CA2056741A1 - Dye thermal transfer sheet with anti-stick coating - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Thermal transfer dyesheets are disclosed containing highly efficient back-side antistick coatings. These are particularly useful in thermal dye transfer printing materials where relatively high temperatures are used in the thermal head and where dye offset from the front of one sheet to the back of an adjacent sheet is often a problem . These coatings comprise at least one polyfluorinated resin having an acrylate functionality, and at least one more resin having an acrylate functionality to provide a crosslinked matrix.

Description

DYE Tl-IERMAL TRANSFER S~EET WITH ~NT~-STICK (~OATING

Field of tlle Invention This invention relates to a dye thermal transfer sheet with an anti-stick coating and more particularly, it relates to a dye thermal transfer sheet with an anti-stick coating containing polyfluorinated acrylate containing compositions.
Back~roand of the Invention In recent years, thermal transfer systems have been developed to obtain prints from pictures generated electronically by a color video camera. According to one way of obtaining such plints, an electronic picture is first subjected to color separation by color 1~) filters. The respective color-separated images are then converged into electrical signals.
These signals are then operated on to produce cyan, magenta and yellow electrical signals.
These signals are then transmitted to a thermal printer. To obtain the print, a cyan, magenta or yellow dye-donor element (and sometimes a black element) is placed :face-to-face with a dye receiving element. The two elements are then inserted between a thermal printing head and a platen roller. A line-type thermal printing head is used to apply heat from the back of the dye-donor sheet. The thermal printing head has many heatingelements and is heated up sequentially in response to the cyan, magenta, or yellow signal.
The process is thell repeated for the other two colors. A color hard copy is thus obtained whicll corresponds to the original yicture viewed on a screen.
2n ~ problem has existed with the use of dye-donor elements for thel mal dye-trallsfer printillg because a thill s~lpport is required in order to provide effective heat transfer For example, when a thin polyester film is employed, it softens whell lleated durhlg the printing operation and can stick to the thermal printing head. This c~uses intermittent rather than continuous transport across the thermal head. The dye transferred thus may not appear as a uniform area, but rather as a series of alternating light and dark bands (i.e., chatter marks). Another defect called "smiles", which are crescent shaped low 2~67~

density areas, is produced in the reeeiving element by stretch-induced folds in the dye-donor element. Another defect is produced in the receiving element when abracled or melted deb~is from the backing layer builds up on the thermal head and causes streaks parallel to the travel direetion whieh may extend over the entire image area. In extreme eases, sufficient frietion is often ereated to tear the dye-donor element during printing.
It would be desirable to eliminate sueh problems in order to have a eommere;allyacceptable system.
In an attempt to solve the foregoing problems, dye-donor or thermal transfer imaging sheets employed in the industry frequently make use of an anti-stiek or slipping layer eoated on the side distant the thermal transfer layer. Materials diselosed for anti-st;ck coatings include linear thermoplastic as well as crosslinked polymers, with additives of either inorganic or organic materials and/or particulate materials to enhance some aspects of performance.
EPO Publieation No. 314,34~ diseloses a baekeoat (i.e., anti-stiek coating) composition for a thermal transfer dye-sheet which is representative of rnany such eoatings used in the industry. The EPO Publication discloses an anti-stick coating containing an organic resin comprising at least one polyfunctional matelial have a plurality of pendant or terminal acrylic groups per molecule available for cross-linking, at least 10% by weigllt of the polyfunctional material having ~-8 suell aerylic groups per moleeule; at least one linear organie polymer soluble or partially sol~lble in the resill; an(l eomprising l-40% by weight of the resin/polymer mixtllre, a slip agent selected from derivatives of long chain carboxylic or phosplloric acids, long alkyl chain esters of phosphoric: acids, and long alkyl chain acrylates; an antistatic agent soluble in the resin;
and a solid partieulate antiblocking agent less than 5~m in diameter.
ln the EPO Publication, the linear polymer is employed to impart flexibility to the eross-linked resin as well as to acljust eoating viseosity and improve adhesion of the eured film to the substrate. The separate slip system eonsists of salts of stea~c and hydroxy stearic acids; for example, lithium soaps, and salts of polyvalent metals and stearic acids ~ o ~

