This invention relates to ink jet printing of color images on polymeric sheets and laminates, and more particularly to the manufacture of three-dimensionally shaped polymeric sheets and laminates with color-matched digitally printed full color ink jet images.
Three-dimensionally shaped polymeric sheets and laminates are commonly printed with full color decorative print patterns. The printed sheets or laminates can be bonded to an injection molded substrate to make the finished part. These products can include interior automotive parts such as dashboard parts and gauges with decorative finishes, including decorative wood grain, and other products such as cell phones, personal electronic equipment (MP3 and CD players), EMI/RFI shielding, signs, and outdoor siding panels, for example.
These products are commonly made by a gravure printing process in which color separations in individual layers are initially sent to an engraver and produced on gravure plates. Inks are produced for individual color layers, and a composite is made to duplicate the customer's color sample. When the colors are acceptable, these steps are repeated to produce production gravure cylinders. The composite is then color-matched on a gravure press, and when the color match is acceptable, the gravure cylinders print the finished pattern. The substrate can comprise a polymeric sheet printed with several passes through the gravure press to produce the various color elements of the finished design. The sheet then can be laminated to a substrate and thermoformed and/or injection molded to a finished three-dimensional shape.
Digital printing allows use of computer generated and enhanced images. This can provide substantial design and production advantages over gravure printing. Computer generated images can be stored and instantly produced from computer memory. This also allows multiple designs to be printed at the same time, whereas with gravure printing, each separate design print must be made in the multi-step process described above.
The present invention provides a process for making ink jet printed products such as thermoformable polymeric sheets and laminates with color-matched digitally printed full color ink jet images.
In one embodiment, the invention comprises a process for making a thermoformable laminate which includes a flexible thermoformable polymeric sheet or film, also referred to herein as a baseweb. The baseweb is placed in an ink jet printer and a solvent-based (non-aqueous) digital printing ink is applied directly to the baseweb, in the absence of an ink receptive layer on the baseweb, to form a digitally printed decorative ink jet pattern in multiple colors with good ink adhesion in a single pass through the printer. This is followed by thermoforming and/or molding the finished printed baseweb into a three-dimensional shape. In a separate embodiment of the invention, the print pattern on the baseweb can be protected by a laminated transparent protective polymeric topcoat. In another embodiment, the digital printing can be directly applied to the underside of a clear coat layer to form a decorative pattern on the clear coat layer in multiple colors in a single pass through the printer.
Another embodiment of the invention comprises a process for making a color-matched thermoformable decorative laminate. The process includes producing a software-driven image of a pattern on a screen to represent a standard color print pattern, and evaluating and adjusting the standard as displayed on the screen using software-driven image-related adjustments for hue, contrast, lightness/darkness, saturation, resolution and image size, for example. A test print is then produced by the steps of applying a decorative pattern to a thermoformable polymeric sheet or film (baseweb), using a digital ink jet printer, and making an optional software-driven image-related adjustment in the standard as displayed on the screen to color-match the standard to the test print image. When the adjusted standard image displayed on the screen is acceptable, an image-related output is passed to the digital ink jet printer for printing on a baseweb a decorative print color-matched to the accepted on-screen standard.
Compared with gravure printing, the digital printing process of this invention speeds the color-matching processing and the process of producing multiple color images. The invention also provides high quality digitally printed images on three-dimensionally shaped parts in which the applied ink jet images have good print quality, abrasion resistance and adhesion to the substrate. The invention also provides digitally printed laminates having a protective outer layer having exterior grade long-term weatherability, durability, and optical properties such as high gloss. Printing directly on the baseweb provides substantial cost savings. Another advantage is that one can see what the product looks like immediately after it is printed. With gravure printing, on the other hand, a sample is taken off-line and laminated to a baseweb piece, which slows the color matching process.
Digitally printed images can be applied to selected areas such as the exact patterns corresponding to the thermoformed parts, whereas with gravure printing, the entire width of the baseweb must be printed with printed scrap areas between the thermoformed parts. There can also be substantial cost saving advantages in production by eliminating the need for lengthy lacquer production and color qualifying time.
These and other aspects of the invention will be more fully understood by referring to the following detailed description and the accompanying drawings.
