[0001] The present invention relates generally to methods for processing substrates printed
with an ink layer having a non-planar surface topography and composite laminates produced
thereby. Preferred embodiments of the invention relate more specifically to methods
for processing light transmissive substrates printed with a phase change ink layer
to produce a composite laminate that provides improved color images by overhead projection.
[0002] Ink jet printers operate by ejecting ink onto a print substrate, such as paper, in
controlled patterns of dots. By selectively regulating the pattern of ink droplets,
such ink jet printers can be used to produce a wide variety of printed images, including
text, graphics, and the like. Moreover, ink jet printers are capable of recording
permanent images on a wide variety of substrates, including both light reflective
and light transmissive substrates.
[0003] Ink jet printers utilize a variety of inks, including phase change inks, which are
often referred to as hot melt inks. In general, phase change inks are solid at ambient
temperatures and liquid at the elevated operating temperatures of an ink jet printing
device. Liquid phase ink droplets are ejected from the printing device at an elevated
operating temperature and, when the ink droplets contact the surface of a substrate,
they quickly solidify.
[0004] Early references to phase change inks for ink jet printing involved monochrome inks
jetted by electrostatic printing devices. Thus, for example, U.S. Patent No. 3,653,932
discloses a low melting point (30°C to 50°C) ink having a base comprising diesters
of sebacic acid. In a similar process, U.S. Patent No. 3,715,219 describes low melting
point (30°C to 60°C) inks including a paraffin alcohol-based ink. One disadvantage
of printing with low melting point phase change inks is that they frequently exhibit
offset problems. Specifically, when substrates printed with these inks are stacked
and stored for subsequent use, the ink adheres to adjacent surfaces, particularly
if the printed substrates are exposed to high ambient temperatures.
[0005] Phase change inks are well known in the art. U.S. Patent Nos. 4,390,369 and 4,484,948
describe methods for producing monochrome phase change inks that employ a natural
wax ink base, such as Japan wax, candelilla wax, and carnauba wax, which are subsequently
printed from a drop-on-demand ink jet device at a temperature ranging between 65°C
and 75°C. U.S. Patent No. 4,659,383 discloses a monochrome ink composition having
an ink base including a C20-24 acid or alcohol, a ketone, and an acrylic resin plasticizer.
These monochrome ink compositions are not durable and, when printed, may become smudged
upon routine handling and folding.
[0006] Japanese Patent Application No. 1,280,578 discloses the use of aliphatic and aromatic
amides that are solid at room temperature, such as acetamide, as printing inks. U.S.
Patent No. 4,684,956 is directed to monochrome phase change inks utilizing synthetic
microcrystalline wax (hydrocarbon wax) and Microcrystalline polyethylene wax. This
molten composition can be applied to a variety of porous and non-porous substrates
using drop-on-demand ink jet application techniques.
[0007] European Patent Application Nos. 0 287 352 and 0 206 286 disclose phase change ink
jet printing in color. The ink bases for these systems include fatty acids, a thermoplastic
polyethylene and a phase change material in the first application; and the alcohol
portion of a thermosetting resin pair, a mixture of organic solvents (o- and p-toluene
sulfonamide) and a dye in the second application.
[0008] A system for applying phase change inks, described in U.S. Patent No. 4,751,528,
relates to an ink jet apparatus for controlled solidification of phase change inks
to assist in controlled penetration of the substrate. This apparatus includes a substrate-supporting,
thermally conductive platen as well as a heater and a thermoelectric cooling arrangement,
both disposed in heat communication with the platen.
[0009] Several prior art references disclose manipulation of printed images formed from
phase change inks, either during or following the printing process. In U.S. Patent
No. 4,745,420, droplets of a phase change ink are ejected onto a target and subsequently
spread by the application of pressure to increase the ink surface area coverage and
minimize the volume of ink required. In other words, droplets of phase change ink
that may not initially cover the entire target are spread over the entire target surface
by application of pressure.
[0010] In xerographic image fusing, the area of contact between the toner and the substrate
may be substantially increased by causing the toner to spread and penetrate somewhat
into the underlying substrate. See Williams, "The Physics and Technology of Xerographic
Processes," J. Wiley & Sons (1984). The mechanical properties of the toner are such
that plastic deformation and flow occur during fusing. In both of the aforementioned
references, the ink or toner spreads across the paper, forming characters or patterns
thereon.
