JP2006003552A - Light emitting device - Google Patents

Light emitting device Download PDF

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JP2006003552A
JP2006003552A JP2004178629A JP2004178629A JP2006003552A JP 2006003552 A JP2006003552 A JP 2006003552A JP 2004178629 A JP2004178629 A JP 2004178629A JP 2004178629 A JP2004178629 A JP 2004178629A JP 2006003552 A JP2006003552 A JP 2006003552A
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light emitting
light
emitting device
transistor
emitting element
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Rei Ono
玲 大野
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Mitsubishi Chemicals Corp
三菱化学株式会社
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Abstract

<P>PROBLEM TO BE SOLVED: To more enhance a light emission efficiency than heretofore by a simple configuration in a light emitting device of a current driving system using a transistor 4 as a driving element, as represented by an active matrix system. <P>SOLUTION: In the light emitting device equipped with a light emitting element 2 and a driving circuit 3 for driving the light emitting element 2, a transistor 4 is interposed in the driving circuit 3 and a substance of which the electric resistance is lowered by the light emitted by the light emitting element 2 is incorporated into a current route of the transistor 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting device. Specifically, the present invention relates to a light-emitting device that includes a light-emitting element and a drive circuit that drives the light-emitting element, and includes a transistor interposed in the drive circuit.

  Conventionally, in the field of light emitting devices, there is a problem of how much the amount of light extracted outside the device per unit power consumption, that is, the number of photons (referred to as “light emission efficiency”) can be increased. .

  Conventionally, for the purpose of increasing the light emission efficiency of a light emitting device, (i) increasing the light emission efficiency of the light emitting element itself (for example, Patent Document 1, Patent Document 2, etc.), (ii) Filter, sealant, reflector For example, measures have been taken to improve the material of the light passage portion such as (for example, Patent Document 3).

  On the other hand, as represented by the active matrix method, a technology for driving a light emitting element such as a light emitting diode (hereinafter referred to as “LED” as appropriate) or an electroluminescent element (hereinafter referred to as “EL element” as appropriate) by current is put into practical use. (For example, Patent Document 4). Further, the drive method itself by the active matrix method is most often used in a liquid crystal display or the like. Here, “driving” means that the element is caused to emit light using an output corresponding to an input such as voltage application, particularly an amplified current. As an element (drive element) for controlling the drive circuit, a transistor, in particular, a field effect transistor is used.

  FIG. 1 is a diagram schematically showing a configuration of a main part of a basic unit (hereinafter, referred to as a “light emitting unit” as appropriate) of a four-terminal TFT device which is an example of a conventional light emitting device using an active matrix method. It is. The light emitting unit 1 shown in FIG. 1 includes a light emitting element 2 such as an LED or an EL element that emits light by current, and a driving circuit 3 for driving the light emitting element 2, and a driving transistor 4 is included in the driving circuit 3. Intervened. The light emitting unit 1 is further provided with a switching transistor 5 and a storage capacitor 6. As the driving transistor 4 and the switching transistor 5, a field-effect transistor (hereinafter sometimes abbreviated as "FET") is usually used. This light emission unit 1 corresponds to, for example, one pixel of a TFT device, and usually a large number of the light emission units 1 are combined, and further combined with an optical filter, a power supply device, a casing, an arithmetic circuit, etc. (not shown) as appropriate. A light emitting device such as a TFT device is formed.

  In the TFT device, a plurality of conductive wires (referred to as “source lines” and “gate lines”, respectively, shown in FIG. 1 as “SL” and “GL”) are stretched in two directions, the X-axis direction and the Y-axis direction. The light emission unit 1 is arranged at the intersection of each source line and each gate line. Then, by applying a voltage from two directions, the X-axis direction and the Y-axis direction, the address of the light-emitting element 2 existing at the intersection can be designated and excited. Here, the addressing signal for excitation of the light emitting element 2 can be separated by using the four-terminal method. Each light emitting element 2 is selected via a switching transistor 4, and the excitation power for the light emitting element 2 is controlled by a driving transistor 5. The storage capacitor 6 has a function of accumulating excitation power for the addressed light emitting element 2. With this storage capacitor 6, the duty cycle can be almost 100% regardless of the addressing duration.

