JP6055054B1 - Light emitting device and manufacturing method thereof - Google Patents

Abstract

A light-emitting device with high efficiency and long life is provided at low cost and in large quantities. One of them is a substantially transparent anode and cathode, and a p-side and n arranged between the anode and cathode. A light emitting device comprising an LED die having a side and an organic layer comprising an organic semiconductor material disposed between the anode and the cathode and in contact with the LED die, wherein the LED die has a cathode side on the n side and an anode side on the p side The organic layer is arranged to fill at least one of the n side and the cathode or the p side and the anode in the cross section where the LED die exists, and there is no LED die. In the cross section, it is arranged so as to fill between the cathode and the anode, and is continuously arranged over the portion where the LED die is present and the portion where the LED die is not present, Thicker than the thickness of the organic layer thickness of the cross-section LED die is present, the light emitting device which is a predetermined film thickness range. [Selection] Figure 1

Description

  The present invention relates to a light emitting device and a manufacturing method thereof.

  An LED is a light-emitting device that has advantages such as power saving and a long life, and is widely used industrially as a backlight for illumination and a display. The LED is manufactured by growing a light-emitting thin film on a small crystalline substrate such as sapphire. An LED device fabricated in a planar shape on a substrate is divided into small pieces (hereinafter referred to as LED dies) each having an order of 100 micrometers. One or several LED dies are fixed to terminals that can be connected to an external power supply (hereinafter referred to as mounting), and become a practical light emitting device that emits light by applying a voltage.

  There are several problems with the process of mounting the aforementioned LED die and the resulting light emitting device.

  First, since it is necessary to pick up each die cut from the wafer, move it to a desired position such as a terminal portion, and fix it, the manufacturing cost is high.

  Secondly, when the electrodes and terminals of the LED die are connected by wire bonding technology at the time of mounting, there is a loss of light because the wire and the wire fixing part shield light. Also, the manufacturing cost for performing wire bonding is expensive.

  Third, the LED die is driven at a high current density in order to obtain the desired brightness and illuminance from the LED die having a small number and a small area. For this reason, the deterioration of the light emission efficiency and the device deterioration due to the device temperature increase become problems. When used for illumination, when the light source is viewed directly, the result is very dazzling or glare.

  Solutions for these three problems have been disclosed so far.

  Patent Document 1 discloses replacing an opaque wire with a transparent electrode. This contributes to the solution of the second problem.

  Patent Document 2 is a further development of Patent Document 1, and discloses a structure and manufacturing method of a light emitting device in which a large number of LED dies are sandwiched between two transparent substrates. Providing a bottom substrate having a conductive surface, providing a hot melt adhesive sheet, embedding an LED die having a top electrode and a bottom electrode in the hot melt adhesive sheet, and providing a top transparent substrate having a transparent conductive layer; The hot melt adhesive sheet is inserted between the conductive surface and the transparent conductive layer, passed through a heated pressure roller system to bond the top substrate to the bottom substrate, and as the hot melt sheet softens, the LED die Are separated so that the top electrode is in electrical contact with the transparent conductive layer of the top substrate and the bottom electrode is in electrical contact with the conductive surface of the bottom substrate, whereby the p-side and n-side of each LED die is Automatically connected to the top conductive layer and the bottom conductive surface. The upper transparent substrate and the conductive surface are insulated by a hot melt adhesive.

U.S. Pat. No. 4,4,9,5,5,4 Special table 2007-531321

Chemical Review, 2007, 107, 953-1010.

The structure and manufacturing method of the light emitting device described in Patent Document 2 does not require wire bonding, soldering, lead wires, or other electrical connection elements or steps, and has a description of a high yield and low cost method. Contributes to solving the first problem. Moreover, it is mentioned that it is effective also for high-density mounting, and if the brightness | luminance of one LED can be reduced, it will contribute also to the solution of a 3rd subject.

  The structure and manufacturing method of the light emitting device disclosed in Patent Document 2 have the following problems.

  In paragraph 49 of Patent Document 2, the hot melt material does not wet the surface of the LED die, so when the hot melt material melts, the p and n surfaces of the LED die are exposed and the top and bottom substrates are exposed. There is a description that electrical connection with the conductive surface is obtained. However, hot melt materials are well thought to wet the LED die surface with some probability. In this case, since the hot melt material is an insulating material, an electrical connection to the LED die cannot be obtained, and the device does not function as a light emitting device. This problem becomes a serious problem when a large number of light emitting devices are manufactured, and when yield is reduced by arranging a large number of LED dies. Furthermore, when the light emitting device is used for a long period of time, the hot melt material does not wet the surface of the LED die, and the electrode and the LED die are in direct contact with each other. There is also a problem that the service life is short because it is stable and is easily peeled off and electrically insulated by stress such as mechanical impact or bending.

  In order to solve this problem, it is necessary to make a structure using a material instead of a hot-melt material that is completely insulating.

  Patent Document 2 discloses a structure using an ion transport material (solid polymer electrolyte, fluid electrolyte, solid electrolyte) in a portion corresponding to a hot-melt material or a structure using a conductive adhesive as another form of the light-emitting device. doing.

  When a solid electrolyte or a conductive adhesive is used instead of a hot melt material, it is impossible to maintain electrical insulation between the surface electrode and the transparent conductive layer, and simple replacement cannot be performed.

