KR102340216B1 - Organic Light Emitting Diode Formed On Flexible Substrate Comprising Organic Light Scattering Materials - Google Patents

Abstract

In the present invention, an organic light emitting diode (OLED) in which a lower substrate, a transparent electrode, an organic thin film layer and a metal electrode are sequentially stacked, wherein the lower substrate comprises a flexible substrate including an organic light scattering material. to provide. The organic light emitting diode according to the present invention has excellent light efficiency and can avoid damage to the transparent electrode layer or the organic thin film layer (light emitting layer) during manufacturing, and also, when bending stress is repeatedly applied to the flexible organic light emitting diode, Cracks can be prevented.

Description

Organic Light Emitting Diode Formed On Flexible Substrate Comprising Organic Light Scattering Materials

The present invention relates to an organic light emitting diode, and more particularly, the lower substrate is formed of a flexible substrate containing an organic light scattering material, so that it is possible to avoid damage to the transparent electrode layer or the organic thin film layer (light emitting layer) during manufacturing while having excellent light efficiency. Also, it relates to an organic light emitting diode capable of preventing a crack of a substrate that occurs when a bending stress is repeatedly applied to the flexible organic light emitting diode.

The organic light emitting device has a typical layered configuration that sequentially includes a substrate, a first electrode layer, an organic layer including a light emitting layer, and a second electrode layer. In the structure of the organic light emitting device, indium tin oxide (ITO), which is generally used as a transparent electrode layer, an organic layer, and a substrate, which are typically a glass substrate, have refractive indices of approximately 2.0, 1.8, and 1.5, respectively. Due to the relationship between these refractive indices, for example, light generated in the organic light emitting layer in a bottom emission type device is trapped by a total internal reflection phenomenon in the interface between the organic layer and the first electrode layer or in the substrate, etc., Only a very small amount of light is emitted.

As a method for solving this problem, techniques for inserting a light scattering layer as a separate layer between each layer forming the organic light emitting device have been tried.

For example, in KR2013-0108207A, in an organic light emitting device in which a base layer, a hole injection electrode layer, an organic laminate structure, and a hole or electron injection electrode layer are sequentially stacked, a scattering layer is separately provided on the hole or electron injection electrode layer An organic light emitting device formed and inserted is disclosed.

KR2015-0055296A discloses that in an OLED display including a substrate, a thin film transistor and an overcoat layer, a scattering layer is formed on the overcoat layer, and the scattering layer is formed of a material containing fluorine such as _{LiF, CsF, BeF 2} Disclosed is an OLED display device, characterized in that

In KR2015-0069871A, as a material for forming a scattering layer, a base material such as benzene, naphthalene, anthracene, and tetracene is substituted with at least one substituent selected from a benzoyl group, a carboxyl group, an aminophenoxyl group, a tricarbonate group, and a styryl group. compounds are disclosed.

On the other hand, KR2014-0073611A4 discloses a method of forming a separate scattering layer having a non-uniform surface on a substrate by depositing an organic material such as _{Alq 3 by a chemical vapor deposition method.}

In spite of advances in the above-described prior art, the increase in light efficiency is not sufficient, causing ancillary problems. In particular, when an inorganic material-based material with a high refractive index is used as the conventional scattering layer material, the inorganic-based high-strength scattering material causes damage to the organic light emitting diode itself during bonding in the process of attaching parts such as a functional film. There is a problem in that cracks easily occur due to the repetitive bending characteristics of the organic light emitting diode.

An object of the present invention is to avoid damage to a transparent electrode layer or an organic thin film layer (light emitting layer) during manufacturing while having excellent light efficiency, and also to avoid cracks in the substrate that occur when bending stress is repeatedly applied to a flexible organic light emitting diode ( To provide an organic light emitting diode capable of preventing cracks.

An organic light emitting diode according to the present invention for achieving the above object is an organic light emitting diode (OLED) in which a lower substrate, a transparent electrode, an organic thin film layer and a metal electrode are sequentially stacked, wherein the lower substrate is an organic light scattering material dispersed in a matrix resin. It is characterized in that it is formed of a flexible substrate.

The organic light scattering material is a polystyrene resin or a derivative thereof; Acrylic resin or its derivative; silicone resins or derivatives thereof; and at least one organic material bead selected from the group consisting of novolak resins or derivatives thereof. More preferably, it is a bead formed of polystyrene/polymethylmethacrylate copolymer resin.

It is preferable that the maximum particle diameter of the bead is 1 μm or less.