JP 2004-14335 A JP 2004-26995 A Japanese Patent Laid-Open No. 2004-47748 Japanese Patent Laid-Open No. 11-8065

  However, even in a light emitting device such as a display or illumination that uses a transistor as a driving element, represented by an active matrix method, improvement in light emission efficiency is desired. However, only prior art means such as Patent Documents 1 to 3 are desired. Then, there was a limit to the improvement of luminous efficiency.

  The present invention was devised in view of the above problems, and an object of the present invention is a current-driven light-emitting device that uses a transistor as a drive element, typified by an active matrix method, and has a simple configuration as compared with the conventional one. The object is to provide an excellent light emitting device with improved luminous efficiency.

  As a result of intensive studies to solve the above problems, the present inventors have found that a substance (photosensitive electrical resistance) whose electrical resistance is reduced by light emitted from the light emitting element is connected to the current path of the transistor interposed in the drive circuit of the light emitting element. The photon emitted from the light-emitting element by containing a reducing substance), which has previously contributed to energy loss, contributes to lowering the electrical resistance of the current path of the transistor, thereby greatly improving the luminous efficiency. The present invention has been completed by finding that the above-mentioned problems can be effectively solved.

That is, the gist of the present invention is a light-emitting device including a light-emitting element and a drive circuit that drives the light-emitting element. A transistor is interposed in the drive circuit, and a current path of the transistor is The present invention resides in a light emitting device characterized by containing a substance whose electric resistance is lowered by light emitted from the light emitting element (hereinafter referred to as “photosensitive electric resistance lowering substance”).
Here, when the transistor is a field effect transistor, it is preferable that a channel constituting the field effect transistor contains the photosensitive electrical resistance lowering substance (claim 2).
Further, when the transistor is a bipolar transistor, it is preferable that the base and / or the collector constituting the bipolar transistor contain the photosensitive electrical resistance lowering substance (claim 3).
The photosensitive electrical resistance lowering substance is preferably a substance whose electrical resistance is reduced to 1/10 or less by light emitted from the light emitting element.
The photosensitive electrical resistance lowering substance is preferably a semiconductor.
The photosensitive electrical resistance reducing material is preferably a photoinduced metal-insulator transition material.
In this case, the photoinduced metal-insulator transition material is tetrathiafulvalene-tetrachlorobenzoquinone complex, Pr (1-x) Ca x MnO 3 , La (1-x) Sr x AlO 4 , La (1-x ) Ca X MnO 3 , La (1-x) Sr X MnO 3 , La (1-x) Ba X MnO 3 , Nd (1-x) Sr X MnO 3 , and Sr 2 MoFeO 6 (however, It is preferable that each X is independently at least one substance selected from 0 or more and 1 or less (Claim 7).

  According to the present invention, in a current-driven light-emitting device represented by an active matrix method using a transistor as a drive element, it is possible to improve the light-emitting efficiency with a simple configuration as compared with the conventional one.

  Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following description, and can be arbitrarily modified and implemented without departing from the gist of the present invention.

  As an embodiment of the present invention, a case where the present invention is applied to a basic unit of a light emitting device of a four-terminal TFT device will be described. FIG. 1 is a diagram schematically illustrating a configuration of a main part of a basic unit (hereinafter, referred to as “a light emitting unit of this embodiment”) 10 of a light emitting device according to an embodiment of the present invention. . Although FIG. 1 is a diagram used when explaining the conventional technique, the configuration of the main part of the light emission unit does not change even when the present invention is applied. To do. The light emitting unit 10 shown in FIG. 1 includes a light emitting element 20 that emits light by current and a driving circuit 30 for driving the light emitting element 20, and a driving transistor 40 is interposed in the driving circuit 30. The light emitting unit 10 is further provided with a switching transistor 50 and a storage capacitor 60. The light emission unit 10 is also equivalent to, for example, one pixel of a TFT device, like the conventional light emission unit 1, and usually a large number of the light emission units 10 are combined, and further, an optical filter, a power supply device, a housing, and an arithmetic circuit (not shown). The light emitting device of this embodiment such as a TFT device is configured by appropriately combining with the above.

  The light emitting element 20 is an element that emits light by current. Specifically, it refers to an element that converts part of the kinetic energy of carriers (electrons or holes) flowing into the element into electromagnetic waves, particularly visible light radiation energy. Although the kind in particular is not restrict | limited, As an example, inorganic EL element (inorganic electroluminescent EL element), inorganic LED (inorganic charge injection type EL element), organic LED (organic EL element) etc. are mentioned. For more specific structure and manufacturing method of the light emitting element, reference can be made to, for example, the descriptions of JP-A-01-245087, JP-A-08-293624, JP-A-09-148071.

