JP2006049853A - Light emitting device, display, and lighting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device and lighting device constituted from field light emitting elements wherein, even if part of the field light emitting elements is short-circuited, there is no deterioration in light emission of the light emitting device and the entire lighting device and the light emission level is kept as it is. <P>SOLUTION: In this light emitting device and lighting device, two or more field light emitting elements formed on the same plane are connected in series. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an element (electroluminescent element) having a structure in which an anode, a cathode, and a thin film that emits light by passing an electric current between the anode and the cathode, and a light emitting device including the electroluminescent element on a substrate. Relates to the device.

  An electroluminescent element is an element that emits light by forming a thin film or a crystal containing an organic compound or an inorganic compound between a cathode and an anode and energizing between the negative and anode. In recent years, an electroluminescent element in which a thin film (hereinafter, referred to as an organic thin film) containing an organic compound as a main component (hereinafter referred to as an organic thin film) is installed between a cathode and an anode, that is, an electroluminescent element has been actively developed.

  As shown in FIG. 3, the electroluminescent device includes an organic thin film 103 disposed between a cathode 101 and an anode 102, and electrons are injected from the cathode 101 and holes are injected from the anode 102. And holes (both electrons and holes, or when referred to without distinguishing between them) are recombined. As a result, an excited state of organic molecules constituting the organic thin film is formed, and light emission is obtained when the excited state returns to the ground state by the radiation process.

  In the electroluminescent device, the organic thin film is formed as a thin film having a thickness of less than 1 μm. Moreover, since light emission can be obtained from the organic thin film itself, a backlight used in a liquid crystal display is not necessary. Therefore, it is a great feature that the electroluminescent element can be manufactured to be extremely thin and light.

  Also, the time from carrier injection to recombination is about 1 microsecond or less, and therefore the response speed is fast. Furthermore, since it is a carrier injection type electroluminescent device and is driven by a DC voltage, it has the merit that noise hardly occurs. By adopting an appropriate organic material or structure, it can be driven with a voltage of several volts, and application to a next-generation light-emitting device is expected.

  As applications of electroluminescent elements, displays and illumination are mainly expected. When considering the application of illumination, an incandescent bulb, which is a conventional lighting fixture, is a point light source, and a fluorescent lamp is a linear light source. On the other hand, since the electroluminescent element can give planar light emission, it is considered possible to produce an illuminating device having an unprecedented shape such as sheet-like illumination. In addition, the use of a surface light source makes it possible to easily obtain illumination closer to natural light.

  On the other hand, the greatest demerit of the electroluminescent device is low reliability due to deterioration of the device. Element degradation is roughly classified into two. One is a phenomenon in which the luminance gradually decreases with time. This is because when the electroluminescent element is driven with a constant current, the current efficiency gradually decreases due to deterioration of the material and the like, and as a result, the luminance gradually deteriorates. Another deterioration mode is a short circuit (conduction) between the cathode and the anode mainly due to a change in film quality. That is, a defect occurs in a part of the film due to crystallization of the material in the organic thin film, where the resistance between the cathode and the anode is greatly reduced, resulting in a partial short circuit. For this reason, carriers cannot be uniformly injected into the entire organic thin film, and light emission cannot be obtained as an element.

  The former deterioration can be improved by devising the structure of the organic material. In recent years, organic materials used for electroluminescent devices have made remarkable progress, and as a result, it has become possible to considerably suppress changes in luminance over time.

  On the other hand, the latter deterioration is often difficult to avoid simply by devising the structure of the organic material. From the viewpoint of material design, a method of preventing crystallization of the material can be considered. However, impurities contained in trace amounts in organic materials, compounds such as water impregnated from the outside of the device, or trace amounts of gas generated from the substrate are considered as one of the causes of short-circuiting between electrodes. Not only the purity, but also the substrate structure and the degree of cleaning are greatly affected. In addition, efforts must be made to prevent the contamination of impurities in the device manufacturing process to the maximum.

  In the case of using an electroluminescent element for a display, the electroluminescent element is formed on a passive matrix type or active matrix type substrate. In this case, basically, each element is driven independently. A conceptual diagram is shown in FIG. A first electrode 206 of an electroluminescent element is formed on a substrate 204, an organic thin film 208 is further formed thereon, and a second electrode 205 is stacked thereon. One of the first electrode 206 and the second electrode 205 is an anode, and the other is a cathode. In FIG. 2, the first electrode 206 is an anode and the second electrode 205 is a cathode.

  In the display, each pixel is formed in a very small area of about several hundred μm square, and these pixels are driven independently. Therefore, even if a certain device cannot emit light due to a short circuit, the light emission defect can be limited to a region of about several hundred μm, so that only a dot-like or linear defect occurs on the screen. Of course, display quality degradation as a display is unavoidable, but if the number of defects is small, it can function as a display.

However, when the electroluminescent device is used for illumination, the light emitting portion is a device having a relatively large area. Since the size of the element is equal to the size for emitting light as illumination, it has a very large area compared to the case where it is used in a display. Then, only the short area of the element is short-circuited, and the corresponding element does not emit light.

  FIG. 4 shows the structure of an electroluminescent element for illumination. In FIG. 4, reference numerals 701 and 702 denote electrodes of the electroluminescent element, one of which is an anode and the other is a cathode, and an organic thin film 703 is formed therebetween. When the very minute region 202 is short-circuited in the region 201 of the entire electroluminescent element, the electric field is concentrated on the minute region 202, and a current cannot be applied to the remaining majority. Accordingly, the entire region of the element, that is, the entire region 201 does not emit light, and even if there is no deterioration of the material used, the lifetime of the lighting fixture is reached.