  Patent Document 2 discloses a structure in which an essentially conductive polymer or a semiconductive adhesive is used in a portion corresponding to a hot melt material as another form of the light emitting device.

  When an essentially conductive polymer is to be used in place of a hot melt material, the conductive polymer generally has poor adhesion and cannot achieve adhesion like a hot melt material.

  Further, the semiconductive adhesive is not disclosed in Patent Document 2 as to what kind of material it is concretely. Generally speaking, conductive polymers include polyacetylene iodine-doped and poly (3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid. These were used instead of hot melt materials. In this case, it is impossible to maintain electrical insulation between the surface electrode and the transparent conductive layer, and a simple replacement is not possible.

  In Patent Document 2, as another embodiment of the light-emitting device, a conductive matrix that completes an electrical contact between the N electrode of the LED die and the ITO cathode by providing a gap between the N electrode of the LED die and the ITO cathode. There is a description of a structure using quinoline droplets as a material.

  Quinoline is a liquid material at room temperature with a melting point of −15 ° C. Since the liquid material has a low viscosity and easily changes its shape, the surface electrode and the transparent electrode cannot be bonded to each other. Therefore, the liquid material cannot be used in place of the hot melt material. Further, there is no description about the reason why electricity flows through the quinoline. Patent Document 2 describes whether the effect of suppressing the leakage current can be obtained by maintaining the insulation between the surface electrode and the transparent electrode where there is no LED die, such as a hot melt material. There is no description.

  The problem to be solved by the present invention is to solve the above-mentioned problems and to provide a large amount of light-emitting devices with high efficiency and long life at low cost.

The light-emitting device of the present invention includes an anode and a cathode that are substantially transparent, an LED die having a p-side and an n-side disposed between the anode and the cathode, and a portion disposed between the anode and the cathode. A light-emitting device comprising an organic layer containing an organic semiconductor material in contact with the LED die, wherein the LED die is arranged so that the n side is the cathode side and the p side is the anode side, and the organic layer has the LED die Is arranged so as to fill at least one of the n side and the cathode or between the p side and the anode in the cross section to be arranged, and arranged between the cathode and the anode in the cross section where the LED die is not present. The organic layer has a thickness of 1 micrometer or more in a cross section where the LED die is present and the LED die is not continuously present. The film thickness of the organic layer in the cross section where the ED die exists is 10 micrometers or less, and the film thickness of the organic layer in the cross section where the LED die does not exist is the film thickness of the organic layer in the cross section where the LED die exists. It is a light emitting device characterized by being thicker.

Here, the p-side of the LED die is defined as the side that is bonded to the anode and receives holes, and the n-side of the LED die is defined as the side that is bonded to the cathode and receives electrons. In an LED die using gallium nitride, the side on which the p-type gallium nitride layer is formed is the p-side, and the side on which the n-type gallium nitride layer is formed is the n-side. A layer generally called an electrode such as an indium tin oxide layer may be formed on the surface of the LED die.

  According to the present invention, the organic layer containing the organic semiconductor between the electrode and the LED die is responsible for the injection and transport of electrons or holes, so that the charge from the anode to the p side of the LED die or from the cathode to the n side of the LED die. Can be efficiently transported, the voltage required for light emission can be applied to the n side and p side of the LED with a small voltage loss. Since the organic layer containing an organic semiconductor does not electrically insulate between the electrode and the LED, it can be manufactured with a high yield, and in addition, a light-emitting device that emits light stably over a long period of time can be obtained.

  In the present invention, since the organic layer is continuously arranged over the portion where the LED die is present and the portion where the LED die is not present, it is not necessary to change the member by patterning or the like between the portion where the LED die is present and the portion where the LED die is not present. A light emitting device can be provided.

In the light emitting device of the present invention, there is a concern about leakage current flowing in the organic layer containing the organic semiconductor between the two electrodes in a portion where there is no LED die, but this is not substantially a problem. This is because, in the light emitting device of the present invention, the thickness of the organic layer in the cross section where the LED die does not exist is thicker than the thickness of the organic layer in the cross section where the LED die exists. Current in the case of injecting and transporting electrons or holes in an organic semiconductor is due to a mechanism called space charge limited current, but since the current density is inversely proportional to the cube of the film thickness, by providing a difference in film thickness, A large current contrast can be obtained between the portion where the LED die is present and the portion where the LED die is not present, and the amount of leakage current in the portion where the LED die is absent is negligible. For example, when the film thickness of the organic layer in the cross section where the LED die is not present is 10 times thicker than the film thickness of the organic layer in the cross section where the LED die is present, the current density in the cross section where the LED die is not present due to the inverse cube power is It becomes 1/1000 of the current density of the existing cross section. The ratio of the area where the LED die is present to the area where the LED die is absent varies depending on the application to be used. The thickness of each organic layer in the cross section where the LED die is present and the cross section where the LED die is not present can be determined from the ratio of the area where the LED die is present to the area where the LED die is not present, and the ratio of the desired LED current and leakage current. Good. This film thickness ratio can be realized by using a spacer, the viscosity of the organic material, the thickness of the LED die, and the like. In the light emitting device of the present invention, the leakage current can be effectively suppressed if the thickness of the organic layer in the cross section where the LED die is not present is 1 micrometer or more. If the film thickness is less than this, it becomes difficult to suppress the generation of pinholes, and currents not caused by pinholes cannot be ignored. If the film thickness of the organic layer in the cross section where the LED die is present is 10 micrometers or less, a current can be injected into the LED with a small voltage drop. If the film thickness is larger than this, the voltage drop in the organic layer becomes too large, and the power consumption of the device becomes too large.

