Solvent-resistant elastomer adhesive for inkjet printheads

Abstract

The present invention provides an elastomeric adhesive having good chemical resistance to solvent-based inks, and a method for preparing the elastomeric adhesive. The elastomeric adhesive can be used as a hydraulic adhesive inside an inkjet printhead to securely bond the chip to the hydraulic components of the cartridge body reservoir and the plug to the inkjet printhead reservoir. Thus, inkjet printheads using the elastomeric adhesive of the present invention are resistant to both conventional solvent-based inks and UV-curable inks and can be printed on porous and non-porous surfaces.

Description

Detailed Description of the Invention

[0001] [Field of the Invention]

[0001] The present invention relates to the field of thermal inkjet printhead technology, and in particular to elastomeric adhesives, methods for preparing elastomeric adhesives, and the use of elastomeric adhesives in inkjet printheads.

[0002] [Background of the invention] A typical prior art inkjet printhead cartridge, such as that described in EP 1896262 (see FIG. 1 therein), consists of a printhead ejection assembly made up of a printhead chip bonded to a flexible printed circuit. The printhead chip houses the electrical and hydraulic components for directing ink to various ejection sites and energizing them on demand to produce ink droplets for printing. A nozzle plate is applied to the top surface of the chip to provide the ink ejection nozzles. The entire ejection assembly is then bonded to a cartridge containing ink reservoirs and closed with a lid. Appropriate ink channels are provided in the cartridge body to allow ink to reach the printhead chip and the microfluidic circuitry either through channels machined in the chip or from the end of the chip, depending on the printhead configuration. A multi-ink printhead cartridge will naturally have multiple ink reservoirs and ink passages to multiple printheads, which are hydraulically isolated from each other to prevent the inks from mixing. Because cartridges are made from an assembly of different parts and materials, the mating surfaces between the parts need to ensure not only a good bond but also a complete and long-lasting ink seal in the area that comes into contact with the ink. To bond the chip to the cartridge body, a suitable adhesive can be dispensed onto the flat surface around the flow path of the cartridge body to also ensure a good seal around the lower surface of the groove in the chip. In this way, the ink can flow from the reservoir to the chip without any mixing or leakage.

[0003] Furthermore, cartridge bodies for multi-ink printheads require special manufacturing processes. For example, a cartridge with three inks in a parallel nozzle array cannot be produced in a single molding process using casting techniques. As shown in FIG. 2 of EP 1896262, the cartridge body has three ink reservoirs separated by walls. Due to the small lateral distance between the different color nozzle arrays, it is not possible to produce three separate, straight ink paths to maintain the necessary hydraulic properties and adequate structural stability. A possible solution is to use a more complex mold, such as that described in EP 1896262, which uses two additional parallel slide inserts to produce the desired fluid structure inside the cartridge body. Once the casting process is complete, the two slide inserts can be removed, leaving two windows open on the side of the cartridge body. These windows must be closed with appropriate plugs that are conveniently attached to the cartridge. A possible method of joining the plug is to use adhesive material dispensed along the flat recessed surface of the window border to ensure a tight seal of the opening and prevent ink from leaking out of the container.

[0004]

[0004] Therefore, there is a need for a suitable adhesive for a typical printhead cartridge, for bonding the chip to the cartridge body and for bonding the plug to the container. Traditionally, adhesives used in printheads loaded with water-based inks are single-component epoxy adhesives, such as Ecobond E3200 (Henkel). This type of single-component epoxy adhesive ensures rigid adhesion of the silicon chip to the printhead's plastic container. However, when solvent-based inks are used, these types of single-component epoxy adhesives, although extensively tested for inkjet applications, exhibit serious drawbacks. For example, the adhesive's adhesion weakens due to the chemical action of the solvent, and the printhead will experience electrical failure over its lifetime as a result of swelling of the adhesive under solvent action. Another critical aspect is the low flexibility of epoxy adhesives, so that thermal stresses during the printhead manufacturing process and during storage can damage the fragile silicon chip components.

[0005]

[0005] Therefore, there is an urgent need in the art to develop special elastomeric adhesives that, once cured, guarantee desirable chemical resistance in solvent environments while at the same time ensuring high flexibility. There is also a need for elastomeric adhesives that include good adhesion to surfaces such as polyolefins, silicones, Kapton, and thermoplastic adhesives, dispensability by pneumatic or vortex deposition systems, adequate thixotropy, good visibility of the adhesive once dispensed by optical detection systems, time / temperature cure conditions compatible with other components of the printhead, most preferably a single-component system, a low Young's modulus to reduce mechanical stress between mating parts of the device during the manufacturing process and during the service life of the product, and / or reduced air permeability.

[0006] [Summary of the Invention]

[0006] To solve the above technical problems, the present invention proposes a novel elastomeric adhesive. The elastomeric adhesive has suitable thixotropy and viscosity, resulting in good dispensability by pneumatic or vortex systems. The novel adhesive exhibits a desirable shape once dispensed onto the surfaces to be joined, minimizing undesirable flow effects between printhead components and curing temperatures compatible with the production line.

