Patent Application
20060019043
In recent years, a significant industry has developed which involves the application of customer-selected designs, messages, illustrations, and the like (referred to collectively hereinafter as “images”) on articles of clothing, such as T-shirts, sweat shirts, and the like. These images may be commercially available products tailored for a specific end-use and printed on a release or transfer paper, or the customer may generate the images on a heat transfer paper. The images are transferred to the article of clothing by means of heat and pressure, after which the release or transfer paper is removed.
Heat transfer papers having an enhanced receptivity for images made by wax-based crayons, thermal printer ribbons, ink-jet printers, laser-jet printers, and impact ribbon or dot-matrix printers, are well known in the art. Typically, a heat transfer material includes a cellulosic base sheet and an image-receptive coating on a surface of the base sheet. The image-receptive coating usually contains one or more film-forming polymeric binders, as well as, other additives to improve the transferability and printability of the coating. Other heat transfer materials include a cellulosic base sheet and an image-receptive coating, wherein the image-receptive coating is formed by melt extrusion or by laminating a film to the base sheet. The surface of the coating or film may then be roughened by, for example, passing the coated base sheet through an embossing roll.
Much effort has been directed at generally improving the transferability of an image-bearing laminate (coating) to a substrate. For example, an improved cold-peelable heat transfer material has been described in U.S. Pat. No. 5,798,179, which allows removal of the base sheet immediately after transfer of the image-bearing laminate (“hot peelable heat transfer material”) or some time thereafter when the laminate has cooled (“cold peelable heat transfer material”). Moreover, additional effort has been directed to improving the crack resistance and washability of the transferred laminate. The transferred laminate must be able to withstand multiple wash cycles and normal “wear and tear” without cracking or fading.
Various techniques have been used in an attempt to improve the overall quality of the transferred laminate and the article of clothing containing the same. For example, plasticizers and coating additives have been added to coatings of heat transfer materials to improve the crack resistance and washability of image-bearing laminates on articles of clothing.
Heat transfer papers generally are sold in standard printer paper sizes, for example, 8.5 inches by 11 inches. Graphic images are produced on the transferable surface or coating of the heat transfer paper by any of a variety of means, for example, by ink-jet printer, laser-jet printer, laser-color copier, other toner-based printers and copiers, and so forth. The image and the transferable surface are then transferred to a substrate such as, for example, a cotton T-shirt. In some circumstances it is desirable that the transferable surface only transfer in those areas where there is a graphic image, thus reducing the overall area of the substrate that is coated with the transferable coating. Some papers have been developed that are “weedable”, that is, portions of the transferable coating can be removed from the heat transfer paper prior to the transfer to the substrate. Weeding involves cutting around the printed areas and removing the coating from the extraneous non-printed areas. However, such weeding processes can be difficult to perform, especially around intricate graphic designs. Therefore, there remains a need in the art for improved weedable heat transfer papers and methods of application. Desirably, the papers and methods provide good image appearance and durability.
In accordance with one embodiment of the present invention, a method of applying an image to a substrate is disclosed that includes the steps of:
a) imaging a printable surface of a first image transfer material to form an imaged surface having a printed area and a non-printed area on the first image transfer material;
b) providing a second image transfer material comprising an outer layer, the outer layer comprising a film forming binder and thermoplastic particles;
c) positioning the outer layer of the second image transfer material adjacent the imaged surface of the first image transfer material;
d) transferring a portion of the outer layer of the second image transfer material to the printed area of the imaged surface while transferring a lesser portion of the outer layer of the second image transfer material to the non-printed area to form a coated imaged surface having a non-printed area with less coating than the printed area; and
e) thereafter, transferring the coated image to a substrate.
In accordance with another embodiment of the present invention, a method of applying an image to a substrate is disclosed that includes the steps of:
a) providing a first image transfer material including an outer layer, the outer layer including a film forming binder and thermoplastic particles, the outer layer further including a printable surface;
b) imaging the printable surface of the first heat transfer material to form an imaged surface having a printed area and a non-printed area on the first image transfer material;
c) providing a second image transfer material having a substantially non-porous surface;
d) positioning the imaged outer layer of the first image transfer material adjacent the substantially non-porous surface of the second image transfer material;
e) transferring the printed area and a first portion of the outer layer of the first image transfer material to the substantially non-porous surface of the second image transfer material to form a coated imaged surface on the second image transfer material having a non-printed area with less coating than the printed area; and
f) thereafter, transferring the coated image to a substrate.
The imaging step may be performed by any type of printing device, but desirably is performed by laser-color copier, laser-jet printer, or other toner-based printers or copiers. The transferring steps may be performed through application of heat and pressure to the image transfer materials. The application of heat and pressure may be, for example, performed by hand ironing or by using a heat press. Desirably, the first transferring steps are performed at a temperature below the melting point of the thermoplastic particles. However, the second transferring steps are desirably performed at a temperature above the melting point of the thermoplastic particles and/or the film-forming binder.