(such as zinc stearate). Thicknesses recommended with these materials are on the order of 1-5,um, preferably ],um. This places constraints on the antiblocking particulate size distribut;on .
There are several major disadvantages incurred with the use of the system disclosed by the EPO Publication. First, the slip properties of the film are imparted by mobile additives separate from the main cross-linked resin, which show a tendency to solvate dyes in the opposing layer and subsequently cont~minate the printhead with the dyes. Also, the slip agents employed are salts of metals such as lithium or zinc, which are generally undesirable since these metals' ions can migrate into the opposing dye layers which may affect image properties, and into the head construction which may cause printing element failure. Additionally, talc, when used in sufficient quantities to be the main antiblocking agent, may require the thermal printer to use excessive pressure to ensure contact with the print head. This pressure can cause the inorganic palticulate to abrade the printhead with time. Further, the average particle size of talc is reported as 2~1m, whicll can be expected to result in distributed protrusions from the antistick coating.
Finally, the recommended coating thicklless of from 1 to S,um contributes considerable thermal mass to the donor ribbon as a whole. With the standard 6~tm PET carrier film, the ribbon can be expected to require as a rninimum roughly an additional 20% printing energy to deliver the required printing density. This is a serious clisa(lvantage since the life of the costly printhead is a strong inverse function of the power expended in printing.
Fluorillated compounds have been disclosed for use in anti-stick layers and release layers. Fol example, EPO Publn. No. 263,47~ discloses thermal transfer ;maging materials with an anti-stick back layer. The transfer layer on the front surface comprises a non-flowable ink layer and an adhesive layer. An anti-stick back layer has a thickness in the range of O.OS,um to 3~m and contains a main component chosen ~rom fluorine-containing surface active agents and ~luorine-containing polymers. These main connponents are preferably mixed with heat resist~nt resins such as epoxy resins, silicone resins, phenolic resins, melamine resins, and polyester sulfones, and others. The 7 ~ 1 fluorine containing polymers disclosed are tetrafluoroethylene-hexafluoropropylene copolymers, polychlorotrifluoroethylene, polyvinylidene fluoride, ancl polytetrafluoroethylene.
Japanese Kokai JP63-062790 discloses the use of a cellulose derivative mixed with a resin which can be fluorinated. No further definition of the latter resin is provided, however, and such compounds are not disclosed in the examples. The layer thickness is stated to be in the range ~).05~m to 3,um.
Japanese Kokai JP63-074687 cliscloses anti-stick back layers of thieknesses in the range 0.2~m to 5,um containing polyurethane fluoride as the major component.
Japanese Kokai JP63-118296 discloses thermal transfer materials with the heat transfer layer on one side of a support. On the other side of the support is a heat resistant layer which contains a perfluoroaIkyl group-containing resin preferably selected from oligomers of tetrafluoroethylene and hexafluoropropylene, or from copolymers of a perfluoroalkyl group-containing vinyl monomer with (meth)acrylic acid or esters.l~ U.S. Pat. No. 4,631,232 discloses a heat-sensitive transferring recorcling rnaterial having a heat melting ink layer on one side of a substrate, and a "heat resistant convey~mce improving layer" on the other side of the substrate. The conveyance improving ]ayer comprises either UV radiation curable resins or compounds containing a perfluoroalkyl group. The former are illustrated by polyester acrylate, polyuretllane 2(~ acrylate, and epoxy acrylate, but no indication is made that ~he monomers in the curable resins may be fluorinated. The compounds containing perfluoroalkyl groups are not described as polymerizable monomers and are not UV c~lrecl, they are represented by salts or esters of perfluoroa]kyl carboxylic acids, salts of perfluoroalkyl sulfonic acid, esters of perfluoroalkyl phosphoric acid, perfluoroalkyl betaine, and perfluoroalkyl trimethyl ammonium salts.
U.S. Pat. No. 4,829,050 discloses therrnal transfer materials with an anti-stick back layer comprising TeflonTM particles dispersed in a cellulose binder.
U.S. Pat. No. 4,383,878 discloses a transfer material for indicia wherein a first SUppOlt base to which the indicia are applied has a release topcoat complising a radiation-2~7~1 curable polyfluorinated acrylate compound and a polyethylenically unsaturated crosslinking agent.
U.S. Pat. No. 4,321,404 discloses the same radiation-curable compositions disclosed in U.S. Pat. No. 4,383,87~ and presents utilities involving the controlled release of images applied to the adherent composition layers.
Although the foregoing disclosed anti-stick and release coatings containing fluorinated compounds are suitable for sheir intended use, improvements in such coatings are continually sought and desired by the industry for use in dye thermal trarlsfer systems.
Specifically, improvements with respect to the heat resistance, lubricity, dye impermeability, and self-cleaning properties of anti-stick coatings for thermal dye transfer sheets are constantly needed.

Summary ~the Invention By the present invention, an effective dyesheet for thermal transfer printing isprovided. The inventive thermal transfer dyesheet comprises a support having on one side thereof a thermal dye transfer layer and on the other side thereof an anti-stick layer comprising the polymerization reaction product of: (a) at least one polyfluorinated resin comprising an acrylate functionality; and (b) at least one ethylenically unsaturated crosslinking agent. The reactioll prodllct can also be characterized as a network polymer comprising: (a) at least one polyfluorinated resin comprising an acrylate fullctiollality;
and (b) at least one etllylenically unsaturated crosslinking agent. Preferably, abo~lt 0.5 20 wt% of the polyfluorinated resin, and most preferably about 1-10 wt% of the resin, is present in the anti-stick backlayer of the dyesheet. Additionally, preferably about 80-99 wt%, and most preferably about 85-95 wt%, of the ethylenically l~nsaturated crosslinking agent is present in the anti-stick layer.
The therrnal dye transfer sheets of the present invention are very effective because of the use of the particular anti-stick compositions utilized in the dyesheets. The anti-stick layer is especially important in performance and serves to provide heat resistance to protect the heat sensitive carrier substrate and prevent distortion or loss of integrity;

3() lubricity at printing conditions to allow for smooth slippage of the carrier under the 2~r~

printllead; impermeability to prevent dye and/or other material diffusion from the dye layers with subsequent possible alteration of dye layer and/or anti-stick printing performance and contamination of the printhead; and self-cleaning action while printing, preventing debris buildup at the printhead surface and subsequent streaking or other printing defects with possible printhead damage.
The thermal dye transfer materials of the present invention have been found to perform well in the printer and the anti-stick }ayers present in the inventive materials provide excellent barrier properties preventing dye retransfer from typical dye layers under accelerated aging conditions.
The inventive thermal dye transfer materials of the present invention employ anti-stick coatings which can be on the order of only O.l~m in film thickness, thus contributing negligible thermal mass to the donor ribbon and allowing for more efficient utilization of printhead energy with attendant extended printhead ]ife. Additionally, the fluorinated anti-st;ck layer used in the inventive material is srosslinked into the resin lS matrix and thlls, is relatively immobile compared with the anti-stick agents used in conventional systems. Also, the inventive materials contain no potentially corrosive ions as compared to other thermal dye transfer sheets, as disclosed in EPO Publn. No. 314,3a,8.
Finally, the use of particulate anti-blocking agents is optional, and not mandatory, in the present invelltion.
Other aspects and advantages of the present invention are apparellt from the detailecl disclosure7 examples, and claims.

Detailed Description of the Invention The present invention provides a dyesheet for therrnal transfer printing comprising 2S a support having on one side thereof a thermal dye transfer layer and on the other side thereof an anti-stick layer comprising the polymerization reaction product of: (a) at least one polyfluorinated resin comprising an acrylate functionality, and (b) at least one ethylenically unsaturated crosslinking agent. The polymerization reaction of (a) and (b) is typically induced by a free-radical mechanism. The initiator for such a reaction is commonly eiihe3; a thermal or photoinitiator, with the latter preferred.

