WO1997000464A1

WO1997000464A1 - Identifiable color proofing elements

Info

Publication number: WO1997000464A1
Application number: PCT/US1996/006304
Authority: WO
Inventors: Jack E. Cook; Richard S. Fisch
Original assignee: Minnesota Mining And Manufacturing Company
Priority date: 1995-06-16
Filing date: 1996-05-02
Publication date: 1997-01-03
Also published as: AU5637696A

Abstract

The use of fluorescent or phosphorescent transparent polymeric beads deposited upon or incorporated into at least one of the layers deposited upon a substrate in a negative or positive composite color proof is described. The fluorescent or phosphorescent beads allow easy identification of the color proofing materials used in the color composite, without interfering with the color rendition of the proof. It also allows one to identify the color proofing materials used when the colored images are transferred onto an unmarked or alternative support.

Description

IDENTIFIABLE COLOR PROOFING ELEMENTS

Field of the Invention

This invention relates to negative or positive acting color proofing systems. In particular, this invention relates to color proofing elements having transparent polymeric beads containing fluorescent or phosphorescent materials incoφorated into or deposited upon at least one ofthe permanent layers for identification.

Discussion of the Art

In color reproduction, the color accuracy of graphic art color separation negatives or positives are generally verified using color proofing systems prior to making the corresponding printing plates. The color proofing systems must provide a consistent representation ofthe final color print. A printer will usually specify a particular brand of color proofing films due to the relationship that the printer has developed between the final color print produced on the press and the corresponding contract proof made using the specified brand of proofing materials.

Each proofing system is designed with different compositions, colorants, layer thicknesses, tonal curves, dot retention, and final construction layout, all of which have a significant influence on the color rendition ofthe final composite proof. Therefore, no two proofing systems provide identical proofs using the same color separation films. Because ofthe differences between proofing systems, it is critical that the printer be able to identify the proofing system used.

It is equally important that the means for identification not adversely interfere with the visual color reproduction. Typically the commercially available proofing systems provide a permanent opaque substrate which may contain the brand identification on the backside ofthe opaque substrate. However, a user is not required to use the marked substrate and sometimes prefers to transfer the imaged film onto the printing stock to be used in the printing job using methods such as those described in U.S. Patent Nos. 5,240,810; 5,094,931; and 4,482,625. This creates a problem for identification ofthe materials used to make a particular composite color proof, especially when the printer contracts with a color separation agency to produce a set of color separation films and a particular corresponding contract composite color proof for verification. Therefore, there is a need for a convenient method of identifying color proofing materials in a final color proof composite that allows flexibility in choosing the paper substrate and does not interfere with the visual rendition ofthe color proof.

It is not uncommon to use fluorescent materials to mark materials. For example, fluorescent microspheres have found widespread use in biomedical applications as analytical tools in labeling antibodies and marking cell surfaces. An example of this type of biomedical application is described in U.S. Patent No. 5,132,242; where a process for making 500 angstrom fluorescent microspheres having a high degree of fluorescence is disclosed.

Summary ofthe Invention The present invention provides a composite color proof comprising a substrate and deposited thereon multiple layers comprising multiple colored images and having fluorescent or phosphorescent transparent polymeric beads deposited upon or incorporated within at least one ofthe layers deposited on the substrate.

Another embodiment provides a photosensitive single sheet color proofing element comprising, in order: (a) a releasable carrier; (b) a photosensitive color coated layer; (c) an optional barrier coated layer; and (d) an adhesive coated layer; wherein, fluorescent or phosphorescent transparent polymeric beads are incorporated into at least one ofthe coated layers.

In still another embodiment, a photosensitive single sheet color proofing element is provided comprising, in order: (a) a releasable carrier; (b) a photosensitive color coated layer; (c) an optional barrier coated layer; and (d) an adhesive coated layer; wherein, fluorescent or phosphorescent transparent polymeric beads are deposited upon the surface of at least one ofthe coated layers. The photosensitive color layers may be either photoinsolublizable giving rise to a negative-acting color proofing element or photosolublizable giving rise to a positive-acting color proofing element.

Detailed Description ofthe Invention

The present invention provides a negative or positive composite color proof comprising fluorescent or phosphorescent transparent polymeric beads incorporated into at least one ofthe layers deposited on the substrate ofthe color proof composite. Alternatively, the fluorescent or phosphorescent beads may be interposed between the layers or present on the surface ofthe color proof.

A preferred embodiment utilizes a negative-acting or positive-acting color proofing element comprising: a releasable carrier; a photosensitive color coated layer; an optional barrier coated layer; and an adhesive coated layer; wherein fluorescent or phosphorescent transparent polymeric beads are incorporated into one or any combination ofthe coated layers. Since all or part ofthe coated layers become a permanent part ofthe finished color proof composite, the proofing elements used to make the final color composite proof are easily identified regardless ofthe final substrate upon which the proof is made or transferred upon. Alternatively, the fluorescent or phosphorescent transparent polymeric beads may be deposited onto the surface of one or a combination ofthe coated layers. For example, the fluorescent or phosphorescent beads may be printed onto the surface ofthe layer using conventional printing methods. This approach would allow one to print an image, such as a logo or code, which becomes visible upon irradiation with the appropriate stimulable radiation. The fluorescent or phosphorescent materials may be incoφorated into transparent polymeric beads by either chemically bonding the materials to the transparent polymer or simply dissolving or dispersing the materials in the monomers or oligomers during the preparation ofthe transparent polymeric beads. If the fluorescent or phosphorescent materials are uniformly dispersed in the transparent polymer, then any fluorescent or phosphorescent compound can be used. However, if the fluorescent or phosphorescent materials are chemically bonded to the transparent polymer, then the fluorophor and phosphor must have some functionality that can chemically react with the transparent polymer. For example, one could incoφorate a pendant ethylenically unsaturated group onto the fluorophor or phosphor which becomes part ofthe transparent polymer during the polymerization process. Alternatively, one could provide a covalently reactive site on the fluorophor or phosphor which reacts with a functional group on the transparent polymer. For example, in U.S. Patent No. 5,132,242, a process is described where fluorescent microspheres are prepared by reacting an acrylic latex bead with a diamine and a fluorescent amine at an elevated pH to attach a spacer arm and a fluorescent marker to the bead by transacylation of ester terminations on the surface ofthe bead.

