A composition, encapsulation structure and OLED device for OLED thin film encapsulation

Abstract

The present application relates to the technical field of electronic packaging, and relates to a composition for OLED thin film packaging, a packaging structure and an OLED device. The composition comprises the following components in parts by weight: 5-15 parts of nano inorganic particles with a refractive index of not less than 1.7, 75-95 parts of a photocurable monomer, 1-10 parts of a photoinitiator, and 0.01-3 parts of an additive. The organic layer formed by the composition for OLED thin film packaging prepared by the present application has a lower curing shrinkage, a lower outgas value and a lower plasma etching resistance, and better meets the requirements that when the organic layer is combined with an inorganic layer to form an "inorganic-organic-inorganic" thin film packaging structure, the inorganic layer can withstand the plasma etching during formation of the inorganic layer, and the flatness of the inorganic layer is ensured, thereby maintaining a good packaging effect.

Description

Technical Field

[0001] This invention belongs to the field of electronic packaging technology, and relates to OLED thin film packaging, specifically to a composition, packaging structure and OLED device for OLED thin film packaging. Background Technology

[0002] OLED (Organic Light Emitting Diodes) is the most promising new display technology after LCD. It features active light emission, high contrast, ultra-thin and lightweight construction, and no viewing angle limitations. It also boasts good flexibility and a high color rendering index, making it widely applicable in television displays, computer displays, mobile phone screens, lighting, wearable devices, and instruments. Furthermore, OLED devices are compatible with flexible, lightweight, and durable plastic substrates, enabling truly flexible displays and making it the technology best suited to meet future display requirements. However, the materials and structure of OLED devices are sensitive to moisture and oxygen; contact with water and oxygen rapidly degrades the luminous efficiency, performance, stability, and lifespan of OLED devices.

[0003] Thin-film encapsulation structures are typically represented by a three-layer (inorganic / organic / inorganic) structure, which encapsulates OLED devices by stacking and depositing dense thin films on the substrate. Currently, the organic layer is mainly composed of UV-curable materials. While meeting the basic requirements of general encapsulation materials, it usually needs to achieve higher performance in terms of curing shrinkage, plasma etching rate, heat resistance, and toughness. Furthermore, during the preparation of the encapsulation film, the small molecules in the organic layer easily generate impurities, resulting in increased outgassing values. When there are many impurities remaining in the organic film, these residual impurities will be released during the inorganic layer evaporation process, leading to a decrease in the flatness of the upper inorganic layer and thus adversely affecting the protected device.

[0004] Currently, the refractive index of silicon nitride substrates used in inorganic layers is above 1.85, while the refractive index of organic layers on the production line does not exceed 1.50. As a result, the encapsulation layers prepared have a large difference in refractive index, which affects the light extraction efficiency of the device. Therefore, without affecting the inkjet printing performance, curing shrinkage rate, flexibility, outgass value and plasma etching resistance of the thin film encapsulation composition, improving the refractive index of organic thin films is gradually becoming a development trend. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composition, encapsulation structure and OLED device for OLED thin film encapsulation.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] On one hand, the present invention provides a composition for OLED thin film encapsulation, comprising the following components in parts by weight: 5 to 15 parts of nano-inorganic particles with a refractive index of not less than 1.7, 75 to 95 parts of photocurable monomer, 1 to 10 parts of photoinitiator, and 0.01 to 3 parts of additives.

[0008] Furthermore, the particle size of the nano-inorganic particles with a refractive index of not less than 1.7 is 1 to 15 nm; the nano-inorganic particles with a refractive index of not less than 1.7 contain zirconium oxide (ZrO2) and / or titanium dioxide (TiO2).

[0009] Furthermore, for the nano-inorganic particles with a refractive index of not less than 1.7, surface treatment can be performed to improve the dispersion stability of the nano-inorganic particles in the photocurable monomer, thereby reducing the haze of the encapsulated film composition after curing.

[0010] Furthermore, the photocurable monomer is a mixture of monofunctional (meth)acrylate, difunctional (meth)acrylate and polyfunctional (meth)acrylate, and the mass ratio is (70-100):(5-20):(1-10).

