Epoxy-based UV-vis curable sealant composition

Abstract

The present invention relates to the field of UV-VIS curable compositions comprising: a) 20 to 50 wt.% of at least one aromatic epoxide monomer or aromatic epoxide oligomer or a mixture thereof; b) 4 to 20 wt.% of at least one epoxidized polyene; c) 15-35 wt.% of at least one organic or inorganic filler or a mixture thereof; d) 0.1 to 10 wt.% of at least one cationic photoinitiator; e) 0-30 wt.% of at least one cationically curable cyclic compound different from a) and b); f) 0-30 wt.% of at least one additional additive selected from the group consisting of photosensitizers, surfactants, adhesion promoters and mixtures thereof, wherein additive f) is different from components a) to e); and wherein the UV-VIS curable sealant composition has a viscosity of from about 60000 m * Pas to about 120000 m * Pas at 25 DEG C; and wherein the weight percentages are based on the total weight of the UV-VIS curable sealant composition. The invention also relates to an inkjet printhead comprising said composition and a method of making the same.

Description

Technical Field

[0001] The present invention relates to the technical field of UV-VIS curable sealant compositions that can be used to protect exposed electrical contacts on inkjet printheads, uses thereof, and methods for making inkjet printhead assemblies containing the UV-VIS curable sealant compositions. Background Art

[0002] Typical inkjet printhead cartridges as described in patent EP 1896262 B1 (see FIG1 therein) or FIG1 are made of a printhead jetting assembly consisting of a printhead chip bonded to a flexible printed circuit. The printhead silicon chip, also known as a silicon ejector group, houses electrical and hydraulic components to direct ink to each ejection site, energizing it as needed to produce ink droplets for printing. A nozzle plate is applied to the top surface of the chip to provide nozzles for ink jetting. The entire jetting assembly is in turn bonded to an ink cartridge comprising an ink container closed by a lid. Suitable ink slots are present in the cartridge body to allow ink to reach the printhead chip and, depending on the printhead layout, are machined into the chip or into the microfluidic circuit from the edge of the chip.

[0003] The silicon chip and the flexible circuit are connected to each other through electrical contacts or leads. A UV-VIS curable sealant composition can be used to cover these otherwise exposed areas (see Figure 2). The sealant must accurately seal all uncovered portions near the bonding area, i.e., the chip solder joints and leads. In order to effectively seal, the sealant should ensure good contact with the different materials used in the print head components, such as conductors made of different metals, silicon and silicon compounds, polymers, and adhesives. It should surround all uncovered portions and completely fill any gaps or depressions in the surface topography. At the same time, the sealant shape should remain stable, and its surface should remain confined to the area where it is dispensed, without spreading to the surrounding area. In other words, the sealant should maintain its shape after dispensing and needs to have the correct rheology to do so. In this way, the UV-VIS curable sealant composition does not cover the critical area near the nozzle, maintains considerable thickness and robustness, and allows the component (see Figure 3) to be quickly moved between the dispensing station and the UV-VIS curing station without substantially losing its dispensed pre-cured form.

[0004] During normal operation of the printhead in an inkjet printer, the sealant comes into contact with the ink dispensed from the nozzles.Therefore, there is always a risk that the sealant composition may become damaged due to this normal exposure and lose its integrity over time.

[0005] When the ink is solvent-based, the sealant is subjected to strong chemical exposure in the solvent environment throughout the life of the printhead. This results in a "swelling" phenomenon of the sealant, which can lead to a loss of integrity of the sealant material.

[0006] Furthermore, the long-term presence or deposition of ink on the front of the printhead, not only for solvent-based inks but also for water-based inks, can be detrimental to the electrical integrity of the printhead. Ink accumulated on the front of the printhead due to printing activity can remain there for weeks or months without being cleaned. This persistence can lead to separation of the UV-VIS-curable sealant composition and / or corrosion of the electrical contacts, potentially leading to failure of the printhead assembly. Consequently, regular replacement becomes necessary, imposing additional costs on the user.

[0007] Therefore, there is a need to provide a UV-VIS curable sealant composition suitable for protecting exposed electrical contacts on inkjet printheads that ensures high adhesion to various surfaces and provides good protection for electrical components exposed to ink, while overcoming the various problems discussed herein. In particular, the sealant composition should have good thixotropy and suitable viscosity to exhibit the desired dispensability and form stability via pneumatic or cochlear systems. The composition should be compatible with manufacturing processes and should exhibit high chemical resistance, adhesion, and good flexibility to provide a durable sealing means for electrical components, especially after ink has been in front of the printhead for an extended period of time. Summary of the Invention

[0008] Problems to be solved by the invention

[0009] In a first aspect, the present invention relates to a UV-VIS curable sealant composition comprising:

[0010] a) 25-40 wt.% of at least one aromatic epoxide monomer or aromatic epoxide oligomer or a mixture thereof;

[0011] b) 4 to 20 wt.% of at least one epoxidized polyene;

[0012] c) 20-35 wt.% of at least one organic filler or inorganic filler or a mixture thereof;

[0013] d) 0.1-10 wt.% of at least one cationic photoinitiator;

[0014] e) 0-30 wt.% of at least one cationically curable cyclic compound different from a) and b);

[0015] f) 0.05-3 wt.% of a nonionic surfactant;

[0016] g) 0-30 wt.% of at least one further additive selected from the group consisting of photosensitizers, adhesion promoters and mixtures thereof, wherein additive g) is different from components a) to f);

[0017] wherein the UV-VIS curable sealant composition has a viscosity at 25° C. of about 60,000 m·Pas to about 120,000 m·Pas; and

[0018] The weight percentages are based on the total weight of the UV-VIS curable sealant composition.

[0019] In a second aspect, the present invention relates to an inkjet printhead comprising a UV-VIS curable sealant composition as described herein in an at least partially cured state.

[0020] In a second aspect, the present invention relates to a method of encapsulating electrical contacts on an inkjet printhead, comprising:

[0021] a) providing a UV-VIS curable sealant composition as described herein;

[0022] b) providing an assembly comprising a flexible circuit and a silicon chip;

[0023] c) dispensing a UV-VIS curable sealant composition onto electrical contacts connecting the silicon chip to the flexible circuit; and

[0024] d) curing or at least partially curing the UV-VIS curable sealant composition using a UV-VIS light source.

[0025] In a final aspect, the present invention relates to the use of a UV-VIS curable sealant composition as described herein for the manufacture of an inkjet printhead as described herein.

[0026] It has been unexpectedly discovered that the UV-VIS curable sealant compositions described herein provide at least the following advantages:

[0027] - Chemical resistance or stability to various inks after curing, especially solvent-based inks;

[0028] -Good adhesion and wettability to various substrates of inkjet print heads such as Kapton, gold, silicon (carbide) or nickel;

[0029] - Suitable assignability to pneumatic or cochlear systems;

[0030] -Good thixotropy and visibility once dispensed through an optical detector system;

[0031] - Fast and efficient curing temperatures and performance compatible with high-speed manufacturing of printhead systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 shows a schematic representation of an inkjet printhead cartridge (1). The cartridge (1) houses a printhead chip (2) provided with a nozzle plate (3) on its surface. Line BB shown in the figure corresponds to the direction of relative movement between the print medium and the printhead during printing. Ink droplets are ejected from the nozzles with the aid of electrical signals sent from the printer to the printhead chip: a flexible printed circuit (4) is used for this purpose. Polyimide is typically used for the flexible circuit substrate. A window is formed on the surface of the flexible printed circuit to allow the printhead chip to protrude, so that the flexible printed circuit surrounds the chip. Conductive metal traces of the flexible printed circuit extend from the edge of the window to serve as leads for electrical contact with the chip. Contact areas (5) are provided for electrical communication with the printer on the other side of the flexible circuit. The electrical connection between the leads and the chip is ensured by a suitable bonding process, such as tape automated bonding (TAB). The chip is provided with a plurality of bonding pads near the periphery to allow the bonding process, with the leads accommodated on their surface: therefore, the pad surfaces must be freely accessible to the bonding tool and not covered by any layer until the bonding process is completed. Typically, though not in all cases, the solder joints are located near the short sides of the printhead die.

