JP2004087153A - Organic EL display - Google Patents

Abstract

[PROBLEMS] An external seal capable of accurately positioning an organic EL light emitting layer and a color filter and curing in a short time, and an internal seal transmitting light from the light emitting layer to the color filter without reflecting the light. To
An organic light-emitting element formed by laminating an anode, a light-emitting layer, a cathode, and a protective layer formed on a substrate, and a laminate of a color filter and a black mask formed on a transparent substrate are formed using an organic material. In an organic EL display in which an EL light emitting layer and a color filter are aligned and sealed and bonded, a substrate and a transparent substrate are bonded with a sealant having an ultraviolet curing function and a room temperature curing function.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic EL display which is high-definition, has excellent environmental resistance and productivity, and can be applied to a wide range of uses such as display of portable terminals and industrial measuring instruments.
[0002]
[Prior art]
2. Description of the Related Art In recent years, the speed of information communication and the range of applications have been rapidly increasing. Among them, there has been widely devised a high-definition display device having low power consumption and high-speed responsiveness capable of responding to requirements for portability and moving image display.
Above all, a color display device of a driving method using a thin film transistor (TFT) (active matrix driving method) has been devised for the colorization method. In this case, in the method in which light is extracted to the substrate side on which the TFT is formed, since the aperture ratio does not increase due to the light blocking effect of the wiring portion, recently, the light is emitted to the side opposite to the substrate on which the TFT is formed. An extraction method, a so-called top emission method, has been devised.
[0003]
Even in the case of the top emission method, in a method in which red, blue, and green light emitters are separately arranged in a matrix, three kinds of light emitting materials for RGB must be arranged in a matrix with high definition. The disadvantages are that it is difficult to manufacture efficiently and inexpensively, and at the same time, it is difficult to secure color reproducibility for a long time because the luminance change characteristics and driving conditions of the three kinds of light emitting materials are different. Left unresolved.
[0004]
Even with a method of transmitting and separating three primary colors by using a color filter for a backlight that emits white light, there still remains the problem of increasing the efficiency of the backlight.
In the color conversion method, in which only the separated phosphors absorb the light and each phosphor emits multicolored fluorescent light, an organic EL display with higher definition and brightness is adopted by adopting a top emission method using a TFT drive method. Has the potential to provide
[0005]
The color display devices disclosed in JP-A-11-251059 and JP-A-2000-77191 are examples of such a system.
FIG. 2 is a schematic cross-sectional view showing the structure of an organic EL display according to the related art (in the case of an active matrix drive system).
A TFT 2 (thin film transistor: hereinafter referred to as TFT), an anode 3, an organic EL light emitting layer 4, and a cathode 5 are formed on a substrate 1. Subsequently, a color filter 12 and a black mask 13 are formed on the transparent substrate 11. Next, a sealing agent 31 is formed around the substrate 1 using, for example, a room temperature-curable two-component epoxy adhesive, and is bonded to the transparent substrate 11. At this time, an internal space 32 is formed between the two substrates. The sealing layer 31 requires a considerably long curing time of 24 hours at room temperature. When the alignment of the organic EL light emitting layer and the color filter is performed, it is necessary to fix the organic layer during the room temperature curing so that no displacement occurs. was there.
[0006]
An important problem in practical use in a color display using a color filter as shown in FIG. 2 is that the organic EL element has a long-term stability including color reproducibility while having a fine color display function. In addition, it has a structure and a sealing method that can be manufactured in a short time.
[0007]
[Problems to be solved by the invention]
However, in such an organic EL element, precise alignment between the organic EL light emitting layer 4 and the color filter 12 is required. Until the alignment is completed, the adhesive used for the sealing layer 31 may have a change in viscosity or a change in viscosity. On the other hand, it is required that the alignment can be adjusted freely without causing a change in properties such as gelation, and at the time of completion of the alignment from the viewpoint of productivity, it is required to have the opposite curing characteristics to complete the curing early.
