Photo-curing epoxy ink as well as preparation method and application thereof

Abstract

The invention provides light-cured epoxy ink and a preparation method and application thereof, the light-cured epoxy ink comprises an alicyclic epoxy monomer, an oxetane monomer, a diluent, a photoinitiator, an adhesion promoter and an assistant, the alicyclic epoxy monomer is an alicyclic epoxy monomer containing more than two polycyclic rings in a molecule; and the adhesion promoter is glycidyl ether epoxy micromolecules containing hydroxyl groups. According to the epoxy ink composition disclosed by the invention, the rigid group alicyclic ring and the adhesion promoter with hydroxyl are introduced, so that the epoxy ink composition has high adhesion and film surface hardness at the same time. The light-cured printing ink provided by the invention has low viscosity and high light transmittance. The liquid crystal composition is suitable for the field of display panels such as OLEDs, Micro-LEDs and the like, and the ink-jet printing technology is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of display packaging, and is mainly applied to the fields of OLED or Micro-LED. Specifically, it relates to a photocurable epoxy ink with high adhesion, high hardness and high light transmittance for display packaging, its preparation method and application. Background Art

[0002] In recent years, with the rapid development of flat panel display technology, several mainstream display technologies have emerged, including OLED (Organic Light-Emitting Diode), Micro-LED (microarray LED direct display), etc.; these new display technologies are already comparable to traditional LCD (liquid crystal display) displays. With the development of new display technologies, various customized and diversified encapsulation protection materials have also emerged accordingly.

[0003] The main defect of OLED display technology in application is that the lifespan of the light-emitting device is relatively short. The key reason is that moisture and dust in the environment gradually penetrate through the encapsulation protection layer and damage the light-emitting layer, reducing the service life. Therefore, it is crucial to use reliable encapsulation materials to protect the light-emitting layer. The mainstream thin film encapsulation process is a sandwich structure of organic / inorganic thin film composites, with an organic thin film layer sandwiched between two inorganic thin film layers with extremely high water resistance. The organic thin film layer can protect the inorganic thin film layer and prevent damage due to mechanical stress.

[0004] For Micro-LED technology, the organic thin film encapsulation layer needs to have high adhesion to the black layer at the bottom of the LED lamp beads, and the film surface of the organic thin film layer needs to have high hardness to avoid mechanical scratches on the film surface during subsequent encapsulation processes.

[0005] At the same time, for OLED and Micro-LED technologies, a thin film encapsulation layer with higher transmittance can reduce the light loss of the light-emitting device and lower the device power consumption.

[0006] CN110982346A discloses an ink composition for OLED encapsulation, which uses a silicon-containing acrylate and a silicon-containing epoxy compound, and adopts a free radical and cation dual-curing system. The adhesion of the cured film is tested by the cross-cut method, and the results show that the adhesion is mostly at the level of grade 2 (according to the GB / T 9286-2021 standard, the best level of cross-cut adhesion is grade 0). The adhesion of this invention does not reach the optimal level.

[0007] CN117836303A discloses an ink composition of an acrylate system containing organosiloxane monomers. The adhesion of the cured film was tested by the cross-cut method, and the result showed that the adhesion could reach the level of grade 0 (corresponding to the 5B level described in this patent). The hardness of the composition was not tested in this invention. It is inferred from the highly flexible long-chain aliphatic and long-chain ether difunctional (meth)acrylate or (meth)acrylamide used in this invention that the cured film of this ink composition does not have a hardness of ≥2H (pencil hardness).

[0008] Therefore, it is necessary to develop a photocurable composition that can simultaneously meet high adhesion and high hardness, has good optical transmittance, a simple curing process, and is suitable for inkjet printing to solve the above technical problems. Summary of the Invention

[0009] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a photocurable epoxy ink that can meet the inkjet printing process and has high adhesion and high hardness. The photocurable epoxy ink has high adhesion and high hardness, excellent optical transmittance and low water vapor transmittance, so that when it is applied to display devices, it can effectively improve the light extraction efficiency, extend the device life and stability.