It is preferable to use the organic light scattering material having a water content of 100 ppm or less and a volatile content of 0.2% or less.

The matrix resin is preferably a thermosetting resin selected from the group consisting of an epoxy resin, a phenol resin, a silicone resin, a polyimide, a cyanate resin, a benzocyclobutene resin, and a polynorbornene resin. Particularly preferably, a thermosetting silicone resin is used.

The refractive index (n _{f ) of the organic light scattering material is 1.5 or more, and the ratio of the refractive index (n f} ) of the organic light scattering material to the refractive _{index (n r} ) of the matrix resin is _{n f} /n _r =1.0 to 1.5 in light of a wavelength of 400 nm It is preferable to be

The lower portion of the flexible substrate may be formed to have a hemispherical protrusion.

As the organic light emitting diode according to the present invention uses an organic material as a light scattering material for forming a flexible substrate, damage to the transparent electrode layer or the organic thin film layer (light emitting layer) can be reduced. In addition, it is possible to significantly reduce the crack (crack) of the substrate that occurs when bending stress is repeatedly applied to the flexible organic light emitting diode.

Additionally, in the case of the organic light emitting diode according to the present invention, as a flexible substrate containing a light scattering material is adopted as a substrate, light loss due to the substrate itself can be reduced, and as a result, the light extraction efficiency of the organic light emitting diode can be maximized.

1 is a schematic cross-sectional view of a first embodiment of an organic light emitting diode according to the present invention;
It is a schematic sectional drawing about 2nd Embodiment.

The organic light emitting diode according to the present invention is characterized in that a substrate including a flexible substrate in which an organic light scattering material is dispersed in a polymer matrix is used. The flexible substrate may be used alone as a substrate, or may be used as a multilayer substrate by laminating a flexible substrate on another flexible polymer film.

1 is a schematic cross-sectional view of a first embodiment of an organic light emitting diode according to the present invention. Referring to FIG. 1 , in the organic light emitting diode of the present invention, a lower substrate 200 , a transparent electrode 300 , an organic thin film layer 400 , and a metal electrode 500 are sequentially stacked. The first embodiment is characterized in that a flexible substrate in which an organic light scattering material is dispersed in a matrix resin is used as the lower substrate 200 .

In the present invention, the matrix resin forming the flexible substrate is preferably thermosetting. The resin for forming the light scattering layer and the resin used for the flexible substrate are often thermosetting resins. That is, in the process of compounding the light scattering layer with the flexible substrate, there are advantages such as using the existing process of the flexible substrate as it is, adding only the process for compounding, and not needing to change other processes. When the resin to be used is not thermosetting, the process tends to be complicated at the time of compounding with the flexible substrate.

As said thermosetting resin, an epoxy resin, a phenol resin, a siloxane resin, polyimide, cyanate resin, benzocyclobutene resin, polynorbornene etc. can be used, for example. However, it is not specifically limited to these.

Preferably, the siloxane-based resin is preferably a monomer, oligomer, polymer, etc. including at least one compound represented by the following formula (1):

[Formula 1]

.

.

In Formula 1, R ₁ to R ₆ are the same as or different from each other, and each independently hydrogen, an alkyl group, an alkenyl group, an aryl group, a glycidyl group, an isocyanate group, a hydroxyl group, a carboxyl group, a vinyl group, an acrylate group, meta may be selected from the group consisting of a acrylate group, an epoxide group, a cyclic ether group, a sulfide group, an acetal group, a lactone group, and an amide group; a, b, c and d are each independently a real number from 0 to 1, and (a+b+c+d) is 1.

The siloxane-based resin may be a monomer, an oligomer, or a polymer. Preferably, the weight average molecular weight of the siloxane-based resin may be 100 to 1,000,000, and most preferably 1,000 to 50,000 are used.

In the siloxane-based resin, one or more functional groups selected from the group consisting of an alkyl group, an aryl group, and an alkenyl group may be bonded to the silicon main chain. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a 1-methylethyl group, a butyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1,1-dimethylethyl group, a pentyl group, a 1-methylbutyl group, 1-ethylpropyl group, 2-methylbutyl group, 3-methylbutyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group , and a cycloalkyl group, but is not limited thereto. Specific examples of the aryl group include a phenyl group; naphthyl group; an alkylaryl group such as a tolyl group and a xylyl group; and an arylalkyl group such as a benzyl group or a phenethyl group, but is not limited thereto. The alkenyl group typically has 2 to 10 carbon atoms, and specific examples thereof include, but are not limited to, a vinyl group, an allyl group, a methacrylic group, a methylmethacryl group, and an acryl group.