The fluorescent or phosphorescent materials may be any fluorophors or phosphors capable of being dispersed, dissolved or reacted with the transparent polymer ofthe polymeric bead. It is desirable that the bead is nearly colorless so that it is not visible to the naked eye, under normal lighting or viewing conditions, when incoφorated into the color proofing construction (e.g., does not cause a color shift of more than 1.0 delta E when measured with a spectrophotometer between 420 nm and 700 nm). It is also highly desirable that the fluorophors or phosphors emit visible light only when stimulated with ultraviolet radiation, in particular commercially available black lights, which have outputs in the range of

250 to 400 nanometers. The concentration of fluorescent or phosphorescent materials incoφorated into the bead needs to be sufficient to render the bead visible when stimulated with the appropriate radiation. Even though there is no specific upper limit to the concentration ofthe fluorescent or phosphorescent materials in the bead, there are some practical limitations due to solubility ofthe materials used and manufacturing process limitations. Typical concentrations are between 0.1% and 10% by weight ofthe bead, preferably between 0.5% and 7.5%, more preferably between 1% and 5%. Fluorophors and phosphors are well known in the art. Any ofthe commercially known materials may be used depending upon their solubility or compatibility with the transparent polymer in the polymeric bead.

Particularly useful fluorophors or phosphors are optical brighteners such as, coumarins (i.e., Aclarat™ 8678, available from Sandoz chemicals, Charolette, NC), fluoresceins, stilbenes (i.e., Tinopal™ PT, available from Ciba Geigy, Greensboro, NC; and Leucophor™ available from Sandoz Chemicals, Charlotte, NC), benzoxazoles (i.e., Uvitex™ OB available from Ciba Geigy, Hawthorne, NY), benzotriazoles, benzothiazoles, and benzimidazoles.

Typical polymerizable monomers for transparent polymers include styrene, substituted or unsubstituted alkyl (meth)acrylates, allyl (meth)acrylates, aryl (meth)acrylates, alkylene diol di(meth)acrylates, pentaerythritol tetra(meth)acrylate and trimethylolpropane tri(meth)acrylate. Each of these monomers may be used separately, or in combination thereof. Any copolymerizable monomer may be used as long as the transparency ofthe beads is not significantly interfered with. In other words, the increase in haze in the polymeric bead should not interfere with the fluorescence or phosphorescence ofthe fluorophor or phosphor within the bead. The transparent polymeric beads used in the present invention can be produced by either of three generally known suspension polymerization methods.

The method described in U.S. Patent No. 4,952,650 uses conventional suspension agents with optional anionic surfactants. The method described in U.S. Patent No. 4,912,009, referred to as the "limited coalescence method", uses a negatively- charged colloidal silica suspending agent and a water-soluble promoter. The "surfactant method" employs a surfactant as a suspending agent, to produce smaller particle sizes. Each of these methods is described in more detail below.

The "limited coalescence method" uses a negatively-charged colloidal silica as a suspending agent. A water-soluble "promoter" is used in conjunction with the suspending agent which affects the hydrophobic-hydrophilic balance ofthe colloidal particles. More specifically, the promoter forms a complex with the suspending agent which is less hydrophilic than the colloidal particles ofthe suspending agent. As stated in U.S. Patent No. 2,932,629, the promoter drives the particles ofthe colloid to the liquid-liquid interface ofthe oleophilic or hydrophobic droplets and the aqueous medium. The colloidal silica particles have dimensions from about 1 to 100 nm and preferably from about 5 to 70 nm. The size and concentration of these particles controls the size ofthe polymer particles. Smaller ?ilica particles and higher silica concentration provides smaller bead diameters. S ible hydrophilic colloidal silica as suspending agents are available commercially induding; Ludox™ TM(20 nm particle size) Ludox™ HS-40 (12 nm particle size), Ludox™ SM (7 nm particle size) and Ludox™ AM (12 nm particle size) all of which are available from LE. Du

Pont de Nemours Co., Wilmington, DE; and Nalcoag™ 1060 (60 nm particle size) available from Nalco Chemical company, Chicago, IL. Typically, about 0.3 to 5 percent by weight of a suspending agent is used based upon the weight ofthe aqueous phase. A water-soluble organic promoter moiety which adjusts the hydrophile- lipolphile balance on the surface ofthe silica stabilizer is particularly useful. Typically, the promoter is a low molecular weight (i.e., about 200 to 1,000 number average molecular weight) condensation polymer of a lower alkylene dicarboxylic acid and an alkanol amine. The dicarboxylic acid can have an alkylene chain from about 2 to 6 carbon atoms in length. The preferred diacid of this class is adipic acid. The alkanol amine preferably is a lower alkanol amine of which the alkanol groups contain from about 1 to 4 carbon atoms, selected from the group consisting of diethanolamine, 2-amino-2-ethyl- 1,3 -propanediol, methyl aminoethanol, N- methyldiethanolamine, N-propyldiethanolamine and N-butyldiethanolamine. Preferably, the promoter is a condensation polymer of adipic acid and diethanolamine. The components ofthe promoter are chosen to ensure good water solubility and sufficient complexing with colloidal silica. The condensation polymer forms a complex with hydrophilic colloidal silica, which is also hydrophilic but is less hydrophilic than the silica alone. As a consequence, the complex is compatible with the hydrophobic or oleophilic monomers dispersed in the aqueous reaction medium. The complex coats the monomer droplets and inhibits their coalescence. Typically, about 0.02 to 0.5 percent by weight of a promoter is used based on the weight ofthe aqueous phase.