[0010] Another purpose of the present invention is to provide a preparation method and application of this photocurable epoxy ink.

[0011] To achieve this purpose, the present invention adopts the following technical solutions:

[0012] In the first aspect, the present invention provides a photocurable epoxy ink with high adhesion and high hardness for display packaging. The photocurable epoxy ink comprises the following components in parts by weight, based on 100 parts of the total weight:

[0013] alicyclic epoxy monomer 30-60 parts by weight, preferably 40-60 parts by weight;

[0014] oxetane monomer 10-40 parts by weight, preferably 10-30 parts by weight;

[0015] diluent 10-40 parts by weight, preferably 10-30 parts by weight;

[0016] photoinitiator 0.5-5 parts by weight, preferably 0.5-2 parts by weight;

[0017] adhesion promoter 0.5-2 parts by weight, preferably 0.5-1 part by weight;

[0018] auxiliary agent 0.01-2 parts by weight; preferably 0.1-1 part by weight.

[0019] As a preferred embodiment, the alicyclic epoxy monomer of the present invention contains more than two polycyclic rings, and epoxy groups are directly connected to each polycyclic ring.

[0020] As a preferred embodiment, the polycyclic ring of the present invention contains no less than four carbon atoms.

[0021] As a preferred embodiment, the adhesion promoter of the present invention is a glycidyl ether epoxy small molecule containing at least one hydroxyl group.

[0022] As a preferred embodiment, the alicyclic epoxy monomer of the present invention is a bifunctional or polyfunctional epoxy monomer containing at least two polyalicyclics in the molecule, and epoxyethyl groups are directly connected to the polyalicyclics.

[0023] As a preferred embodiment, the alicyclic epoxy monomer of the present invention is selected from one or more of the following structural formulas:

[0024]

[0025] As a preferred embodiment, the alicyclic epoxy monomer of the present invention is formula (Ⅰ) and / or formula (Ⅲ). It can provide high hardness performance to the film.

[0026] In the present invention, the dosage of the alicyclic epoxy monomer is 30 to 60 parts by weight, such as 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60 parts by weight, etc., preferably 40 to 60 parts by weight; considering from the perspective of improving the film hardness, the lower limit of the dosage of the alicyclic epoxy monomer is preferably 30 parts by weight, and the upper limit is preferably 60 parts by weight.

[0027] In a specific embodiment, the oxetane monomer of the present invention includes one or more of monofunctional oxetane compounds and polyfunctional oxetane compounds.

[0028] As a preferred embodiment, the monofunctional oxetane compounds of the present invention include but are not limited to one or more of 3-ethyl-3-((2-ethylhexyloxy)methyl)oxetane, 3-ethyl-3-(octyloxymethyl)oxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-(phenoxymethyl)oxetane, 3-allyloxyoxetane, 3-ethyl-3-allyloxyoxetane, 3-ethyl-3-acryloxymethyloxetane, 2-methyl-2-allyl-4-propyloxetane, etc.

[0029] As a preferred embodiment, the multi-functional oxetane compound of the present invention is one or more of 3,7-bis(3-oxetanyl)-5-oxanonane, benzenedimethylenedioxetane, oxetanyl sesquisiloxane, 1,4-bis((3-ethyl-3-oxetanylmethoxy)methyl)benzene, etc.

[0030] As a preferred embodiment, the oxetane monomer of the present invention is 3-ethyl-3-hydroxymethyloxetane and / or 3,7-bis(3-oxetanyl)-5-oxanonane.