  As another form of the present invention, the organic light-emitting device of the present invention includes an organic layer having a glass transition temperature of 25 ° C. or lower and capable of maintaining a stable supercooled liquid state at 25 ° C. The light emitting device.

  By using such an organic layer, the organic layer is in a supercooled liquid state at a standard room temperature of 25 ° C. Since the organic layer in this state has a sufficiently high viscosity, the two electrodes can be adhered to each other so as not to be separated, and the device can be kept mechanically stable. Since it is in an amorphous state, there is no grain boundary like a polycrystal, and it does not cause an electrical short circuit. In addition, even when stress is applied to the device due to external force or temperature change, the supercooled liquid in the organic layer can be deformed appropriately, so that stress can be relaxed to prevent device destruction due to peeling or cracking. it can. Therefore, due to the effects of the present invention, the light emitting device of the present invention is resistant to mechanical impact and has flexibility. For example, when a plastic substrate is used, it can be bent.

  The materials that can be used as the organic layer in the previous paragraph of the present invention are limited. This is because the organic layer has a thermodynamic property that the glass transition temperature is 25 ° C. or less, a morphological stability that can maintain a supercooled liquid state, and an energy level that allows holes or electrons to be injected from the electrode. This is because it is necessary to satisfy many required performances of high mobility of holes or electrons.

  In the present invention, a light-emitting device using a material having a triarylamine moiety and an alkyl group or alkoxy group having 2 to 16 carbon atoms as an organic semiconductor contained in an organic layer satisfying such required performance has been invented. The triarylamine moiety is highly stable in a supercooled liquid state because three aryl groups bonded to nitrogen are in a propeller-like positional relationship with each other and have low planarity, so that crystallinity can be inhibited. Alkyl or alkoxy groups having 2 to 16 carbon atoms can take various conformations, which also contributes to the improvement of the stability of the amorphous state and can be adjusted to room temperature or lower by lowering the glass transition temperature. Also contributes. The glass transition temperature is considered to be the temperature at which molecular groups begin to move cooperatively. When there is an alkyl group or alkoxy group that is more mobile than an aryl group in the molecule, the cooperative movement of the molecular group is likely to occur at a lower temperature starting from the movement in the molecule, thus lowering the glass transition temperature. Is born. Furthermore, when the organic layer containing the organic semiconductor is used as a p-type organic layer, the triarylamine has an appropriate energy level capable of accepting holes from the anode and high hole mobility. It can take on the function of electrical conduction.

Another embodiment of the present invention is a light emitting device characterized in that a charge injection layer is formed on at least one of the anode and the cathode among the light emitting devices of the present invention.

By applying this structure, charge injection becomes easy, voltage loss required for charge injection can be prevented, and the required value of the energy level related to the injection barrier among the required performance of the material of the organic layer described above is relaxed. Therefore, a wider material system can be applied to the present invention.

The inventor has also invented a method for manufacturing a light emitting device of the present invention. The manufacturing method of the present invention includes a step of preparing a substrate having an anode and a substrate having a cathode, a step of disposing an LED die on one of the two substrates, and an organic material containing an organic semiconductor as an LED die. A step of placing the substrate on the other substrate, the step of lowering the viscosity by heating the organic material, and the step of sandwiching the organic material between two substrates in this order. A device manufacturing method.

By manufacturing the light emitting device by applying this manufacturing method, in the process of heating the organic material and sandwiching it between two substrates with low viscosity, the organic semiconductor is spread and formed as a continuous film, and the two substrates are bonded. The mechanical strength of the light emitting device can be obtained by arranging the layers. In addition, since the organic semiconductor wets and spreads so that the distance between the two substrates is constant, the structure of the present invention is automatically obtained in which the portion where the LED is present is thin and the portion where the LED die is not present is thick. Therefore, since the structure of the present invention that can deliver charges to the LED die with a small voltage loss and can reduce the leakage current in a portion where there is no LED can be easily realized, the mounting process can be greatly simplified, and the light emitting device of the present invention can be realized. Can be manufactured at low cost. When the area of the substrates is large, the distance between the substrates may be kept constant using a spacer.

  According to the present invention, light-emitting devices with high efficiency and long life can be provided at low cost and in large quantities.

A mode for carrying out the present invention will be described in detail. The present invention provides an anode and a cathode, which are substantially transparent, an LED die having a p-side and an n-side disposed between the anode and the cathode, and disposed between the anode and the cathode, A light emitting device comprising an organic layer containing an organic semiconductor material in contact with an LED die, wherein the LED die is arranged so that the n side is the cathode side and the p side is the anode side, and the organic layer is in a cross section where the LED die exists Is arranged so as to fill at least one of between the n side and the cathode or between the p side and the anode, and is arranged so as to fill between the cathode and the anode in the cross section where the LED die does not exist. The organic layer in the cross section where the LED die does not exist is 1 micrometer or more, and the LED die exists. The film thickness of the organic layer in the cross section is 10 micrometers or less, and the film thickness of the organic layer in the cross section where the LED die is not present is thicker than the film thickness of the organic layer in the cross section where the LED die is present. It is the light-emitting device characterized.