[0011] Although several references describe fusing of images between a pair of mechanically
loaded rollers at ambient temperatures, hot roll fusing has seen widespread use in
toner applications. In hot roll fusing, two rolls (typically one is heated) are mechanically
loaded together and rotated to provide transient application of heat and pressure
to the substrate. The toner is typically heated to above its glass transition temperature
(T
g), which enables it to coalesce, flow, and penetrate the substrate. Rolling pressure
and capillary action facilitate coverage. See Dr. John W. Trainer, "Trends and Advances
in Dry Toner Fusing," Institute for Graphic Communication (June 1985).
[0012] Ink jet printing of colored inks onto light transmissive media for displaying color
images by overhead projection has historically been a problem. When aqueous inks are
employed, for example, special coatings must be provided on the light-transmissive
medium to absorb the solvent so that images of high quality are formed. See U.S. Patent
Nos. 4,503,111, 4,547,405 and 4,555,437.
[0013] The development of phase change inks that are substantially transparent provides
improved capability to print images on many types of substrates. Phase change ink
compositions disclosed in U.S. Patent No. 4,889,761 are exemplary. Special coatings
are not required for phase change ink jet printing on transparencies. Images produced
by prior art color phase change inks printed on light transmissive substrates, however,
are not generally acceptable for use in overhead projection systems as a consequence
of color ink jet printing techniques.
[0014] U.S. Patent Nos. 4,889,761, 4,801,473 and 4,853,706 describe problems associated
with projection of images from light transmissive substrates (
e.g., transparencies) printed with phase change inks. Projection problems result because
ink deposited on substrates by an ink jet printer solidifies as curved droplets that
refract and scatter impinging light, notwithstanding the substantial transparency
of the phase change ink material. Impinging light is transmitted through printed ink
droplets in a non-rectilinear path, and the refracted light is directed away from
the collection lens of a projection system. Consequently, the projected image is visible
primarily in contrast, and the colors of the projected image have a dull grayish cast.
This problem is exacerbated by printing techniques wherein multiple layers of ink
droplets are applied to produce secondary colors.
[0015] U.S. Patent No. 4,801,473 is directed to a method of processing transparencies printed
with curved, light scattering ink droplets. Printed ink droplets are overlaid with
a transparent layer having an index of refraction substantially the same as the index
of refraction of the ink droplets. Preferred coating materials include transparent
polyurethane and acrylic. The ′473 publication teaches that the exterior surface of
the coating layer need not be parallel to the substrate surface to achieve an improvement
in projection.
[0016] Application of a liquid coating to a printed substrate is impractical in several
respects. Liquid coating application techniques are generally difficult to control.
Moreover, drying periods are frequently required to permit evaporation of solvents.
This technique moreover only provides some improvement because, although processing
reduces the radius of curvature of individual ink spots, the coating itself is curved
and refraction of transmitted light, although less severe, remains problematic.
[0017] U.S. Patent No. 4,853,706 discloses methods for processing transparencies having
curved, light scatting ink droplets thereon. The printed substrate is exposed to heat
and/or pressure to flatten the curved ink droplets. This processing requires a time
interval of about 30 seconds to 5 minutes, and may be achieved by bringing the transparency
into close thermocoupling or contact with a heater to remelt the ink. Coating the
printed substrate with a transparent coating to minimize the amount of light reflected
and refracted by the curved ink droplets scattered from the air/ink interface is also
disclosed.
[0018] Additionally, the ′706 patent teaches that ink droplets may be spread and flattened
by application of a second substantially transparent resinous support utilizing a
hot melt adhesive in a lamination process. After the adhesive-covered support sheet
is applied to cover the printed transparency, both the adhesive and the printed image
pattern are heated to melting temperatures, and the ink droplets are thereby flattened.
[0019] U.S. Patent No. 4,889,761 discloses substrates having a light-transmissive phase
change ink printed thereon that are processed to improve the quality of images projected
by overhead projection techniques. Printed substrates are processed to reorient the
surface configuration of solidified phase change ink droplets to provide a printed
ink layer having a generally uniform thickness that is capable of transmitting light
in a substantially rectilinear path. Reorientation is achieved by the application
of pressure or a combination of heat and pressure to the printed substrate by means
of a dual roller assembly. Rollers having various constructions are disclosed, including
a TEFLON® coated heated roller and silicone rubber covered pressure roller.
[0020] Reorientation of printed phase change ink layers has many practical limitations.