In addition, there is a problem that light emitted from the organic EL light emitting layer 4 is reflected at an air layer interface having a significantly different refractive index due to the influence of the internal space 32 formed between the two substrates.
[0008]
The present invention has been made in view of the above-described drawbacks, and has a sealing method capable of performing accurate alignment between an organic EL light emitting layer and a color filter, and also allowing a curing method in a short time, and light from the organic EL light emitting layer. The present invention provides a sealing structure and a sealing method for an organic EL element capable of effectively transmitting light to a color filter without reflecting the same, preventing invasion of moisture and the like from the external environment, and maintaining stable light-emitting characteristics for a long period of time. It is in.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an organic EL display according to the present invention comprises:
An organic light emitting element formed by laminating a first electrode made of a conductive thin film material formed on a substrate, an organic EL light emitting layer, a second electrode made of a transparent conductive material, and a protective layer; and a transparent substrate An organic EL element in which a laminate having a color filter and a black mask formed in the above is sealed and joined by aligning the position of the organic EL light emitting layer and the color filter.
An acrylic adhesive having an ultraviolet curing function and a room temperature curing function is used as a sealant used between two substrates to be sealed and joined.
[0010]
Here, the refractive index of the acrylic adhesive is preferably 1.2 to 2.5.
In the present invention, the use of the above two adhesives having a curing function enables accurate alignment of the organic EL light emitting layer and the color filter in the outer peripheral portion of the sealant, and also has a function of performing ultraviolet curing in a short time. Granted.
The inside of the sealing layer is provided with a function of transmitting light from the organic EL light-emitting layer to the color filter and having a high refractive index, and a function of curing at room temperature because ultraviolet light cannot be cured.
[0011]
Japanese Patent Application Laid-Open No. 2001-237066 discloses that there are a case where an ultraviolet-curable resin is used as an adhesive and a case where a room-temperature-curable two-liquid mixed resin is used as an adhesive. However, this disclosure discloses the use of one of the two types of resins, and does not suggest the use of an adhesive having two types of functions as in the present invention. The present invention is characterized by using an acrylic adhesive having both an ultraviolet curing function and a room temperature curing function.
[0012]
The reason for this is that, in order to perform the alignment and sealing of the two substrates, the entire surface is adhered with one adhesive, and then the resin curing of the outer peripheral portion after the completion of the alignment is completed in a short time, so that the position is reduced. It is difficult to irradiate ultraviolet rays to the resin (adhesive) inside the device using the ultraviolet curing function to prevent the displacement. Therefore, the room temperature curing function is used to perform both alignment and sealing. Is to complete.
[0013]
In the present invention, the organic EL display may be driven by an active matrix or may be driven by a passive matrix. When the active matrix drive is performed, for example, the anode on the lower side (substrate side) may be divided for each light emitting unit and connected to the source of a TFT (thin film transistor) provided on the substrate. At this time, the cathode of the upper electrode (opposite the substrate) can be a uniform electrode. Here, a configuration may be adopted in which the electrode on the substrate side is used as the cathode and the electrode on the opposite side to the anode is used as the anode, so that connection to the TFT may be established. On the other hand, when passive matrix driving is performed, a configuration can be adopted in which the lower electrode (substrate side) and the upper electrode (opposite substrate side) are line patterns extending in directions orthogonal to each other. In the case of active matrix driving, the substrate itself may be a TFT substrate on which driving TFTs are already formed. In the case of forming a passive matrix driving element, a glass substrate or a plastic substrate can be used.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
The organic EL display of the present invention will be described with reference to FIG.
In addition, the materials of each part constituting the organic EL element will be described below.
1: TFTs are arranged in a matrix on a substrate, a thin film transistor (TFT), and an insulating substrate made of anode glass, plastic, or the like, or a substrate formed by forming an insulating thin film on a semiconductive or conductive substrate. The source electrode is connected to the anode, which is the first electrode corresponding to.