  Arbitrary transistors are used as the driving transistor 40 and the switching transistor 50. Examples include FETs, bipolar transistors, and the like. Among these, FETs are preferable because only voltage is applied without passing current. The driving transistor 40 and the switching transistor 50 may be the same type of transistor (FET, bipolar transistor) or different types of transistors. For a more specific structure of the transistor and a manufacturing method thereof, for example, descriptions in JP-A-2004-103638 and JP-A-2004-95578 can be referred to.

  The materials constituting the light emitting element 20, the driving transistor 40, and the switching transistor 50 are preferably organic materials. For example, it is preferable that an organic LED is used as the light emitting element 20 and an organic transistor is used in combination as the driving transistor 40 and the switching transistor 50. By forming these components with an organic material, the light-emitting device can be made flexible, and the light-emitting device can be manufactured easily and at low cost.

  In the light emitting unit of the present embodiment, the current path of the driving transistor 40 interposed in the driving circuit 30 of the light emitting element 20 is a substance whose electric resistance is lowered by irradiation of light emitted from the light emitting element 20 (hereinafter referred to as “photosensitive” as appropriate). It is characterized by containing "electrical resistance lowering substance").

  Here, the “current path” of the transistor refers to a portion in the structure of the driving transistor 40 where a current (driving current) for driving the light emitting element 20 flows. When the driving transistor 40 is an FET, it is a channel, and when it is a bipolar transistor, it is a base and / or a collector.

Further, the photosensitive electrical resistance lowering substance specifically refers to a substance having an electrical resistivity change rate R defined by the following formula (I) of 1 or less.
R≡ (Electric resistivity when irradiated with light) / (Electric resistivity when not irradiated with light) (I)

In the formula (I), it is preferable to use a value measured by the following procedure for each electrical resistivity at the time of light irradiation and at the time of non-light irradiation.
Regarding the measurement environment, the influence of external light should be minimized as long as there is no hindrance to the measurement. For example, the measurement may be performed in a dark room or a box with a light shielding structure. The temperature of the sample should be as constant as possible as long as there is no problem in measurement.

  Under this environment, the electrical resistivity of the sample to be measured is measured by the 4-terminal method. Here, the sample may be in any state of single crystal, polycrystal, and amorphous. As the light to be irradiated, light emitted from a light emitting element used in the light emitting device of this embodiment or a light emitting element of the same type is used. The light emitting element is fixed at a certain distance from the sample. This distance is not limited, but it should be adjacent as long as it does not interfere with the measurement. Moreover, even when not making it adjoin, this distance is arrange | positioned within 5 cm. This is because if the distance is longer than 5 cm, the substance may not actually be observed even if the substance should be R ≦ 1. The intensity of the irradiated light is sufficiently large as long as there is no problem in the measurement. A substance that satisfies the requirement that R ≦ 1 in at least one of the conditions within the allowable range of the measurement conditions described above is defined as a photosensitive electrical resistance lowering substance.

In the light emitting unit 10 of the present embodiment, the photosensitive electrical resistance lowering substance contained in the current path of the driving transistor 40 is not particularly limited as long as R ≦ 1, but the smaller the value of R, the better. Specifically, R ≦ 1/10 is preferable, R ≦ 1/1000 is more preferable, and R ≦ 1/10 −6 is still more preferable. Although there is no restriction | limiting in particular regarding the minimum of R, Usually, it is R> = 1/10 <-24 >.

  In general, the photosensitive electrical resistance lowering substance used in the present embodiment is preferably a semiconductor. Here, that the photosensitive electrical resistance lowering substance is “semiconductor” means that it exhibits the properties of a semiconductor under light non-irradiation conditions. This is because a sufficient amount of output current flows when the semiconductor is used in the current path when the transistor is operated.

  In addition, the photosensitive electrical resistance lowering substance used in this embodiment is preferably a substance that causes a photo-induced metal-insulator transition. Here, the “substance causing a photoinduced metal-insulator transition” means that a band gap originally exists, that is, a semiconductor or an insulator, but the original electronic state when carriers are induced by light. Refers to a substance that changes to a band gap that decreases, preferably disappears. Whether such a phenomenon occurs when light is not irradiated can be confirmed by observing a change in the band gap by photoelectron spectroscopy, measurement of the temperature coefficient of electrical resistivity, measurement of an optical spectrum, or the like.