  The present invention has been made in view of the above-described problems, and in a light-emitting device and a lighting device including an electroluminescent element, even if a part of the electroluminescent element is short-circuited, light emission of the light-emitting device or the entire lighting device is achieved. It is an object of the present invention to provide a light-emitting device and a lighting device that can maintain light emission without impairing light.

  One of the structures of the present invention for solving the above problem is a light emitting device characterized in that two or more electroluminescent elements formed on the same plane are connected in series.

One of the constitutions of the present invention for solving the above-mentioned problems is that a first electroluminescent element comprising a first anode, a first organic thin film and a first cathode, a second anode and a second organic A second electroluminescent element comprising a thin film and a second cathode, the side edges of the first anode and the second anode being covered by a partition, and a part of the first anode Is covered with the first organic thin film. A part of the second anode is covered with the second organic thin film. The first organic thin film is covered with the first cathode, and the second organic thin film is covered with the second cathode. The second cathode is electrically connected to the first anode via the partition, and a series connection structure of the first electroluminescent element and the second electroluminescent element is formed. The light emitting device is characterized.

One of the constitutions of the present invention for solving the above-mentioned problems is that a first electroluminescent element comprising a first anode, an organic thin film and a first cathode, a second anode, the organic thin film and a second A second electroluminescent element including a cathode. The first anode and the second anode are formed on the same plane, and the organic thin film is formed so as to cover a part of the first anode and the second anode. A first cathode is formed corresponding to the first anode and covering a part of the organic thin film, and a second cathode covering a part of the organic thin film and corresponding to the second anode. Is formed. In addition, the first cathode extends and is electrically connected at the end of the second anode where the organic thin film is not formed, and the first electroluminescent element and the second electroluminescent element are connected in series. A light-emitting device characterized in that a connection structure is formed.

One of the constitutions of the present invention for solving the above-mentioned problems is that a first electroluminescent element comprising a first anode, an organic thin film and a first cathode, a second anode, the organic thin film and a second A second electroluminescent element including a cathode. In addition, the first anode and the second anode are formed on the same plane, and side end portions of the first anode and the second anode are covered with a partition wall, and the first anode and the second anode are covered. The organic thin film is formed so as to cover a part of the two anodes. A first cathode is formed corresponding to the first anode and covering a part of the organic thin film, and a second cathode covering a part of the organic thin film and corresponding to the second anode. Is formed. The first cathode extends beyond the partition wall at the end of the second anode where the organic thin film is not formed, and is electrically connected to the second anode. The light emitting device is characterized in that an electroluminescent element and a second electroluminescent element are connected in series.

One of the constitutions of the present invention for solving the above-mentioned problems is that a first electroluminescent element comprising a first cathode, a first organic thin film and a first anode, a second cathode and a second organic A second electroluminescent element comprising a thin film and a second anode, wherein the first cathode and a side end portion of the second cathode are covered by a partition, and a part of the first cathode Is covered with the first organic thin film. A part of the second cathode is covered with the second organic thin film. The first organic thin film is covered with the first anode, and the second organic thin film is covered with the second anode. The second anode is electrically connected to the first cathode via the partition, and a series connection structure of the first electroluminescent element and the second electroluminescent element is formed. The light emitting device is characterized.

One of the constitutions of the present invention for solving the above-mentioned problems is that the first electroluminescent element comprising the first cathode, the organic thin film and the first anode, the second cathode, the organic thin film and the second A second electroluminescent element comprising an anode. The first cathode and the second cathode are formed on the same plane, and the organic thin film is formed so as to cover a part of the first cathode and the second cathode. A first anode is formed so as to cover a part of the organic thin film and correspond to the first cathode, and a second anode covers a part of the organic thin film and corresponds to the second cathode. Is formed. In addition, the first anode extends and is electrically connected at the end of the second cathode where the organic thin film is not formed, and the first electroluminescent element and the second electroluminescent element are connected in series. A light-emitting device characterized in that a connection structure is formed.

One of the constitutions of the present invention for solving the above-mentioned problems is that the first electroluminescent element comprising the first cathode, the organic thin film and the first anode, the second cathode, the organic thin film and the second A second electroluminescent element comprising an anode. The first cathode and the second cathode are formed on the same plane, and the side edges of the first cathode and the second cathode are covered with a partition wall, and the first cathode and the second cathode The organic thin film is formed so as to cover a part of the two cathodes. A first anode is formed so as to cover a part of the organic thin film and correspond to the first cathode, and a second anode covers a part of the organic thin film and corresponds to the second cathode. Is formed. The first anode extends beyond the partition at the end of the second cathode where the organic thin film is not formed, and is electrically connected to the second cathode. The light emitting device is characterized in that an electroluminescent element and a second electroluminescent element are connected in series.

The following effects can be obtained by the light-emitting device, display device, and illumination of the present invention as described above.

  In the electroluminescent element of the present invention, adjacent or adjacent elements are connected in series as shown in FIG. 1A, and the first electrodes 301A to 301C, The structure includes two electrodes 303A to 303C and organic thin films 302A to 302C sandwiched therebetween, and the first electrode and the second electrode of adjacent elements are electrically connected. One of the first electrode and the second electrode is an anode, and the other is a cathode.

  Here, when the negative anode is short-circuited in the region A, light emission can no longer be obtained in this region, but since the anode in the region A is electrically connected to the cathode in the region B, the region B and the region A current can be applied to C. Therefore, although light emission cannot be obtained in the region A, light emission can be obtained in the regions B and C, and light emission of the entire element can be maintained.