[0031] As a preferred embodiment, the amount of the oxetane monomer of the present invention is 10 to 40 parts by weight, such as 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 parts by weight, preferably 10 to 30 parts by weight. Considering from the perspective of improving the printing effect, the lower limit of the amount of the oxetane compound is preferably 10 parts by weight, and the upper limit is preferably 30 parts by weight. Considering from the perspective of improving the curing efficiency, the lower limit of the amount of the oxetane compound is more preferably 20 parts by weight, and the upper limit is more preferably 30 parts by weight.

[0032] As a preferred embodiment, the diluent of the present invention is a vinyl ether compound.

[0033] As a preferred embodiment, the vinyl ether compound of the present invention includes but is not limited to one or more of limonene-1,2-epoxide, dicyclopentadiene vinyl ether, 1,4-butanediol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, 1,4-dicyclohexane dimethyl divinyl ether, etc.

[0034] As a preferred embodiment, the vinyl ether compound of the present invention is limonene-1,2-epoxide.

[0035] As a preferred embodiment, the amount of the diluent of the present invention is 10 to 40 parts by weight, such as 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 parts by weight, preferably 10 to 30 parts by weight. Considering from the perspective of improving the printing effect, the lower limit of the amount of the diluent is preferably 10 parts by weight, and the upper limit is preferably 40 parts by weight. Considering from the perspective of suppressing the volatile content, the upper limit of the amount of the diluent is more preferably 30 parts by weight. The diluent mainly plays a role in adjusting the viscosity of the epoxy ink. After determining the weights of other components, the amount of the diluent can be adjusted to keep the ink viscosity within the required range.

[0036] As a preferred embodiment, the photoinitiator of the present invention is a cationic photoinitiator, preferably selected from one or more of aromatic sulfonium salts, aromatic iodonium salts, aromatic diazonium salts, aromatic ammonium salts, and ferrocene salts.

[0037] As a preferred embodiment, the photoinitiator of the present invention includes, but is not limited to, one or more of phenyl diazonium hexafluorophosphate, phenyl diazonium hexafluoroantimonate, isopropylphenylcyclopentadienyliron hexafluorophosphate, diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate, diphenyl-4-(phenylthio)phenylsulfonium hexafluoroantimonate, diphenyl-4-(phenylthio)phenylsulfonium tetrafluoroborate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis(pentafluorophenyl)borate.

[0038] As a preferred embodiment, the amount of the photoinitiator of the present invention is 0.5 to 5 parts by weight, such as 0.6, 0.8, 1.0, 1.5, 2.0, 2.5, 2.5, 3.0, 3.5, 4.0, 4.5, 5 parts by weight, preferably 0.5 to 2 parts by weight. Considering the improvement of the curing effect, the lower limit of the amount of the photo cationic initiator is preferably 0.5 part by weight, and the upper limit is preferably 5 parts by weight. Considering the improvement of storage stability, the lower limit of the amount of the photoinitiator is more preferably 0.1 part by weight, and the upper limit is more preferably 2 parts by weight.

[0039] As a preferred embodiment, the adhesion promoter of the present invention is a glycidyl ether epoxy small molecule containing at least one hydroxyl group.

[0040] As a preferred embodiment, the adhesion promoter of the present invention is mainly a hydroxyl-containing glycidyl ether synthesized from small molecule polyols and epichlorohydrin. Specifically, commercially available products can be directly selected, and one or more of the following compound structural formulas 1 to 3 can be selected, and they can be obtained from Nagase in Japan:

[0041]

[0042] As a preferred embodiment, the additives of the present invention mainly include one or more of sensitizers and leveling agents.

[0043] As a preferred embodiment, the sensitizers of the present invention include, but are not limited to, one or more of thioxanthone compounds, 2,2-dimethoxy-1,2-diphenylethane-1-one, benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis(dimethylamino)benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide.

[0044] As a preferred embodiment, the leveling agent of the present invention includes, but is not limited to, BYK-307, BYK-333 of BYK Chemie, etc. The leveling agent is beneficial to the spreading of the ink into a film and the uniformity of the film thickness.