~5~

Any material can be used as the support for the dye-donor element of the invention provided it is dimensionally stable and can withstand the heat of the thermal printing heads. Such materials include polyesters sueh as poly(ethylene terephthalate~;
polyamides; polycarbonates; glassine paper; condenser paper; cellulose esters such as cellulose acetate; fluorine polymers sueh as polyvinylidene fluoride; polyacetals;
polyolefins such as polystyrene, polyethylene, polypropylene or methylpentane polymers;
and polyimides such as polyimide-amides and polyether imides. The support generally has a thickness of from about 2 to about 30,um. It may also be coated with a priming layer, if desired.
The thermal dye transfer layer of the materials of this invention may be chosen from the many formulations disclosed in the art. Preferred formulations are those making use of so-called "sublimable" dyes. The dyes are eommon dispersed in a polymericbinder. Typical dye classes are anthraquinone, azo, and arninostyryl, but many other dyes are disclosed in the art such as, for example, in U.S. Pat. No. 4,857,503.
1~ The dye layer of the dye-donor element may be coated on the support or printed thereon by a printing technique such as a gravure process.
Preferably, the polyfluorinted resins comprising an acrylate functionality employed in the anti-stick coating layer of the resin invention are selected from:

2~) Rf-X-A and Z-Rf~-Y-A
wherein:
R, is a polyfluorinatecl, saturated, monovalent aliphatic group which is straight, branched, or cyclic;
Rrl is a polyfluorinated, divalent, saturatecl aliphatic group which is straight, branched, or cyclic;
A is an acrylate or methacrylate group;
X and Y are each C, to Cl4 aliphatic connecting groups which may be fluorinated with the proviso that there is an unfluorinated carbon atom connected clirectly to A;

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is selected from CF30-, C2F50-, C4F90-, CF3CF(CF3)0-, CF30CF(CF3)0-, or Y-A, where Y and A are as defined above.
In this context, "aliphatic" or groups may contain other covalently bonded atoms besides carbon. Included are groups where the carbon atoms are interspersed with atoms of one or more of the elements oxygen, nitrogen, and sulfur.
~referably R, is fully fluorinated; however, desired release characteristics can be obtained with hydrogen or chlor~ne atoms present as substituents provided no more than one atom of either is present for every two carbons in the group. Rf preferably contains 6 to 14 carbon atoms and more preferably 8 to 10 carbon atoms.
Preferably R~l comprises highly fluorinated polyethers having units selected from at least one of the groups -CF20-, -CF2CF,0-, -CF2CF2CF20-, and -CF(CF3)CF20-, and may have incorporated therein -CF2CF2CF2CF20-, -CF2CF2-, and -CF2- grollps. Where more than one of the groups -CF20-, -CF2CF20-, -CF2CF2CF20-, and -CF(CF3)CF20-, is selected, then these groups may be randomly distributed.
The connecting group X is preferably chosen from those with the formulae --S2--N--(cH2)b ll 72 --C--1~ (Cl-l2)b an~

C (CH2)c-H

2 ~

and the connecting group Y is preferably chosen from those with the formulae 1l 1 2 --C--N--(CH2)b--, and C--(CH2)c I

wherein:
R2 iS hydrogen, a lower aL~yl of about 1 to 4 carbon atoms ~preferably methyl orS ethyl), or (CH2)d-A where A as is defined above, R3 is hydrogen, CF3, or CF2CI;
b is 2 to 12, except that when R2 is -(CH2)"-A, b is 2 or 3;
d is 2 or 3;
c is 1 to 12.
Preferably A is an ethylenically wnsaturated group selected from the formulae;

O R
--O~ C=CH2 O O
Il 11 O--C--NH--(CH2)~ 0~ C--Cl =CH2 . and O O O
Il 11 11 --O--CNH--Rl--NHCO~CH2)a--O--C--C--C~12 20~6~

wherein:
~ is hydrogen or methyl, a is an integer having a value in the range 2 to 6; and Rl is a divalent aliphatic or cycloaliphatic group having 2 to 14 carbon atoms or an aryl group having 6 to 14 ring carbon atoms.
These fluoroacrylates may be made by the methods disclosed in U.S. Pat. No.

4,383,878.
Preferred ethylenically unsaturated functionality crosslinking agents for inclusion in the anti-stick formulations of this invention are acrylates and methacrylates. Fxamples include compounds with acrylic equivalent weight of about 63 to 400, and preferably about 85 to 300. Such agents are well known and are listed, for example, in U.S. Pat.
Nos. 3,833,384; 3,885~964; and 4,037,021. Preferred compounds are pentaerythrytol tetraacrylate (PETA), hexamethylene diisocyanate trimer (HMDI), an add~lct of H~IDI and PETA, trimethylolpropane propoxylate triacrylate, and hydantoin hexacrylaie. Other 1~ useful compounds are neopentylglycol ethoxylate diacrylate, pentaerythrytol triacrylate, urethane acrylales, polyester acrylates, amine acrylates, acrylated epoxides, and methoxy ether acrylates.
Examples of photopolymerization initiators which are useful in the practice of this invention include the benzoin/acetophenone classes such as benzoin, benzoin all~ylethers, benzil ketals, and dialkoxyacetophenones. A preferred initiator i9 Irgac~lre'rM 500 (Ciba-Geigy) whicll is a 50/50 mixtllre of benzophenone and 1-hydroxy-cyclohexylphenylketone.
Another example is IrgacureTM 907 which is 2-methyl- 1-[~-(methyltllio)pllenyl]-2-morphalinopropanone-1. This initiator may be sensitized, for example, with isopropylthioxanthone. A further example is 1-hyclroxy-1-methylethylphenylketone.
Photoinitiators containing fluorinated aliphatic chains have been found particularly suitable and can provide high curing speeds. It is surmised that the enhanced performance of these compounds is related to their being more compatible with the fluorinated acrylates.
It is also within the scope of the invention tha~ azo and peroxide containing materials can be utilized. Such materials are well known to those slcilled in the art.