In accordance with one embodiment of the present invention, an image transfer material kit is disclosed that includes a first image transfer material that includes a substantially non-porous printable surface, and a second image transfer material that includes an outer layer including a film forming binder and thermoplastic particles. The first and second image transfer materials may be labeled so as to allow a user to distinguish therebetween. The kit may contain substantially equal numbers of the first and second image transfer materials, or the kit may contain more of the second image transfer material than the first image transfer material.
In one aspect, the first image transfer material may further include a base layer, and a release layer overlaying the base layer. The release layer may include, for example, a polymer having essentially no tack at transfer temperatures of about 177 degrees Celsius and/or a crosslinked polymer. Desirably, the release layer may include a polymer selected from the group consisting of acrylic polymers, poly(vinyl acetate), and so forth. The release layer may include an effective amount of a release-enhancing additive in the release layer. The release-enhancing additive may include, for example, a divalent metal ion salt of a fatty acid, a polyethylene glycol, a silicone surfactant, a mixture thereof, and so forth. More specifically, the release-enhancing additive may include, for example, calcium stearate, a polyethylene glycol having a molecular weight of from about 2,000 to about 100,000, a siloxane-polyether surfactant, a mixture thereof, and so forth.
In a further aspect, the second image transfer material may further include a base layer, and a release layer overlaying the base layer-and underlying the outer layer. The release layer may include, for example, a polymer having essentially no tack at transfer temperatures of about 177 degrees Celsius and/or a crosslinked polymer. Desirably, the release layer may include a polymer selected from the group consisting of acrylic polymers, poly(vinyl acetate), and so forth. In one embodiment, the release layer and the outer layer are adapted to provide the second image transfer material with cold release properties. Such cold-release properties may be imparted by using an effective amount of a release-enhancing additive in the release layer as described above for the first heat transfer material.
In yet another aspect, a method of using the kit is disclosed that includes the steps of:
a) imaging the substantially non-porous printable surface of one of the first image transfer material to form an imaged surface having a printed area and a non-printed area on the first image transfer material;
b) positioning the outer layer of one of the second image transfer material adjacent the imaged surface;
c) transferring a portion of the outer layer to the printed area of the imaged surface while transferring a lesser portion of the outer layer to the non-printed area to form a coated imaged surface having a non-printed area with less coating than the printed area; and
d) thereafter, transferring the coated image to a substrate.
In another aspect, a method of using the kit is disclosed that includes the steps of:
a) imaging the outer layer of the second image transfer material to form an imaged surface having a printed area and a non-printed area on the second image transfer material;
b) positioning the outer layer of the second image transfer material adjacent the substantially non-porous surface of the first image transfer material;
c) transferring the printed area and a first portion of the outer layer of the second image transfer material to the substantially non-porous surface of the first image transfer material to form a coated imaged surface on the first image transfer material having a non-printed area with less coating than the printed area; and
d) thereafter, transferring the coated image to a substrate.
In accordance with one embodiment of the present invention, a heat transfer intermediate includes a base sheet having a non-porous surface, an image including meltable toners adhered to a printed area of the non-porous surface, and a heat activated polymer coating overlaying the meltable toners, wherein the basis weight of the polymer coating overlaying the meltable toners is greater than the basis weight of the polymer coating overlaying an unprinted area of the non-porous surface. In one aspect, the base sheet includes a backing layer, a conformable layer overlaying the backing layer, and a release coating overlaying the conformable layer.
In accordance with another embodiment of the present invention, a decorated article includes a substrate and a decoration imprinted on the substrate. The decoration includes first and second areas, the first area including meltable toners and the second area being devoid of meltable toners. The decoration further includes a heat activated polymer layer, wherein a portion of the heat activated polymer layer is positioned between the meltable toners and the substrate, and further wherein the basis weight of the heat activated polymer layer under the first area is greater than the basis weight of the heat activated polymer layer under the second area.
Other features and aspects of the present invention are discussed in greater detail below.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, which makes reference to the appended figures in which:
a-3f are fragmentary sectional views depicting a method of transferring an image to a substrate using a release sheet transfer material and an transfer coating material in accordance with the present invention; and
Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention.
Reference will now be made in detail to embodiments of the invention, one or more examples of which are provided herein. Each example is provided by way of explanation of the invention and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment may be utilized with another embodiment to yield still a further embodiment. It is intended that the present invention include such modifications and variations as come within the scope of the appended claims and their equivalents.