In this invention, a hardening|curing agent is added as needed. For example, in general, the siloxane flexible substrate may be cured by adding a curing agent. Examples of the curing agent include an amine curing agent, an acid anhydride curing agent, and a platinum curing agent. Moreover, these hardening|curing agents may mutually use together.

In the above, the organic light scattering material contained in the flexible substrate, for example, polystyrene resin or a derivative thereof; Acrylic resin or its derivative; silicone resins or derivatives thereof; and at least one organic material bead selected from the group consisting of novolak resins or derivatives thereof. Most preferably, the light scattering material uses beads formed of polystyrene/polymethyl methacrylate copolymer resin.

Preferably, the organic light scattering material bead has a maximum particle size of 1 μm or less. Control of the maximum particle size is for improving the uniformity of the surface of the substrate including the same, and may be controlled by a known method such as, for example, a hair-cut process. On the other hand, it is preferable to use the organic light scattering material having a water content of 100 ppm or less and a volatile matter content of 0.2% or less.

Preferably, the refractive index (nf) of the organic light scattering material is 1.5 or more, and the ratio of the refractive index (nf) of the organic light scattering material and the refractive index (nr) of the matrix resin is nf / nr = 1.0 to 1.5 in light of a wavelength of 400 nm use.

On the other hand, the ratio of the matrix resin and the light scattering material in the composition for the flexible substrate is 1 - 30 parts by weight of the light scattering material with respect to 100 parts by weight of the matrix resin, preferably 5 to 20 parts by weight. When the proportion of the light scattering material is less than 1 part by weight, the light scattering effect is not sufficient, and when it exceeds 30 parts by weight, the surface protrusion is severe, and it is difficult to uniformly form the transparent electrode layer laminated thereon.

The said flexible base material is obtained by apply|coating and solidifying the composition which disperse|distributed the light scattering material to the matrix resin. This paste is produced by, for example, a method in which organic filler powder is added to a resin solution and mixed and dispersed, or a dispersion in which an organic filler is previously dispersed in a suitable solvent is prepared, and the dispersion is mixed with a resin solution by a let-down method, etc. do.

In addition, the method of dispersing the organic filler in the resin or solvent is not particularly limited, for example, ultrasonic dispersion, ball mill, roll mill, clarmix, homogenizer, bead mill, media disperser, etc. can be used, but in particular, It is preferable to use a ball mill, a roll mill, a homogenizer, and a bead mill from the point of dispersibility. When dispersing the organic filler, in order to improve the dispersibility, for example, surface treatment of the organic filler, addition of a dispersant, addition of a surfactant, addition of a solvent, etc. may be performed. Examples of the surface treatment of the organic filler include treatment with various coupling agents such as silane-based, titanium-based, and aluminum-based, fatty acid, phosphoric acid ester, etc., rosin treatment, acid treatment, and basic treatment. Nonionic, cationic and anionic surfactants, wetting agents such as polyhydric carboxylic acids, amphiphilic substances, and resins having a high steric hindrance substituent may be further added.

A method of molding the composition containing the flexible scattering material and the matrix resin into a sheet shape and processing it into a scattering sheet is not particularly limited, but a known method can be used. That is, a method of extruding a resin composition containing a scattering material using a T-die, etc. to form a sheet, a method of melting and coating on a substrate and cooling, a method of coating on a substrate in a mixed state with a solvent and drying, etc. can be heard In addition, when the matrix resin of the flexible substrate is a photocurable or thermosetting resin, the scattering sheet may be manufactured by coating the raw material composition in a sheet form on the substrate and curing it by applying a known method in that state.

The thickness of the flexible substrate produced by the above method is preferably 1 ~ 500㎛. If the scattering sheet is less than 1 µm, handling becomes difficult, and if it exceeds 500 µm, the thickness of the display device itself increases. More preferably, it is the range of 10-250 micrometers.

On the other hand, in the organic light emitting diode according to the present invention, the organic thin film layer and the metal electrode known in the art may be used for other configurations other than the transparent electrode and the substrate. For example, materials of the transparent electrode include CuI, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), FTO (fluorine doped tin oxide), AZO (aluminum doped zink oxide), GZO (gallium doped ZnO), ZnO , a conductive transparent material such as _{SnO 2} or In ₂ O _{3 may be exemplified.}

On the other hand, in the organic light emitting diode of the present invention, the organic thin film layer is a light emitting layer. The light emitting layer may include an Alq-based material such as Alq3, 4-MAlq3 or Gaq3; cyclophenadiene derivatives such as C-545T; It can be formed using various fluorescent or phosphorescent organic materials known in the art, such as. The thin film layer may be equipped with an additional layer structure such as an electron transport layer and a hole transport layer in addition to the light emitting layer if necessary.

