WO1999010183A1

WO1999010183A1 - Sublimation composite printing on fabrics

Info

Publication number: WO1999010183A1
Application number: PCT/US1998/017915
Authority: WO
Inventors: D. Grier Ii William
Original assignee: Apparel Technologies, Inc.
Priority date: 1997-08-28
Filing date: 1998-08-28
Publication date: 1999-03-04
Also published as: AU9210598A

Abstract

Composite printing is employed to transfer foreground (12) and background (14) dot colors from an electrostatic surface (26) to a fabric substrate (16) by sublimation under action of heat and pressure. Dots (28) are formed by a digital printing and are configured to have a concave cross section (30) which sublimes at its lowest point first enabling implosion sublimation transfer of dots without substantial dot gain.

Description

SUBLIMATION COMPOSITE PRINTING ON FABRICS

Field of Invention

The present invention is directed to composite printing on fabrics using sublimation color transfer.

Background of the Invention

Composite printing may be defined as the combining of two or more printing techniques to produce a single product. Composite printing conventionally employs screen or lithographic printing processes to produce a quality finished product at increased production rates and at reduced cost.

Composite printing has been used for many years in the advertising industry. Billboard advertisements, for example, employ a product where a four-color image of a person or persons is lithographicly printed as foreground and a solid spot-color background later applied by screen printing. Banners have also been produced by composite printing where the foreground is lithographicly or screen printed and background added by screen printing around a carefully positioned mask. Composite printing has great utility when a constant background is to be printed in combination with a variable foreground. Product applications include licensed apparel, uniforms, active wear, banners, flags, large decals, specialty promotion items and home furnishings.

Fabrics have been printed by direct transfer, heat split and sublimation processes. Direct transfer printing involves the transfer of one solid to another solid and is generally recognized as decal printing. Meat split printing a solid is liquefied and transfeπed to a fabric substrate. Sublimation printing involves the sublimation of inks and transfer of the gasified ink to a substrate with accompanying penetration of the substrate. This provides a more permanent, colorfast print as the dyes or color penetrate the filaments forming the fabric, but requires more energy. The problem with sublimation printing is the difficulty of controlling the sublimed color component or half-tone dots. Conventionally formed dots explode when sublimed and increased in size up to about 300 percent. This phenomenon is dot gain. This results in print overlap producing muddy colors, poor image definition and loss of portions of the color palate.

It would be desirable to provide a process where -precise control can be exercised over dot gain during transfer by sublimation and dots can be transfeπed from a donor source to a substrate a close one-to-one relationship giving high resolution and high print quality in any combination of colors and tones. It was recognized that if this could be achieved, it could be combined with other printing techniques to enable composite printing at high rates and low cost. This is the subject of the instant invention.

Summary of the Invention

The present invention is directed to the electrostatic formation of sublimation color dots on a donor surface in a substantially concave cross sectional configuration which enables the dots to implode and transfer from the donor surface to a receiving substrate substantially without dot gain. The invention is also directed to composite printing using such dots in which foreground image is printed simultaneously with a background image and where a physical trapping layer serves to prevent transfer to the substrate of the background image behind the area occupied by the foreground. The first aspect of the invention is achieved by use of solid dots having a concave cross section with a depressed center which on action of heat and pressure sublimate prior to the outer periphery thereby tending to implode and reform on a receiving substrate substantially without dot gain. Composite printing is achieved by combining a foreground pattern on a masking transfer surface which absorbs and retains background color and prevents background color from reaching the substrate combined with a background of any design and color to give precise, photo-perfect composite print to any receptive substrate, especially substrates formed of polymeric materials.

Because the foreground image can be changed on the fly, and applied anywhere on a background, without masking the background image, the composite product, can be printed at one-quarter to one-third of the cost of digital production alone. The process may be keyed to immediate market needs as compared to forecast production and provides four-color process printing of inks which is contained, at least in part, within a filament or thread forming the fabric eliminating thereby special washing instructions.

The Drawings

FIG. 1 schematically illustrates the composite printing process of the invention. FIG. 2 illustrates the construction of a laminate for composite printing employing a physical trap.

FIG. 3 illustrates a printed substrate. FIG. 4 illustrates the rear of the physical trap after sublimation printing.

FIG. 5 illustrates the presently prefeπed dot constmction of the invention on specialty paper used for sublimation printing as well as the physical trap to enable low-cost composite printing.

Detailed Description

FIG. 1 schematically illustrates the composite printing process scheme as applied, for example, to a polyester jersey. With reference thereto, the design to be applied to the jersey is first drawn (DRAW). The drawing is then scanned (SCAN) by a scanner into a computer. Drawing may involve generating art work by using digital software such as an Adobe Illustrator or PhotoShop to create digital images inside the computer. The computer drawing can be a 4-color piece to be printed by an electrostatic printer and a pattern and/or print background to be printed also using sublimation inks.

The scanned image which creates a digital file which is stored. The stored image is then color coπected (PREP) to compensate for color shift dust and/or scratches to ready the image for output using available photo retouching software. The prep step may also be effectively employed to reduce possibility of dot gain in the sublimation printer.

