JP2004179108A - Organic electroluminescence device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL device suitable for light source in which, even if one sheet of large substrate is used, the jointing strength of a container composed of the substrate is increased and early deterioration of the EL element is prevented, and which is improved in light emission characteristics and life characteristics. <P>SOLUTION: The organic EL device 1A is composed of a first substrate 2 having optical transparency, EL elements 4 formed by successively laminating a plurality of positive electrode layers 3, luminous layes 4, and negative electrode layers 5 on the substrate 2 in matrix form, and a second substrate 7 joined with the first substrate 2, covering these EL elements 4, and dividing EL element 4 at every section. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence (hereinafter, referred to as EL) device serving as a planar light source used for a backlight of a matrix type display device or a liquid crystal display device.
[0002]
2. Description of the Related Art Solid planar light sources composed of organic EL devices are thinner and lighter than LCDs (liquid crystal displays), LEDs (light emitting diodes), PDPs (plasma display panels), etc., and their display areas are compared. It is expected to be a promising light source for display devices, backlights, or illumination, which has excellent overall characteristics such as brightness, contrast, visual field, and flicker required to obtain large, high-quality images.
[0003]
This organic EL device has a structure in which a transparent anode layer made of a conductive material such as indium oxide In ₂ O _{3 is formed} on one of a pair of substrates such as glass, and N, N-diphenyl-N, N-bis. A hole transport layer composed of (3-methylphenyl) 1,1'-biphenyl-4,4'-diamine or the like; an organic light-emitting layer composed of tris (8-hydroxyquinalina) aluminum (Alq3) and quinacdrine; And an electron transport layer made of tris (8-hydroxyquinalinato) aluminum (Alq3) or the like, and a cathode electrode layer made of a low work function metal material such as aluminum or an aluminum alloy and lithium fluoride (LiF) are deposited and sputtered. , Are sequentially laminated by means such as screen printing or pasting, and the other substrate is disposed so as to cover this The part near are joined via an adhesive.
[0004]
Then, when a voltage is applied between the electrodes, the free electrons slightly existing in the light emitting layer are accelerated by a high electric field, and are excited at the emission center to emit light and increase the number of free electrons. When the electric field is removed, the free electrons accumulated at the movable end move in the opposite direction, emit light by recombination, and pass through the one light-transmitting substrate to emit light.
[0005]
In the EL device having the above configuration, when the size of the substrate is increased in order to increase the area of the light emitting portion, the stress applied to the adhesive bonding the two substrates increases, and the EL device leaks from the bonded portion and enters the EL device. Oxygen or moisture may enter or the organic light emitting layer may be overheated by Joule heat during light emission.
[0006]
When such a leak or overheating occurs, the organic light emitting layer formed of Alq3 or the like is oxidized and deteriorated early, or becomes an insulator by being crystallized from an amorphous state to a glassy state. There is a problem that predetermined light emission characteristics and life characteristics cannot be obtained, for example, light emission stops.
[0007]
The light emitted from the organic light emitting layer passes through the one light transmissive substrate and is emitted, but there is also light traveling in the lateral direction in the container formed by the pair of substrates and toward the other substrate. Since this light is not used, a desired luminous efficiency may not be obtained, or brightness unevenness may occur on the light emitting surface of the substrate.
[0008]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. Even when a single large substrate is used, the bonding strength of a container made of a substrate or the like is increased so that an EL element can be formed by invasion of outside air. It is an object of the present invention to provide an organic EL device suitable for a light source capable of preventing early deterioration of the light emitting device and improving the light emission characteristics and the life characteristics.
[0009]
According to the first aspect of the present invention, there is provided an organic EL device comprising a light-transmissive first substrate, a plurality of anode layers and a plurality of light-emitting layers provided on the substrate in a matrix. And an EL element formed by sequentially laminating a cathode layer and a second substrate which covers the EL element and is divided for each EL element and joined to the first substrate.
[0010]
The organic EL device according to claim 1 is an assembly in which the EL element is divided and a set of EL elements is sealed in a small partitioned container, and is formed by a partition or the like that partitions the periphery of a small area. And the temperature rise of the EL element at the time of energization becomes lower than before, so that the stress at the joint due to the temperature rise can be reduced, and peeling from the joint can be prevented. .
[0011]
Therefore, it is possible to suppress deterioration of the organic light emitting layer formed of Alq3 or the like due to leakage or overheating, such as oxidation or crystallization.
