KR102112773B1 - Pressure sensitive adheisve and flexible organic light emitting diode display device - Google Patents

Abstract

The present application relates to a pressure-sensitive adhesive and a flexible organic light-emitting diode display device including the same, and the pressure-sensitive adhesive of the present application can increase the light extraction efficiency at the same time as thinning the structure of the flexible organic light-emitting diode display and simplifying the structure.

Description

Pressure sensitive adheisve and flexible organic light emitting diode display device

The present application relates to a pressure-sensitive adhesive and a flexible organic light emitting diode display device including the same.

In recent years, the display field for visually expressing electrical information signals has been rapidly developed in the era of full-scale informatization, and a flat panel display device having excellent performance of thinning, lightening, and low power consumption has been developed and used.

Here, among flat panel display devices, liquid crystal display devices (LCDs) and organic light emitting diode (OLED) display devices have been widely used.

In particular, the organic light emitting diode display device has an advantage that it is possible to realize a thin and light weight compared to a liquid crystal display device requiring a separate light source backlight unit by using a self-light emitting device.

In addition, the organic light emitting diode display device has a relatively good viewing angle and contrast ratio compared to a liquid crystal display device, has a fast response speed, consumes low power consumption, and is capable of driving DC low voltage, so it is easy to manufacture and design a driving circuit. Have In addition, since the internal component is solid, it is resistant to external shock and has a wide range of operating temperatures.

Organic light-emitting diode display devices having these advantages are being researched to be applied in a wider use area such as a desktop computer monitor and a wall-mounted television as well as a portable computer, and in particular, research is being conducted to enlarge the area to have a larger display area. It is actively progressing.

The organic light emitting diode display device includes a display panel including an organic light emitting diode for self-emission and an organic light emitting diode composed of first and second electrodes for emitting the organic light emitting layer.

In the organic light emitting diode display, when voltage is applied to the first electrode and the second electrode, electrons and holes injected from the first electrode and the second electrode are combined inside the organic light emitting layer to generate excitons. It uses the principle of emitting light as the exciton falls from the excited state to the ground state.

Recently, as interest in flexible display devices has increased, demand for a technology using a flexible substrate in an organic light emitting diode display device has increased. However, when a flexible substrate is applied to an organic light emitting diode display device, a difference in refractive index between the organic light emitting diode device and the flexible substrate and the adhesive causes total reflection that occurs when light passes through the material at a specific incident angle, thereby lowering the light efficiency of the device. There is a problem. In order to solve this problem, a technique for arranging a light extraction film inside or outside of an organic light emitting diode device is known, but since this technology requires a separate light extraction film to be manufactured and attached, the process is complicated and the thickness of the final device It has the disadvantage of thickening.

Republic of Korea Patent Publication No. 2015-0078333

The present application provides a flexible organic light-emitting diode display device including a pressure-sensitive adhesive capable of increasing light extraction efficiency and thinning of a flexible organic light-emitting diode display device and simplifying the structure.

This application relates to an adhesive. The pressure-sensitive adhesive of the present application may be used in a flexible organic light emitting diode display device. Exemplary adhesives of the present application may include adhesive resins and inorganic nanoparticles. The inorganic nanoparticles may have a refractive index of 2.0 to 2.5 for light having a wavelength of 400 nm to 800 nm. The adhesive may have a transmittance of 70% or more.

Since the pressure-sensitive adhesive of the present application has a high transmittance and a high refractive index, it is possible to reduce the difference in refractive index between the organic light emitting diode device and the flexible substrate, thereby reducing total reflection occurring in the refractive index gap between each layer, thereby increasing light extraction efficiency. I can do it. In addition, since the present application is a technique of increasing the refractive index without lowering the transmittance of the pressure-sensitive adhesive instead of using a separate light extraction film for the organic light-emitting diode device, it is possible to increase the light extraction efficiency at the same time as the device is thinned and the structure is simplified. . Hereinafter, the pressure-sensitive adhesive of the present application will be described in detail.

In one example, an adhesive resin known to be used in a flexible organic light emitting diode display device may be used as the adhesive resin. Examples of the adhesive resin include acrylate resin, silicone resin, rubber resin, styrene resin, epoxy resin polyolefin resin, polyoxyalkylene resin, polyester resin, polyvinyl chloride resin, polycarbonate resin and polyamide resin. One or more selected from can be used. According to an embodiment of the present application, an acrylate resin may be used as the adhesive resin, and more specifically, butyl acrylate, isobornyl acrylate, phenoxyethyl acrylate, and 2 -Copolymers of 2-Hydroxyethyl acrylate can be used.