[0007]

[0007] As a first aspect of the present invention, Linear unsaturated hydrocarbon-based polymers containing at least one non-aromatic unsaturation in at least one monomer, including polyisoprene-grafted maleic anhydride and polybutadiene-styrene; one or more sulfur donor molecules, and Organometallic Zinc Catalyst 1. A method for preparing an elastomeric adhesive for bonding components inside an inkjet printhead from a composition comprising: a) reacting one or more sulfur donor molecules with an organometallic zinc catalyst to form a zinc sulfide complex as an active crosslinking initiator; b) catalyzing the vulcanization reaction of one or more linear unsaturated hydrocarbon-based polymers with a zinc sulfide complex to obtain a vulcanized polymer and a thiol; c) cross-linking the polymer chains of the vulcanized polymer obtained in step b) through polysulfide bridges between the units by a curing process; A method is provided, comprising:

[0008] In a second aspect of the present invention, there is provided an elastomeric adhesive prepared by the method according to the first aspect of the present invention.

[0009] In a third aspect of the present invention, there is provided an ink jet printhead comprising an elastomeric adhesive prepared by the method according to the first aspect of the present invention.

[0010]

[0010] In a fourth aspect of the present invention, there is provided the use of an elastomeric adhesive prepared by a method according to the first aspect of the present invention for bonding components inside an inkjet printhead.

[0011] The elastomeric adhesive of the present invention has the following advantageous technical effects: The elastomeric adhesive of the present invention enables the fabrication of solvent-resistant inkjet printheads and can firmly bond components within the inkjet printhead, such as bonding a chip (e.g., a silicon chip) to a hydraulic component in a cartridge body reservoir (e.g., a plastic polyolefin-based reservoir), and bonding a plug to the reservoir. Thus, inkjet printheads containing the elastomeric adhesive of the present invention are resistant to both conventional solvent-based inks and UV-curable inks, and can be printed on porous and non-porous surfaces.

[0012]

[0012] Non-limiting and non-exhaustive embodiments of the present invention are described by way of example with reference to the following drawings: [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of a hot air blower for curing hydraulic adhesive in an inkjet printhead.

[0014] Detailed Description of the Embodiments To make the above and other features and advantages of the present invention more apparent, the present invention will be further described in conjunction with the accompanying drawings, in which: It will be understood that the particular embodiments of the present invention are illustrative and not intended to be limiting.

[0015]

[0015] As a first aspect of the present invention, Linear unsaturated hydrocarbon-based polymers containing at least one non-aromatic unsaturation in at least one monomer, including polyisoprene-grafted maleic anhydride and polybutadiene-styrene; one or more sulfur donor molecules, and Organometallic Zinc Catalyst 1. A method for preparing an elastomeric adhesive for bonding components inside an inkjet printhead from a composition comprising: a) reacting one or more sulfur donor molecules with an organometallic zinc catalyst to form a zinc sulfide complex as an active crosslinking initiator; b) catalyzing the vulcanization reaction of one or more linear unsaturated hydrocarbon-based polymers with a zinc sulfide complex to obtain a vulcanized polymer and a thiol; c) cross-linking the polymer chains of the vulcanized polymer obtained in step b) through polysulfide bridges between the units by a curing process; A method is provided, comprising:

[0016] In a preferred embodiment, the one or more linear unsaturated hydrocarbon-based polymers further comprise one or more covalently bonded polar groups in at least one monomer.

[0017] In a preferred embodiment, the organometallic zinc catalyst is zinc carbamate, zinc guanidine, and / or zinc xanthate. The zinc carbamate can be, for example, zinc ethylphenyldithiocarbamate (ZEPC) and / or zinc dibutyldithiocarbamate (ZDBC).

[0018] In one embodiment, the composition comprises: 15% to 60% of one or more linear unsaturated hydrocarbon-based polymers; 3.3% to 10.6% of one or more sulfur donor molecules, and 2.0% to 7.0% organometallic zinc catalyst and the percentages are calculated based on the total weight of the composition.

[0019] In a preferred embodiment, the composition comprises: 20% to 50% of one or more linear unsaturated hydrocarbon-based polymers; 5.0% to 8.5% of one or more sulfur donor molecules, and 3.0% to 6.0% organometallic zinc catalyst and percentages are calculated based on the total weight of the composition.

[0020] In a more preferred embodiment, the composition comprises: 35% to 40% of one or more linear unsaturated hydrocarbon-based polymers; 6.5% to 7.5% of one or more sulfur donor molecules, and 4.0% to 5.0% organometallic zinc catalyst and percentages are calculated based on the total weight of the composition.

[0021] (Linear unsaturated hydrocarbon polymer) As mentioned above, the composition of the present invention comprises one or more linear unsaturated hydrocarbon-based polymers containing at least one non-aromatic unsaturation in at least one monomer. The unsaturation is a reactive site (particularly an allylic hydrogen) during the vulcanization reaction of the linear unsaturated hydrocarbon-based polymer. During the vulcanization reaction, the allylic hydrogen is replaced by a sulfur atom (substitution reaction) of the polysulfide chain derived from the zinc catalyst once sulfurized.

[0022] In a preferred embodiment, the linear unsaturated hydrocarbon-based polymer further comprises one or more covalently bonded polar groups, such as alcohol, ketone, ester, amide, carboxyl, amine, anhydride, in at least one monomer for covalent bonding. The presence of one or more covalently bonded polar groups in the polymer chain increases surface interaction and, as a result, promotes adhesion.

[0023] In a more preferred embodiment, the polar group is an anhydride. An anhydride is a functional group that undergoes a nucleophilic substitution reaction, for example, with a hydroxyl, amino, or carboxylic acid group that is ultimately present on the surface to be bonded. The new bond created between the polymer and the surface by the anhydride is a strong covalent bond. Without wishing to be bound by theory, anhydrides can also cause weaker interactions with other functional groups, such as dipole-dipole or van der Waals interactions.