[0011] It should be noted that a "monofunctional" monomer refers to a monomer containing one photocurable functional group, a "difunctional" monomer refers to a monomer containing two photocurable functional groups, and a "multifunctional" monomer refers to a monomer containing three or more photocurable functional groups.

[0012] Furthermore, the monofunctional (meth)acrylate is a mixture of aryl (meth)acrylate and silicon (meth)acrylate, with a weight ratio of (10-15):1.

[0013] Furthermore, the structural formula of the aryl-containing (meth)acrylate is shown in Formula 1 below:

[0014]

[0015] In Formula 1, R1 and R2 are each independently selected from any one of hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C1-C30 aralkyl, substituted or unsubstituted C1-C30 aryl, substituted or unsubstituted C1-C30 aralkyl, and substituted or unsubstituted C1-C30 heteroaryl; R3 is hydrogen or methyl; X1 is a single bond, any one of C1-C12 alkylene or C1-C12 alkeneoxy; p and q are each independently integers from 0 to 5.

[0016] Furthermore, the structural formula of the silicon-containing (meth)acrylate is shown in Formula 2 below:

[0017]

[0018] In Formula 2, R4, R5, and R6 are each independently selected from substituted or unsubstituted C1-C6 alkyl groups, substituted or unsubstituted C1-C6 alkoxy groups, and substituted or unsubstituted phenyl groups; X2 is any one of substituted or unsubstituted C1-C6 alkylene groups and substituted or unsubstituted C1-C6 alkoxy groups; and R7 is hydrogen or methyl.

[0019] Furthermore, the difunctional (meth)acrylate is a (meth)acrylate containing a long carbon chain.

[0020] Specifically, the long-chain (meth)acrylate is an unsubstituted C1 to C20 straight-chain or branched alkyl (meth)acrylate, specifically tert-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, ethylhexyl (meth)acrylate (including at least one of 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and lauryl (meth)acrylate).

[0021] Furthermore, the multifunctional (meth)acrylate is at least one of trimethylolpropane triacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, propoxylated glycerol triacrylate, trimethylolpropane trimethacrylate, bis(trimethylolpropane)tetraacrylate, polydipentaerythritol pentaacrylate, sorbitol pentaacrylate, and dipentaerythritol hexaacrylate.

[0022] Furthermore, the photoinitiator component is a free radical initiator. The free radical initiator is at least one selected from triazine-based, acetophenone-based, benzophenone-based, thioxanone-based, benzoin-based, phosphorus-based, and oxime-based photoinitiators.

[0023] Specifically, the photoinitiator is a phosphorus-based photoinitiator, specifically one or more of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, benzyl(diphenyl)phosphine oxide, and bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide.

[0024] Furthermore, the additive is any one or more of the following: polymerization inhibitor, surfactant, antioxidant, defoamer, and leveling agent.

[0025] On the other hand, the present invention also provides an encapsulation structure comprising a first inorganic layer, an organic layer, and a second inorganic layer arranged alternately in sequence; the organic layer is formed using the composition for OLED thin film encapsulation described above, and the organic layer is an intermediate layer that can serve as a protective layer and a planarization layer for the device.

[0026] Furthermore, the thickness of the organic layer is 1–20 μm, and the refractive index is 1.55–1.70.

[0027] To obtain a high-performance composition for OLED thin-film encapsulation that meets the process requirements of inkjet printing, the encapsulation composition preferably has a viscosity of 15–40 mPa·s and a surface tension of 20–38 mN / m at 25°C.

[0028] Furthermore, the materials of the first inorganic layer and the second inorganic layer are at least one of silicon nitride, silicon oxynitride, silicon oxide, aluminum oxide, zirconium oxide, titanium oxide and zinc oxide, and the first inorganic layer and the second inorganic layer are formed by vacuum evaporation, DC sputtering or ion cluster deposition.

[0029] Furthermore, the thickness of both the first inorganic layer and the second inorganic layer is 200–300 nm, and the refractive index is 1.8–2.2.

[0030] Furthermore, the encapsulation structure is formed by depositing and coating the surface to be encapsulated in an alternating manner of inorganic layer-organic layer-inorganic layer.

