the off state (S1).

After performing step S1, the gate controller 15c of the control unit 15 turns on the first thin film transistor 21 connected to the vertical organic light emitting transistor 20 to be corrected and connects it to the vertical organic light emitting transistor 20 not to be corrected. The first thin film transistor 21 is switched to the off state (S2). By controlling the control unit 15 in this way, no voltage is applied to the gate electrode of the vertical organic light emitting transistor 20 which is not the correction target, and no current is supplied to the source electrode.

In the state controlled as described above, the luminance inspection voltage is applied to the data line 11 connected to the first thin film transistor 21 in the on state or all the data lines 11 (S3). Then, the total of the current values when the luminance inspection voltage is applied to the vertical organic light emitting transistor 20 to be corrected flows through the current supply line 12.

Therefore, the current measuring unit 16 measures the current connected to the current supply line 12 connected to the second thin film transistor 22 in the ON state, or all the current supply lines 12 (S4). At this time, ideally, when a voltage for brightness inspection is applied to the gate electrode of the second thin film transistor 22, the current value flowing from the current supply line 12 toward the source electrode is corrected by the vertical organic light emission. The current value multiplied by the number of transistors 20 is measured.

Specific methods for measuring the current value include, for example, a method of measuring the current value with an A / D converter, or a method of arranging a resistor on the current supply line 12 and setting the voltage appearing across the resistor to a desired voltage. When a method for comparing with the value or a diversion path is prepared and a predetermined current value is passed through the current supply line 12, the current flowing through the diversion path without flowing through each vertical organic light emitting transistor is measured with a current meter. , There is a method of measuring the difference from the supplied predetermined current value.

The control unit 15 acquires the current value (I ₁ ) with respect to the luminance inspection voltage (Vc) actually measured as characteristic information by the data input / output circuit 15d, and stores it in the storage unit 17. At this time, the data input / output circuit 15d of the control unit 15 reads out the current value (I ₀ ) from the storage unit 17 with respect to the freshly manufactured state or the factory-shipped luminance inspection voltage (Vc). Then, the arithmetic processing circuit 15e confirms the deviation from the characteristic information, and corrects the voltage applied to the data line 11 so that the deviation (ΔI = I ₁ −I ₀ ) of the generated current value becomes small. Determine (S5). The characteristic information used for the comparison at this time may be the conductance (gm ₁ = I ₁ / Vc) calculated by the arithmetic processing circuit 15e conductance.

When the correction value is determined, the process returns to the normal image display control, the gate controller 15c of the control unit 15 switches the second thin film transistor 22 to the ON state, and the gate driver 15a of the control unit 15 responds to the image to be displayed. A corrected voltage, which is a voltage, is applied to the data line 11.

By applying the corrected voltage value to the gate electrode of the vertical organic light emitting transistor 20 in this way, due to deterioration, the expected current does not flow to the source electrode with respect to the voltage applied to the gate electrode. Even in this case, the control of the gate electrode is corrected so that the expected current value is obtained, the change in brightness can be suppressed, and the brightness can be compensated for lighting for a long period of time.

Further, in the luminance compensation method of the present embodiment, as described above, almost no current flows through the vertical organic light emitting transistor 20 which is not the correction target. Therefore, when the correction control is performed at one time, the light emitting unit 10 emits a small amount of light only in the horizontal row in FIG. 1 that shares the first gate line 13 and the second gate line 14, but other The vertical organic light emitting transistor 20 is turned off. Therefore, a black screen can be inserted at the image update interval.

By displaying a black screen at the image update interval, the liquid crystal display or display inserts a screen different from the image displayed during the displayed image update interval for a moment, thereby changing from the previous image to the next image. Afterimages when switching to are reduced. By the above method, the display can display an image or a moving image more clearly by suppressing an afterimage.

[Another Embodiment]
Hereinafter, another embodiment will be described.

<1> The correction value may be determined based on the current value or conductance measured at the time of the previous correction control stored in the storage unit 17. Based on the value measured at the time of the previous correction control, the display 1 can also be used for correcting the correction value according to the passage of time and for detecting a defect.

<2> FIG. 7 is a schematic configuration diagram of a part of another embodiment of the display 1. As shown in FIG. 7, the display 1 of the present invention may not be provided with the second thin film transistor 22. The second thin film transistor 22 cuts off the current path so that the current does not flow through the vertical organic light emitting transistor 20 which is not the target of correction. That is, if the current flowing through the vertical organic light emitting transistor 20 that is not the correction target is very small and does not become a large value that affects the correction calculation, the second thin film transistor 22 may not be provided. I do not care.

With the above configuration, wiring and elements can be reduced, and the light emitting region can be further increased. Therefore, a display 1 having higher brightness can be realized.