[0033] Figure 2 shows a cross-sectional view of a print head chip (2) and a flexible circuit and a cured or at least partially cured UV-VIS curable sealant composition (16). The view is along a direction perpendicular to line BB. The chip (2) is a silicon substrate having a conductive layer, a resistive layer, a dielectric layer and a protective layer on its surface, which is covered by a patterned barrier layer (6), on which the hydraulic print head circuit with ejection chambers (7) is based. The barrier layer is usually a polymer, which is covered by a nozzle plate (3), the nozzles of which allow the ejection of ink droplets (8). The bonding pads (9) are placed near the side of the chip that accommodates the leads (10) protruding from the flexible printed circuit (4), the leads (10) being bonded to the pad surface. The leads are extensions of the conductive traces (11) of the flexible printed circuit. A suitable adhesive layer (12) allows the flexible printed circuit to be fastened to the box body. It also functions as an insulating protector, preventing the conductive traces (11) from mechanical or electrical contact with any components or materials that could cause damage or short circuits. The solder joint surface must be uncovered to allow contact between the conductors during the bonding process. Therefore, the barrier layer is removed in the solder joint area during patterning: only the portion behind the solder joint (13) is left to prevent mechanical contact between the substrate and the leads. During printing, the front of the chip is subjected to ink contact and sometimes also to a wiping action performed by a suitable scraper. Therefore, once the bonding stage is completed, the solder joint area and the leads must be covered with some sealing UV-VIS curing sealant material (16) to protect the electrical connection, avoid mechanical damage, short circuits and provide chemical or electrochemical resistance.

[0034] Figure 3 shows the process steps of dispensing a UV-VIS curable sealant composition with a dispensing station (18) (left) and curing or at least partially curing the composition with a curing station (20) (right). After bonding, the chip and flexible printed circuit assembly (17) is transferred to the dispensing station (18), where a certain amount (19) of the uncured UV-VIS curable sealant composition is delivered to each area to be protected. The assembly (17) with the dispensed UV-VIS curable sealant undergoes a rapid movement to the curing station (20), where a UV-VIS light source (21) cures the UV-VIS curable sealant. DETAILED DESCRIPTION

[0035] definition

[0036] The following definitions are intended to clarify the meaning of terms discussed in the specification and recited in the claims.

[0037] As used herein, the indefinite article "a" means one as well as more than one and does not necessarily limit the referenced noun to a singular.

[0038] As used herein, the term "about" means that the amount or value in question can be the specified value or some other value nearby. The wording is intended to convey that similar values ​​within the range of ±5% of the specified value promote similar results or effects according to the present invention.

[0039] As used herein, the term "UV-VIS" is intended to mean radiation having wavelength components in the UV-VIS portion of the electromagnetic spectrum; typically 200 nm to 420 nm.

[0040] As used herein, the term "at least one" is intended to define one or more than one, such as one or two or three.

[0041] As used herein, the term "and / or" means that all or only one of the elements of the group may be present. For example, "A and / or B" should mean "only A, or only B, or both A and B." In the case of "only A," the term also encompasses the possibility that B is not present, i.e., "only A, but not B."

[0042] As used herein, the term "comprising" is intended to be non-exclusive and open-ended. Thus, for example, a UV-VIS curable sealant composition comprising compound A may include other compounds in addition to A. However, the term "comprising" also encompasses the more restrictive meanings of "consisting essentially of" and "consisting of" as specific embodiments thereof, such that, for example, a "UV-VIS curable sealant composition comprising A, B, and optionally C" may also consist (essentially) of A and B or (essentially) of A, B, and C.

[0043] When the present description refers to “preferred” embodiments / features, combinations of “preferred” embodiments / features shall also be considered disclosed, as long as these combinations make technical sense.

[0044] The term "wt. %" means the amount of the component based on the total weight of the UV-VIS curable sealant composition.

[0045] The UV-VIS curable sealant composition as described herein comprises:

[0046] a) 20-50 wt.% of at least one aromatic epoxide monomer or aromatic epoxide oligomer or a mixture thereof;

[0047] b) 4 to 20 wt.% of at least one epoxidized polyene;

[0048] c) 15-35 wt.% of at least one organic filler or inorganic filler or a mixture thereof;

[0049] d) 0.1-10 wt.% of at least one cationic photoinitiator;

[0050] e) 0-30 wt.% of at least one cationically curable cyclic compound different from a) and b);

[0051] f) 0-30 wt.% of at least one additional additive selected from the group consisting of photosensitizers, surfactants, adhesion promoters, and mixtures thereof, wherein additive f) is different from components a) to e);

[0052] wherein the UV-VIS curable sealant composition has a viscosity at 25° C. of 60,000 m·Pas to about 120,000 m·Pas; and

[0053] The weight percentages are based on the total weight of the UV-VIS curable sealant composition.

[0054] In some examples, the UV-VIS curable sealant composition described herein comprises:

[0055] a) 25-40 wt.% of at least one aromatic epoxide monomer or aromatic epoxide oligomer or a mixture thereof;

[0056] b) 5-15 wt.% of at least one epoxidized polyene;

[0057] c) 20-35 wt.% of at least one organic filler or inorganic filler or a mixture thereof;

[0058] d) 1-5 wt.% of at least one cationic photoinitiator;

[0059] e) 0-30 wt.% of at least one cationically curable cyclic compound different from a) and b);

[0060] f) 0-30 wt.% of at least one further additive selected from the group consisting of photosensitizers, surfactants, adhesion promoters and mixtures thereof, wherein additive f) is different from components a) to e).

[0061] The UV-VIS curable sealant composition comprises at least one aromatic epoxide monomer or aromatic epoxide oligomer or a mixture thereof (a) as described herein. As used herein, an aromatic epoxide monomer or aromatic epoxide oligomer refers to a component containing a reactive or curable epoxy group and an aromatic moiety. The at least one aromatic epoxide monomer and aromatic epoxide oligomer independently may have an epoxide functionality (the number of epoxide groups per molecule) of greater than 2 to about 8; about 2.1 to about 5; about 2.3 to about 4; about 2.5 to about 3.5; or about 2. The aromatic epoxide monomer or oligomer may be present in the composition in an amount of about 20 to about 50 wt.%, preferably about 30 to about 40 wt.%, even more preferably about 35 to about 40 wt.%, or even about 25 to about 40 wt.%.

[0062] The aromatic epoxide monomers or aromatic epoxide oligomers may be derived from mononuclear phenols, for example from resorcinol or hydroquinone, or may be based on polynuclear phenols, for example bis-(4-hydroxyphenyl)methane (bisphenol F), 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), or on the condensation products of phenols or cresols with formaldehyde obtained under acidic conditions, generally known as novolacs, in particular phenol novolacs and cresol novolacs.