[0015]
The TFT is a bottom gate type in which a gate electrode is provided below a gate insulating film, and has a structure using a polycrystalline silicon film as an active layer.
The anode is formed on the flattening insulating film formed on the TFT. In a normal organic EL display, ITO having a high work function is used as an anode material while transparent, and in the case of top emission, a metal electrode (Al, Ag, Mo, W) having a high reflectance is used under the ITO.
2: A TFT electrode substrate on which an organic light emitting element TFT and an anode are pattern-formed, an organic EL light emitting layer, and a cathode as a second electrode. That is, in the case of the color conversion method, light in the near ultraviolet to visible region emitted from the organic light emitting element, preferably light in the blue to blue-green region is emitted from the color filter layer alone or the color filter layer and the fluorescent color conversion layer or the color filter layer. And a fluorescent color conversion layer. The organic light emitting device has a structure in which an organic EL light emitting layer is sandwiched between a pair of electrodes, and a hole injection layer or an electron injection layer is interposed as necessary. Specifically, those having the following layer configurations are employed. Here, an example in which the first electrode on the substrate side is an anode is described, but it is a matter of course that the substrate side may be a cathode.
(1) anode / organic light emitting layer / cathode (2) anode / hole injection layer / organic EL light emitting layer / cathode (3) anode / organic EL light emitting layer / electron injection layer / cathode (4) anode / hole injection layer / Organic EL light emitting layer / electron injection layer / cathode (5) anode / hole injection layer / hole transport layer / organic EL light emitting layer / electron injection layer / cathode In the top emission color conversion method of the present embodiment, the above layers In the configuration, the cathode needs to be transparent in the wavelength range of light emitted from the organic EL light emitting layer, and emits light through the transparent cathode.
[0016]
Transparent cathodes include alkali metals such as lithium and sodium, alkaline earth metals such as potassium, calcium, magnesium and strontium, or electron-injecting metals such as fluorides thereof, and alloys and compounds with other metals. Is formed as an electron injection layer, and a transparent conductive film such as ITO or IZO is formed thereon.
[0017]
Known materials are used for the materials of each layer of the organic EL light emitting layer. For example, in order to obtain blue to blue-green light emission as the organic light emitting layer, for example, a fluorescent whitening agent such as a benzothiazole type, a benzimidazole type, a benzoxazole type, a metal chelated oxonium compound, a styrylbenzene type compound, an aromatic compound Dimethylidin compounds are preferably used.
3: Color conversion layer 1) Organic fluorescent dye In the present invention, the organic fluorescent dye absorbs light in the near-ultraviolet region or visible region, particularly, light in the blue or blue-green region emitted from a light-emitting element, and emits different visible light. As long as it emits, at least one type of fluorescent dye that emits at least red light fluorescence is used, and may be combined with at least one type of fluorescent dye that emits green light fluorescence. In other words, it is easy to obtain an organic EL light emitting element that emits light in the blue or blue-green region. , The output light becomes extremely dark.
[0018]
Therefore, the light in the red region can be output with a sufficient intensity by converting the light from the element into the light in the red region by the fluorescent dye. On the other hand, light in the green region may be converted into light in the green region by another organic fluorescent dye and output as in the case of light in the red region, or light emitted from the device may emit green light. If the region contains sufficient light, the light from the device may simply be output through a green filter. On the other hand, with respect to light in the blue region, it is also possible to output light from the organic light emitting element through a simple blue filter.
[0019]
Examples of the fluorescent dye that absorbs light in the blue to blue-green region emitted from the illuminant and emits fluorescence in the red region include rhodamine B, rhodamine 6G, rhodamine 3B, rhodamine 101, rhodamine 110, sulforhodamine, basic violet 11, Rhodamine dyes such as Basic Red 2, cyanine dyes, pyridine dyes such as 1-ethyl-2- [4- (p-dimethylaminophenyl) -13-butadienyl] -pyridium-perchlorate (pyridine 1), or Oxazine dyes and the like can be mentioned. Furthermore, various dyes (direct dyes, acid dyes, basic dyes, disperse dyes, etc.) can also be used as long as they have fluorescence.
