Abstract:
A solvent resistant printhead having a barrier deposited and intercalating into the various polymeric materials on the printhead is disclosed. The deposition process may be performed at the various level of production depending on what material or surface requires protection from the solvent. The barrier may include a base coating and an outer coating. The base coating may include an intercalate layer deposited on the printhead and intercalating into the various polymeric materials and a tie layer deposited on the intercalate layer. The outer coating may be a self-assembled monolayer deposited on the base coating.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    This patent application is related to and claims priority to U.S. Provisional Patent Application Ser. No. 61/394,474 entitled “Solvent Resistant Printhead” which was filed on Oct. 19, 2010. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    None. 
       REFERENCE TO SEQUENTIAL LISTING, ETC. 
       [0003]    None. 
       BACKGROUND 
       [0004]    1. Technical Field 
         [0005]    The present disclosure relates to micro-fluid ejection devices. More particularly, it relates to inkjet printheads using solvent based inks. 
         [0006]    2. Description of the Related Art 
         [0007]    The art of printing images with micro-fluid technology is relatively well-known. In the field of micro-fluid ejection devices, current nozzle plate materials and the upilex/phenolic ablated materials have been engineered to be compatible with aqueous based inks. The aqueous based inks are suitable for thermal inkjet due to water nucleation kinetics and pumping effectiveness. Aqueous based inks are traditionally ejected onto porous media such has cellulose pulp paper or photopaper. The aqueous base ink surface tensions are low enough to establish wetting onto the paper and this wetting enables penetration into the porous media and provides good coverage yielding good print quality. Unfortunately, use of the aqueous based inks on other substrates, specifically low surface energy, non-porous media such as PVC, PET, ceramics, PP, coated papers, and other non-porous media used in the industrial market, has shown adhesion issues due to the inability of the aqueous based inks to wet the surface and penetrate into the substrate. For printing on non-porous media, solvent-based inks are being used. 
         [0008]    Solvents that are typically used in solvent-based inks generally have lower surface tension compared to water and will wet lower surface energy surfaces/substrates. Solvent-based inks, however, may not be compatible with the ablated or nozzle plate materials, encap, diebond, TAB circuits, covercoat and other organic materials used in printheads designed for aqueous based inks. The solvents in solvent-based inks have lower surface tensions and increased solubility with organic materials allowing them to diffuse and swell the various polymeric materials of the printhead. Diffusion of the solvent and moisture into the material may lead to an accelerated corrosion failure, premature loss of adhesion, and print quality defects. 
         [0009]    Accordingly, a need exists to provide an improved solution for printheads using solvent-based inks. 
       SUMMARY OF THE INVENTION 
       [0010]    The above-mentioned and other problems become solved with a solvent-resistant printhead. The printhead having a polymeric material may include a barrier to protect the printhead against corrosion and loss of adhesion that may be caused by exposure to solvent-based inks. 
         [0011]    In one example embodiment, the barrier may include a base coating and an outer coating. The base coating may include an intercalate layer and a tie layer. The intercalate layer may be deposited on the printhead and may intercalate into the various polymeric materials of the printhead. The tie layer may be deposited on and may chemically bond with the intercalate layer. The intercalate layer and the tie layer may be oxide layers. The intercalate layer may be an aluminum oxide layer while the tie layer may be a silicon dioxide layer. The outer coating may be a self-assembled monolayer deposited on the base coating. 
         [0012]    The barrier may encapsulate all the polymeric based materials and free surfaces on the printhead, leading to improve solvent resistance. Once the barrier is deposited on the printhead assembly, solvent and moisture may be prevented from reaching or penetrating the polymeric materials thus providing corrosion protection and improved solvent compatibility to the printhead assembly. The intercalation of the intercalate layer into the various polymeric materials of the printhead may enable better adhesion of the barrier to the printhead assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    A more thorough understanding of the example embodiments may be had from the consideration of the following detailed description taken in conjunction with the accompanying drawings. 
           [0014]      FIG. 1  is a diagrammatic view of an example embodiment of an advanced surface modification employing the barrier in the present disclosure. 
           [0015]      FIG. 2  is a detailed view of the base coating of  FIGS. 1 . 
           [0016]      FIG. 3  is a flowchart depicting a method of forming the barrier of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    It is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use herein of “including,” “comprising,” or “having” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings. 