[0063] Suitable commercially available aromatic epoxide monomers or aromatic epoxide oligomers are, but are not limited to, BISPHEROL A EPOXY LIQUID RESIN from Palmer Holland. GY series, as bisphenol A epoxy solid resin CT and GT series, as bisphenol F epoxy liquid GY and PY series, ECN series epoxy cresol novolac, EPN series epoxy phenol novolac, DEN series epoxy novolac resin.

[0064] In a preferred embodiment, the aromatic epoxide monomer or aromatic epoxide oligomer is an epoxy novolac resin.

[0065] The UV-VIS curable sealant composition comprises at least one cationic photoinitiator d) as described herein, which is an onium salt as described herein, in an amount of about 0.1 to about 10 wt.%, preferably about 3 to about 12 wt.%, more preferably about 4 to about 10 wt.%, and even more preferably about 1 to about 5 wt.%. The onium salt as described herein is preferably selected from the group consisting of (di)azonium salts, oxonium salts, (diaryl)iodonium salts, sulfonium salts, and mixtures thereof, more preferably selected from the group consisting of oxonium salts, iodonium salts, sulfonium salts, and mixtures thereof, and even more preferably selected from the group consisting of iodonium salts, sulfonium salts, and mixtures thereof.

[0066] The iodonium salts described herein have a cationic portion and an anionic portion, wherein the anionic portion is preferably BF4 - 、B(C6F5)4 - PF6 - 、AsF6 - 、SbF6 - or CF3SO3 - , more preferably SbF6 - or PF6 - , and wherein the cationic moiety is preferably an aromatic iodonium ion, more preferably an iodonium ion comprising two aromatic groups, wherein the two aromatic groups may be independently substituted with one or more alkyl groups (e.g., methyl, ethyl, isobutyl, tert-butyl, etc.), one or more alkoxy groups, one or more nitro groups, one or more halogen-containing groups, one or more hydroxyl groups, or a combination thereof. Particularly suitable examples of iodonium salts for use in the present disclosure are commercially available from IGM Resins under the names Omnicat 250 and 440 and from Lambson under the name SpeedCure 938.

[0067] The sulfonium salts described herein have a cation portion and an anion portion, wherein the anion portion is preferably BF4 - 、B(C6F5)4 - PF6 - 、(PF 6-m (C n F 2n-1 ) m ) - (wherein m is an integer from 1 to 5, and n is an integer from 1 to 4), AsF6 - 、SbF6 - CF3SO3 - , perfluoroalkylsulfonate or pentafluorohydroxyantimonate, more preferably SbF6 - or PF6 -, and wherein the cationic portion is preferably an aromatic sulfonium ion, more preferably a sulfonium ion comprising two or more aromatic groups, wherein the two or more aromatic groups may be independently substituted with one or more alkyl groups (e.g., methyl, ethyl, isobutyl, tert-butyl, etc.), one or more alkoxy groups, one or more aryloxy groups, one or more halogen-containing groups, one or more hydroxyl groups, or a combination thereof.

[0068] Suitable examples of the sulfonium ion containing two or more aromatic groups include, but are not limited to, triarylsulfonium ion, diphenyl[4-(phenylthio)phenyl]sulfonium ion, bis[4-(diphenylsulfonium)phenyl]sulfonium ion, triphenylsulfonium ion, and tris[4-(4-acetylphenyl)sulfanylphenyl]sulfonium ion.

[0069] In a preferred embodiment, the at least one cationic photoinitiator d) is selected from the group consisting of triphenylsulfonium salts, diazonium salts, diaryliodonium salts, ferrocenium salts, metallocene compounds and mixtures thereof.

[0070] Suitable commercially available cationic photoinitiators d) are, but are not limited to, Irgacure PAG 290 (BASF), diphenyliodonium hexafluorophosphate (Sigma-Aldrich), diphenyliodonium hexafluoroantimonate (Sigma-Aldrich), triarylsulfonium hexafluorophosphate (Sigma Aldrich) and / or triphenylsulfonium trifluoromethanesulfonate (Sigma-Aldrich), aromatic iodonium salts and aromatic sulfonium salts, for example triarylsulfonium hexafluorophosphate (CYRACURE TM UVI-6992, Dow Chemical Company), triarylsulfonium hexafluoroantimonate (CYRACURE TMUVI-6976, Dow Chemical Company), and arylsulfonium hexafluorophosphate (ESACURE 1064, Lamberti), arylsulfonium hexafluorophosphate (ESACURE 1064, Lamberti), bis-(4-dodecylphenyl)iodonium hexafluoroantimonate in glycidyl ether from Arkema (SpeedCure 937), bis-(4-tert-butylphenyl)-iodonium hexafluorophosphate (SpeedCure 938), bis-(4-tert-butylphenyl)-iodonium hexafluorophosphate (SpeedCure 939), (sulfanediyldiphenyl-4,1-diyl)bis(diphenylsulfonium)bis(hexafluoroantimonate) in propylene carbonate (SpeedCure 976), and (sulfanediyldiphenyl-4,1-diyl)bis(diphenylsulfonium)bis(hexafluoroantimonate) in propylene carbonate (SpeedCure 992), diphenyl[(phenylthio)phenyl]sulfonium (PAG-20001), mixed triarylsulfonium hexafluoroantimonate PAG-20002 or PAG-21608 from Aalchem.

[0071] Other examples of useful photoinitiators can be found in standard textbooks, such as "Chemistry & Technology of UV & EB Formulation for Coatings, Inks & Paints", Volume III, "Photoinitiators for Free Radical Cationic and Anionic Polymerization", 2nd edition, J. V. Crivello & K. Dietliker, edited by G. Bradley, published jointly by John Wiley & Sons and SITA Technology Limited in 1998.

[0072] The UV-VIS curable sealant composition comprises at least one epoxidized polyene as described herein in an amount of about 4 to about 20 wt.%, preferably about 5 to about 15 wt.%. As used herein, the expression epoxidized polyene b) refers to epoxidized poly-1,3-dienes such as polybutadiene and polyisoprene, or to epoxidized copolymers having a butadiene portion or an isoprene portion. Examples of epoxidized polyenes include epoxidized polybutadiene, epoxidized polyisoprene, epoxidized copolyenes having a butadiene portion, and epoxidized copolyenes having an isoprene portion. The number average molecular weight (Mn) of the epoxidized polyene is preferably 500-50,000, more preferably 1,000-5,000. When the molecular weight exceeds 50,000, the epoxidized product may not liquefy and may result in poor working efficiency, while when the molecular weight is less than 500, the epoxidized product may not be used as a satisfactory flexibility imparting agent. The number average molecular weight can be determined by a suitable gel permeation chromatography (GPC) method known to those skilled in the art.

[0073] In a preferred embodiment, the epoxidized polyene is epoxidized polybutadiene.

[0074] The epoxidized polyene b) described herein may have epoxy groups in the molecule and may also have hydroxyl groups. The hydroxyl groups may originate from the polyene or may be formed during the epoxidation of the polyene. Among the epoxidized polyenes disclosed herein, hydroxyl-terminated epoxidized polybutadiene has superior compatibility with other epoxy resins compared to hydrogen-terminated epoxidized polybutadiene if they have the same oxirane oxygen content.

