Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
  • B41M5/42—Intermediate, backcoat, or covering layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
  • B41M5/46—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography characterised by the light-to-heat converting means; characterised by the heat or radiation filtering or absorbing means or layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/02—Dye diffusion thermal transfer printing (D2T2)
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/06—Printing methods or features related to printing methods; Location or type of the layers relating to melt (thermal) mass transfer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/08—Ablative thermal transfer, i.e. the exposed transfer medium is propelled from the donor to a receptor by generation of a gas
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/12—Preparation of material for subsequent imaging, e.g. corona treatment, simultaneous coating, pre-treatments
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/30—Thermal donors, e.g. thermal ribbons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/38—Intermediate layers; Layers between substrate and imaging layer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/382—Contact thermal transfer or sublimation processes
  • B41M5/385—Contact thermal transfer or sublimation processes characterised by the transferable dyes or pigments
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
  • B41M5/41—Base layers supports or substrates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
  • B41M5/42—Intermediate, backcoat, or covering layers
  • B41M5/44—Intermediate, backcoat, or covering layers characterised by the macromolecular compounds

Definitions

• This invention pertains to a donor element for use with a receiver element in an imageable assemblage for radiation-induced transfer of material from the donor element to the receiver element.
• Donor elements for use with a receiver element in an imageable assemblage for radiation-induced transfer of material from the donor element to the receiver element typically include multiple layers.
• the layers can include but are not limited to a support layer, a transfer-assist or light-to-heat conversion (LTHC) layer, and a transfer layer.
• LTHC transfer-assist or light-to-heat conversion
• a support layer such as a 50 ⁇ m polyethylene terephthalate film is sequentially coated with a LTHC layer precursor, the precursor is converted to a final LTHC layer by drying, and subsequently a transfer layer precursor is coated above the LTHC layer opposite the support layer and converted to a transfer layer by drying.
• thermal transfer donor elements and improvements in their use with receiver elements in an imageable assemblage, in order to improve at least one of thermal transfer efficiency, independence of thermal transfer efficiency from any variation 5 of heating, independence of thermal transfer efficiency from any variation of environmental conditions such as humidity and temperature, completeness of mass transfer, freedom from unintended mass transfer, clean separation of mass transferred and unimaged regions of the donor, and smoothness of the surface and edges of mass transferred material.
• the ejection layer can have additives, as long as they do not interfere with the essential function of the layer.
• additives include coating aids, flow additives, slip agents, antihalation agents, antistatic agents, surfactants, and others which are known to be
• the invention provides a donor element useful in an assemblage for imaging by exposure to radiation.
• the invention provides a donor element for use in a radiation-induced thermal transfer 25 process comprising: a substrate; a transfer-assist layer disposed adjacent the substrate comprising one or more water-soluble or water-dispersible radiation absorbing compound(s); and a transfer layer disposed adjacent the transfer-assist layer opposite the substrate, at least a portion of the transfer layer capable of being image-wise transferred from the donor
• Figure 1 is a schematic cross-section of an imageable assemblage of a donor element adjacent a receiver element being imaged by radiation.
• pattern-wise or “image-wise” from donor sheets to receptor substrates
• image-wise selective thermal transfer of materials such as inks (including conductive inks) may be used in the printing of graphics io and circuitry; in photographic applications; and in applications currently served by ink-jet technology.
• thermal transfer may be utilised to form elements useful in electronic displays and other devices.
• Colour filters as components in a liquid crystal display (LCD) are of particular interest.
• the colour filter is a thin ink layer which controls the colour of a pixel in the LCD.
• a colour LCD must have at least three subpixels with red, green and blue colour filters to create each colour pixel.
• the substrate typically glass
• the photoactive ink which is then dried, exposed, washed and then dried again. This procedure is repeated for each pigment. It would be desirable to reduce the number of process steps for purposes of economy IH" Li: ⁇ fficW&$MM ' W ⁇ ffl ⁇ i ⁇ 6 ⁇ hcrease manufacturing flexibility.
• the present invention considers radiation-induced thermal imaging as an alternative and simpler manufacturing process. Radiation-induced thermal transfer imaging for the manufacture of colour filters is also addressed in US- 5 5521035.
• thermal transfer donor elements include US-6689538, US-6645681 , US-6482564, US-6461775, US-6358664, US- 6242152, US-6051318, US-5453326, US-5387496 and US-5350732, and known coated support films are disclosed in US-5882800, US-5453326, US-4695288 and US-4737486.
• inks are transferred from a donor sheet (typically comprising a polymeric support) to a receptor substrate (typically glass) by the application of heat in loci corresponding to the desired pattern or image.
• the donor sheet is exposed to electromagnetic radiation at one or more wavelengths (typically infrared radiation, usually
• the donor element can be exposed to the imaging radiation through the donor sheet.
• the transfer of material can occur via a variety of
• the term "light-to-heat converter” refers to a compound which absorbs the radiation utilised in the thermal transfer process to induce the transfer of material(s) from a donor sheet to a receptor sheet, and which then
• imaging can be effected via gap transfer in which the receptor and ink-coated * ' ' 1L:: doii ' oVsleefe by an ink-impermeable mask (also known as a black matrix) which masks specific areas of the receiver sheet (as shown in Figure 2).
• an ink-impermeable mask also known as a black matrix
• the transfer of some materials can be problematic. It is desirable to 5 effect complete transfer of the ink, i.e. 100% transfer or as close as possible thereto, with no concomitant thermal degradation of the materials transferred. It is also desirable that the variability in the amount of ink transferred be very low. In other words, a system in which 95% of the ink is consistently transferred with a variability of ⁇ 0.5% is preferable to a io system in which the amount of ink transferred varies between, for example, 97 and 100%. In addition, the resolution of the transferred image or pattern should be high with good line edge quality (i.e. smooth and sharp image edges). In order to promote good transfer, one or more additional layer(s) can be deposited on the donor sheet substrate prior to
• the amount of functional 25 component(s) incorporated in the transfer-assist layer must exceed a pre ⁇ determined minimum threshold level, the precise level being determined by the identity of the functional component, the identity of the transfer layer, and the thermal transfer method utilised.