In one example, the inorganic nanoparticles may be present in a dispersed state in the adhesive resin. In the case where the inorganic nanoparticles are dispersed in the adhesive resin, since the refractive index can be improved without lowering the transmittance, total reflection between the substrates can be reduced.

The content ratio of the inorganic nanoparticles to the adhesive resin may be appropriately adjusted in consideration of the purpose of the present application. As the content of the inorganic nanoparticles increases, the transmittance of the adhesive tends to increase and haze decreases. That is, as the content of inorganic nanoparticles increases, the dispersibility of particles in the adhesive resin tends to increase. In one example, the inorganic nanoparticles may be included in a weight ratio of 10 parts by weight to 100 parts by weight based on 100 parts by weight of the adhesive resin. When the content ratio is satisfied, the light extraction efficiency of the pressure-sensitive adhesive can be effectively increased. When the content of the inorganic nanoparticles is too high, the transmittance of the pressure-sensitive adhesive may be reduced and light extraction efficiency may be reduced.

In one example, the inorganic nanoparticles can be high refractive index particles. As described above, the inorganic nanoparticles may have a refractive index of 2.0 to 2.5 for light having a wavelength of 400 nm to 800 nm. The inorganic nanoparticles can increase the refractive index of the pressure-sensitive adhesive, thereby reducing total reflection reduction, thereby improving light extraction efficiency.

The refractive index may be a value measured for light having a wavelength of about 400 nm to 800 nm, for example, about 632.8 nm, using a known refractive index measuring device, for example, a Prism Coupler SPA-4000 device, unless otherwise specified. have.

In one example, the particle diameter of the inorganic nanoparticles may be 1 nm or more to 50 nm or less. When the particle size of the inorganic nanoparticles satisfies the above range, dispersion stability can be secured in the adhesive resin to effectively increase light extraction efficiency.

In one example, a metal oxide may be used as the inorganic nanoparticle. Examples of the inorganic nanoparticles include silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), iron oxide (FeO ₃ ), zinc oxide (ZnO), One or more metals selected from the group consisting of magnesium oxide (MgO), zirconium oxide (ZrO ₂ ), cerium oxide (CeO ₂ ), lithium oxide (LiO ₂ ), silver oxide (AgO) and antimony oxide (Sb ₂ O ₃ ) Oxides can be used. According to an embodiment of the present application, zirconium oxide (ZrO ₂ ) may be used.

The thickness of the pressure-sensitive adhesive may be appropriately selected in consideration of the purpose of the present application. In one example, the thickness of the pressure-sensitive adhesive may be 15㎛ to 25㎛. When the thickness of the adhesive satisfies the above range, light extraction efficiency can be effectively increased. If the thickness of the pressure-sensitive adhesive is too thin, it is difficult to manufacture and the light scattering effect is reduced. If the thickness of the pressure-sensitive adhesive is too thick, the transmittance of the pressure-sensitive adhesive may be reduced.

The pressure-sensitive adhesive of the present application not only exhibits high refractive index and high transmittance, but may also exhibit an appropriate level of haze to cause light scattering.

In one example, the transmittance of the adhesive may be 70% or more, 80% or more, 85% or more, or 88% or more. In this specification, the transmittance may mean transmittance to light having a wavelength of 400 nm to 800 nm. As an example, in this specification, the transmittance may mean a transmittance for light having a wavelength of 400 nm to 800 nm, or an average transmittance for light having a wavelength of 400 nm to 800 nm. As described above, when the pressure-sensitive adhesive exhibits high transmittance, light efficiency can be further increased.

As described above, the haze of the pressure-sensitive adhesive may be 5% to 30%. Thus, when the pressure-sensitive adhesive exhibits haze in the above range, light extraction efficiency can be effectively increased due to an appropriate light scattering effect.

The present application also relates to a flexible organic light emitting diode display device. The exemplary display device of the present application may include the pressure-sensitive adhesive, a flexible substrate and an organic light emitting diode device.