[0031] In summary, the polymer film formed using the composition for OLED thin film encapsulation provided by this invention has a lower curing shrinkage rate, a smaller thickness difference, a lower outgas value, and a lower plasma etching resistance. It better meets the requirements of being able to withstand plasma etching during the formation of the inorganic layer and ensuring the flatness of the inorganic layer when combined with an inorganic layer to form an inorganic-organic-inorganic thin film encapsulation structure, thereby maintaining a better encapsulation effect.

[0032] In addition, the present invention also provides an OLED device, comprising a substrate, an OLED unit, and an encapsulation structure as described above in part or all of the above-described manner, arranged from bottom to top.

[0033] The applicant needs to clarify that, through long-term research, the inventors have discovered that when the refractive index of the organic layer in the encapsulation structure reaches 1.55–1.70, the light transmittance can be effectively improved, thereby further enhancing the luminous efficiency of the OLED device. This is because: when light emitted from the luminescent material enters the first inorganic layer, due to the difference in refractive indices between the first inorganic layer and the organic layer, the light is refracted at the interface between the two layers. If the angle of incidence is greater than the critical angle, total internal reflection can occur. When the refractive index of the organic layer in the encapsulation structure is 1.55–1.70, total internal reflection can be reduced, increasing the light extraction efficiency of the OLED device by 10–20%. However, if the refractive index of the organic layer is too low, the light emitted from the luminescent material is prone to total internal reflection at the interface between the first and organic layers, causing a waveguide effect in the first inorganic layer, thus reducing the light extraction efficiency of the OLED device. If the refractive index of the organic layer is too high, the light emitted from the luminescent material is prone to a waveguide effect in the second inorganic layer, thus reducing the light extraction efficiency of the OLED device.

[0034] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0035] 1. The present invention can effectively increase the refractive index of the composition used for thin film encapsulation by adding nano-inorganic particles with a refractive index of not less than 1.7, so that the refractive index of the organic layer is controllable between 1.55 and 1.70, which effectively improves the luminous efficiency of OLED devices, and also improves the plasma resistance and reduces the curing shrinkage rate of the composition used for thin film encapsulation.

[0036] 2. The composition for thin films prepared in this invention forms a stack of organic and inorganic layers after curing. On the one hand, it can improve the light emission efficiency of OLED devices, and on the other hand, it serves as an encapsulation layer to block water vapor and oxygen.

[0037] 3. The organic layer formed by the composition for OLED thin film encapsulation prepared in this invention has a lower curing shrinkage rate, a lower outgas value, and a lower plasma etching resistance rate. This better satisfies the requirement that when it is combined with the inorganic layer to form an "inorganic-organic-inorganic" thin film encapsulation structure, it can withstand the plasma etching during the formation of the inorganic layer, ensuring the flatness of the inorganic layer and thus maintaining a better encapsulation effect.

[0038] 4. In this invention, aryl-containing (meth)acrylates and silicon-containing (meth)acrylates in a weight ratio of (10-15):1 are selected with nano-inorganic particles with a refractive index of not less than 1.7 and a particle size of 1-10 nm. This combination exhibits good compatibility and stability, reducing the difficulty and risks of inkjet printing and resulting in superior optical effects and more uniform thickness.

[0039] 5. By using a mixture of (meth)acrylates with multiple functionalities and further defining their structure, this invention not only improves the encapsulation effect of the composition for OLED thin film encapsulation, but also firmly fixes the nano-inorganic particles in the cross-linked network of the encapsulation composition, ensuring the stability of the encapsulation composition. Attached Figure Description

[0040] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 A cross-sectional view of the OLED device provided by the present invention.

[0043] Wherein: 110, substrate; 120, OLED; 121, first electrode; 122, light-emitting material; 123, second electrode; 140, encapsulation structure; 141, first inorganic layer; 142, organic layer; 143, second inorganic layer. Detailed Implementation

[0044] Exemplary embodiments will be described in detail below. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of products consistent with some aspects of the invention as detailed in the appended claims.

