A composition of the invention which is readily imageable with relatively low-output semi-conductor lasers or a similar light source comprises between about 1 and about 90 weight %, preferably between about 25 and 75 weight % of fine polyacetyleniσ crystals having thermosensitivity at temperatures above 80 ^β C, preferably above 100°C. , and having the formula

R-f-C≡C-3- _n R'

in a binder matrix and a polycarbocyanine dye, or a polycarbocyanine dye mixture, capable of absorbing energy within the 400-1500 nm wavelength range said dye present in an amount sufficient to absorb energy and transmit heat in excess of a critical temperature of the thermochromic polyacetylene, and said polycarbocyanine dye having the formula

wherein n has a value greater than 1, e.g. from 2 to 10, preferably 2; R is a polar hydrophilic moiety containing a radical of the group of amino, amido, hydroxy, ester, ether, phenol, carboxy, halo, sulfonyl, sulfoxy, sulfinyl, silyl, ^" siloxy, phosphoro, phosphate, keto, aldehyde, carbonate, urethane, urea radicals and a metal salt group; R' is hydrogen, alkyl, aryl, aralkyl, alkaryl or is selected from the group defined for R; p has a value of from 2 to 5; R" is hydrogen, lower alkyl, phenoxy, methylate or any of the polycarbocyanine moieties of

compounds disclosed in Volume 6, pages 616-622 of Kirk-Othmer's Encyclopedia of Chemical Technology, Second Edition, Interscience Publishers which absorb energy in the 600-1500 nm wavelength range and X represents any of the terminal moieties disclosed in said Kirk-Othmer's Encyclopedia of Chemical Technology pages 605-622, incorporated herein by reference.

Of the above compositions of thermosensitive polyacetylenic compounds, those dispersed microcrystalline diacetylenes containing an amido, carboxy, hydroxy, ether, urea or urethane radical in a water soluble binder are preferred. Also preferred are water soluble polycarbocyanine dyes of the above formula or their mixtures.

The polycarbocyanine dyes of this invention have an advantage over many other energy absorbing dyes in that most of these compounds are water soluble and therefore require no extraneous solvent when added to aqueous dispersions of the crystalline polyacetylene.

Specific examples of polyacetylenic compounds include

1,6-diamino-l,6-hexadiyne, 2,4-hexadiyn-l,6-bis(n-butyl carbamate) , 2,4-hexadiyn-l,6-bis(cyclohexyl urea) , 1,12-(3,10-dioxa-5,7-dodecadiyndiyl) dibenzoate, 2,5-octadiyn-l,8-bis(n-propyl carbamate) , 3,5-octadiyn-l,8-bis(n-propyl carbamate) , 5,7-dodecadiyn-l,12-bis(isopropyl carbamate) , 5,7-dodecadiyn-l,12-bis(n-butyl carbamate) , 2,4-hexadiyn-l,6-bis(n-propyl urea) , 2,4-hexadiyn-l,6-bis(n-octadecyl urea) , 1,12-dodecadiynediol, 1,20-diethylhydroxy cosadiyne, 4,6-decadiyn-l,10-bis(naphthanyl carbamate) , 2,4-hexadiyn-l,6-bis(isopropyl carbamate) ,

1,10-di(hydroxyphenyl) decadiyne, 10,12-pentacosadiynoic acid, 4,6-decadiynoic acid, 11,13-tetraσosadiynoic acid, 10,12-docosadiynoic acid, the mono- and di- alkyl esters and dibenzyl esters of the foregoing acids; salts of the foregoing acids and any of the crystalline polyacetylenes or polyacetylene derivatives disclosed in U.S. 3,501,303; U.S. 4,215,208, and U.S. 4,784,934; as well as polymers of triynes, tetraynes and higher polynes and their derivatives and related compounds.