The photosensitive electrical resistance lowering substance is a substance that causes a photo-induced metal-insulator transition, and is more preferably a semiconductor when not irradiated with light, and most preferably an organic substance. Preferred examples of the substance that undergoes photoinduced metal-insulator transition and is a semiconductor include tetra-thiafulvalen (TTF) -tetrachloro-benzoquinone (CA) complex, Pr (1-x) Ca X MnO 3 , La ( 1-x) Sr X AlO 4 , La (1-x) Ca X MnO 3 , La (1-x) Sr X MnO 3 , La (1-x) Ba X MnO 3 , Nd (1-x) Sr X MnO 3 , Sr 2 MoFeO 6 and the like can be mentioned (wherein X independently represents a number of 0 or more and 1 or less). Any one of these may be used alone, or two or more may be used in any combination. These exemplary compounds may contain other elements as long as they do not affect the photoinduced metal-insulator transition.

  For substances that exhibit the metal-insulator transition phenomenon by light irradiation and their effects, see Physical Review Letters, 78, 22, 4257 (1997), Journal of the Physical Society of Japan, 66, 11, 3570 (1997). Etc. are described.

  Further, the light emitting unit 10 of the present embodiment is provided with means for controlling the temperature as necessary for the purpose of reducing the R of the photosensitive electrical resistance lowering substance, and is kept at a temperature higher or lower than the temperature of the external environment. You may do it. As means for controlling the temperature, a temperature control device such as a heater or a cryostat is generally provided.

  In the light emitting unit 10 of the present embodiment, these components are arranged so that photons generated from the light emitting element 20 are absorbed in the current path of the driving transistor 40. In particular, the light emitting element 20 and the driving transistor 40 are preferably in contact with each other, and the light emitting element 20 and the driving transistor 40 are more preferably integrated with each other in a multilayer structure. As photons are absorbed into the current path of the driving transistor 40, carrier scattering in the current path of the driving transistor 40 is reduced, that is, its electrical resistivity is reduced. As a result, the ratio of the power consumption in the driving transistor 40 per unit power consumption of the light emitting device is reduced, and the corresponding amount becomes the power consumption in the light emitting element 20, that is, contributes to the emission of photons.

  In a conventional light emitting device such as a TFT device, a part of photons emitted from a light emitting element is absorbed by a component such as a transistor disposed around the transistor and taken out as an effective photon to the outside of the light emitting device. There were no photons present. Such photon energy was dissipated as Joule heat. On the other hand, in the light emitting unit 10 of the present embodiment, the current path of the driving transistor 40 contains a photosensitive electrical resistance lowering substance, and absorbs the photons emitted from the light emitting element to increase its electrical resistivity. Therefore, the energy of photons that have been dissipated as Joule heat contributes to the reduction of electron scattering in the transistor, leading to an increase in photons from the light emitting element 20. As a result, when viewed from the same power consumption of the light-emitting device, the amount of photons taken out of the light-emitting device increases, that is, the light emission efficiency increases.

  The method for producing the light emitting unit 10 of the present embodiment is not particularly limited, but it is usually preferable to form a laminate by laminating the main constituent elements in layers.

  FIG. 2 is a cross-sectional view schematically showing an example of a laminated structure when the light emitting unit 10 of the present embodiment is configured as a laminated body. In FIG. 2, only main components included in the light emitting unit 10 of the present embodiment, that is, the light emitting element 20 and the driving transistor 40, and the substrate 90 on which these are stacked are shown, and other components (switching transistor 50) are shown. , Storage capacitor 60, etc.) are omitted.

  In the stacked structure shown in FIG. 2, the driving transistor 40 and the light emitting element 20 are stacked on the substrate 90 in this order. As the driving transistor 40, an example in which an FET is used is shown as an example. Specifically, the driving transistor 40 includes a gate electrode 41, a gate insulating layer 42, a source electrode 43, a drain electrode 44, and a photosensitive electrical resistance lowering layer 45. ing. Here, the photosensitive electrical resistance lowering layer 45 is a part mainly formed by using the above-described photosensitive electrical resistance lowering substance, and functions as a channel of the FET (that is, as a current path of the transistor). . The light emitting element 20 includes an electron transport layer 21, a light emitting layer 22, a hole transport layer 23, and a counter electrode 24. A part of the light generated from the light emitting layer 22 is absorbed by the photosensitive electrical resistance lowering layer 45, thereby reducing the carrier scattering of the photosensitive electrical resistance lowering portion 45.