[0020]
Examples of the fluorescent dye that absorbs light in the blue to blue-green region emitted from the luminous body and emits fluorescence in the green region include 3- (2′-benzothiazolyl) -7-diethylaminocoumarin (coumarin 6) and 3- (2 '-Benzimidazolyl) -7-N, N-diethylaminocoumarin (coumarin 7), 3- (2'-N-methylbenzimidazolyl) -7-N, N-diethylaminocoumarin (coumarin 30), 2,3,5,6 Coumarin-based dyes such as -1H, 4H-tetrahydro-8-trifluoromethylquinolidine (9,9a, 1-gh) coumarin (coumarin 153) or coumarin dye-based dyes such as Basic Yellow 51 and Solvent Yellow 11 And naphthalimide dyes such as Solvent Yellow 116. Furthermore, various dyes (direct dyes, acid dyes, basic dyes, disperse dyes, etc.) can also be used as long as they have fluorescence.
[0021]
Incidentally, the organic fluorescent dye used in the present invention, polymethacrylic acid ester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer resin, alkyd resin, aromatic sulfonamide resin, urea resin, melamine resin, benzoguanamine resin and these resins It may be kneaded in advance into a mixture or the like to form a pigment, thereby obtaining an organic fluorescent pigment. These organic fluorescent dyes and organic fluorescent faces may be used alone or in combination of two or more in order to adjust the hue of fluorescence. The organic fluorescent dye used in the present invention is contained in an amount of 0.01 to 5% by weight, more preferably 0.1 to 2% by weight, based on the weight of the fluorescent color conversion film. If the content of the organic fluorescent dye is less than 0.01% by weight, sufficient wavelength conversion cannot be performed, or if the content exceeds 5%, color conversion due to the effect of concentration quenching and the like. This results in reduced efficiency.
2) Matrix resin Next, the matrix resin used for the fluorescent color conversion film of the present invention is obtained by subjecting a photo-curable or photo-thermo-curable resin to light and / or heat treatment to generate radical species and ionic species. It is insoluble and infusible by polymerization or crosslinking. Further, it is not necessary to be soluble in an organic solvent or an alkali solution before curing, which is essential when performing patterning by a conventional photolithography method.
[0022]
Specifically, a photo-curable or photo-heat-curable resin is defined as (1) a composition film comprising an acrylic polyfunctional monomer or oligomer having a plurality of acroyl groups or methacryloyl groups, and a photo- or heat-polymerization initiator. (2) a composition comprising polyvinyl cinnamate and a sensitizer cross-linked by dimerization with light or heat, and (3) a chain. (4) a composition film comprising a monomer having an epoxy group and a photo-acid generator, wherein nitrene is generated by light or heat treatment and crosslinked with an olefin; To generate an acid (cation) for polymerization. In particular, the photo-curable or photo-heat-curable resin (1) can be patterned with high definition and is preferable in terms of reliability such as solvent resistance and heat resistance.
3) Shape As the shape of the color conversion layer, a stripe pattern separated for each color is well known, but in order to improve the effect of the visible light reflecting wall, not only for each color but also for each subpixel. It is more preferable to have a modified structure. Further, by making the peripheral portion of the color conversion layer have a forward tapered shape, the extraction efficiency is further improved. However, if the angle 順 of the forward taper is too small, the light reflected by the reflection layer travels in the horizontal direction and cannot be taken out. Therefore, an angle of about 45 ° is preferable. When sufficient color purity cannot be obtained by using only the layer, a laminate of the color filter layer and the color conversion layer is used. The thickness of the color filter layer is preferably from 1 to 1.5 μm.