Specific examples of polycarbocyanine dyes suitably employed in the present invention include 1,1'-diethyl-2,2 ^• -tricarbocyanine iodide, 1•-ethyl-3,9-dimethyloxa-2'-tricarbocyanine iodide; 3,3'-diethylthiazolintricarbocyanine iodide; 1,1'-diethyl-4,4•-tricarbocyanine iodide; 3,3'-diethylthiatricarbocyanine iodide; 3,3'-diethyl-9,13-dimethyloxatricarbocyanine iodide; 3 ^» -ethyl-l,3,3-trimethyl-ll,13-neopentyleneindothiatri- carbocyanine iodide;

3,3'-diethylthiapentacarboσyanine iodide; 3,3'-diethylthiatetracarbocyanine iodide; and their corresponding bromide or chloride salts and diethylheptacarbocyanine, 1-cyanotetracarbocyanine, and other di-, tri-, tetra- and pentacarbocyanine dyes having terminal groups selected from thiazol, thiazoline, 3-pyrrole, 4-pyrazole, 2-pyridinie, benzoxazole, benzothiazole, benzoselenazole, benzi idazole, 3H-indole, naphth[2,l-d]oxazole and naphtho[l,2-d]thiazole radicals. Most preferred are the tricarbocyanine dyes which are soluble in water, for example IR-125 supplied by Eastman Kodak Company. The energy absorbing heat transmitting dye can also comprise a mixture of polycarbocyanines as well as

their mixtures with other auxiliary energy absorbing dyes capable of operating in the 600-1500 nm wavelength range, which auxilary dyes may comprise up to 50% of the energy absorbing component of the present compositions.

Examples of other suitable energy absorbing dyes include metal complexes such as diimine iron complex, dithiol nickel complex, indigo, anthraquinone, azulenium, polycarbocyanine, squarylium, indolizinium, naphthalocyanine, naphthoquinone and its analogs, phthalocyanine, poly ethine, pyrylium, thiapyrylium, telluropyrylium, triaryl ammonium, triquinocycloalkane, or the specific dyes disclosed in the Journal of Imaging Science, Volume 32, number 2, March/April 1988, pages 51-56 (ORGANIC ACTIVE LAYER MATERIALS FOR OPTICAL RECORDING by James E. Kuder) ; Chemistry in Britain, November 1986, pages 997-1000 entitled MODERN DYE CHEMISTRY by J. Griffiths; Angewandte Chemie, Volume 28, number 6, June 1989, pages 677-828 (SEARCH FOR HIGHLY COLORED ORGANIC COMPOUNDS by Jurgen Fabian et al.); and Journal of Imaging Technology, Volume 12, Number 3, June 1986, pages 140-143, (ORGANIC MATERIALS FOR OPTICAL DATA STORAGE MEDIA - AN OVERVIEW by James E. Kuder) , all incorporated herein by reference.

As a guide for the selection of an energy absorbing compound in a wavelength similar to transmission of a particular imaging device, the following table provides specific examples of wavelength absorbance.

TABLE

Wavelength Absorption

Aromatic annulenes 768 nm

Al tetraazaporphyrins 1204 nm

Ni dithiolenes 1298 nm

Streptopolymethines 1500 nm

Silenoxantheny1ium 802 n

Azo 778 nm

Indophenols and Analogues 761 nm

Ther ochromic dianthrone 675 nm

Betaines 934 nm

Divinyl benzothiazole 640 nm

Trivinyl benzothiazole 750 nm

Diethyl carbocyanine iodide 700 nm

The polycarbocyanine dyes or their mixtures are preferred as the heat transmitting agents of this invention for the reason that, they possess narrow absorption bands with high extinction coefficients not shared with many of the other energy absorbing compounds mentioned above. Accordingly, significantly smaller amounts of these dyes are needed to provide the desired absorption.

The above compositions are prepared under atmospheric conditions by forming a dispersion, emulsion or suspension, preferably an aqueous dispersion, of from about 0.02 urn to about 5 urn diameter crystals, preferably from 0.1 urn to 1.0 um diameter crystals, of the polyacetylene in a binder to provide a dispersion containing from about 1 to about 50%, preferably from about 4 to about 20% of solid polyacetylenic microcrystals.