• the materials in the transfer layer should be stable to the heat experienced during the imaging
• the amount, identity and location of the radiation converter should be suitable to meter the correct amount of heat to the transfer layer in order to avoid degradation of the components thereof. For this reason, there is normally also a maximum threshold limit for the amount of radiation which should be absorbed by the transfer-assist layer, if too FMl ,, ;. ⁇ iiucliVatiyfen '' ig"yil ⁇ l ⁇ yyd and converted to heat by the radiation absorber in the transfer-assist layer, then too much heat energy can be transmitted to the materials of the transfer layer nearest the transfer-assist layer, which can lead to degradation and decomposition thereof.
• a radiation absorber is also present in the transfer layer itself, which ensures the release of heat energy throughout the whole thickness of the transfer layer.
• a proportion of the radiation normally passes through the transfer-assist layer to the transfer layer itself to assist in the thermal transfer.
• the transfer-assist layer therefore functions not io only to transmit heat-energy to the transfer layer, but also to shield the transfer layer from an excess of heat energy which would otherwise be experienced if all the radiation absorber were present in the transfer layer.
• irradiation induces adhesive failure at the interlayer boundary of the transfer layer and the transfer-assist layer, which would
• the transfer layer 2 o assist layer be transferred to the receptor substrate along with the transfer layer, which can improve the flow and adhesion of the transfer layer to the receptor surface and lead to a smooth image surface on the receptor. It is important that the image transferred to the receptor substrate should have a smooth surface to ensure that any subsequently applied layers (for 25 instance indium tin oxide layers) are themselves smooth and defect-free. However, the transfer of certain other components of the transfer-assist layer to the receptor surface can be problematic and should be avoided.
• One such component is carbon black. Carbon black is typically used in conventional transfer-assist layers as a radiation-absorber to convert
• Donor elements having a substrate and a functional transfer-assist coating comprising a radiation-absorber are known in the art. These prior art donor elements typically utilise an organic material as the radiation-absorber, IH' ll»: in ⁇ re ! q#e !i the '' solvents to apply the coating onto the substrate. These organic solvents can be environmentally toxic and costly to use and dispose of. It is an object of this invention to provide alternative elements and supports comprising a substrate or polymeric substrate and 5 radiation-absorbing transfer-assist coating, particularly donor elements and supports which are more economic and less environmentally harmful to produce, and a method for their production.
• donor element comprises a donor support and a transfer layer.
• the term “radiation” refers to electromagnetic radiation, and particularly to the microwave, infrared, visible and ultraviolet regions thereof, and particularly the infrared, visible and ultraviolet regions thereof.
• the term “radiation” preferably refers to infrared radiation, i.e. the wavelength range from 0.75 ⁇ m to 1000 ⁇ m, and particularly to near-
• the imaging radiation can be provided by any suitable radiation source,
• Infrared lasers are a particularly suitable source for providing image-wise light energy.
• the imaging light is provided by one or more diode lasers.
• a donor element for a radiation-induced thermal transfer imaging process comprising a substrate or polymeric substrate and a transfer-assist coating layer derived from an aqueous composition comprising one or more water- soluble or water-dispersible radiation-absorbing compound(s).
• the aqueous composition further comprises one or more water-soluble or water-dispersible polymeric binder(s).
• the composite film also comprises one or more humectant(s), which may be, and preferably is/are, disposed in the transfer-assist layer.
• an aqueous transfer-assist coating composition comprising one P I , . , :: drmWe ⁇ ite ⁇ seSlUli'iycl ⁇ bter-dispersible radiation-absorbing compound(s), optionally one or more water-soluble or water-dispersible polymeric binder(s), and optionally one or more humectant(s).
• a method of manufacture of a composite film suitable for use as a donor support in a radiation-induced thermal transfer imaging process comprising a substrate or polymeric substrate and a transfer-assist coating, said transfer-assist coating comprising one or more io water-soluble or water-dispersible radiation-absorbing compound(s) and optionally one or more water-soluble or water-dispersible polymeric binder(s), said process comprising the steps of:
• the process for coating the transfer-assist composition may be 25 conducted either in-line or off-line.
• the application of the transfer-assist layer to the substrate or polymeric substrate is conducted according to the present invention in an "in-line” process, i.e. wherein the coating step is effected during film manufacture.
• an "in-line” coating process refers to a process wherein coating step (d) is 30 either effected between steps (a) and (b); or between the two stretching steps (b) and (c) of a biaxial stretching process; or between steps (c) and (e) in the case of a biaxially stretched film or between steps (b) and (e) in the case of a monoaxially stretched film; or between steps (e) and (f).
• an "in-line” coating process is one in which the coating step (d) »" ' is ⁇ dMdi&ea' p ⁇ iorws ⁇ p ' tc).
• an "off-line” coating process is one in which the coating step is distinct from, and effected after, the process of film manufacture. Thus, an "off-line” coating step is conducted after step (f).
• An in-line coating process has advantages of economy and efficiency over the prior art processes in which the coating step could typically only be conducted after the manufacture of the substrate or polymeric substrate has been completed, i.e. in an "off-line” manufacturing process, because organic solvents require inconvenient and costly drying io procedures.
• an in-line coating process can surprisingly provide superior adhesion between the substrate layer and the coated layer, and superior imaging performance. While in-line coating methods are desirable from an economy and efficiency perspective, there are nevertheless inherent limitations to this coating technique. The use of organic solvents
• the range of dry coating thicknesses attainable by an in-line solution coating technique is from about 10nm to about 2000nm. Thicknesses lower than about 10nm tend to lose their desired functionality and/or continuity; while thicknesses higher than about 2000nm are
• the viscosity of the coating composition is typically be in the range of 1 to IOOPas for gravure-type coating methods, but can be greater than IOOPas for other
• the functional components are compatible with each other to allow the formulation of a coating composition suitable for an in-line coating technique without particle flocculation, aggregation or crystallisation. Accordingly, there are inherent limitations on the amount of functional component(s) that can be J " ⁇ • ⁇ • ⁇ layer applied using an in-line coating technique. However, the transfer-assist coating must contain an amount of radiation-absorber which exceeds a minimum threshold level, as noted hereinabove. There is therefore a trade-off between "in-line coatability" on 5 the one hand and thermal transfer performance on the other.
• the aqueous coating composition comprise a sufficient amount of radiation-absorber to exhibit adequate performance (i.e. exceeding a minimum threshold level of radiation absorption) as a o transfer-assist layer in a thermal transfer process while simultaneously allowing the composition to be applied to a substrate via an in-line coating technique, particularly wherein the functional components of the coating composition are thermally stable during film manufacture and capable of forming an in-line coatable composition.