[0075] Suitable commercially available epoxidized polyenes are, but are not limited to, EPOLEAD PB3600 (Daicel), epoxy-functionalized and hydroxyl-terminated polybutadiene (CAS: 129288-65-9, from Sigma Aldrich).

[0076] The UV-VIS curable sealant composition may comprise an epoxy-containing component which may be an aliphatic epoxide or a cycloaliphatic epoxide or a mixture thereof. If present, the epoxy-containing compound is different from components a) and b).

[0077] The alicyclic epoxides described herein may be difunctional or polyfunctional. Preferably, the alicyclic epoxides independently contain at least one cyclohexane group and at least two epoxide groups. Preferred alicyclic epoxides contain more than one cyclohexane epoxide group and have structural formula (I):

[0078]

[0079] wherein X is selected from a single bond and a divalent group containing more than one atom.

[0080] According to one embodiment, X is a divalent hydrocarbon group which is a linear or branched alkylene group containing 1 to 18 carbon atoms, wherein examples of the linear or branched alkylene group include, but are not limited to, methylene, methylmethylene, dimethylmethylene, ethylene, propylene, and trimethylene.

[0081] According to one embodiment, X is a divalent alicyclic hydrocarbon group or a cycloalkylene group, such as 1,2-cyclopentylene, 1,3-cyclopentylene, cyclopentylidene group, 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene and cyclohexylidene group.

[0082] According to one embodiment, X is a divalent group containing one or more oxygen-containing linking groups, wherein the oxygen-containing linking groups are -CO-, -O-CO-O-, -COO- and -O-. According to one embodiment, preferred epoxy derivatives containing more than one cyclohexane oxide group and having the structural formula (I), wherein X is a divalent group containing one or more oxygen-containing linking groups, wherein the oxygen-containing linking groups are -CO-, -O-CO-O-, -COO-, -O-, have the structural formula (II), (III) or (IV):

[0083]

[0084] It corresponds to 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, wherein R1-R9 are independently hydrogen, or a linear or branched alkyl group containing 1-10 carbon atoms and preferably containing 1-3 carbon atoms (such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl and decyl), and preferred alicyclic epoxides with structural formula (II) are 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methyl-cyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, 3,4-epoxy-2-methyl-cyclohexylmethyl-3,4-epoxy-2-methyl-cyclohexanecarboxylate and 3,4-epoxy-4-methyl-cyclohexylmethyl-3,4-epoxy-4-methyl-cyclohexanecarboxylate,

[0085]

[0086] It corresponds to an alicyclic diepoxide ester of a dicarboxylic acid, wherein R1-R9 are independently hydrogen, or a linear or branched alkyl group containing 1 to 10 carbon atoms and preferably containing 1 to 3 carbon atoms (such as methyl, ethyl, n-propyl, isopropyl, butyl, hexyl, octyl and decyl), and A is a valence bond, or a linear or branched divalent hydrocarbon group containing usually 1 to 10 carbon atoms and preferably containing 3 to 8 carbon atoms, such as an alkylene group (such as trimethylene, tetramethylene, hexamethylene and 2-ethylmethylene). hexyl) and alicyclic groups (such as 1,4-cyclohexane, 1,3-cyclohexane and 1,2-cyclohexane); preferably, the alicyclic diepoxide ester of the dicarboxylic acid having the structural formula (III) is bis(3,4-epoxycyclohexylmethyl) adipate, bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate, bis(3,4-epoxycyclohexylmethyl) oxalate, bis(3,4-epoxycyclohexylmethyl) pimelate and bis(3,4-epoxycyclohexylmethyl) sebacate;

[0087]

[0088] wherein R1-R9 are independently hydrogen or a straight or branched hydrocarbon group containing 1 to 3 carbon atoms; a preferred example of an alicyclic diepoxide having the structure (IV) is 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-m-dioxane.

[0089] According to one embodiment, the cycloaliphatic epoxides described herein have the structural formula (V) or (VI):

[0090]

[0091] The cycloaliphatic epoxides described herein may be hydroxyl modified or (meth)acrylate modified. Examples are commercially available from Daicel Corp. under the names Cyclomer A400 (CAS: 64630-63-3) and Cyclomer M100 (CAS: 82428-30-6), or from TetraChem / Jiangsu as TTA 15 and TTA 16, from Daicel as Celloxide 2021P, and from Dow Chemical as CYRACURE TM 6110UVR、CYRACURE TM6105UV is commercially available from Sigma Aldrich as 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate or as ACHWL CER 4221 from PHLEX TEK, which is commercially available from Arkema as 7-oxabicyclo[4.1.0]hept-3-ylmethyl 7-oxabicyclo[4.1.0]heptane-3-carboxylate (UviCure S105).

[0092] The UV-VIS-curable sealant composition includes at least one filler c). The filler may be an organic filler, an inorganic filler, or a mixture thereof. The at least one filler is preferably present in an amount of about 15 to about 35 wt.%, more preferably about 20 to about 25 wt.%. In a preferred embodiment, the filler has a refractive index at 400 nm of about 1.2 to about 1.8, preferably about 1.3 to about 1.6, and / or a particle size of about 5 to about 15 μm, preferably about 5 to about 9 μm. When the refractive index of the filler is within the above-defined range, the UV-VIS-curable sealant composition exhibits suitable transparency to the UV-VIS radiation used during the curing process.

[0093] The refractive index of the at least one filler c) can be measured using ISO 489: 2022, while the particle size can be determined by laser diffraction using ISO 13320: 2020. In addition, the refractive index of various materials is also available from refractiveindex.info.

[0094] The inorganic filler can be preferably selected from the group consisting of carbon fiber, talc, mica (muscovite), wollastonite, calcined clay, china clay, kaolin, carbonates (e.g. calcium carbonate, sodium aluminum carbonate), silicates (e.g. magnesium silicate, aluminum silicate), sulfates (e.g. magnesium sulfate, barium sulfate), titanates (e.g. potassium titanate), alumina hydrate, silicon dioxide, fumed silica, montmorillonite, graphite, anatase, rutile, bentonite, vermiculite, zinc white, zinc sulfide, wood flour, quartz powder, natural fibers, synthetic fibers, glass, and mixtures thereof. Preferred inorganic fillers can be selected from the group consisting of glass, carbonates, talc, and mixtures thereof. A particularly preferred inorganic filler is talc.

[0095] Preferably, filler c) is an organic filler. The organic filler can be selected from the group consisting of acrylic resins produced from at least acrylates or methacrylates, copolymers thereof with styrene (i.e., styrene-acrylic resins), modified rosin resins, terpene resins, modified terpene resins, polyester resins, polyamide resins, epoxy resins, vinyl chloride resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, polyacrylic polyols, polyvinyl alcohol, polyurethanes, hydrogenated petroleum resins, and mixtures thereof. Advantageously, polymerized acrylic resins based on PMMA (polymethyl methacrylate), PMMA-DEGDA (polymethyl methacrylate diethylene glycol diacrylate), PBMA (polybutyl methacrylate), and PiBMA (polyisobutyl methacrylate) are preferred. Other suitable resins are cross-linked poly(styrene-co-divinylbenzene) or poly(4-vinylpyridine-co-ethylvinylbenzene). In a preferred embodiment, the particle size of the organic polymer filler is ≤10 μm. When the filler has the particle size described herein, its compatibility in the UV-VIS curable sealant composition is improved, and the composition maintains high uniformity and form or shape stability after dispensing. From the perspective of chemical robustness and / or stability over time, the acrylic resin imparts the desired rheological properties without inducing any weakening of the composition over time.