[0012]
In addition, in this organic EL device, the EL elements arranged in rows and columns in a matrix are turned on by applying a voltage to all anode terminals and cathode terminals, and all EL elements are turned on, and only desired EL elements are turned on. In the case of lighting, since only the anode terminal and the cathode terminal drawn out from the intersection of the column and the row of the corresponding EL element need to be energized, various lighting modes can be obtained.
[0013]
In the present invention and each of the following inventions, definitions and technical meanings of terms are as follows unless otherwise specified.
[0014]
For the first substrate constituting the organic EL device according to the present invention, a material such as glass, synthetic resin or ceramics having good light transmittance is used.
[0015]
The second substrate bonded to the first substrate via an adhesive is made of a material such as glass, synthetic resin, metal, ceramics, etc., but the light transmittance is not required except in special cases.
[0016]
The second substrate may be a single substrate that covers the first substrate and is provided with a partition for partitioning each EL element, or a dome-shaped concave covering each EL element. The portions may be individually formed and each may be individually joined.
[0017]
In addition, when the first and second substrates are joined, by forming a groove-shaped portion on the first substrate that coincides with the joining peripheral portion of the second substrate, the positioning of both is easy and accurate. It is possible to prevent the adhesive from flowing out to an undesired portion.
[0018]
An EL element has at least an organic light emitting layer laminated between an anode layer and a cathode layer, and a hole injection layer for facilitating injection of electrons from electrodes before and after the organic light emitting layer, It may have a multilayer structure in which a hole transport layer, an electron transport layer, and the like are formed therebetween.
[0019]
As the anode layer, a transparent conductive film such as nickel, gold, silver, platinum, palladium, an alloy thereof, antimony tin oxide or indium tin oxide (ITO) can be used. The ITO film is often used, and since this layer transmits light in the visible region well, it is preferable to form the layer on the first substrate side that emits light.
[0020]
The cathode layer is made of a material effective for electron injection, such as aluminum, magnesium, magnesium indium alloy, magnesium aluminum alloy, magnesium silver alloy, indium Pd, and aluminum lithium alloy. High aluminum and magnesium silver alloys are preferred.
[0021]
As the light-emitting layer, tris (8-hydroxyquinalinato) aluminum (hereinafter, referred to as Alq3) or the like can be used.
[0022]
Further, for example, when it is desired to obtain red, green, and blue light emission colors for illumination, the red light-emitting layer is formed by adding [2- [2- [4- (dimethylamino) phenyl] ethynyl] -6-methyl-4H to Alq3. -Ylidene] -propanepropane dinitrile (DCM dye) doped structure, green is Alq3, blue is bis (2-methyl-8-quinolitrato, para-phenylphenolato) aluminum (BAlq) doped with penylene What is necessary is just to use the layer made.
[0023]
In the present invention, the emission color of the light emitting layer of the adjacent EL element may be red, green, or blue, for example. By doing so, highly efficient white light can be obtained.
[0024]
As the hole transport layer, bis [N- (1-nafquib) -N-phenyl] benzidine (hereinafter referred to as α-NPD) or N, N-diphenyl-N, N-bis (3-methylphenyl) For example, 1,1'-biphenyl-4,4'-diamine (hereinafter, referred to as TPD) can be used.
[0025]
As the electron transporting layer, lithium fluoride (LiF) or the like can be used.
[0026]
Then, a plurality of sets of EL elements are formed in a matrix on one substrate, and each layer can be formed by stacking a plurality of sets at a time by vapor deposition, sputtering, screen printing, pasting, or the like.
[0027]
As the adhesive for hermetically bonding the first and second substrates, an ultraviolet-curable adhesive such as acrylic epoxy can be used, but may be selected according to the material of the substrate.
[0028]
An organic EL device according to a second aspect of the present invention is characterized in that the cathode layer constituting the EL element has a visible light reflecting function toward the first substrate.
[0029]
When the cathode layer is formed of a material having high light reflectivity in the visible region, such as aluminum, silver, a magnesium silver alloy, or an aluminum lithium alloy, light coming from the light-emitting layer toward the cathode layer is irradiated to the cathode layer. 1 can be reflected to the substrate side, and the intensity of light emitted from the substrate can be increased.
[0030]
An organic EL device according to a third aspect of the present invention is characterized in that the second substrate has a function of reflecting visible light toward the EL element and / or the first substrate.