• a composite film as defined herein comprising a substrate or polymeric substrate and a transfer-assist coating layer derived from an aqueous composition comprising one or more water- soluble or water-dispersible radiation-absorbing compound(s) and o optionally one or more water-soluble or water-dispersible polymeric binder(s), as a donor support in a radiation-induced thermal transfer imaging process, particularly for the purpose of improving one or more characteristics of the donor support in said imaging process as defined herein.
• aqueous composition refers to a composition in which the aqueous solvent is a single phase at ambient temperatures (i.e.
• the co-solvent is preferably selected from a low to medium molecular weight (i.e. no more than about 300) branched or unbranched aliphatic alcohol (including diols and polyols), for instance C2-C6 aliphatic alcohols such as isopropanol.
• a ii" ' " IL: ⁇ pi ' dyi ! ! ⁇ titJeeius ⁇ sB ⁇ fi r ⁇ i'icy m position contains about 85% of the aqueous solvent by weight of the total weight of the coating composition.
• an aqueous coating composition comprising one or more water-soluble or water-dispersible radiation- 5 absorbing compound(s), and optionally one or more water-soluble or water-dispersible polymeric binder(s), and optionally one or more humectant(s), to provide a transfer-assist layer in a donor support suitable for use in a radiation-induced thermal transfer imaging process, particularly for the purpose of improving the characteristics of a donor io support in a radiation-induced thermal transfer imaging process as defined herein.
• the substrate or polymeric substrate of the composite film is a self- supporting film or sheet by which is meant a film or sheet capable of
• the substrate may be formed from any suitable film-forming polymer, including polyolefin (such as polyethylene and polypropylene), polycarbonate, polyamide (including nylon), PVC and polyester.
• polyolefin such as polyethylene and polypropylene
• polycarbonate such as polyethylene and polypropylene
• polyamide including nylon
• PVC polyvinyl chloride
• polyester in a preferred embodiment, the substrate is polyester, and particularly a synthetic linear polyester.
• the synthetic linear polyesters useful as the substrate may be obtained by condensing one or more dicarboxylic acids or their lower alkyl (up to 6 carbon atoms) diesters, eg terephthalic acid, isophthalic acid, phthalic acid, 2,5-, 2,6- or 2,7-naphthalenedicarboxylic acid, succinic acid, sebacic acid, adipic acid, azelaic acid, 4,4'-diphenyldicarboxylic acid,
• dicarboxylic acids or their lower alkyl (up to 6 carbon atoms) diesters eg terephthalic acid, isophthalic acid, phthalic acid, 2,5-, 2,6- or 2,7-naphthalenedicarboxylic acid, succinic acid, sebacic acid, adipic acid, azelaic acid, 4,4'-diphenyldicarboxylic acid,
• hexahydro-terephthalic acid or 1 ,2-bis-p-carboxyphenoxyethane (optionally with a monocarboxylic acid, such as pivalic acid) with one or more glycols, particularly an aliphatic or cycloaliphatic glycol, e.g. ethylene glycol, 1 ,3-propanediol, 1 ,4-butanediol, neopentyl glycol and 1 ,4- cyclohexanedimethanol.
• An aromatic dicarboxylic acid is preferred.
• Polyesters or copolyesters containing units derived from hydroxycarboxylic acid monomers such as ⁇ - hydroxyalkanoic acids (typically C 3 -Ci 2 ) such as hydroxypropionic acid, hydroxy butyric acid, p-hydroxybenzoic acid, m-hydroxybenzoic acid, or 2- hydroxynaphthalene-6-carboxylic acid, may also be used.
• IP lJ l , ⁇ i-fnP M - the polyester is selected from polyethylene terephthalate and polyethylene naphthalate. Polyethylene terephthalate (PET) is particularly preferred.
• the substrate may comprise one or more discrete layers of the 5 above film-forming materials.
• the polymeric materials of the respective layers may be the same or different.
• the substrate may comprise one, two, three, four or five or more layers and typical multi-layer structures may be of the AB, ABA, ABC, ABAB, ABABA or ABCBA type.
• the substrate comprises one, two or three layers, and io preferably only one layer. In one embodiment, the substrate comprises three layers.
• Formation of the substrate may be effected by conventional techniques well-known in the art. Conveniently, formation of the substrate is effected by extrusion, in accordance with the procedure described
• the process comprises the steps of extruding a layer of molten polymer, quenching the extrudate and orienting the quenched extrudate in at least one direction.
• the substrate may be uniaxially-oriented, but is preferably biaxially- oriented, as noted above. Orientation may be effected by any process
• Biaxial orientation is effected by drawing in two mutually perpendicular directions in the plane of the film to achieve a satisfactory combination of mechanical and physical properties.
• simultaneous biaxial orientation may be
• the substrate-forming polymer is
• Orientation is then effected by stretching the quenched extrudate in at least one direction at a temperature above the glass transition temperature of the polyester.
• Sequential orientation may be effected by stretching a H 1 " 1" !
• the cast film may be stretched simultaneously in both the forward and transverse directions in a biaxial stenter. Stretching is effected to an extent determined by the nature of the polymer, for example polyethylene terephthalate is usually stretched so that the dimension of io the oriented film is from 2 to 5, more preferably 2.5 to 4.5 times its original dimension in the or each direction of stretching. Typically, stretching is effected at temperatures in the range of 70 to 125°C. Greater draw ratios (for example, up to about 8 times) may be used if orientation in only one direction is required. It is not necessary to stretch equally in the machine
• a stretched film may be, and preferably is, dimensionally stabilised by heat-setting under dimensional restraint at a temperature above the glass transition temperature of the polyester but below the melting
• the actual heat-set temperature and time will vary depending on the composition of the film but should not be selected so as to substantially degrade the mechanical properties of the film. Within these constraints, a heat-set temperature of about 135° to 250 0 C is generally desirable.
• the thermal 25 stability of the components in the coating layer may require careful control of the heat-set temperature in order to avoid or reduce any degradation of those components.
• the heat-set temperature is less than about 235°C, preferably less than 230 0 C.
• substrate is conveniently effected by coextrusion, either by simultaneous coextrusion of the respective film-forming layers through independent orifices of a multi-orifice die, and thereafter uniting the still molten layers, or, preferably, by single-channel coextrusion in which molten streams of ⁇ ' '' ⁇ t ⁇ ie ' ⁇ yp ⁇ e ' p ⁇ l ⁇ ttlW'kb first united within a channel leading to a die manifold, and thereafter extruded together from the die orifice under conditions of streamline flow without intermixing thereby to produce a multi-layer polymeric film, which may be oriented and heat-set as 5 hereinbefore described.