The polymeric beads can also be prepared using a "stabilizer-surfactant method" which utilizes suspension stabilizers that are conventionally used in suspension polymerization processes. The terms "suspension stabilizer", "suspending agents", and "suspension agents" are used interchangeably herein. They may be minimally water-soluble inorganic salts such as tribasic calcium phosphate, calcium carbonate, calcium sulfate, barium sulfate, barium phosphate, magnesium carbonate, and mixtures thereof. Preferred inorganic suspending agents include barium sulfate, tribasic calcium phosphate, and mixtures thereof. Water¬ soluble organic suspending agents may also be used such as polyvinyl alcohol, poly-N-vinylpyrrolidone, polyacrylic acid, polyacrylamide, and hydroxyalkyl cellulose. The suspending agent is present in amounts ranging from about 0.01 to 5 parts by weight based upon 100 parts of total monomers present. The surfactants useful in the stabilizer-surfactant method are typically anionic surfactants, preferably sodium lauryl sulfate and sodium dioctyl sulfosuccinate. Nonionic surfactants may also be included so long as an anionic surfactant is present and predominates. The amount of surfactant is preferably from about 2.5 ppm to about 1.0 part based on 100 parts of total monomer content. When polymeric beads having a diameter less than one micron are desired then a surfactant or emulsifying agent alone is used as the suspending agent. Surfactants or emulsifiers useful in the "surfactant method" are typically anionic surfactants, cationic surfactants and nonionic surfactants. Suitable anionic surfactants include alcohol sulfates, alkylaryl sulfonates, ethoxylated alkyl phenol sulfates, ethoxylated alkyl phenol sulfonates and mixtures thereof. Suitable cationic surfactants include quaternary ammonium salts wherein at least one higher molecular weight group and two or three lower molecular weight groups are linked to a common nitrogen atom to produce a cation, and wherein the electrically balancing anion is selected from the group consisting of a halide, acetate, nitrite, and lower alkosulfonate, and mixtures thereof. Suitable nonionic surfactants include ethoxylated alkyl phenols, ethoxylated fatty acids, and ethoxylated fatty alcohols and mixtures thereof. A combination of more than one surfactant or emulsifier is also found to be useful. For the surfactant methods, a useful concentration range ofthe surfactant is from about 0.2 parts to 5 parts, based on 100 parts of total monomers. Any one of these methods may be used to prepare the transparent polymeric beads. The method of choice will depend upon the particle size and distribution of particle sizes desired. The beads may be incoφorated into any layer ofthe color proofing construction that becomes a permanent part ofthe final proof. However, the particle size and distribution ofthe beads are chosen based upon which layer within the color proofing element the beads are to be incoφorated. Particles or polymeric beads greater in size than the thickness ofthe color layer may appear as voids or pinholes in the coating. The number of outsized particles may be minimized by using a narrow distribution. However, since only a very small percentage of fluorescent or phosphorescent beads are necessary for visibility, outsized beads are typically not a problem.

If the beads are incoφorated into an adhesive layer or a barrier layer of a color proofing element, then the particle size distribution ofthe beads is less important. When used in an adhesive layer, it may be advantageous to use a particle size that is larger than the thickness ofthe adhesive layer. The larger particles may additionally act as slip agents or anti-blocking agents. Suitable mean particle sizes are between 2 and 30 microns, preferably between 2 and 20 microns, more preferably between 5 and 15 microns.

Incoφorating the fluorescent or phosphorescent materials into the polymeric beads concentrates the materials in a small area making the beads easily detectable at very low concentration levels in the layer(s) ofthe proofing element. Therefore, allowing the beads to be easily seen with the naked eye upon stimulation with a suitable light source (e.g., an inexpensive black light). Suitable concentrations of fluorescent or phosphorescent polymeric beads in a single layer is between 0.005% and 5.0% by weight, preferably between 0.01% and 4.5%, more preferably between 0.01% and 4.0%, and most preferably between 0.02% and 3.0%. If the polymeric beads are incoφorated into more than one layer, then the concentration of fluorescent or phosphorescent beads may be reduced further within each individual layer. The presence ofthe fluorescent or phosphorescent polymeric beads not only identifies the materials but also allows oi to easily detect whether or not the layer containing the beads is present in the construction. This is advantageous in the manufacturing ofthe proofing element. The detection of transparent layers can sometimes be very difficult, especially when working in subdued or colored light. Since the color proofing elements are typically sensitized to ultraviolet radiation in the range of 350 to 450 nm, the elements are manufactured in a yellow light environment. If the polymeric beads are incoφorated into one ofthe transparent layers, such as the adhesive or barrier layers, then one can more easily evaluate the existence and uniformity ofthe coated layer in subdued lighting conditions. Since the photosensitive layers are typically sensitized to ultraviolet radiation, the incoφoration ofthe fluorescent or phosphorescent materials in a small area allows one to add low concentrations ofthe fluorescent or phosphorescent materials without adversely affecting the imaging characteristics of the proofing elements. Suφrisingly, the fluorescent or phosphorescent polymeric beads do not cause pinholes in the colored images due to competing absoφtion in a negative system or unwanted irradiation ofthe image due to the light emission from the beads in a positive system.