1 exemplarily shows the display device of the first embodiment of the present application. According to FIG. 1, the pressure-sensitive adhesive 10 is present on one surface of the flexible substrate 20, and the organic light emitting diode device 30 can be disposed on the opposite side of the pressure-sensitive adhesive of the flexible substrate.

As the flexible substrate, a flexible substrate known to be used for a flexible display device can be used. As the flexible substrate, a substrate including at least one member selected from the group consisting of polyether sulfone, polyethylene naphthalate, polyethylene terephthalate, polycarbonate, and polyimide may be used.

The flexible substrate may have a refractive index of 1.45 to 1.75 for light having a wavelength of 400 nm to 800 nm. The pressure-sensitive adhesive of the present application may increase the light extraction efficiency by reducing total reflection by reducing a difference in refractive index from such a flexible substrate.

The organic light emitting diode device may include first and second electrodes disposed opposite to each other and an organic light emitting layer between the first and second electrodes. Hereinafter, an electrode adjacent to the flexible substrate is referred to as a first electrode for distinction, and an opposite electrode is referred to as a second electrode.

In one example, when the first electrode is used as the transparent electrode and the second electrode is used as the reflective electrode, a lower emission type device in which light generated from the organic light emitting layer is emitted toward the substrate may be implemented.

The organic light-emitting layer can be formed, for example, using various fluorescent or phosphorescent organic materials known in the art. As a material of the light emitting layer, tris (4-methyl-8-quinolinolate) aluminum (III) (tris (4-methyl-8-quinolinolate) aluminum (III)) (Alg3), 4-MAlq3 or Gaq3, etc. Alq series material, C-545T (C ₂₆ H ₂₆ N ₂ O ₂ S), DSA-amine, TBSA, BTP, PAP-NPA, Spiro-FPA, Ph ₃ Si (PhTDAOXD), PPCP (1,2,3) Cyclopenadiene derivatives such as, 4,5-pentaphenyl-1,3-cyclopentadiene), DPVBi (4,4'-bis (2,2'-diphenylyinyl) -1,1'-biphenyl), distyryl Benzene or derivatives thereof or DCJTB (4- (Dicyanomethylene) -2-tert-butyl-6- (1,1,7,7, -tetramethyljulolidyl-9-enyl) -4H-pyran), DDP, AAAP, NPAMLI,; Or Firpic, m-Firpic, N-Firpic, bon ₂ Ir (acac), (C ₆ ) ₂ Ir (acac), bt ₂ Ir (acac), dp ₂ Ir (acac), bzq ₂ Ir (acac), bo _{2 Ir (acac), F 2} Ir (bpy), F 2 Ir (acac), op 2 Ir (acac), ppy 2 Ir (acac), tpy 2 Ir (acac), FIrppy (fac-tris [2- ( 4,5'-difluorophenyl) pyridine-C'2, N] iridium (III)) or Btp ₂ Ir (acac) (bis (2- (2'-benzo [4,5-a] thienyl) pyridinato-N, C3 ') phosphorescent materials such as iridium (acetylactonate)) and the like may be exemplified, but is not limited thereto. The light emitting layer includes the material as a host, and also includes perylene, distyrylbiphenyl, DPT, quinacridone, rubrene, BTX, ABTX, or DCJTB. It may have a host-dopant system included as a dopant.

The organic light emitting diode device may be formed of various structures that further include various other functional layers known in the art as long as it includes an organic light emitting layer, and the functional layer includes an electron injection layer, a hole blocking layer, an electron transport layer, A hole transport layer and a hole injection layer may be exemplified.

In one example, a pixel driving layer may be formed on a flexible substrate, and an organic light emitting diode device may be formed on the pixel driving layer. The pixel driving layer may include, for example, a driving thin film transistor, a switching thin film transistor, and a color filter layer.

The display device may further include a sealing structure as needed. The encapsulation structure may be a protective structure that prevents foreign substances such as moisture or oxygen from entering the organic light emitting layer of the organic light emitting diode device. The encapsulation structure may be, for example, a can such as a glass can or a metal can, or a film covering the entire surface of the organic light emitting layer.

The display device may further include a barrier layer. As used herein, the term “barrier layer” may mean a layer having a function of preventing oxygen, moisture, nitrogen oxides, sulfur oxides, or ozone permeation in the atmosphere. The barrier layer is not particularly limited as long as it has the above function, and may be appropriately selected depending on the intended use.