~ o ~

Preferably, the fluoroacrylated compound should contain sufficient fluorine so that the combination of fl~lorinated and unfluorinated acrylates contains at least 0.()5% by weight of fluorine. Owing to the limited solubility of the fluoroacry~ates, which is determined by the chemical nature and length of the fluorinated relative to the non-fluorinated group, the fluoroacrylate may phase separate from the matrix acrylate, if employed, after coating.
The ~luoroacrylate, possessing lower surface energy, will segregate toward the coating surface, resulting in a distribution of fluorine more highly concentrated near the surface of the coating. The required weight % of fluorine to achieve functional antistick performance is thus dependent on the chemical nature of the fluorinated acrylate, its solubility and surface energy relative to the cTosslinking rnatrix, and in addition the overall coating weight employed. For example, a longer tail fluoroacrylate will likely be less soluble in common acrylate monomers, and will likely bloom to the coating surface more efficiently than a shorter tail material. Thus, a lower total percent by weight of such a material and consequently, fluorine will be required for functionality relative to the shorter tail material. Further, with increasing coating weight, less percent by weight of the fluoracrylate will be required for functional performance, because the fluoroacrylate tends to concentrate at or near the coating surface. If a long tail fluoroacrylate were employed whicll was insoluble in the matrix monomer, then for increasing coating weight, the thicklless of the resultillg fluoroacrylate at the coating s~lrface woulcl increase 2(~ proportionally, conceivably to an excessive and undesirable level. This segregatioll of flllorine at the coating surface further enhances the imperl~eability an(l thus barrier proper~ies of the antistick.
For coating, the components are dissolved in solvents such as methyl ethyl ketone, and polyfluolinated solvents such as DuPont FreonTMl 13 and 3M FC FluorinertTM
2~ solvents. The longer chain fluoroacrylates have lirnited solubility in either hydrocarbon or ketone solvents and typically the fluorinated solvents must be employed. Tertiary butyl methyl ether was found to solvate many of the perfluoroalkylether acrylates which are relatively insoluble in other non-fluorinated solvents.

2 ~

It has also ~een found that solvent--free forrnulations are possible by emulsification of the fluoroacrylate in the crosslinking acrylate material. This makes it possible to use fluGroacrylates for which no good solvent can be found.
A wide range of surfactant coating aids may be added to the formwlation be~ore S coating. Preferred ones in this invention are fluoroaliphatic polymeric esters.
Antistatic agents may be added to the formulations before coating to alleviate static charge buildup during handling, to improve conveyance properties in the printer, and to reduce collection of dust or other airborne particles which can result in irnage defects. Fluorinated antistatic agents are well known in the art and have advantages in the formulations of this invention.
Curin~ of the coated anti-stick layers may be carried out by methods common in the art, such as using ultraviolet light emitting lamps. Reduction of oxygen content in the curing atmosphere can be advantageous to improve surface and resistance through cure. This may be achieved by flooding the curing environment with nitrogen or other inert gases which displaces oxygen. ~30wever, this requirement can be obviated in some instances by the use of coinitiators, comonomers, and radical scavengers such asfunctional and non-functional amines, e.g., triethanolamine, 2-(dimethylamino)ethyl benzoate, ethyl p-(dimethylamino) benzoate, and amines with acrylate functionality or unsaturation. ~adiation from the lamp may be focused or defocused onto the swrface of 2() the anti-stick layer. Focused radiation is preferable since this reduces sensitivity of the cure to oxygen levels. For temperature sensitive substrates sllch as polyethylene teraphtllalate (P~T), the infra-red radiation content o~ the lamp emissions may need to be absorbed by optical filters or alternatively, the substrate temperatare must be controlled by heat removal.
Although the anti-stick layers used in this invention preferably do not contain particulates for the reasons given earlier in discussing the art, inert particulates may be used in certain circumstances, in particular to reduce the static and dynamic friction, and subsequently the tension required to pull the transfer ribbon through a printing device during operation. The particulates may be inorganic or organic as commonly employed in the art, including talc, zeolite, alumina, alumnosilicate, calcium carbonate, TeflonTM

2 ~ 7 ~ ~

powder, zinc oxide, titanium oxide, magnesillm oxide, silica, gr~phite, and others Mean particle size shou]d preferably be between 0.01ym and 50~1m and more preferably between 0.01,um and 10Llm. Depending on the hydrophilicity of particles employed, buildup of static charge may also be alleviated on the donor film by the particles, acting in the same S fashion as comlT on antistatic agents. The particulates should be present in an amount between 0.1% and about 50~o or more, preferably between 1% and 20% by weight of the total resin present in the anti-stick layer. Dry coating weights of the anti-stick layers are preferably in the range O.lg/m2 to l.Og/m2.

EXAMIPLES.
Chemical abbreviations used in the examples are interpreted in the following Table.
Chemical Abbreviation Description.
Class Abbreviation Descri~on li FIIJorinatecl FPEO (CF2CF2O)~(CF2CH2)yOCOCH=CH2 x=7.5, y=1.4.
A clylates. FPTOC - [(CF2CF20)1n(CF2O)"],~- (CF2CH2)yOCOCH=CH2 m/n~3.28, x=5.8, y=1.5.
FPTHF -(CF2CF2CF2CF20)~-(C3F6CH2)yOCOCH=CH2 x=8.~, y=1.6 2() FPPG -(CF2CF(CF3)O),~-CF2CH(CF3)OCOCI~I=CHI2 x=5.g.
FX-13 C3F,7SO2N(CH2CH3)CH2CH2OCOCl-l=CH2 (3M product) FBEE C4F8OC2F4OCF2CH2OCOCH=CH2 KRYTOX C3F,O(CF(CF3)CF2O)~CF(CF3)CH2OCOCH=CH2 x=10.3.
FOA C7F~scH2ococH=cH2 (3M product) FCY C~F,ICH2OCOCH=CH2 (fluorocyclohexyl) FCYM C~F"CH2OCOCH(CH3)=CH2 (flllorocylohexyl) 3() FC550 CF30(CF2CF20),~CF2CH20COCH2 x=5.8.

