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EP-4735260-A1 - EPOXY-BASED UV-VIS-CURABLE COMPOSITIONS

EP4735260A1EP 4735260 A1EP4735260 A1EP 4735260A1EP-4735260-A1

Abstract

The invention relates to A UV-VIS-curable composition comprising: a) about 20 to about 40 wt.% of at least one aromatic epoxide component, wherein the epoxy functionality is between 2 to 3; b) about 30 to about 50 wt.% of at least one cycloaliphatic epoxide component, b) being different than a); c) about 2 to about 20 wt.% of at least one ester-containing component; d) about 2 to about 12 wt.% of at least one fluorine-based component; e) about 1 to about 15 wt.% of at least one cationic photoinitiator; f) more than about 3 wt.% of at least one additive selected from the group consisting of surfactants and adhesion promoters or mixtures thereof; g)0 to 5 wt.% of at least one photosensitizer; and wherein the composition has a Tg-value of less than 100 °C and a viscosity between about 1000 m-Pas to about 4000 m-Pas at 25 °C, wherein the weight percents are based on the total weight of the UV-VIS-curable composition. The invention further relates to an inkjet printhead comprising said composition and a method of coating a silicon substrate, preferably a silicon wafer, with said UV-VIS-curable composition.

Inventors

  • CIAMPINI, DAVIDE
  • PRUDENTI, Noemi

Assignees

  • Sicpa Holding SA

Dates

Publication Date
20260506
Application Date
20240626

Claims (10)

  1. 1 . A UV-VIS-curable composition comprising: a) about 20 to about 40 wt.% of at least one aromatic epoxide component, wherein the epoxy functionality is between 2 to 3; b) about 30 to about 50 wt.% of at least one cycloaliphatic epoxide component, b) being different than a); c) about 2 to about 20 wt.% of at least one ester-containing component; d) about 2 to about 12 wt.% of at least one fluorine-based component; e) about 1 to about 15 wt.% of at least one cationic photoinitiator; f) more than about 3 wt.% of at least one additive selected from the group consisting of surfactants and adhesion promoters or mixtures thereof; g) 0 to 5 wt.% of at least one photosensitizer; and wherein the composition has a Tg-value of less than 100 °C and a viscosity between about 1000 m Pas to about 4000 m Pas at 25 °C, wherein the weight percents are based on the total weight of the UV-VIS-curable composition.
  2. 2. The UV-VIS-curable composition according to claim 1 , wherein the Tg-value is less than 90 °C, preferably less than 80 °C.
  3. 3. The UV-VIS-curable composition according to claims 1 or 2 having a viscosity between about 1000 m Pas to about 3000 m Pas.
  4. 4. The UV-VIS-curable composition according to claims 1 to 3, wherein the component (a) is present in an amount between about 20 to about 30 wt.%, prerebaly between about 20 to about 25 wt.%, the weight percents being based on the total weight of the UV-VIS-curable composition.
  5. 5. The UV-VIS-curable composition according to claims 1 to 4, wherein the component (b) is present in an amount between about 30 to about 35 wt.%, the weight percents being based on the total weight of the UV-VIS-curable composition.
  6. 6. The UV-VIS-curable composition according to claims 1 to 5, wherein the component (c) is a cyclic ester, preferably caprolactone.
  7. 7. A UV-VIS-curable composition according to any one of the claims 1 to 6 wherein the component e) is selected from the group consisting of triphenylsulfonium salts, diazonium salts, diaryliodonium salts, ferrocenium salts, metallocene compounds and mixtures thereof.
  8. 8. A method for coating a silicon substrate, wherein the method comprises: a) providing a silicon substrate, in particular silicon wafer; b) depositing the UV-VIS-curable composition according to claims 1 to 7; c) rotationally spreading out said composition, in particular by spin-coating; d) at least partially, preferably completely, evaporating the solvent from said composition; e) applying a mask to the UV-VIS-curable composition to generate a photolithographic pattern; f) at least completely removing any uncured UV-VIS-curable composition; g) at least partially curing said composition.
  9. 9. An inkjet printhead comprising any of the UV-VIS-curable composition recited in any one of claims 1 to 7, in at least a partially cured state.
  10. 10. A method of manufacturing an inkjet printhead comprising the UV-VIS-curable compositions of any of the claims 1 to 7.