[0045] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0046] Synthesis example

[0047] This synthetic example provides a detailed preparation process for Equation 1-1:

[0048]

[0049] 500 mL of ethyl acetate, 50 g of methyl (diphenyl)silane, and 80 g of allyl alcohol were added to a reactor, which was then purged three times with nitrogen. 144 ppm of platinum-carbon black catalyst was added to the reactor, which was heated to 80 °C and stirred for 4 h. The remaining solvent was removed by distillation to obtain compound (I). Then, 130 g of the obtained compound (I) and 32 g of triethylamine were added to 500 mL of dichloromethane, cooled to 0 °C, and 30 g of methacryloyl chloride was slowly added. The solvent was removed by distillation to obtain the compound shown in Formula 1-1.

[0050] Example 1

[0051] This embodiment provides a composition (I) for OLED thin film encapsulation, which, by weight, consists of 10 parts of nano-inorganic particles with a refractive index of not less than 1.7, 85 parts of photocurable monomer, 4 parts of photoinitiator, and 1 part of additive.

[0052] The nano-inorganic particles with a refractive index of not less than 1.7 are zirconium oxide (ZrO2) with an average particle size of 8 nm, and were purchased from Anhui Zhonghang Nanotechnology Development Co., Ltd.

[0053] The photocurable monomer is a mixture of monofunctional (meth)acrylate, difunctional (meth)acrylate and polyfunctional (meth)acrylate, in a mass ratio of 85:10:5.

[0054] The monofunctional (meth)acrylate is a mixture of aryl (meth)acrylate and silicone (meth)acrylate in a weight ratio of 13:1.

[0055] The aryl-containing (meth)acrylate is (2-Naphthylacrylate).

[0056] The silicon-containing (meth)acrylate has the structure shown in Formula 1-1, i.e.

[0057] The difunctional (meth)acrylate is dodecanediol dimethacrylate, purchased from TCIAMERICA.

[0058] The multifunctional (meth)acrylate is pentaerythritol triacrylate, purchased from Sigma-Aldrich.

[0059] The photoinitiator is a TPO photoinitiator.

[0060] The additive is a leveling agent, specifically a polyacrylate surface additive, purchased from BYK 361N.

[0061] Example 2

[0062] This embodiment provides a composition (II) for OLED thin film encapsulation, which, by weight, consists of 15 parts of nano-inorganic particles with a refractive index of not less than 1.7, 80 parts of photocurable monomer, 4 parts of photoinitiator, and 1 part of additive.

[0063] The nano-inorganic particles with a refractive index of not less than 1.7 are zirconium oxide (ZrO2) with an average particle size of 8 nm, and were purchased from Anhui Zhonghang Nanotechnology Development Co., Ltd.

[0064] The photocurable monomer is a mixture of monofunctional (meth)acrylate, difunctional (meth)acrylate and polyfunctional (meth)acrylate, in a mass ratio of 100:5:1.

[0065] The monofunctional (meth)acrylate is a mixture of aryl-containing (meth)acrylate and silicone-containing (meth)acrylate in a weight ratio of 15:1.

[0066] The aryl-containing (meth)acrylate is (2-Naphthylacrylate).

[0067] The silicon-containing (meth)acrylate has the structure shown in Formula 1-1, i.e.

[0068] The difunctional (meth)acrylate is dodecanediol dimethacrylate, purchased from TCIAMERICA.

[0069] The multifunctional (meth)acrylate is pentaerythritol triacrylate, purchased from Sigma-Aldrich.

[0070] The photoinitiator is a TPO photoinitiator.

[0071] The additive is a leveling agent, specifically a polyacrylate surface additive, purchased from BYK 361N.

[0072] Example 3

[0073] This embodiment provides a composition (III) for OLED thin film encapsulation, which, by weight, consists of 5 parts of nano-inorganic particles with a refractive index of not less than 1.7, 90 parts of photocurable monomer, 4 parts of photoinitiator, and 1 part of additive.

[0074] The nano-inorganic particles with a refractive index of not less than 1.7 are zirconium oxide (ZrO2) with an average particle size of 8 nm, and were purchased from Anhui Zhonghang Nanotechnology Development Co., Ltd.

[0075] The photocurable monomer is a mixture of monofunctional (meth)acrylate, difunctional (meth)acrylate and polyfunctional (meth)acrylate, in a mass ratio of 100:5:1.