[0096] The at least one cationic curable cyclic compound e) different from a) and b) that can be used in the UV-VIS curable sealant composition described herein includes oxetanes, oxolanes, cyclic acetals, anhydrides, cyclic lactones, thiiranes, and thiotanes. Typical oxolane compounds include tetrahydrofuran and 2,3-dimethyltetrahydrofuran. Typical cyclic acetal compounds include trioxane, 1,3-dioxolane, and 1,3,6-trioxocane. Typical cyclic lactone compounds include β-propiolactone and ε-caprolactone. Typical anhydrides include phthalic anhydride and terephthalic anhydride and their hydroxyl-containing derivatives. Typical thiirane compounds include ethylene sulfide, 1,2-propylene sulfide, and thioepichlorohydrin. Typical thiirane compounds include 1,3-propylene sulfide and 3,3-dimethylthietane. The cationically curable cyclic compound e) may be present in the UV-VIS curable sealant composition in an amount of about 0 to about 30 wt.%, preferably about 15 to about 30 wt.%, and even more preferably about 20 to about 25 wt.%.

[0097] According to a preferred embodiment, the UV-VIS curable sealant composition may include one or more oxetane compounds or compounds having oxetane functional groups, as described herein. For embodiments in which the UV-VIS curable sealant composition described herein includes one or more oxetanes, the one or more oxetanes are present in an amount of less than or equal to about 30 wt.%, preferably greater than or equal to about 5 wt.% and less than or equal to about 25 wt.%.

[0098] Preferred examples of oxetanes include propylene oxide, 3,3-dimethyloxetane, trimethylolpropaneoxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-[(2-ethylhexyloxy)methyl]oxetane, 3,3-dicyclomethyloxetane, 3-ethyl-3-phenoxymethyloxetane, bis([1-ethyl(3-oxetanyl)]methyl)ether, 1,4-bis[3-ethyl-3-oxetanylmethoxy)methyl]benzene, 3,3-dimethyl-2(p-methoxy-phenyl)oxetane, 3-ethyl-[(triethoxysilylpropoxy)methyl]oxetane, 4,4-bis(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl and 3,3-dimethyl-2(p-methoxy-phenyl)oxetane. The one or more oxetanes described herein may be hydroxyl-modified or (meth)acrylate-modified.

[0099] Suitable commercially available examples of oxetanes are, but are not limited to, OXT221 (Toagosei Chemical), 3-ethyl-3-oxetanemethanol (Sigma-Aldrich), 3,3-dimethyloxetane (Sigma-Aldrich) and / or 3-ethyl-3-[(2-ethylhexyloxy)methyl]oxetane (OXT 212) (Toagosei chemical).

[0100] The UV-VIS curable sealant composition may comprise at least one additional additive selected from the group consisting of a photosensitizer, a surfactant, an adhesion promoter, and mixtures thereof, wherein the additive f) is different from components a) to e), and wherein the amount of the at least one additional additive may be from about 0 to about 30 wt.%, preferably from about 2 to about 20 wt.%, even more preferably from about 5 to about 15 wt.%.

[0101] In one embodiment, the at least one additional additive is a photosensitizer, and the UV-VIS curable sealant composition may contain more than one such photosensitizer. Photosensitizers are activated by one or more wavelengths emitted by a UV-VIS light source and reach an excited state. The excited photosensitizer then transfers energy to at least one cationic photoinitiator, which in turn initiates the polymerization process. When present, the one or more photosensitizers are preferably present in an amount of about 0.1 to about 10 wt.%, more preferably about 0.1 to about 5 wt.%, and even more preferably about 0.2 to about 1 wt.%.

[0102] Commercially available photosensitizers include, but are not limited to, thioxanthone derivatives, anthracene derivatives (e.g. 9,10-diethoxyanthracene sold by UVS-1101

[0103] UVS-1331, both sold by Kawasaki Kasei Chemicals Ltd) and titanocene derivatives such as those sold by BASF 784). Other suitable photosensitizers include, but are not limited to, isopropyl-thioxanthone (ITX), 1-chloro-2-propoxy-thioxanthone (CPTX), 2-chloro-thioxanthone (CTX), and 2,4-diethyl-thioxanthone (DETX), and mixtures thereof. Alternatively, the thioxanthone photosensitizer may be used in oligomeric or polymeric form (e.g., OMNIPOL TX sold by IGM Resins, TX sold by Rahn TX-2 or SpeedCure 7010 sold by Lambson).

[0104] In one embodiment, the at least one additional additive is a nonionic surfactant, and the UV-VIS curable sealant composition may include one or more of the nonionic surfactants in an amount of about 0.01 to about 5 wt.%, preferably about 0.05 to about 3 wt.%, more preferably about 0.1 to about 2 wt.%, and even more preferably about 0.2 to about 1 wt.%.

[0105] As is well known to those skilled in the art, nonionic surfactants comprise a hydrophilic portion and a hydrophobic portion and are uncharged. Preferably, the one or more nonionic surfactants used have a molecular weight between about 200 g / mol and about 3000 g / mol and / or contain one or more functional groups selected from hydroxyl groups and epoxide groups. More preferably, the one or more nonionic surfactants are selected from nonionic fluorinated surfactants and nonionic silicone surfactants.

[0106] As used herein, the term "nonionic fluorinated surfactant" includes nonionic perfluoropolyether surfactants and nonionic fluorine surfactants.

[0107] As used herein, the term "nonionic perfluoropolyether surfactant" refers to a nonionic surfactant comprising a perfluoropolyether backbone and one or more, preferably two or more, terminal functional groups selected from the group consisting of hydroxyl, epoxide, acrylate, methacrylate, and trialkoxysilyl, preferably selected from the group consisting of hydroxyl and epoxide. Preferably, the nonionic perfluoropolyether surfactant is characterized by an average molecular weight (Mn) of less than about 2000 [g / mol]. As used herein, the perfluoropolyether backbone refers to the residue of a perfluoropolyether polymer comprising randomly distributed repeating units selected from perfluoromethyleneoxy (-CF2O-) and perfluoroethyleneoxy (-CF2-CF2O-). The perfluoropolyether residue is linked directly or via a spacer to a terminal functional group selected from the group consisting of methylene (ethyleneoxy), 1,1-difluoroethylene-(ethyleneoxy), methylene-bis(ethyleneoxy), 1,1-difluoroethylene-bis(ethyleneoxy), methylene-tri(ethyleneoxy), 1,1-difluoroethylene-tri(ethyleneoxy), methylene-tetra(ethyleneoxy), 1,1-difluoroethylene-tetra(ethyleneoxy), methylene-penta(ethyleneoxy), 1,1-difluoroethylene-penta(ethyleneoxy) and a linear or branched hydrocarbon group, optionally fluorinated at the carbon atom connecting the spacer to the perfluoropolyether residue, comprising one or more carbamate groups, or one or more amide groups, and optionally one or more cyclic moieties, including saturated cyclic moieties (such as cyclohexylene) and aromatic cyclic moieties (such as phenylene). Preferably, the nonionic perfluoropolyether surfactant is functionalized with one or more hydroxyl and / or epoxide functional groups.

