Clear protective overcoat for a printed medium

US007037398B2

(12) United States Patent

Kwasny et al.

(io) Patent No.: (45) Date of Patent:

US 7,037,398 B2 *May 2, 2006

(58) Field of Classification Search 156/230,

156/234, 237-241, 277, 247, 289, 540, 580, 156/587, 583.1, 582, 581; 427/146-148; 428/40.1, 41.7, 41.8, 42.3, 343, 195, 200, 428/202, 203, 914 See application file for complete search history.

(56) References Cited

U.S. PATENT DOCUMENTS

4,738,555 A 4/1988 Nagashima

4,861,409 A * 8/1989 Hashida et al 156/308.2

5,220,343 A 6/1993 Takanashi et al.

5,427,997 A 6/1995 Oshima et al.

5,486,397 A * 1/1996 Gordon et al 428/76

5,555,011 A 9/1996 Tang et al.

5,560,979 A * 10/1996 Bloom et al 428/195.1

5,847,738 A 12/1998 Tutt et al.

5,942,330 A * 8/1999 Kelley 428/423.1

6,095,220 A * 8/2000 Kobayashi et al 156/540

6,264,296 Bl * 7/2001 Klinefelter et al 347/4

FOREIGN PATENT DOCUMENTS

EP 0 487 727 6/1992

EP 0 743 192 11/1996

EP 0 775 593 5/1997

* cited by examiner

Primary Examiner—Sue A. Purvis

(57) ABSTRACT

A transparent, protective overcoat for a printed medium achieved with a thermal transfer material on a carrier ribbon that is heated and pressed to transfer a segment of thermal transfer material from the carrier ribbon onto the printable surface of a medium.

10 Claims, 2 Drawing Sheets

1

CLEAR PROTECTIVE OVERCOAT FOR A
PRINTED MEDIUM

CROSS REFERENCE TO THE RELATED

APPLICATION(S) 5

This is a divisional of application Ser. No. 09/629,835 filed on Jul. 31, 2000 ABN, which is hereby incorporated by reference herein.

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FIELD OF INVENTION

The present invention, relates to a clear protective overcoat for a printed medium, achieved with a thermal transfer material and a carrier ribbon forming a donor web which is 15 subjected to heat and pressure to transfer a segment of thermal transfer material from the donor web onto the printed area on the printable surface of a medium.

BACKGROUND OF INVENTION 20

Digital photography and imaging provide cost-effective alternatives for capturing images, but known methods of producing durable, hardcopy prints of digitally printed areas are at least as expensive as traditional photographic meth- 25 ods. Further, with increasing use of various printing and imaging technologies in the publishing industry as well as in the home, protecting imaged or printed documents against abrasion, water alcohol, other liquid spills, ink smear, fading, blocking or other image-degradation processes and 30 effects has become an important consideration. Such protection is particularly desirable for printed or imaged documents produced with water-based (water-soluble) or other liquid inks, as well as documents printed or imaged with toner. These are commonly used in ink-jet printing, offset 35 printing, electrophotography and the like.

Photography provides an easy and reliable way to permanently capture images for a variety of uses. While photographs provide durable images, they are prone to scratches, have poor resistance to light and ultraviolet radia- 40 tion (which causes photographic images to fade over time), and degrade when exposed to water, other liquids or to vapors of such liquids. Traditional photography uses harsh and expensive chemicals, requires silver recovery, and involves a process requiring several intermediate steps of 45 handling negatives. While photographic processes can be automated, such automatic processing machines are expensive and bulky and do not eliminate the inherent problems of chemical exposure and handling negatives. Additionally, producing large prints (larger than the traditional 3-by-5 inch 50 or 4-by-6 inch prints) can be quite expensive.

Hot and cold laminates are the most common methods used to protect printed areas. However, laminates tend to be expensive, typically costing 6 to 80 cents per square foot for materials. The labor-intensive nature of producing durable 55 prints via lamination also increases the cost of such prints. Laminates may be applied on one or both surfaces of the print. One-sided lamination may lead to excessive curling of the final print, whereas two-sided application can be very expensive in terms of material and labor costs and may 60 excessively increase the thickness of the final print. Adhesives used for cold laminates may be tacky at room temperature, leaving a sticky residue at the edges of the prints. Additionally, binders used in creating cold laminates are typically water-based, which means the print may delami- 65 nate if exposed to excessive water or other liquid. Laminates are also susceptible to trapped air pockets, which are viewed

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as image defects. Most importantly, care must be taken to ensure that the laminates are accurately aligned to the media, and such alignment is especially critical for a continuous web laminate. These are just some of the deficiencies of traditional laminates.

Liquid overcoats are also commonly used to protect photographic prints and are becoming more popular as protective coatings for inkjet printed areas. Typical systems for applying these overcoats rely on roller coating or gravure type systems to dispense, gauge, and apply the coating. Smaller systems typically apply the overcoat off-line, rather than being an integral part of a single printing and coating unit. Larger systems used by the printing industry are in-line, but require extensive monitoring. Both systems require significant manual cleaning or intervention to maintain the components that contact the liquid.

Liquid overcoats tend to be slightly less expensive than laminates (6-18 cents per square foot). However, because currently available systems must be cleaned frequently and regularly monitored, these methods of using liquid overcoats are just as labor-intensive as the lamination methods, if not more labor-intensive.

Additionally, many of the overcoat formulations have residual odors before and/or after application, and some people find these odors offensive or even harmful.

Ultraviolet (UV) light curable liquid overcoats are also available, such as the overcoats commonly used to protect magazine covers. In such a UV-curable system, the liquid is first applied to the surface of the print and then cured to yield a solid, durable, protective coating. Because these liquids are widely used in large volumes for the magazine industry, their cost tends to be significantly lower than most other overcoat options. However, the systems used to apply such UV-curable overcoats tend to be more complicated and costly than other liquid overcoat systems, due to the multistep application and cure process. Additionally, many of the overcoat formulations have strong odors, some of which are harmful or offensive to people. Furthermore, there are potential safety problems associated with the handling of the potentially hazardous liquids used in this process.

Malhotra (U.S. Pat. No. 5,612,777 assigned to Xerox), Tutt & Tunney (U.S. Pat. No. 5,847,738 assigned to Eastman Kodak Co.) and Tyagi et al. (U.S. Pat. No. 5,783,348 assigned to Eastman Kodak Co.) disclose methods of applying a clear, scratch-resistant, lightfast, toner coating onto printed areas. Malhotra describes photocopied color images created by first, depositing color toner on a charge retentive surface; second, depositing a clear polymer toner material onto the charge retentive surface; and third, transferring and fusing the color toner and clear polymer toner material onto a substrate. Tutt & Tunney describe a process of depositing and fusing a clear polymer toner on inkjet printed areas. Tyagi et al. describes a similar process for coating clear toner over silver halide printed areas.

Similar electrostatic coating methods are also commonly used in the commercial painting industry to powder coat products, parts, or assemblies. One powder coating method charges a powdered paint using an air gun outfitted with an electrode before spraying the charged paint onto an electrically grounded object. Alternatively, an electrically grounded object may be immersed in a charged, fluidized bed of paint particles (typically referred to as"fluidized bed powder coating").

Another Malhotra patent (U.S. Pat. No. 5,906,905 assigned to Xerox) discloses a method of creating photographic quality prints using imaging such as xerography or ink jet by, first, reverse reading toner printed areas on a