[0024] In a preferred embodiment, the linear unsaturated hydrocarbon-based polymer(s) of the present invention also contain aromatic moieties within the chain that improve the final mechanical properties and chemical resistance of the adhesive.

[0025] In exemplary embodiments, the one or more linear unsaturated hydrocarbon-based polymers include one of the following: [ka] where m+n is equal to 113 and neither m nor n is equal to zero. [ka] where (x+z) / (x+y+z) equals 20% and y / (x+y+z) equals 80%, and [ka] where x / (x+y) equals 33% and y / (x+y) equals 67%.

[0026] In certain embodiments, the linear unsaturated hydrocarbon-based polymer comprises polyisoprene grafted maleic anhydride and / or polybutadiene-styrene, commercially available from ALDRICH.

[0027] (sulfur donor molecule) As noted above, the compositions of the present invention contain one or more sulfur donor molecules, which are essential components for the sulfur-based vulcanization reaction. The sulfur donor molecules react with an organometallic zinc catalyst (described in detail below) to produce an active zinc sulfide complex that efficiently initiates the crosslinking reaction of linear unsaturated hydrocarbon-based polymer chains.

[0028] In one embodiment, the one or more sulfur donor molecules are selected from elemental sulfur or dispersed sulfur, which may be dispersed with an appropriate polymeric dispersant additive (usually a polymer or wax) to increase the uniformity of dispersion if solubility is not complete.

[0029] In a preferred embodiment, the one or more sulfur donor molecules are soluble crystalline sulfur with an average particle size distribution of 100 mesh or less. In this manner, the resulting elastomeric adhesive will have good homogeneity and good dispensability by pneumatic or vortex dispensing systems.

[0030] (organometallic zinc catalyst) The composition of the present invention includes an organometallic zinc catalyst. The organometallic zinc catalyst is an active compound that first reacts with a sulfur donor molecule to form an active zinc sulfide complex. The zinc sulfide complex catalyzes the sulfur substitution reaction of the allylic hydrogen of a linear unsaturated hydrocarbon-based polymer during the vulcanization reaction. As a result of the vulcanization reaction, the zinc sulfide complex decomposes into several by-products, such as ZnS and thiols, while the polymer chains are efficiently crosslinked via the corresponding long polysulfide chains.

[0031] In one embodiment, the organometallic zinc catalyst can be zinc carbamate, zinc guanidine, and / or zinc xanthate. In a preferred embodiment, the organometallic zinc catalyst is zinc carbamate and / or zinc xanthate, which, once incorporated into the complete elastomeric adhesive, exhibit higher performance in terms of scorch time, reactivity, and cure temperature of the final elastomeric adhesive.

[0032] Examples of organometallic zinc catalysts suitable for the vulcanization reaction are: [ka] Includes.

[0033]

[0033] In certain embodiments, the organometallic zinc catalyst is zinc ethylphenyldithiocarbamate (ZEPC) or zinc dibutyldithiocarbamate (ZDBC), such as those commercially available from Henan Xuannuo Imp & Exp Co., Ltd., or zinc isopropyl xanthate, such as that commercially available from Vanderbilt under the name PROPYL ZITHATE (registered trademark).

[0034] In one embodiment, the composition of the present invention comprises: metal oxides, one or more organic ligands, one or more hydrocarbon-based organic solvents or oils having a boiling point equal to or greater than the curing temperature of the composition; a coupling agent consisting of an organosilane molecule having one or more unsaturations, and / or An organic or inorganic filler that can be dispersed in the composition Further includes:

[0035] In certain embodiments, the composition comprises: 1.9% to 6.2% metal oxides, 2.5% to 8.5% of one or more organic ligands; 14% to 45% of one or more hydrocarbon organic solvents or oils, 2.5% to 9.0% of a coupling agent, and / or 1.5% to 12% organic or inorganic filler and percentages are calculated based on the total weight of the composition.

[0036] In a preferred embodiment, the composition comprises: 3.0% to 5.0% metal oxides, 4.0% to 7.0% of one or more organic ligands; 20% to 35% of one or more hydrocarbon organic solvents or oils, 4.0% to 7.5% of a coupling agent, and / or 3.0% to 10.0% organic or inorganic filler and percentages are calculated based on the total weight of the composition.

[0037] In a more preferred embodiment, the composition comprises: 4.0% to 4.5% metal oxides, 5.0% to 5.5% of one or more organic ligands; 25% to 30% of one or more hydrocarbon organic solvents or oils, 5.5% to 6.0% coupling agent, and / or 5.0% to 8.0% organic or inorganic filler and percentages are calculated based on the total weight of the composition.

[0038] (metal oxides) As mentioned above, the composition of the present invention further comprises a metal oxide, and preferably, the metal oxide is zinc oxide (ZnO). The metal oxide can be in the form of particles. In this method, metal oxide particles, such as ZnO particles, are dispersed in the composition and can react with the thiol generated from the first zinc sulfide complex during the vulcanization reaction to form a zinc complex.

[0039] In a preferred embodiment, the zinc complex is first complexed with an organic ligand, vulcanized, and then participates in the vulcanization and crosslinking reactions of the polymer.