The present invention provides a process for making digitally printed products in which multiple color decorative print patterns are applied to a polymeric sheet or laminate by a digitally-controlled ink jet printer. The polymeric sheet or laminate comprises a thermoformable material in the form of a flexible film or sheet or a semirigid sheet (each of which is referred to herein as a baseweb) on which a decorative image is digitally printed. Digital printing of this invention allows the use of computer generated and enhanced images. The finished product is characterized by color-matched digitally printed full color ink jet images. The invention provides substantial design and production advantages over gravure printing. To that end, the invention may be more fully appreciated by initially referring to the schematic flow diagram of
Generally speaking, the different constructions comprise various combinations of polymeric sheets or films (basewebs) to which a print layer is applied. The print layer refers specifically to digital printing, preferably ink jet printing. In one embodiment, there are from four to six color cartridges in the digital printer. The color in each cartridge is kept constant. A software program controls how these set colors are combined to produce an image. Printing can be directly applied to the polymeric baseweb, which is preferably a flexible thermoformable polymeric material capable of being transported through an ink jet printer to receive the digitally controlled multiple color ink layers from the ink jet head. In one embodiment, organic solvent based (non-aqueous) digital printing ink is applied to a baseweb surface having an absence of an ink receptive layer. The digital printing inks are generally vinyl and acrylic resinous materials. The polymeric sheet or film has sufficient flexibility that it can be unwound from a supply roll, passed through the printer, and stored on a take-up roll, at high print speeds. Machine adjustments to the digital printer can be made to adapt to printing on different polymeric baseweb materials. These machine adjustments include drying time (speed of baseweb), printing speed and heating the baseweb. A forced air or infrared dryer can be used for heating the baseweb before and after printing, to improve ink adhesion and to dry the printed ink pattern.
In a presently preferred embodiment of the invention the polymeric sheet or film (baseweb) on which the printing is applied is from about one to about 40 mils in thickness. The baseweb can be a thermoformable semirigid backing sheet which has sufficient flexibility to be transported through the ink jet printer; or the baseweb can comprise a thin flexible film usually supported by a flexible temporary carrier sheet. The semirigid sheets are generally about 10 to about 40 mils in thickness. Opaque polymeric sheets or films can include ABS, TPO, polycarbonate, acrylic and urethane. Optically clear sheets or films can include polycarbonate, PETG, acrylic and urethane. Thin polymeric films used as a baseweb can include PVC, PVDF/acrylic and urethane resins. These films are typically from about one to three mils in thickness. These films can be supported by a temporary carrier sheet, such as PET, during printing.
The digitally printed products may include a protective topcoat having weatherability and durability properties sufficient for protecting the underlying construction. The protective topcoat is a weatherable, exterior grade durable, optically clear polymeric material, which is also preferably thermoformable. Presently preferred materials comprise PVDF/acrylic, PVC, urethane and acrylic resins. The PVDF/acrylic topcoat preferably has a 63/37 ratio of solids content and is available under the designation AVLOY from Avery Dennison Corporation.
A clear primer may be necessary to adequately bond the print layer to various topcoats. Acrylic resins are commonly used for the primer coat. A tie coat layer also may be applied to a polymeric sheet or film to bond the print layer to the sheet or film. Tie coat materials can include acrylic resins for ABS, and a two-layered tie coat for TPO which includes a CPO (chlorinated polyolefin) that contacts the TPO and an acrylic resin that contacts the print layer. As described below, the print layer can be applied to a transparent protective topcoat layer in some constructions.
Printing inks useful in this invention include (1) 3M Scotchcal Piezo Ink Jet Ink Series 3700, (2) Roland FPG Series and CR-MR2 Series cartridges, and (3) Inkware (division of Vutek) printing ink. Ink jet printers useful for carrying out the invention include (1) Scitex “Novo Green,” (2) Vutek “Ultra Vu 3360” and “Ultra Vu 2360 SC,” (3) Roland “Hi-Fi Jet Pro,” and (4) “Arizona” printer from Raster Graphics.
The Roland printer uses the Roland printing inks and the 3M printing inks. The Vutek printer uses the Inkware inks. The Scite printer uses its own brand of inks. Organic solvent-based inks with pigments have produced superior weathering results. Failures were produced under similar conditions with water-based inks that contained dyes.
Referring now to the various constructions of digitally printed products which illustrate principles of this invention,
This example (and Examples 2 to 4) describe digital printing on a baseweb comprising a thin polymeric film supported by a temporary carrier and subsequently laminating the baseweb to an ABS backing sheet. A roll of 1.0 mil transparent PVC film, supported by a 1.0 mil high-gloss PET temporary carrier, was placed in an ink jet printer. Images were printed directly on the surface of the film, in the absence of an ink receptive layer on the baseweb. The film was heated to 120 deg. F. immediately before contact with the print head. The laminates and films of this invention are pre-heated prior to printing for improved ink adhesion. As presently understood, 120° F. is the minimum temperature needed for good adhesion. Several images of different colors were printed side-by-side on the PVC film. These images had previously been adjusted using software that changes such print quality factors as hue, contrast, lightness/darkness, saturation, resolution, and image size.
