Encapsulated inks for inkjet printing of glass substrates and use thereof

Abstract

This invention relates to the field of photocurable ink technology, specifically to an encapsulation ink for inkjet printing on glass substrates and its application. By weight, the components include: 10-20 parts of cage-like polysilsesquioxane, 50-80 parts of acrylic monomers, and 1-5 parts of an initiator; the acrylic monomers include epoxy-containing acrylate monomers, carboxyl-containing acrylate monomers, and hydroxyl-containing acrylate monomers. The encapsulation ink prepared by this invention can improve the interfacial compatibility between the glass substrate and the hydrophobic ink, reduce film shrinkage differences, and simultaneously possess excellent water vapor barrier properties and flexibility.

Description

Technical Field

[0001] This invention relates to the field of photocurable ink technology, specifically to an encapsulation ink for inkjet printing on glass substrates and its application. Background Technology

[0002] With the rapid development of display technology, flexible organic light-emitting diodes (OLEDs) have become one of the core development directions in the display field due to their advantages such as thinness, flexibility, and vibrant colors. Encapsulation materials, as a key component of OLED devices, directly affect the device's lifespan, stability, and flexibility. Organic encapsulation inks, due to their efficient film-forming characteristics adapted to inkjet printing, are widely used in the OLED inner screen encapsulation process. Glass substrates, with their excellent flatness, light transmittance, and mechanical strength, are often used as the core substrate for OLED inner screens. However, glass surfaces typically have high surface energy and hydrophilicity. Existing organic encapsulation inks have poor interfacial compatibility with glass surfaces and cannot be inkjet printed. This characteristic leads to uneven droplet spreading on the glass substrate surface during inkjet printing, and excessively rapid drying, easily causing problems such as film cracking and increased porosity, severely affecting the encapsulation effect and reducing the device's moisture barrier capability and long-term stability.

[0003] Developing an inkjet encapsulation ink that can improve the interfacial compatibility between glass substrates and hydrophobic inks, reduce film shrinkage differences, and simultaneously possess excellent water vapor barrier properties and flexibility has become a pressing technical problem to be solved in the current OLED encapsulation field. Summary of the Invention

[0004] The first aspect of the present invention provides an encapsulation ink for inkjet printing on glass substrates, comprising, by weight: 10-20 parts of cage-like polysilsesquioxane, 50-80 parts of acrylic monomers and 1-5 parts of initiator; wherein the acrylic monomers include epoxy-containing acrylate monomers, carboxyl-containing acrylate monomers and hydroxyl-containing acrylate monomers.

[0005] In existing technologies, most inkjet inks used for OLED packaging have not specifically optimized the interfacial compatibility between the glass substrate and the hydrophobic ink, and have not constructed an intermolecular force network through the synergistic construction of multiple polar groups. This results in large differences in the drying and shrinkage of droplets on the glass surface, insufficient adhesion between the film and the substrate, and difficulty in achieving both water vapor barrier properties and flexibility. This invention combines cage-like polysilsesquioxanes substituted with polar groups such as epoxy groups and various acrylic monomers (acrylate monomers containing epoxy groups, acrylate monomers containing carboxyl groups, and acrylate monomers containing hydroxyl groups). The rigid cage-like structure of the cage-like polysilsesquioxane provides mechanical support and barrier properties. Simultaneously, the epoxy, carboxyl, and hydroxyl groups carried by the three types of acrylate monomers synergistically interact with the epoxy groups of the cage-like polysilsesquioxane, promoting the orderly arrangement of molecular chain segments through non-covalent bonds such as hydrogen bonds. This constructs an ordered intermolecular force network, guiding the chain segments to align parallel to the glass substrate surface. This effectively improves the interfacial compatibility between hydrophilic glass and hydrophobic inks, solving the problem of excessively rapid droplet drying, and reducing local shrinkage differences caused by disordered chain segment accumulation. Furthermore, the cage-like structure complements the flexible chain segments of the acrylic monomers, resulting in an encapsulation ink that possesses both excellent water vapor barrier properties and flexibility.