It typically requires application of relatively high pressures and/or the use of elevated
temperatures. Moreover, even under optimal conditions, it is difficult to achieve
sufficient reorientation of ink droplets in areas of transition from one ink layer
thickness to another.
[0021] Prior art techniques for processing and/or reorienting phase change ink droplets
printed on light transmissive substrates such as transparencies generally have not
provided optimal results. Offset problems and problems resulting from the non-uniform
distribution of ink droplets persist, especially where multiple ink droplet layers
are utilized in color printing techniques. Moreover, most existing processing cycles
require complex, bulky equipment and/or unacceptable time periods for completion and
thus are not commercially viable alternatives.
[0022] The present invention provides methods for processing substrates printed with an
ink layer having a non-planar surface topography,
e.g., curved ink droplets, to produce a composite laminate. The composite laminate comprises
a printed substrate laminated to a substantially optically transparent film with an
adhesive layer interposed between the printed substrate and the film. The methods
of the present invention are especially suitable for processing light transmissive
substrates, such as transparencies, having phase change inks printed thereon to produce
a composite laminate that projects a clear, color saturated image upon projection
by overhead projection techniques.
[0023] The adhesive layer interposed between the printed substrate and the transparent film
is substantially optically clear and has an index of refraction substantially matching
that of the printed ink. The thickness of the intermediate adhesive layer is preferably
at least about as great as the maximum thickness of the printed image. Suitable adhesive
materials include hot-melt adhesives, pressure sensitive adhesives, and the like.
When hot-melt adhesives are employed, the softening point of the material is preferably
lower than the melting point of the printed ink.
[0024] Application of the substantially transparent film and intermediate adhesive layer
to the printed substrate may involve application of a combination of heat and pressure
using planar surfaces, rollers, or a combination thereof, to produce a composite laminate.
The processing apparatus, or a portion of the processing apparatus that contacts the
transparent film, is preferably heatable to a temperature at which the adhesive softens
and flows. During processing, the intermediate adhesive layer is heated to a temperature
at which it flows to intimately contact and conform to the topography of the printed
ink layer. The adhesive layer bonds to the ink layer, the substrate in regions that
are unprinted, and to the transparent film, to provide a durable composite laminate.
Additionally during processing, air trapped between the layers is expelled to produce
a composite laminate that is substantially free from visible bubbles.
[0025] According to preferred embodiments, the surface contacting the printed substrate
during lamination is at a lower temperature than the heated surface contacting the
transparent film. It is unnecessary and, for many applications, undesirable to heat
the printed ink layer to melting temperatures during the lamination process. Methods
of the present invention contemplate manipulation and reorientation of the adhesive
layer, rather than the printed ink layer, to provide a composite printed ink/adhesive
layer of uniform thickness bonded between the substrate and the transparent film.
[0026] The composite laminate produced according to methods of the present invention demonstrates
substantially improved projection by overhead projection techniques. As a result of
the lamination process, the composite laminate is generally planar. This feature facilitates
transmission of impinging light through the composite laminate in a substantially
rectilinear fashion and results in improved image clarity and color saturation during
overhead projection. As used herein with reference to composite laminates, the term
"planar" means that the surfaces of the substrate and the transparent film are substantially
parallel to one another in areas having similar image densities. Because the image
density,
i.e., the volume of printed ink per unit surface area may vary over the surface of the
printed substrate, there may be transitional regions where the substrate and the transparent
film are not perfectly parallel. Such transitional regions do not deviate substantially
from a parallel orientation and generally do not affect the quality of the composite
laminate.
[0027] The composite laminate of the present invention provides numerous practical advantages.
Composite laminates comprising a light transmissive substrate exhibit a high degree
of lightness and chroma and transmit light in a substantially rectilinear path. Offset
and abrasion problems are eliminated because the printed ink layer is protected from
exposure. Moreover, the laminated composite transparencies exhibit improved durability
for extended storage periods. Additionally, the composite laminate can be temporarily
or permanently marked with inks or the like. Frames, borders, logos, and the like
may be provided on the transparent film and incorporated in the composite laminate
product.
[0028] The lamination methods of the present invention are preferably incorporated in a
post-printing processing step utilized in conjunction with an ink jet printing device,
such as a drop-on-demand ink jet printer. Lamination processing may be utilized as
a stand alone process, or it may be utilized in conjunction with other post-processing
techniques, such as reorientation of the printed image. According to preferred embodiments,
printed substrates may undergo a pressure reorientation step prior to lamination processing.