• Formation of a multi-layer substrate may also be effected by conventional lamination techniques, for example by laminating together a preformed first layer and a preformed second layer, or by casting, for example, the first layer onto a preformed second layer.
• the substrate layer is suitably of a thickness from about 5 to io 350 ⁇ m, preferably from 12 to about 300 ⁇ m, and particularly from about 20 to about 200 ⁇ m and particularly from about 30 to about 200 ⁇ m. In one embodiment, the thickness is from about 20 to about 100 ⁇ m, preferably from about 30 to about 100 ⁇ m, preferably from about 30 to about 70 ⁇ m.
• the substrate may contain any of the additives conventionally
• Fillers are particularly common additives for voiding agents, lubricants, anti-oxidants, radical scavengers, UV absorbers, fire retardants, thermal stabilisers, anti-blocking agents, surface active agents, slip aids, optical brighteners, gloss improvers, viscosity modifiers and dispersion stabilisers. Fillers are particularly common additives for voiding agents, lubricants, anti-oxidants, radical scavengers, UV absorbers, fire retardants, thermal stabilisers, anti-blocking agents, surface active agents, slip aids, optical brighteners, gloss improvers, viscosity modifiers and dispersion stabilisers. Fillers are particularly common additives for voiding agents, lubricants, anti-oxidants, radical scavengers, UV absorbers, fire retardants, thermal stabilisers, anti-blocking agents, surface active agents, slip aids, optical brighteners, gloss improvers, viscosity modifiers and dispersion stabilisers. Fillers are particularly common additives for
• Typical fillers include particulate inorganic fillers (such as metal or metalloid oxides, clays and alkaline metal salts, such as the carbonates and sulphates of calcium and barium) or incompatible resin fillers (such as polyamides and polyolefins, in a polyester film substrate) or 25 a mixture of two or more such fillers, as are well-known in the art and described in WO-03/078512-A for example.
• the components of the composition of a layer may be mixed together in a conventional manner. For example, by mixing with the monomeric reactants from which the layer polymer is derived, or the components may be mixed with the polymer by
• ⁇ ' L;: l! ⁇ ' " u la yiS substrate comprises a small amount
• a dye which can assist in the focussing of the radiation source (onto the radiation-absorber in the transfer-assist layer) during the thermal imaging 5 step, thereby improving the efficiency of the heat transfer.
• This dye typically absorbs in the visible region (and in one embodiment around 670nm).
• Suitable dyes are well-known in the art and include blue phthalocyanine pigment or green anthraquinone pigment, such as the widely commercially available Disperse Blue 60 and Solvent Green 28 io dyes.
• the substrate may be modified by the incorporation therein of a light attenuating agent or by physically roughening a surface thereof.
• the light attenuating agent may be an absorber or a diffuser, or a mixture thereof.
• the wavelength ranges at which the imaging and non-imaging laser operate typically in the range
• the absorber 20 from about 300 nm to about 1500 nm determine the wavelength ranges in which the absorber(s) and/or diffuser(s) are active and inactive. For example, if the non-imaging laser operates in about the 670 nm region and the imaging laser at 830 nm, it is preferred that the absorber and/or diffuser operate to absorb or diffuse light in the 670 nm region, rather than
• Typical absorbers include blue phthalocyanine pigments with significant absorption in about the 670 nm range and minimal absoption at 830 nm; such as C.I. Pigment Blue 15 or 15-3 (Sun Chemical Corporation, Cincinnati, Ohio).
• Light diffusers include those materials which scatter light or scatter and absorb light and include white
• the light attenuating agent is used in an amount effective to absorb or diffuse the light from the non-imaging laser, and typically in an amount sufficient to achieve an absorbance (OD) ranging from about 0.1 to about 2.0, typically from about 0.3 to about 1.5, even more typically about 1.2.
• OD absorbance
• Absorbance is the absolute value of log liJ ' L;: dbasy fej'tt ⁇ Ne 1 ⁇ I 0 NPtHe intensity of the incident light and I is the intensity of the light transmitted.
• An absorbance of about 0.1 to 3 or higher corresponds approximately to an absorption of 20 to 99.9% or more of incident radiation.) At an absorbance above about 2.0 the base is likely to 5 be too highly absorbing for the imaging process and below about 0.1 there might not be a sufficient attenuating effect.
• the substrate is preferably unfilled or only slightly filled, i.e. any filler is present in only small amounts, generally not exceeding 0.5% and preferably less than 0.2% by weight of the substrate polymer.
• the substrate will typically be optically clear, preferably having a % of scattered visible light (haze) of ⁇ 6%, more preferably ⁇ 3.5 % and particularly ⁇ 2%, measured according to the standard ASTM D 1003.
• the substrate exhibits a transmittance of the imaging radiation of at least 85%, and preferably at least 90% or more, and in one 15 embodiment at least 95%.
• the substrate exhibits a transmittance of the imaging radiation of between about 85% and 90%.
• the surface characteristics of the substrate will depend on the application for which the imaged article is to be used. Typically, it will be desirable for the substrate, or at the least the surface of the substrate
• one side (or both sides, typically one side) of the substrate may be coated with a "slip coating" comprising a particulate material in order to assist in the handling of the film, for instance to
• slip coating 30 improve windability and minimise or prevent "blocking".
• the slip coating could be applied to either side of the substrate, but is preferably applied to the reverse surface of the substrate, i.e. the surface opposite to the surface on which is coated the transfer-assist coating.
• Suitable slip coatings may comprise potassium silicate, such as that disclosed in, for ⁇ ' IL: Jx ⁇ f!fe ; J L ⁇ 1 ⁇ aiM l N(li: i "5925428 and 5882798, the disclosures of which is incorporated herein by reference.
• a slip coating may comprise a discontinuous layer of an acrylic and/or methacrylic polymeric resin optionally further comprising a cross-linking agent, as disclosed in, 5 for example, EP-A-0408197, the disclosure of which is incorporated herein by reference.
• the reverse side of the substrate or polymeric substrate is coated with an antistatic agent using conventional techniques, such as those described herein, in order to improve io contamination control and improve transport of the film.