  The light emitting unit 10 having the stacked structure shown in FIG. 2 can be manufactured by sequentially stacking the constituent elements of the light emitting element 20 and the driving transistor 40 on the substrate 90.

The material of the substrate 90 is not particularly limited. As long as the material has a certain degree of shape stability and does not affect the constituent elements of the light emitting unit 10 such as the light emitting element 20 and the driving transistor 40, it depends on the use of the light emitting unit 10 and the type of other constituent elements. It can be selected appropriately. Examples include plastics, SiO 2 , Si, etc. Among them, plastics are preferable from the viewpoints of price and handleability. Moreover, there is no restriction | limiting in particular also in the shape, According to the use of light emission units, such as plate shape, sheet shape, and film shape, it can select suitably. In particular, when a plastic film is used, a light-emitting device that is light and flexible and is not easily broken can be produced. The substrate may be a single layer or a plurality of layers. In the case of a plurality of layers, each layer may be formed of a different material.

  In some cases, the characteristics of the light emitting unit 10 obtained can be improved by performing a predetermined surface treatment on the substrate 90. For example, by adjusting the degree of hydrophilicity / hydrophobicity of the surface of the substrate 90, the film quality of the film formed thereon can be improved. In particular, the characteristics of organic semiconductor materials vary greatly depending on the state of the film, such as the orientation of molecules, but by applying surface treatment to the substrate 90, the molecular orientation at the interface between the substrate 90 and the semiconductor film is controlled, improving the characteristics. Is done. Examples of such substrate treatment include hydrophobization treatment with hexamethyldisilazane, cyclohexene, octadecyltrichlorosilane, acid treatment with hydrochloric acid, sulfuric acid, acetic acid, sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, etc. Alkali treatment, ozone treatment, fluorination treatment, plasma treatment with oxygen, argon, etc., Langmuir-Blodgett film formation treatment, other insulator and semiconductor thin film formation treatment, mechanical treatment, electrical treatment such as corona discharge Etc.

  In order to form each part of the light emitting unit 10 on the substrate 90, various methods are used. For example, vacuum processes such as PVD (Physical Vapor Deposition) method, CVD (Chemical Vapor Deposition) method, vacuum deposition method; coating methods such as casting, spin coating, dipping, blade coating, wire bar coating, spray coating; Langmuir-Blodgett method, in which the formed monomolecular film is transferred to the substrate and laminated, coating-like method in which liquid crystal or melt state is sandwiched between two substrates or introduced between the substrates by capillary action; inkjet printing, screen printing, offset Examples thereof include printing methods such as printing and letterpress printing; soft lithography methods such as microcontact printing; sol-gel methods and the like. A plurality of these methods may be combined.

A description of the vacuum process is added. For example, in the case of the vacuum deposition method, a material to be laminated is put in a crucible or a metal boat and heated in a vacuum, and this is evaporated to adhere to a substrate to be laminated. At this time, the gas pressure is usually 1 × 10 −3 Torr (1.3 × 10 −1 Pa) or less, preferably 1 × 10 −6 Torr (1.3 × 10 −4 Pa) or less. . In addition, since the characteristics of the semiconductor film and thus the device change depending on the substrate temperature, an optimum substrate temperature is selected. Specifically, a range of usually 0 ° C. or higher and 200 ° C. or lower is preferable. The deposition rate is usually 0.001 nm / s or more, preferably 0.01 nm / s or more, and usually 10 nm / s or less, preferably 1 nm / s or less.

  In the case of the PVD method, a solid material (target) is placed in a plasma together with a substrate to be laminated, and ions such as argon accelerated by the plasma collide with the target to strike the material atoms. put out. As a result, a material to be formed is deposited on the substrate or the like. The gas pressure at which discharge occurs varies depending on the target material, but is usually in the range of 0.1 Pa to 1 Pa.