[0040] (organic ligand) As mentioned above, the compositions of the present invention further comprise one or more organic ligands. The organic ligands are intended to increase the solubility and dispersibility of zinc-containing materials (e.g., organometallic zinc catalysts, zinc sulfide complexes, and zinc oxide) in organic non-polar compositions to prevent excessive vulcanization effects due to inadequate dispersion and / or solubilization. The organic ligands are molecules capable of forming coordination complexes with the zinc atom of the organometallic zinc catalyst, or with the zinc complex, or with ZnO.

[0041]

[0041] In a preferred embodiment, the organic ligand is a carboxylic acid and / or an amine having a non-polar molecular portion. In a more preferred embodiment, the organic ligand is a C18 to C30 carboxylic acid, an aliphatic amine, and / or an aromatic amine.

[0042] Examples of one or more organic ligands suitable for the vulcanization reaction of the polymer include: [ka] Includes.

[0043] (organic solvent or oil) As mentioned above, the compositions of the present invention further comprise one or more hydrocarbon-based organic solvents or oils. These organic solvents or oils are used to solubilize and / or disperse the other components of the composition and are hydrocarbon-based solvents such as styrene, diisopropylbenzene (DIPB), mesitylene, xylene, nonane, decane, undecane, dodecane, heptane, octane, toluene, and the like. Furthermore, the selected organic solvent or oil will have a boiling point equal to or higher than the curing temperature of the composition, i.e., the elastomeric adhesive, to prevent boiling and foaming of the solvent or oil during the curing process. For example, organic solvents or oils suitable for curing temperatures of 130° C. or less include mesitylene, xylene, nonane, decane, undecane, dodecane, and the like, while organic solvents or oils suitable for curing temperatures of 80° C. or less include heptane, octane, toluene, and all of the hydrocarbon-based solvents mentioned above.

[0044] (coupling agent) As mentioned above, the compositions of the present invention further comprise a coupling agent. The coupling agent is also an adhesion promoter and can be an organosilane molecule that is soluble in the adhesive and has reactive functional groups, such as hydroxyl, amino, and / or carboxylic acid groups, ultimately present on the surfaces (silicon and / or plastic) to be joined. Such functional groups enable the coupling agent, or in particular the organosilane molecule, to react with both other components of the adhesive and with the surfaces. In certain embodiments, reactive functional groups refer to one or more unsaturations contained in the coupling agent or organosilane molecule.

[0045]

[0045] The coupling agent, or in particular the organosilane molecule, is capable of vulcanizing and reacting with the remainder of the adhesive, thereby ensuring high bond strength between the elastomeric adhesive prepared from the composition and the silicone and / or plastic surfaces being joined.

[0046] Examples of organosilane molecules suitable for sulfur-based vulcanization reactions according to the present invention are: [ka] It includes one or more of the following.

[0047] For example, the organosilane molecule can be Silquest A171, available from MOMENTIVE.

[0048] (organic filler or inorganic filler) As mentioned above, the compositions of the present invention further comprise an organic or inorganic filler, which may be dispersed in the composition with or without a dispersing agent, to provide the adhesive with suitable viscosity and thixotropy, and therefore good dispensability onto the silicone and / or plastic surfaces to be joined by pneumatic and swirl dispensing systems.

[0049]

[0049] In a preferred embodiment, the organic or inorganic filler has gas barrier properties and solvent barrier properties and an average particle size distribution of 50 microns or less.

[0050]

[0050] The best adhesive performance has been achieved by using a layered talc filler, which ensures good dispersion in the polymer matrix of the final elastomeric material and also ensures good solvent / gas barrier properties. Therefore, in a more preferred embodiment, the organic or inorganic filler is a layered talc filler (e.g., Talc HAR, available from IMERYS).

[0051] As known to those skilled in the art, each component in the above-described composition has unique properties that contribute to imparting to the adhesive the appropriate reactivity and the desired final physical, chemical and mechanical properties.

[0052] The compositions for preparing the elastomeric adhesives of the present invention are capable of crosslinking rapidly and achieving high adhesion to the silicone and / or plastic surfaces to be joined.

[0053] In a second aspect of the present invention, there is provided an elastomeric adhesive prepared from a composition according to the first aspect of the present invention.

[0054] The prepared elastomeric adhesive is a single-component adhesive, so that mixing of the individual components prior to use is not required. The adhesive is used internally in inkjet printheads as a hydraulic adhesive to bond components of the inkjet printhead, for example, to bond a silicon chip to a plastic polyolefin-based container (hydraulic component) and / or to bond a plastic plug to the container. The adhesive can also be used to seal portions of the edges of flexible circuits to prevent ink from flowing under the flexible circuit and subsequently causing potential chemical and electrical problems.

[0055] Furthermore, the elastomeric adhesive can absorb stresses caused by the manufacturing process, protecting the final product from chip cracking during and after the manufacturing process. Final heating of the printhead during its life causes different expansion of the bonding materials (e.g., silicon and plastic container) as a result of thermal expansion coefficients; this mismatch causes a bending effect on the chip, resulting in fracture of the brittle silicon and rendering the printhead unusable. The elasticity of the adhesive ensures absorption of stresses caused in the printhead by the manufacturing process or occurring during storage.

[0056]

[0056] The elastomeric adhesives are also compatible with solvent-based inks once vulcanized. These inks can contain alcohols, glycols, glycoethers, ethers, esters, hydrocarbons, amides, lactones, and ketones. The adhesives contain additives specifically designed to give the polymer high adhesion to the backside of the printhead silicon chip, and additives that allow the adhesive to bond to the container plastic, which is usually polyolefin-based, to make it compatible with solvent-based inks.