[0108] Particularly suitable examples of nonionic perfluoropolyether surfactants are available from Solvay under the name E10H, MD700, MD500, AD1700, E series and S10 is commercially available.

[0109] As used herein, the term "nonionic fluorosurfactant" refers to a surfactant containing a perfluoroalkyl chain CF3(CF2) x wherein x is an integer from 2 to 18. Preferably, the nonionic fluorosurfactant is characterized by an average molecular weight (Mn) of about 200 [g / mol] to about 2000 [g / mol]. Preferably, the nonionic fluorosurfactant is a compound of formula (VII):

[0110] CF3(CF2) x (CH2) y E

[0111] (VII)

[0112] in

[0113] x is an integer from 2 to 18;

[0114] y is an integer from 0 to 8; and

[0115] E is selected from

[0116] -(CR2CR2O) z H, and -OSi(OR 20 )3,

[0117] wherein z is an integer from 0 to 15;

[0118] R may be the same or different at each occurrence and is selected from hydrogen and methyl; and

[0119] R 20 It is a C1-C4 alkyl group.

[0120] The nonionic fluorosurfactant can be selected from fluorinated epoxy monomers, preferably selected from 3-perfluorooctyl-1,2-epoxypropane (Fluorochem), 3-perfluorohexyl-1,2-epoxypropane (Sigma-Aldrich) (Chemical Co., Ltd) and / or 3-[2-(perfluorohexyl)ethoxy]-1,2-epoxypropane (TCI American).

[0121] Nonionic fluorinated surfactant of general formula (VIII-a):

[0122] CF3(CF2) x (CH2) y (CR2CR2O) z H

[0123] (VIII-a)

[0124] in

[0125] x is an integer from 2 to 18;

[0126] y is an integer from 0 to 8;

[0127] z is an integer from 0 to 15; and

[0128] R may be the same or different at each occurrence and is selected from hydrogen and methyl, preferably hydrogen being particularly preferred. The nonionic fluorosurfactant of formula (VIII-a) is commercially available under the name CHEMGUARD S550-100 or CHEMGUARD S550, CHEMGUARD S222N, CHEMGUARD S559-100 or CHEMGUARD S559, all commercialized by CHEMGUARD; Capstone TM FS-31, Capstone TM FS-35, Capstone TM FS-34, Capstone TM FS-30, Capstone TM FS-3100, all commercialized by Chemours.

[0129] Nonionic fluorinated surfactant of general formula (VIII-b):

[0130] CF3(CF2) x (CH2) y OSi(OR 20 )

[0131] (VIII-b),

[0132] in

[0133] x is an integer from 2 to 18;

[0134] y is an integer from 0 to 8; and

[0135] R 20 is a C1-C4 alkyl group, which is also preferred. Nonionic fluorosurfactants of the general formula (VIII-b) are commercially available under the names Dynasylan F8261 and Dynasylan F8263, commercialized by Evonik.

[0136] Nonionic fluorinated surfactant of general formula (VIII-c):

[0137]

[0138] in

[0139] x is an integer from 2 to 18;

[0140] y is an integer from 0 to 8; and

[0141] R 21Selected from hydrogen and methyl, is also preferred. Examples of nonionic fluorinated surfactants of general formula (VIII-c) include, but are not limited to: 1H,1H,2H,2H-perfluorooctyl acrylate (Sigma-Aldrich), 1H,1H,2H,2H-perfluorooctyl methacrylate (Sigma-Aldrich), 1H,1H-perfluorooctyl acrylate (Sigma-Aldrich), 1H,1H-perfluorooctyl methacrylate (Sigma-Aldrich), 1H,1H-perfluoroheptyl acrylate (Sigma-Aldrich), and 1H,1H-perfluoroheptyl methacrylate (Sigma-Aldrich).

[0142] As used herein, nonionic silicone surfactants refer to nonionic surfactants comprising a silicone backbone containing randomly distributed repeating units selected from di(methyl)siloxane (-(CH3)2SiO-) and / or methyl-(C2-C 10 -alkyl)-siloxane (-(CH3)(C2-C 10 -alkyl)SiO-), wherein one or more methyl groups and / or C2-C 10 -alkyl groups may be substituted independently of one another by aromatic groups, polyesters optionally presenting terminal functional groups selected from hydroxyl groups, epoxide groups and (meth)acrylate groups, polyethers such as polyalkylene glycols (including polyethylene glycol and polypropylene glycol) optionally presenting terminal functional groups selected from hydroxyl groups, epoxide groups and (meth)acrylate groups, hydroxyl groups, epoxide groups or (meth)acrylate groups, and / or wherein the organosilicon backbone may be linked directly or via a spacer to a terminal functional group selected from hydroxyl groups, epoxide groups and (meth)acrylate groups. The organosilicon backbone described herein may be linked to an aliphatic urethane acrylate or a fluoroaliphatic urethane acrylate. Preferably, the nonionic organosilicon surfactant is characterized by an average molecular weight of less than about 3000 g / mol.

[0143] Nonionic silicone surfactants include, but are not limited to, poly-methyl-alkyl-siloxanes such as BYK-077 and BYK-085 commercialized by BYK, polyester-modified poly-dimethyl-siloxanes such as BYK310 commercialized by BYK, polyether-modified poly-dimethyl-siloxanes such as BYK-377, BYK-333, BYK-345, BYK-346 and BYK-348 commercialized by BYK, polyester-modified poly-methyl-alkyl-siloxanes such as BYK-315 commercialized by BYK, polyether-modified poly-methyl-alkyl-siloxanes such as BYK-341, BYK-320 and BYK-325 commercialized by BYK, hydroxy-functional poly-dimethyl-siloxanes such as BYK-316 commercialized by Evonik. HSI-2311, polyester-modified hydroxy-functional poly-dimethyl-siloxanes such as BYK-370 and BYK-373 commercialized by BYK, polyether-modified hydroxy-functional poly-dimethyl-siloxanes such as BYK-308 commercialized by BYK, polyether-polyester-modified hydroxy-functional poly-dimethyl-siloxanes such as BYK-375 commercialized by BYK, epoxy-functional poly-dimethyl-siloxanes such as BYK-370 commercialized by Evonik E-Si 2330, an acryloxy-functional poly-dimethyl-siloxane, such as commercialized by Evonik V-SI 2250 and Rad2700, polyester-modified acrylic functional poly-dimethyl-siloxane, such as BYK-371 commercialized by BYK, polyether-modified acrylic functional poly-dimethyl-siloxane, such as Evonik commercialized by Rad2100 and Rad 2500, silicone-modified aliphatic urethane acrylates such as SUO-S3000 and SUO-S600NM commercialized by Polygon, silicone- and fluorine-modified aliphatic urethane acrylates such as SUO-FS500 commercialized by Polygon.

[0144] In other embodiments, the at least one additional additive is an adhesion promoter, and the UV-VIS curable sealant composition may include more than one such adhesion promoter. One or more adhesion promoters that can be used to further improve the adhesion of the resulting photopolymer layer may include a transition metal chelate, a thiol, a thiol-containing compound, a carboxylic acid, an organophosphoric acid, a diol, an alkoxysilane, a combination of alkoxysilanes and a hydroxyl-functional polyorganosiloxane, or a combination thereof. The one or more adhesion promoters may be unsaturated or epoxy-functional compounds. Suitable epoxy-functional compounds are known in the art and are commercially available, see, for example, U.S. Patent Nos. 4,087,585; 5,194,649; 5,248,715; and 5,744,507col.45.