• the slip additive referred to hereinabove may be added to an antistatic coating. Static charge build-up can be controlled by increasing the electrical conductivity of a material, and antistatic agents typically operate by dissipating static charge as it builds up. Thus, static decay rate and surface conductivity
• antistatic agents 15 are common measures of the effectiveness of antistatic agents. Any conventional antistatic agent can be used in the present invention.
• Known antistatic agents cover a broad range of chemical classes, including organic amines and amides, esters of fatty acids, organic acids, polyoxyethylene derivatives, polyhydridic alcohols, metals, carbon black,
• Anti-static coatings may also contain anti-blocking inorganic or organic components such as silica, acrylic and/or methacrylic resins such as poly(methyl methacrylate) (PMMA), polystyrene and the like, typically in particulate from, to improve film handling and film transport.
• PMMA poly(methyl methacrylate)
• PMMA poly(methyl methacrylate)
• the coating on the reverse side of the polymeric substrate comprises PMMA (particularly wherein the PMMA is in the form of particles having a diameter in the range of from about 0.1 to about 0.3 ⁇ m, and particularly about 0.2 ⁇ m).
• PMMA is in the form of particles having a diameter in the range of from about 0.1 to about 0.3 ⁇ m, and particularly about 0.2 ⁇ m.
• Various antistatic media are disclosed in US-5589324, US-4225665, EP-A-0036702, EP-A-0027699, EP-A-0190499, EP-A-
• antistatic agents are also surfactants and can be neutral or ionic in nature.
• such an antistatic coating is characterised in that it exhibits a surface resistivity of greater than 16 logi 0 ohms/square at a iP li: a surface resistivity of 16 logTM ohms/square or less at a relative humidity of 50%, particularly at a temperature of 25 0 C. It is recognised that temperature variation typically has only a second order effect on surface resisitivity within normal operating 5 temperatures (for instance within 0 to 100 0 C).
• the dried coating typically exhibits a dry coat weight of from about 0.1 to about 10 mg/dm "2 .
• the thickness of an antistatic layer is generally within a range of from 0.01 to 1.0 ⁇ m.
• the substrate may be coated with a primer
• a primer layer can be applied before any stretching operations are conducted on the cast film, and the transfer-assist coating layer can be applied subsequently, e.g. either after a first stretching operation and before a second stretching operation or after both stretching 15 operations.
• the light-attenuating agent referred to hereinabove may be present in a discrete layer, referred to as light- attenuating layer, which may be coated on the substrate by conventional techniques for instance as an aqueous dispersion of the light attenuating
• a binder such as a copolymer of methylmethacrylate and n- butylmethacrylate, or those referred to herein for the transfer layer
• a minor amount of surfactant such as a fluoropolymer
• the transfer-assist layer should exhibit a radiation transmission in
• 25 the range of from about 20% to about 80%, preferably from about 20% to about 60%, preferably from about 30% to about 50%, more preferably from about 40% to about 50%, at the wavelength of the imaging radiation used in the thermal transfer imaging process.
• the degree of radiation transmission of the transfer assist layer is the degree of radiation transmission of the transfer assist layer.
• the radiation-absorbing compound is preferably present in an amount from about 5% to about 85% by weight of the solids fraction in the coating composition, preferably about 5% to about 60% by weight, I
• the dry thickness of the transfer-assist coating layer is preferably no more than about 5 ⁇ m, preferably no more than about 2 ⁇ m, and preferably no more than about 1 ⁇ m, and is preferably at least 0.05 ⁇ m. In o preferred embodiments, the dry thickness of the transfer-assist coating layer is from about 0.05 to about 1 ⁇ m, preferably from about 0.1 ⁇ m to about 0.6 ⁇ m, preferably from about 0.15 ⁇ m to about 0.6 ⁇ m, and more preferably 0.5 ⁇ m or less. It is surprising that such layer thicknesses, particularly in combination with the preferred levels of radiation-absorbing 5 compound described hereinabove, would be capable of functioning as a transfer-assist layer.
• the radiation-absorbing compound need only absorb radiation at the desired wavelength(s) of the imaging radiation and may be transparent to radiation of other wavelengths.
• a radiation- o absorber which absorbs in the near-infrared region or portion thereof may not absorb in the visible region.
• the radiation-absorbing compound of the radiation of the imaging laser (referred to hereinafter as the "imaging 5 radiation-absorbing compound") is preferably relatively transparent to the radiation of the non-imaging laser.
• the absorbance of the imaging radiation-absorbing compound in the wavelength region of the imaging laser is preferably greater than the absorbance of the imaging radiation- absorbing compound in the wavelength region of the non-imaging laser, o and is preferably greater by a factor of at least 2, preferably at least 5, preferably at least 10, preferably at least 50, and preferably more.
• the radiation-absorbing compound(s) should be sufficiently thermally stable to retain functionality at the processing conditions experienced during film manufacture.
• the I1J ' L' of the radiation-absorbing compound is at least 18O 0 C, preferably at least 200 0 C, preferably at least 22O 0 C and preferably at least 235 0 C.
• the radiation-absorbing compound is preferably also selected on 5 the basis of its solubility or dispersibility in water; its compatibility with a specific binder of the transfer-assist layer; and the wavelength ranges of absorption required for the transfer-assist layer. Soluble and dispersible radiation-absorbing compounds promote homogenous thin layers which absorb radiation homogenously, and without scattering of the incident io radiation, which can occur with particulate materials.
• Suitable radiation-absorbing materials are selected from dyes (such as visible dyes, ultraviolet dyes, infrared dyes, fluorescent dyes and radiation-polarizing dyes), pigments, metals and metal-containing compounds, metallized films (for instance those formed by sputtering and
• dyes and pigments suitable as radiation-absorbers include cyanine compounds (including indocyanines, phthalocyanines, polysubstituted
• a source of suitable infrared-absorbing dyes is H. W. Sands Corporation 5 (Jupiter, FL, US).
• Suitable dyes include 2-[2-[2-(2-pyrimidinothio)-3-[2-(1 ,3- dihydro-1 ,1-dimethyl-3-(4-sulphobutyl)-2H-benz[e]indol-2- ylidene)]ethylidene-1-cyclopenten-1-yl]ethenyl]-1 ,1dimethyl-3-(4- sulphobutyl)-1 H-benz[e]indolium, inner salt, sodium salt; and indocyanine green, having CAS No. [3599-32-4].