[0076] The monofunctional (meth)acrylate is a mixture of aryl-containing (meth)acrylate and silicone-containing (meth)acrylate in a weight ratio of 10:1.

[0077] The aryl-containing (meth)acrylate is (2-Naphthylacrylate).

[0078] The silicon-containing (meth)acrylate has the structure shown in Formula 1-1, i.e.

[0079] The difunctional (meth)acrylate is dodecanediol dimethacrylate, purchased from TCIAMERICA.

[0080] The multifunctional (meth)acrylate is pentaerythritol triacrylate, purchased from Sigma-Aldrich.

[0081] The photoinitiator is a TPO photoinitiator.

[0082] The additive is a leveling agent, specifically a polyacrylate surface additive, purchased from BYK 361N.

[0083] Example 4

[0084] This embodiment provides a composition (IV) for OLED thin film encapsulation, which, by weight, consists of 10 parts of nano-inorganic particles with a refractive index of not less than 1.7, 85 parts of photocurable monomer, 3 parts of photoinitiator, and 2 parts of additives.

[0085] The nano-inorganic particles with a refractive index of not less than 1.7 are titanium dioxide (TiO2) with an average particle size of 10 nm, and were purchased from Anhui Zhonghang Nanotechnology Development Co., Ltd.

[0086] The photocurable monomer is a mixture of monofunctional (meth)acrylate, difunctional (meth)acrylate and polyfunctional (meth)acrylate, in a mass ratio of 100:5:10.

[0087] The monofunctional (meth)acrylate is a mixture of aryl-containing (meth)acrylate and silicone-containing (meth)acrylate in a weight ratio of 15:1.

[0088] The aryl-containing (meth)acrylate is (4-Biphenylmethanol acrylate);

[0089] The silicon-containing (meth)acrylate has the structure shown in Formula 1-1, i.e.

[0090] The difunctional (meth)acrylate is dodecanediol dimethacrylate, purchased from TCIAMERICA.

[0091] The multifunctional (meth)acrylate is pentaerythritol triacrylate, purchased from Sigma-Aldrich;

[0092] The photoinitiator is a TPO photoinitiator.

[0093] The additive is a leveling agent, specifically a polyacrylate surface additive, purchased from BYK 361N.

[0094] Example 5

[0095] This embodiment provides a composition (V) for OLED thin film encapsulation, which, by weight, consists of 10 parts of nano-inorganic particles with a refractive index of not less than 1.7, 85 parts of photocurable monomer, 3 parts of photoinitiator, and 2 parts of additives.

[0096] The nano-inorganic particles with a refractive index of not less than 1.7 are a mixture of titanium dioxide (TiO2) and zirconium oxide (ZrO2) in a mass ratio of 1:1.

[0097] The photocurable monomer is a mixture of monofunctional (meth)acrylate, difunctional (meth)acrylate and polyfunctional (meth)acrylate in a mass ratio of 100:5:10.

[0098] The monofunctional (meth)acrylate is a mixture of aryl-containing (meth)acrylate and silicone-containing (meth)acrylate in a weight ratio of 15:1.

[0099] The aryl-containing (meth)acrylate is (4-Biphenylmethanol acrylate);

[0100] The silicon-containing (meth)acrylate has the structure shown in Formula 1-1, i.e.

[0101] The difunctional (meth)acrylate is dodecanediol dimethacrylate, purchased from TCIAMERICA.

[0102] The multifunctional (meth)acrylate is pentaerythritol triacrylate, purchased from Sigma-Aldrich.

[0103] The photoinitiator is a TPO photoinitiator.

[0104] The additive is a leveling agent, specifically a polyacrylate surface additive, purchased from BYK 361N.