Description

EPOXY-BASED UV-VIS-CURABLE COMPOSITIONS FIELD OF THE INVENTION [001] The present invention relates to the technical field of UV-VIS-curable compositions useful for manufacturing an inkjet printhead, its use and a method for manufacturing an inkjet printhead assembly comprising the UV-VIS-curable composition. BACKGROUND OF THE INVENTION [002] A typical inkjet printhead cartridge, as described in the patent EP 1896262 B1 (see figure 1 therein) or in figure 1 , is made of a printhead ejection assembly constituted by a printhead chip bonded to a flexible printed circuit. The printhead silicon chip, also known as silicon ejector group, houses the electrical and hydraulic components to address the ink towards the various ejecting sites, energizing it on demand, to produce ink droplets for printing. A nozzle plate is applied on the top surface of the chip, to provide the nozzles for ink ejection. The whole ejection assembly is in turn bonded to a cartridge that contains the ink reservoir, closed by a lid. Suitable ink slots are present in the cartridge body to allow the ink to get the printhead chip and to arrive to the microfluidic circuit, either through the slots machined into the chip or from the chip edge, depending on the printhead layout. [003] In the field of inkjet printing used in the solvent-based ink and water-based ink formulations, the materials used for protecting electronic component and defining microhydraulics, are usually epoxy or unsaturated resins. This material can react through UV-VIS-curable process. The benefit of this method is the capability to control the degree of cross-linking of the composition. [004] One of the state-of-the-art problems are the defects in the manufacturing process of the silicon ejector group. The ejector group consists of a CMOS part and a MEMS part. The CMOS unit consists of a series of conductive and insulating layers used in order to manage the electrical signals. Into the MEMS area is realized the geometry of the resistors required to generate the ink bubble. Different layers of metal(s) are needed to eject the ink, but the presence of layers at different thickness create topographies that introduce different gaps between silicon wafer and nozzle plate. The crosslinking of the UV-VIS-curable composition used to manufacture the inkjet printhead, in other term the contraction driven by the crosslinking and solvent evaporation process, does not exacerbates the gap issue, thereby compromising the protection and sealing of interfaces once the orifice layer is thermally bonded onto the microhydraulic. [005] Thus, there is a need to develop a UV-VIS-curable composition in order to reduce the gap unevenness and provide a smooth surface between nozzle plate and silicon wafer bonded to UV-VIS composition, with the aim of optimizing the interface that influences the behavior of the ink in the printhead. [006] Furthermore, due to various types of inks used i.e. water- and solvent-based, the UV-VIS- curable composition should be compatible with such inks. The UV-VIS-curable composition should possess high chemical resistance and the proper mechanical flexibility for the application. As the deposition of the UV-curable composition on the silicon substrate is performed by means of spin-coating, the composition should have the right viscosity value. SUMMARY OF THE INVENTION [007] In a first aspect the present invention relates to to a UV-VIS-curable composition comprising: a) 20 to 40 wt.% of at least one aromatic epoxide component, wherein the epoxy functionality is between 2 to 3; b) 30 to 50 wt.% of at least one cycloaliphatic epoxide component, b) being different than a); c) 2 to 20 wt.% of at least one ester-containing component; d) 2 to 12 wt.% of at least one fluorine-based component; e) 1 to 15 wt.% of at least one cationic photoinitiator; f) more than 3 wt.% of at least one additive selected from the group consisting of surfactants and adhesion promoters; g) 0 to 5 wt.% of at least one photosensitizer; and wherein the composition has a Tg-value of less than 100 °C and a viscosity between about 1000 m Pas to about 4000 m Pas at 25 °C, wherein the weight percents are based on the total weight of the UV-VIS-curable composition. [008] In a second aspect the invention relates to an inkjet printhead comprising the UV-VIS-curable composition as described herein, in at least partially cured state. [009] In a third aspect, the invention relates to a method for coating a silicon substrate, wherein the method comprises: a) providing a silicon substrate, in particular silicon wafer; b) depositing the UV-VIS-curable composition, described herein; c) rotationally spreading out said composition, in particular by spin-coating; d) at least partially, preferably completely, evaporating the solvent from said composition; e) applying a mask to the UV-VIS-curable composition to generate a photolithographic pattern; f) at least completely removing any uncured UV-VIS-curable composition;