In the preferred embodiment, the carrier is a dimensionally and chemically stable plastic film. To assist in the handling ofthe films, it may be desirable to include an antistatic coating, such as the antistatic coating comprising a colloidal silica crosslinked with an ambifunctional silane coupling agent described in U.S.

Patent No. 5,344,751. The carrier film is provided with a release surface which may either be a smooth surface ofthe carrier itself or a surface release layer thereon. The function ofthe release surface is to serve as a parting layer between the carrier film and the photosensitive color coating layer. The preferred material for use in the present invention is a 1.5 to 2.0 mil (0.04 to 0.05 mm) polyester film provided with a release layer comprising a cellulose methyl ether, polyvinylpyrolidone or polyvinyl alcohol resin. The release properties ofthe release layer may be adjusted by the addition of surfactants. Preferred surfactants include alkylarylpolyether alcohols, such as Triton™ X-100 (octylphenoxy ethanol, available from Rohm & Haas, Philadelphia, PA), glycerin and ethoxylated castor oil. In the preferred embodiment, the surfactant is present in the release layer at about 0.1 to 5% by weight of solids in the layer, more preferably 0.5 to 2%. Other ingredients may be added such as mold inhibitors, anti-halation dyes, filter dyes, solvents, wetting agents, etc. Additionally, the carrier may have a smooth or textured surface and may also include colorants or UV absorbers. A photosensitive color layer is coated onto the releasable surface ofthe carrier. The photosensitive color layer generally includes a photosensitive material (either photoinsolubilizable or photosolubilizable), a colorant, a binding resin and other optional ingredients, such as plasticizers, surfactants, coating aids, antistats, and UV absorbers. The photoinsolubilizable coating used in a negative-acting color proofing element may be based on a photosensitive polymeric diazonium salt or a photopolymerizable compound, which are well known in the art. Suitable polymeric diazonium salts include materials such as, the condensation product of p- diazodiphenylamine and formaldehyde (described in U.S. Patent No. 2,714,066), and the condensation product of 3-methoxy-4-diazo-diphenyl amine sulfate and

4,4'-bis-methoxy methyl diphenyl ether precipitated as a mesitylene sulfonate salt (described in U.S. Patent No. 4,407,426). Suitable photopolymerizable compounds include materials, such as photopolymerizable oligomers or monomers containing multi-functional (meth)acrylates. Examples of photopolymerizable materials useful in color proofing applications are described in U.S. Patent Nos.

5,248,583 and 4,482,625.

The photosolubilizable coatings used in positive-acting color proofing elements are typically based on naphthoquinone diazide compounds, which are also well known in the art. Suitable diazides include; the ester of t-butyl phenol and 6- diazo-5,6-dihydroxy-5-oxo-l-naphthalene sulfonic acid (available from St. Jean

Photo Chemicals, Inc., St. Jean sur Richelieu, Ouebec); ester of 4-benzoyl-l,3- phenylene and 6-diazo-5,6-dihydroxy-5-oxo-l-naphthalene sulfonic acid (available from St. Jean Photo Chemicals, Inc.); and the ester of bis-(3-benzoyl-4,5,6- trihydroxyphenyl)methane and 2-diazo-l-naphthol-4-sulfonic acid or 2-diazo-l- naphthol-5-sulfonic acid (described in U.S. Patent No. 4,407,926). Pigments or dyes may be used as colorants in the photosensitive color layer. However, pigments or polymeric dyes are preferred since they have a lower tendency for migration between the layers. Pigments are more preferred due to the wide variety of colors available and lower cost. Pigments are generally introduced into the photosensitive formulation in the form of a millbase comprising the pigment dispersed with a binder and suspended into a solvent or mixture of solvents. The dispersion process may be accomplished by a variety of methods well known in the art, such as two-roll milling, three-roll milling, sand milling, ball milling, etc. Many different pigments are available and are well known in the art. The pigment type and color are chosen such that the coated color proofing element is matched to a preset color target or specification set by the industry. Color enhancing additives may be used which include fluorescent, pearlescent, iridescent, and metallic materials. Materials such as silica, polymeric beads, reflective and non- reflective glass beads, or mica may also be added in place of a colorant to provide a textured image. The color enhancing additives or texturing materials may be used either alone or in combination with the above pigments to produce proofs with the desired visual effects.

The type of dispersing resin and the pigment to resin composition ratio chosen are dependent upon the pigment type, surface treatment on the pigment, dispersing solvent and milling process. Some examples of resins suitable for generating millbases which are compatible with the aforementioned photo- oligomers and monomers include; polyvinyl acetate/crotonic acid copolymers, styrene/maleic anhydride partial-ester resins, acid containing acrylic and methacrylic polymers and copolymers, polyvinyl acetals, polyvinyl acetals modified with anhydrides and amines, hydroxy alkyl cellulose resins and styrene/acrylic/acrylic acid resins. The dispersion may contain a mixture of these resins. The pigment to resin ratio in the dispersion is typically between 0.6 to 5.0, preferably between 0.8 to 3.0.

A dispersing agent may be necessary to achieve optimum dispersion quality. Some examples of dispersing agents include; polyester/polyamine copolymers, alkylarylpolyether alcohols, acrylic resins and Disperbyk™ wetting agents available from Byk-Chemie USA, Wallingford, CT. Other components may also be included in the millbase such as surfactants^* to improve solution stability, fluorescent materials, optical brighteners, UN absorbers, fillers, etc.