  For this reason, the electroluminescent element of the present invention can leave the light emitted from the element even when a part thereof is short-circuited. In addition, a light-emitting device having such an electroluminescent element does not suffer a great influence even when part of the light-emitting device is short-circuited, and can maintain the function as a light-emitting device. This also makes it possible to extend the usable period of the light emitting device. In addition, illumination using such an electroluminescent element or a light-emitting device can be used continuously as illumination even if a part of the electroluminescent element is short-circuited without significantly impairing the function as an illumination. . Thereby, the usable period of illumination becomes long and reliability can be improved.

On the other hand, in the conventional method, since the element structure as shown in FIG. 4 is adopted, if a short circuit occurs in the region A, the electric field is concentrated only in this short portion, and as a result, a current is applied to the regions B and C. Can not do it. Therefore, light emission cannot be obtained over the entire region of the element.

As described above, according to the present invention, even when a very small region of the element is short-circuited, light emission in other regions can be maintained, and the lifetime of the element can be extended.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different modes, and those skilled in the art can easily understand that the modes and details can be variously changed without departing from the spirit and scope of the present invention. Is done. Therefore, the present invention is not construed as being limited to the description of this embodiment mode.

(Embodiment 1)
Below, the form for achieving this invention is demonstrated using FIG. FIG. 5 shows an element structure composed of a single organic thin film and a negative anode, but the number of layers of the organic thin film is not limited.

  The light-emitting device of the present invention includes an island-shaped first electrode 502 formed over a substrate 501, an insulating film (partition wall) 510 covering a side end portion of the first electrode 502, and at least one of the first electrodes 502. A plurality of electroluminescent elements each including an organic thin film 503 that overlaps with the second electrode 504 and a second electrode 504 that partially overlaps at least the first electrode 502 on the organic thin film 503 are provided.

  One of the first electrode 502 and the second electrode 504 of the electroluminescent element is an anode, and the other is a cathode. In the present invention, the first electrode 502 is connected in series with the second electrode 506 included in the adjacent or adjacent electroluminescent element. Further, the connected electroluminescent element group may be a unit, and a plurality of units may be used as a light emitting device, or a light emitting device may be formed by one unit. Further, the number of electroluminescent elements connected for each unit may be the same or different.

  In this embodiment, the case where the first electrode 502 is an anode and the second electrode 504 is a cathode is described.

  First, since it is necessary to extract emitted light in an electroluminescent element, at least one of the electrodes needs to be transparent. In this embodiment, an electroluminescent element in which a first electrode 502 (anode) is formed using a transparent material over a substrate and light emission can be extracted from the anode side will be described. However, the present invention is not limited to this structure, and can be applied to, for example, a structure in which only the cathode is transparent and light is extracted from the cathode side, or a structure in which both the cathode anode and the cathode are transparent to obtain light emission from above and below the element. It is.

In FIG. 5, reference numeral 501 denotes a substrate for supporting an element, and not only quartz and glass but also paper or plastic resin can be used. In the embodiment of the present invention, since the transparent first electrode 502 (anode) is formed on the substrate, it is sufficient that the substrate has visible light transmittance. As the transparent anode, conductive metal oxides such as ITO (indium tin oxide) and IZO (indium zinc oxide) are suitable. These conductive metal oxide films are usually formed by sputtering, but may be formed by applying a sol-gel method or the like. In addition, a metal having a high work function such as gold can be used as a material other than the metal oxide. However, in this case, an ultrathin film is formed in consideration of light transmittance.

The feature of the present invention is that the first electrode 502 is formed in an island shape as shown in FIG. An organic thin film 503 is formed on the transparent electrode formed in an island shape. The organic thin film 503 is mainly formed using an organic compound, but may be formed using a single composition thin film. For example, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum (abbreviation: Almq ₃ ), bis (10-hydroxybenzo [h] -quinolinato) beryllium (abbreviation: BeBq) ₂ ), bis (2-methyl-8-quinolinolato)-(4-hydroxy-biphenylyl) -aluminum (abbreviation: BAlq), bis [2- (2-hydroxyphenyl) -benzoxazolate] zinc (abbreviation: Zn) (BOX) ₂ ), and bis [2- (2-hydroxyphenyl) -benzothiazolate] zinc (abbreviation: Zn (BTZ) ₂ ). Alternatively, hydrocarbon compounds such as 9,10-diphenylanthracene and 4,4′-bis (2,2-diphenylethenyl) biphenyl are also suitable.

The organic thin film may be a mixed layer of a plurality of materials. Luminous efficiency can be increased by mixing a small amount of a fluorescent dye or a phosphorescent dye in the organic thin film. Examples of the fluorescent material include coumarin derivatives, quinacridone derivatives, acridone derivatives, pyrene derivatives, perylene derivatives, anthracene derivatives, and pyrone derivatives. As the phosphorescent dye, the triplet light-emitting material includes tris (2-phenylpyridine) iridium (hereinafter referred to as “Ir (ppy) ₃ ”), 2,3,7,8,12,13,17,18. -Transition metal complexes such as Ir, Ru, Rh, Pt, or rare earth metals such as octaethyl-21H, 23H-porphyrin-platinum (hereinafter referred to as “PtOEP”).