[0006] The weight ratio of the epoxy-containing acrylate monomer, the carboxyl-containing acrylate monomer, and the hydroxyl-containing acrylate monomer is (5-10):(20-40):(20-30).

[0007] Optionally, the weight ratio of the epoxy-containing acrylate monomer, the carboxyl-containing acrylate monomer, and the hydroxyl-containing acrylate monomer is (8-10):(20-40):(20-30).

[0008] The epoxy-containing acrylate monomers include at least one of glycidyl methacrylate, glycidyl acrylate, glycidyl methacrylate, 3,4-epoxycyclohexyl methyl acrylate, 3,4-epoxycyclohexyl ethyl methacrylate, and glycidyl ether acrylate.

[0009] The carboxyl-containing acrylate monomers include at least one of acrylic acid, methacrylic acid, β-carboxyethyl acrylate, itaconic acid, maleic acid, and fumaric acid.

[0010] The hydroxyl-containing acrylate monomers include at least one of hydroxypropyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

[0011] Optionally, the epoxy-containing acrylate monomer includes glycidyl methacrylate.

[0012] Optionally, the carboxyl-containing acrylate monomer includes acrylic acid.

[0013] Optionally, the hydroxyl-containing acrylate monomer includes hydroxypropyl acrylate.

[0014] The cage-like polysilsesquioxanes include cage-like polysilsesquioxanes substituted with polar functional groups.

[0015] Optionally, the polar functional group includes any one or more of epoxy, carboxyl, and hydroxyl groups.

[0016] Optionally, the polar functional group includes an epoxy group.

[0017] Optionally, the cage-shaped polysilsesquioxane includes at least one of epoxycyclohexyl-cage-shaped polysilsesquioxane, disiloyl isobutyl-cage-shaped polysilsesquioxane, and glycidyl ether oxysilylpropyl-cage-shaped polysilsesquioxane. Specifically, it can be purchased from companies such as Xi'an Qiyue Biotechnology Co., Ltd. (187333-74-0 POSS) or Wengjiang Reagent γ-glycidyl ether oxysilylpropyl silsesquioxane (PB36189). Alternatively, it can be a combination of epoxycyclohexyl-cage-shaped polysilsesquioxane, disiloyl isobutyl-cage-shaped polysilsesquioxane, and glycidyl ether oxysilylpropyl-cage-shaped polysilsesquioxane, adapted to the combination of acrylic monomers, so as to introduce polar groups that can form strong interactions with glass surfaces (hydrophilic / high surface energy) into the ink system, while also improving the low defects (no cracks, no pores) after film formation after adaptation.

[0018] Optionally, the initiator includes at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl peroxide, tert-butyl peroxyneodecanate, and tert-butyl peroxide isobutyrate. In some specific embodiments, different suitable initiators can be used.

[0019] A second aspect of this invention provides an application of an encapsulation ink for inkjet encapsulation of OLED glass substrates. The ink is formed by compounding the aforementioned ink components and then sprayed onto the substrate using inkjet printers or other inkjet equipment.

[0020] Beneficial effects 1. The present invention prepares an encapsulation ink by compounding cage-like polysilsesquioxane and acrylic monomers, wherein the acrylic monomers include acrylate monomers containing epoxy groups, acrylate monomers containing carboxyl groups, and acrylate monomers containing hydroxyl groups. The resulting ink can improve the interfacial compatibility between glass substrates and hydrophobic inks, reduce film shrinkage differences, and at the same time have excellent water vapor barrier properties and flexibility.

[0021] 2. The present invention specifies that the weight ratio of epoxy-containing acrylate monomers, carboxyl-containing acrylate monomers, and hydroxyl-containing acrylate monomers is (5-10):(20-40):(20-30), which can effectively improve the forming quality of the film layer after ink encapsulation.

[0022] 3. Using the ink prepared by this invention for encapsulation can form a uniform and stable structure in the encapsulation film layer, and can have both good hydrophobicity and adhesion, which significantly improves the encapsulation effect and the long-term stability of the device.