In addition, as a material of the metal electrode, in general, it may be formed of a metal having a lower work function than that of the transparent electrode material. For example, a metal such as potassium, lithium, sodium, magnesium, lanthanum, cerium, calcium, strontium, barium, aluminum, molybdenum, gold, silver, indium, tin, zinc or zirconium, or two or more components selected from the above metals Alloys may be used.

The organic light-emitting diode characterized in that it comprises a flexible substrate comprising an organic light-scattering material according to the present invention can be applied in a modified embodiment. For example, FIG. 2 is a schematic cross-sectional view of a second embodiment of an organic light emitting diode according to the present invention. Referring to FIG. 2 , in the organic light emitting diode 20 of the second embodiment, a lower substrate 200 , a transparent electrode 300 , an organic thin film layer 400 , and a metal electrode 500 are sequentially stacked. The second embodiment is characterized in that a flexible substrate in which an organic light scattering material is dispersed in a polymer matrix is used alone as the substrate 210, but the lower portion of the substrate 210 is formed to have a hemispherical protrusion.

The hemispherical protrusion may be formed by curing the flexible substrate on a mold having the opposite shape or by pressing the mold on the semi-hardened or cured flexible substrate. When the substrate 210 made of a flexible substrate has a protrusion, it helps to improve the luminance as well as the effect by light scattering, as it helps the straightness of light. Specifically, if the refractive index of the light-scattering flexible substrate is 1.5, the refractive index of air is 1.0, and if there is a hemispherical protrusion, total reflection does not occur even if light is incident at 41.8 degrees or more, and most of the light wave is not formed. You can go out right away.

The first advantage of using a light scattering material of an organic material in manufacturing a lower substrate using a flexible substrate in the organic light emitting diode of the present invention is that other layers, for example, That is, damage to the transparent electrode layer or the organic thin film layer (light emitting layer) can be reduced.

The second advantage is that, in particular, when a bending stress is repeatedly applied to the flexible organic light emitting diode, cracks easily occurring in the substrate can be greatly reduced when an inorganic material is used as a light scattering material.

Additionally, in the case of the organic light emitting diode according to the present invention, there is an advantage that light extraction efficiency can be maximized. For example, in the case of a flexible substrate made of polyester, such as polyethylene terephthalate or polyethylene naphthalate, or polyimide, the refractive index of these materials is 1.5 or more, so the optical loss of the substrate itself using these materials is significant. In the case of the organic light emitting diode according to the present invention, as a flexible substrate containing a light scattering material is applied as a substrate, light loss due to the substrate itself can be reduced, and thus, light extraction efficiency can be maximized.

200, 210. Substrate 300. Transparent electrode
400.. Organic thin film layer 500.. Metal electrode

Claims (9)

In a matrix resin made of a thermosetting siloxane-based resin,
Polystyrene resin or its derivative(s) as an organic light-scattering material; Acrylic resin or its derivative; silicone resins or derivatives thereof; and a lower substrate in which at least one organic material bead selected from the group consisting of a novolac resin or a derivative thereof is dispersed, and the flexible substrate is used alone or in a multi-layered form;
A flexible organic light emitting diode in which a transparent electrode, an organic thin film layer and a metal electrode are sequentially stacked on the lower substrate. delete The flexible organic light emitting diode according to claim 1, wherein the organic material bead is a polystyrene/polymethyl methacrylate copolymer resin. The flexible organic light emitting diode according to claim 3, wherein the maximum particle diameter of the organic material bead is 1 μm or less. The flexible organic light emitting diode according to claim 1, wherein the organic light scattering material has a water content of 100 ppm or less and a volatile content of 0.2% or less. According to claim 1, wherein in the flexible substrate, the refractive index of the organic light scattering material (n _f ) is 1.5 or more, and the refractive index (n _f ) of the organic light scattering material and the refractive index (n _r ) of the matrix resin is n in light of a wavelength of 400 nm A flexible organic light emitting diode, characterized in that it satisfies _f /n _{r =1.0 to 1.5.} delete delete The flexible organic light emitting diode according to claim 1, wherein a lower portion of the lower substrate has a hemispherical protrusion.

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