[0029] The foregoing and other objects, features and advantages of the present invention
will be more readily apparent from the following detailed description of preferred
embodiments which proceeds with reference to the drawings.
[0030] Fig. 1 is a schematic representation illustrating the laminated composite product
of the present invention.
[0031] Fig. 2 is an exploded side view schematic representation of a dual roller processing
apparatus according to the present invention.
[0032] Fig. 3 is a side view schematic representation of a lamination processing kit according
to the present invention.
[0033] Fig. 4 is a side view schematic representation of another arrangement employing a
platen and a roller for laminating printed substrates.
[0034] Fig. 5 is an exploded side view schematic representation of a dual platen lamination
apparatus according to the present invention with a printed substrate and transparent
film/adhesive sheet positioned therein for lamination.
[0035] Phase change inks useful in accordance with the present invention are solid at ambient
temperatures and liquid at printing temperatures. Phase change inks preferably exhibit
low viscosity in the liquid phase and transparency and durability in the solid phase.
Phase change inks disclosed, for example, in U.S. Patent No. 4,889,761, which is incorporated
herein by reference in its entirety, are suitable.
[0036] Suitable printing substrates may be permeable, such as paper and the like, or substantially
impermeable, such as light reflective films, or light transmissive films, such as
transparencies and the like. Lamination processing according to the present invention
may advantageously be utilized with permeable, generally light reflective substrates
to improve the durability of the printed substrate. Lamination processing according
to the present invention, however, is especially suitable for utilization in connection
with light transmissive substrates, such as transparencies.
[0037] The term "lamination processing," as used herein, refers to the application and bonding
of a substantially optically clear protective film on a printed ink layer to provide
a composite laminate. More specifically, lamination processing according to the present
invention involves application of an intermediate adhesive layer and a protective
film layer on a printed ink layer whereby the printed ink layer and the adhesive layer
form a composite intermediate layer that has substantially parallel planar faces.
The surfaces of the substrate and the protective film consequently are substantially
planar and parallel.
[0038] Prior art transparency lamination techniques, as exemplified by the disclosure of
U.S. Patent No. 4,853,706, have utilized application of heat during or after lamination
to spread and flatten the curved ink droplets. Heat is applied, for example, by bringing
the transparency into close thermocoupling or contact with a heater to remelt the
ink. Remelting of the printed ink layer generally results in a lower definition image
and may result in smears or runs in the printed image. It is not necessary to remelt
the printed ink droplets or layer utilizing the lamination techniques of the present
invention. In fact, preferred lamination processing techniques of the present invention
are designed to prevent remelting of the printed ink layer.
[0039] A highly schematic diagram illustrating a composite laminate in accordance with the
present invention is illustrated in Fig. 1. Composite laminate 10 comprises a print
substrate 12, a printed ink layer comprising a plurality of generally curved ink droplets
14 deposited on substrate 12, an adhesive layer 16, and a protective film 18, which
forms a second exterior face of the composite laminate. During lamination processing,
adhesive layer 16 conforms to the surface topography of ink droplets 14 and intimately
contacts and bonds to substrate 12, ink droplets 14 and protective film 18. The thickness
of composite layer (A) formed by ink droplets 14 and adhesive layer 16 is preferably
substantially uniform, as shown, and the composite laminate is substantially free
of trapped air bubbles. As a consequence, the outer faces 20 and 22 of substrate 12
and protective film 18, respectively, are planar and are oriented substantially parallel
to one another.
[0040] When substrate 12 comprises a light transmissive material, such as a transparency,
and the composite laminate is intended for use in applications such as overhead projection,
substrate 12, ink droplets 14, and adhesive layer 16 comprise materials that are substantially
optically transparent and have substantially similar indices of refraction. The term
"substantially optically transparent," as used herein, means a material having a transmittance
of about 80% or greater in the visible light range. The term "substantially similar,"
as used herein with reference to indices of refraction (n), means that the difference
between the index of refraction of the adhesive material and that of the substrate
and the printed ink, respectively, is not more than about 10% to 12%. Composite laminate
10 has a generally uniform thickness, and the outer faces 20 and 22 formed by substrate
12 and protective film 18, respectively, are planar. Incident light, such as from
a projection source located beneath substrate 12, is therefore transmitted in a substantially
rectilinear path through composite laminate 10.