[0023] 4. Using the ink prepared by this invention for encapsulation can impart excellent flexibility to the film layer, with a bending radius of less than 2 mm and a bending cycle of no less than 50,000 times, which is fully compatible with the application requirements of flexible OLEDs.

[0024] 5. The present invention limits the selection of cage-shaped polysilsesquioxane, which can improve the water vapor barrier performance of the encapsulation film layer formed by the ink, with a water vapor permeability of approximately 10%. -6 g / cm 2 / D and below can effectively resist the corrosion of packaged devices by external moisture. Detailed Implementation

[0025] Example 1 An encapsulation ink for inkjet printing on glass substrates, comprising, by weight: 12 parts of cage-like polysilsesquioxane (epoxycyclohexyl-cage-like polysilsesquioxane), 68 parts of acrylic monomers, and 3 parts of initiator (azobisisobutyronitrile); wherein the acrylic monomers are: 8 parts of epoxy-containing acrylate monomer (glycidyl methacrylate), 40 parts of carboxyl-containing acrylate monomer (acrylic acid), and 20 parts of hydroxyl-containing acrylate monomer (hydroxypropyl acrylate).

[0026] Example 2 An encapsulation ink for inkjet printing on glass substrates, comprising, by weight: 15 parts of cage-like polysilsesquioxane (epoxycyclohexyl-cage-like polysilsesquioxane), 50 parts of acrylic monomers, and 3 parts of initiator (diisopropylbenzene peroxide); wherein the acrylic monomers are: 10 parts of epoxy-containing acrylate monomer (glycidyl methacrylate), 20 parts of carboxyl-containing acrylate monomer (acrylic acid), and 20 parts of hydroxyl-containing acrylate monomer (hydroxypropyl acrylate).

[0027] Example 3 The specific implementation method is the same as in Example 1; the difference is that the epoxy-containing acrylate monomer is 3,4-epoxycyclohexyl ethyl methacrylate, the carboxyl-containing acrylate monomer is β-carboxyethyl acrylate, and the hydroxyl-containing acrylate monomer is hydroxybutyl acrylate.

[0028] Example 4 The specific implementation method is the same as in Example 1; the difference is that the cage-shaped polysilsesquioxane is glycidyl ether oxysilylpropyl-cage-shaped polysilsesquioxane.

[0029] Example 5 The specific implementation method is the same as in Example 1; the difference is that the cage-shaped polysilsesquioxane is an epoxy cyclohexyl-cage-shaped polysilsesquioxane and a disiloyl isobutyl-cage-shaped polysilsesquioxane in a weight ratio of 1:1.

[0030] Example 6 The specific implementation method is the same as in Example 1; the difference is that the cage-shaped polysilsesquioxane is glycidyl ether oxysilylpropyl-cage-shaped polysilsesquioxane and disiloyl isobutyl-cage-shaped polysilsesquioxane in a weight ratio of 1:1.2.

[0031] Comparative Example 1 The specific implementation method is the same as in Example 1; the difference is that the acrylic monomers are: 48 parts of acrylate monomers containing carboxyl groups and 20 parts of acrylate monomers containing hydroxyl groups.

[0032] Comparative Example 2 The specific implementation method is the same as in Example 1; the difference is that 20 parts of cage-shaped polysilsesquioxane and 60 parts of acrylic monomers are used; the acrylic monomers are: 40 parts of acrylate monomers containing carboxyl groups and 20 parts of acrylate monomers containing hydroxyl groups.

[0033] Comparative Example 3 The specific implementation method is the same as in Example 1; the difference is that the acrylic monomers are: 48 parts of epoxy-containing acrylate monomers and 20 parts of hydroxyl-containing acrylate monomers.

[0034] Comparative Example 4 The specific implementation method is the same as in Example 1; the difference is that the acrylic monomers are: 48 parts of acrylate monomers containing carboxyl groups and 20 parts of acrylate monomers containing epoxy groups.

