Printing – Processes – With heating or cooling
Reexamination Certificate
2001-04-19
2003-02-04
Evanisko, Leslie J. (Department: 2854)
Printing
Processes
With heating or cooling
C101S035000, C101S483000, C065S120000, C118S072000, C427S255150
Reexamination Certificate
active
06513435
ABSTRACT:
BACKGROUND
The invention provides for a method for modifying a surface of a solid substrate, in particular glass, ceramic, and/or porcelain as well as substances made by this method.
Solid substrates and materials are used in domestic and industrial applications as well as in research and development. The natural surface of solid substances is not suitable for a number of applications due to heterogeneous structures or porosity.
It is known how to modify the surface of a solid substrate chemically, physically or biologically. The modification can be done using oils, wax or varnish, or by radioactive radiation, sand blasting, or depositing bio-molecules. Chemical modification is widely used in industrial or craft applications. Chemical modification of a surface of an amorphous substance is achieved through the use of liquids, for example aggressive acids or alkalines.
The physical-chemical structure of the top layer, that is to say the layer that is to be modified, determines the coating process. Known methods are acid baths, waxing, flaming or plasma or corona pre-treatment of, for example, un-polarised plastics. The surface can also be modified through depositing a layer of adhesion promoter, for example a conversion layer.
DE3511720 discloses a multi-step process which serves to produce hydrophilic glass surfaces on glass sheets. The sheets are treated with a liquid alkaline phosphate glass cleaner and, after rinsing with water, with a solution containing phosphoric acid.
U.S. Pat. No. 558,515 discloses a process where a printing ink together with a silane adhesion promoter are deposited directly onto a glass surface.
In particular the surfaces of glass, ceramic, porcelain or crystals can be such that due to the surface energy a modification using liquid substances is only limited or not possible at all. The surface energy and the polarity of the surface are the critical factors in moistening with liquids and for the success of the surface modification as well as for the subsequent adhesion of modifying layers that are deposited on the surface.
EP0594171 discloses a process and apparatus for the modification of the surface activity of a silicate glass substrate. Hydrophilisation is achieved by having a silicon-containing coating applied as SiO
x
by flame-pyrolytic decomposition of the organosilicon substance(s). This process for modifying silicate glass facilitates subsequent processes such as depositing a layer of varnish.
AT-PS381693 discloses a process to modify the surface of a silicate glass substrate to give it hydrophilic properties through depositing a sulphonate-organosilicon compound on the surface of the substrate and subsequently drying it.
DD 232 429 B1 and DD 236 758 A1 disclose a process where a flame-hydrolysis burner is used under ordinary atmospheric conditions to coat a metallic dental prosthesis part with silicon oxide.
While the prior art discloses processes for the modification of surfaces of solid substrates, in particular surfaces of glass, ceramic, porcelain and others, it is not possible to deliver reproductible, homogeneous surface properties. This is mainly due to the fact that the surface structure of a solid substrate always affects a directly deposited layer of silicon oxide. Local variation in density and chemical modification occur naturally on the surface of the substrate and these cause a variation in the adhesion of the silicon oxide, resulting in an inhomogeneous coating.
When printing ink and silane adhesion promoter are deposited directly onto the surface then this modification of the surface causes a negative interaction between the natural OH-groups on the surface and the silane adhesion promoter. Therefore the non-reproductible, non-homogeneous properties of the surface cause a non-satisfactory adhesion of the modifying layer to the surface.
Attempting a chemical treatment of a glass surface with the objective or providing a uniformly structured and homogeneous surface has the disadvantage, that these treatments can only be applied after the glass ribbon is separated into individual glass sheets so that they can be immersed in an immersion bath. The immersion treatment requires a large apparatus. The hydrophilic coating has organic traces, their interaction with the layers deposited later is undesirable. If the treated surface is part of a container or a pipe, it could also cause undesirable interactions with the solutions being stored in a container or with the liquids being transported through the pipe.
Additional problems can arise with trapped moisture on surfaces on glass-like, solid substrates. The moisture is trapped in gel-films that have a negative affect on the adhesion of the layers to be deposited. A reduction in the gel-film in a homogeneous and reproductible way is not known in the art.
The quality of the modification of the surface also depends on the deposited or generated reactive groups as these form the basis for a strong adhesion of the subsequently deposited layers. The known processes do not achieve a sufficient density of reactive OH-Groups, this results in reduced adhesion of the subsequently deposited layers.
SUMMARY OF THE INVENTION
The technical problem addressed by the invention is to provide a process that modifies the amorphous surfaces of solid substrates, in a way that produces reproducible, homogeneous surfaces with a high density of reactive OH-Groups and simultaneously creates a micro-retentive surface by reducing the gel-film.
The invention solves the technical problem by providing a process for modifying a surface of an amorphous substance; this process comprises the following steps:
Modification of the surface with at least one oxidising flame; and
Modification of the surface with at least one silicatising flame.
This combined treatment of a surface with at least one oxidising and at least one silicatising flame produces a homogeneous, micro-retentive surface with a high density of reactive groups.
The invention provides for a process that has the advantage of reducing the moisture that is present as non-homogeneous gel-films on the amorphous surface of solid substrates.
Surprisingly, the process reduces the gel-film in a way that is reproducible. The gel-film properties are determined by the existing amorphous structure and the age of the gel-film. In the first step of the process, the oxidising flame reduces the gel-film and the trapped moisture. The reduction of the gel-film provides reproducible, homogeneous surface properties.
In the second step, a surface created during the first step is treated with a silicatising flame and a silicon oxide layer is deposited. The layer thickness is up to 60 nm, preferably 5 to 50 nm, more preferably 10 to 30 nm and the layer is characterised by a high density of reactive OH-groups. The uniformity and excellent adhesion properties of the deposited layer of silicon oxide are derived through the combination of the first and second step of the process. It is advantageous to select a number of flames so that 1 to 5 oxidising and silicatising flames modify the surface. Preferably, the flame temperature is in the range 900° C. to 1200° C. and the solid substance is heated up to 50° C. and 100° C. Preferably, flaming continues for the duration of 0.1 sec to 5 sec, more preferably for the duration of 0.1 sec to 1 sec.
The reactive groups are the chemical basis for a strong chemical adhesion of the subsequently deposited, surface modifying layers, such as layers of wax, varnish or ink.
When the amorphous substance is glass, then the resulting density of OH-groups on solid surfaces treated by the present invention is 2 to 5 times higher than on untreated surfaces.
The silicon oxide layer or silicate layer deposited during the second step exhibits a sub-microscopic roughness. This roughness enables a significantly improved adhesion of all subsequently deposited layers. The oxidising and the silicatising process steps produce a reproducible, homogeneous, micro-retentive surface. The combination of both process steps surprisingly gives a reduction in the gel-film and
Evanisko Leslie J.
ISIMAT GmbH Seibdruckmaschinen
Morriss Bateman O'Bryant & Compagni
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