[0041] Substrate 12 may comprise a light reflective, somewhat permeable material such as
paper. Lamination processing according to the present invention is especially beneficial,
however, when substrate 12 comprises a light transmissive material, such as a transparency.
Many light transmissive substrates are known in the art and would be suitable. Substrates
comprising materials such as polyester (
e.g. MYLAR), cellulose triacetate, polystyrene, polycarbonate, and the like are suitable.
[0042] Hot melt adhesives, waxy materials, pressure sensitive adhesives, and the like that
are substantially optically clear are generally suitable adhesive materials for use
in composite laminates of the present invention. Hot melt adhesives are generally
preferred. Hot melt adhesives include materials that are generally solid and do not
exhibit adhesive properties at ambient temperatures but, at elevated temperatures,
become viscous fluids and conform and bond, upon cooling, to contact surfaces.
[0043] Numerous hot melt adhesive materials are known in the art for adhering fabrics, paper,
cardboard, and the like, but most would not be suitable for use in the present invention.
Hot melt adhesives that soften and flow at temperatures below the melting point of
printed inks are required, so that the heated adhesive softens, flows, and becomes
a viscous liquid at temperatures where the printed ink remains solid. Hot melt adhesives
having a softening point about 10° to 20°C below the melting point of the printed
ink are especially preferred.
[0044] Adhesive materials having a viscosity of about 10 to 30,000 centipoise (cp) at 140°C
are preferred, and adhesive materials having a viscosity of about 5,000 to 10,000
cp at 140°C are especially preferred. As the adhesive material is heated during lamination
processing, it conforms to the non-planar surface topography of the printed ink layer.
The printed ink layer preferably does not undergo melting or reorientation to a substantial
degree during lamination processing.
[0045] Preferred hot melt adhesive substances according to the present invention comprise
substantially optically clear polymeric hot melt adhesives that exhibit relatively
low melt viscosity. Adhesive formulations comprising from about 25% to about 80% of
a substantially optically clear base polymer and from about 20% to 75% of various
additives, such as tackifiers, waxes, and antioxidants are suitable. Copolymers marketed
by Dupont as "ELVAX" resins are particularly suitable base polymers for this application,
particularly those having a relatively low molecular weight (or high melt index).
A hot melt adhesive formulation consisting of 60% ELVAX 205W, 30% of an Arakawa Chemical
Co. KE-311 resin as a tackifier, and 10% Witco M-445 microcrystalline wax is especially
preferred for use in the methods and composite laminates of the present invention.
The formulation may also contain small amounts of an antioxidant such as Irganox 1010
(Ciba-Geigy), or the like, to facilitate stability during the coating process. This
formulation is designed to exhibit substantially lower melt viscosity compared to
typical hot melt adhesive formulations, while still providing good adhesive strength
and flexibility in the composite lamination, and retaining optical clarity.
[0046] Alternatively, the adhesive layer may comprise a wary material or a pressure sensitive
adhesive material. Materials having substantial optical clarity and compositions similar
to that of phase change inks are suitable, although waxy materials that soften and
flow at a temperature below the melting point of the printed ink layer are preferred.
Materials such as Witco Kenamide EX-774 are suitable.
[0047] Pressure sensitive adhesive materials typically exhibit bonding properties at ambient
temperatures and do not require application of elevated temperatures during processing
according to the present invention. Numerous pressure sensitive adhesive substances
that exhibit substantial optical clarity and conform and bond to materials having
a non-planar surface topography are known in the art and would be suitable. Adhesive-backed
transparent films available, for example, from Adhesive Research, Inc., Glen Rock,
PA, and marketed as ARCLAD, are suitable.
[0048] Substantially transparent films suitable for use as the protective layer are also
well known in the art. Flexible, polymeric sheet materials such as polyester,
e.g. MYLAR, and the like are well known in the art and would be suitable. The protective
film may comprise the same material as a light transmissive substrate. According to
preferred embodiments, protective film 18 has a thickness (B) less than thickness
(C) of substrate 12, suitably from about 10% to about 80% the thickness of the substrate,
and most preferably from about 30% to about 70% the thickness of the substrate. According
to especially preferred embodiments, substrate 12 has a thickness of about 100 microns
and protective film 18 has a thickness of 50 microns.