[0057] According to a third aspect of the present invention, there is provided a method for preparing an elastomeric adhesive according to the second aspect of the present invention from a composition according to the first aspect of the present invention, comprising the steps of: a) reacting one or more sulfur donor molecules with an organometallic zinc catalyst to form a first zinc sulfide complex as an active crosslinking initiator; b) catalyzing a vulcanization reaction of one or more linear unsaturated hydrocarbon-based polymers with a first zinc sulfide complex to obtain a vulcanized polymer and a thiol; c) crosslinking the polymer chains of the vulcanized polymer obtained in step b) via polysulfide bridges between the units by a curing process, preferably a thermosetting process; A method is provided, comprising:

[0058]

[0058] The result is the present elastomeric adhesive.

[0059] In one embodiment, the method further comprises the step of: d) reacting a metal oxide, such as zinc oxide, with the thiol obtained in step b) to form a zinc complex.

[0060] In a further embodiment, the zinc complex is complexed with one or more organic ligands and then sulfurized to obtain a second zinc sulfide complex. The second zinc sulfide complex further participates in the vulcanization reaction of the polymer. Thus, in the context of the present invention, the addition of a metal oxide, such as zinc oxide, in the adhesive is intended to maximize the use of the by-product sulfide.

[0061] It should be noted that the first zinc sulfide complex and the second zinc sulfide complex herein may be identical or similar in structure.

[0062] In one embodiment, the method further comprises the step of: e) desulfurizing the polysulfide bridges with an organometallic zinc catalyst. Step e) is carried out to reduce the length of the crosslinked polymer and consequently increase the Young's modulus.

[0063] In one embodiment, the method further comprises the step of: f) vulcanizing a coupling agent having one or more unsaturations to participate in step c).

[0064] In a preferred embodiment, steps d), e) and f) are not performed in sequence.

[0065] In a preferred embodiment, step c) crosslinks the polymer chains of the vulcanized polymer of step b) via polysulfide bridges between the units by a thermosetting process.

[0066]

[0066] In a fourth aspect of the present invention, there is provided an inkjet printhead comprising an elastomeric adhesive according to the second aspect of the present invention, or prepared from a composition according to the first aspect of the present invention, or prepared by a method according to the third aspect of the present invention.

[0067]

[0067] In a fifth aspect of the present invention there is provided the use of an elastomeric adhesive according to the second aspect of the present invention, or prepared from a composition according to the first aspect of the present invention, or prepared by a method according to the third aspect of the present invention for bonding components inside an inkjet printhead.

[0068] For example, the elastomeric adhesive of the present invention may be used as a hydraulic adhesive inside an inkjet printhead to bond a chip to a reservoir and / or to bond a plug to a reservoir. The elastomeric adhesive of the present invention may also be used to seal a portion of the edge of a flexible circuit to prevent ink from flowing under the flexible circuit and subsequently causing possible chemical and electrical problems.

[0069] (Adhesive hardening) As mentioned above, the elastomeric adhesive of the present invention is heat-curable. Therefore, a curing system is utilized in the present application to heat-cure the elastomeric adhesive. Curing systems typically used in automated inkjet printhead manufacturing assembly lines include a heated air blower and / or an oven.

[0070] (thermal blower) FIG. 1 shows a hot air blower system that involves thermal reticulation of adhesive via heating of the silicon jets of an inkjet printhead.

[0071] As shown in Figure 1, heat is rapidly transferred from the silicone to the adhesive. The hot air blower system allows the manufacturing process to reach higher curing temperatures (compatible with the silicone components of the ejector group) in the relatively short time required for complete curing of the adhesive without damaging any other heat-sensitive components of the inkjet printhead. The time and temperature of the hot air blower can be adjusted to protect components near the plastic container and printhead from thermal damage due to heat transfer.

[0072] (oven)

[0072] When an oven is used as the curing system, the entire printhead is placed in a heated oven for a period of time at a certain temperature, where the heating is non-directional and results in all printhead components being heated.

[0073] It is important to prevent temperatures from reaching a critical temperature that may be dangerous to at least one component of the printhead. In an oven, more than one printhead can be heated simultaneously in parallel, which may increase the heating time beyond that required with a hot air blower.

[0074] The curing conditions and the resulting reactivity of the adhesive will be adapted for the application to protect all other components of the printhead from thermally induced damage. For example, if the maximum curing temperature above which at least one component of the printhead begins to be damaged is 90°C, then once the printhead components are bonded, it is better to place the entire printhead in an oven at a temperature below 90°C; otherwise, including a hot air blower in the production line is also an option to locally heat the silicon and / or plastic surfaces to be bonded to a higher temperature (e.g., up to about 130°C) for a short period of time (e.g., <3 minutes) without damaging the final printhead.

[0075] The degree of reticulation reached after the curing process will be high. The enthalpy consumed during the curing process, measured by a DSC instrument, will be higher than 50% of the total enthalpy available. [Example]

[0076] The characteristics of the elastomeric adhesive according to the present invention are evaluated in the following examples. It will be understood by those skilled in the art that the examples described below are merely illustrative and not limiting to illustrate embodiments of the present invention.