The preferred composition ofthe millbase solids comprises about 30 - 71% by weight pigment, 15-30% by weight acidic resin, 0-25% non-acidic resin, and 0-

20%, more preferably 0-10% by weight dispersing agents. Additional binders may also be included in the photosensitive color formulation to balance developability and tack for each color. The coating weights ofthe individual colors may vary in order to achieve the preset color target. The color formulations are adjusted to achieve optimum color, resolution, exposure speed and developability. Typical dry color coating weights are between 50 mg/ft² and 150 mg ft² (0.54 g/m² and 1.61 g/m²), preferred 60 mg/ft² and 90 mg/ft² (0.65 g/m² and 0.97 g/m²).

Coated adjacent to the photosensitive color layer is an optional barrier layer. The barrier layer may be present to prevent interaction between the color layer and the adhesive layer. In some constructions the barrier layer also improves developability ofthe non-image areas. A typical barrier layer comprises the same materials as the photosensitive color layer without the colorants.

Coated adjacent to the barrier layer (or photosensitive layer if the barrier layer is not used) is the adhesive layer. The adhesive layer provides a means of laminating the color proofing element to a temporary or permanent substrate under heat and pressure. The solvent used for this coating must not attack or interact with the coatings present on the carrier. Examples of solvents include alcohols, water and hydrocarbon solvents. Because hydrocarbon solvents like heptane and naphtha are prone to irregular coating patterns, due primarily to static, more polar solvents such as water and alcohols are preferred. The adhesive is preferably a thermally activated adhesive that is softenable at a temperature of less than 200°C, preferably within a range between 100°C and 160°C. In contrast with the softening characteristics ofthe adhesive it is desirable that the adhesive not block during storage or shipment. Resins having a Tg between 45°C and 60°C, including copolymers and teφolymers of alkyl acrylate, alkyl methacrylate, styryl, and acrylamide monomers, meet both the lamination criteria and avoid the potential for blocking, without requiring the use of an additional protective liner. Useful resins include polymers, copolymers and teφolymers of methyl methacrylate, n-butyl methacrylate, n-butyl/isobutyl methacrylate, vinylacetates, N-(hydroxymethyl) acrylamide and styrenes. Vinyl acetate polymers have been found to be very sensitive to moisture and can cause blocking ofthe coated materials in shipment and storage if the vinyl acetate component ofthe adhesive is present in amounts greater than 20%. Other additives may be present to aid in coating and performance such as surfactants, coalescent aids, plasticizers, slip agents (i.e., polymethacrylate beads like those described in U.S. Patent No. 4,885,225, silica, polyethylene waxes), optical brighteners, UV absorbers, etc.

A multi-colored composite proof is made by laminating a color proofing element onto a receptor. The carrier may be removed either prior to exposure or prior to the development step. The laminated structure is imaged through a negative or positive color separation graphic art film corresponding to the color of the proofing element to create a latent image. The spectral and power output ofthe exposure unit and the absoφtion ofthe photoinitiator system are chosen for an optimum exposure speed. Typical exposure units are equipped with UV lamps having optimum spectral outputs between 250 nm and 500 nm and a power output between 2.5 and 10 Kilowatts. The exposed laminated structure is then developed with a developer solution. The process of laminating, exposing and developing is then repeated using a different color until the desired multi-colored composite proof is complete. A non-colored or textured image may be added if so desired by laminating, exposing and developing a proofing element whose photosensitive layer contains texturing materials such as those described earlier in place of or in addition to a colorant.

The receptor may be a permanent substrate. A suitable composition for the receptor sheet is a heat stable, wateφroof white paper, such as P-350 (available from Schoeller Technical Paper Sales, Inc. of Pulaski, NY) or Matchprint™ base (available from 3M, St. Paul, MN). The receptor sheet may also be a polyester film or any other heat stable plastic material. Alternatively, the receptor may be a temporary receptor such as those described in U.S. Patent Nos. 5,240,810; 5,192,630; and 5,094,931. When a temporary receptor is used, the color composite may be transferred from the temporary receptor onto any desired support.

Developer solutions used to develop the image after exposure are typically an aqueous solution. In some constructions, tap water is sufficient to develop the image. However, the aqueous solution may contain a combination of sodium or potassium carbonate, and sodium or potassium bicarbonate and a surfactant. In the preferred embodiment, the carbonate is present at about 0.5 - 2.0% by weight, the bicarbonate is present at about 0 - 1.0% by weight, and the surfactant is present at about 0.1 - 1.0% by weight ofthe total aqueous developer solution. The preferred surfactants non-exclusively include; Surfynol™ 465 (ethoxylated tetramethyl decynediol, available from Air Products and Chemicals, Allentown, PA), Surfactol™ 365 (ethoxylated castor oil, available from CasChem Inc., Bayonne, NJ), Triton™ X-100 (octylphenoxypolyethoxyethanol, available from Rohm and Haas, Philadelphia, PA), and Surfynol™ GA (acetylenic diols compounded with other non-ionic surfactants and solvents, available from Air Products and

Chemicals, Allentown, PA).

In some positive-acting constructions, a stronger developer may be necessary. The strength ofthe developer can be easily adjusted using a stronger base such as, sodium or potassium hydroxide, or sodium metasilicate. Fluorescent or phosphorescent beads may also be used in a dry peel apart color proofing system for identification. The beads simply need to be incoφorated into the final composite color proof for identification. The type of proofing system used is not critical as long as the beads are associated with a layer that becomes a permanent part ofthe composite color proof other than the substrate upon which the color proof is made or transferred upon.