[0031]
The surface of the container formed by joining the first and second substrates, except for the light emitting surface, is formed of aluminum or silver exhibiting a visible light reflecting function, or is made of white such as barium carbonate or calcium oxide. By forming the film, radiated light other than from the light-emitting layer toward the first substrate is directed to the EL element or the first substrate, so that the intensity of the radiated light from the first substrate is increased to increase luminous efficiency. Can be improved.
[0032]
An organic EL device according to a fourth aspect of the present invention is characterized in that the second substrate has a concave shape.
[0033]
By directing the visible reflected light toward the substrate using the second substrate as a concave portion, the intensity of the emitted light can be increased and the luminous efficiency can be improved. By forming the concave portion as a visible light reflecting surface such as white or silver, the luminous efficiency can be further increased.
[0034]
An organic EL device according to a fifth aspect of the present invention is characterized in that a desiccant is provided in a container formed of the first and second substrates.
[0035]
If the airtightness is originally maintained, no impurity gas or the like will enter the container joined by the adhesive from the outside, and the EL element will not be deteriorated due to oxidation or the like, and the characteristics will not be deteriorated. In this case, a desiccant may be provided in the container.
[0036]
As the desiccant, diphosphorus pentoxide, barium oxide, calcium, or the like, which withstands the heat generation temperature at the time of energization and does not release oxygen or moisture, is bonded with an ultraviolet curing adhesive or a double-sided sealing material to form the second substrate. Fixed to.
[0037]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an organic EL (electroluminescence) device according to the present invention will be described below with reference to FIGS. FIG. 1 is a front view of the organic EL device 1A, and FIG. 2 is an enlarged sectional view schematically showing a portion cut along the line aa in FIG. (Including the figures shown below, the vertical and horizontal contrasts are not correct, and some parts are exaggerated such as the main parts.)
Four transparent planar anode layers 3 made of an ITO (indium tin oxide) film are formed on a first substrate 2 made of light transmissive glass, and a predetermined interval is formed on the anode layers 3. EL elements 4,... Are formed in a total of 16 squares of 4 × 4 horizontally in a grid pattern in this case.
[0038]
Each EL element 4 includes a hole transport layer 4a made of, for example, bis [N- (1-naphquib) -N-phenyl] benzidine (hereinafter referred to as α-NPD) on the anode layer 3, and a tris (8-hydroxy A light emitting layer 4b made of (quinalinato) aluminum (hereinafter referred to as Alq3), an electron transport layer 4c made of lithium fluoride (LiF), and a cathode layer 5 made of aluminum are sequentially laminated.
[0039]
Further, on the first substrate 2, the peripheral walls 61, 61 and the partition walls 62,... Of the second substrate 7 serving as the back surface on which the partition walls 62,. The tip is joined via an adhesive 8 such as an ultraviolet curing resin.
[0040]
Also, in the drawing, the drying agents 3a,... Provided on the inner surface side of the second substrate 7 in the containers 27,. The common anode terminal portions 5a,... Of the EL elements 4,... Are the common cathode terminal portions of the four sets of EL elements 4,.
[0041]
The bonding of the first substrate 2 and the second substrate 7 is performed by applying an adhesive 8 to one of the substrates 2 and 7 in advance and setting the substrate in an atmosphere of an inert gas such as argon or a nitrogen gas. Are filled in the containers 27,... Formed by the first and second substrates 2, 7.
[0042]
Incidentally, the organic EL device 1A has a structure in which the first substrate 2 has a length of about 50 mm × width of about 50 mm, one side of the second substrate 2 has a length of about 10 mm × width of about 10 mm, and The thickness is about 1 mm, and the height inside the container 27 is about 3 μm.
[0043]
In the organic EL device 1A having such a configuration, the EL elements 4,... Arranged in columns and rows are turned on by applying a voltage to all the anode terminals 3a,. ,... Are turned on, and only the desired EL element 4 is turned on, since only the anode terminal section 3a and the cathode terminal section 5a drawn out from the intersection of the vertical and horizontal rows of the EL element 4 need be energized. And various lighting modes can be obtained.
[0044]
The organic EL device 1A is an assembly in which a set of EL elements 4 is sealed in a container 27,... Which divides the EL elements and is divided into small parts, and is formed by a partition or the like dividing the periphery of a small area. And the temperature rise of the EL element 4 at the time of energization becomes lower than before, so that the stress at the joint due to the temperature rise is reduced, and the leakage due to peeling from the joint is reduced. Can be prevented.