[0105] Using any of the compositions prepared in Examples 1-5 for OLED thin-film encapsulation, an organic layer is formed, and an inorganic layer-organic layer-inorganic layer alternating deposition coating is performed on the surface to be encapsulated to form an encapsulation structure. This encapsulation structure can be further used in OLED devices, combined with... Figure 1 As shown, the OLED device includes a substrate 110, an OLED unit 120, and an encapsulation structure 140 arranged sequentially from bottom to top. The OLED unit includes a first electrode 121, a light-emitting material layer 122, and a second electrode 123. The encapsulation structure 140 includes a first inorganic layer 141, an organic layer 142, and a second inorganic layer 143 arranged alternately in sequence. The organic layer 142 serves as an intermediate layer and is used as a protective layer and a planarization layer for the OLED device.

[0106] Comparative Example 1

[0107] The specific implementation method of Comparative Example 1 is the same as that of Example 1; the difference from Example 1 is that the composition (vi) for OLED thin film encapsulation described in Comparative Example 1, by weight, consists of 85 parts of photocurable monomer, 4 parts of photoinitiator, and 1 part of additive.

[0108] Comparative Example 2

[0109] The specific implementation of Comparative Example 2 is the same as that of Example 1; the difference from Example 1 is that in the composition (vii) for OLED thin film encapsulation described in Comparative Example 2, the monofunctional (meth)acrylate is only an aryl-containing (meth)acrylate.

[0110] Comparative Example 3

[0111] The specific implementation of Comparative Example 3 is the same as that of Example 1; the difference from Example 1 is that in the composition (eight) for OLED thin film encapsulation described in Comparative Example 3, the photocurable monomer is a mixture of monofunctional (meth)acrylate and difunctional (meth)acrylate, and the mass ratio is 85:10.

[0112] Comparative Example 4

[0113] The specific implementation of Comparative Example 4 is the same as that of Example 1; the difference from Example 1 is that in the composition (ix) for OLED thin film encapsulation described in Comparative Example 4, the nano-inorganic particles with a refractive index of not less than 1.7 are zirconium oxide with an average particle size of 20 nm, which were purchased from Anhui Zhonghang Nanotechnology Development Co., Ltd.

[0114] Performance testing:

[0115] (1) Curing shrinkage rate: The composition for OLED thin film encapsulation is coated onto a glass substrate and the curing shrinkage rate is 30 mW / cm. 2 The sample was then subjected to UV curing for 120 seconds by UV irradiation to produce a sample with dimensions of 5cm×5cm×1mm (width×length×thickness).

[0116] Curing shrinkage rate η = (Vb - Va) / Vb × 100%;

[0117] Where Vb is the volume before curing and Va is the volume after curing.

[0118] (2) Outgass Measurement: The composition for OLED thin-film encapsulation was coated with a 10 μm thick layer on a 5 cm × 5 cm glass substrate, and the coating was measured at 30 mW / cm² in a nitrogen atmosphere. 2 The sample was cured by UV irradiation for 60 seconds to obtain a cured organic layer, which was then cut into 1cm × 3cm samples. Outgassing was collected for 30 minutes at 120℃ using a JAI thermal desorption instrument (JTD-505Ⅲ). After analysis of the samples using gas chromatography-mass spectrometry (QP2020GC / MS), calibration curves were plotted, and the collected outgassing was analyzed.

[0119] (3) Plasma Etching Rate: The composition for OLED thin-film encapsulation was coated onto a silicon wafer and photocured to form an organic layer. The initial coating height of the organic layer (T1, unit: μm) was then measured. The organic barrier layer was subjected to plasma treatment under the following conditions: ICP power: 2500W; RE power: 300W; DC bias: 200V; Ar flow rate: 50sccm; etching time: 1 minute; pressure: 10 mTorr. The height of the organic layer (T2, unit: μm) was then measured. The plasma etch rate of the organic layer was calculated using the following equation:

[0120] Plasma etching rate (%) = (T1-T2) / T1 × 100%

[0121] Where T1 is the initial height of the organic layer, and T2 is the height of the organic layer after plasma treatment.

[0122] (4) Refractive index: A thin film with dimensions of 5 mm × 15 mm × 25 μm (width × length × thickness) was fabricated and then tested using an Abbe refractometer.