Once the image has been coπected and ready for printing, exact copies are made to effectively to fill all the available space on a digital press. Multiple and different images can be combined on a single printout. The layout is rasterized and sent to the electrostatic printer (E-STAT) and vectored to the cutter (CUT) to serve as a template for high speed cutting of individual elements. The image is then printed on the electrostatic transfer surface preferably electrostatic paper. Each foreground image for the composite constmction is printed an electrostatic transfer surface which is capable of physically containing and trapping any electrostatic ink it covers. The electrostatic transfer surface cuπently employed is Rexam 100 gram presentation grade electrostatic paper produced by Rexam, Inc. of South Hadley, Massachusetts. The significance of the selection of electrostatic paper will be-later described.

Printed images are then cut (CUT) precisely around the edges using a high speed CAD- driven cutter. The images are sorted (SORT) and stacked for forming a composite sandwich. The background is concuπently prepared. The background may be color flood on conventional electrostatic paper which is simply covered with solid color sublimation ink, (COLOR FLOOD) and/or another digital design (DESIGN). Multiple color flood and/or designs can be combined to give uniform or gradient multicolors of expansive area as may be desired for the garment. The color flood and/or design are cut to (TRIM) the rough size and shape of the fabric to be printed. This may done by hand or using an electric cutter. They are sorted (SORT) for combination with the printed foreground.

The cloth or fabric is then prepared by forming a computer-aided design (CAD) allowing the components of the garment to be made to be cut (CUT) to the proper size and shape, after which they are sorted (SORT). The composite shape is then created as a laminate with the foreground designs being imposed on the background(s) (Construct). The foreground may be adhered to the background by using glue stick and spray adhesives and the like. The composite sublimation papers are then placed on top of the cut material to be sublimated (CONSTRUCT).

With further reference to FIG. 2 and 3 composite 10 with foreground layer or layers 12 containing their visual indicia and background layer or layers 14 and their visual indicia and fabric 16 are fed to a press where by action of heat and pressure sublimation inks of the composite sublimate and transfer to and penetrate the fibers of the fabric substrate (TRANSFER) . There may be employed a roll press or a flatbed press. Transfer occurs at a temperature of from about 290"F to the heat distortion temperature of the fabric preferably from about 290' to about 385'F. Heat distortion is the temperature at which the character of the fabric will change, e.g., lose elasticity or other characteristics induced to the fabric at the time of fabric manufacture. The temperatures employed are lower than temperatures conventionally employed for sublimation printing, i.e., 400'F or more where fabrics can be iπeversibly adversely altered.

After printing the composite is separated from the sublimated material 16 and discarded. FIG. 3 illustrates the printed fabric while FIG, 4 illustrates the rear of the physical mask carrying the blocked background 18. The printed fabrics are then separated; sorted (SEPARATE and SORT), sewn together and a finished garment packaged and shipped (SHIP) for sale. By this process a single white background can be printed to any color or design as demand requires, eliminating the need for projecting potential customer demand for a color, or having to change colors after having acquired bolts of color fabric in hope that product can be manufactured from it before consumer demand forces a change of color or design.

As an example, the foreground 12, say that of a soccer player, is printed on one sheet of paper cut to size and the background 14, in this instance, say a stadium is also digitally printed on another sheet of paper. The foreground 12 is laid on the background 14 and adhered to it. When placed in the press, the foreground 12 transfers to the fabric 16 simultaneously with the background 14 in the areas where the foreground is absent and to the back 18 of the foreground pphysical mask 12. The physical mask traps the colors and prevents their reaching fabric 16. In this way, the foreground can be changed at will or "on the fly" and positioned anywhere on the background 14, giving complete control over the image formed. This is a key element enabling cost composite printing.

The image to be transfeπed is with reference to FIG. 5 printed onto electrostatic paper 20 comprised of a layer of paper 22, a conductive layer 24 and a dialectic layer 26. The paper is sufficiently moisturized by humidity control to become conductive. Concave dots 28 are created on the dielectric surface. The electrostatic surface is substantially uniformly electrostaticly charged. Nibs are employed to create dots forming the indicia to be created by modifying the charge on the surface of the paper. The paper is then passed over a toner (not shown) containing charged sublimation inks in a suitable fluid vehicle canier such as kerosene or isdpar and selectively attracted to the paper to form the image imparted by the nibs. There are several forms of dots which can be printed by sublimation printing. Only one is suitable for use in the process of the invention. This dot illustrated in FIG. 5 and I dot 28 having a concave surface with a central depression 30 with a higher periphery 32. The area beneath the central depression 30 vaporizes first, creating a vacuum, which causes implosion enabling printing of a color process densities with components up to about 90% and half tones substantially without dot gain. This may be contrasted to offset lithographic printing where component densities less than about 70% and screen printing where color densities less than about 50% and other digital printing methods where the upper limit is about 30%.