The invention will now be illustrated in the following non-limiting examples:

EXAMPLES Unless designated otherwise, all materials are available from Aldrich

Chemicals, Milwaukee, WI. ^* Preparations

The following preparations describe methods for preparing materials used in the examples that are not commercially available.

Preparation of Acidified Butvar™ B-98

A 2 liter 3-necked roundbottom flask equipped with an overhead stirrer was charged with 300 g of Butvar™ B-98 (available from Monsanto Co., St. Louis, MO), 90 g of succinic anhydride, 90 g of triethylamine and 900 g of methyl ethyl ketone. The mixture was heated at 77°C for six hours. The solvent was removed under vacuum yielding a white solid. An Infrared spectrum ofthe material showed no anhydride peaks.

Preparation of Tethered m-MOST-ol photoinitiator (as described in U.S. Patent No. 5,298,361)

A stirred solution of 103 g of 2,4-bis(trichloromethyl)- 1,3, 5 -triazine, 47 g of 3-(2-hydroxyethoxy)benzaldehyde), and 10.5 g of ammonium acetate in 270 mL of methanol was refluxed for 12 hours. After the mixture had cooled, an additional 80 mL of methanol was added, followed by 112 mL of water. The resultant precipitate was filtered and dried to yield 74 g of 2,4-bis(trichloromethyl)-6-[3-(2- hydroxyethoxy)styryl]- 1 ,3 , 5-triazine (m-MOST-ol).

To a stirred dispersion containing 55.00 g of m-MOST-ol and 18.2 g of 2,4-tolylene diisocyanate in 200 mL of toluene at 16°C was added 0.150 g of dibutyltin dilaurate. A slight exotherm raised the temperature ofthe reaction mixture to 19°C and the reaction mixture became clear after approximately 20 minutes. The m-MOST-ol had completely reacted in 5 hours and the resulting mixture of m-MOST-ol TDI, (m-MOST-ol)₂/TDI and residual 2,4-tolylene diisocyanate. To this mixture was added 58.92 g of a 79.2% solution of polyoxyethylene nonylphenol (Igepal™ CO-520, available from GAF Chemicals Coφ., Wayne, NJ) in toluene and the solution was heated to 60°C and maintained at that temperature for 4 hours. Removal of thi. toluene under vacuum by means of a rotary evaporator provided a slightly brown viscous syrup. The material was redissolved in sufficient methyl ethyl ketone to produce a solution having a concentration of approximately 50% total solids.

Acrylated Urethane Oligomer P-l 1 (as described in U.S. Patent No. 4,304,923)

Polycaprolactone hexol was prepared by adding 63.5 g dipentaerythritol, 228 g of epsilon-caprolactone, and 0.02 g of 2,6-di-t-butyl-4-methylphenol to a 500 mL, three-neck flask equipped with an overhead mechanical stirrer and a condenser. The liquid was deoxygenated for 20 minutes by bubbling with dry nitrogen from a gas dispersion tub. This tube was then replaced with a gas inlet adapter and the reaction mixture heated while maintaining a slight positive pressure with nitrogen. The mixture was maintained at 170°C for 5 hours under continual stirring. The reaction mixture was then allowed to cool to room temperature under nitrogen atmosphere. A 1 liter three-neck flask was fitted with an adapter, mechanical stirrer, thermometer, addition funnel and drying tube. To this flask was charged 175 g of the polycaprolactone hexol and 60 mL of methyl ethyl ketone. A solution of 13 g of 2,4-tolylene diisocyanate in 9 mL of methyl ethyl ketone was slowly dripped into the first solution with stirring at room temperature. The addition was completed in 20 minutes and the reaction mixture stirred for 90 minutes at 30°C.

To a second flask fitted with an overhead mechanical stirrer, thermometer, addition funnel and drying tube was charged 86.1 g of 2,4-tolylene diisocyanate. Through the addition funnel was added 70.2 g of 2-hydroxyethylmethacrylate (HEMA) and 0.02 g of 2,6-di-t-butyl-4-methylphenol (inhibitor) slowly with stirring to the diisocyanate while maintained below or at 30°C. The addition was completed in 15 minutes and after 40 minutes of reaction time, a white solid formed. The solid was dissolved in 45 mL of methyl ethyl ketone by heating to 45°C and held at that temperature for 10 minutes to complete the reaction.

The flask containing the reaction product ofthe polycaprolactone hexol and the 2,4-tolylene diisocyanate was heated to 67°C and the solution ofthe

HEMA/2,4-tolylene diisocyanate adduct in methyl ethyl ketone was added slowly with stirring over a period of 2 hours. 27 g of succinic anhydride was then added with an additional 0.02 g ofthe inhibitor. Heating and stirring was continued until the anhydride had completely reacted (about 5-6 hours).

Polymethacrylate Beads containing Optical Brightener

An aqueous solution of 700 g of deionized water, 16.6 g of Ludox™ TM colloidal silica (50% solution; available from I.E. DuPont de Nemours, Wilmington, DE), 0.50 g ofN, N, N', N'-tetramethyl ethylene diamine, and 0.16 g of potassium dichromate was stirred and adjusted to pH 4 by addition of 10% sulfuric acid. A solution of 456 g of methylmethacrylate monomer, 8.6 g of trimethylolpropane trimethacrylate, 1.4 g of Vazo™ 64 (azobisisobutylnitrile initiator, (available from I.E. DuPont de Nemours Chemicals, Wilmington, DE) and 14.4g Uvitex™ OB (optical brightener, available from Ciba Geigy, Hawthorne, NY) were added to the above aqueous mixture and then stirred at 1500 φm for 2 minutes. The mixture was then passed through a Manton-Gaulin homogenizer three times at an internal pressure of 700 psi, then poured into a reaction flask which was purged with nitrogen, and stirred at 60°C overnight. The contents were then collected in a Buchner funnel fitted with #54 filter paper, followed by washing several times with water to yield a wet cake containing about 78% by weight beads. The resultant polymeric beads contain approximately 3% by weight optical brightener. Under magnification, more than 90% ofthe beads appeared to be in a range from 10-20 microns, with an average particle diameter of approximately 19 microns.