[0045]
Therefore, the formed product of the organic light emitting layer 4b made of Alq3 or the like due to leakage or overheating is prevented from being deteriorated such as oxidation or crystallization, and is practically used as an illumination light source having improved light emission characteristics and life characteristics. Organic EL device can be provided.
[0046]
When the cathode layer 5 is formed of a material having good light reflectivity in a white visible region such as aluminum, light coming from the organic light emitting layer 4b toward the cathode layer 5 is reflected toward the first substrate 2 on the front surface side. As a result, the intensity of light emitted from the substrate 2 can be increased.
[0047]
The light emitted from the organic light emitting layer 4b passes through the one light-transmitting substrate 2 and is light-emitted. Since there is also light traveling toward the substrate 7, the other substrate 7 is formed of aluminum, or a film having good reflectivity of visible light is formed on the substrate 7, and the reflected light is directed to the one substrate 2. If this is the case, higher luminous efficiency can be obtained, and the occurrence of uneven brightness on the light emitting surface of the substrate 2 can be prevented.
[0048]
Further, in the present invention, the emission color of the light emitting layer of the adjacent EL element may be red, green, or blue, for example. By using blue, highly efficient white light can be obtained.
[0049]
FIGS. 3 to 7 show another embodiment of the organic EL device of the present invention. FIGS. 3 and 4 are schematic cross-sectional views, FIG. 5 is a front view, FIG. 6 is a rear view, and FIG. 6 is an enlarged cross-sectional view schematically showing a portion cut along the line bb in FIG. 6, where the same reference numerals are given to the same portions as those in FIGS. 1 and 2 and the description thereof will be omitted. 3 is different from the EL device 1A of FIG. 2 in that the partitions 62,... Are not formed on the second substrate 7 in the EL device 1B of FIG. Are formed by an adhesive 8 made of an ultraviolet curable resin or the like for joining the two.
[0050]
The partition walls 62,... Are formed by applying an adhesive 8 by screen printing or the like on the cells 2 at predetermined positions of the substrate 2 or 7 in advance in a linear manner, aligning the substrates 2 and 7, and irradiating ultraviolet rays. Is performed. The partition walls 62,... May be formed with the adhesive 8 inside the peripheral wall portion 61 around the second substrate 7, but the peripheral wall portion 61 of the substrate 7 may also be configured as shown in the figure. .
[0051]
The EL device 1C shown in FIG. 4 is composed of a dome-shaped concave assembly in which the second substrate 7 is divided, and each EL element 4,... Is covered by each concave portion 7a,. It is joined to one substrate 2 via an adhesive 8. Although not shown, the plurality of concave portions 7a,... May be formed on a single member at predetermined intervals, and the periphery of each concave portion 7a,.
[0052]
In the EL devices 1B and 1C, the EL elements 4,... Formed separately on the first substrate 2 are also partitioned and covered by the second substrates 7, 7a. In addition, it is possible to provide an EL device having the same operation and effect as those of the above-described embodiment, which can prevent excessive temperature rise. Also, in the case of the EL device 1C, for example, the inner surfaces of the concave portions 7a,... Covering the EL elements 4,... May be formed of a visible light reflector, and the reflected light may be directed to the first substrate 2. If this is the case, the radiated light from the first substrate 2 also increases, and the luminous efficiency can be improved.
[0053]
The desiccants 9 provided on the inner surface side of the second substrate 7 or 7a in each of the containers 27 partitioned by the partition walls 62 are formed by forming barium oxide or the like into a plate shape. , Which absorbs water, oxygen, and the like that enter from the outside due to the presence, generation, or change with time in the containers 27,... And performs an adsorption reaction, thereby preventing deterioration of the EL elements 4,. It works.
[0054]
The EL device 1D shown in FIGS. 5 to 7 has a lattice shape (row 8 × column 8) on the rear surface side (closer to the second substrate 7) of the first substrate 2 facing the EL elements 4,. The transparent portions 2c,... And the diffusion portions 2d,.
[0055]
The transparent portion 2c and the diffusion portions 2d are formed of, for example, acrylic, epoxy, or polyimide used for a photosensitive resist material by using cerium oxide (average particle size is 11 nm by BET method) or aluminum oxide (alumina) (average particle size by BET method). A material exhibiting light diffusivity, which is a mixture of 0.005 to 5.0% by weight of spherical fine particles having a diameter of 33 nm) is applied on the planar anode layer 3 made of an ITO film on the first substrate 2 and patterned. Processing (UV exposure, etching, rinsing) is performed to form a lattice.