[0049] The adhesive layer may be applied independently from the protective film, but the
protective film and adhesive layer are preferably provided as a unitary sheet for
lamination to the printed substrate. This may be accomplished, for example, by heating
a hot melt adhesive substance to flow temperatures and applying a uniform thickness
hot melt adhesive coating on one surface of the protective film. Additionally, a release
layer may be provided between the hot melt adhesive and the protective film so that
the protective film is removable after application of the adhesive layer to the printed
substrate.
[0050] According to preferred embodiments, the thickness of the adhesive coating corresponds
generally to at least about 50% of the maximum thickness of the printed ink layer.
Thus, for example, as illustrated in Fig. 1, the maximum thickness of the printed
ink layer is (D), and the adhesive layer coating on transparency film 18 preferably
has a thickness of at least about 50% (D). Adhesive coating layers having a thickness
of at least about 100% (D) are especially preferred. An adhesive layer having a thickness
of about 25 to 100 microns and most preferably about 70 microns is preferred, for
example, for use with printed ink layers having a thickness of about 66 microns.
[0051] Lamination processing of the printed substrate is accomplished by application of
heat and/or pressure sufficient to provide intimate contact and bonding of the intermediate
adhesive layer to printed ink droplets and the substrate. Suitable contact pressures
and/or temperatures vary depending upon the properties of the adhesive material and
the configuration of the lamination apparatus.
[0052] When hot melt adhesives are employed, lamination processing preferably involves application
of both heat and pressure. Exemplary lamination processing apparatus are shown schematically
in Figs. 2-4. Fig. 2 illustrates a dual roller processing apparatus including a first
roller 26 and a second roller 28 aligned on substantially parallel longitudinal axes.
Roller diameters of about 1.25 to 5 cm are preferred, and rollers having a diameter
of about 2.5 cm are especially preferred.
[0053] Rollers 26 and 28 are preferably constructed from a rigid material and one or both
rollers may be provided with a resilient support means 30 in the form of an outer
resilient layer. Resilient support means 30 preferably comprises an elastomeric material
such as silicone rubber having a Durometer of about 40 Shore A and a thickness of
at least about 2 mm.
[0054] Rollers 26 and 28 are positioned to apply pressure to the printed substrate, the
intermediate adhesive layer and the protective film at the roller interface upon rotation
of the rollers in opposite directions. Processing pressures of about 70 to about 700
kpascals, and most preferably about 140 to about 420 kpascals, are generally utilized
when conventional hot melt polymeric adhesives and waxes are employed as the adhesive
layer. Processing pressures of about 250 to about 700 kpascals are generally suitable
for pressure sensitive adhesive materials. Processing rates (the rate at which the
printed substrate is passed between the rollers) of about .25 to about 2.5 cm/sec
are generally suitable, and processing rates of about 0.6 to about 1.25 cm/sec are
preferred.
[0055] Processing of laminated composite products incorporating hot melt adhesive materials
involves application of heat in addition to pressure. Roller apparatus for lamination
processing are preferably heatable to temperatures at which the adhesive substance
flows and bonds. In the embodiment shown in Fig. 2, roller 26 contacting protective
film 18 having adhesive layer 16 bonded thereto is preferably heatable. Temperatures
of about 100° to about 145°C are preferred for use with preferred adhesive and ink
compositions disclosed herein. Roller 28 contacting the printed substrate is preferably
not actively heated and, according to preferred embodiments, is therefore maintained
at a temperature not greater than that of heatable roller 26.
[0056] A thermal insulating layer may also be provided to thermally isolate the printed
substrate from roller 28. This thermal insulating layer facilitates lamination processing
by effectively ensuring that the majority of the thermal energy from roller 26 is
transferred to the adhesive layer and other composite laminate constituents. Suitable
thermal insulating layers include sheet materials having dimensions corresponding
generally to or slightly larger than the dimensions of the printed substrate. The
thermal insulating layer comprises a flexible sheet material having a relatively low
thermal conductivity. Preferred materials include heavy papers such as tag board,
or the like, having a thickness of about 200 to about 300 microns.
[0057] The thermal insulating layer is fed into the lamination apparatus between non-heated
roller 28 and the printed substrate and serves to isolate the printed substrate from
thermal energy stored in non-heated roller 28. Utilization of a thermal insulating
layer during lamination processing also renders the lamination process less sensitive
to temperature variations of roller 28. It may therefore be unnecessary to monitor
or control the temperature of roller 28 during lamination processing using a thermal
insulating layer.