The material of the substantially transparent anode or cathode includes a metal oxide electrode such as indium tin oxide, a thin film metal electrode having a thickness of 100 nm or less made of aluminum or silver, a carbon material such as carbon nanotube or graphene, silver And nanowire materials such as copper. As an electrode manufacturing method, a vacuum method, a dry method such as a sputtering method or a CVD method, or a wet method in which a precursor ink is applied and then baked can be used. The higher the transmittance of the transparent electrode for LED light emission, the lower the power consumption, so the closer it is to 100%, the more preferable, but it should be 10% or more. A lower electrode resistance value is preferable because voltage loss can be reduced, but a sheet resistance of 1000 ohms / square or less is sufficient. In general, since the conductivity of the transparent electrode is not high, if a relatively thick wiring made of a highly conductive metal is formed as an auxiliary wiring, the substantial resistance value can be greatly reduced, which contributes to the reduction of power consumption.

An opaque electrode may be used for one of the anode and the cathode. In this case, a general metal film or the like may be formed on the substrate, or a metal plate or metal film can be used as it is as an electrode and substrate.

When substantially transparent electrodes are used for both the anode and the cathode, a light-emitting device having optical transparency can be obtained. As a result, a see-through property that allows the viewer to see the side opposite to the side where the observer is present can be obtained through the planar light emitting device, which is practically valuable.

As the LED die having the p side and the n side, a commercially available vertical LED die can be suitably used. Note that a horizontal LED die in which p and n are taken out on the same surface side cannot be used in the present invention. This is because in order to obtain the effect of the present invention, the LED die is arranged so that the n side is the cathode side and the p side is the anode side, and either one of electrons or holes is placed in the organic layer formed as a continuous film. This is because the structure must flow.

The organic layer in the light emitting device of the present invention is continuously arranged over the portion where the LED die is present and the portion where the LED die is not present, and the thickness of the organic layer in the cross section where the LED die is not present is the organic layer in the cross section where the LED die is present It is necessary to be thicker than the film thickness. FIG. 1 is a schematic diagram of a cross-sectional view of a light-emitting device of the present invention, which satisfies the above-described film thickness relationship. In addition, the organic layer of the present invention needs to contain an organic semiconductor. When the organic layer containing the organic semiconductor is not doped, it does not contain charges in the film, and holes or electrons that are sources of current are given by injection from the electrodes. In this case, a current generally flows by a mechanism called a space charge limited current, and the current density J at this time is given by J = 9/8 μεV ² / L ³ (Equation 1). In Equation 1, μ is the mobility, ε is the dielectric constant, V is the applied voltage, and L is the film thickness. In the light emitting device of the present invention, the voltage applied between the electrodes, the mobility of the organic layer, and the dielectric constant are the same between the portion with and without the LED die, and only the film thickness is different. In Equation 1, since the current density is inversely proportional to the cube of the film thickness, the difference in film thickness is a large difference in current value. For example, if the thickness of the organic layer where the LED die is present is 1 micrometer and the thickness where the LED die is not present is 200 micrometers, the portion where the LED die is present is compared to the current density of the portion where the LED die is absent. A current having a current density 8,000,000 times higher flows. The current that flows in the portion where there is no LED die is a leakage current, which leads to a loss of power consumption of the entire light emitting device, but by applying the present invention, the effect of the present invention that suppresses the loss of power consumption due to the leakage current is obtained. It is done. In the light emitting device of the present invention, the leakage current can be effectively suppressed if the thickness of the organic layer in the cross section where the LED die is not present is 1 micrometer or more. If the film thickness is less than this, it becomes difficult to suppress the generation of pinholes, and currents not caused by pinholes cannot be ignored. If the film thickness of the organic layer in the cross section where the LED die is present is 10 micrometers or less, a current can be injected into the LED with a small voltage drop. If the film thickness is larger than this, the voltage drop in the organic layer becomes too large, and the power consumption of the device becomes too large. It should be noted that the difference in current density between the portion with and without the LED die is determined by the design and use of the light-emitting device, thereby determining how much the film thickness difference should be provided. . In addition, although the voltage drop of the LED die is present in the portion where the LED die is present, it is described as being negligible in the above description because it is sufficiently smaller than the voltage drop of the organic layer having the same film thickness. In addition, the actual current-voltage characteristics of organic semiconductors may deviate from the ideal formula 1, but the current characteristics can be used for the light-emitting device of the present invention as long as the current value changes greatly with the change in film thickness. I will supplement what I can do.

Equation 1 is a conventionally known theory, and a difference in film thickness causes a difference in current density. The thickness of the LED die is usually 100 micrometers or more, and the thickness of the organic semiconductor film used in the organic EL, which is a general organic semiconductor application, is in the range of about 0.01 to 0.1 micrometers. There has been no idea of using an organic semiconductor in a thick film thickness range that can cover an LED die, and there is no precedent applied as a method for mounting an LED die, so the present invention is epoch-making and has an inventive step. It can be said that it is an invention.