         [0018]    Referring now to the drawings and more particularly to  FIG. 1 , there is shown one example embodiment of the barrier  10  of the present disclosure. The barrier  10  may consist of a base coating  20  deposited on the substrate  15  and an outer coating  25 , such as a self-assembled monolayer, deposited on the base coating  20 . The substrate  15  in the present disclosure may include various polymeric materials used in making the printhead. The barrier  10  may have a thickness range of about 100 Angstrom to about 400 Angstrom and may encapsulate all free surfaces of a finished printhead assembly (not shown) to protect the printhead assembly from various solvents and moisture which may cause corrosion and loss of adhesion between the bather  10  and the printhead assembly by preventing solvent from reaching or penetrating the polymeric materials. The self-assembled monolayer  25  is a one molecule thick layer of material that chemically bonds to the base coating  20  in an ordered way as a result of physical or chemical forces during the deposition process and may be created by the chemisorption of hydrophilic head groups  25   a  onto the base coating  20  from either the vapor or liquid phase followed by a slow two-dimensional organization of hydrophobic tail groups  25   b . The hydrophilic head groups  25   a  may assemble together on the base coating  20 , while the hydrophobic tail groups  25   b  may assemble far from the base coating  20 . The self-assembled monolayer  25  may be deposited by physical vapor deposition process and a covalent bonding may occur between the self-assembled monolayer  25  and the base coating  20  during deposition. The deposition of the self-assembled monolayer  25  on the base coating  20  may provide sufficient hydrophobic character to the barrier  10  and may cause the ink (not shown) to be less wetting. The contact angle of water for the self-assembled monolayer  25  is from about 90 degrees to about 120 degrees. 
         [0019]      FIG. 2  is a detailed view of the base coating  20  of  FIG. 1  being deposited on a polymeric material  15   a  of the substrate  15 . The base coating  20  may include an intercalate layer  20   a  and a tie layer  20   b . The intercalate layer  20   a  may enable adhesion of the barrier  10  to the printhead assembly. To achieve a better adhesion to the printhead assembly, the intercalate layer  20   a  may be deposited such that the intercalate layer  20   a  intercalates into the various polymeric materials  15   a  of the substrate  15 . In one example embodiment, the intercalate layer  20   a  may be an Al 2 O 3  layer deposited by atomic layer deposition. The use of an Al 2 O 3  layer as an example intercalate layer  20   a  may not be considered limiting as other layers with different chemical compositions may be used as an intercalate layer  20   a  for the present disclosure. 
         [0020]    Atomic layer deposition is a process of applying thin films to various substrates with atomic scale precision similar in chemistry to chemical vapor deposition, except that in an atomic layer deposition, an atomic layer deposition reaction may break a chemical vapor deposition reaction into two half-reactions and may keep the precursor materials separate during the reaction. Atomic layer deposition film growth may be self-limited and may be based on surface reactions, which may make achieving atomic scale deposition control possible. By keeping the precursors separate throughout the coating process, atomic layer thickness control of film grown may be obtained as fine as atomic/molecular scale per monolayer. 
         [0021]    The atomic layer deposition process may enable the intercalate layer  20   a  to intercalate into the various polymeric materials  15   a  with atomic scale precision and uniformity. Once the intercalate layer  20   a  is formed, chemical vapor deposition may be employed to deposit the tie layer  20   b  on the intercalate layer  20   b . The tie layer  20   b  may be deposited on the intercalate layer  20   a  such that the intercalate layer  20   a  and the tie layer  20   b  chemically bonds together and sufficient hydroxyl groups are provided for the deposition of the self-assembled monolayer  25 . In one example embodiment, the tie layer  20   b  may be a SiO2 layer deposited by chemical vapor deposition process on the intercalate layer  20   a . The use of a SiO2 layer as an example tie layer  20   b  may not be considered limiting as other layers with different chemical compositions may be used as a tie layer  20   b  for the present disclosure. 
         [0022]      FIG. 3  is a flowchart depicting one example method of forming the barrier  10  of  FIG. 1 . At block  100 , an intercalate layer  20   a  may be deposited on the substrate  15  such that the intercalate layer  20   a  intercalates into the polymeric material  15   a  of the substrate  15 . In one example embodiment, atomic layer deposition may be used to deposit the intercalate layer  20 . 
         [0023]    At block  101 , the tie layer  20   b  is deposited on the intercalate layer  20   a . The tie layer  20   b  may be deposited by chemical vapor deposition process. During the deposition, the tie layer  20   b  may chemically bond with the intercalate layer  20   a  forming the base coating  20 . The deposition of the tie layer  20   b  may also provide the hydroxyl groups (not shown) for the deposition of the self-assembled monolayer  25 . 
         [0024]    At block  102 , the self-assembled monolayer  25  may be deposited on the base coating  20 , particularly, the tie layer  20   b . In one example embodiment, the self-assembled monolayer  25  may be an octadecyltrichlorosilane self-assembled monolayer. In another example embodiment, the self-assembled monolayer  25  may be a perfluorodecyl-trichlorosilane self-assembled monolayer. In yet another example embodiment, undecenyltrichlorosilane self-assembled monolayer may be used. Other chemicals having alkyltrichlorosilanes may be used as self-assembled monolayer  25  in the present disclosure. 
         [0025]    The foregoing description of several methods and an embodiment of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.