The organic thin film having a single composition or the mixed organic thin film described above is a functional layer for obtaining light emission, and is called a light emitting layer. That is, it is an element in which an organic thin film composed only of a light emitting layer is disposed between negative and positive electrodes. However, the organic thin film may be a film having a laminated structure in which not only the light emitting layer but also layers having other functions are combined. This is because it is difficult to control the injection balance of electrons and holes with only the above-mentioned single composition or mixed light emitting layer, and by improving the luminous efficiency by laminating a plurality of materials to improve this. This is because of the improvement. For example, in addition to the light-emitting layer having the single composition or the mixed composition described above, a hole transport layer that efficiently transports injected holes to the light-emitting layer, and an electron transport layer that efficiently transports injected electrons to the light-emitting layer It is good to provide. A material suitable for the hole transport layer is an aromatic amine-based compound (that is, a compound having a benzene ring-nitrogen bond). As a widely used material, 4,4′-bis [N- (3-methylphenyl) -N-phenyl-amino] -biphenyl and its derivative 4,4′-bis [N- (1-naphthyl) ) -N-phenyl-amino] -biphenyl, 4,4 ′, 4 ″ -tris (N, N-diphenyl-amino) -triphenylamine, 4,4 ′, 4 ″ -tris [N- (3 And starburst aromatic amine compounds such as -methylphenyl) -N-phenyl-amino] -triphenylamine. Examples of suitable materials for the electron transport layer include the above-mentioned typical metal compounds, but 3- (4-tert-butylphenyl) -4- (4-ethylphenyl) -5- (4-biphenylyl) -1 Triazole derivatives such as 2,2,4-triazole, and phenanthroline derivatives such as bathophenanthroline and bathocuproin may be used.

The method for forming these organic thin films is not limited to the vacuum deposition method, and any so-called wet method may be employed for the spin coating method, the dip coating method, and the spray method.

Furthermore, a hole injection layer for reducing a hole injection barrier from the anode is preferably provided between the hole transport layer and the anode described above. Suitable compounds for the hole injection layer include transition metal oxides such as cobalt oxide, titanium oxide, niobium oxide, nickel oxide, neodymium oxide, vanadium oxide, beryllium aluminum oxide, molybdenum oxide, lanthanum oxide, ruthenium oxide, and rhenium oxide. Etc. Preferably, it is a transition metal oxide of Group 4 to Group 7, and nitrides and halides may be used. Alternatively, 4,4 ′, 4 ″ -tris [3-methylphenyl (phenyl) amino] triphenylamine (hereinafter referred to as m-MTDATA) or 4,4′-bis [N- (4- (N , N-di-m-tolylamino) phenyl) -N-phenylamino] biphenyl (hereinafter referred to as DNTPD) or the like, or a low molecular organic compound such as metal phthalocyanine is also a good example. Organic polymer compounds can also be used, and examples thereof include polyaniline and poly (2,3-ethylenedioxythiophene).

Similarly, an electron injection layer for reducing an electron injection barrier from the cathode is preferably provided between the electron transport layer and the cathode. As a compound suitable for the electron injection layer, an alkali metal salt such as calcium fluoride, lithium fluoride, lithium oxide or lithium chloride, an alkaline earth metal salt, or the like may be used.

In this manner, the organic thin film 503 is formed, and then the second electrode 504 (cathode) is formed. As the second electrode 504 (cathode), a metal having a low work function and a metal compound thereof can be given. For example, Mg—Ag alloy, Al—Li alloy, Mg—Li alloy and the like. However, when an electron injection layer is used, since an electron injection barrier is reduced, Al which is a metal having a large work function may be used.

At this time, it is a feature of the present invention that the second electrode 504 (cathode) is formed in an island shape so as to face the anode and similarly to the first electrode 502 (anode). Furthermore, as shown by the dotted line in FIG. 5, one anode is characterized in that it is electrically connected to an adjacent or adjacent cathode. That is, a plurality of electroluminescent elements are formed on the same plane, and a plurality of electroluminescent elements are electrically arranged in series. In FIG. 5, each of the three electroluminescent elements is electrically arranged in series, but the number of electroluminescent elements arranged in series is not limited and may be an integer of 2 or more. However, since they are arranged in series, the driving voltage of the device is in principle the sum of the driving voltages of the individual electroluminescent elements. Therefore, in consideration of the driving voltage, it is preferably 2 or more and 20 or less.

  In addition, the connected electroluminescent element may be used as one unit, and a plurality of units may be used as the light emitting device, or the light emitting device may be formed as one unit. Further, the number of electroluminescent elements connected for each unit may be the same or different.

Here, in FIG. 5, even if the region 505 surrounded by the thick line portion is short-circuited, a current can be applied to the electrically connected element portions. Therefore, light emission cannot be obtained from the region 505, but light emission can be obtained from elements in other regions. If the proportion of the area A is sufficiently small with respect to the light emitting surface, almost the entire element can be obtained. The light emission is maintained from.

  For this reason, the electroluminescent element of the present invention can leave light emitted from another element even if one electroluminescent element is short-circuited, and can extend the life of the element.

  In the present embodiment, the organic thin film can be composed of a single layer or a plurality of organic thin films. Further, as shown in FIG. 6, a conductive intermediate layer (hereinafter referred to as an intermediate conductive layer) is included in the organic thin film. ) May be installed. Also in FIG. 6, the first electrode 502 is an anode and the second electrode 504 is a cathode, but this may be either.