[0077] (Examples E1 to E4 and Comparative Examples C5 to C6) Table 1 shows exemplary adhesive compositions (by weight) of the present invention (E1-E4) and comparative examples (C5-C6). [Table 1]

[0078] (Method of Preparing the Elastomeric Adhesive of the Present Invention)

[0078] Taking formulation E3 as an example, an elastomeric adhesive according to the present invention was prepared by the following method.

[0079] The following ingredients were first placed in a container: 20.6 wt% polyisoprene-grafted maleic anhydride, 17.5 wt% polybutadiene-styrene, 29.65 wt% mesitylene, and 5.78 wt% Silquest A171. The ingredients were mixed in a mixer (ARE-250 THINKY, USA) for 9 cycles (10 min for each cycle) with a 5-minute pause after every 3 cycles. After the resulting mixture was cooled, 4.12 wt% zinc oxide, 5.48 wt% stearic acid, 7.09 wt% sulfur (mesh 150 μm), and 5.16 wt% Talc HAR were added to the mixture, which was then mixed in a mixer (ARE-250 THINKY, USA) for 3 cycles (10 min for each cycle) with a 5-minute pause after each single cycle. Finally, 4.62 wt% ZDBC as a zinc catalyst was added to the mixture and mixed for 10 min with a mixer (ARE-250 THINKY, USA).

[0080] Other elastomeric adhesives according to the present invention and their comparative adhesives were prepared in a similar manner.

[0081]

[0081] The prepared adhesive is cured using a hot air curing system at a maximum temperature of 135°C for a time period of not more than 3 minutes, and / or alternatively using an oven at a maximum cure temperature of 80°C for a time period of not more than 3 hours to ensure the following requirements for the elastomeric adhesive of the present invention: Stress resistance, High chemical resistance to both water-based and solvent-based inks, High crosslink density, High conversion rates (% of carbon-sulfur bond formation or C-H bond loss), High adhesion to the surfaces to be bonded (silicone or polyolefin-based plastics), Good flexibility, Good dispensing properties and scorch times, and Reduced air permeability.

[0082] A detailed description of these advantageous properties is provided below through experimental testing and / or analysis of the materials.

[0083] (stress resistance) The elastomeric adhesive of the present invention can absorb stresses caused by the manufacturing process and protect the final printhead from chip cracking during and after the manufacturing process. Final heating of the printhead during its life causes differential expansion of mating parts (e.g., silicon and plastic housing) due to different thermal expansion coefficients. This mismatch causes a chip bending effect, resulting in fracture of the brittle silicon and rendering the printhead unusable. However, the elasticity of the elastomeric adhesive of the present invention ensures absorption of stresses on the printhead caused by the manufacturing process or arising during storage.

[0084] (Chemical resistance to solvent-based inks)

[0084] Once the printhead manufacturing process is complete, the ink(s) are loaded into the reservoir(s). If the printhead is tri-color, three inks (typically cyan, magenta, and yellow) are loaded into three reservoirs. Typically, each reservoir needs to contain an ink.

[0085]

[0085] Once the printhead filled with ink is prepared, it is placed in its packaging and placed in an oven set at 45°C for 1 week, 3 weeks, 5 weeks, and 7 weeks for each storage time step. The sample is then removed from the oven and allowed to cool at room temperature for 2 hours. The packaging is opened, the printhead is placed in the printer, and a predefined print pattern is executed on a paper sheet. By observing the print pattern, it is possible to determine whether any defects have occurred in the hydraulic adhesive during storage. If any contaminating ink print is observed in the technical pattern, the chemical resistance of the adhesive is not considered to be sufficient.

[0086] The elastomeric adhesives of the present invention are formulated to be compatible with solvent-based inks used in inkjet printheads once vulcanized. These solvent-based inks typically contain alcohols, glycols, glycoethers, ethers, esters, hydrocarbons, amides, lactones, and ketones. The elastomeric adhesives of the present invention contain components capable of imparting high adhesion to the backside of the silicon chip of the printhead and also contain components capable of bonding the container plastic, which is typically polyolefin-based, to be compatible with the solvent-based inks.

[0087] In the present invention, to evaluate the chemical compatibility (or chemical resistance) between the elastomeric adhesive of the present invention and commonly used solvent-based inks, cyan, magenta, and yellow solvent-based inks were used. The ink compositions are shown in Table 2. [Table 2]

[0088]

[0088] Chemical compatibility was evaluated by filling three reservoirs of a printhead with each of the above solvent-based inks and holding them at 45°C for seven weeks, and observing the final failure of the printhead's mating components (hydraulics, plugs, beads on the circuit board) after 1, 3, 5, and 7 weeks. Properly cured adhesives of the present invention showed no detachment from any surface and / or any significant swelling.

[0089] The chemical resistance of the printhead and especially the hydraulic adhesive was specifically evaluated by observing the print quality after 1, 3, 5 and 7 weeks of storage at 45°C. Typically, adhesive failure becomes evident when unusual colors of the print pattern on the paper are observed, which is the result of ink mixing into the macrohydraulic areas of the printhead. Another possible defect is the absence of nozzles during the printing process as a result of loss of hydraulic closure of the printhead.

[0090] Table 3 shows the print quality of printheads using adhesives E1-E4 and C5-C6 after storage at 45°C for times 0 and 1, 3, 5 and 7 weeks. [Table 3]

[0091] The above results in Table 3 show that printhead print quality was good for E1-E4, while negative for C5 after 5 and 7 weeks. Thus, the chemical resistance of the elastomeric adhesive of the present invention is good, whereas the chemical resistance is moderate for comparative examples C5 and C6.