As used herein, the term “printable” is meant to include enabling the placement of an image on a material by any means, such as by direct and offset gravure printers, silk-screening, typewriters, laser printers, laser copiers, other toner-based printers and copiers, dot-matrix printers, and ink jet printers, by way of illustration. Moreover, the image composition may be any of the inks or other compositions typically used in printing processes.
The term “molecular weight” generally refers to a weight-average molecular weight unless another meaning is clear from the context or the term does not refer to a polymer. It long has been understood and accepted that the unit for molecular weight is the atomic mass unit, sometimes referred to as the “dalton.” Consequently, units rarely are given in current literature. In keeping with that practice, therefore, no units are expressed herein for molecular weights.
As used herein, the term “cellulosic nonwoven web” is meant to include any web or sheet-like material which contains at least about 50 percent by weight of cellulosic fibers. In addition to cellulosic fibers, the web may contain other natural fibers, synthetic fibers, or mixtures thereof. Cellulosic nonwoven webs may be prepared by air laying or wet laying relatively short fibers to form a web or sheet. Thus, the term includes nonwoven webs prepared from a papermaking furnish. Such furnish may include only cellulose fibers or a mixture of cellulose fibers with other natural fibers and/or synthetic fibers. The furnish also may contain additives and other materials, such as fillers, e.g., clay and titanium dioxide, surfactants, antifoaming agents, and the like, as is well known in the papermaking art.
As used herein, the term “polymer” generally includes, but is not limited to, homopolymers; copolymers, such as, for example, block, graft, random and alternating copolymers; and terpolymers; and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configurations of the material. These configurations include, but are not limited to isotactic, syndiotactic, and random symmetries.
The term “thermoplastic polymer” is used herein to mean any polymer which softens and flows when heated; such a polymer may be heated and softened a number of times without suffering any basic alteration in characteristics, provided heating is below the decomposition temperature of the polymer. Examples of thermoplastic polymers include, by way of illustration only, end-capped polyacetals, such as poly(oxymethylene) or polyformaldehyde, poly(trichloroacetaldehyde), poly(n-valeraldehyde), poly(acetaldehyde), and poly(propionaldehyde); acrylic polymers, such as polyacrylamide, poly(acrylic acid), poly(methacrylic acid), poly(ethyl acrylate), and poly(methyl methacrylate); fluorocarbon polymers, such as poly(tetrafluoroethylene), perfluorinated ethylene-propylene copolymers, ethylene-tetrafluoroethylene copolymers, poly(chlorotrifluoroethylene), ethylene-chlorotrifluoroethylene copolymers, poly(vinylidene fluoride), and poly(vinyl fluoride); polyamides, such as poly(6-aminocaproic acid) or poly(e-caprolactam), poly(hexamethylene adipamide), poly(hexamethylene sebacamide), and poly(11-aminoundecanoic acid); polyaramides, such as poly(imino-1,3-phenyleneiminoisophthaloyl) or poly(m-phenylene isophthalamide); parylenes, such as poly-p-xylylene and poly(chloro-p-xylylene); polyaryl ethers, such as poly(oxy-2,6-dimethyl-1,4-phenylene) or poly(p-phenylene oxide); polyaryl sulfones, such as poly(oxy-1,4-phenylenesulfonyl-1,4-phenyleneoxy-1,4-phenylene-isopropylidene-1,4-phenylene) and poly(sulfonyl-1,4-phenyleneoxy-1,4-phenylenesulfonyl-4,4′-biphenylene); polycarbonates, such as poly(bisphenol A) or poly(carbonyidioxy-1,4-phenyleneisopropylidene-1,4-phenylene); polyesters, such as poly(ethylene terephthalate), poly(tetramethylene terephthalate), and poly-(cyclohexylene-1,4-dimethylene terephthalate) or poly(oxymethylene-1,4-cyclohexylenemethyleneoxyterephthaloyl); polyaryl sulfides, such as poly(p-phenylene sulfide) or poly(thio-1,4-phenylene); polyimides, such as poly(pyromellitimido-1,4-phenylene); polyolefins, such as polyethylene, polypropylene, poly(1-butene), poly(2-butene), poly(1-pentene), poly(2-pentene), poly(3-methyl-1-pentene), and poly(4-methyl-1-pentene); vinyl polymers, such as poly(vinyl acetate), poly(vinylidene chloride), and poly(vinyl chloride); diene polymers, such as 1,2-poly-1,3-butadiene, 1,4-poly-1,3-butadiene, polyisoprene, and polychloroprene; polystyrenes; copolymers of the foregoing, such as acrylonitrile-butadiene-styrene (ABS) copolymers; and the like.