[0035] Comparative Example 5 The specific implementation method is the same as in Example 1; the difference is that there are 6 parts of cage-shaped polysilsesquioxane and 85 parts of acrylic monomers.

[0036] Comparative Example 6 The specific implementation method is the same as in Example 1; the difference is that the cage-shaped polysilsesquioxane is: octaisobutyl-cage-shaped polysilsesquioxane.

[0037] Performance testing methods The encapsulation inks prepared in the examples and comparative examples were subjected to the following performance tests, and the test data are listed in Table 1. An application of the encapsulation ink is used in the inkjet encapsulation process of OLED glass substrates. The aforementioned ink components are compounded to form an ink, which is then sprayed onto the substrate using an inkjet printer or other inkjet equipment. Specifically, the above components are weighed and placed in a mixing tank, stirred at a uniform speed for 1-2 hours to obtain UV inkjet ink. This ink is then sprayed onto the OLED glass substrate, and after scanning light curing irradiation for 60 seconds, an encapsulation film is obtained.

[0038] 1. Water vapor transmission rate: Tested according to GB / T 1037-2011 at 38℃ and 90% RH. Unit: g / cm² / D.

[0039] 2. Bending radius: Using a bending tester, the encapsulation film is bent along the axis of the cylinder, and the minimum bending radius when visible cracks appear in the film is recorded. Unit: mm.

[0040] 3. Bending times: Using a bending tester, perform 180° reciprocating bends at a speed of 30 times / minute with a bending radius of 2mm. Record the number of bends at which the film layer cracks or peels off. Unit: 10,000 times.

[0041] 4. Water droplet angle: Refer to GB / T 30693-2014 "Measurement of contact angle between plastic film and water", use a contact angle measuring instrument to test the static water droplet angle on the film surface, unit: °.

[0042] The performance test data is as follows: Table 1

Claims

1. An encapsulated ink for inkjet of a glass substrate, characterized by, By weight, the components include: 10-20 parts of cage-like polysilsesquioxane, 50-80 parts of acrylic monomers and 1-5 parts of initiator; the acrylic monomers include epoxy-containing acrylate monomers, carboxyl-containing acrylate monomers and hydroxyl-containing acrylate monomers.

2. The encapsulating ink according to claim 1, characterized in that, The weight ratio of the epoxy-containing acrylate monomer, the carboxyl-containing acrylate monomer, and the hydroxyl-containing acrylate monomer is (5-10):(20-40):(20-30).

3. The encapsulating ink according to claim 2, wherein The weight ratio of the epoxy-containing acrylate monomer, the carboxyl-containing acrylate monomer, and the hydroxyl-containing acrylate monomer is (8-10):(20-40):(20-30).

4. The encapsulating ink according to claim 1 or 3, characterized by, The cage-like polysilsesquioxanes include cage-like polysilsesquioxanes substituted with polar functional groups.

5. The encapsulating ink according to claim 4, wherein The polar functional group includes one of epoxy, carboxyl, and hydroxyl groups.

6. The encapsulation ink according to claim 5, characterized in that, The polar functional groups include epoxy groups.

7. The encapsulating ink according to claim 1 or 6, characterized by The epoxy-containing acrylate monomers include at least one of glycidyl methacrylate, glycidyl acrylate, glycidyl methacrylate, 3,4-epoxycyclohexyl methyl acrylate, 3,4-epoxycyclohexyl ethyl methacrylate, and glycidyl ether acrylate.

8. The encapsulating ink according to claim 1 or 6, wherein The carboxyl-containing acrylate monomers include at least one of acrylic acid, methacrylic acid, β-carboxyethyl acrylate, itaconic acid, maleic acid, and fumaric acid.

9. The encapsulating ink according to claim 1 or 6, wherein The hydroxyl-containing acrylate monomers include at least one of hydroxypropyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

10. Use of the encapsulated ink according to any one of claims 1 to 9, characterized in that, Inkjet encapsulation process for OLED glass substrates.

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