[0092] (Crosslink density) In the present invention, the crosslink density of the inventive and comparative elastomeric adhesives, once cured, was measured by this procedure as follows:

[0093]

[0093] Rubber samples were prepared by casting the adhesive inside an aluminum mold having the following three dimensions: 10 mm x 20 mm x 20 mm.

[0094]

[0094] The samples were cured under the appropriate desired curing conditions (hot air blower and / or oven) and after cooling and measuring the weight and volume, the samples were placed in a known volume of isooctane at room temperature.

[0095]

[0095] This organic solvent (isooctane) has a very high affinity for the polymer matrix of the elastomeric adhesive, resulting in swelling. After 2 minutes, the samples were then removed from the solvent and measured for final weight and volume.

[0096] The crosslink density of the adhesive samples was then calculated using the Flory Rehner formula:

number

[0097] For vulcanized rubber containing fillers, V r is obtained from the following formula:

number

[0098] Table 4 shows the crosslink density of the elastomeric adhesives of the present invention and comparative examples. The calculated crosslink density for most promising adhesives is 10 -3 mol / cm 3 For both Comparative Examples C5 and C6, the crosslink density was not available due to the difficulty in preparing the samples. [Table 4]

[0099] (conversion rate) In the context of the present invention, the conversion of the adhesive means the percentage of carbon-sulfur (C-S) bond formation or C-H bond loss. The conversion of the adhesive once cured was measured by FTIR spectroscopy.

[0100]

[0100] The vulcanization reaction involves a certain number of reaction steps that are difficult to monitor by FTIR. However, it has been observed that with FTIR spectroscopy it is possible to obtain satisfactory detection of the reaction simply by observing the appearance or disappearance of C-S and C-H bonds, respectively.

[0101]

[0101] 1603cm -1 Normalized to the reference peak at 1520 cm -1 By monitoring the increase in the signal, it was observed that the elastomeric adhesives of the present invention had an increase in absorbance value of at least 0.4, as shown in Table 4. For comparative examples C5 and C6, the increase in absorbance value was 0.14 and 0.30, respectively, which is significantly lower than the values ​​of the present invention (E1-E4).

[0102] (adhesion to the surfaces to be joined) The adhesion of elastomeric adhesives to surfaces (both silicone and polyolefin-based plastics) was tested by preparing at least 10 printheads on which the elastomeric adhesive was being tested. The adhesive was dispensed by a spiral or pneumatic dispensing system installed on the manufacturing assembly line and cured under appropriate selected conditions identified by analysis.

[0103]

[0103] The adhesive adhesion was evaluated by the "knife test": after dispensing the adhesive and the correct cure time, the tip was observed to determine if it held position.

[0104]

[0104] In particular, the "knife test" was carried out in the following manner. Remove the flexible circuit (or flat) from the printhead; Place the tip of the knife on the end of the chip and apply gentle pressure to create leverage. If the force applied causes chip removal, the evaluation test is negative with a rank of "KO" and complete removal of the chip with adhesive on the backside can be observed. If the force applied causes the chip to break or is difficult to remove, the evaluation test is positive and the ranking test is "good" or "very good."

[0105]

[0105] As shown in Table 4, all of the inventive examples and comparative examples exhibit acceptable adhesion ranging from a "moderate" level to "very good."

[0106] (Flexibility)

[0106] Typically, the flexibility or glass transition temperature of a polymeric material is measured indirectly by a DSC technique in which a heating ramp is performed at a set heating rate over a temperature range between room temperature and a higher temperature. If the material is elastic at room temperature, it will not exhibit any glass transition within the detection temperature range. Adhesives with glass transition temperatures below room temperature are essentially bulky free bodies within the polymer structure. Thermal expansion, vibrations, etc. of the joining surfaces during or after the manufacturing process are consequently absorbed by the material.

[0107]

[0107] However, because the glass transition temperatures of the elastomeric adhesives E1 to E4 according to the present invention are significantly lower than zero degrees Celsius, the precise values ​​obtained by a DSC instrument (which is less accurate at cold temperatures below 0°C) suffer from high instrumental error. Therefore, in this application, the glass transition temperatures of the elastomeric adhesives E1 to E4 as well as C5 and C6 were evaluated by placing the adhesives in a refrigerator at -45°C and scoring the adhesive with the tip of a knife. It was observed that none of the adhesives were in a glassy state, and all adhesives remained flexible down to temperatures as low as -40°C. As can be seen from the above, the glass transition temperatures of the elastomeric adhesives E1 to E4 are all below -30°C.

[0108] (Air permeability)

[0108] Printing and storage tests performed on the printheads did not reveal any air permeability to the elastomeric adhesive used to bond the printhead components once properly dispensed and cured.

[0109]

[0109] The presence of air in the printhead microhydraulics can be serious and can cause nozzle loss during the life of the device.

[0110]

[0110] The various technical features described above can be combined in any manner. Although not all possible combinations of the various technical features are described, all combinations of these technical features should be considered to be within the scope described in this specification, unless they are inconsistent.