The term “hard acrylic polymer” as used herein is intended to mean any acrylic polymer which typically has a glass transition temperature (Tg) of at least about 0 degrees Celsius. For example, the Tg may be at least about 25 degrees Celsius. As another example, the Tg may be in a range of from about 25 degrees Celsius to about 100 degrees Celsius. A hard acrylic polymer typically will be a polymer formed by the addition polymerization of a mixture of acrylate or methacrylate esters, or both. The ester portion of these monomers may be C1-C6 alkyl groups, such as, for example, methyl, ethyl, and butyl groups. Methyl esters typically impart “hard” properties, while other esters typically impart “soft” properties. The terms “hard” and “soft” are used qualitatively to refer to room-temperature hardness and low-temperature flexibility, respectively. Soft latex polymers generally have glass transition temperatures below about 0 degrees Celsius. These polymers flow too readily and tend to bond to the fabric when heat and pressure are used to effect transfer. Thus, the glass transition temperature correlates fairly well with polymer hardness.
As used herein, the term “cold release properties” means that once an image has been transferred to a substrate, such as cloth or another heat transfer paper, the backing or carrier sheet may be easily and cleanly removed from the substrate after the heat transfer material has cooled to ambient temperature. That is, after cooling, the backing or carrier sheet may be peeled away from the substrate to which an image has been transferred without resisting removal, leaving portions of the image on the carrier sheet, or causing imperfections in the transferred image coating.
The present invention relates to first and second matched heat transfer materials. The first heat transfer material is a release sheet material that includes a printable surface. The second heat transfer material is a transfer coat sheet material that includes an outer layer comprising a film forming binder and thermoplastic particles. The present invention also relates to a method of transferring images to substrates using the release sheet material and the transfer coat sheet material.
Release Sheet Material
In
The backing, or base, layer 11 of the release sheet material is flexible and has first and second surfaces. The backing layer typically will be a film or a cellulosic nonwoven web. In addition to flexibility, the backing layer also should have sufficient strength for handling, coating, sheeting, other operations associated with the manufacture of the release sheet material, and for transfer of the image to a substrate. The basis weight of the base layer generally may vary from about 30 to about 150 g/m2. By way of example, the backing, or base, layer may be a paper such as is commonly used in the manufacture of heat transfer papers. In some embodiments, the backing layer will be a latex-impregnated paper such as described, for example, in U.S. Pat. No. 5,798,179, the entirety of which is incorporated herein by reference. The backing layer is readily prepared by methods that are well known to those having ordinary skill in the art.
The release layer, or coating 13, overlays the first surface of the backing layer or the optional conformable layer. The release coating can be fabricated from a wide variety of materials well known in the art of making peelable labels, masking tapes, etc. For example, silicone polymers are very useful and well known. In addition, many types of lattices such as acrylics, polyvinylacetates, polystyrenes, polyvinyl alcohols, polyurethanes, polyvinychlorides, as well as many copolymer lattices such as ethylene-vinylacetate copolymers, acrylic copolymers, vinyl chloride-acrylics, vinylacetate acrylics, other hard acrylic polymers, and so forth, can be used.
In some cases, it may be helpful to add release agents to the release coatings such as soaps, detergents, silicones etc., as described in U.S. Pat. No. 5,798,179. The amounts of such release agents can then be adjusted to obtain the desired release. For example, the release enhancing additive may include a divalent metal ion salt of a fatty acid, a polyethylene glycol, a polysiloxane surfactant, or a mixture thereof. More particularly, the release-enhancing additive may include calcium stearate, a polyethylene glycol having a molecular weight of from about 2,000 to about 100,000, a siloxane polymer polyether, or a mixture thereof.
The thickness of the release coatings is not critical, and may vary considerably depending upon a number of factors including, but not limited to, the backing layer or conformable layer to be coated. Typically, the release coating layer has a thickness of less than about 2 mil (52 microns). More desirably, the release coating layer has a thickness of from about 0.1 mil to about 1.0 mil. Even more desirably, the release coating layer has a thickness of from about 0.2 mil to about 0.8 mil. The thickness of the release coating layer may also be described in terms of a basis weight. Desirably, the release coating layer has a basis weight of less than about 45 g/m2. More desirably, the release coating layer has a basis weight of from about 2 g/m2 to about 25 g/m2. Even more desirably, the release coating layer has a basis weight of from about 2 g/m2 to about 20 g/m2, and even more desirably from about 4 g/m2 to about 20 g/m2.
The release coating layer is desirably printable with an image that is to be permanently transferred to a substrate. The release coating layer desirably substantially prevents penetration of the image, dyes, pigments and/or toners into the underlying layer. In this regard, the release coating layer is desirably substantially non-porous.