[0123] (5) Dynamic bending performance: A 10mm×120mm cured composition for OLED film encapsulation was fixed to the short side of the sample with tape. The sample was then mounted on a tension-free U-shaped folding tester (instrument name DLDMLH-FS, manufactured by YuasaSystem). The outer diameter (Φ) of the bending part of the tester was set to 4mm and the radius (R) to 2.5mm. The sample was folded in half and subjected to 20,000 180° dynamic bending tests. The tester checked whether cracks or fissures occurred at the bending part. If no cracks or fissures occurred at the bending part, the evaluation was (○). If cracks or fissures occurred at the bending part, the evaluation was (×).

[0124] The compositions (i) to (v) prepared in Examples 1 to 5 and the compositions (vi) to (ix) prepared in Comparative Examples 1 to 4 were subjected to performance tests. The test results are shown in Table 1 below:

[0125]

[0126]

[0127] As can be seen from the data in Table 1, the polymer films formed by the compositions obtained in Examples 1 to 5 of the present invention have lower curing shrinkage, lower outgass value, lower plasma etch resistance, higher refractive index, and good dynamic bending performance and inkjet printing performance.

[0128] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0129] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A composition for OLED thin-film encapsulation, characterized in that, It includes the following components in parts by weight: 5-15 parts of nano-inorganic particles with a refractive index of not less than 1.7, 75-95 parts of photocurable monomer, 1-10 parts of photoinitiator, and 0.01-3 parts of additives; The nano-inorganic particles with a refractive index of not less than 1.7 have a particle size of 1~15nm; the photocurable monomer is a mixture of monofunctional (meth)acrylate, difunctional (meth)acrylate and polyfunctional (meth)acrylate, and the mass ratio is (70~100):(5~20):(1~10). The monofunctional (meth)acrylate is a mixture of aryl-containing (meth)acrylate and silicon-containing (meth)acrylate, in a weight ratio of (10~15):1; The structural formula of the aryl-containing (meth)acrylate is shown in Formula 1 below: Formula 1 In Formula 1, R1 and R2 are each independently selected from any one of hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C1-C30 aryl, substituted or unsubstituted C1-C30 aralkyl, and substituted or unsubstituted C1-C30 heteroaryl; R3 is hydrogen or methyl; X1 is a single bond, any one of C1-C12 alkylene or C1-C12 alkeneoxy; p and q are each independently integers from 0 to 5. The structural formula of the silicon-containing (meth)acrylate is shown in Formula 2 below: Formula 2 In Formula 2, R4, R5, and R6 are each independently selected from substituted or unsubstituted C1-C6 alkyl groups, substituted or unsubstituted C1-C6 alkoxy groups, and substituted or unsubstituted phenyl groups; X2 is any one of substituted or unsubstituted C1-C6 alkylene groups and substituted or unsubstituted C1-C6 alkoxy groups; and R7 is hydrogen or methyl. The difunctional (meth)acrylate is a difunctional (meth)acrylate containing a long carbon chain, and the difunctional (meth)acrylate containing a long carbon chain is at least one selected from tert-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and lauryl (meth)acrylate.

2. The composition for OLED thin-film encapsulation according to claim 1, characterized in that, The nano-inorganic particles with a refractive index of not less than 1.7 include zirconium oxide and / or titanium dioxide.

3. A packaging structure comprising a first inorganic layer (141), an organic layer (142), and a second inorganic layer (143) arranged alternately in sequence, characterized in that, The organic layer (142) is formed using the composition for OLED thin film encapsulation as described in any one of claims 1-2 above, and the organic layer (142) serves as a protective layer and a planarization layer for the OLED device.

4. The packaging structure according to claim 3, characterized in that, The organic layer (142) has a thickness of 1~20 μm and a refractive index of 1.55~1.

70.

5. The packaging structure according to claim 3, characterized in that, The materials of the first inorganic layer (141) and the second inorganic layer (143) are at least one of silicon nitride, silicon oxynitride, silicon oxide, aluminum oxide, zirconium oxide, titanium oxide and zinc oxide.

6. The packaging structure according to claim 3, characterized in that, The thickness of the first inorganic layer (141) and the second inorganic layer (143) are both 200~300nm, and the refractive index is both 1.8~2.

2.

7. An OLED device, characterized in that, It includes a substrate (110), an OLED unit (120), and a packaging structure (140) as described in any one of claims 3-6, arranged from bottom to top.

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