  That is, the organic thin film 508 is formed on the first electrode 502 (anode) formed on the substrate 501. The organic thin film 508 may be a single layer, or may have a stacked structure by combining an electron / hole transport layer for transporting carriers, a light emitting layer, and the like. An intermediate conductive layer 507 is formed on the organic thin film 508 thus formed. Further, an organic thin film 506 is formed on the intermediate conductive layer 507, and finally a second electrode 504 (cathode) is formed. The organic thin film 506 at this time can also be composed of a single layer or a plurality of organic thin films. The organic thin films 508 and 506 may have the same structure and composition, or may have different structures and compositions. Furthermore, the emission spectra obtained from the organic thin films 508 and 506 may be the same or different.

  In the device manufactured in this way, electrons are transferred from the second electrode (cathode) 504 to the organic thin film 506 and current is transferred from the first electrode (anode) 502 to the organic thin film 508 by energizing the negative and positive electrodes. Are injected from the intermediate conductive layer 507 into the organic thin film 508, and holes are injected from the intermediate conductive layer 507 into the organic thin film 506. Accordingly, recombination of carriers occurs not only in the organic thin film 508 but also in the organic thin film 506, and light emission can be obtained from both thin films. At this time, if the organic thin films 508 and 506 have complementary colors, white light emission can be obtained. When the intermediate conductive layer is provided, each element has two elements stacked in series, so that the driving voltage of each element almost doubles. However, by applying the same current density, almost double emission intensity can be obtained.

  It is essential that the intermediate conductive layer has transparency, and that carriers can be injected into the organic thin films placed above and below the intermediate conductive layer. Specific materials include: 1) a mixed layer composed of an electron transporting compound such as Alq or bathocuproine (hereinafter referred to as BCP) and an electron injecting compound such as an alkali metal; ITO (indium tin oxide) or IZO; Lamination of transparent electro-transparent electrodes such as (indium / zinc oxide), 2) Lamination of mixed layer of metal transporting compound and electron injection compound and metal oxide, 3) Electron transporting compound and electron injection property Examples thereof include a mixed layer made of a compound and a laminate of an electron-accepting organic compound.

In the present embodiment, only one intermediate conductive layer is used and two organic thin films are used. However, the number of intermediate conductive layers is not limited, and the number of organic thin films is 1 from the number of intermediate conductive layers. More layers are needed.

(Embodiment 2)
In this embodiment mode, a method for manufacturing the light-emitting device of the present invention with a layout different from that in Embodiment Mode 1 will be described with reference to FIGS. 12 and 13 show an example of one unit in which two electroluminescent elements are connected in series. Of course, three or more electroluminescent elements may be connected in series. In addition, the light emitting device may be configured by one unit, or may be configured by a plurality of units. The component materials and the like are omitted when described in the first embodiment.

  First, the first electrode 603 is provided in an island shape over the substrate 601 (FIG. 12A). The first electrode 603 needs to be transparent when light is extracted in the direction of the substrate 601, but may be opaque when light is extracted in the direction opposite to the substrate 601 with respect to the first electrode 603. Absent. The first electrode 603 functions as an anode or a cathode of the electroluminescent element. In the case where the first electrode 603 is used as an anode, a material such as aluminum having a high work function is preferably used. Examples of the material that can be used as the anode and have transparency include the metal oxides described in Embodiment 1. Even if it is an opaque material such as gold or aluminum, sufficient transparency can be obtained by making it an extremely thin film.

  In the case where the first electrode 603 is used as a cathode, a material having a low work function can be used. For example, Mg—Ag alloy, Al—Li alloy, Mg—Li alloy and the like. However, when an electron injection layer is used, since an electron injection barrier is reduced, Al which is a metal having a large work function may be used. Moreover, although these cathode materials are opaque, sufficient transparency can be obtained by using an ultrathin film in order to obtain transparency.

  Subsequently, an insulating film (partition wall) 609 is formed so as to cover the substrate 601 and the first electrode 603. An opening is provided in the insulating film (partition wall) 609 so that the first electrode 603 is exposed in the contact hole 610 and the element formation portion 611 (FIG. 12B).

  Next, an organic thin film 604 is formed to cover the opening formed in the element formation portion 611 (FIG. 13C). Subsequently, the second electrode 605 is also formed so as to cover at least part of the opening formed in the element formation portion 611, whereby an electroluminescent element is formed (FIG. 13D). Note that the second electrode 605 of the first electroluminescent element 612 is formed so as to be electrically connected to the first electrode 603 of the second electroluminescent element 613. In this embodiment mode, the connection is made through a contact hole provided in the insulating film (partition wall) 609; however, the connection method is not limited to this.

  In addition, the first electrode of the first electroluminescent element 612 and the second electrode of the second electroluminescent element 613 are formed to extend to the external connection portion 607 and are connected to an external power source. The number of electrodes directly connected to the external connection portion is one each of the first electrode 603 and the second electrode 605, and one of the end elements of the series-connected elements is the first electrode 603. Is connected directly to the external connection portion, the second electrode 605 is directly connected to the other terminal element at the external connection portion.

  In the light emitting device of the present invention formed as described above, even if some of the electroluminescent elements are short-circuited, a current can be applied to other electrically connected electroluminescent element portions. Therefore, light emission cannot be obtained from the short-circuited portion, but light emission can be obtained from the other electroluminescent element elements, and the short circuit occurring in one place does not have a great influence.

(Embodiment 3)
In the present embodiment, another embodiment of the present invention will be described with reference to FIG. Note that the arrangement method of the electroluminescent element shown in the figure is the same as that described in the second embodiment, but of course, the arrangement shown in the first embodiment may be used as long as it has the configuration of the present invention. Any arrangement method may be used.