The barrier layer may be present between the organic light emitting diode device and the flexible substrate, or may be on the opposite side of the flexible substrate of the pressure-sensitive adhesive. When present between the organic light emitting diode device and the flexible substrate, it may be referred to as an inner barrier layer, and when present on the opposite side of the flexible substrate of the pressure-sensitive adhesive, it may be referred to as an outer barrier layer.

2 exemplarily shows the display device of the second embodiment of the present application. As shown in FIG. 2, the display device may sequentially include the adhesive 10, the flexible substrate 20, the inner barrier layer 40, and the organic light emitting diode device 30. 3 exemplarily shows the display device of the third embodiment of the present application. As shown in FIG. 3, the display device may sequentially include an outer barrier layer 50, an adhesive 10, a flexible substrate 20, an inner barrier layer 40, and an organic light emitting diode device 30.

The material of the barrier layer may be a material having a function of preventing substances that promote device deterioration such as moisture and oxygen from entering the device. Specific examples of the barrier layer include specific examples of the barrier layer include metals such as In, Sn, Pb, Au, Cu, Ag, Al, Ti and Ni; TiO, TiO ₂ , Ti ₃ O _{3 ,} Al ₂ O ₃ , MgO, SiO, SiO ₂ , GeO, NiO, CaO, BaO, Fe ₂ O ₃ , Y2O ₃ , ZrO ₂ , Nb ₂ O ₃ and, CeO ₂ and Metal oxides such as; Metal nitrides such as SiN; Metal oxynitrides such as SiON; Metal fluorides such as MgF ₂ , LiF, AlF ₃ and CaF ₂ ; Polyethylene, polypropylene, polymethylmethacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, or chlorotrifluoroethylene and dichlorodifluoroethylene Copolymer; A copolymer obtained by copolymerization of a comonomer mixture containing at least one comonomer and tetrafluoroethylene; A fluorine-containing copolymer having a cyclic structure in the copolymer main chain; Absorbent material having an absorption rate of 1% or more; And a moisture-proof material having an absorption coefficient of 0.1% or less.

In one example, the barrier layer may be a single-layer structure or a multi-layer structure. For example, the barrier layer, Al ₂ O ₃ layer and The TiO ₂ layer may be a multilayer structure sequentially stacked.

When the pressure-sensitive adhesive of the present application is applied to a flexible organic light-emitting diode display device, other components or a method of configuring the device are not particularly limited, and any materials or methods known in the art as long as the pressure-sensitive adhesive is applied are all Can be employed.

The present application provides a flexible organic light emitting diode display device including a pressure-sensitive adhesive capable of increasing light extraction efficiency and thinning the structure of a flexible organic light emitting diode display device and simplifying the structure.

1 is a schematic diagram of a display device according to a first embodiment of the present application.
2 is a schematic diagram of a display device according to a second embodiment of the present application.
3 is a schematic diagram of a display device according to a third embodiment of the present application.

Hereinafter, the present application will be described in more detail through examples according to the present application and comparative examples not according to the present application, but the scope of the present application is not limited by the examples presented below.

Measurement example  1. Refractive index measurement

Using a refractive index measuring equipment Prism Coupler SPA-4000, the refractive index of light having a wavelength of 632.8 nm was measured.

Measurement example 2. Transmittance measurement

The transmittance of light having a wavelength of 400 nm to 800 nm was measured using a Nippon denshoku 400 device.

Measurement example  3 Haze  Measure

Haze was measured using a Nippon denshoku 400 instrument.

Evaluation example  1 Quantum efficiency evaluation

Quantum efficiency was measured using OTSUKA's integrating hemisphere device.

Example 1

Preparation of adhesive

ZrO ₂ (refractive index: 2.15) dispersion (ZA14, NIKKISO) as an adhesive resin in butyl acrylate (BA), isobornyl acrylate (IBOA), phenoxyethyl acrylate (PEA) and 2-hydroxyethyl acrylate Mix in coalescence. It was sufficiently dispersed in the adhesive resin by stirring and sonication for one day. The prepared adhesive resin solution was coated on a release-treated polyethylene terephthalate (PET) film by a bar coating method, dried in an oven at 120 ° C. for 2 minutes, and then immediately laminated a release PET film to prepare an adhesive. The thickness of the prepared adhesive was about 20 μm, and the content of ZrO ₂ particles in the adhesive was 25 parts by weight compared to 100 parts by weight of the adhesive resin.