20~7 ~4 FPEMO -[(CF2cF2o)m(cF2o)n]~-(cF2cH~)y-(ococH CH2)t m/nzO.8, x~12.6, y~1.95, z~1.95 Ac7ylates PETA pentaerythrytol tetraacrylate PET3A pentaerythrytol triacrylate HMDI hexamethylene diisocyanate trimer ~3 functional isocyanate) HMDITA-7 adduct of pentaerythrytol triac7ylate and singly reacted HMDI with HOCH2CH20COCH=C~2, i.e (HMDI)-PET3A)~-OCH2CH20COCH=CH~
HHA hydantoin hexacrylate (3M product) PhotomerTM 4160 neopentylglycol ethoxylate diacrylate (Henkel) PhotomerTM 4072 trimethylolpropane propoxylate triacrylate (Henkel) nitiato7- IrgacureTM soo solso blend of benzophenone and 1-hydroxy cyclohexylphenylketone (CIBA-GEIGY) Sulf~7Ctant FC-430 fluoroaliphatic polymeric esters (3M product) 2~ FC-43 1 fluoroaliphatic polymeric esters (3M product) Solvents MEIC methyl ethyl ketone FC-86 fluorocarbon (3M FluorinertrM liquid) FreonTM 113 1,1,2 trichloro-1,2,2-trifluoroethane (TF grade, DuPont) Subst)-ates PET poly(ethylene terephthalate) 2~7~

EXAMPLE 1.
Four formulations were made and tested as follows:
Table 1.
Component % of solids for solution #
.

FC-550 8.92 8.95 4.67 4.68 FC-430 0.34 0 0.36 0 PhotomerTM4072 84.74 85.03 88.70 87.01 IrgacureTM 500 6.0 6.02 6.28 6.3 Solutions were prepared with these solids compositions at 8% total solids in FreonTM 113.
Solutions were then applied to a 5.7~m PET substrate used for donor sheets by slot-die coating at dly coating weights of 0.3 and 0.6 g/m2. Dried coatings were cured continuously on the substrate at 20 fpm (~.1 m/min) using a 200 Wlin (80 W/cm) UV
lamp system. A standard 300 dotlinch (11.8 dots/mm) printhead was employed with a backup platen hardness of 55 Shore Gauge A and 1.6 pounds/lineal inch (0.29 k~/cm) engagement pressure. Maximurn temperatures at the printhead in these tests were estimated ~rom pyrometer measurements to approach 300C. All coatings performed well in the printer with smooth passage and quiet operation.

EXAMPLE 2.
All formulations referred to herein are described in Table 2. Coating and curingwas carried out using a RPC W processing unit with nitrogen inerting. This curing unit 2~ contained two medium pressure mercury lamps; for a norninal 300 W/in (120 W/cm) operation each lamp was estimated to emit the following power at the indicated peak wavelengths: ll.lW at 254nm, 10.3W at 313 nm, and 17.5W at 365 nm. Curing was typically carried out at 200W/in (80W/cm) using one or both lamps, with one or two passes through the machine at speeds from 20 ft/min to 5() ft/min (6.1 m/min to 15.25 m/min~ Coatings were made using a ~4 Meyer rod ( 10 ~Jm wet thickness), with one ~ ~ s~

and two passes through the curing unit at 25 ft/min (7.6 m/min). One pass at these conditions yielcled a tota] dosage of roughly 200 mj/cm~ using a Dynachem integrating radiometer (~ = 360 nm +/-25 nm). These cured samples were then aged against actual dye coated layers.
Aging was carried out in dry (50C) and wet (40C, 90% RH) ovens for up to 2 weeks by layering dye and anti-stick coatings face to face under a pressure between 0.1 to 0.2 pounds/inch2 (7 to 14 g/cm2).

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Table 2 Formulation~e2 ID # ComPonents Amt (g) FPEO 1.22 HMDITA-7 1.66 IrgacureTM 500 0.1 FC-430 0.03 MEK 25.43 FreonTM 113 49.73 2 FPEO 1.23 HMDITA-7 2.53 IrgacureTM 500 0.13 FC-430 0.02 MEK 31.9 FreonTM 113 625 3 FPEO 0.65 HMDITA-7 2.57 IrgacureTM 500 0.15 2() FC-430 0.02 MEK 27.6 FreonrM 113 54.4 4 (HMDI)3(LTM)~PETA2.11 IrgacureTM S00 O.OS
FC-430 0.02 FC-86 52.84 2~Y~l ID # Components Arnt S FC-550 1.25 HMDITA-7 2.52 IrgacureTM 500 O. l O
FC-430 0.02 MEK 32.97 FreonTM 113 62.6 6 HMDITA-7 6.64 FX-13 2.02 IrgacureTM 500 0.13 FC-430 0.02 7 FPPG 0.5 HMDITA-7 1 .5 Irgac~lreTM 500 0.04 FC-430 0.04 MEK 17.45 2(~ FreonrM 113 33.68 HMDITA-7 1.52 lrgac~lreTM 500 0.05 FC-430 0.015 MEK 17.78 FreonTM 113 34 21~7~1 ID # 5~ a~
9 FPTOC 0.51 HMDITA-7 1.51 IrgacurerM 500 0.04 FC-430 0.01 MEK 17.40 FreonTM 113 33.50 (HMDI)3-(LTM)2-PETA1.01 IrgacureTM 500 0.03 FreonTM 113 25.25 11 FOA 1.0 HMDITA-7 4.0 IrgacureTM 500 0.07 FC-430 0.02 MEK 41.41 FreonrM 113 83.76 12 (HMDI)3-(LTM)3 2.04 IrgacllreTM 500 0.03 FC-430 0.01 FreOllTM 113 51.9 2S 13 FCY 0.27 HMDITA-7 1.08 IrgacureTM 500 0.04 FC-430 0.01 MEK 11.6 Freonr~ 113 24.6 .f~. ~

ID ~ ComPonents Amt ( 14 (HMDI)3-(LTM)2-PETA 1.5 IrgacureTM 500 0.05 PC-a,30 0.01 MEK 37.8 .
FCYM 0.51 HMDITA-7 2.04 IrgacureTM 500 0.05 FC-430 0.01 MEK 21. 1 FreonTM 113 44.5 16 (HMDI)3-(LTM)~-PETA 2.08 IrgacureTM S00 0.02 FC-430 0.01 FreonTM 113 527 ~0 17 FC-550 0.26 HMDITA-'7 1.08 IrgacureTM 500 0.05 FC-430 0.01 MEK 10.9 FreonrM 113 23.10 18 (EIMDI)3-LTM-PETAl.Sl IrgacureTM 500 0 04 FC-430 0.01 MEK 37.64 ~1 ID # Com~onents Amt 19 FC-550 0.25 HMDITA-7 4.77 IrgacureTM 500 0.06 FC-430 0.01 MEK 42.0 FreonTM 113 84.50 (HMDI)3-(C7Fl5)-(PETA)2 1.5 IrgacureTM 500 0.04 FC-430 0.01 MEK 38.1 21 FPEO 0.12 HMDITA-7 2.37 IrgacureTM 500 0.04 FC-430 0.01 MEK 20.70 Freon'M 113 41.90 2~
22 FC-55V 0.30 HHA 1.21 IrgacureTM 500 .04 FC-430 0.01 ~5 MEK 12.36 FreonTM 113 25.4 2~7~