  The light-emitting device of the present invention as shown in Embodiment Mode 1 and Embodiment Mode 2 includes a plurality of the above-described electroluminescences including a first electrode 603, a second electrode 605, and an organic thin film 604 sandwiched therebetween. The device includes a substrate 601 provided with an external connection portion 607 for connecting the element, the electroluminescent element, an external circuit, and a power source, and a sealing member 602. Note that a circuit having some function in addition to the above may be provided on the substrate (FIG. 11).

  Since degradation of the electroluminescent element is promoted by water or the like, sealing is performed for the purpose of protecting it from a substance that promotes the electroluminescent element formed on the substrate. Sealing is performed using a counter substrate similar to the substrate, a sealing can, a sealing film, or the like. However, when the counter substrate is used for sealing, the external connection portion is exposed by the insulating sealing material 608. to paste together.

  A space between the counter substrate and the element substrate may be filled with an inert gas such as dry nitrogen, or a seal material may be applied to the entire surface of the pixel portion to form the counter substrate. It is preferable to use an ultraviolet curable resin or the like for the sealing material. The sealing material may contain a desiccant and particles for keeping the gap constant. Subsequently, a flexible wiring substrate is attached to the external connection portion, whereby the light emitting device is completed.

  FIG. 11 shows an example of a method of connecting electroluminescent elements in series. The second electrode 605 of the electroluminescent element is connected to the first electrode 603 of the adjacent electroluminescent element through a contact hole 606 opened in the partition wall 609. Although FIG. 11 shows an example in which the stripes are arranged in a stripe shape, it is of course possible to use a matrix shape, and the selection thereof can be appropriately determined by the user as a design matter. For simplicity, each electroluminescent element is very large with respect to the substrate. However, if the area ratio of one electroluminescent element with respect to the substrate is reduced, one electroluminescent element is caused by a short circuit. There will be no significant effect if the light stops. Of course, the method of connecting elements is not limited to this, and can be set by the user as appropriate. In FIG. 11, the connection unit of the electroluminescent element is one unit, but a plurality of units of two or more units may be used.

  The light-emitting device of the present invention does not suffer a great influence because the light emission of other electroluminescent elements is maintained even if a short circuit occurs in a part of the mounted electroluminescent element, and functions as a light-emitting device. Can be maintained. In addition, this makes it possible to extend the usable period of the light-emitting device and extend its life.

(Embodiment 4)
In this embodiment, an example of a device using the light-emitting device of the present invention will be described with reference to FIGS.

  FIG. 7 shows an example of the liquid crystal display device of the present invention. The liquid crystal display device illustrated in FIG. 7 includes a housing 901, a liquid crystal layer 902, a backlight 903, and a housing 904, and the liquid crystal layer 902 is connected to a driver IC 905. The backlight 903 uses the light-emitting device having the structure described in Embodiment 1, and current is supplied from the terminal 906.

  Since the liquid crystal display device of the present invention uses the light-emitting device having the structure described in Embodiment Mode 1 as a backlight, a thin and light liquid crystal display device can be obtained. Further, even a thin and light liquid crystal display device can be a highly reliable display device. In other words, in the lighting device used for the backlight 903, light emission in other regions can be maintained even if an extremely small region of the element is short-circuited.

  In addition, since the backlight can have a large area, the liquid crystal display device can have a large area. Further, since the electroluminescent element is thin and has low power consumption, it is possible to reduce the thickness and power consumption of the display device.

  FIG. 8A shows the lighting device of the present invention used as indoor lighting. The illuminating device of the present invention can maintain light emission in other regions even if a short circuit of a very small region of the element occurs, and can be a illuminating device having a long usable period. Since this is a surface emitting lighting device and there is little variation in luminance even when the area is increased, for example, the lighting device of the present invention can be used on the entire ceiling surface. Further, the lighting device of the present invention can be used not only on the ceiling but also on walls, floors, pillars, and the like. Further, by manufacturing the light-emitting device of the present invention using a flexible substrate, a thin and flexible lighting device can be obtained. Therefore, it can be installed on a curved surface. Further, it can be used not only indoors but also outdoors, and can be installed on a building wall or the like as an external light.

  FIG. 8B shows the lighting device of the present invention used as lighting in a tunnel. The illuminating device of the present invention can maintain light emission in other regions even if a short circuit of a very small region of the element occurs, and can be a illuminating device having a long usable period. In addition, when the light-emitting device of the present invention is manufactured using a flexible substrate, a thin and flexible lighting device can be obtained. Therefore, it can be installed along the curved surface of the wall in the tunnel.

  FIG. 8C illustrates an example in which the lighting device of the present invention is used as interior lighting. The illuminating device of the present invention can maintain light emission in other regions even when an extremely small region of the element is short-circuited, and can be a illuminating device having a long usable period. In addition, when the light-emitting device of the present invention is manufactured using a flexible substrate, a thin and flexible lighting device can be obtained. In addition, since the light-emitting device of the present invention is surface-emitting, it can be processed into a free shape as shown in FIG.

  The lighting device of the present invention can also be used as lighting when taking a photograph. When taking a picture, it is possible to take a picture similar to the case where the subject is illuminated with natural light by illuminating the subject with light having a uniform luminance with a large area.

(Embodiment 5)
A light-emitting device capable of illuminating at a constant luminance regardless of the variation factor in consideration of the temperature characteristics and luminance change characteristics of the electroluminescence element will be described with reference to FIGS.