4: Passivation layer (protective layer)
The passivation layer has high transparency in the visible region (transmittance of 50% or more in the range of 400 to 700 nm), Tg of 100 ° C. or more, surface hardness of 2H or more in pencil hardness, and a smooth coating film on the color conversion layer. Any material can be used as long as it does not deteriorate the functions of the color conversion layers 2 to 4. For example, an imide-modified silicone resin (Japanese Patent Laid-Open No. 5-134112), an inorganic metal compound (TiO, AL ₂ O ₃₎ SiO ₂ etc.) dispersed in acrylic, polyimide, silicone resin and the like (JP-A-5-119306, etc.), and an epoxy-modified acrylate resin as an ultraviolet-curable resin (JP-A-7-48424). Resin having a reactive vinyl group of acrylate monomer / oligomer / polymer, resist resin (JP-A-6-300910, etc.), sol-gel method Photocurable resins such as inorganic compounds (described in Monthly Display 1997, Vol. 3, No. 7, JP-A-8-27934, etc.), fluorine-based resins (JP-A-5-36475, etc.) and / or thermosetting resins Mold resin.
[0023]
There is no particular limitation on the method of forming the passivation layer. For example, conventional methods such as a dry method (sputtering method, vapor deposition method, CVD method, etc.) and a wet method (spin coat method, roll coat method, cast method, etc.) are used. It can be formed by the method described below.
In addition, the passivation layer has an electrical insulating property, a barrier property against moisture and low molecular components, a high transparency in a visible region (a transmittance of 50% or more in a range of 400 to 700 nm), and preferably 2H or more. A material having a film hardness may be used.
[0024]
For example, inorganic oxides such as SiOx, SiNx, SiNxOy, AlOx, TiOx, TaOx, ZnOx, and inorganic nitrides can be used. The method for forming the passivation layer is not particularly limited, and the passivation layer can be formed by a conventional method such as a sputtering method, a CVD method, a vacuum evaporation method, and a dipping method. The above-mentioned passivation layer may be a single layer, but the effect is greater in the case where a plurality of layers are stacked. The thickness of the laminated passivation layer is preferably 1 to 10 μm.
5: Sealant As the sealant, an adhesive having both functions of an ultraviolet curing function and a room temperature curing function is used.
[0025]
This adhesive is achieved, for example, by adding a photocuring catalyst and providing an ultraviolet curing function based on an acrylic two-component adhesive. The ultraviolet curing function is designed so that curing is completed at an irradiation amount of 3000 to 10000 mJ / cm ² at a wavelength of 365 nm with respect to irradiation conditions of ultraviolet light. The irradiation amount can be achieved in detail by irradiating with an illuminance of 100 mW / cm ² for 30 to 100 seconds.
[0026]
Regarding the illuminance, stable curing can be obtained if the illuminance is 400 mW / cm ² or less and 50 mW / cm ² or more. At 400 mW / cm ² or more, the reaction is severe and an exothermic reaction occurs. Further, at 50 mW / cm ² or less, no reaction occurs. Good illuminance is around 100 mW / cm ² .
As a specific adhesive, a UV-curable two-component mixed acrylic adhesive, trade name DX-1013U manufactured by Toyo Ink Co., Ltd. can be used.
[0027]
As a function of curing the adhesive at room temperature, the curing is completed in about 40 to 50 minutes at room temperature (20 to 28 ° C.) after mixing.
(Example 1)
As shown in FIG. 1, a TFT 2, an anode 3, an organic EL light emitting layer 4, a cathode 5, and a protective layer 6 are sequentially formed on a glass substrate 1. Next, a color filter 12 and a black mask 13 are sequentially formed on the transparent glass substrate 11. The two substrates thus formed are subjected to the following steps in a dry nitrogen atmosphere (both oxygen and moisture concentrations are 1 ppm or less) in a glove box.