As the organic layer containing the organic semiconductor material in contact with the LED die, p-type and n-type materials can be used. In the case of the p-type, the organic layer is disposed between the p-side of the LED die and the anode, and carries holes injected from the anode to the p-side of the LED die. In the case of the n-type, the organic layer is disposed between the n side of the LED die and the cathode, and carries electrons injected from the cathode to the n side of the LED die. The organic semiconductor material is necessary for obtaining the effects of the present invention, but other materials may be mixed as necessary. For example, a polymer that does not exhibit conductivity may be mixed as a binder resin. An inorganic material may be mixed, and as the inorganic material, a hole doping material such as tungsten oxide or molybdenum oxide, or an electron doping material such as cesium carbonate, alkali metal, or alkaline earth metal may be mixed. Increasing the charge density in the organic film by adding a charge-doping material increases the leakage current by deviating from the film thickness dependence of the space charge limiting current (1), but improves the electrical junction between the LED die and the electrode. This has the effect of reducing the contact resistance. Further, other organic semiconductor materials may be mixed. Alternatively, a plasticizer such as bis (2-ethylhexyl) phthalate may be added to increase flexibility.

In the present invention, the p-side or n-side of the LED die may be an electrical connection method other than the organic layer. For example, the LED and the electrode may be electrically connected using a metallic solder, or a conductive paste such as a silver paste may be used.

Both the p-type and n-type sides of the LED die may be electrically connected by an organic layer. in this case,
As shown in FIG. 2, both sides of the p-type and n-type may satisfy the relationship of the thickness of the organic layer of the present invention, or only one side of the thickness of the organic layer of the present invention is as shown in FIG. You may satisfy the relationship.

Furthermore, the inventor invented a light-emitting device including an organic layer in which the glass transition temperature of the organic layer used in the light-emitting device of the present invention is 25 ° C. or lower and can maintain a stable supercooled liquid state at 25 ° C. did.

Organic semiconductors are classified into two types, crystalline and amorphous (glass). Among these, since the crystalline film becomes a polycrystalline film, an electrical short circuit is likely to occur at the interface between crystal grains in the film, which is not suitable for practical use. Amorphous materials have homogeneity in which no interface exists in the film, so there is no electrical short circuit and the practicality for electrical devices is high.

Until now, organic semiconductor materials having a high glass transition temperature have been developed in order to increase the heat resistance of the device. This is because in an ultra-thin device having a total film thickness of about 0.1 to 0.3 micrometers such as an organic EL, an electrical short circuit is likely to occur at a temperature higher than the glass transition temperature. On the other hand, when considering a film containing an organic semiconductor having a thickness of 100 micrometers or more as in the present invention, an electrical short circuit that easily occurs at a glass transition temperature or higher can be ignored because it is a thick film. On the other hand, since the glass state of organic semiconductors is generally weak and weak in mechanical strength, it is necessary to consider means for preventing the film from being damaged by external stress in a thick film of 100 micrometers or more. The inventor has invented that the problem of mechanical strength can be solved by using an organic layer containing an organic semiconductor that is at or above the glass transition temperature at room temperature (typically 25 ° C.), that is, in a supercooled liquid state.

The use of a supercooled liquid not only prevents cracking in the film in a rigid device using a glass substrate and the like, and accompanying film peeling, but also in a flexible device using a plastic film substrate or a metal film substrate. The effect of preventing the occurrence of cracks in the film and the accompanying film peeling is great.

In general, in a supercooled liquid state of an organic semiconductor, molecules are in a state of being easily moved, so that they are easily rearranged and crystallized. Therefore, a material capable of maintaining a stable supercooled liquid state is required for the present invention.

The inventors have invented a material having a triarylamine moiety and an alkyl group or alkoxy group having 2 to 16 carbon atoms as an organic semiconductor highly compatible with the present invention. This material system can achieve both the glass transition temperature below room temperature and the stability of the supercooled liquid state. In the triarylamine moiety, three aryl groups are arranged non-planar with respect to the amine (nitrogen atom), and crystallization is suppressed to inhibit intermolecular alignment, and the stability of the supercooled liquid state To increase. Alkyl groups or alkoxy groups with a large number of carbon atoms have the effect of lowering the glass transition temperature because bonds between carbon atoms are easy to rotate within the alkyl chain. Increase the stability of the liquid state. The longer the alkyl chain, the lower the glass transition temperature and the stability of the supercooled liquid state. However, if the alkyl chain is too long, the alkyl chains tend to align with each other and promote crystallization. The number of alkyl chains must be selected. These compounds are also excellent in adhesion to glass, ITO electrodes, metals, polymer resins, etc., and show high performance for bonding and fixing two electrodes or substrates.

