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EP-4741463-A1 - UV CURABLE COMPOSITIONS AND INKS

EP4741463A1EP 4741463 A1EP4741463 A1EP 4741463A1EP-4741463-A1

Abstract

A UV curable composition containing a mixture of free radical polymerizable monomers and a APO photoinitiator according to formula (I): wherein R1 is selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group and an aryl group or a heteroaryl group; R2 and R3 are independently selected from an alkyl group and an alkoxy group; R4 is selected from a hydrogen, an alkyl group and an alkoxy group; X and Y are independently selected from an oxygen atom, a methylene group, a - C(=CH2)- group, and a carbon atom present in a group selected from a straight chain alkylene group, an alkenylene group, an arylene group, a heteroarylene group and a cycloalkylene group; L represents a divalent linking group selected from the group consisting of an unsubstituted alkylene group, an arylene group, a heteroarylene group, a cycloalkylene group, a substituted alkylene group substituted by one or more ether groups, a substituted alkylene group substituted by one or more substituents selected from the group consisting of an aryl group, a heteroaryl group, an arylene group, a heteroarylene group, a cycloalkylene group, an ester group, an amide group, an amine group, an ether group, a thioether group, a ketone group, an aldehyde group, a sulfoxide group, a sulfone group, a sulfonate ester group, a sulphonamide group, -Cl, -Br, -I, -OH, - SH, -CN and -NO 2 ; and wherein the UV curable composition is free of a photoinitiator including 2 monoacyl phosphine oxide moieties linked to each other via their acyl group and wherein the 2 monoacyl phosphine oxide moieties have a chemical structure differing in the phosphine oxide part. Cured products and inkjet printing methods with the radiation curable compositions are also disclosed.

Inventors

  • LOCCUFIER, JOHAN
  • ADRIAENSSENS, Yves

Assignees

  • AGFA NV

Dates

Publication Date
20260513
Application Date
20241106

Claims (14)

  1. A UV curable composition containing a mixture of free radical polymerizable monomers and a APO photoinitiator according to formula (I): wherein R1 is selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group and an aryl group or a heteroaryl group; R2 and R3 are independently selected from an alkyl group and an alkoxy group; R4 is selected from a hydrogen, an alkyl group and an alkoxy group; X and Y are independently selected from an oxygen atom, a methylene group, a -C(=CH2)- group, and a carbon atom present in a group selected from a straight chain alkylene group, an alkenylene group, an arylene group, a heteroarylene group and a cycloalkylene group; L represents a divalent linking group selected from the group consisting of an unsubstituted alkylene group, an arylene group, a heteroarylene group, a cycloalkylene group, a substituted alkylene group substituted by one or more ether groups, a substituted alkylene group substituted by one or more substituents selected from the group consisting of an aryl group, a heteroaryl group, an arylene group, a heteroarylene group, a cycloalkylene group, an ester group, an amide group, an amine group, an ether group, a thioether group, a ketone group, an aldehyde group, a sulfoxide group, a sulfone group, a sulfonate ester group, a sulphonamide group, -Cl, -Br, -I, -OH, -SH, -CN and -NO 2 ; and wherein the UV curable composition is free of a photoinitiator including 2 monoacyl phosphine oxide moieties linked to each other via their acyl group and wherein the 2 monoacyl phosphine oxide moieties have a chemical structure differing in the phosphine oxide part.
  2. The UV curable composition according to claim 1, wherein the APO photoinitiator is a photoinitiator according to formula (II):
  3. The UV curable composition according to claim 1 or 2, wherein R1 is a C 1 -C 4 -alkyl group.
  4. The UV curable composition according to claim 1, wherein the APO photoinitiator is selected from the group consisting of: and
  5. The UV curable composition according to any one of claims 1 to 4, wherein the mixture of free radical polymerizable monomers contains at least one of N-vinyl caprolactam, vinyl methyl oxazolidinone and (2'-vinyloxyethoxy)ethyl acrylate.
  6. The UV curable composition according to any one of claims 1 to 5 containing a colorant.
  7. A UV curable inkjet ink including a UV curable composition according to any one of claims 1 to 6.
  8. The UV curable inkjet ink according to claim 7 having a mixture of free radical polymerizable monomers comprising of: a) 7 - 70 wt% of 2- (2'-vinyloxyethoxy)ethyl acrylate b) 1 - 65 wt% of one or more polymerizable compounds selected from the group consisting of monofunctional acrylates and difunctional acrylates; and c) 0 - 55 wt% of one or more polymerizable compounds selected from the group consisting of trifunctional acrylates, tetrafunctional acrylates, pentafunctional acrylates and hexafunctional acrylates.
  9. A UV curable inkjet ink set including one or more UV curable inkjet inks according to claim 7 or 8.
  10. The UV curable inkjet ink set according to claim 9 which includes: - a cyan UV curable inkjet ink containing a beta-copper phthalocyanine pigment; - a red or magenta UV curable inkjet ink containing a pigment selected from the group consisting of C.I. Pigment Red 57/1, C.I. Pigment Red 122, C.I. Pigment Red 144, C.I. Pigment Red 170, C.I. Pigment Red 175, C.I. Pigment Red 176, C.I. Pigment Red 187, C.I. Pigment Red 188, C.I. Pigment Red 202, C.I. Pigment Red 207, C.I. Pigment Red 242, C.I. Pigment Red 254, C.I. Pigment Red 272, C.I. Pigment Violet 19, and mixed crystals thereof; - a yellow UV curable inkjet ink containing a pigment selected from C.I. Pigment Yellow 74 C.I. Pigment Yellow 83, C.I. Pigment Yellow 97, C.I. Pigment Yellow 110, C.I. Pigment Yellow 120, C.I. Pigment Yellow 139, C.I. Pigment Yellow 138, C.I. Pigment Yellow 150, C.I. Pigment Yellow 151, C.I. Pigment Yellow 154, C.I. Pigment Yellow 155, C.I. Pigment Yellow 175, C.I. Pigment Yellow 180, C.I. Pigment Yellow 181, C.I. Pigment Yellow 194, C.I. Pigment Yellow 213, C.I. Pigment Yellow 214 and mixed crystals thereof; and - a black UV curable inkjet ink containing a carbon black pigment; optionally complemented by a white UV curable inkjet ink and/or a colourless UV curable inkjet ink.
  11. A printed article comprising a cured composition derived from the UV curable composition of any one of claims 1 to 10.
  12. The printed article of claim 11 selected from printed packaging, printed leather articles, and printed interior decoration articles.
  13. The printed article of claim 11 or 12 obtained using inkjet printing technology.
  14. An inkjet printing method comprising the steps of: a) jetting an image with a UV curable inkjet ink according to any one of claims 1 to 13 on a substrate; and b) curing the jetted image by UV light emitting diodes having an emission wavelength of 360 nm or larger.