In one embodiment, the release coating layer includes a crosslinked polymer. The cross-linked polymer may be formed from a crosslinkable polymeric binder and a crosslinking agent. The crosslinking agent reacts with the crosslinkable polymeric binder to form a 3-dimensional polymeric structure. Generally, it is contemplated that any pair of polymeric binder and crosslinking agent that reacts to form the 3-dimensional polymeric structure may be utilized. Crosslinkable polymeric binders that may be used are any that may be cross-linked to form a 3-dimensional polymeric structure. Desirable crosslinking binders include those that contain reactive carboxyl groups. Exemplary crosslinking binders that include carboxyl groups include acrylics, polyurethanes, ethylene-acrylic acid copolymers, and so forth. Other desirable crosslinking binders include those that contain reactive hydroxyl groups. Cross-linking agents that can be used to crosslink binders having carboxyl groups include polyfunctional aziridines, epoxy resins, carbodiimide, oxazoline functional polymers, and so forth. Cross-linking agents that can be used to crosslink binders having hydroxyl groups include melamine-formaldehyde, urea formaldehyde, amine-epichlorohydrin, multi-functional isocyanates, and so forth.
In another embodiment, the release coating layer may include a polymeric film forming binder and a particulate material. The film forming binder is applied to the base layer so as to form a film on the surface of the release sheet material. The particulate material may be, for example, clay particles, powdered thermoplastic polymers, diatomaceous earth particles, and so forth.
The release coat material layers that are based on a film-forming binder may be formed on a given underlying layer by known coating techniques, such as by roll, blade, Meyer rod, and air-knife coating procedures. The resulting image transfer material then may be dried by means of, for example, steam-heated drums, air impingement, radiant heating, or some combination thereof. Melt-extruded release coat layers may be applied with an extrusion coater that extrudes molten polymer through a screw into a slot die. The film exits the slot die and flows by gravity onto the base layer or conformable layer. The resulting coated material is passed through a nip to chill the extruded film and bond it to the underlying layer. For less viscous polymers, the molten polymer may not form a self-supporting film. In these cases, the material to be coated may be directed into contact with the slot die or by using rolls to transfer the molten polymer from a bath to the image transfer material.
If desired, the release coating layer may contain other additives, such as processing aids, release agents, pigments, deglossing agents, antifoam agents, surfactants, pH control agents such as ammonium hydroxide, rheology control agents and the like. The use of these and similar materials is well known to those having ordinary skill in the art.
Transfer Coat Sheet Material
Referring now to
In some embodiments, the transfer coat sheet material may have cold-release properties. Heat transfer materials having cold-release properties have been previously disclosed, for example, in U.S. Pat. No. 6,200,668, U.S. Pat. Nos. 5798,179, and 6,428,878, the contents of which are incorporated herein in their entirety. Other heat transfer materials having cold-release properties, for example, are disclosed in U.S. patent application Ser. No. 10/750,387, the entirety of which is incorporated herein by reference.
The backing, or base, layer 21 of the transfer coat sheet material 20 may be substantially as described above for the backing layer of the release sheet material. The backing layer of the transfer coat sheet material is flexible and has first and second surfaces. The flexible backing layer typically will be a film or a cellulosic nonwoven web. In addition to flexibility, the backing layer also should have sufficient strength for handling, coating, sheeting, other operations associated with the manufacture of the transfer coat sheet material, and for removal after transfer. By way of example, the backing layer may be a paper such as is commonly used in the manufacture of heat transfer papers. The backing layer is readily prepared by methods that are well known to those having ordinary skill in the art.
The optional release layer 22 of the transfer coat sheet material may be substantially as described above for the release layer of the release sheet material. The release layer of the transfer coat sheet material overlays the first surface of the backing layer. The basis weight of the release layer generally may vary from about 2 to about 30 g/m2. In one embodiment, the release layer has essentially no tack at transfer temperatures (e.g., 177 degrees Celsius). As used herein, the phrase “having essentially no tack at transfer temperatures” means that the release layer does not stick to the overlying transfer coating to an extent sufficient to adversely affect the quality of the transferred image. By way of illustration, the release layer may include a hard acrylic polymer or poly(vinyl acetate). As another example, the release layer may include a thermoplastic polymer having a Tg of at least about 25 degrees Celsius. As another example, the Tg may be in a range of from about 25 degrees Celsius to about 100 degrees Celsius. Suitable polymers include, for example, polyacrylates, styrene-butadiene copolymers, ethylene vinyl acetate copolymers, nitrile rubbers, poly(vinyl chloride), poly(vinyl acetate), ethylene-acrylate copolymers, and so forth, which have suitable glass transition temperatures.
In another embodiment, the optional release layer of the transfer coat sheet material may include a crosslinked polymer. The cross-linked polymer may be formed from a crosslinkable polymeric binder and a crosslinking agent. The crosslinking agent reacts with the crosslinkable polymeric binder to form a 3-dimensional polymeric structure. Generally, it is contemplated that any pair of the polymeric binders and crosslinking agents described above for the release layer of the release sheet material may be utilized in the release layer of the transfer coat sheet material.