In this invention, it invented that the compound of General formula (1)-(8) shown below can be used suitably. Here, in the general formulas (1) to (8), R1 to R8 represent an alkyl group or an alkoxy group and may be the same or different from each other, and one or more of them are an alkyl group having 2 or more carbon atoms. , Ar1 to Ar4 represent an aryl group and may be the same or different from each other. The triphenylamine moiety common to the general formulas (1) to (8) creates a non-planar structure, and has an effect of maintaining a stable supercooled liquid state and an effect of increasing the melting point to room temperature or higher. In addition, the triphenylamine moiety has a function of accepting and carrying holes when these materials are used for a p-type semiconductor. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propyloxy group, an isopropyloxy group, an n-butoxy group, a sec-butoxy group, and a tert-butoxy group. As the number of carbons contained in the alkyl group or alkoxy group, the glass transition temperature tends to decrease as the number of carbons increases. However, as the number of carbons increases and the alkyl chain becomes longer, the crystallinity increases and a stable supercooled liquid state is maintained. Since it becomes impossible, it is preferable that it is in the range of 1 to 20. The aryl group is a substituent of an aromatic hydrocarbon such as a phenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, or an anthryl group, and these may further have a substituent. R1 to R8 and Ar1 to Ar4 may be substituted at any position of the ortho, meta, and para positions of the benzene ring. The aryl group having 6 to 40 carbon atoms can be suitably used.

Of the general formulas (1) to (8), more specific chemical structures include those shown in chemical formulas 9 to 17, but the present invention is not limited to these.

The inventor has invented a light emitting device in which a charge injection layer is formed on at least one of an anode and a cathode.

As the charge injection layer for facilitating charge injection, materials such as those used in organic EL and organic solar cells can be suitably used.

Suitable examples of the hole injection layer used between the anode and the p-type organic layer include, but are not limited to, tungsten oxide, molybdenum oxide, copper phthalocyanine, triphenylamine derivatives, and And cyan compounds. An example of the cross-sectional structure of the device when the hole injection layer is used is shown in FIG.

Suitable as the electron injecting layer used between the cathode and the n-type organic layer is not limited to these, but lithium salts such as lithium fluoride and lithium oxide, lithium complexes such as lithium quinoline, Examples thereof include cesium salts such as cesium carbonate, alkaline earth metals such as barium, and oxides of alkaline earth metals such as barium oxide. An example of the cross-sectional structure of the device when the electron injection layer is used is shown in FIG.

As a manufacturing method of the present invention, first, two substrates having electrodes are prepared. Preparation includes a step of cutting a substrate from a mother size, a step of performing patterning by a method such as photolithography if electrode patterning is necessary, and a step of forming an insulating layer if a spacer or other insulating layer is required, and forming a photo It includes a patterning process by a method such as lithography, and a surface cleaning process by a method such as ultraviolet irradiation, ozone exposure, and plasma exposure. Next, an LED die is placed on one of the two substrates. In order to place the LED die at a predetermined position, a step of recognizing the position of the substrate to be arranged based on the outer shape of the substrate to be arranged or the alignment mark on the substrate, and a blue sheet on which the LED die is fixed at the time of purchase And a step of lifting the LED die to a position to be arranged, a step of lowering and fixing the LED die to the substrate, and the like. When fixing the LED die to the substrate, it is necessary to fix the LED die in a positional manner and to obtain a stable electrical connection with the electrode. In order to satisfy these two simultaneously, there is a method using a conductive adhesive. As the conductive adhesive, a paste-type conductive adhesive containing a metal such as silver or a heat-meltable metal such as solder can be used. In the case of using a paste-like conductive adhesive containing a metal, a step of attaching the conductive adhesive to the side of the LED die that contacts the substrate and then placing it on the substrate and then solidifying it by heating or the like may be taken. Alternatively, a predetermined amount of conductive adhesive may be applied to a desired position on the substrate, and then the LED die may be placed thereon and solidified by a method such as heating. Similarly, when using a heat-meltable material such as solder for fixing and electrical connection, it may be attached to the LED die first and then joined to the substrate, or it may be first placed on the substrate side and then joined to the LED die. May be. As another method of bonding the LED die to the substrate, an organic semiconductor or an organic conductive layer is formed on the substrate, and the fixed and electrical connection is performed by bonding on the layer or embedding in the layer. May be obtained. As mechanical equipment for placing the LED die at a predetermined position, a semiconductor chip or a mounter for the LED die can be used. In order to dispose the organic material containing the organic semiconductor on the substrate on which the LED die is disposed or on the other substrate, the organic semiconductor may be evenly disposed on the substrate at a certain interval. Existing machinery such as a dispenser can be diverted as mechanical equipment for implementing this. The substrate on which the organic semiconductor is placed may be on the substrate side on which the LED die is placed or on the other substrate side. A method of heating the substrate on which the organic semiconductor is disposed can be applied to the step of heating the organic material to lower the viscosity. In the step of sandwiching the organic material between the two substrates, one or both substrates may be lifted and bonded together. In order to prevent air or gas from entering, a vacuum laminate may be used. After that, when cooled to room temperature, the adhesive layer containing the organic semiconductor becomes a supercooled liquid, the viscosity is increased, and the two substrates are fixed in position in order to develop adhesiveness, and can be handled as one light emitting device as a whole. become able to.

In this example, a light-emitting device using an organic semiconductor material represented by Chemical Formula 9 as an organic layer is described.