Flexible  Manufacturing of organic light emitting diode display device

The manufactured adhesive 10, a plastic substrate 20 having a refractive index of 1.75 for light having a wavelength of 400 nm to 800 nm, and a known organic light emitting diode device 30 are manufactured in a structure as shown in FIG. 1. Did.

Example  2

When manufacturing the adhesive, a display device was manufactured in the same manner as in Example 1, except that the content of the inorganic nanoparticles was changed to 50 parts by weight compared to 100 parts by weight of the adhesive resin.

Example  3

When manufacturing the adhesive, a display device was manufactured in the same manner as in Example 1, except that the content of the inorganic nanoparticles was changed to 80 parts by weight compared to 100 parts by weight of the adhesive resin.

Comparative example  One

When manufacturing the adhesive, a display device was manufactured in the same manner as in Example 1, except that inorganic nanoparticles were not added.

For Examples 1 to 3 and Comparative Example 1, the refractive index, transmittance, and haze of the adhesive were measured, and the quantum efficiency of the display device was evaluated, and the results are shown in Table 1 below.

Example 1 Example 2 Example 3 Comparative Example 1 adhesive Refractive index 1.58 1.65 1.73 1.47 Transmittance (%) 79.96 83.45 84.82 91.65 Haze (%) 26.14 12.37 9.79 0.42 Quantum efficiency (%) 53.9 54.5 54.7 52.0

10; adhesive
20: flexible substrate
30: organic light emitting diode
40: inner barrier layer
50: outer barrier layer

Claims (16)

An adhesive applied to a flexible organic light emitting diode display device, comprising an adhesive resin and inorganic nanoparticles having a refractive index of 2.0 to 2.5 for light having a wavelength of 400 nm to 800 nm, a particle diameter of 1 nm to 50 nm, and a transmittance 70% or more adhesive.
delete The adhesive of claim 1, wherein the inorganic nanoparticles are present in a dispersed state in the adhesive resin.
The method of claim 1, wherein the adhesive resin is an acrylate-based resin, silicone-based resin, rubber-based resin, styrene-based resin, epoxy-based resin polyolefin-based resin, polyoxyalkylene-based resin, polyester-based resin, polyvinyl chloride-based resin, poly An adhesive comprising at least one member selected from the group consisting of carbonate-based resins and polyamide-based resins.
The adhesive of claim 1, wherein the inorganic nanoparticles are contained in an amount of 10 parts by weight to 100 parts by weight based on 100 parts by weight of the adhesive resin.
The pressure-sensitive adhesive according to claim 1, wherein the haze of the pressure-sensitive adhesive is 5% to 30%.
delete The method of claim 1, wherein the inorganic nanoparticles are silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), iron oxide (FeO ₃ ), zinc oxide (ZnO) ), Magnesium oxide (MgO), zirconium oxide (ZrO ₂ ), cerium oxide (CeO ₂ ), lithium oxide (LiO ₂ ), silver oxide (AgO), and antimony oxide (Sb ₂ O ₃ ) The adhesive containing the above metal oxide.
The pressure-sensitive adhesive of claim 1, wherein the pressure-sensitive adhesive has a thickness of 15 μm to 25 μm.
A flexible organic light emitting diode display device comprising the adhesive of claim 1, a flexible substrate and an organic light emitting diode device.
The flexible organic light emitting diode display device of claim 10, wherein the pressure sensitive adhesive is on one side of the flexible substrate, and the organic light emitting diode device is disposed on the opposite side of the pressure sensitive adhesive of the flexible substrate.
The display device of claim 10, wherein the flexible substrate comprises at least one member selected from the group consisting of polyether sulfone, polyethylene naphthalate, polyethylene terephthalate, polycarbonate, and polyimide.
The display device of claim 10, wherein the flexible substrate has a refractive index of 1.45 to 1.75 for light having a wavelength of 400 nm to 800 nm.
The display device of claim 10, wherein the organic light emitting diode device includes first and second electrodes disposed opposite to each other and an organic light emitting layer between the first and second electrodes.
The display device of claim 10, further comprising a barrier layer.
16. The display device according to claim 15, wherein the barrier layer is present between the organic light emitting diode element and the flexible substrate or on the opposite side of the flexible substrate of the pressure-sensitive adhesive.

Images