[0058] A lamination processing kit including a thermal insulating layer 30 and an adhesive
layer 16 may also be provided, as shown in Fig. 3. The printed substrate is positioned
between the thermal insulating layer and the adhesive layer, with the printed ink
layer positioned adjacent the adhesive layer. The lamination processing kit, with
the printed substrate positioned therein, may then be processed by application of
heat and pressure. In lamination processing assemblies of this type, the adhesive
layer is preferably provided as a coating on transparent film 18 and the adhesive
layer and transparent film are simultaneously applied to the printed substrate.
[0059] Additionally, the lamination processing assembly may include a cover sheet 32 comprising
a flexible sheet material having a relatively low thermal resistance positioned adjacent
the transparent film. Preferred cover sheet materials include Vellum, or the like,
that readily conduct heat from heated roller 26 to the transparent film and adhesive
layer. The cover sheet preferably has a thickness less than that of the thermal insulating
layer. Thicknesses of about 10 to about 100 microns are suitable, and thicknesses
of about 50 to 75 microns are preferred. Multiple sheets comprising the lamination
processing kit may be joined along one edge, such as at edge 31, to facilitate accurate
alignment of the various sheets and the printed substrate. Lamination processing kits
of this type may be provided as single use assemblies that facilitate convenient handling
and improve thermal energy management during lamination processing.
[0060] Fig. 4 illustrates another processing apparatus according to the present invention
comprising a pressure application roller assembly 34 and a stationary platen 36. A
resilient support means 38 may be mounted on a substrate contact face of platen 36
and/or provided as an outer surface layer on roller assembly 34. Roller 34 is preferably
constructed from a rigid material such as stainless steel, or the like. Rollers having
a diameter of about 2.5 cm are preferred. Platen 36 preferably has dimensions that
are slightly larger than those of printed substrates to be processed. Platen 36 and/or
roller 34 may be heated during processing to a temperature that melts the adhesive
layer.
[0061] A printed substrate and an adhesive coated protective film are positioned between
platen 62 and roller 34 for processing. The adhesive layer is preferably positioned
adjacent the heated surface during lamination processing. The surface adjacent to
the printed substrate may be thermally isolated from the heated surface to prevent
melting of the printed ink layer. During processing, roller 34 traverses the upper
surface of platen 36 along a path substantially parallel to the contact surface of
resilient support means 38 and preferably exerts a pressure of about 70 to about 700
kpascals on the composite laminate components.
[0062] A dual platen processing apparatus having composite laminate components positioned
therein for processing is illustrated in Fig. 5. The processing apparatus comprises
a first platen 42 and a second platen 44 mounted for movement relative to one another
between a substrate insertion position, wherein the first and second platens are in
a spaced apart relationship, and a pressure application position, wherein the platens
apply a substantially uniform pressure over the surface area of a printed substrate
12. A dual platen processing apparatus of this type may be utilized in a variety of
orientations, provided that the first and second platens are positioned so that their
contact surfaces 43 and 45, respectively, are substantially parallel to one another
in the pressure application position. Resilient support means having dimensions at
least co-extensive with those of substrate 12 is preferably positioned on one or both
of the platen contact surfaces.
[0063] Where the adhesive layer comprises a hot melt adhesive, one or both of platens 42
and 44 are heated to preferred processing temperatures that cause the hot melt adhesive
to flow and bond. Preferred processing temperatures are preferably below the melting
point of the printed ink layer. It is preferred that the platen contacting protective
film 18, shown as platen 42 and Fig. 4, is heated to suitable processing temperatures,
while platen 44 contacting printed substrate 12 is not actively heated. In the embodiment
shown, platen 44 contacting printed substrate 12 preferably is not substantially passively
heated as a result of its proximity to heated platen 42.
[0064] Pressure may be applied to platens 42 and/or 44 in any convenient manner. For example,
platens 42 and 44 may be incorporated in a conventional platen press design, wherein
a manual or automatic actuator applies force to at least one of the platens to exert
pressure in a direction substantially perpendicular to the contact surface during
lamination processing. Substantially uniform pressure is applied simultaneously to
the entire surface area of the composite laminate components by means of the dual
platen apparatus. Processing times using a dual platen apparatus are reasonably short
as a result of the large contact area.
[0065] The composite laminate produced according to methods of the present invention exhibits
numerous practical advantages. It is not subject to offset or abrasion problems because
the printed ink layer is protected. Laminated composite transparencies are more durable
over extended storage periods. Additionally, the laminated composite product can be
temporarily or permanently marked with inks or the like, and borders, logos, and the
like may be provided on the transparent film and incorporated in the laminated composite
product.