[0045] As a preferred embodiment, the addition amount of the agent of the present invention is 0.01 to 2 parts by weight, such as 0.1, 0.5, 1, 1.5, 2 parts by weight, etc.

[0046] On the other hand, the present invention provides a method for preparing a photocurable epoxy ink with high adhesion and high hardness for display packaging, comprising the following steps: According to the ratio, in the yellow light area or under light-shielding conditions, an alicyclic epoxy monomer, an oxetane monomer, a diluent, a photoinitiator, an adhesion promoter, and an agent are added to a reaction kettle, and the temperature is maintained within the range of 20-30 °C and stirred for 30-60 min to make the composition uniformly mixed, and then filtered to obtain the photocurable epoxy ink composition with a viscosity between 10-30 cps.

[0047] As a preferred embodiment, the filtration of the present invention uses a filter membrane with a pore size of 0.45 μm.

[0048] In yet another aspect, the application of the aforementioned photocurable epoxy ink with high adhesion and high hardness for display packaging or the photocurable epoxy ink for display packaging prepared by the aforementioned preparation method in the inkjet printing process in the field of display packaging.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The photocurable epoxy ink composition of the present invention comprises an alicyclic epoxy monomer, a diluent, an oxetane compound, a photoinitiator, an adhesion promoter, and an agent. Due to the rigid alicyclic structure of the alicyclic epoxy monomer, it can provide a high surface hardness to the cured ink film. On the other hand, the adhesion of the film can be improved by a small amount of adhesion promoter. Previous studies have found that if a photocurable ink film is to have high hardness, a rigid structure and an increased crosslinking density need to be selected, but this results in excessive internal stress during the curing process of the ink and insufficient toughness of the film, making it difficult to achieve good adhesion. The solution of the present invention can improve the adhesion of the film to an excellent level while maintaining the high hardness of the film.

[0051] The photocurable epoxy ink packaging composition prepared by the present invention can have excellent optical transmittance and low water vapor transmittance. Detailed Embodiments

[0052] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments, all of which do not depart from the scope of the present invention, and the descriptions therein are for illustrative purposes in nature and not intended to limit the present invention.

[0053] Main raw material sources:

[0054] A Alicyclic epoxy resin:

[0055] A1: Tetrahydroindene diepoxide of formula (Ⅲ) (purchased from Shaanxi Xihua Chemical Industry Co., Ltd.)

[0056] A2: 3,4-Epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate of formula (Ⅰ) (purchased from Nantong New Nassie); B: Oxetane monomer:

[0057] B1: 3-Ethyl-3-hydroxymethyloxetane (purchased from Donghua New Materials);

[0058] B2: 3,7-Bis(3-oxetanyl)-5-oxanonane (purchased from Donghua New Materials);

[0059] C Diluent:

[0060] Limonene-1,2-epoxide (purchased from Aladdin Reagents)

[0061] D Cationic photoinitiator:

[0062] UVI-6976 (purchased from Donghua New Materials);

[0063] E Adhesion promoter:

[0064] E1: DENACOL EX-313 (compound of formula 1) (purchased from Nagase, Japan);

[0065] E2: DENACOL EX-614B (compound of formula 3) (purchased from Nagase, Japan)

[0066] F Auxiliary agent:

[0067] F1: Sensitizer TR-PSS-510 (purchased from Qiangli New Materials);

[0068] F2: BYK-307 (purchased from BYK Chemie)

[0069] Example 1

[0070] 40 parts by weight of bis-7-oxabicyclo[4,1,0]heptane, 30 parts by weight of 3-ethyl-3-hydroxymethyloxetane, 30 parts by weight of 1,2-epoxy-4-vinylcyclohexane, 1 part by weight of initiator UVI-6976, 1 part by weight of adhesion promoter DENACOL EX-313, 0.1 part by weight of sensitizer TR-PSS-510 and 0.1 part by weight of leveling agent BYK-307 were put into a reaction kettle. Under light-shielded conditions, the temperature was maintained in the range of 20-30 °C and stirred at 60 r / min for 60 min to make the composition uniformly mixed. After being uniformly mixed, the mixture was filtered through a 0.45-μm filter membrane to obtain a clear and transparent liquid sample.

[0071] According to the preparation method of Example 1, Examples 2-6 and Comparative Examples 1-2 were prepared with the parts by weight shown in Table 1.

[0072] Table 1 Formulations of Examples and Comparative Examples

[0073]

[0074] Performance Test

[0075] 1) Sample viscosity

[0076] The sample was added to a rheometer, and the viscosity of each composition was tested at 25 °C.

[0077] 2) Preparation of cured film

[0078] The composition was spin-coated uniformly on a clean glass substrate and cured by irradiation with a UV-LED light source in the 395-nm band with a curing energy of 2500 mJ / cm 2 , irradiated and cured in air. A film with a thickness of about 16 μm was prepared.

[0079] 3) Adhesion test: Referring to the test standard of GB / T 9286-2021, the adhesion of the cured film was tested using the cross-cut method. The adhesion was divided into grades 0-5. The smaller the number, the stronger the adhesion.

[0080] 4) Pencil hardness test: Tested according to GB / T 6739-2006. The pencil load was 750 g, and the scratch results were H-6H. The higher the number, the higher the hardness. Scratch results of HB and B-6B indicate that the film surface is softer.

[0081] 5) Transmittance test: For the cured film, the light transmittance of each sample was tested using a colorimeter (HunterLab UltraScan VIS).

[0082] 6) Reliability test

[0083] After the cured film was placed in an environment of 85°C and 85% Rh for 500 h, there was no peeling or damage on the surface, which is represented by and the appearance of damage on the surface is represented by .

[0084] 7) Water vapor transmission rate: Measured for 24 h using a water permeability measuring instrument (Model 3, MOCON) at 40°C and 90% relative humidity.

[0085] 8) Inkjet performance test

[0086] The inkjet printing performance of each composition was tested using a piezoelectric drop-on-demand print head (KM1024i, Konica Minolta). With an inkjet head temperature of 25°C, films of 10 μm and 16 μm were printed on a glass substrate respectively. The film surface was observed using an OM microscope. A flat surface is represented by and the appearance of defects or inability to form a film on the surface is represented by .

[0087] The results of the performance test are shown in Table 2 below:

[0088] Table 2 Results of performance test

[0089]

[0090]

[0091] It can be seen from the results of the performance test data in the table that the photocurable compositions prepared in Examples 1-6 have higher adhesion compared to the comparative examples, and at the same time have relatively high hardness. It can be seen from Example 1 and Comparative Example 1 that the adhesion promoter used in Example 1 can significantly improve the adhesion. It can be seen from Example 1 and Comparative Example 2 that when the proportion of the alicyclic epoxy monomer added is too low, the cured film is relatively soft and the hardness has not reached H. In addition, the film transmittance of the examples is higher than that of the comparative examples, and for the inkjet printing process, under the condition of a relatively low film thickness of 10 μm, the examples can all form films well and the film surface is flat; while there are defects on the film surface of the comparative examples.

[0092] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A photocurable epoxy ink comprising the following components in parts by weight, based on 100 parts by total weight: 30 to 60 parts by weight of alicyclic epoxy monomer, preferably 40 to 60 parts by weight; 10 to 40 parts by weight of oxetane monomer, preferably 10 to 30 parts by weight; 10 to 40 parts by weight of diluent, preferably 10 to 30 parts by weight; 0.5 to 5 parts by weight, preferably 0.5 to 2 parts by weight, of a photoinitiator; 0.5 to 2 parts by weight, preferably 0.5 to 1 part by weight, of an adhesion promoter; The auxiliary agent is 0.01 to 2 parts by weight; preferably 0.1 to 1 part by weight.

2. The light-curing epoxy ink according to claim 1, characterized in that: The alicyclic epoxy monomer is selected from one or more of the following structural formulas:

3. The light-curing epoxy ink according to claim 1 or 2, characterized in that: The oxetane monomer comprises one or more of a monofunctional oxetane compound and a multifunctional oxetane compound; the monofunctional oxetane compound comprises one or more of 3-ethyl-3-((2-ethylhexyloxy)methyl)oxetane, 3-ethyl-3-(octyloxymethyl)oxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-(phenoxymethyl)oxetane, 3-allyloxyoxetane, 3-ethyl-3-allyloxyoxetane, 3-ethyl-3-acryloyloxymethyloxetane, and 2-methyl-2-allyl-4-propyloxetane; The multifunctional oxetane compound includes one or more of 3,7-bis(3-oxetanyl)-5-oxonane, xylylenebisoxetane, oxetanylsilsesquioxane, and 1,4-bis((3-ethyl-3-oxetanylmethoxy)methyl)benzene; Preferably, the oxetane monomer is 3-ethyl-3-hydroxymethyloxetane and / or 3,7-bis(3-oxetanyl)-5-oxonane.

4. The light-curable epoxy ink according to any one of claims 1 to 3, characterized in that: The diluent is a vinyl ether compound; preferably, the vinyl ether compound includes one or more of limonene-1,2-epoxide, dicyclopentadiene vinyl ether, 1,4-butanediol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, and 1,4-dicyclohexane dimethyl divinyl ether; more preferably, the vinyl ether compound is limonene-1,2-epoxide.

5. The light-curable epoxy ink according to any one of claims 1 to 4, characterized in that: The photoinitiator is a cationic photoinitiator, preferably selected from one or more of aromatic sulfonium salts, aromatic iodonium salts, aromatic diazonium salts, aromatic ammonium salts, and ferrocenium salts; preferably, the photoinitiator includes one or more of phenyldiazonium hexafluorophosphate, phenyldiazonium hexafluoroantimonate, isopropylcyclopentadienylferron hexafluorophosphate, diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate, diphenyl-4-(phenylthio)phenylsulfonium hexafluoroantimonate, diphenyl-4-(phenylthio)phenylsulfonium tetrafluoroborate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, and diphenyliodonium tetrakis(pentafluorophenyl)borate.

6. The light-curable epoxy ink according to any one of claims 1 to 5, characterized in that: The adhesion promoter is a glycidyl ether epoxy small molecule having at least one hydroxyl group.

7. The light-curable epoxy ink according to any one of claims 1 to 6, characterized in that: The adhesion promoter comprises one or more of the following formulas 1 to 3:

8. The light-curable epoxy ink according to any one of claims 1 to 7, characterized in that: The auxiliary agent comprises at least one of a sensitizer and a leveling agent; the sensitizer comprises one or more of a thioxanthone compound, 2,2-dimethoxy-1,2-diphenylethane-1-one, benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis(dimethylamino)benzophenone, and 4-benzoyl-4'-methyldiphenyl sulfide; the leveling auxiliary agent comprises BYK-307 and / or BYK-333 of BYK Chemical.

9. A method for preparing the photocurable epoxy ink according to any one of claims 1 to 8, comprising the following steps: adding alicyclic epoxy monomer, oxetane monomer, diluent, photoinitiator, adhesion promoter and auxiliary agent into a reaction kettle in a yellow light region or under light-proof conditions according to proportion, maintaining the temperature in the range of 20-30° C. and stirring for 30-60 minutes to mix the composition evenly, filtering and obtaining a photocurable epoxy ink with a viscosity of 10-30 cps.

10. Use of the photocurable epoxy ink according to any one of claims 1 to 8 or the photocurable epoxy ink prepared by the method according to claim 9 in an inkjet printing process for display packaging.

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