Standard Millbases and Coating Solutions

The following standard millbases and coating solutions were used in the

Examples.

Release Layer Coating Solution:

Airvol™ 205 Polyvinyl alcohol 5.6 g (available from Air Products and Chemicals,

Allentown, PA) Airvol™ 107 Polyvinyl alcohol 2.4 g

(available from Air Products and Chemicals, Allentown, PA) Triton™ X-100 (octylphenoxypolyethoxyethanol, 0.2 g available from Rohm and Haas, Philadelphia, PA) Kathon™ CG/ICP Preservative 0.09 g

(available from Rohm and Haas, Philadelphia, PA) Deionized Water 91.7 g

Millbases:

Ingredients Black Green Red Shade Shade Cyan Cyan

Raven 760 (available from 8.3 g Columbian Chemicals Co., Tulsa, OK)

Sun 249-0592 Green Shade Cyan (available 8.72 g from Sun Chemical, Cincinnati, OH)

Sun 248-0615 Red Shade Cyan (available from Sun 8.72 g Chemical, Cincinnati, OH)

Acidified Butvar™ B-98 1.483 g 2.9 g 2.9 g

Jonciyl™ 67 4.43 g 2.9 g 2.9 g (styrene/acrylic resin available from S.C. Johnson Wax, Racine, WI)

Disperbyk™ 161 0.75 g 0.436 g 0.436 g (available from Byk- Chemie USA, Wallingford, CT)

FC-430 (fluorochemical .033 g 0.03 g 0.03 g surfactant, available from 3M, St. Paul, MN)

Methyl ethyl ketone 59.5 g 59.5 g 59.5 g

Propyleneglycol 25.5 g 25.5 g 25.5 g monomethyl ether

Photosensitive Color Layer Coating Solution

Green Shade Cyan Millbase 10.6 g

Red Shade Cyan Millbase 7.04 g

Black Millbase 0.41 g

Acrylated urethane oligomer P-l 1 (described in U.S. 51.03 g

Patent No. 4,304,923) Echo™ 310 (novolac diacrylate resin, available from

Echo Resins and Laboratory, Versailles, MO ) 8.98 g Joncryl™ 67 (styrene/acrylic acid res , available from

Johnson Wax, Racine, WI ) 12.16 g Acidified Butvar B-98 5.04 g

Tethered m-MOST-ol photoinitiator 4.74 g

FC-430 (fluorinated surfactant, available from 3M, 0.04 g

St. Paul, MN)

Methyl ethyl ketone 560 g

Propylene glycol monomethyl ether 240 g

Photopolymerizable Barrier Layer Coating Solution

Echo™ 310 (novolac diacrylate resin, 2.9 g available from Echo Resins and Laboratory,

Versailles, MO)

Joncryl™ 586 (styrene/acrylic resin, available 2.0 g from S.C. Johnson Wax, Racine, WI)

Tethered m-MOST-ol photoinitiator 0.1 g

Methyl ethyl ketone 95.0 g

Example 1

The following example illustrates the use of transparent polymeric beads containing an optical brightener in the adhesive layer of a color proof construction. An adhesive coating solution was prepared by combining the following ingredients:

DL-0777 Acrylic latex adhesive (37% T.S. available from Reichhold Chemical Co., Dover, DE) 1000 g FC 129 (fluorochemical surfactant, available from

3M, St. Paul, MN) 0.5 g

Polymethacrylate beads containing Uvitex™ OB 1.15 g

(slurry containing about 80% beads)

The fluorochemical surfactant was added to the acrylic latex adhesive followed by the polymeric beads with continuous stirring. The adhesive solution was coated onto 2 mil (0.051 mm) polyester film using a #10 wire wound bar. The coating was dried at 90°C for 5 minutes.

The adhesive coated polyester film was laminated to a Matchprint™ Commercial Color Proofing Base (available from 3M, St. Paul, MN) using heat and pressure. The polyester support was then removed leaving the adhesive coating on the Matchprint™ base surface. The adhesive layer was illuminated using a Minerallight™ UVSL 25 hand-held ultraviolet light source available from Ultraviolet Products, Inc., San Gabriel, CA. The polymeric beads in the adhesive appeared as bright spots under the ultraviolet light at both the long (366 nm) and short (254 nm) wavelength settings. The background area absent beads also exhibited some slight fluorescence, possibly due to some residual optical brightener in the water phase ofthe bead slurry.

Example 2 The following example illustrates the use of transparent polymeric beads containing an optical brightener incoφorated into a cyan color proofing element.

This cyan element is then used to construct a four color proof composite.

A cyan color proofing element was constructed by first coating and drying a release layer onto a 2 mil (0.051 mm) polyester substrate to achieve a dry coating weight of about 1 g/m². The photosensitive cyan color layer solution was then coated and dried onto the release layer at a density of 1.3 measured with a Gretag

SPM- 100 spectrophotometer. The photopolymerizable barrier solution was then applied at a dry coating weight of approximately 32 mg/ft² (0.34 g/m²).