The ink jet printer was the Vutek 3360. The printed ink was from the Inkware line of organic solvent-based inks. The Vutek 3360 ink jet printer had a resolution of 360 dpi (dots per inch).
After the PVC film exited the print head, the film was heated in-line with an infrared heater. This again raised the film temperature to 120 deg. F., which facilitated solvent drying of the printed inks.
The film was printed at the rate of approximately 200 square feet per minute.
After the film was removed from the printer, it was tested for retained solvent. The retained solvent was 8.4%, which is comparable to a gravure printed sample of PVC film.
The printed film was then heat and pressure laminated to a 20 mil ABS backing sheet. The laminating drum pressure was 80 psi, the line speed was 25 fpm, and the drum temperature was 400 deg. F. The PET carrier was removed during the laminating step.
After laminating, the sheet was thermoformed to a three-dimensional shape at a sheet temperature of 330 deg. F. The gloss, color and DOI of the thermoformed sheet were visually comparable to a gravure printed product.
The thermoformed piece was trimmed, and placed in an injection mold, where an ABS substrate material was molded to the back of the laminate sheet.
The resulting injection molded part was tested in a Xenon Weatherometer. The test spec. used was SAE J1885. After 500 and 1240 kilojoules exposure, the sample had retained its original gloss and DOI. (Gloss retention is considered comparable if at least 70% retention is produced for all accelerated weathering samples.) The color print quality of the resulting laminate was judged to be comparable to a gravure printed laminate.
In terms of gloss readings, this example (and Examples 2, 3 and 6 to 9, to follow) generally produced minimum gloss readings of 50 gloss units (measured on a 60 degree meter) for the high-gloss basewebs.
A roll of 0.7 mil transparent urethane film, supported by a 1.0 mil high-gloss PET temporary carrier, was placed in an ink jet printer. The same printer, printing inks, printing rate, resolution, and images were used as in Example 1. The urethane film did not have an ink receptive layer. The urethane film was heated to 160 deg. F. immediately before contact with the print head. The higher film pre-heat temperature (as compared to Example 1) was found to give a better print appearance for the urethane.
The ink jet images were printed directly onto the film surface, and the film was again heated in-line with an infrared heater, to a film temperature of 120 deg. F., for solvent drying the printing inks.
After the film was removed from the printer, it was tested for retained solvent. The retained solvent was 8.8%, which is comparable to a gravure printed sample of urethane.
The same laminating, thermoforming, and injection molding steps were used as in Example 1.
The resulting injection molded part was tested in the Xenon Weatherometer, using the SAE J1885 test spec. After 500 and 1240 kilojoules exposure, the sample had retained its original gloss and DOI.
A roll of 1.8 mil transparent PVDF/acrylic film, supported by a 2.0 mil high-gloss PET temporary carrier, was placed in an ink jet printer. The same printer, printing inks, printing rate, film pre-heat temperature, infrared heating, resolution, and images were used as in Example 2. The film did not have an ink receptive layer.
After the film was removed from the printer, it was tested for retained solvent. The retained solvent was 2.9%, which is comparable to a gravure printed sample of PVDF/acrylic film.
The same laminating, thermoforming, and injection molding steps were used, as in Examples 1 and 2.
The resulting injection molded part was tested in the Xenon Weatherometer, using the SAE J1885 test spec. After 500 and 1240 kilojoules exposure, the sample had retained its original gloss and DOI.
In addition, thermoformed (but not injection molded) samples were subjected to the following tests:
2000 hours QUV (ASTM G53 spec.)
2000 hours Xenon Weatherometer (SAE J1960 spec.)
500 hours Carbon Arc Weatherometer
72 hours water immersion at 70 deg. C.
At the conclusion of the water immersion test, the General Motors tape test GM 9071 was performed, and the sample passed. All of the samples in the accelerated weathering tests retained their original gloss and DOI.
A roll of 0.7 mil translucent, low-gloss urethane film, supported by a matte 1.0 mil PET temporary carrier, was placed in an ink jet printer. The low gloss carrier produces low gloss products having a 60-degree gloss below about 10 gloss units. The same printer, inks, printing rate, film pre-heat temperature, infrared heating, resolution, and images were used as in Examples 2 and 3.