The optional release layer also may include an effective amount of a release-enhancing additive. For example, the release enhancing additive may include a divalent metal ion salt of a fatty acid, a polyethylene glycol, a polysiloxane surfactant, or a mixture thereof. More particularly, the release-enhancing additive may include calcium stearate, a polyethylene glycol having a molecular weight of from about 2,000 to about 100,000, a siloxane polymer polyether, or a mixture thereof.
As mentioned above, the transfer coating overlays the base layer or the optional release layer. The basis weight of the transfer coating generally may vary from about 2 to about 70 g/m2. Desirably, the basis weight of the transfer coating may vary from about 20 to about 50 g/m2, more desirably from about 25 to about 45 g/m2, and even more desirably from about 25 to about 45 g/m2. The transfer coating includes one or more coats or layers of a film-forming binder and a powdered thermoplastic polymer over the base layer or optional release layer. The composition of the coats or layers may be the same or may different. Desirably, the transfer coating will include greater than about 10 percent by weight of the film-forming binder and less than about 90 percent by weight of the powdered thermoplastic polymer. In general, each of the film-forming binder and the powdered thermoplastic polymer will melt in a range of from about 65 degrees Celsius to about 180 degrees Celsius. For example, each of the film-forming binder and powdered thermoplastic polymer may melt in a range of from about 80 degrees Celsius to about 120 degrees Celsius.
In general, any film-forming binder may be employed which meets the criteria specified herein. As a practical matter, water-dispersible ethylene-acrylic acid copolymers have been found to be especially effective film-forming binders.
Similarly, the powdered thermoplastic polymer may be any thermoplastic polymer that meets the criteria set forth herein. For example, the powdered thermoplastic polymer may be a polyamide, polyester, ethylene-vinyl acetate copolymer, polyolefin, and so forth. In addition, the powdered thermoplastic polymer may consist of particles that are from about 2 to about 50 micrometers in diameter.
Manufacturers' published data regarding the melt behavior of film-forming binders or powdered thermoplastic polymers correlate with the melting requirements described herein. It should be noted, however, that either a true melting point or a softening point may be given, depending on the nature of the material. For example, materials such a polyolefins and waxes, being composed mainly of linear polymeric molecules, generally melt over a relatively narrow temperature range since they are somewhat crystalline below the melting point. Melting points, if not provided by the manufacturer, are readily determined by known methods such as differential scanning calorimetry. Many polymers, and especially copolymers, are amorphous because of branching in the polymer chains or the side-chain constituents. These materials begin to soften and flow more gradually as the temperature is increased. It is believed that the ring and ball softening point of such materials, as determined, for example, by ASTM Test Method E-28, is useful in predicting their behavior in the present invention. Moreover, the melting points or softening points described are better indicators of performance in this invention than the chemical nature of the polymer.
The layers applied to the transfer coat sheet material that are based on a film-forming binder may be formed on a given layer by known coating techniques, such as by roll, blade, Meyer rod, and air-knife coating procedures. The resulting image transfer material then may be dried by means of, for example, steam-heated drums, air impingement, radiant heating, or some combination thereof.
For decoration of dark fabrics, the transfer coating may further include an opacifier. The use of opaque layers in heat transfer materials for decoration of dark colored fabrics is described in U.S. patent application Ser. No. 10/003,697, filed Oct. 31, 2001. The opacifier is a particulate material that scatters light at its interfaces so that the transfer coating is relatively opaque. Desirably, the opacifier is white and has a particle size and density well suited for light scattering. Such opacifiers are well known to those skilled in the graphic arts, and include particles of minerals such as aluminum oxide and titanium dioxide or of polymers such as polystyrene. The amount of opacifier needed in each case will depend on the desired opacity, the efficiency of the opacifier, and the thickness of the transfer coating. For example, titanium dioxide at a level of approximately 20 percent in a film of one mil thickness provides adequate opacity for decoration of black fabric materials. Titanium dioxide is a very efficient opacifier and other types generally require a higher loading to achieve the same results.
As mentioned above, the transfer coat sheet material may further include a conformable layer overlaying the base layer and underlying the optional release layer, thereby being located between the base layer and the release layer. In general, the conformable layer may include an extrusion coated polymer that melts in a range of from about 65 degrees Celsius to about 180 degrees Celsius as described above for the release sheet material. As an example, the conformable layer may be an extrusion coating of ethylene vinyl acetate. Alternatively, the conformable layer may include a film-forming binder and/or a powdered thermoplastic polymer. The basis weight of the conformable layer generally may vary from about 5 to about 60 g/m2.