[0028]
A two-component mixed type UV curable acrylic adhesive having a room temperature curing function (trade name: DX-1013U, manufactured by Toyo Ink Co., Ltd.) is measured / mixed / defoamed at a volume ratio of 1: 1 and then dispensed with an organic EL light emitting layer side. After the required amount is applied onto the glass substrate 1, the transparent glass substrate 11 on the color filter side is bonded. In this case, the distance between the two substrates to be bonded is set to be 5 μm to 50 μm, and the necessary amount of the sealant can be calculated from the area.
[0029]
Thereafter, alignment is performed in correspondence with the organic EL light emitting layer 4 and the color filter 12, and curing is performed by irradiating the outer periphery of the sealant with an irradiance of 100 mW / cm ² for 30 seconds as an ultraviolet curing condition.
For the inside of the sealant which cannot be cured by ultraviolet light, the curing is completed in about 40 to 50 minutes at room temperature.
[0030]
The refractive index of the two-component mixed type UV curable acrylic adhesive (trade name: DX-1013U, manufactured by Toyo Ink Co., Ltd.) having a room temperature curing function is 1.43, and light is not reflected, and light from the organic EL light emitting layer 4 is not generated. Can be transmitted to the color filter 12. In addition, it prevents an intrusion of moisture from the external environment and constitutes an organic EL element having long-term reliability.
In the case of passive matrix driving, a step of aligning the intersection of the line pattern of the two electrodes with the color conversion filter layer is performed.
[0031]
【The invention's effect】
As described above, according to the present invention, an organic layer formed by stacking a first electrode made of a conductive thin film material, an organic EL light emitting layer, a second electrode made of a transparent conductive material, and a protective layer. In an organic EL display in which a light emitting element, a laminate having a color filter and a black mask formed on a transparent substrate are sealed and joined by aligning the position of the organic EL light emitting layer and the color filter, two sheets that are sealed and joined As a sealant used between the substrates, a two-liquid mixed type ultraviolet curable acrylic adhesive having a room temperature curing function was used.
[0032]
By using the adhesive having the above two curing functions, a function of accurately aligning the organic EL light emitting layer and the color filter at the outer peripheral portion of the sealant and performing ultraviolet curing in a short time is provided.
The inside of the sealing layer is provided with a function of transmitting light from the organic EL light emitting layer to the color filter and having a high refractive index, and a function of curing at room temperature because ultraviolet light cannot be cured.
[0033]
By using a sealing agent having a refractive index of 1.3 to 2.5 inside the sealing layer, a structure is achieved in which reflection of light from the organic EL light emitting layer is prevented and the light is effectively transmitted to the color filter. At the same time, it has become possible to prevent entry of moisture and the like from the external environment and maintain stable light emission characteristics for a long period of time.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a structure of an organic EL display of the present invention.
FIG. 2 is a schematic sectional view showing the structure of a conventional organic EL display.
[Explanation of symbols]
1 substrate 2 TFT
3 anode 4 organic EL light emitting layer 5 cathode 6 protective layer 11 transparent substrate 12 color filter 13 black mask 21 outer peripheral sealing layer 22 inner sealing layer 31 sealing layer 32 inner space

Claims (2)

An organic light emitting element formed by laminating a first electrode made of a conductive thin film material formed on a substrate, an organic EL light emitting layer, a second electrode made of a transparent conductive material, and a protective layer; and a transparent substrate An organic EL element in which a laminate having a color filter and a black mask formed in the above is sealed and joined by aligning the position of the organic EL light emitting layer and the color filter.
An organic EL display using an acrylic adhesive having an ultraviolet curing function and a room temperature curing function as a sealing agent used between two substrates to be sealed and joined. An organic EL display comprising an acrylic adhesive having a refractive index of 1.2 to 2.5 and having a UV curing function and a room temperature curing function as the sealant according to claim 1.

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