Description

Technical Field The present invention relates to UV curable compositions, especially to UV curable (inkjet) inks. Background Art State of the art UV curing technology is based on LED curing, operating for the majority of the systems at 395 nm. The number of industrially available photoinitiators suitable for curing at such wavelength is rather limited. A combination of thioxanthones and amine-based co-initiators gives high curing speed at 395 nm, but results in considerable yellowing of the cured layers, making it unsuitable for UV curable compositions such as varnishes and white inks. Acyl phosphine oxides have found to be very suitable for 395 nm LED curing without these photo-yellowing problems. However, the number of industrially available acyl phosphine oxides is limited and there are increasing concerns on their toxicology. The applicability of bis-acyl phosphine oxides is often limited by their solubility in UV curable compositions, leading to mono-acyl phosphine oxides as particularly preferred photoinitiators for 395 nm radiation curable inkjet inks, further narrowing the options. On top of the toxicological concerns and limitations in formulation latitude, as good as all available acyl phosphine oxide initiators are prone to migration and generate volatile degradation products, leading to a smell. Especially smell is the limiting factor for a lot of large volume applications such as indoor decoration. The application scope would further widen if on top the migration problem can be solved. Over the last decade, there has been a considerable research activity in search of alternatives for the industrially available acyl phosphine oxides, targeting at solving the above-mentioned problems. Functionalization on the mesityl fragment of acyl phosphine oxide photoinitiators as disclosed in WO 2014/051026 (FUJIFILM) , WO 2014/129213 (FUJIFILM) , WO 2019/243039 (AGFA) and WO 2022/106099 (AGFA) is a potential solution to solve the problem of volatile degradation products. WO 2019/243039 (AGFA) discloses urea and oxalyl amide functionalized acyl phosphine oxides, where additional supramolecular interactions are used to further control volatility of the degradation products. In WO 2022/106099 (AGFA) , additional tertiary amines are incorporated into the structure to further optimize the surface cure of printed images, thereby preventing the migration of skin-irritating acrylates. However, the use of supramolecular interactions often limits the formulation latitude which had to be controlled by additional structural elements leading to an increase in molecular weight per photoinitiating moiety, impacting both the viscosity of the formulation and the curing speed for a same weight ratio in the formulation. For maintaining the curing speed on an acceptable level, higher amounts of the photoinitiator have to be added further impacting the viscosity. The impact on viscosity limits the applicability of the disclosed photoinitiators in inkjet applications, where viscosity of the formulation is particularly critical. Several inkjet applications require a high chroma in the colored prints. Gloss is a particularly important aspect of colored images. Improvements in gloss lead to higher chroma in colored prints and a broader dynamic range in tonality (darker blacks and richer shadows), which in its turn brings a larger color gamut. An ink set with a larger color gamut generally has a lower ink consumption, because less ink needs to be laid down to match the same color effects. Enhancing gloss is frequently achieved by altering the monomer composition, as demonstrated in US 2020254755 A (SEIKO EPSON). However, choosing specific monomers often leads to trade-offs in other properties. There is still a need for UV curable compositions exhibiting high curability at 395 nm, no photoyellowing and less toxicological concerns or photoinitiator solubility issues, while delivering cured products with improved gloss, minimal smell and minimal migration problems. Summary of invention It has surprisingly been found that the above-mentioned problems for UV curable compositions can be largely solved by using a mixture of free radical curable monomers and a specific photoinitiator. An object of the present invention is to provide a UV curable composition, such as an ink jet ink, optimized for gloss. Another object of the present invention is to provide a cured product with improved gloss and minimal smell or migration problems. These and other objects and advantages of the present invention will become apparent from the detailed description given below. Description Definitions The term "APO photoinitiator" is herein used as an abbreviation for an acyl phosphine oxide photoinitiator. The term "alkyl group" means a functional group with all variants possible for each number of carbon atoms in the alkyl group, i.e. for one carbon atom: methyl, for two carbon atoms: ethyl, for three carbon atoms: n-propyl and isopropyl; for four carbon atoms