The dots, in consequence, transfer substantially without dot gain. "Dot gain" as used herein, means the ratio of the reflected area of a transferred dot back to the donor surface to the area of the dot occupied prior to transfer. As compared to prior electrostatic processes where dot gain was up to 300% or more, dot gain according to this invention effectively no more than 10 to about 20%. This is a combination of a physical reduction from 300% to about 60% coupled with a computer coπection of about 50%. Dots of the shape used was early used in Xerographic processing but later discarded as unacceptable and supplanted by generally convex dots which did not contain depressions. Such dots normally have tapered sides and explode outward, as opposed to imploding and are used for high saturation printing.

The toner inks preferably used in the invention are available from Hilord of Haupauge, Long Island and Specialty Toner Corporation of Fairfield, New Jersey. Toning is four- color process, black, cyan, magenta and yellow, forming dot clusters with varying dot density and different colors. The composite printing process of the invention combines the best features of digital and screen printing into a single process. Digital printing contributes the ability to change foreground or background on the fly while digital cutting and four color process management and conventional screen printing contributes spot- color solid area saturation and enables volume pricing. By reducing the printed area assigned to the digital printing, production can be increased 5 to 10 times based on the area for color process needed in the final product. A soccer jersey, for instance, produced at a rate of 175 units/day using digital printing alone, was increased to 2,000/day using the composite process of the invention giving the spot-color background and digital foreground, color. Production cost is reduced. For instance, a soccer jersey that is 20% digitally printed drops in cost from over $6.00/unit for a totally digitally printed to under $0.90 when composite production according to the invention.

The process is applicable for substrates including polymeric substrates such a polyester, nylon, polyvinyl chloride, polyolefins and the like, and for a whole range of synthetic apparel and banners. The process is not yet adaptable to natural fibers and rayon but allows printing on woven, knitted, non-woven, porous, non-porous and like substrates. Printable fabrics include those describe in "Industrial Products Review", July 1995, Fabric Incorporated herein by reference. Dot diameter is typically at about 0.055 inch after transfer. Transfer typically occurs a press pressure of about 30 to about 80 psi at a dwell time of about 20 to about 60 seconds.

In addition to the electrostatic printing of the dots on electrostatic paper as hereinabove described., the dot structure of the present invention may also be printed using heat sublimable inks on commonly used apparatus in lithography, screen printing and etching processes. The present invention is to be defined solely by the scope of the following claims.

Claims

ClaimsWhat is Claimed Is:

1. A process for the sublimation printing of multiple colors on a substrate comprising the steps of:

(a) forming on a first transfer surface a plurality of heat sublimable dots; said dots having a substantially concave surface facing substantially parallel to said transfer surface; (b) applying said transfer surface containing said dots on a receptive substrate to be printed, and

(c) subliming, at a sublimation temperature, said dots under action of heat and pressure applied for a time sufficient to sublime and transfer said dots to said substrate substantially without dot gain.

2. The process as set forth in Claim 1, in which dots are formed of the colors black, cyan, magenta, and yellow.

3. A process as set forth in Claim 1 in which the dots are sublimed at a sublimation temperature of from about 290┬░ F to about 385┬░ F.

4. A process as set forth in Claim 2 in which the dots are transfe╧Çed at a sublimation temperature of from about 290┬░ F to about 385┬░ F.

5. A process as set forth in Claim 1 in which the receptive substrate is a polymeric substrate.

6. A process as set forth in Claim 5 in which the receptive substrate is in the form of a woven, knitted or non-woven fabric.

7. A process as set forth in Claim 6 in which the fabric comprises a polymeric material selected from the group consisting of nylon, polyester and polyolefin.

8. A process as claimed in Claim 1 further comprising:

(d) forming on a second transfer surface a plurality of heat sublimable dots, the second surface having a back surface,

(e) placing the second surface over a portion of the first surface, wherein the back surface is in a facing relationship to the first dielectric surface, prior to performing the applying step (c).

9. A process as set forth in Claim 1 wherein said transfer surface is a dielectric surface.

10. A process as set forth in Claim 9 wherein said transfer surface is electrostatic paper.

11. A process as set forth in Claim 8 wherein said second transfer surface is a dielectric surface.

12. A composite printing process comprising the steps of:

(a) electrostaticly forming a foreground image on an electrostatic paper having an electrostatic transfer surface and a back surface, said foreground image being formed on said transfer surface, said back surface being capable of absorbing sublimable inks, said foreground image including a plurality of heat sublimable dots having a concave surface substantially parallel to said transfer surface;

(b) forming on a second surface a background image of heat sublimable ink;

(c) placing said electrostatic paper over a portion of said second surface with said back surface in a facing relationship to said second surface to combine said foreground image and said background into a composite image and applying said second surface and said transfer surface on a receptive substrate to be printed by heat sublimation;

(d) transfe╧Çing by sublimation, under action of heat and pressure, said composite image onto said substrate, said back surface absorbing ink from said background image from said portion of said second surface.

13. A process as claimed in claim 12 in which the dots are transfe╧Çed at a sublimation temperature of from about 290┬░ F to about 385┬░ F.

14. A process as set forth in Claim 12 wherein said receptive substrate is a polymeric substrate.

15. A process as claimed in claim 14 in which the receptive substrate is a woven, nonwoven or knitted fabric.

16. A process as claimed in claim 15 in which the fabric comprises a material selected from the group consisting of nylon, polyester and polyolefin.