ID # Components Amt 23 FC-550 0.1~
PhotorneTTM 4160 1.72 kgacureTM 5~0 0.04 S FC-430 0.01 FreonTM 113 48.3 24 FPEO 0.30 HHA 1.21 IrgacureTM S00 0.04 FC-430 0.01 MEK 12.4 FreonTM 113 25.3 FC-550 0.26 PhotomerTM 4072 2.47 IrgacureTM 500 0.08 FC-430 O.0i FreonTM 1 1 3 70.1 26 FPEO 0.4 PET3A 1.22 Irg~cure~ M 500 0.04 FC-430 0.01 FI'eOnTM 11 3 34 27 FPEMO 0.5 PETA 0.04 MEK 12.9 2~7~

Donor dve layer formulations used in these examples DYE COLOR.
Yellow Components % of solids PTS #2 11.9 Dye A 11.9 Nippon Kayaku MQ-452 23.7 Geon 178 PVC 39.5 Vitel PE 200 1.98 Troysol CD1 Dispersant 11.1 n 100 Ma~enta ComPonents of solids AQ-l 23.9 Mitsibushi Kasei HSR-31 23.9 Geon 178 PVC 27.9 Vitel PE200 1.99 ODA/AA Copolymer 11.2 Troysol CD1 11.2 5~ Collle~ ! Of solids Foron Brilliant Blue 23.4 Dye B 23.4 Geon 178 PVC 31.2 ODA/AA Copolymer 6.54 Vitel PE 200 3.12 UVINUL N539 (BASF) 12.5 1~0 ~13 5 ~ r~ 4 ~

2~
The dyes in these fcrmulations were as follows:
Ye]low TPS#2 N-(1-Anthraquinonyl)-2-ethylhexamide Dye A N-(4-Hydroxyanthraquinon- 1 -yl)-p-toluenesulfonamide Nippon Kayaku MQ-452 1-Butyl-3-cyano-4-methyl-5-(3,4-clichloroazobenzene--6-hydroxypyrid-2-one MaLTenta Mitsibushi Kasei HSR-31 p-tricyanovinyl-N-butyl-N-(2-phenylethyl)-aniline AQ-1 N-(4-Amino-3-rnethoxyanthraquinon- 1 -yl)-p-toluenesulfonamide Cyan Dye B 1 ,4-bis-(1 -Methylhexylamino)-5,8-dihydroxyanthraquinone Foron Brilliant Blue Propanedinitrile [2-[[4-(dihexylamino)-2-methylphenyl]
methylene]benzo[b]thien-3-(2H-ylidene)]-5,5-dioxide RES ULTS
Results are shown in Table 3, corresponding to two-pass cures at app:roximately 400 m j/clll2 close as measured by a radiometer integrating between 330 ancl 40() nm. All 2() mLlterials provided generally quiet printer operation, A stalldar(l 300 dot/inch (l],8 dots/mlll) plintheacl was ernployed with a backup platen hat(lness of 55 Shore Gauge A
ancl 1.6 pounds/lineal inch (0.29 kg/cm) engagement pressure. Maximum temperatures at the printhead in these tests were estimated from pyrometer measurements to approach 300C Printer noise as a result of the "stick-slip" phenomenon was noted at specified 2~ voltages as indicated in Table 3.

2~7~

Table 3. Perfomlance of antistick layers a~ed a~ainst dYe donor layer.
Formula #Max volts Days Agecl before Observable without Dye Transfer for noise. Wet Oven Dry Oven (40C 90%F~H) (50C) YM C YM C
17.5 3 * 7 7 * *
2 20 7 * * * * 3 3 20 7 4 7 4 * 4 lû 4 20 1 1 1 1 1 1 7 7 7 3 * 1 6 16.5 - - - - - -9 17.5 - - - - -1 1 17.5 12 20 1 * 1 1 1 1 13 20 - - - 1 *
2() 1 4 20 - - - - - -IS 20 * ~ I l * I
16 2~) 1 1 1 1 1 1 2i 19 20 - - - - -- - - - - -21 20 * * * * * 7 2~7~

* * * 1 3 7 26 20 * * 7 1 * *

"-" indicates data not taken;
"*" indicates better than one week without trans~er.
EXAMPLE 3.
This example illustrates the effect of 1) fluoroacrylate level, and 2) coating weight on surface cure and resultant unreacted fluoroacrylate which can be of concern if the backcoated material is stored in wound-up form before coating the dye layers on the other surfaces.
Coatings from Example 1 were prepared as described and wound up on cylindrical cores for storage. Samples were removed from these cores and coated with the cyan li formulation described in Example 2, at 4% solids in a 20%/35~o/45% tetrahyclrofuran, methyl-ethyl ketone/cyclohexanone solvent system. Coatings were applied to the opposite side of the antistick after it was in roll form. A #8 wire wound Meyer rod was used to yield dry coating weights near 1 g/m2. Contamination of the face side was indicated by poor wettability of the cyan coating after application, with various degrees of wetting behavior being observed depes~ding on the fiuoroacrylate coating parameters, Forexample, severe dewetting implies extensive beading up of the coating, mo(lelate implies that clewetting is not extensive but scattered, and slight implies that no beading of solution is observed, although nonllniforrllities in the coating may be observable due to poor wetting. Results were as follows:
De~ree of_dewettin~ for antisticlc coating weight of:
Antistick solution # 0.3 ~/m2 0.6 ~/m2 severe severe 3 slight moderate 4 slight severe 2 ~

Results indicate that surface transferrable unreacted fluoroacrylate is reduced at the lower coating weight and with the reduced fluoroacrylate levels for the 0.3 g/m2 antistick coating weight.