Exemplary of binder materials are natural and synthetic plastics, resins, waxes, colloids, gels and the like including gelatins, desirably photographic-grade gelatin, various polysaccharides including dextran, dextrin, hydrophilic cellulose ethers and esters, acetylated starches, natural and synthetic waxes including paraffin, beeswax, polyvinyl-lactams, polymers of acrylic and methacrylic esters and amides, hydrolyzed interpolymers of vinyl acetate and unsaturated -addition polymerizable compounds such as aleic anhydride, acrylic and methylacrylic esters and styrene, vinyl acetate polymers and copolymers and their derivatives including completely and partially hydrolyzed products thereof, polyvinyl acetate, polyvinyl alcohol, polyethylene oxide polymers, polyvinylpyrrolidone polyvinyl acetals including polyvinyl acetaldehyde acetal, polyvinyl butyraldehyde acetal, polyvinyl sodium-o-sulfobenzaldehyde acetal, polyvinyl formaldehyde acetal, and numerous other known photographic binder materials including a substantial number of aforelisted useful plastic and resinous substrate materials which are capable of being placed in the form of a dope, solution, dispersion, gel, or the like for incorporation therein of the thermosensitive polyacetylenic compound and capable of processing to a solid form containing dispersed crystals of the thermosensitive crystalline polyacetylenic compound. Preferable, are those binders that can be applied from an aqueous medium, as a dispersion, emulsion or solution and particularly preferable are water soluble binder materials. As is well known in the art in the preparation of smooth uniform continuous coatings of binder materials, or mixtures of binder materials, there may be employed therewith small amounts of conventional coating aids as viscosity controlling agents, surface active agents, leveling agents dispersing agents and the like.

The polycarbocyanine and dye or dye mixture is added to the aqueous dispersion in an amount sufficient to provide a peak optical density of between about 0.1 and about 3, preferably between about 0.2 and about 2, after which the resulting composition is coated and dried on a substrate. Coatings of the present compositions are applied to a substrate by any of the known techniques, preferably in the form of an aqueous dispersion; although one or more monomolecular layers of the polyacetylene compound can be applied to the substrate as formed by the Langmuir-Blodgette, spin or spray coating methods.

Suitable substrates include polyethylene terephthalate, nylon, polystyrene, cellulose acetate, cellulose nitrate, cellophane, polyvinyl chloride, polyvinylidene chloride, teflon, polychlorotrifluoro- ethylene, polyethylene, polypropylene, paper, ceramic, glass, metal, wood and the like.

The coating composition is applied to the substrate in a thickness of from about 0.02 um to about 100 um, preferably from about 0.1 um to about 5 um or sufficient to produce an optical contrast of at least 1.0 in the image. Application of the composition on the substrate is accomplished by any of the numerous and known techniques. In cases where the dye is not water soluble and an aqueous dispersion of the polyacetylene compound is employed, the dye can be dissolved in a suitable inert solvent such as a ketone, alcohol, benzene and the like for addition to the dispersion. The weight ratio of polyacetylene to dye in the resulting coating mixture can vary from about 1000:1 to about 1:10.

The dried, coated composition is then exposed to laser, or other light emanation which impinges on the coating surface in precise areas of a design consistent with the desired image to create a latent image on the coating composition. In choosing a suitable light source.

e.g. a GaAlAs laser, a xenon arc lamp, a mercury arc lamp, a tungsten-quartz halogen lamp, a YtAl garnet laser, and the like, it is necessary to match the optical absorbance of the polycarbocyanine dye or dye mixture to the wavelength of the light source. For example a laser has an output wavelength of up to 1500 nm, preferably within a range of from about 650 to about 900 nm and a power sufficient to generate heat greater than 80 ^β C, preferably greater than 100°C, in the coating, which presumably deactivates the polyacetylene compound by causing it to undergo a change from its original crystalline solid state to an amorphous solid state after the exposure. Since polyacetylene compounds are generally incapable of absorbing energy much above 400 nm wavelength, they are not directly imageable by the semi-conductor laser or other light source emitting energy above about 400 nm wavelength; hence the dye component is included to absorb energy and to generate heat which is instantly transferred to the thermosensitive polyacetylenic compound.

The latent imaged composition is then given an overall exposure to short wavelength radiation generated from a source such as UV light, electron beam, gamma-ray. X-ray, beta-ray, neutron, alpha-particle and the like to convert the unexposed portion of the coating composition to a color or color intensity which is readily distinguishable from the portion exposed to the light source which remains colorless.