The compound shown in Chemical formula 9 was synthesized by the following method. In a 200 ml three-necked flask equipped with a condenser tube, 5.0 g of 4,4 ′, 4 ″ -triiodotriphenylamine, 7 ml of N-ethyl-m-toluidine, 7 g of potassium carbonate, 18- Add 1.3 g of crown-6-ether, 1.5 g of copper powder, and 20 ml of mesitylene. Introduce nitrogen into the three-necked flask and fully replace it. Next, the reaction system is heated to 170 ° C., and the mesitylene is refluxed with stirring to react for 10 hours. Solid potassium carbonate, copper powder, and produced potassium iodide are removed from the reaction solution by filtration. Then, 3.1 g (yield 60%) of the compound shown in Chemical formula 9 was obtained by repeating silica gel column chromatography (developing solvent toluene: hexane = 1: 9). As a result of performing mass spectrometry of the obtained compound by atmospheric pressure chemical ionization method, molecular ion peak m / z = 644.4 was obtained.

Although the compound of Chemical formula 9 shows a transparent glass-like appearance at room temperature, it has the flexibility to change its shape by being dented when pressed with a medicine spoon or the like. When the glass transition temperature of the compound of Chemical formula 9 was measured by differential scanning calorimetry, it was 9 ° C., which was a glass transition temperature sufficiently lower than room temperature, and was found to be a supercooled liquid at room temperature. The results of differential scanning calorimetry when heated from the glass state at −50 ° C. are shown in FIG. In addition, even if this supercooled liquid was allowed to stand at room temperature for several months or heated to 100 ° C. or higher, no crystallization was confirmed, and it was found that the supercooled liquid state of this compound was extremely stable.

In addition, the compound of Chemical formula 9 contains four electron-donating amino groups in the π-conjugated system and has the property of emitting electrons. 4,4 ′, 4 ″ -tris [3-methylphenyl (phenyl) amino] tri is known as a compound that facilitates hole injection from an indium tin oxide electrode as a hole injection material for organic EL. Phenylamine (hereinafter referred to as m-MTDATA) exhibits an ionization potential of 5.1 eV in the solid state. When the chemical structures of m-MTDATA and Chemical 9 are compared, the compound of Chemical formula 9 has three phenyl groups as ethyl groups. It is a compound having an equivalent ionization potential and capable of easily injecting holes from an electrode such as indium tin oxide.

As the light-emitting device of the present invention, a light-emitting device having a top view shown in FIG. 7 and a cross-sectional view shown in FIG. 8 was prepared by the following method. ES-CAHR509, which is a red LED manufactured by Epistar, was used as the LED die. The size of the LED die is 230 μm × 230 μm in length × width, and the thickness is 170 μm. As the substrate, a 10 mm × 20 mm glass substrate on which an ITO electrode 100 nm was formed was used (hereinafter referred to as ITO substrate 1). First, a silver paste was placed at a predetermined position on the ITO substrate 1. Next, the LED die is placed on the silver paste with tweezers so that the n side is the ITO electrode side of the ITO substrate 1, and the substrate is baked at 120 ° C. to evaporate the solvent in the silver paste and solidify the silver paste. This fixed the LED die. Next, as a counter substrate, a 10 mm × 20 mm glass substrate on which ITO was deposited to a thickness of 100 nm was prepared (hereinafter referred to as ITO substrate 2) in the same manner as the substrate on which the LED die was arranged. The ITO substrate 1 and the ITO substrate 2 are placed on a hot plate heated to 150 ° C. and heated. In this state, a small amount of the compound of Chemical formula 9 is placed on the ITO substrate 2. When the compound of the arranged chemical formula 9 is heated, the viscosity decreases, so that it spreads wet. In this state, when the ITO substrate 1 on which the LED dies are arranged is placed on the ITO substrate 2 in the positional relationship shown in FIG. 7, the chemical compound 9 is further wetted by the weight of the ITO substrate 1 and the two ITO substrates overlap. It spreads over the whole part. Thereafter, when the ITO substrates that overlap each other were lowered from the hot plate and cooled, the compound of chemical formula 9 cooled and the viscosity increased, so that even when force was applied, the two substrates were bonded without being separated.

A direct current voltage was applied to the light emitting device produced by the method of the previous paragraph so that the ITO substrate 1 was negative and the ITO substrate 2 was positive. Red light emission based on the light emission of the LED die was obtained by applying a voltage of 1.6 V or more. A photograph of the light emission state is shown in FIG. Note that since the light emitting device of this example has high transparency of the two ITO substrates and the compound represented by Chemical Formula 9, the light emitting device has a see-through property where the other side of the observer can be seen through the light emitting device.

In this example, Example 1 was used except that an ITO film substrate manufactured by Nitto Denko Corporation in which an ITO substrate was formed on a 50 micrometer plastic film substrate made of polyethylene terephthalate as the ITO substrate 1 and the ITO substrate 2 was used. A light emitting device was created in the same manner as described above.

A direct current voltage was applied to the light emitting device produced by the method of the previous paragraph so that the ITO substrate 1 was negative and the ITO substrate 2 was positive. Red light emission based on the light emission of the LED die was obtained by applying a voltage of 1.8 V or more. Note that the light-emitting device of this example also has two ITO substrates and the compound represented by Chemical Formula 9 has high transparency, and thus has a see-through property that allows the viewer to see the other side through the light-emitting device. In addition, the light-emitting device of the present invention has flexibility, and it was confirmed that light emission was obtained even when the substrate was bent.

In this embodiment, a conventional organic semiconductor material 2-TNATA shown in Chemical Formula 19 is used as an organic layer containing an organic semiconductor, and a hot plate heated to 280 ° C., which is higher than 245 ° C., which is the melting point of 2-TNATA, is used. A light emitting device was manufactured in the same manner as in Example 1 except that the above was found.