[0066] While in the foregoing specifications, this invention has been described in relation
to certain preferred embodiments thereof, and many details have been set forth for
purposes of illustration, it will be apparent to those skilled in the art that the
invention is susceptible to additional embodiments and that certain of the details
described herein may be varied considerably without departing from the basic principles
of the invention.
1. Verfahren zum Behandeln von Substraten (12), die mit einer Tintenschicht (14) bedruckt
sind, welche eine nicht-planare Oberflächentopographie aufweist, wobei das Verfahren
ein Auftragen einer Klebschicht (16) auf die Oberfläche des bedruckten Substrates
(12), wobei die Klebschicht (16) eine erste Oberfläche, die sich an die nicht-planare
Oberflächentopographie der Tintenschicht (14) anpaßt und mit dieser verbindet, und
eine gegenüberliegende, im wesentlichen planare Oberfläche, die im wesentlichen parallel
zu der Ebene des Substrates (12) angeordnet ist, aufweist, und ein Auftragen eines
im wesentlichen planaren transparenten Filmes (18) auf die planare Oberfläche der
Klebschicht (16) umfaßt.
2. Verfahren nach Anspruch 1, welches den Schritt einer Erwärmung der Klebschicht (16)
während ihrer Auftragung auf das bedruckte Substrat (12) auf eine Laminierungstemperatur,
bei welcher sich die Klebschicht (16) an die nicht-planare Oberflächentopographie
der Tintenschicht (14) anpaßt und mit dieser verbindet, beinhaltet, wobei die gedruckte
Tintenschicht (14) in einem im wesentlichen festen Zustand während der Auftragung
der Klebschicht (16) gehalten wird.
3. Verfahren nach Anspruch 1 oder 2, welches eine Druckbeaufschlagung des bedruckten
Substrates (12) während der Auftragung der Klebschicht (16) darauf umfaßt.
4. Verfahren nach Anspruch 2 oder 3, bei welchem der transparente Film (18) in der Form
eines Verbundwerkstoffes mit einer Klebschicht (16) mit einer heizbaren Kontaktfläche
(26) in Kontakt gebracht wird, wobei die Klebschicht (16) auf eine Laminierungstemperatur
während der Auftragung der Klebschicht (16) auf das bedruckte Substrat (12) erwärmt
wird, und bei welchem das bedruckte Substrat (12) mit einer zweiten Fläche (28), die
eine Temperatur aufweist, welche nicht größer ist als die Laminierungstemperatur während
der Auftragung der Klebschicht (16) auf das bedruckte Substrat (12) in Kontakt gebracht
wird.
5. Verfahren nach Anspruch 4, bei welchem die zweite Fläche (28) und die heizbare Kontaktfläche
(26) in der Form von Rollen vorliegen.
6. Verfahren nach Anspruch 4 oder 5, welches ein Positionieren einer thermischen Isolierschicht
zwischen dem bedruckten Substrat (12) und der zweiten Fläche (28) umfaßt.
7. Verfahren nach einem der vorhergehenden Ansprüche, welches eine Druckbeaufschlagung
des bedruckten Substrates (12) von etwa 140 bis etwa 420 kPascal während der Auftragung
der Klebschicht (16) darauf umfaßt.
8. Verfahren nach einem der vorhergehenden Ansprüche, bei welchem die Klebschicht (16)
und der transparente Film (18) gleichzeitig auf das bedruckte Substrat (12) aufgetragen
werden.
9. Bedrucktes Substrat, das ein Drucksubstrat (12), das mit einer Tintenschicht (14)
bedruckt ist, welche eine nicht-planare Oberflächentopographie aufweist, eine Klebschicht
(16), die auf dem bedruckten Substrat (12) vorgesehen ist und eine erste Oberfläche,
welche sich an die nicht-planare Oberflächentopographie der Tintenschicht und vorzugsweise
auch an das darunterliegende Drucksubstrat (12) anpaßt und mit diesen verbindet, und
eine zweite sowie gegenüberliegende, im wesentlichen planare Oberfläche, welche im
wesentlichen parallel zu der Ebene des Drucksubstrates (12) angeordnet ist, aufweist,
und einen im wesentlichen planaren transparenten Film (18), der über der im wesentlichen
planaren zweiten Oberfläche der Klebschicht (16) angeordnet und an dieser befestigt
ist, umfaßt.