An adhesive coating solution was prepared with polymethacrylate beads containing Uvitex™ OB incoφorated into the solution. Before adding the beads to the adhesive, a 50 g sample of polymethacrylate beads containing Uvitex™ OB were added to 150 mL of distilled water. The mixture was stirred and filtered with suction using a water aspirator. This procedure was repeated eight additional times.

The water washed polymeric beads were added to 6.7 Kg of DL-0777 acrylic latex adhesive (37% T.S. available from Reichhold Chemical Co., Dover,

DE) with stirring. The adhesive solution was coated and dried on the photopolymerizable barrier layer at a dry coating weight of 700 mg/ft². The dried adhesive layer contained approximately 0.02% by weight ofthe polymeric beads. A four color proof was then made by first laminating the cyan color proofing element containing the polymeric beads with optical brightener. The polyester carrier was removed, the laminated film was then exposed with a UV light source having a power output of 0.15 Watt/cm² through a color separation negative. The imaged film was then developed using a developer comprising 1% potassium carbonate, 1% potassium bicarbonate and 0.1% Surfynol™ 465 (ethoxylated tetramethyldecynediol surfactant, available from Air Products) in water.

Additional Matchprint™ negative magenta, yellow and black films (available from 3M, St. Paul, MN) were then sequentially laminated, exposed and developed to provide a four color proof composite. The Matchprint™ negative films are essentially the same basic construction as the cyan color proofing element described above with different colorants. A comparative four color proof was also made using all four commercially available Matchprint™ colored films containing no beads with optical brightener.

When the color proof composite containing the cyan element containing the polymeric beads with optical brightener was viewed with an ultraviolet light source, the polymeric beads were easily detected. The background areas ofthe color proof composite containing the optical bright beads and the comparative proof composite with no optical bright beads were measured for spectral reflectance using a Gretag SPM spectrophotometer. Comparison ofthe spectral reflectance curves (380 to 700 nanometers) ofthe two composite proofs showed no significant differences in color, indicating that the presence ofthe detector beads does not alter the visual appearance ofthe proof.

Reasonable variations and modifications are possible from the foregoing disclosure without departing from either the spirit or scope ofthe invention as claimed.

Claims

What is claimed:

1. A composite color proof comprising a substrate and deposited thereon multiple layers comprising multiple colored images and having fluorescent or phosphorescent transparent polymeric beads deposited upon or incoφorated within at least one of said layers deposited on said substrate.

2. The composite color proof of Claim 1 wherein said fluorescent or phosphorescent transparent polymeric beads are present in the form of an image.

3. The composite color proof of Claim 1 wherein said fluorescent or phosphorescent transparent polymeric beads are present in at least one of said layers deposited on said substrate at a concentration between 0.005% and 5.0% by weight.

4. The composite color proof of Claim 1 wherein said fluorescent or phosphorescent transparent polymeric beads are present in at least one of said layers deposited on said substrate at a concentration between 0.01% and 4.0% by weight.

5. The compositie color proof of Claim 1 wherein said fluorescent or phosphorescent transparent polymeric beads have a mean particle size between 2 and 30 microns.

6. A photosensitive single sheet color proofing element comprising, in order:

(a) a releasable carrier;

(b) a photosensitive color coated layer;

(c) an optional barrier coated layer; and

(d) an adhesive coated layer; wherein fluorescent or phosphorescent transparent polymeric beads are incoφorated into at least one of said coated layers.

7. The photosensitive color proofing element of Claim 6 wherein said photosensitive color coated layer is photoinsolublizable.

8. The photosensitive color proofing element of Claim 6 wherein said photosensitive color coated layer is photosolublizable.

9. The photosensitive color proofing element of Claim 6 wherein said fluorescent or phosphorescent transparent beads are present in the form of an image.

10. The photosensitive color proofing element of Claim 6 wherein said fluorescent or phosphorescent transparent polymeric beads are present in at least one of said coated layers at a concentration between 0.005% and 5.0% by weight.

11. The photosensitive color proofing element of Claim 6 wherein said fluorescent or phosphorescent transparent polymeric beads are present in at least one of said coated layers at a concentration between 0.01% and 4.0% by weight.

12. The photosensitive color proofing element of Claim 6 wherein said fluorescent or phosphorescent transparent polymeric beads have a mean particle size between 2 and 30 microns.

13. A photosensitive single sheet color proofing element comprising, in order:

(a) a releasable carrier;

(b) a photosensitive color coated layer;

(c) an optional barrier coated layer; and

(d) an adhesive coated layer; wherein fluorescent or phosphorescent transparent polymeric beads are deposited upon the surface of at least one of said coated layers.

14. The photosensitive color proofing element of Claim 13 wherein said photosensitive color coated layer is photoinsolublizable.

15. The photosensitive color proofing element of Claim 13 wherein said photosensitive color coated layer is photosolublizable.

16. The photosensitive color proofing element of Claim 13 wherein said fluorescent or phosphorescent transparent polymeric beads are deposited upon said surface of at least one of said coated layers in the form of an image.

17. The photosensitive color proofing element of Claim 13 wherein said fluorescent or phosphorescent transparent polymeric beads are present on said surface of at least one of said coated layers at a concentration between 0.005% and 5.0% by weight.

18. The photosensitive color proofing element of Claim 13 wherein said fluorescent or phosphorescent transparent polymeric beads are present on said surface of at least one of said coated layers at a concentration between 0.01% and 4.0% by weight.

19. The photosensitive color proofing element of Claim 13 wherein said fluorescent or phosphorescent transparent polymeric beads have a mean particle size between 2 and 30 microns.