[0145] More than one adhesion promoter can preferably include unsaturated or epoxy-functional alkoxysilane.The example of suitable epoxy-functional alkoxysilane includes 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyl-triethoxysilane, (epoxycyclohexyl) ethyldimethoxysilane, (epoxycyclohexyl)-ethyldiethoxysilane and combination thereof.The example of suitable unsaturated alkoxysilane includes vinyltrimethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, hexenyltrimethoxysilane, undecenyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane and combination thereof.

[0146] Preferred adhesion promoters are preferably selected from the group comprising Silquest A187 (Momentive), (3-glycidoxypropyl)triethoxysilane (Sigma-Aldrich), (3-glycidoxypropyl)trimethoxysilane (Sigma-Aldrich) and / or trimethoxy[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane (Sigma-Aldrich).

[0147] The UV-VIS curable sealant composition may include one or more organic solvents. There is no particular limitation on the one or more organic solvents, but they are preferably non-polar organic solvents. Examples of polar organic solvents include, but are not limited to, alcohols (e.g., methanol, ethanol, propanol, butanol, isopropanol, and fluorinated alcohols), ketones (e.g., acetone, methyl ethyl ketone, and cyclohexanone), carboxylates (e.g., methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, and ethyl propionate), and ethers (e.g., diethyl ether, dipropyl ether, tetrahydrofuran, and dioxane). These organic solvents may be used alone or in combination. The UV-VIS curable sealant composition may include up to about 10 wt.% of one or more organic solvents. Preferably, and when present, the organic solvent is present in an amount of from about 1 wt.% to about 7.5 wt.%, more preferably from about 2 wt.% to about 5 wt.%. Alternatively, in other embodiments, the UV-VIS curable sealant composition does not contain any solvent, i.e., it is solvent-free.

[0148] In one embodiment, the present invention relates to a method of encapsulating electrical contacts on an inkjet printhead, comprising:

[0149] a) providing a UV-VIS curable sealant composition as described herein;

[0150] b) providing an assembly comprising a flexible circuit and a silicon chip;

[0151] c) dispensing a UV-VIS curable sealant composition onto electrical contacts connecting the silicon chip to the flexible circuit; and

[0152] d) curing or at least partially curing the UV-VIS curable sealant composition using a UV-VIS light source.

[0153] FIG3 illustrates but is not limited to one embodiment of the packaging method. After bonding, the assembly (17) of the silicon chip (2) and the flexible printed circuit (3) is transferred to a distribution station (18), where a certain amount (19) of the uncured UV-VIS curable sealant composition is delivered in each area to be protected. The assembly (17) with the distributed UV-VIS curable sealant undergoes rapid movement to a curing station (20), where a UV-VIS lamp (21) cures the UV-VIS curable sealant composition. Typically, UV-VIS curing is carried out between 200-420nm. Within this range, the UV-VIS curable sealant composition reaches a high degree of conversion of the reactive functional groups it contains. Post-exposure heat treatment does not have to be used, which simplifies the manufacturing process. After the curing process of the UV-VIS curable sealant composition, a high level of adhesion to the different materials (i.e., especially silicon and silicon compounds, gold or other metals, polyimides, protective coatings, etc.) constituting the assembly (17) is achieved.

[0154] The method described herein comprises a step d) of curing or at least partially curing the UV-VIS curable sealant composition from step c), wherein the curing step is performed using a curing unit that serves as a UV-VIS light source. Suitable curing units include devices for UV-VIS curing units that include a light-emitting diode (LED) lamp or an arc discharge lamp, such as a medium-pressure mercury arc (MPMA) or metal vapor arc lamp, as a source of actinic radiation, preferably providing an emission between about 200 and about 420 nm. In contrast to medium-pressure mercury lamps that have emission bands in the UV-A, UV-B, and UV-C regions of the electromagnetic spectrum, UV-LED lamps emit radiation in the UV-A region, for example, in the range of about 380 nm to about 410 nm. In addition, current UV-LED lamps emit quasi-monochromatic radiation, i.e., they emit at only one wavelength, such as 365 nm, 385 nm, 395 nm, or 405 nm. In a preferred embodiment, curing is performed with the aid of a mercury lamp, in particular a medium-pressure mercury lamp (MPMA).

[0155] The UV-VIS curable sealant composition preferably has a thermal conductivity of at least 150 mJ / cm 2 A dose of at least 200 mJ / cm 2 A dose of at least 500 mJ / cm 2The UV-VIS curable sealant composition is exposed to UV-VIS light in a dose of 100 μm to cure the UV-VIS curable sealant composition, wherein the dose can be obtained using UV Power from EIT, Inc., USA. II radiometer measurements.

[0156] The bottom side of the flexible circuit is typically coated with an epoxy-based coating to provide electrical insulation for the copper traces. A set of metal fingers or electrical contacts connects the flexible circuit to the silicon chip. In a preferred embodiment, the placement area can be surface treated before dispensing the UV-VIS-curable sealant composition onto the metal fingers or electrical contacts. A preferred method of surface treatment is plasma treatment.

[0157] Plasma treatment is used to enhance the bonding of the UV-VIS curable sealant composition to the reservoir and / or epoxy coating surface. The enhanced bonding can particularly prevent ink penetration at the interface of various additional adhesives used in the inkjet printhead assembly.

[0158] Plasma treatment can be carried out by inducing surface polarization with the aid of gases such as oxygen, nitrogen, carbon dioxide, etc. This polarization is promoted by dipoles and polar moieties activated by the plasma treatment on the surface. In a preferred embodiment, nitrogen is used for plasma treatment.

[0159] To achieve high throughput in the manufacturing process and the possibility of performing plasma treatment without the need for vacuum for safety reasons, an Acxys atmospheric-pressure nitrogen plasma treatment system can be used. Treatment can be performed on both sides of the flexible circuit. Plasma treatment is preferably performed before bonding the silicon chip to avoid conditioning the front of the injector stack, which should not be wettable for proper printing. In other embodiments, plasma treatment can also be performed on only one of the two surfaces of the flexible circuit, for example, to modify and, in particular, polarize epoxy coating surfaces.

[0160] To achieve good results in terms of wettability, the apparatus should be set to a power of at least 1500 W and a nitrogen flux of at least 120 sccm. In a preferred embodiment, the apparatus should be set to a power of at least 2000 W and a nitrogen flux of at least 120 sccm and a conveyor speed of at least 10 seconds per piece. The effect of the plasma treatment can be monitored by means of the contact angle as a function of the residence time at room temperature.

[0161] One embodiment relates to the use of the UV-VIS curable sealant composition described herein for the manufacture of an inkjet printhead. In particular, the use relates to protecting electrical contacts between a flexible circuit and a silicon chip mounted on the inkjet printhead.

[0162] Without departing from the spirit of the present invention, a skilled person may conceive of several modifications to the specific embodiments described above. Such modifications are encompassed by the present invention.

[0163] Furthermore, all documents mentioned throughout this specification are hereby incorporated by reference in their entirety as if fully set forth herein.

[0164] Example

[0165] Examples E1-E9 were prepared as follows. The ingredients listed in Table 1 were introduced into a suitable reaction vessel in order from top to bottom. The materials were mixed in a Thinky planetary mixer for two cycles of 30 minutes each. After mixing, the resulting composition was introduced into a dispensing syringe.