• Infrared-absorbers can also be selected from those marketed by American Cyanamid Co. (Wayne, NJ), Cytec Industries (West Paterson, NJ) or by Glendale Protective Technologies,
• CYASORB IR- 99, IR-126 and IR-165 N,N'-2,5-cyclohexadiene-1 ,4-diylidenebis[4- (dibutylamino)-N-[4-(dibutylamino)phenyl]benzenaminium bis[(OC-6-11 )- hexafluoroantimonate(i-)].
• Other suppliers include Hampford Research lnc (Stratford, CT).
• polyolefins including polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE); copolyester resins in alcohol (such as those commercially available as VylonalTM); ethylene vinyl acetate resins; polyoxazolines; high MW polyolefin alcohols, poly(ethylene oxide); polyoxymethylene; gelatin; phenolic resins (such as novolak and resole 25 resins); polyvinylbutyral resins; polyvinyl acetates; polyvinyl acetals; polyvinylidene chlorides and fluorides; polyvinyl chlorides and fluorides; polycarbonates; and; and polyalkylenecarbonat.es.
• the binder may also comprise the condensation product of an amine such as melamine with an aldehyde such as formaldehyde, optionally alkoxylated (for instance
• Preferred polyesters are selected from copolyesters comprising functional comonomers which improve hydrophilicity, and which typically o introduce pendant ionic groups, preferably an anionic group, into the polyester backbone, for instance pendant sulphonate or carboxylate groups, as is well known in the art.
• Suitable hydrophilic polyesters include partially sulphonated polyesters, including copolyesters having an acid component and a diol 5 component wherein the acid component comprises a dicarboxylic acid and a sulphomonomer containing a sulphonate group attached to the aromatic nucleus of an aromatic dicarboxylic acid.
• the sulphomonomer is present in the range of from about 0.1 to about 10 mol%, preferably in the range of from about 1 to about 10 mol%, and more o preferably in the range from about 2 to about 6%, based on the weight of the copolyester.
• the number average molecular weight of the copolymer is in the range of from about 10,000 to about 15,000.
• the molecular weight of the polymer is in the range of from about 10,000 to about 1 ,000,000, particularly 40,000 to about 500,000.
• the binder is selected from polytetrafluorethylene (PTFE); polyvinyl fluoride (PVF); polyvinylidene fluoride (PVDF); polychlorotrifluoroethylene (PCTFE); polyvinylidene chloride (PVDC); polyvinylchloride (PVC); nitrocelluloses; 5 polymethylmethacrylates; polyalpha-methylstyrene; polyalkylenecarbonates; and polyoxymethylene, and particularly from nitrocelluloses; polymethylmethacrylates; and polyalkylenecarbonates (particularly wherein the alkylene group is C 1 -C 8 alkylene group, particularly a Ci-C 4 alkylene, and particularly ethylene or polypropylene).
• the humectant component should be compatible with the radiation
• Polymeric humectants include poly(ethylene oxide) compounds and derivatives and polymer electrolytes such as poly(ethylene oxide) salts (particularly the lithium salts); polyvinylpyrollidones and their salts; polycarboxylic acids and their salts (e.g. GlascolTM RP2); polyamine salts (e.g. AlcostatTM RP1); and
• polystyrenesulphonates include gelatin; cellulosics (e.g. hydrocyethylcellulose); polysaccharides (e.g. starch); and chitosan and its salts.
• Surfactant humectants may be non-ionic (e.g. glycerol monostearates, glycerides (particularly the mono- and tri ⁇ glycerides), ethoxylated/propoxylated and glycerol derivatives of
• the polymeric binder may itself provide humectant properties, and the incorporation of a separate humectant is not necessary.
• Suitable binder-humectants may be selected according to the above physical characteristics, and should be capable of absorbing water as well as forming a film.
• Suitable binder-humectant materials io include PVOH and cellulosic esters and ethers.
• the transfer-assist layer preferably also comprises one or more surfactant(s), preferably anionic and/or nonionic surfactants, to improve wetting of the transfer-assist coating on the surface of the substrate or polymeric substrate.
• surfactants include polyether-modified
• the cross-linking agent may be used in amounts of up to about 25% by weight based on the weight of the solid of the transfer-assist layer, and typically in the range of 5 to 20% by weight of solids.
• a catalyst is preferably employed to facilitate the cross-linking action of the cross- linking agent.
• Such a sequence of stretching and coating is especially preferred for the production of a coated film substrate which is preferably firstly stretched in the longitudinal direction over a series of rotating rollers, coated with the coating composition, and then stretched transversely in a stenter oven, preferably followed by heat setting.
• the coating composition may be
• the material(s) may be disposed in one or more layers with or without a binder, and are selectively transferable in entirety or in portions upon exposure to imaging radiation. Components of the transfer layer in a single portion may be
• Examples of materials that can be selectively patterned from donor elements as transfer layers and/or as materials incorporated in transfer layers include colorants (including pigments and/or dyes dispersed in a binder), polarizers, liquid crystal materials, particles (including spacers for liquid crystal displays, magnetic particles, insulating particles and conductive particles), emissive materials (including phosphors and/or organic electroluminescent materials), non-emissive materials that may be incorporated into an emissive device (for example, an electroluminescent device), hydrophobic materials (including partition banks for ink jet receptors), hydrophilic materials, multilayer stacks (e.g., multilayer device constructions such as organic electroluminescent devices), micro- structured or nano-structured layers, photoresist, metals, polymers, adhesives, binders, and bio-materials, and other suitable materials or combination of materials.
• the transfer layer includes one or more material(s) useful in display applications, particularly in the preparation of a colour filter.
• suitable transparent colorants include Ciba-Geigy Cromophtal Red A2B®, Dainich-Seika ECY-204®, Zeneca Monastral Green 6Y-CL®, and BASF Heliogen Blue L6700®.
• Suitable transparent colorants include Sun RS Magenta 234-007®, IH 1 Sun GS Cyan 249-0592®, Sun RS Cyan 248-061 , Ciba-Geigy BS Magenta RT- 333D®, Ciba-Geigy Microlith Yellow 3G-WA®, Ciba-Geigy Microlith Yellow 2R- WA®, Ciba-Geigy Microlith Blue YG-W A®, Ciba-Geigy Microlith Black C-WA®, Ciba-Geigy 5 Microlith Violet RL-WA®, Ciba-Geigy Microlith Red RBS-WA®, any of the Heucotech Aquis II® series, any of the Heucosperse Aquis III series, and the like.
• pigments that can be used as colorants are latent pigments such as those available from Ciba-Geigy.