E~fAMPLE 4.
This example illus~rates the effect of the fluoroacrylate tail length on printer performance.
Two fluoroacrylates were used: FBEE and KRYTOX. These two compounds were prepared at varying levels of % of solids in the following formulation, keeping the ratio of fluoroacrylate to FC-430 constant at 26.24, and the ratio of Photomer 4072 toIrgacureTM 500 constant at 14.12.

Table 4.
Component % of solids for formulation #

FBEE 8.93 20 30 40 50 KRYTOX - - - - - 0.5 1 2 5 8.93 FC-430 0.34 0.762 1.14 1.52 1.91 0.019 0.038 0.076 0.19 0.34 Photomer 4072 84.7 74 64.3 54.6 44.9 92.9 92.4 9l.5 88.5 84.7 IrgacllreTM 500 6.0 5.2 4.6 3.87 3.18 6.58 6.54 6.48 6.27 6.0 Solutions were prepared based on these solids contents at 3% solids in FreonTM 113 and coaLed on 5.71,1m PET with a #4 wire wound rod yielding a dry coating weight of about 0.5 g/m2. Curing was carried out at 30 fpm (9.15 m/min) with two 200 W/inch (80 W/cm) lamps giving roughly 200 mj/cm2 dose.

2~67l~1 Additional samples of -formulations 1 and 2 above were coated with a #8 Meyer rod, yielding a c()ating weight of roughly 1 g/m2. These samples and samples from formulation 3 were exposed to a double cure of 400 mj/cm2 (2 passes through curing unit). Printer results are presented in Table 5 below.
', The results clearly indicate the importance of tail length in providing sufficient lubricity to the antistick, with a lesser percentage of solids being required of the longer tail fluoroacrylate (F-acrylate) in order to achieve satisfactory printer performance.

Table 5.
~ Solution # o F-acrylate in solids Cure (mi/cm2) Wire Rod # Printer Test FBEE 1 8.92 200 4 Fail " ~ 400 " " " 20G 8 "
" " 400 "
1C, " 2 20 200 4 Fail " " " 400 4 "
" " " 200 8 "
" ~ 400 " 3 30 200 4 "
" " " 400 " "
" ~ 200 " " " 400 " "
" 4 40 200 ~I "
" 5 50 200 " Pass Krytox 6 0.5 200 4 Fail " 7 1 " " Pass " 8 2 " " "
" 9 5 " " "
~,0 " 10 8.92 " " "

2 ~

EXA~IPLE 5.
In an attempt to further improve surface cure, a soluble fluorinated photoinitiator was tested. This initiator was found to be soluble in the FC550 acrylate. The initiator was synthesized by combination of fluorinated polypropylene glycol acylfluoride (FPPG) and the Merck initiator Darocure 2959. Its chemical formula, confirmed by ~MR, is asfollows:

CF3(CF2)3O(CFCF2O)2 l F--C--O--(CH~2--O--~ C--C--OH

This will be referred to as FD2959. Its photoachvity was studied in a UV visiblespectrophotometer, and compared to absorbance of the original Darocure 2959 initiator.
The characteristic absorbance is preserved in the 25()-400 nm range. Photoactivity of this compound is further confinned by differential photocalorimetry (DPC) studies. The following table illushrates the dramatic effect on the enthalpy of reaction and overall reaction efficiency 30% increase), by adding FD2959 at a level of 1% relative to the FC550 acrylate, where the conhrol formulation is identical to Solution $~1, in Example 1.

DPC results of control formulation and control plus FD2959 at 1% of the FC550 level.

Formulatio!l Enthalpy of Reacti Control 211 Conhol ~ FD2959 266 Tests were then carried out using this novel initiator with the control formulation to determine its effect on surface cure and reduction of contamination. The controlformulatioll was prepared along with three additional formulations having FD2959 at 1%, 5% and 10% of FC-550. This was then coated at 3% solids with a #4 Meyer rod, yielding dry coating weights of about 0.5 g/m~. The control formulation was cured at 2 ~ 3 three total dosages of 100, 150, and 300 mj/cm2 as measured by a Dynachem integrating radiometer. The other three formulations with FD2959 were curecl ~t a single dose of 100 mj/cm2 (30 fpm { 9.15 m/min } with single 200 W/in ~ 80 W/cm } lamp). These coated antisticks were then aged against clean Teijin at 50C and roughly 0.2 psi ~0.014 kg/cm2) for one hour. The aged Teijin was then coated with the same cyan formulation as described in the previous example, by handspread, and checked for dewetting. Results from this study are presented in the following table.

The effect of addition of FD2959 at only 1% of the FC-550 is dramatic in reducing contamination. Further addition appears to worsen contamination, although at a reduced level compared to the control. Thus, the effect of a soluble photinitiator is apparently to improve surface cure and reduce transferrable unreacted fluoro-acrylate.

Contamillatioll study with control formulation and added FD2959.
Table 6.
Formulatiolll:)ose (mj/cm~) Dewettin,~
Control 100 Severe Contlol 150 Severe Control 300 Severe 2() Control + 1% FD2959 lOO Sligllt Control -~ 5'~ FD2959 100 Moderale " -~ 10% FD2959 100 Moderate 2S Also interesting to note from the Table 6 is that increased cure did not reduce apparent dewetting for the control formulation, indicatir,g that the photoinitiator is exhausted predominantly in the matrix acrylate phase. This is confirmed in other DPS st-dies showing virt~lally no solubilization of the Irgacure 500 initiator in FC-550, and stresses the need for attention to the solubility of the photoinitiator.
3() 2~7~

_XAMPLE 6.
This example demonstrates the effect of particulate additions to the formulations.
Hydrophobic fumed silica R972 from Degussa Corporation having a primary p~rt;cle si~e of 0.016ym, was added to the formulation as described below at levels of 1, 5, and 10%
of total solids.

Table 7.