If desired, any of the foregoing film layers of the transfer coat material may contain other materials, such as processing aids, release agents, pigments, particulates such as kaolin clay or diatomaceous earth, deglossing agents, antifoam agents, pH control agents such as ammonium hydroxide, and so forth. The use of these and similar materials is well known to those having ordinary skill in the art.
Methods of Using the Matched Image Transfer Papers
It is envisioned that the image transfer papers of the present invention may be used in several different methods of applying printed images to fabrics or other substrate materials. Referring to
Referring to
Referring to
Referring to
In one embodiment, it is envisioned that a matched set of image transfer materials or papers such as described herein may be provided to enable the transfer of printed images to fabrics and other substrates. The matched transfer materials may be provided as a kit in which a supply of both the release sheet material and the transfer coat material may be present in the kit. The release sheet materials and/or the transfer coat materials may be labeled appropriately so as to allow a user to distinguish therebetween. The kit may contain an equal number of the transfer coat materials and the release sheet materials. Alternatively, the kit may contain more of the transfer coat materials than the release sheet materials because it is envisioned that it may be possible to reuse a single release sheet material for more than one image transfer.
The present invention may be better understood with reference to the examples that follow. Such examples, however, are not to be construed as limiting in any way either the spirit or scope of the present invention. In the examples, all parts are parts by weight unless stated otherwise.
Series of base substrates, release coating formulations, and powdered polymer coating formulations were produced for use in demonstrating the present invention. The base substrates are defined in Table 1. The release coating formulations are defined in Table 2. The powdered polymer coating formulations are defined in Table 3.
Table 4 summarizes the constructions of the release sheet materials that were produced using the base substrates of Table 1 and the release coatings of Table 2 to demonstrate the present invention.
Table 5 summarizes the constructions of the transfer coat sheet materials that were produced using the base substrates of Table 1, the release coatings of Table 2, and the powdered polymer coatings of Table 3 to demonstrate the present invention.
Image transfer experiments were performed using two transfer steps. Each experiment utilized a release sheet from Table 4 and a powdered polymer coated sheet from Table 5. The release sheet was imaged using a Canon 700 color Copier, unless noted otherwise. The first transfer step was carried out by heat pressing the imaged release sheet against the powdered polymer sheet in a heat press for the times and temperatures indicated. The powdered polymer coated sheet substrate was removed after cooling of the sheet materials. The second transfer step was done by heat pressing the release sheet (with the image and attached powdered polymer coating) against a 100% cotton Tee shirt material for 30 seconds at 350 degrees F., then removing the release sheet base substrate while the release sheet was still hot. Thereafter, the transferred images were evaluated according to how well the image was transferred, including how well the polymer coating was limited to the printed areas. Table 6 summarizes the cold peel/hot peel experiments with the Canon 700 color copier images.
As discussed above, in the cold peel/hot peel experiments, the step of removing the powdered polymer transfer base substrate was done after cooling of the sheet materials, and the step of removing the release sheet base substrate was done while the sheet material was still hot. Under these conditions, the release coating in the transfer coat sheet material with the powdered polymer coating functions as a true release coating. However, the release coating on the release sheet material acts more like a barrier layer, since the separation occurs within the melted toner. When this is the case, less than 100% of the toner may be transferred to the fabric. The actual amount which is transferred to the fabric depends on the structure of the release sheet. If the release sheet is plain paper, most of the toner stays on the paper. More of the toner transfers if there is a barrier layer on the release sheet, but still only about 50%. Results are much improved if the release sheet has a meltable conformable film layer under the release (barrier) coat since this allows the release sheet to conform to the fabric substrate. It has generally been seen that thinner or more conformable release coatings give better transfers in these designs. For example, release coatings including polyethylene oxides tend to perform better than those with large amounts of crosslinker (XAMA 7) or clay.
Some of the experiments resulted in small amounts of the powdered polymer coating transferring to the non-imaged areas of the release sheet in the first step. However, after the second transfer step, the background, or non-imaged areas of the fabric substrate did not appear significantly different than on those fabrics to which no polymer coating transferred in the non-printed areas.
Table 6 Comments:
A second set of experiments was performed, again using release sheets from Table 4 and powdered polymer coated sheets from Table 5. The release sheets were imaged using a Canon 700 color copier. The first transfer step was done by pressing the imaged release sheet against the powdered polymer sheet in a heat press for the indicated times and temperatures. The transfer coat sheet base substrate was removed while the sheet materials were still hot. The second transfer step was done by pressing the imaged release sheet with the attached powdered polymer coating to a 100% cotton Tee shirt material for 30 seconds at 350 degrees F. The release sheet base substrate was then removed while the sheet material was still hot. As such, the transfer steps can be classified as “hot peel/hot peel”. Thereafter, the transferred images were evaluated according to how well the image was transferred, including how well the polymer coating was limited to the printed areas. Table 7 summarizes the hot peel/hot peel experiments with the Canon 700 color copier images.