  In the light-emitting device shown in FIGS. 9 and 10, the electroluminescent element 404 has the same structure as that of the first embodiment. In addition to the electroluminescent element 404, a monitor element 403 is disposed. One or a plurality of monitor elements 403 can be provided. The monitor element 403 may be provided adjacent to the electroluminescent element 404 or may be provided on another part of the substrate on which the electroluminescent element 404 is formed.

  It is desirable that the monitor element 403 and the electroluminescent element 404 are manufactured in the same manufacturing process. That is, the structure of the element is the same as the constituent material. By making the electroluminescent element 404 and the monitor element 403 the same, temperature characteristics and deterioration characteristics can be made similar. As a result, it is possible to improve the accuracy of correction with respect to the luminance variation of the electroluminescent element 404. The structures of the electroluminescent element 404 and the monitor element 403 are the same as those in the first embodiment, and two or more electroluminescent elements formed on the same plane are connected in series with the adjacent or adjacent electroluminescent elements. This is the structure. However, the monitor element 403 may have a typical laminated structure in which an organic thin film is sandwiched between a pair of electrodes without complicating the electrode structure.

  The monitor element 403 is connected to the current source 401. One terminal of the monitor element 403 connected to the current source 401 is also connected to the input side of the voltage generation circuit 402. The output side of the voltage generation circuit 402 is connected to the electroluminescent element 404.

  The current source 401 supplies a constant current to the monitor element 403. When the environmental temperature changes while the monitor element 403 is driven at a constant current, the resistance value changes. When the resistance value of the monitor element 403 changes, the current value flowing through the monitor element 403 is constant, so that the potential difference between both electrodes of the monitor element 403 changes. By detecting the potential difference of the monitor element 403 at this time, it is possible to detect a change in the environmental temperature. In the monitor element 403, the other electrode potential not connected to the current source 401 is constant. Therefore, it is possible to detect a change in electrode potential on the side connected to the current source 401 of the monitor element 403.

  Also, the resistance value of the monitor element 403 changes when the light emission characteristics of the monitor element 403 driven by constant current change with time. Similarly in this case, the change in the light emission characteristics can be known by detecting the potential difference of the monitor element 403. That is, the degree of deterioration of the light emission luminance can be detected.

  The voltage generation circuit 402 uses one electrode potential of the monitor element 403 as an input potential. The potential output from the voltage generation circuit 402 is the same as the potential detected by the monitor element 403. With this voltage generation circuit 402, one electrode potential of the monitor element 403 can be reflected in the drive voltage of the electroluminescent element 404.

  As shown in the inset of FIG. 9, the voltage generation circuit 402 can be configured by a voltage follower circuit using an operational amplifier. Since the non-inverting input terminal of the voltage follower circuit has a high input impedance and the output terminal has a low output impedance, the input side and the output side are output as the same potential, and the current of the current source 401 is output without flowing into the voltage follower circuit. Current can flow from the terminal. Note that other circuit configurations can be applied as long as the circuit can prevent potential fluctuations, such as the voltage follower circuit illustrated here.

  In the light emitting device, a current source 401, a monitor element 403, and a voltage generation circuit 402 constitute a temperature and deterioration compensation circuit (hereinafter referred to as a compensation circuit). That is, the ratio of the total amount of charge flowing in the electroluminescent element provided in the light emitting unit and the monitor element is operated under different driving conditions for both the electroluminescent element provided in the light emitting part and the monitor element equivalent to the electroluminescent element. However, control is performed so as to satisfy a certain relationship in consideration of luminance degradation.

  The light-emitting device of this embodiment compares the amount of electric charge of the electroluminescent element 404 with the amount of electric charge flowing to the monitor element 403 by considering essential deterioration that occurs in the electroluminescent element. Correction is made so that the brightness is constant. Thereby, constant luminescence driving can be performed to keep the luminance of the electroluminescent element 404 constant. For example, the driving condition of the monitor element 403 is set to be more overloaded than the driving condition of the electroluminescent element 404, and the constant luminescence driving is realized by controlling the luminance so as to keep it constant.

  An example of a light-emitting device capable of illuminating at a constant luminance regardless of the variation factor in consideration of the temperature characteristics and luminance change characteristics of the electroluminescent element will be described with reference to FIG.

  The light-emitting device shown in FIG. 10 includes a monitor element 403 and an electroluminescent element 404. The monitor element 403 is driven with a constant current by a current source 401. The constant voltage source 405 has a function of generating a constant voltage, and a constant voltage source having a small temperature coefficient such as a known band gap regulator is used. The voltage generated from the constant voltage source 405 is converted into a constant current having a small temperature coefficient by the operational amplifier 406, the transistor 407, and the resistor 408. The converted current is inverted by a current mirror circuit including transistors 409 and 410 and resistors 411 and 412 and supplied to the electroluminescent element 404. The voltage of the constant voltage source 405 is controlled according to the output of the voltage generation circuit 402 that detects the potential difference of the monitor element 403. In this case, when the output voltage of the voltage generation circuit 402 is increased, the output voltage of the constant voltage source 405 is also increased and the amount of current flowing through the electroluminescence element 404 is increased.

  The light-emitting device of FIG. 10 uses the monitor element 403 to correct the voltage generated from the constant voltage source 405 according to the temperature change and the change with time, so that the influence due to both the temperature change and the change with time is affected. Can be prevented.

  As described above, when the light emitting device, the display device, and the illumination described in Embodiments 1 and 2 are combined with a unit that corrects the luminance of the electroluminescent element in accordance with a change in temperature and a change with time, a decrease in illuminance is achieved. It is possible to prevent the burden on the eyes due to the lighting, and to always provide illumination with optimum brightness.