<3> The display 1 may be configured so that the light emitted from the organic semiconductor layer 20a is emitted to the side opposite to the substrate 30 to display an image. This configuration is also referred to as a "top emission method", and has an advantage that an element can be configured between the vertical organic light emitting transistor 20 and the substrate 30.

<4> The configuration included in the display 1 described above is merely an example, and the present invention is not limited to each of the illustrated configurations.

1: Display 10: Light emitting unit 11: Data line 12: Current supply line 13: First gate line 14: Second gate line 15: Control unit 15a: Gate driver 15b: Source driver 15c: Gate controller 15d: Data input / output circuit 15e: Arithmetic processing circuit 16: Current measuring unit 17: Storage unit 20: Vertical organic light emitting transistor 20a: Organic semiconductor layer 20d: Drain electrode layer 20g: Gate electrode layer 20h: Gate insulating film layer 20s: Source electrode layer 21: No. One thin film transistor 21a: Oxide semiconductor layer 21d: Drain electrode layer 21g: Gate electrode layer 21s: Source electrode layer 22: Second thin film transistor 22a: Oxide semiconductor layer 22d: Drain electrode layer 22g: Gate electrode layer 22s: Source electrode layer 23 : Capacitor 24: Bank layer 30: Substrate 31: Surface layer

Claims (10)

A brightness compensation method for a display including a plurality of vertical organic light emitting transistors and a storage unit for storing characteristic information of the vertical organic light emitting transistors.
The step (A) of applying a voltage for luminance inspection to the gate electrode of the vertical organic light emitting transistor to be corrected, and
A step of measuring the current flowing through a current supply line that supplies a current to the source electrode of the vertical organic light emitting transistor by applying a voltage for brightness inspection to the gate electrode of the vertical organic light emitting transistor to be corrected. (B) and
Correction of the voltage applied to the gate electrode of the vertical organic light emitting transistor based on the current value measured in the step (B) and the characteristic information of the vertical organic light emitting transistor stored in the storage unit. A display brightness compensation method comprising the step (C) of determining a value. The brightness compensation method for a display according to claim 1, wherein the step (A) includes a step (A1) of cutting off the supply of a current to the vertical organic light emitting transistor which is not a correction target. The brightness compensation method for a display according to claim 1 or 2, wherein the step (A) and the step (B) are performed between image update intervals. The display according to any one of claims 1 to 3, wherein the step (B) includes a step (B1) of storing the current value measured in the step (B) in the storage unit. Brightness compensation method. With multiple vertical organic light emitting transistors
A data line that supplies a voltage for controlling the gate electrodes of the plurality of vertical organic light emitting transistors,
A current supply line that supplies current to the source electrodes of the plurality of vertical organic light emitting transistors, and
A first thin film transistor that is connected between the gate electrode of each of the vertical organic light emitting transistors and the data line and controls the voltage supply to the gate electrode of the vertical organic light emitting transistor.
A first gate line connected to the gate electrode of the first thin film transistor and controlling the first thin film transistor,
At least a control unit that controls the voltage applied to the first gate line,
A current measuring unit that measures the current flowing through the current supply line,
It is provided with a storage unit in which characteristic information of each of the vertical organic light emitting transistors is stored.
The control unit
Controlled so as to apply a voltage for luminance inspection to the gate electrode of the vertical organic light emitting transistor to be corrected.
The current measuring unit
When a voltage for luminance inspection is applied to the gate electrode of the vertical organic light emitting transistor to be corrected, the current flowing through the source electrode of the vertical organic light emitting transistor is measured, and the measured current value is stored in the storage unit. Store in
The control unit
The correction value of the voltage applied to the gate electrode of the vertical organic light emitting transistor is determined based on the measured current value and the characteristic information of the vertical organic light emitting transistor stored in the storage unit. Characteristic display. The display according to claim 5, wherein a dielectric layer is formed between the gate electrode and the source electrode of the vertical organic light emitting transistor. The display according to claim 5 or 6, wherein at least one of the vertical organic light emitting transistor selected from the source electrode and the drain electrode is formed of a conductive material containing carbon. The display according to claim 7, wherein at least one of the vertical organic light emitting transistors selected from the source electrode and the drain electrode is formed of carbon nanotubes. A second thin film transistor that is connected between the source electrode of the vertical organic light emitting transistor and the current supply line and controls the current supply to the source electrode of the vertical organic light emitting transistor.
A second gate line connected to the gate electrode of the second thin film transistor and controlling the second thin film transistor is provided.
The control unit according to any one of claims 5 to 8, wherein the control unit controls the second thin film transistor connected to the vertical organic light emitting transistor to be corrected so as to be in an off state. Display. The display according to claim 9, wherein the second thin film transistor is made of an oxide semiconductor.

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