In the first transfer step, the separation occurs within one of the powdered polymer coating layers because the coating still at least partially molten. In the first transfer step, the binders are probably molten when the sheets are separated. It is advantageous to utilize a powdered polymer coating having a low melting point and/or a low melt viscosity binder in the powdered polymer coating since this will make separation easier. A two-layered powdered polymer coating with the first powdered polymer coating (the one closest to the base substrate) having the low melting point and/or low melt viscosity binder is especially desirable. The second transfer step for the experiments summarized in Table 7 is substantially as described above for Table 6.
Table 7 Comments:
A third set of experiments was performed, again using release sheets from Table 4 and powdered polymer coated sheets from Table 5. The release sheets were imaged using a Canon 700 color copier. The first transfer step was done by pressing the imaged release paper against the polymer coated sheet in a Tee shirt press for the indicated time and temperature, then removing the base substrate of the polymer coated sheet while the sheets were still hot. The second step was done by pressing the imaged release sheet with the attached powdered polymer against a 100% cotton Tee shirt material for 30 seconds at 350 degrees F. The sheets were allowed to cool prior to removing the base substrate from the release sheet material. As such, the transfer steps can be classified as “hot peel/cold peel”. Thereafter, the transferred images were evaluated according to how well the image was transferred, including how well the polymer coating was limited to the printed areas. Table 8 summarizes the hot peel/cold peel experiments with the Canon 700 color copier images.
As noted above, in the second transfer step the release paper was allowed to cool before the release sheet backing was removed. Desirably, the release coating acts as a true release coating and nearly 100% of the toner is transferred to the fabric. Generally, this method is capable of giving the most desirable results, but the combination of release sheet and polymer coated sheet must be such that, in the first transfer step, the powdered polymer coating transfers only to the imaged areas of the release sheet. Also, the toner must not transfer to the powdered polymer sheet in this step. Several of the combinations of release sheet and powdered polymer sheet formulations did satisfy these requirements. Interestingly, these same combinations failed when the sheets were allowed to cool after the first pressing (cold peel in the first step). When cold peeling in the first transfer step, the toner transferred to the powdered polymer sheet. This is apparently due to the toner adhesion being stronger at higher temperatures.
Release sheets with a meltable conformable polymer layer under the release coat resulted in much better transfers than similar release sheets without the meltable conformable polymer layer under the release coat. This is because the meltable polymer layers allow conformability to the fabric surface. Generally, thinner, more conformable release coatings result in more durable transfers. For example, release sheet RS21 transfers washed better than release sheet RS23 transfers. Plain paper with a release coat did give nearly 100% transfer of the toner to the fabric in one experiment, but the image was glossy and not penetrated well into the fabric. The transfer could be improved somewhat by pressing it with a thin, silicone treated release paper.
Some of the hot peel/cold peel experiments resulted in small amounts of the powdered polymer coating transferring to the non-imaged areas of the release sheet in the first step. However, after the second transfer step, the background, or non-imaged areas of the fabric substrate did not appear significantly different than on those fabrics to which no polymer coating transferred in the non-printed areas.
Table 8 Comments:
A fourth set of experiments was performed, again using release sheets from Table 4 and powdered polymer coated sheets from Table 5. The release sheets were imaged using a Hewlett Packard 4600 color printer. The first transfer step was done by pressing the imaged release sheet against the polymer coated transfer sheet in a heat press for the indicated time and temperature. Thereafter, the transfer sheet back was removed while the sheets were still hot. The second transfer step was done by pressing the imaged release sheet with the attached powdered polymer coating against a 100% cotton Tee shirt material in a heat press for 30 seconds at 350 degrees F. The release sheet backing was removed after cooling of the release sheet material. As such, the transfer steps can be classified as “hot peel/cold peel”. Thereafter, the transferred images were evaluated according to how well the image was transferred, including how well the polymer coating was limited to the printed areas. Some of the hot peel/cold peel experiments resulted in successful transfers. However, the washability of the transferred images did not compare favorably with those imaged with the Canon 700 color copier. Using a hot peel transfer for the second transfer step resulted in insufficient transfer of the toner from the release sheet, even using designs which were successful with the Canon 700 color copier images. Table 9 summarizes the hot peel/cold peel experiments with Hewlett Packard 4600 color printer images.
Table 9 Comments:
All wash tests were done using Tide detergent in a commercial washing machine (Unimat model 18 available from Unimat Corporation) at a medium soil setting. Drying was done in an heavy duty, large capacity, electric Kenmore drier.
It should be appreciated by those skilled in the art that various modifications or variations can be made in the invention without departing from the scope and spirit of the invention. It is intended that the invention include such modifications and variations as come within the scope of the appended claims and their equivalents.