% OF SOLIDS
1~ Component Control #1 ~2 , #3 FC550 9.30 9.21 8.84 8.37 P4072 87.6086.72 83.22 7~.84 IRG 500 2.80 2.77 2.66 2.52 FC430 0.30 0.30 0.29 0.27 R972 SILICA 0.00 1.00 5.00 10.00 PHR _ 2() Component Control #1 #2 #3 FC550 10.6210.62 10.62 10.62 P~072 100.00100.00 100.00 100,00 IRG 500 3.20 3.20 3.20 3.20 FC430 0.34 0.34 0.34 0.34 R972 SILICA 0.00 l.lS 6.02 1~.. 68 3~
Solutions of these formulations were prepared at 3% solids in FreonrM 113, and coated using a #4 wire wound rod, yielding coatings with roughly 0 5 g/m2 coating weight.
Samples were cured with a single RPC UV lamp at 200 W/inch (80 W/cm) and at speeds of 20 to 50 fpm (6.1 m/min to 15.25 m/min), corresponding to 140 rnj/cm2 to 60 mj/cm2 dosage as measured by the Dynachem in~egrating radiometer. Samples of the control formulation, and that formulation with 5% and 10% levels of silica passed quietly through 2 ~ Y7 ~ ~

the printer with head temperatu~es near 270C. The case at l~/o si]ica resulted in stick-slip behavior in the printheacl, detectable by chatter noise. Lubricity is improvecl at the higher silica loadings where interfacial contact is reduced, but reduced at the 1% leve].

This example will illustrate the preparation of fluoroacrylated compositions in a solventless fashion with coating and curing to obtain functional antistick materials. The following formulation was prepared.
Table 8 1() Component PHR% of Solids FC-550 10 8.55 Photomer 4072100 85.47 IrgacurerM500 7 5.98 lO0 A solution of the matri,x acrylte Photomer 4072 and the photoinitiator :IrgacurerM 500 was first prep~red in proportions described above. Addition of the fluoro-acrylate was theIl made, and the entire solution was then hand shaken to moderately disperse the fluoroacrylate, which readily emulsifies once added thereafter, a Branson Moclel 350 Sonifier was emp]oyed hclving a 20 KHZ frequency operation, and using amplitude setting of 5 at 50% cycle. 'I'he ultrasollic probe was immersed in the clispersion and allowed to sonicate for 5 millutes to achieve more complete clispersion of the fl-loroacrylate in the matrix phase Droplet sizes resulting from similar sonication proced-lres were measured in the 50-lOOmm range, and the resulting emulsion was observed to remain stable for several days when left standing at room temperature. The emulsion was then bladecoated to four coating weights measured at 0.15, 0.24, 0.52, and 0.93 glm~. Coatings were cured in an R3'C unit with two 200 Wlin lamps at 50 fpm yielding a dosage near 100 mj/cm~ for a single pass through the UV curing ~lnit. All coatings performecl well 2~7~

in printer tests with quiet and smooth operation, with head temperatures approaching 300C, and operating parameters as described in Example 1.

Table 9 Coating weight emulsionDosage Printer (glm2)(mj/cm2)Results 0.93 100 Pass 0.52 100 Pass 1~ 0.52 200 Pass 0.24 200 Pass O.lS 200 Pass Reasonable modifications and variations are possible from the foregoing disclosure without departing from either the spirit or scope of the present invention as defined by the claims.

Claims (9)

1. A thermal transfer dyesheet comprising a support having on one side thereof athermal dye transfer layer and on the other side thereof an anti-stick layer comprising the reaction product of:
a) at least one polyfluorinated resin comprising an acrylate functionality; and b) at least one ethylenically unsaturated crosslinking agent.

2. A thermal transfer dyesheet as recited in claim 1 wherein said antistick layer further comprises a coating-aid surfactant.

3. A thermal transfer dyesheet as recited in claim 1 wherein said antistick layer further comprises inert particulate material of particle size in the range 0.01,µm to 10µm.

4. A thermal transfer dyesheet as recited in claim 1 wherein said polyfluorinated resin is selected from the group consisting of polyfluorinated alkyl acrylates and methacrylates, and poly(fluorooxyalkalene)acrylates and methacrylates.

5. A thermal transfer dyesheet as recited in claim 1 wherein said polyfluorinated resin is selected from the group consisting of:
R1-X-A and Z-Rf1-Y-A
wherein:
Rf is a polyfluorinated, saturated monovalent, aliphatic radical;
Rf1 is a polyfluorinated, divalent saturated, aliphatic radical;
A is an acrylate or methacrylate radical;
X and Y are each C1 to C14 aliphatic connecting groups which may be fluorinated with the proviso that there is an unfluorinated carbon atom attacheddirectly to A; and Z is selected from the group consisting of CF3O-, C2F5O-, C4F9O-, CF3CF(CF3)O-, and -Y-A wherein Y and A are each as defined above.

6. A thermal transfer dyesheet material as recited in claim 5 wherein:
Rf contains from 6 to 14 carbon atoms and is perfluorinated; or Rf1 is selected from the group consisting of -CF2O-, -CF2CF2O-, -CF2CF2CF2O-, and -CF(CF3)CF20-;
X is chosen from the group consisting of:
, , and Y is chosen from the group consisting of:

, and wherein:

R2 is hydrogen, a lower alkyl of about 1 to 4 carbon atoms, or -(CH2)d-A where R3 is hydrogen, CF3, or CF2Cl;
d is 2 or 3, c is 1 to12; and A is selected from the group consisting of:
, , and wherein:
R is hydrogen or methyl, a is an integer having a value in the range 2 to 6, and R1 is a divalent aliphatic or cycloaliphatic group having 2 to 14 carbon atoms or an aryl group having 6 to 14 carbon atoms.

7. A thermal transfer dyesheet as recited in claim 1 wherein said crosslinking agent has an acrylic equivalent weight in the range 63 to 400.

8 A thermal transfer dyesheet as recited in claim 1 wherein said crosslinking agent is selected from the group consisting of pentaerythrytol tetraacrylate; hexamethylene diisocyanate trimer; an adduct of hexamethylene diisocyanate trimer and pentaerythrytol;
hydantoin hexacrylate; neopentylglycol ethoxylate diacrylate; trimethylolpropanepropoxylate triacrylate; and pentaeryihrytol triacrylate.

9. A thermal transfer dyesheet as recited in claim 1 wherein said anti-stick layer has a dry coating weight in the range 0.1g/m2 to 1.0 g/m2.