  In the CVD method, substances that are raw materials of the materials to be laminated are reacted with each other in a vacuum space, and the material to be formed is deposited on a substrate to be laminated, as in the PVD method.

  Although the vacuum process requires expensive equipment, there is an advantage that a uniform film can be easily obtained with good film formation. On the other hand, the coating method and the printing method have an advantage that an inexpensive facility and a large-area layer can be formed at a time, and this method is preferably used particularly when the material is an organic material.

  It is possible to further improve the characteristics of each layer thus produced, particularly a layer made of an organic semiconductor such as the photosensitive electrical resistance lowering layer 45, by post-processing. For example, the heat treatment can reduce distortion in the film that is generated during film formation and can improve characteristics. Furthermore, characteristic changes due to oxidation or reduction can be induced by exposure to oxidizing or reducing gas or liquid such as oxygen or hydrogen. This is used for the purpose of increasing or decreasing the carrier density in the film, for example.

  Each layer of the light emitting unit 10 may be used by mixing a plurality of materials as necessary in order to improve characteristics or impart other characteristics, or each layer, for example, a photosensitive electrical resistance lowering layer, The light emitting layer or the like may be formed by being divided into a plurality of layers. Various additives may be added.

  The film thickness of each layer is not particularly limited, and can be appropriately selected according to the intended use and shape of the light emitting unit 10, the film forming method used, etc., but as long as it can perform the necessary functions. It is preferable to make it thin.

  In addition to the above-described layers, the light emitting unit 10 having a laminated structure can be provided with a protective layer as appropriate. When the protective layer is formed, there is an advantage that the influence of outside air such as humidity can be minimized, electrical characteristics can be stabilized, and deterioration with time can be prevented. The protective layer may be provided on each of the light emitting element 20 and the driving transistor 40, or may be provided in a form that covers the light emitting unit 10 that combines them and the entire light emitting device that is configured by combining them. Also good. The material of the protective layer is not particularly limited. For example, films made of various resins such as acrylic resin such as epoxy resin and polymethyl methacrylate, polyurethane, polyimide, polyvinyl alcohol, fluororesin, polyolefin, silicon oxide, aluminum oxide, and nitride A film made of a dielectric material such as silicon or an inorganic oxide film or a nitride film is preferable. Various known methods can be used for forming the protective layer. When the protective layer is made of a resin, for example, a method of applying a resin solution and then drying to form a resin film, or applying or depositing a resin monomer Examples include a method of polymerizing later. Moreover, you may perform a crosslinking process after film-forming. When the protective layer is made of an inorganic material, for example, a formation method in a vacuum process such as a sputtering method or a vapor deposition method, a formation method in a solution process typified by a sol-gel method, or the like can be used. In particular, it is preferable to use, as a material, a resin (polymer) having a low oxygen and moisture permeability and a low water absorption rate.

  In addition, the laminated structure of the light emitting unit 10 described above is an example, and the light emitting unit 10 can be appropriately modified as necessary as long as the function of the light emitting unit 10 is not impaired. Examples of such changes include changing the stacking order, providing another layer between any two layers, or reducing the number of layers by combining the functions of multiple layers. It is done.

  As described above, the light emitting unit 10 of the present embodiment described above is usually combined with a plurality of components and, if necessary, other components such as an optical filter, a power supply device, a housing, and an arithmetic circuit. Used in combination as a light emitting device. When the light emitting device is used as a display, it is preferable that the light emitting units 10 capable of emitting any one of three colors of blue, green, and red are appropriately combined. For this purpose, a light emitting element that emits blue, green, or red light may be used as the light emitting element 20 of each light emitting unit 10.

  As described above, the embodiment of the present invention has been described by taking the case where the present invention is applied to a light emitting unit of a four-terminal TFT device as an example. However, the embodiment of the present invention is not limited to the above-described embodiment. It is possible to carry out with appropriate modifications.

  For example, a photosensitive electrical resistance lowering substance may be included in the current path of the switching transistor 50 as well as the driving transistor 40. According to such a configuration, since the photons generated from the light emitting element 20 are absorbed also by the current path of the switching transistor 50, energy dissipation can be further suppressed.