• the colours of the transfer layer may be selected as needed by the user as appropriate. o
• pigments are used as the colorant, they are preferably transparent.
• Cross-linking before transfer can provide more stable donor media, better control over film morphology that might lead to better transfer and/or better performance properties in the OLED device, and/or allow for the construction of unique OLED devices and/or o OLED devices that might be more easily prepared when crosslinking in the device layer(s) is performed prior to thermal transfer.
• light emitting polymers include poly(phenylenevinylene)s (PPVs), poly-para- phenylenes (PPPs), and polyfluorenes (PFs).
• PVs poly(phenylenevinylene)s
• PPPs poly-para- phenylenes
• PFs polyfluorenes
• cross-linkable transport layer materials for OLED devices include the silane functionalized triarylamine, the poly(norbomenes) with pendant triarylamine as disclosed in Bellmann et al., Chem Mater 10, pp.
• Light emitting, charge transport, or charge injection materials used in transfer layers of the present invention may also have dopants incorporated therein either prior to or after thermal transfer. Dopants may be incorporated in materials for OLEDs to alter or enhance light emission 5 properties, charge transport properties and/or other such properties. Thermal transfer of materials from donor sheets to receptors for emissive display and device applications is disclosed in U.S. Pat. Nos. 5, 998,085 and 6,114,088, and in WO-00/41893-A.
• the transfer layer comprises a suitable binder system and o may also comprise a minor amount of radiation absorber, and/or surfactant(s) (including silicone surfactants and fluorosurfants) or other additives.
• Other optional additives include dispersing agents, UV- stabilizers, plasticizers, cross-linking agents, coating aids and adhesives.
• the " " " an amount from about 0.5% to about to about 5% by weight of the solids fraction, preferably about 1.5% to about 3% by weight.
• the radiation-absorbing compound may be the same as or different to the radiation-absorbing compound in the transfer-assist layer. 5
• the binder should not self-oxidize, decompose or degrade at the temperatures achieved during processing.
• the monomers for the above 5 polymers can be substituted or unsubstituted. Mixtures of polymers can also be used.
• Other suitable binders include vinyl chloride polymers, vinyl acetate polymers, vinyl chloride-vinyl acetate copolymers, vinyl acetate- crotonic acid copolymers, styrene-maleic anhydride half ester resins, (meth)acrylate polymers and copolymers, polyvinyl acetals), polyvinyl 0 acetals) modified with anhydrides and amines, hydroxy alkyl cellulose resins and styrene acrylic resins.
• the transfer layer can be coated onto the transfer-assist layer, or other suitable adjacent layer as described herein, according to conventional techniques including bar coating, gravure coating, extrusion 5 coating, vapor deposition, lamination and other such techniques.
• Aqueous or non-aqueous dispersions may be used for application of the transfer layer.
• a cross-linkable transfer layer material or portions thereof may be cross-linked, for example by heating, exposure to radiation, and/or exposure to a chemical curative, 0 depending upon the material.
• the transfer efficiency should be high, and preferably at least 85%, and more preferably 90 to 100 % of material should be transferred from the donor element to the receptor element.
• the fidelity of the transfer should be high, i.e. the visible transmission spectrum of the image should not substantially change before and after thermal transfer,
• the resolution of the transferred image should be high with good line 0 edge quality.
• the transferred image should exhibit high smoothness or planarity on the receptor.
• '' ⁇ ' ⁇ ' effiefeHyy'-incI fidelity of transfer should be relatively independent of the power of the radiation used to effect the thermal transfer (for instance at different power levels of the irradiating laser), and this factor is typically referred to as "power latitude".
• a transfer-assist layer 5 having good power latitude shows little variation in the transfer parameters with variation in the power of irradiation.
• the radiation 5 transmission of the transfer-assist layer is measured after the transfer-assist layer has been coated onto a substrate or polymeric substrate, and so the measured transmission value of the transfer- assist layer and substrate composite film requires adjustment or calibration to take into account any absorption by the substrate or io polymeric substrate, and this may be effected in accordance with standard analytical methods by measuring the transmission of the uncoated substrate.
• Optical density may be measured by ASTM E97 (densitometer).
• Transfer efficiency in the preparation of colour filters is conveniently measured by measuring the CIE transmission colour spectrum of the donor element before and after transfer, typically only over discrete regions of the spectrum, and taking a ration of the measured transmission parameters.
• the line edge quality of the transferred image is typically measured by computer scanning an edge in an image and measuring the distance along the edge between two points to produce two values, L2 and L1 , L1 being between the distance prior to image transfer, and L2 being the distance after image transfer, an L2/L1 of 1.0 5 representing a perfect edge.
• Viscosity may be measured using ASTM D4300.
• the water-absorbing properties of the humectant may be measured using a modified ASTM D750 procedure wherein an immersion tank is replaced with a humidity chamber. A known weight of humectant is placed in the humidity chamber at 27° and 90% relative humidity. ⁇ ' U S "" iLjl f B ⁇ J sim pl4 ;i ril U&fgrfed at regular intervals until the sample weight remains constant. The percentage increase in weight is then calculated.
• FIG. 1 shows an 5 assemblage (400) of a donor element (100) and a receptor element (410), the donor element comprising a transfer layer (130), a transfer-assist layer (120) and a substrate (110), said donor element (100) being in contact at the transfer layer with a receptor element (410), and being exposed to radiation (as signified by the arrows, 420) during a (direct) o thermal imaging process.
• Figure 2 corresponds to Figure 1 except that the thermal transfer is effected via gap transfer, and the donor and receptor elements are separated by a black matrix (430) across a gap of air (480).
• the invention is further illustrated by the following examples. It will be appreciated that the examples are for illustrative purposes only and are 5 not intended to limit the invention as described above. Modification of detail may be made without departing from the scope of the invention.
• Coating compositions comprising one or more of the following ingredients were prepared: (i) A 46% solids aqueous dispersion of a copolymer of ethyl acrylate o (EA; 48 mole %), methyl methacrylate (MMA; 48 mole %) and methacrylamide (MA; 4 mole %) (derived from AC201 ®; Rohm and
• TegoWetTM 251 (4), a polyether modified polysiloxane copolymer (Goldschmidt); propyldimethyl-beta-hydroxyethyl- ammonium-dihydrogen-phosphate (Cytec);
• compositions shown in Tables 1A and 1 B were prepared using the amounts of ingredients (weight in grams) described therein.