[0111]

[0111] While the present invention is described in conjunction with the embodiments, those skilled in the art will understand that the above description and drawings are merely illustrative and not limiting, and that the present invention is not limited to the disclosed embodiments. Various modifications and variations are possible without departing from the concept of the present invention. [Item 1] Linear unsaturated hydrocarbon-based polymers containing at least one non-aromatic unsaturation in at least one monomer, including polyisoprene-grafted maleic anhydride and polybutadiene-styrene; one or more sulfur donor molecules, and Organometallic Zinc Catalyst 1. A method for preparing an elastomeric adhesive for bonding components inside an inkjet printhead from a composition comprising: a) reacting the one or more sulfur donor molecules with the organometallic zinc catalyst to form a first zinc sulfide complex as an active crosslinking initiator; b) catalyzing a vulcanization reaction of the one or more linear unsaturated hydrocarbon-based polymers with the first zinc sulfide complex to obtain a vulcanized polymer and a thiol; c) crosslinking the polymer chains of said vulcanized polymer obtained in step b) via polysulfide bridges between the units by a curing process, preferably a thermosetting process; A method comprising: [Item 2] The composition comprises: 15% to 60% of the linear unsaturated hydrocarbon-based polymer; 3.3% to 10.6% of the one or more sulfur donor molecules, and 2.0% to 7.0% of said organometallic zinc catalyst 2. The method of claim 1, wherein the percentages are calculated based on the total weight of the composition. [Item 3] 3. The method according to claim 1, wherein the linear unsaturated hydrocarbon-based polymer comprises one of the following:

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Claims

1. A linear unsaturated hydrocarbon polymer, wherein at least one of the monomers constituting the linear unsaturated hydrocarbon polymer contains at least one non-aromatic unsaturation. one or more sulfur donor molecules, and Organometallic Zinc Catalyst 1. A method for preparing an elastomeric adhesive for bonding components inside an inkjet printhead from a composition comprising: the linear unsaturated hydrocarbon-based polymer comprises polyisoprene-grafted maleic anhydride and polybutadiene-styrene; a) reacting the one or more sulfur donor molecules with the organometallic zinc catalyst to form a first zinc sulfide complex as an active crosslinking initiator; b) catalyzing a vulcanization reaction of the linear unsaturated hydrocarbon-based polymer with the first zinc sulfide complex to obtain a vulcanized polymer and a thiol; c) cross-linking the polymer chains of the vulcanized polymer obtained in step b) through polysulfide bridges between the units by a curing process; A method comprising:

2. The composition comprises: 15% to 60% of said linear unsaturated hydrocarbon-based polymer; 3.3% to 10.6% of the one or more sulfur donor molecules, and 2.0% to 7.0% of said organometallic zinc catalyst 10. The method of claim 1, comprising:

3. 3. The method of claim 1 or 2, wherein the linear unsaturated hydrocarbon-based polymer comprises one of the following: 【Chemistry 1】 where m+n is equal to 113 and neither m nor n is equal to zero. 【Chemistry 2】 where (x+z) / (x+y+z) equals 20% and y / (x+y+z) equals 80%. and 【Transformation 3】 where x / (x+y) is equal to 33% and y / (x+y) is equal to 67%.

4. 4. The method according to any one of claims 1 to 3, wherein the one or more sulfur donor molecules are selected from elemental sulfur or dispersed sulfur.

5. The method described in claim 4, wherein the one or more sulfur donor molecules are soluble crystalline sulfur having an average particle size distribution of 100 mesh or less.

6. The organometallic zinc catalyst is 【Chemistry 4】 The method of any one of claims 1 to 5, wherein the compound is selected from the group consisting of:

7. 6. The method of any one of claims 1 to 5, wherein the organometallic zinc catalyst is selected from the group consisting of zinc ethylphenyldithiocarbamate (ZEPC), zinc dibutyldithiocarbamate (ZDBC), zinc guanidine, and zinc isopropylxanthate.

8. The composition comprises: metal oxides, one or more organic ligands selected from C18 to C30 carboxylic acids, aliphatic amines or aromatic amines; one or more hydrocarbon-based organic solvents or oils having a boiling point equal to or greater than the cure temperature of the composition; a coupling agent consisting of an organosilane molecule having one or more unsaturations, and / or an organic or inorganic filler that can be dispersed in the composition and further has gas barrier properties, solvent barrier properties, and an average particle size distribution of 50 microns or less; The method of any one of claims 1 to 7, further comprising:

9. The method described in claim 8, wherein the organic filler or inorganic filler is a layered talc filler.

10. The composition comprises: 1.9% to 6.2% of said metal oxide; 2.5% to 8.5% of said one or more organic ligands; 14% to 45% of said one or more hydrocarbon-based organic solvents or oils; 2.5% to 9.0% of said coupling agent, and / or 1.5% to 12% of said organic or inorganic filler 10. The method of claim 8 or 9, comprising:

11. the one or more organic ligands are 【Transformation 5】 The method according to any one of claims 8 to 10, wherein the compound is selected from the group consisting of:

12. The coupling agent is 【Transformation 6】 The method according to any one of claims 8 to 11, selected from the group consisting of:

13. The method described in claim 8, wherein the metal oxide is zinc oxide, and the method further comprises the step of d) reacting the metal oxide with the thiol obtained in step b) to form a zinc complex.

14. 14. The method according to any one of claims 1 to 13, wherein the method further comprises the step of: e) desulfurizing the polysulfide bridges with the organometallic zinc catalyst.

15. 15. The method of any one of claims 1 to 14, wherein the method further comprises the step of: f) vulcanizing a coupling agent having one or more unsaturations to participate in step c).

16. Use of an elastomeric adhesive prepared by the method of any one of claims 1 to 15 for bonding components inside an inkjet printhead.

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