[0056]
As for the EL elements 4,..., Each of which has eight rows of anode terminals 3a,... And each cathode terminals 5a,. Are provided at portions corresponding to the transparent portions 2c,. That is, the EL element 4 is provided at a portion corresponding to the transparent portion 2c,... Of the first substrate 2, but the portion corresponding to the diffusion portion 2d,. Not provided.
[0057]
In order to prevent the light emitted from the EL element 4 from escaping to the second substrate 7 due to the fiber effect, the EL device 1D comprises a first diffused film 2d in which spherical fine particles are dispersed and a cathode layer 5 having a back surface reflecting effect. Is incident on the substrate 2 and the light is extracted to the front surface, so that the light that has been conventionally irradiated to the end of the EL device 1D and lost can be effectively used.
[0058]
The organic EL device 1D can efficiently use the effects of the diffusion films 2d,... By surrounding the EL elements 4,. Further, compared to the conventional organic EL device, it can be driven at a lower voltage (approximately 4 to 6 V). In the experiment, the surface irradiation illuminance can be increased by 50%. Similarly, the life of reaching half luminance can be extended by 50%.
[0059]
According to the first aspect of the present invention, an EL element is divided and a set of EL elements is sealed in a small partitioned container. Provided is an organic EL device which is practically used as a light source for illumination and the like having improved light-emitting characteristics and life characteristics, in which the stress of a bonding portion due to a rise in temperature is reduced to prevent deterioration of the EL element. be able to.
[0060]
According to the second aspect of the present invention, the cathode layer constituting the EL element is formed of a material having high light reflectivity in the visible region, such as aluminum or silver, so that light coming from the light emitting layer toward the cathode layer can be formed on the surface. The intensity of the light radiated from the substrate is increased by reflecting the light to the first substrate side, thereby providing an organic EL device with improved light emission characteristics.
[0061]
In the organic EL device according to a third aspect of the present invention, the surface of the container formed by joining the first and second substrates except for the light emitting surface is formed of a material exhibiting a visible light reflecting function. By doing so, the intensity of light emitted from the EL element can be increased, and an organic EL device with improved emission characteristics can be provided.
[0062]
In the organic EL device according to the fourth aspect of the present invention, the intensity of the radiated light can be increased and the light emission characteristics can be improved by directing the visible reflected light to the substrate side by using the second substrate as a concave portion. By forming the concave portion as a visible light reflecting surface such as white or silver, an organic EL device with further improved light emission characteristics can be provided.
[0063]
In the organic EL device according to the fifth aspect of the present invention, by providing a desiccant in a container formed by the first and second substrates, water, oxygen, and the like existing in the device are adsorbed, and the organic EL device has an organic EL device. It is possible to provide an organic EL device in which light emission characteristics and life characteristics are improved and deterioration is prevented.
[Brief description of the drawings]
FIG. 1 is a front view showing an embodiment of an organic EL device according to the present invention.
FIG. 2 is an enlarged sectional view schematically showing a portion cut along the line aa in FIG.
FIG. 3 is a cross-sectional view schematically showing another embodiment of the organic EL device according to the present invention.
FIG. 4 is a cross-sectional view schematically showing another embodiment of the organic EL device according to the present invention.
FIG. 5 is a front view showing another embodiment of the organic EL device.
6 is a rear view of the organic EL device shown in FIG.
FIG. 7 is an enlarged sectional view schematically showing a portion cut along the line bb in FIG. 6;
[Explanation of symbols]
1A to 1D: organic EL device, 2: first substrate, 3: anode layer,
4: EL element, 4b: light emitting layer, 5: cathode layer, 7: second substrate,
8: adhesive, 9: desiccant,

Claims (5)

A light-transmissive first substrate;
An EL element in which a plurality of sets of an anode layer, a light-emitting layer, and a cathode layer are sequentially laminated on the substrate in a matrix;
A second substrate that covers the EL elements and is partitioned for each EL element and bonded to the first substrate;
An organic EL device comprising: The organic EL device according to claim 1, wherein the cathode layer constituting the EL element has a visible light reflecting function toward the first substrate. 3. The organic EL device according to claim 1, wherein the second substrate has a function of reflecting visible light toward the EL element and / or the first substrate. 4. The organic EL device according to claim 3, wherein the second substrate has a concave shape. The organic EL device according to any one of claims 1 to 4, wherein a desiccant is provided in a container formed by the first and second substrates.

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