After the film was removed from the printer, it was tested for retained solvent. The retained solvent was 10.7%, which is comparable to a gravure printed sample of low-gloss urethane film.
The same laminating, thermoforming, and injection molding steps were used, as in Examples 1, 2 and 3.
The resulting injection molded part was tested in the Xenon Weatherometer, using the SAE J1885 test spec. After 500 and 1240 kilojoules exposure, the sample was close to its original gloss and DOI. For the 500 kJ Xenon test, initial 60 degree gloss measured 8.1 gloss units; final 60 degree gloss measured 6.0 gloss units.
This example describes digital printing directly on an ABS backing sheet. A roll of semirigid 10 mil opaque grey ABS sheet was placed in an ink jet printer. The same printer, printing inks, printing rate, resolution, infrared heating, and images were used as in Example 1. The ABS sheet did not have an ink receptive layer.
After the ABS sheet was removed from the printer, it was tape tested for ink adhesion. The test used was General Motors spec. GM 9071. No ink was removed during this test.
The printed ABS sheet was then thermoformed, using the same conditions as in Example 1.
After thermoforming, the GM 9701 test was again performed. The sample passed with no ink removal.
This example describes printing directly on a transparent backing sheet. A roll of 1.8 mil transparent PVDF/acrylic film, supported by a 2.0 mil high-gloss PET temporary carrier, was placed in an ink jet printer. The same printer, inks, printing rate, film pre-heat temperature, infrared heating, resolution, and images were used as in Example 3.
The resulting film had the same retained solvent level as in Example 3.
The printed PVDF/acrylic film was laminated to a sheet of transparent 20 mil PETG. The resulting product had a translucent appearance, allowing a substantial amount of visible light through the laminate.
The laminating and thermoforming conditions were the same as in the previous Examples. The sample was not injection molded.
The resulting thermoformed part was tested in the QUV ultraviolet condensation tester for 2800 hours. The test method used was ASTM G53. After the 2800 hours exposure, the sample had retained its original gloss, color, and DOI.
This example (and Example 8) describes use of different ink jet printers. A roll of 1.8 mil transparent PVDF/acrylic film, supported by a 2.0 mil high-gloss PET temporary carrier, was placed in an ink jet printer. The printer used this time was the Arizona, manufactured by Raster Graphics. Several images of different colors were printed side-by-side on the film. The resolution of these images was 300 dpi. The inks used were of the 3M Scotchcal Piezo Ink Jet Series 3700.
The film was printed at the rate of approximately 90 square feet per minute. Printing was directly onto the film surface, in the absence of an ink receptive layer.
The printed film was then laminated, thermoformed, and injection molded in the same manner as in Examples 1 through 4.
The resulting injection molded part was tested in the QUV ultraviolet condensation tester for 2800 hours. The test method used was ASTM G53. After the 2800 hour exposure, the sample had retained its original gloss, color, and DOI.
A roll of 1.0 mil transparent PVC film, supported by a 1.0 mil high-gloss PET temporary carrier, was placed in a Roland Solvent Jet ink jet printer. Several images of different colors were printed side-by-side on the film. The resolution of these images was 1440 dpi. The inks used were of the Roland FPG series, printed with the CR-MR2 cartridges.
The film was printed at the rate of approximately 16 square feet per minute, and printing was directly onto the film surfaces.
The printed film was then laminated, thermoformed, and injection molded in the same manner as in Examples 1 through 4. Because of the higher resolution, these samples were judged to be superior in quality to gravure printed samples.
This example describes printing on a clear baseweb followed by laminating to a TPO backing sheet. A roll of 1.8 mil transparent PVDF/acrylic film, supported by a 2.0 mil high-gloss PET temporary carrier, was processed with the same printing steps, and the same processing conditions, as in Example 3.
The printed film was then heat and pressure laminated to a white 20 mil TPO sheet. This TPO sheet had previously been laminated with a CPO/acrylic two-layer coating for improved adhesion. The printed side was laminated to the acrylic side of this two layer coating. The laminating drum pressure was 80 psi, the line speed was 25 fpm, and the drum temperature was 380 deg. F.
After laminating, the sheet was thermoformed at a sheet temperature of 320 deg. F. The gloss and DOI of the thermoformed sheet were comparable to a gravure printed product.
The thermoformed piece was trimmed, and placed in an injection mold, where a TPO substrate material was molded to the back of the laminate sheet.