[0166] Viscosity measurement: With the help of a plate P20 (about 0.2 cm 3 The samples were analyzed using a rotational viscometer (Reologica).

[0167] Table 1

[0168]

[0169] In order to measure the stability of the cured UV-VIS curable sealant composition to ink, an immersion test was designed. The UV-VIS curable sealant composition was cured independently by means of a UV exposure device (Exfor 5000) with broadband exposure in the UVA range (315-400 nm) at a dose of at least 500 mJ / cm 2 The UV radiation is focused onto the adhesive surface with the help of optical fibers.

[0170] Examples E2 and E4-E8 were evaluated by immersing the front of the print head containing the cured UV-VIS curable sealant composition in a solvent-based ink at 45°C for 1 week. Afterwards, the front of the print head, in particular the UV-VIS curable sealant composition, was observed to determine whether there were any relevant defects on the material. In particular, the observation was carried out by observing the shape and color of the UV-VIS curable sealant composition under an optical microscope and attempting to remove the material with a knife. In the absence of any relevant penetration at the interface or any change in the structure and shape of the glue, the composition was considered to have passed the stability test. Otherwise, it was classified as a failure. The results of the immersion test are as follows:

[0171] -E2: Failed

[0172] -E4: Failed

[0173] -E5: Failed

[0174] -E6: Pass

[0175] -E7: Failed

[0176] -E8: Failed

[0177] The immersion test was conducted using the following solvent-based inks:

[0178]

[0179] A test was designed to measure the resistance of UV-VIS-curable sealant compositions to ink. A printhead containing cured UV-VIS-curable sealant compositions E2 and E4-E8 was maintained under electrical tension with its front constantly moistened with fresh aqueous ink. Aqueous ink was chosen because it is more aggressive toward the silicon and conductive parts of the chip. Aqueous ink also has a higher conductivity than solvent-based ink and can easily penetrate the sealant composition, causing an electrical short. A positive result was determined if the UV-VIS-curable sealant effectively protected the printhead electrical contacts from electrical failure.

[0180] The water-based ink wetted the front of the printhead and the electrical contacts, as well as the UV-VIS-curable sealant composition. This electrical test closely simulates conditions that might occur in the field on an installed printer, particularly during downtime. With the exception of composition E6, the other sealant compositions tested experienced electrical shorts or leaks after a period ranging from a few hours to about a week. If the sample, once exposed to the water-based ink, did not exhibit any electrical defects (e.g., shorts) after a week, the test result was considered positive and graded as a pass; otherwise, it was graded as a fail.

[0181] -E2: Failed

[0182] -E4: Failed

[0183] -E5: Failed

[0184] -E6: Pass

[0185] -E7: Failed -E8: Failed The resistance test was performed using the following water-based inks:

[0186] raw material supplier %Wt 2-Pyrrolidone CAS: 616-45-5 VWR 10 Ethylene glycol CAS: 107-21-1 VWR 10 Glycerol CAS: 56-81-5 VWR 5 Surfynol 465 VWR 1.5 Proxel GXL VWR 0.1 Cab-O-Jet 465M (2.5%) Cabot 16.33 Cab-O-Jet 270Y (1%) Cabot 9.99 water / 47.08

Claims

1. A UV-VIS curable sealant composition comprising: a) 25-40 wt.% of at least one aromatic epoxide monomer or aromatic epoxide oligomer or a mixture thereof; b) 4 to 20 wt.% of at least one epoxidized polyene; c) 20-35 wt.% of at least one organic filler or inorganic filler or a mixture thereof; d) 0.1-10 wt.% of at least one cationic photoinitiator; e) 0-30 wt.% of at least one cationically curable cyclic compound different from a) and b); f) 0.05-3 wt.% of a nonionic surfactant; and g) 0-30 wt.% of at least one additional additive selected from the group consisting of photosensitizers, adhesion promoters or any mixtures thereof, wherein the additive g) is different from components a) to f); wherein the UV-VIS curable sealant composition has a viscosity at 25° C. of about 60,000 m·Pas to about 120,000 m·Pas; The weight percentages are based on the total weight of the UV-VIS curable sealant composition.

2. The UV-VIS curable sealant composition according to claim 1, comprising: a) 35-40 wt.% of at least one aromatic epoxide monomer or aromatic epoxide oligomer or a mixture thereof; b) 5-15 wt.% of at least one epoxidized polyene; c) 20-25 wt.% of at least one organic filler or inorganic filler or a mixture thereof; d) 3-10 wt.% of at least one cationic photoinitiator; e) 0-30 wt.% of at least one cationically curable cyclic compound different from a) and b); f) 0.1-2 wt.% of a nonionic surfactant; and g) 0-30 wt.% of at least one further additive selected from the group consisting of photosensitizers, adhesion promoters or any mixtures thereof, wherein the additive g) is different from components a) to f).

3. The UV-VIS curable sealant composition according to claim 1 or 2, wherein the nonionic surfactant is a nonionic silicone surfactant comprising a silicone backbone containing randomly distributed repeating units selected from di(methyl)siloxane (-(CH3)2SiO-) and / or methyl-(C2-C 10 -alkyl)-siloxane, wherein one or more methyl and / or C2-C 10 -Alkyl groups can be substituted independently of one another by aryl groups, polyesters, poly-methyl-alkyl-siloxanes.

4. The UV-VIS curable sealant composition according to claim 3, wherein the nonionic silicone surfactant is a poly-methyl-alkyl-siloxane. 5 . The UV-VIS curable sealant composition according to claim 1 , comprising about 20 to about 30 wt. % of compound e).

6. The UV-VIS curable sealant composition according to any one of claims 1 to 5, wherein component b) is at least one epoxidized polybutadiene. 7 . The UV-VIS curable sealant composition according to claim 1 , wherein the size of component c) is between 5 μm and 15 μm.

8. The UV-VIS curable sealant composition according to any one of claims 1 to 7, wherein component c) has a refractive index at 400 nm of between 1.2 and 1.

8.

9. The UV-VIS curable sealant composition according to any one of claims 1 to 8, wherein component c) is at least one polymer filler, preferably at least one PMMA-based filler.

10. The UV-VIS curable sealant composition according to any one of claims 1 to 9, wherein component c) is at least one inorganic filler, preferably selected from the group consisting of glass, carbonates, talc and mixtures thereof.

11. The UV-VIS curable sealant composition according to any one of claims 1 to 10, wherein component d) is selected from the group consisting of triphenylsulfonium salts, diazonium salts, diaryliodonium salts, ferrocenium salts, metallocene compounds, and mixtures thereof. 12 . An inkjet print head comprising any one of the UV-VIS curable sealant compositions according to claim 1 .

13. A method of encapsulating electrical contacts on an inkjet printhead, comprising: a) providing a UV-VIS curable sealant composition according to any one of claims 1 to 11; b) providing an assembly comprising a flexible circuit and a silicon chip; c) dispensing a UV-VIS curable sealant composition onto electrical contacts connecting the silicon chip to the flexible circuit; and d) curing or at least partially curing the UV-VIS curable sealant composition using a UV-VIS light source.

14. The method according to claim 13, wherein: Step b1) following step b) comprises exposing at least one surface of the flexible circuit to a plasma treatment, preferably to a nitrogen plasma atmosphere.

15. Use of the UV-VIS curable sealant composition according to any one of claims 1 to 11 for manufacturing an inkjet print head.

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