  Further, the light emitting unit 10 shown in FIG. 1 has two transistors (a driving transistor 40 and a switching transistor 50) for one light emitting element 20, but one or one for each light emitting element. The present invention can also be applied to a light-emitting device having three or more transistors. If any of the transistors is interposed in the drive circuit that drives the light emitting element, the above-described structure is obtained by including a photosensitive electrical resistance lowering substance in the current path of the transistor interposed in the drive circuit. It is possible to obtain the effect of improving the luminous efficiency.

  Furthermore, the type of transistor is not particularly limited. In the above embodiment, the case where a field effect transistor (FET) is used has been described as an example. However, the present invention can be similarly applied to a bipolar transistor. A bipolar transistor is usually composed of an emitter, a base and a collector, and the collector current is controlled by turning on and off the base voltage. When the bipolar transistor is interposed in the drive circuit of the light emitting element, it is connected to the light emitting element via the collector terminal. In the bipolar transistor having such a configuration, it is preferable to include the above-described photosensitive electrical resistance reducing substance in the current path, specifically, the base and / or the collector. As a result, as in the case of the FET described above, it is possible to obtain the effect of improving the light emission efficiency of the light emitting element.

  The light emitting device to which the present invention can be applied is not limited to the above-described one. Any light-emitting device that includes a light-emitting element and a drive circuit that drives the light-emitting element and includes a transistor in the drive circuit can be applied to various types of light-emitting devices.

  The light-emitting device of the present invention has an effect that light-emitting efficiency of a current-driven light-emitting device using a transistor typified by an active matrix method as a drive element can be improved as compared with the conventional structure with a simple structure. Therefore, it can be suitably used in various fields in which such a light emitting device is used, for example, in the fields of inorganic LED display, organic LED (organic EL) display, inorganic EL display, liquid crystal display, and the like. .

The structure of the main part of the basic unit (light emitting unit) of the light emitting device according to one embodiment of the present invention and the basic unit (light emitting) of a four-terminal TFT device, which is an example of a conventional light emitting device using an active matrix method It is a figure which shows typically the structure of the principal part of a unit. It is sectional drawing which shows typically the example of the laminated structure in the case of comprising the light emission unit of this embodiment as a laminated body.

Explanation of symbols

1,10 Basic unit of light emitting device (light emitting unit)
2,20 Light Emitting Element 3,30 Drive Circuit 4,40 Driving Transistor 5,50 Switching Transistor 6,60 Storage Capacitor 21 Electron Transport Layer 22 Light Emitting Layer 23 Hole Transport Layer 24 Counter Electrode 41 Gate Electrode 42 Gate Insulating Film 43 Source electrode 44 Drain electrode 45 Photosensitive electric resistance lowering layer 90 Substrate

Claims (7)

  1. A light emitting device comprising a light emitting element and a drive circuit for driving the light emitting element,
    A transistor is interposed in the driving circuit, and the current path of the transistor contains a substance whose electric resistance is lowered by light emitted from the light emitting element (hereinafter referred to as “photosensitive electric resistance lowering substance”). A light emitting device.
  2. The transistor is a field effect transistor,
    2. The light emitting device according to claim 1, wherein a channel constituting the field effect transistor contains the photosensitive electrical resistance lowering substance.
  3. The transistor is a bipolar transistor,
    2. The light emitting device according to claim 1, wherein a base and / or a collector constituting the bipolar transistor contains the photosensitive electrical resistance lowering substance.
  4. The light emitting device according to any one of claims 1 to 3, wherein the photosensitive electrical resistance lowering substance is a substance whose electrical resistance is reduced to 1/10 or less by light emitted from the light emitting element. .
  5. The light emitting device according to claim 1, wherein the photosensitive electrical resistance lowering substance is a semiconductor.
  6. The light emitting device according to claim 1, wherein the photosensitive electrical resistance lowering material is a photoinduced metal-insulator transition material.
  7. The light-induced metal - insulator transition material, tetrathiafulvalene - tetrachlorobenzoquinone complex, Pr (1-x) Ca X MnO 3, La (1-x) Sr X AlO 4, La (1-x) Ca X A group consisting of MnO 3 , La (1-x) Sr X MnO 3 , La (1-x) Ba X MnO 3 , Nd (1-x) Sr X MnO 3 , and Sr 2 MoFeO 6 The light-emitting device according to claim 6, wherein the light-emitting device is at least one substance selected independently from 0 to 1 and a number of 1 or less.
JP2004178629A 2004-06-16 2004-06-16 Light emitting device Pending JP2006003552A (en)

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