A direct current voltage was applied to the light emitting device produced by the method of the previous paragraph so that the ITO substrate 1 was negative and the ITO substrate 2 was positive. Red light emission based on the light emission of the LED die was obtained by applying a voltage of 1.6 V or more. Note that since the light emitting device of this example has high transparency of the two ITO substrates and the compound represented by Chemical formula 19, it has a see-through property that allows the viewer to see the other side through the light emitting device.

At the time of producing the light emitting device of Example 3, 2-TNATA of Chemical Formula 19 forms glass at a glass transition temperature of 110 ° C. or lower, but crystallizes in a temperature region (110 to 245 ° C.) below the melting point or higher during cooling. In some cases, crystallization occurred. When crystallized, the adhesion with the ITO substrate is lowered, and the substrate and the organic layer are separated, so that it cannot function as a light emitting device, and there is a problem that the yield of the device is lowered. Even if a glass film is formed without crystallization, the glass film is mechanically fragile, so that it is mechanically broken by internal stress based on the difference between the thermal expansion coefficient of ITO or glass and the thermal expansion coefficient of the organic layer. There are things that reduce device yield.

In comparison between Example 1 and Example 3, using a film containing an organic semiconductor in a supercooled liquid state at room temperature has a higher yield than using a film containing an organic semiconductor having a glass transition temperature equal to or higher than room temperature. It was found that stable light emission can be obtained. This is because the stress can be relieved because the supercooled liquid state has the flexibility to change the shape of the film, and the light emitting device that bends by utilizing the flexibility of the supercooled liquid as in Example 2 You can also get

The light emitting device provided by the present invention can be suitably used for illumination, a display, and the like.

Schematic diagram of a cross-sectional view of the light-emitting device of the present invention Schematic diagram of a cross-sectional view of a light emitting device having p-type and n-type organic layers of the present invention Schematic diagram of a cross-sectional view of a light emitting device having p-type and n-type organic layers of the present invention Schematic diagram of a cross-sectional view of a light emitting device having a hole injection layer of the present invention Schematic diagram of a sectional view of a light emitting device having an electron injection layer of the present invention DSC thermogram of differential scanning calorimetry of compound 9 of the present invention The schematic diagram which looked at the light emitting device of this invention of Examples 1-3 from the top Schematic diagram of the cross-sectional view of the dotted line in FIG. 7 (does not represent the actual size ratio) Photograph at the time of light emission of Example 1

1 Electrode 1
2 Organic layer containing organic semiconductor 3 Electrode 2
4 LED die 5 Cathode 6 Anode 7 n-type organic layer 8 p-type organic layer 9 n-side of LED die 10 p-side of LED die 11 hole injection layer 12 electron injection layer 13 ITO substrate 1 (substrate on the anode side)
14 ITO substrate 2 (cathode side substrate)
15 Silver paste

Claims (6)

An anode and a cathode, one of which is substantially transparent, an LED die having a p-side and an n-side disposed between the anode and the cathode, and disposed between the anode and the cathode and in contact with the LED die A light emitting device comprising an organic layer containing an organic semiconductor material, wherein the LED die is arranged so that the n side is the cathode side and the p side is the anode side, and the organic layer is n side in the cross section where the LED die exists In the cross section where the LED die is not present and between the cathode and the p side and the anode, the portion where the LED die is present is arranged so as to be filled between the cathode and the anode. In the section where the LED die is present, the film thickness of the organic layer in the section where the LED die is not present is 1 micrometer or more. The film thickness of the organic layer is 10 micrometers or less, and the film thickness of the organic layer in the cross section where the LED die does not exist is thicker than the film thickness of the organic layer in the cross section where the LED die exists. A light emitting device. The light emitting device according to claim 1, wherein the organic layer has an organic layer having a glass transition temperature of 25 ° C. or lower and capable of maintaining a stable supercooled liquid state at 25 ° C. The light emitting device according to claim 2, wherein a material having a triarylamine moiety and an alkyl group or an alkoxy group having 2 to 16 carbon atoms is used as an organic semiconductor contained in the organic layer. device. The light emitting device using the organic compound represented by General formula (1)-(8) among the light emitting devices of Claim 3. Here, in the general formulas (1) to (8), R1 to R8 represent an alkyl group or an alkoxy group and may be the same or different from each other, and one or more of them are an alkyl group or alkoxy having 2 or more carbon atoms. Ar1-Ar4 represents an aryl group, which may be the same or different from each other, and R1-R8 and Ar1-Ar4 may be substituted at any position of the ortho, meta, and para positions of the benzene ring. .
The light-emitting device according to claim 1, wherein a charge injection layer is formed on at least one of the anode and the cathode. 2. The method of manufacturing a light emitting device according to claim 1, wherein a step of preparing a substrate having an anode and a substrate having a cathode, a step of disposing an LED die on one of the two substrates, and an organic The step of arranging an organic material containing a semiconductor on the substrate on which the LED die is arranged or the other substrate, the step of lowering the viscosity by heating the organic material, and the step of sandwiching the organic material between two substrates A method for manufacturing a light-emitting device comprising the steps of: