A photoinitiator composition and an ultraviolet light curable ink based on the photoinitiator composition

Abstract

The application belongs to the technical field of organic thin film packaging, relates to the technical field of ultraviolet light curable ink, and relates to a photoinitiator composition and ultraviolet light curable ink based on the photoinitiator composition. The photoinitiator composition is composed of a first photoinitiator and a second photoinitiator mixed according to a weight ratio of 1:(0.1-10); the first photoinitiator is a monoacyl phosphine oxide compound, and the second photoinitiator is a bisacyl phosphine oxide compound. The ultraviolet light curable ink prepared based on the photoinitiator composition has a long absorption wavelength under a 395 nm UV-LED light source and has good photoinitiator activity, so as to absorb as much as possible limited ultraviolet light energy, thereby promoting the development of environment-friendly and energy-saving UV light curing.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of ultraviolet light-curable ink, and relates to a photoinitiator composition and an ultraviolet light-curable ink based on the photoinitiator composition. BACKGROUND

[0002] With the development of science and technology, the renewal and replacement of electronic products are also changing rapidly, and many display devices also change from heavy and rigid to light and foldable and bendable, which inevitably puts forward higher requirements for the performance and service life of the display devices; and the performance and service life of the display devices are determined not only by their own characteristics, but also by the external packaging effect. Thin film packaging, represented by a three-layer structure, has become the mainstream way of flexible OLED packaging due to its excellent performance. It is known in the industry that the three-layer structure is a first inorganic layer (SiNx) as a smooth substrate, an organic layer as an intermediate layer, which is coated on the substrate by inkjet printing and then cured by ultraviolet light, and a third layer is the last inorganic layer (SiNx). The ultraviolet light-curable ink as the intermediate organic layer needs to have excellent curing rate, light curing rate and yellowing resistance, and in order to meet the actual use requirements, many researchers have studied the ultraviolet light-curable ink, but most researchers only consider the structure and performance of the light-curable material, and do not make in-depth research on the photoinitiator.

[0003] The wavelength of ultraviolet light when the traditional mercury lamp type ultraviolet light curing equipment works is mainly 365nm. Compared with mercury lamps, the wavelength of ultraviolet light sources excited by semiconductor light-emitting diodes can save 80% to 90% of electrical energy, and the wavelengths are mainly 385nm, 395nm and 405nm. There are few conventional photoinitiators that match them, so problems such as slow curing rate and low light curing rate are often encountered in UV-LED light curing, which is closely related to the selection of photoinitiators in the specific light curing formula system. Photoinitiator is a key component of the light curing system, which is related to whether the crosslinking polymerization reaction of the light-curable monomer and the active diluent can be initiated when the system is irradiated by light. It has an important influence on the light curing rate and light curing rate of the ink. Therefore, developing a photoinitiator suitable for the 395nm LED light curing wavelength is the key to the current LED-UV light curing field. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a photoinitiator composition and an ultraviolet light-curable ink based on the photoinitiator composition, so as to solve the problems of large amount of photoinitiator, low light curing rate, slow curing rate and poor surface drying in the curing process of the current ultraviolet light-curable ink.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] In one aspect, the present application provides a photoinitiator composition, which is composed of a first photoinitiator and a second photoinitiator mixed in a weight ratio of 1:(0.1-10); the first photoinitiator is a monoacyl phosphine oxide compound, and the second photoinitiator is a bisacyl phosphine oxide compound.

[0007] Specifically, the structure of the monoacyl phosphine oxide compound is shown in formula (1), and the structure of the bisacyl phosphine oxide compound is shown in formula (2):

[0008]

[0009] In formula (1) to formula (2), R1, R2, R3 are each independently a substituted or unsubstituted aryl group.

[0010] Further, the structure of the monoacyl phosphine oxide compound includes any one of formula (1-1) to formula (1-3):

[0011]

[0012] Further, the bisacyl phosphine oxide compound includes at least any one of raw materials shown in formula (2-1) to formula (2-3):

[0013]

[0014]

[0015] For the strong electron-withdrawing group carbonyl and phosphine acyl in the acyl phosphine oxide photoinitiator, and the photoinitiator under the same concentration, the activity of the free radicals generated by the acyl phosphine oxide photoinitiator is stronger, and the chromophore group is more prone to be destroyed under the irradiation of ultraviolet light at about 395 nm. Therefore, the acyl phosphine oxide photoinitiator can effectively improve the light transmittance of the ultraviolet curing ink used in the system of encapsulating OLED, and greatly improve the curing rate and stability of the ultraviolet curing ink.

[0016] However, the inventors found in the experiment that the single acyl phosphine oxide photoinitiator cannot meet the requirements of high light transmittance, high curing rate and low photoinitiator dosage when applied to the ultraviolet curing ink for encapsulating OLED. The inventors found through extensive research that when the acyl phosphine oxide photoinitiator is a mixture of monoacyl phosphine oxide compound and bisacyl phosphine oxide compound, the curing rate and light transmittance of the ultraviolet curing ink are improved, and the dosage of the photoinitiator is reduced, thereby avoiding the problems of surface unevenness and yellowing caused by rapid curing of the surface when the dosage of the photoinitiator is too high. However, when the weight ratio of the monoacyl phosphine oxide compound and the bisacyl phosphine oxide compound is too small, the hardness is poor, and the yellowing resistance is poor; when the weight ratio of the monoacyl phosphine oxide compound and the bisacyl phosphine oxide compound is too large, the curing rate and the light curing rate of the ultraviolet curing ink are too low. Based on this, the inventors found through extensive experiments that the effect is best when the weight ratio of the monoacyl phosphine oxide compound and the bisacyl phosphine oxide compound is 1: (0.1-10).

[0017] On the other hand, the application also provides the use of the above-mentioned photoinitiator composition in ultraviolet light curable ink. The ultraviolet light curable ink is ejected from the nozzle hole of an inkjet printer, and is irradiated by a UV-LED lamp with an irradiation light intensity of 10-100 mW / cm 2 , and a wavelength of 395 nm, to obtain a coating layer with a thickness of 1-20 μm.

[0018] Further, the viscosity of the ultraviolet curing ink at a temperature of 25°C is 15-40 cps.

[0019] The application also provides an ultraviolet light curable ink prepared from the above-mentioned photoinitiator composition, wherein the weight of the photoinitiator composition accounts for 0.1-4% of the total weight of the ultraviolet light curable ink.

[0020] The high amount of photoinitiator can improve the curing rate of the ultraviolet light curable ink, but reduces the hardness and solvent resistance of the coating, and the yellowing resistance is poor. The present inventors have found through extensive research that when a specific proportion of a monoacyl phosphine oxide compound and a bisacyl phosphine oxide compound photoinitiator is used, the amount of photoinitiator added to the ultraviolet light curable ink can be effectively reduced, and at the same time, the low viscosity ultraviolet light curable ink can be cured in 30s, and has good surface dryness and light curing rate. This is because: on the one hand, a specific proportion of a monoacyl phosphine oxide compound and a bisacyl phosphine oxide compound, when irradiated by 395nm UV-LED ultraviolet light, a large amount of photoinitiator is enriched on the surface of the ink system, so that a high concentration of free radicals can be generated in the surface, part of the free radicals consume the dissolved oxygen in the ink system in a short time, and the other part of the free radicals polymerize on the surface, so that the surface of the coating is completely cured. On the other hand, the bisacyl phosphine oxide compound has higher initiation activity than the monoacyl phosphine oxide compound, and can generate 4 free radical active centers, which can further trigger the photolysis of the monoacyl phosphine oxide compound into aryl formyl free radicals and aryl-ethoxy-phosphine acyl free radicals, improve the initiation activity, and generate a large number of active free radicals in a short time. In addition, the presence of monoacyl phosphine oxide can also promote the second dissociation of bisacyl photoinitiator, thereby having high initiation efficiency for curable monomers and effectively promoting crosslinking and curing reaction.

[0021] The ultraviolet light curable ink provided by the present application comprises at least one monomer containing a (meth)acrylate photocurable group.

[0022] Specifically, the ultraviolet light curable ink comprises, by weight percentage, at least: 10-80% of a photocurable monomer, 10-75% of a photocurable diluent monomer, 0.1-4% of a photoinitiator, and 0-5% of an auxiliary agent.

[0023] Further, the photocurable monomer is an aromatic (meth)acrylate monomer.

[0024] Further, the aromatic (meth)acrylate monomer has two or more substituted or unsubstituted phenyl groups, specifically including substituted or unsubstituted biphenyl groups, substituted or unsubstituted terphenyl groups, substituted or unsubstituted biphenylene groups, substituted or unsubstituted bisphenol F groups, substituted or unsubstituted terphenyloxy groups, substituted or unsubstituted quaterphenyl groups, substituted or unsubstituted quinquephenyl phenyloxy groups, and structural isomers of the above-mentioned groups.

[0025] Further, the photo-curable diluent monomer is one or more of a mono-functional (meth)acrylate of a C1 to C30 mono-alcohol, a di(meth)acrylate of a C2 to C30 di-alcohol, tri-alcohol, tetra-alcohol or penta-alcohol, a tri(meth)acrylate of a C3 to C30 tri-alcohol, tetra-alcohol or penta-alcohol.

[0026] Further, the photo-initiator is the photo-initiator composition described above.

[0027] In addition, the present application also provides a preparation method of the ultraviolet light curable ink, specifically, the photo-curable monomer, the photo-curable diluent monomer, the photo-initiator and the auxiliary agent are added into a brown reaction bottle under light-proof conditions, mixed uniformly, filtered, and the ultraviolet light curable ink is obtained.

[0028] In order to improve the film-forming performance of the light-curing packaging composition, the auxiliary agent comprises one or more of a polymerization inhibitor, a surfactant, an antioxidant, a heat stabilizer, a defoaming agent, and a leveling agent.

[0029] Compared with the prior art, the technical scheme provided by the present application has the following beneficial effects:

[0030] 1. The photo-initiator composition provided by the present application is applied to the low-viscosity ultraviolet light curable ink, and under the irradiation of a 395nm UV-LED light source with an ultraviolet light intensity of 20-100mW / cm 2 , the curing can be completed within 30 seconds, and the coating obtained after curing has good surface dryness, high transparency and strong yellowing resistance, and is especially suitable for thin film coatings with a thickness of 50μm or less.

[0031] 2. The photo-initiator composition provided by the present application can effectively improve the curing rate of the ultraviolet light curable ink, and the curing rate can reach 96% or more, and the hardness can reach 2H, thereby effectively ensuring the requirements of the ultraviolet light curable ink for OLED packaging.

[0032] 3. The photo-initiator composition provided by the present application is applied to the ultraviolet light curable ink, has a long wavelength of absorption under the 395nm UV-LED light source, and has good photo-initiator activity, so as to absorb as much limited ultraviolet light energy as possible, thereby promoting the development of the environment-friendly and energy-saving UV light curing. DETAILED DESCRIPTION

[0033] The exemplary embodiments will be described in detail herein below, and the embodiments described in the following exemplary embodiments do not represent all the embodiments consistent with the present application. Instead, they are merely examples of compositions, products consistent with some aspects of the present application as detailed in the appended claims.

[0034] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below in conjunction with examples.

[0035] Preparation Example 1

[0036] The structural formula of the monoacyl phosphine oxide compound is formula (1-2), and the synthesis route thereof is as follows:

[0037]

[0038] Specifically, the preparation process is as follows: 9g of 4-biphenyl formaldehyde (A1) is added into a reaction container with 50mL of ethyl acetate, after being fully dissolved, 11g of diphenyl phosphine oxide (B1) is added, stirring at room temperature for 8h, and then a white solid (C1) is obtained by filtration, which is washed with ethyl acetate for three times, and then white crystals are obtained by vacuum filtration; then 3g of the obtained white solid is weighed and placed in a reaction container, 50mL of toluene is added for dissolution, then 15g of manganese dioxide is weighed and stirred, and the reaction is carried out at 10℃ for 8h, after the reaction is completed, vacuum filtration is carried out, and anhydrous sodium sulfate is dried, and then the solvent is removed by vacuum distillation, so that the target product formula (1-2) is obtained, and the yield is 76%.

[0039] Preparation Example 2

[0040] The raw material of the bisacyl phosphine oxide compound is shown in formula (2-2), and the synthesis route thereof is as follows:

[0041]

[0042] Specifically, the preparation process is as follows: 200mL of water, 56.1g of phenyl phosphine oxide (A2), 64.4g of 2-naphthaldehyde (B2), 0.2g of potassium tert-butoxide and 1g of cetyl pyridinium chloride salt are added into a reaction container, and fully stirred until uniform, and then the reaction is carried out at room temperature for 4h to obtain a mixed solution (C2), 0.1g of super strong acid catalyst tungstosilicic acid is added into the mixed solution, while stirring, 0.5g of hydrogen peroxide is added dropwise into the above system, after the dropwise addition is completed, the reaction is carried out at room temperature for 8h, after the reaction is completed, dichloromethane is used for extraction, the organic phase is dried with anhydrous sodium sulfate, and then vacuum distillation and petroleum ether recrystallization are carried out, so that the target product formula (2-2) is obtained, and the yield is 85%.

[0043] Example 1

[0044] The present embodiment provides a photoinitiator composition (I) which is composed of 1.5g of a monoacyl phosphine oxide compound and 1.5g of a bisacyl phosphine oxide compound, wherein the weight ratio of the monoacyl phosphine oxide compound and the bisacyl phosphine oxide compound is 1:1.

[0045] The monoacyl phosphine oxide compound is shown in formula (1-1), (CAS No.: 75980-60-8).

[0046] The bisacylphosphine oxide compound is shown in formula (2-1), (CAS No. 162881-26-7).

[0047] The ultraviolet light curable ink (one) prepared based on the photoinitiator composition (one) provided in the present example, each raw material and its proportion are as follows: by weight percentage, photo-curable monomer 55%, photo-curable diluent monomer 42%, photoinitiator 3%. Specifically:

[0048] The photo-curable monomer is o-phenylphenoxyethyl acrylate, purchased from Sigma-Aldrich.

[0049] The photo-curable diluent monomer is 1,3-butanediol dimethacrylate, purchased from Beijing Bailingwei Technology Co., Ltd.

[0050] The photoinitiator is the above-mentioned photoinitiator composition (one).

[0051] The preparation method of the above-mentioned ultraviolet light curable ink (one) is: the photo-curable monomer, the photo-curable diluent monomer, and the photoinitiator composition (one) are added to a brown reaction bottle under light-proof conditions according to the above-mentioned raw materials and their proportions, mixed uniformly, filtered, and the ultraviolet light curable ink (one) is obtained.

[0052] Example 2

[0053] The present example provides a photoinitiator composition (two) composed of 0.3g of a monoacylphosphine oxide compound and 3g of a bisacylphosphine oxide compound, wherein the weight ratio of the monoacylphosphine oxide compound to the bisacylphosphine oxide compound is 1:10.

[0054] The monoacylphosphine oxide compound is shown in formula (1-2), and its preparation process is described in detail in Preparation Example 1. The bisacylphosphine oxide compound is shown in formula (2-2), and its preparation process is described in detail in Preparation Example 2.

[0055] The ultraviolet light curable ink (two) prepared based on the photoinitiator composition (two) provided in the present example, each raw material and its proportion are as follows: by weight percentage, photo-curable monomer 70%, photo-curable diluent monomer 27%, photoinitiator 3%. Specifically:

[0056] The photo-curable monomer is 2-methyl-[1,1'-biphenyl]-4-acrylate, purchased from Sigma-Aldrich.

[0057] The photo-curable diluent monomer is 1,3-butanediol dimethacrylate, purchased from Beijing Bailingwei Technology Co., Ltd.

[0058] The photoinitiator is the above-mentioned photoinitiator composition (two).

[0059] The preparation method of the above-mentioned ultraviolet light curable ink (two) is as follows: the photopolymerizable monomer, the photopolymerizable diluent monomer, and the photoinitiator composition (two) are added into a brown reaction bottle under light-proof conditions according to the above-mentioned raw materials and their proportions, uniformly mixed, filtered, and then the ultraviolet light curable ink (two) is obtained.

[0060] Example 3

[0061] The present embodiment provides a photoinitiator composition (three) composed of 3g of a monoacyl phosphine oxide compound and 0.3g of a bisacyl phosphine oxide compound, wherein the weight ratio of the monoacyl phosphine oxide compound to the bisacyl phosphine oxide compound is 10:1.

[0062] Specifically, the monoacyl phosphine oxide compound is a structure of formula (1-2) in Preparation Example 1,

[0063] The bisacyl phosphine oxide compound is a structure of formula (2-1).

[0064] The ultraviolet light curable ink (three) prepared based on the photoinitiator composition (three) provided in the present embodiment, the raw materials and their proportions are as follows: by weight percentage, photopolymerizable monomer 40%, photopolymerizable diluent monomer 57%, and photoinitiator 3%. Specifically:

[0065] The photopolymerizable monomer is 4,4'-biphenylene diisobutyrate, purchased from Wuhan Yingnuo Pharmaceutical Technology Co., Ltd.

[0066] The photopolymerizable diluent monomer is hexanediol acrylate, purchased from Beijing Bailingwei Technology Co., Ltd.

[0067] The photoinitiator is the above-mentioned photoinitiator composition (three).

[0068] The preparation method of the above-mentioned ultraviolet light curable ink (three) is as follows: the photopolymerizable monomer, the photopolymerizable diluent monomer, and the photoinitiator composition (three) are added into a brown reaction bottle under light-proof conditions according to the above-mentioned raw materials and their proportions, uniformly mixed, filtered, and then the ultraviolet light curable ink (three) is obtained.

[0069] Comparative Example 1

[0070] Different from Example 1, in Comparative Example 1, the weight ratio of the monoacyl phosphine oxide compound to the bisacyl phosphine oxide compound is 20:1.

[0071] Comparative Example 2

[0072] Different from Example 1, in Comparative Example 2, the weight ratio of the monoacyl phosphine oxide compound to the bisacyl phosphine oxide compound is 1:20.

[0073] Performance test: The UV-curable inks obtained in Examples 1-3 and Comparative Examples 1-2 above were coated on a glass plate, with a film thickness of about 18 μm, and irradiated with a UV-LED ultraviolet lamp having a wavelength of 395 nm and an irradiation light intensity of 30 mW / cm 2 for 30 s.

[0074] 1. Surface dry effect: The surface curing condition was detected by finger touch method, and the coating surface appeared fingerprint indentation, indicated by o, indicating that the oxygen inhibition was overcome; indicated by x, indicating that there was significant surface oxygen inhibition. The coating surface appeared fingerprint indentation.

[0075] 2. Light curing rate: FT-IR (Nicolet iS50, Thermo-Fisher) was used to measure the absorption peak intensity of the UV-curable ink before and after curing at 1635 cm -1 (C=C) and 1720 cm -1 (C=O).

[0076] Light curing rate (%) = |1-(F / S)|x100;

[0077] Wherein, F is the ratio of the absorption peak intensity near 1635 cm -1 to the absorption peak intensity near 1720 cm -1 after curing; S is the ratio of the absorption peak intensity near 1635 cm -1 to the absorption peak intensity near 1720 cm -1 before curing.

[0078] 3. Pencil hardness: Mitsubishi electric pencil hardness tester (CT-PC2) and 6B-9H pencil were used to measure the pencil hardness. The pencil load on the sample was 500 grams, the pencil stretching angle was 45°, and the pencil stretching speed was 48 mm / min. When one or more times of scratch occurred after five times of evaluation, the measurement was performed using a pencil with the next lower pencil hardness, and when there was no scratch in all five times of evaluation, the maximum pencil hardness value was obtained.

[0079] 4. Yellowing resistance: The cured UV-curable ink was kept in a UV aging test box for 10 h, and the samples before and after light exposure were tested using a color difference meter. The ΔE was measured, and the smaller the ΔE, the stronger the yellowing resistance. Wherein, L, a, b (L represents lightness, a represents red-green color, and b represents yellow-blue color value). The color difference of the film before and after yellowing was calculated according to the following formula:

[0080]

[0081] In the above formula: ΔE-comprehensive deviation; ΔL-black and white deviation; Δa-red and green deviation; Δb-yellow and blue deviation.

[0082] The performance test results are shown in Table 1:

[0083] Table 1: Performance test results of the ultraviolet curable ink obtained in Examples 1-3 and Comparative Examples 1-2

[0084] tack-free effect photocuring rate / % hardness yellowing resistance example 1 ○ 97.5 2H 1.09 example 2 ○ 96.8 2H 1.14 example 3 ○ 96.7 2H 1.01 comparative example 1 × 93.5 H 1.21 comparative example 2 ○ 94.2 B 1.61

[0085] As can be seen from the results in Table 1, when the weight ratio of the monoacyl phosphine oxide compound and the bisacyl phosphine oxide compound is 1:(0.1-10) in the photoinitiator composition provided by the present application, the surface dryness is strong, the photocuring rate is high, and the hardness is excellent when irradiated by a 395nm wavelength, 30mW / cm 2 UV-LED ultraviolet lamp for 30s.

[0086] On the contrary, in Comparative Example 1, the weight ratio of the monoacyl phosphine oxide compound and the bisacyl phosphine oxide compound is 20:1, which is not within the weight ratio range provided by the present application, and the surface dryness of the coating after curing of the ultraviolet curable ink is poor, the photocuring rate is low, the hardness is low, and the yellowing resistance is poor. In Comparative Example 2, the weight ratio of the monoacyl phosphine oxide compound and the bisacyl phosphine oxide compound is 1:20, which is also not within the weight ratio range provided by the present application, although the surface dryness of the coating after curing of the ultraviolet curable ink is good, the photocuring rate is low, the hardness drops sharply (from 2H to B), and the yellowing resistance is even worse, and it is impossible to take into account the problems of low photocuring rate, slow curing rate, poor surface dryness, low hardness, and poor yellowing resistance of the ultraviolet curable ink during the curing process.

[0087] The above description is merely a specific implementation of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application.

[0088] It should be understood that the present application is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A UV-curable ink, characterized in that, The ink includes a photoinitiator composition, which accounts for 0.1-4% of the total weight of the UV-curable ink; it also includes a photocurable monomer, a photocurable diluent monomer, and additives, with the following weight percentages: photocurable monomer 10-80%, photocurable diluent monomer 10-75%, and additives 0-5%. The photoinitiator composition is composed of a first photoinitiator and a second photoinitiator mixed in a weight ratio of 1:(1 to 10); the first photoinitiator is a monoacylphosphine oxide compound, and the second photoinitiator is a diacylphosphine oxide compound; The structural formula of the monoacylphosphine oxide compound is shown in formula (1), and the structural formula of the diacylphosphine oxide compound is shown in formula (2): In equations (1) to (2), R1, R2, and R3 are each independently a substituted or unsubstituted aryl group.

2. The UV-curable ink according to claim 1, characterized in that, The structural formula of the monoacylphosphine oxide compound includes any one of formulas (1-1) to (1-3):

3. The UV-curable ink according to claim 1, characterized in that, The diacylphosphine oxide compound comprises at least one of the raw materials shown in formulas (2-1) to (2-3):

4. The UV-curable ink according to claim 1, characterized in that, The UV-curable ink is cured under light intensity of 10–100 mW / cm. 2 After being irradiated with a UV-LED lamp with a wavelength of 395nm, a coating of 1-20μm is obtained.

5. The UV-curable ink according to claim 1, characterized in that, The photocurable monomer includes at least one monomer containing a (meth)acrylate photocurable group.

6. The UV-curable ink according to claim 1, characterized in that, The photocurable dilutable monomer is C1 to C1. 30 Monofunctional (meth)acrylates of monohydric alcohols, C2 to C3 30 Di(meth)acrylates of diols, triols, tetraols or pentaols, C3 to C4 30 One or more of the tri(meth)acrylates of triols, tetraols or pentaols.

7. The UV-curable ink according to claim 1, characterized in that, The additives include one or more of the following: polymerization inhibitors, surfactants, antioxidants, heat stabilizers, defoamers, and leveling agents.

Images