• the formulations were then poured through a No. 541 Whatman filter paper in a Buchner funnel and vacuum filtered to remove any aggregates of carbon black or undissolved dye.
• the in-line coated films were prepared as follows.
• the polymer composition was melt-extruded, cast onto a cooled rotating drum and stretched in the direction of extrusion to approximately 3 times its original dimensions at a temperature of 75°C.
• the cooled stretched film was then coated on one side with the transfer-assist coating composition to give a wet coating thickness of approximately 20 to 30 ⁇ m.
• a direct gravure coating system was used to apply the coatings to the film web.
• a 60QCH gravure roll (supplied by Pamarco) rotates through the solution, taking solution onto the gravure roll surface.
• the gravure roll rotates in the opposite direction to the film web and applies the coating to the web at one point of contact.
• the coated film was passed into a stenter oven at a temperature of 100-110°C where the film was dried and stretched in the sideways direction to approximately 3 times its original dimensions.
• the biaxially stretched coated film was heat-set at a temperature of about 19O 0 C by conventional means.
• the coated polyester film is then wound onto a roll.
• the total thickness of the final film was 50 ⁇ m; the dry thickness of the transfer-assist coating layer is given in Tables 2 to 10.
• Off-line coating of the substrate is effected as follows.
• the polymeric substrate (prepared as described above, omitting the in-line coating step) is laid onto a mechanized rubber roller, and a wire-wound bar is laid onto the film.
• Coating solution is metered onto the film on the input side of the wire-wound bar using a 10ml syringe with a "Luer-Lok" tip (Becton Dickinson, Franklin Lakes, NJ).
• a 1 micron GMF-150 filter is fitted onto the syringe (Whatman, Inc., Clifton, NJ). Solution is pushed through the filter onto the substrate.
• the rubber roller then begins rotating, advancing the substrate under the wire-wound bar, which meters a uniform coating onto the web.
• the wet coating is dried, and the coated are not stretched, proportionally less NIR absorber (relative to the examples made by an in ⁇ line process) is required in the formulations to achieve a similar % transmission at the desired wavelength.
• NIR absorber relative to the examples made by an in ⁇ line process
• the amount of NIR absorber used in the off-line process is reduced, typically to between 2 and 5 times that of the corresponding in-line formulation to compensate for the absence of a sideways draw.
• the percentage of solids in the formulations o was diluted in order to achieve a coat weight and %transmission which is comparable to the in-line coated formulations.
• Both in-line coated formulations retained 100% of the crosshatched areas, while the off-line coated formulations retained 0% of the Crosshatch areas.
• the in-line coated layers have significantly better adhesion to the polyester substrate, and are therefore more resistant to blocking, scratching and abrasion than o the off-line coated films.
• the composite films comprising the polyester substrate and transfer-assist coating were then used in the manufacture of a colour filter.
• the coated substrate was coated with a transfer layer formulation (referred to hereinafter as "Blue 72") made by combining 67.4 parts blue 5 pigment dispersion (49.3% non-volatile), 3.60 parts violet pigment dispersion (25% non-volatile), 229.2 parts water, 90.8 parts Joncryl® 63, 2.4 parts aqueous ammonium hydroxide (3%), 1.4 parts Zonyl®FSA, 1.20 parts SDA-4927, and 4 parts Aerotex 3730, to form a donor element.
• a transfer layer formulation referred to hereinafter as "Blue 72”
• Blue 72 transfer layer formulation made by combining 67.4 parts blue 5 pigment dispersion (49.3% non-volatile), 3.60 parts violet pigment dispersion (25% non-volatile), 229.2 parts water, 90.8 parts Joncryl® 63, 2.4 parts aqueous ammonium hydroxide
• the donor element was then juxtaposed with a receptor element (a glass color o filter substrate having previously transferred color pixels), such that the layer was substrate/transfer assist layer/transfer layer/pixels/glass, to form an imageable assemblage.
• the imageable assemblage was imaged using a rapidly moving, blinking 830nm laser impinging on the substrate at a fluence of approximately 400 mJ/cm 2 and exposure time of less than 5 5 ⁇ s to transfer blue pixels.
• the thermal transfer process and the quality of the colour filters were assessed by measuring x, y and Y values for colour coordinates in the CIE system in which x and y describe the hue of a colour, and Y is a measure of the luminance (ratio of transmitted photons/incident photons).
• Tables 2 to 10 show the imaging results.
• the transfer lp The aim is to achieve a high and consistent transfer efficiency over a range of incident laser power. This is desirable as the power output of commercial lasers is prone to drift in practice.
• the preferred embodiment which comprises use of a near-IR absorber and 5 humectant, provides the most balanced properties in terms of transfer efficiency and colour values, and in this embodiment the transfer efficiency is lifted to above 80% at almost all power levels with colour values in or near the target specification.
• a coating formulation similar to that of Formulation I was made up as follows:
• polyester binder (Amertech Polyester Clear; American Inks and
• a coating formulation was made up as follows: (i) demineralised water : 800 g; (ii) dimethylaminoethanol : 5 g; ! ' ' " Research; formulation corresponds to
• the red transfer layer had a dried coating weight of 40.0 mg/sqdm.
• This forms a red donor element.
• a section of the red donor element was then juxtaposed with a receptor element (a glass color filter substrate having previously transferred color pixels) such that the red 'cy ' tiftgi ' ⁇ 'm- ⁇ o ' ntaWwrtl 1 !TM imaged pixels to form an imageable assemblage.
• the imageable assemblage was imaged using a rapidly moving 830 nm laser impinging on the substrate at a fluence of approximately 400 mJ/cm 2 and exposure time of less than 5 ⁇ s to transfer red pixels.
• the red donor element is then removed, and the imaged color filter baked at 230 0 C for 1 hour to solidify the transferred color pixels.
• the annealed filter was examined with a microscope at 200X total magnifying power, and the line-widths of the annealed red lines measured at a range of incident laser powers, along with the surface roughness. A line-width of at least 85 ⁇ m is desirable.
• the thermal transfer process and the quality of the colour filters were assessed by measuring x, y and Y values for colour coordinates in the CIE system in which x and y describe the hue of a colour, and Y is a measure of the luminance (ratio of transmitted photons/incident photons).
• Formulations L and M exhibit the target colour properties, surface roughness and line-width and these are achieved at lower applied power, and over a wider range of operating power (which is desirable as laser power can drift in practice) .

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• 2005
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