The resulting injection molded part was tested in the Xenon Weatherometer. The test spec. used was SAE J1885. After 500 and 1240 kilojoules exposure, the sample had retained its original gloss and DOI.
This example describes digital printing on a TPO backing sheet. A roll of 20 mil opaque black TPO sheet was placed in an ink jet printer. This TPO sheet had previously been laminated with a CPO/acrylic two-layer coating for improved adhesion. The acrylic part of the two-layer coating was printed with the inks. The same printer, inks, printing rate, resolution, infrared heating, and images were used as in Example 1.
After the TPO sheet was removed from the printer it was tape tested for ink adhesion. The test used was GM9071. No ink was removed during this test.
The printed TPO sheet was then thermoformed, using the same conditions as in Example 9.
After thermoforming, the GM9071 test was again performed. The sample passed, with no ink removal.
A roll of 20 mil opaque brown ABS sheet was placed in an ink jet printer. The same printer, inks, printing rate, resolution, infrared heating, and images were used, as in Example 1. Printing was directly onto the surface of the ABS sheet.
The ABS sheet was then removed from the printer. A piece of transparent 1.8 mil PVDF/acrylic film, supported by a 2.0 mil high-gloss PET temporary carrier, was laminated to the printed side. The laminating pressure was 80 psi, the line speed was 25 fpm, and the laminating drum temperature was 400 deg. F.
The laminate was then thermoformed and injection clad, using the same conditions of Example 1.
The resulting injection molded part was tested in the Xenon Weatherometer, using the SAE J1885 spec. After 500 and 1240 kilojoules exposure, the sample had substantially retained its original gloss, color, and DOI. The appearance of this part was judged to be equal to the sample produced in Example 3. For the 1240 kJ Xenon test, initial 60 degree gloss measured 79.6; final 60 degree gloss measured 59.3.
A roll of 20 mil opaque black TPO sheet was placed in an ink jet printer. This TPO sheet had previously been laminated with a CPO/acrylic two-layer coating for improved adhesion. The acrylic part of the two-layer coating was printed with the inks. The same printer, inks, printing rate, resolution, infrared heating, and images were used, as in Example 1.
The TPO sheet was then removed from the printer. A piece of 1.8 mil PVDF/acrylic film, supported by a 2.0 mil high-gloss PET temporary carrier, was laminated to the printed side. The laminating pressure was 80 psi, the line speed was 25 fpm, and the laminating drum temperature was 400 deg. F.
The laminate was then thermoformed and injection clad, using the same conditions of Example 9.
The resulting injection molded part was tested in the Xenon Weatherometer, using the SAE J1885 spec. After 500 and 1240 kilojoules exposure, the sample had retained its original gloss, color, and DOI. The appearance of this part was judged to be equal to the sample produced in Example 9. For the 1240 kJ Xenon test initial 60 degree gloss measured 76.2; final 60 degree gloss measured 67.8.
A roll of 20 mil clear PETG sheet was placed in an ink jet printer. The same printer, printing inks, printing rate, resolution, infrared heating, and images were used, as in Example 1. Printing was directly onto the PETG sheet, in the absence of an ink receptive layer.
The printed PETG sheet was thermoformed at a sheet temperature of 300 deg. F. The resulting thermoformed piece had gloss and DOI comparable to the (high-gloss baseweb) samples of Examples 1, 2, and 3. The PETG maintained its transparency after thermoforming. Due to the translucency of the ink jet print, the thermoformed piece had some visible light transmission.
A roll of 3 mil opaque adhesive-backed PVC film was placed in an ink jet printer. Printing was directly onto the surface of the film. The PVC is commercially available from the Avery-Dennison Corp., and has the product number MPI 1005. The same printer, inks, printing rate, and resolution were used, as in Example 7. The PVC film was supported by a temporary carrier. The film was not pre-heated.
The resulting film was tested for ink adhesion, using the GM 9071 spec. No ink was removed during this test.
The film was then placed on a vacuum table. A two-component urethane, commercially available as Chem-Dec 829, was poured on the ink jet printed pattern, to a depth of 40 mils. The urethane was allowed to dry at room temperature for 24 hours, at which time it was considered fully cured.
The resulting product had a 20 deg. gloss of 60 and a DOI of 90. These readings were much higher than the other Examples, due to the greater thickness and clarity of the urethane.
Number | Date | Country | |
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Parent | 09947077 | Sep 2001 | US |
Child | 11894325 | Aug 2007 | US |