The figure which shows the structure of the light-emitting device of this invention, and a circuit diagram Diagram showing the structure of a general light-emitting device Diagram showing the structure of a general light-emitting device Structure of electroluminescent device with large pixel area and schematic diagram when short circuit occurs The figure which shows the structure of the light-emitting device of this invention, and a schematic diagram when a short circuit arises The figure which shows the structure of the element which is the light-emitting device of this invention, and the intermediate conductive layer was installed. The figure showing the usage pattern of the illuminating device of this invention. The figure which illustrates the usage type of the illuminating device of this invention. The figure of the circuit which can compensate for the temperature change of luminance, and a time-dependent change. The figure of the circuit which can compensate for the temperature change of luminance, and a time-dependent change. The top view of the light-emitting device of this invention. The figure showing the creation process of the light-emitting device of this invention. The figure showing the creation process of the light-emitting device of this invention.

Explanation of symbols

101 Cathode 102 Anode 103 Organic thin film

Claims (12)

A light-emitting device, wherein two or more electroluminescent elements formed on the same plane are connected in series. A first electroluminescent device comprising a first anode, a first organic thin film, and a first cathode;
A second electroluminescent element comprising a second anode, a second organic thin film, and a second cathode;
Side edges of the first anode and the second anode are covered with partition walls,
A portion of the first anode is covered with the first organic thin film;
A portion of the second anode is covered with the second organic thin film;
The first organic thin film is covered with the first cathode;
The second organic thin film is covered with the second cathode;
The second cathode is electrically connected to the first anode via the partition;
A light-emitting device, wherein a series connection structure of the first electroluminescent element and the second electroluminescent element is formed. A first electroluminescent element comprising a first anode, an organic thin film, and a first cathode;
A second electroluminescent element comprising a second anode, the organic thin film, and a second cathode;
The first anode and the second anode are formed on the same plane;
The organic thin film is formed to cover a part of the first anode and the second anode,
A first cathode covering a part of the organic thin film and corresponding to the first anode;
A second cathode covering a part of the organic thin film and corresponding to the second anode;
The first cathode extends and is electrically connected at the end of the second anode where the organic thin film is not formed,
A light emitting device characterized in that a series connection structure of the first electroluminescent element and the second electroluminescent element is formed. A first electroluminescent element comprising a first anode, an organic thin film, and a first cathode;
A second electroluminescent element comprising a second anode, the organic thin film, and a second cathode;
The first anode and the second anode are formed on the same plane;
Side edges of the first anode and the second anode are covered with partition walls,
The organic thin film is formed to cover a part of the first anode and the second anode,
A first cathode covering a part of the organic thin film and corresponding to the first anode;
A second cathode covering a part of the organic thin film and corresponding to the second anode;
The first cathode extends beyond the partition at the end of the second anode where the organic thin film is not formed, and is electrically connected to the second anode;
A light emitting device characterized in that a series connection structure of the first electroluminescent element and the second electroluminescent element is formed. A first electroluminescent device comprising a first cathode, a first organic thin film, and a first anode;
A second electroluminescent device comprising a second cathode, a second organic thin film, and a second anode;
Side edges of the first cathode and the second cathode are covered with a partition wall,
A portion of the first cathode is covered by the first organic thin film;
A portion of the second cathode is covered with the second organic thin film;
The first organic thin film is covered with the first anode;
The second organic thin film is covered with the second anode;
The second anode is electrically connected to the first cathode via the partition;
A light-emitting device, wherein a series connection structure of the first electroluminescent element and the second electroluminescent element is formed. A first electroluminescent device comprising a first cathode, an organic thin film, and a first anode;
A second electroluminescent element comprising a second cathode, the organic thin film, and a second anode;
A first cathode and a second cathode are formed on the same plane;
The organic thin film is formed to cover a part of the first cathode and the second cathode,
A first anode covering a part of the organic thin film and corresponding to the first cathode;
Covering a part of the organic thin film and forming a second anode corresponding to the second cathode;
The first anode extends and is electrically connected at the end of the second cathode where the organic thin film is not formed,
A light-emitting device, wherein a series connection structure of the first electroluminescent element and the second electroluminescent element is formed. A first electroluminescent device comprising a first cathode, an organic thin film, and a first anode;
A second electroluminescent element comprising a second cathode, the organic thin film, and a second anode;
A first cathode and a second cathode are formed on the same plane;
Side edges of the first cathode and the second cathode are covered with a partition wall,
The organic thin film is formed to cover a part of the first cathode and the second cathode,
A first anode covering a part of the organic thin film and corresponding to the first cathode;
Covering a part of the organic thin film and forming a second anode corresponding to the second cathode;
The first anode extends beyond the partition at the end of the second cathode where the organic thin film is not formed, and is electrically connected to the second cathode;
A light-emitting device, wherein a series connection structure of the first electroluminescent element and the second electroluminescent element is formed. 8. The light-emitting device according to claim 2, wherein a plurality of the series connection structures are further provided in series. 9. The light emitting device according to claim 8, wherein the number of electroluminescent elements connected in series by the series connection structure is 2 to 20. 10. The light emitting device according to claim 1, wherein the electroluminescent element group connected by the series connection structure is one unit, and the unit is composed of one unit of the electroluminescent element group. 10. The light-emitting device according to claim 1, wherein the electroluminescent element group connected by the series connection structure is a unit, and the electroluminescent element group includes a plurality of units of the electroluminescent element group. An illuminating device using the light emitting device according to any one of claims 1 to 11.

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