Lasers or other light sources, transmitting energy in the 400-1500 nm output range provide the highest image resolution, which is an important consideration in recording data transmissions. Within the output range of 600 to 900 n , high speed can be achieved as well. For example using a laser beam diameter of 0.5 to 2 um, an exposure time of 180-250 ns/dot and output of 2.5-3.5 mW, a latent image is encoded on the polyacetylene compound

which, when developed to a visual image, has excellent resolution and high color contrast. Generally the speed of recording and image density varies directly with the output power of the laser and the thickness of the polymer coating. Accordingly, thin coatings of from about 0.02 to 100 micrometers, preferably from about 0.1 to 5 micrometer are recommended, whereupon the optical density change, developed by short wavelength exposure within the imaged area, is from about 1.0 to greater than 5.0 density units and preferably from about 1.5 to about 4.5 density units.

It is desirable, for example, when recording visual images for use as master artwork in the graphic arts or printed circuit board industries, to select a polyacetylenic compound which, when subjected to short wavelength radiation, undergoes a thermochromic change dramatically altering the absorption of blue light (e.g. a blue to yellow thermochromic change) since this change will provide the highest contrast for duplication to other recording photosensitive recording media, particularly those containing photopolymers, sensitive to blue and ultraviolet light as are commonly employed in commercial photolithographic printing plates and etch resists used in the preparation of printed board circuits. However, polyacetylenes which are converted to other contrasting hues or hue intensities in the red, magenta, green, brown, blue and other color spectra all provide good image definition.

The types of laser which are suitably employed with the present composition include compact semi-conductor, solid state, gas, metal-vapor, and dye lasers. However, semi-conductor diode lasers or solid state lasers are preferred and semi-conductor diode lasers are most preferred.

The techniques of short wavelength exposure to develop the latent image are well known, thus further amplification is not required. However, for illustrative purposes, it is preferable to choose an exposure source capable of supplying high power to the imageable layer and to employ exposures of between about 1 uJ/cm ² to about 10 J/cm ² .

EXAMPLE 1

In a glass beaker, 15 g. of pentacosa-10,12-diynoic acid was dissolved in 15 g. of n-butanol at 50°C. and this solution was filtered to provide Solution A.

A second solution, Solution B, was prepared by dissolving 15 g. of a deionized photographic gelatin and 0.6 g. of ALKANOL XC^ ¹ ) in 250 g. of water. Solution B was heated to 75°C. and introduced into a high shear blender. While mixing at high speed, Solution A, at 50°C. , was added to Solution B over a period of about 30 seconds and mixing was continued for an additional 2 minutes. The mixture was cooled to 40°C. and then poured into stainless steel containers and chill set at about 4°C. The resulting gelled dispersion was then placed in a vacuum oven at about 20°C. and evacuated to about 5 torr pressure for sufficient time to undergo a 60 g. weight loss at which time n-butanol was removed. The gelled dispersion was then reconstituted by melting at 40°C. and adding 60 g. of water to replace the liquid lost in drying.

1. an alkyl naphthalene sulfonate, supplied by E. I. duPont

EXAMPLE 2

Sample A was prepared by coating the reconstituted dispersion of Example 1 on 3 mil polyester film base to provide a layer having a dry thickness of about 1.5 um. Sample B was prepared by dissolving 0.1 g. of IR-125^ ² ) dye in 100 g. of the reconstituted dispersion of Example 1 and coating this mixture on 3 mil polyester film base to provide a dry coating having a thickness of about 1.5 um.

2. a polycarbocyanine dye supplied by Eastman Kodak Company

EXAMPLE 3

A portion of Sample A was exposed to the emission from a GaAlAs semi-conductor diode laser with a wavelength of about 830 nm. The laser emission was focused onto the surface of the Sample and scanned across the surface at the rate of about 300 cm/sec. The power output of the laser was varied in order to expose different portions of the Sample to various energies in the range of from about 10 mJ/cm ² to about 1 J/cm ² .

When the exposed Sample was inspected, no marks or patterns could be discerned, nor were any markings observed after the Sample was subsequently exposed to short wavelength UV radiation sufficient to turn the Sample to a uniform blue color.

EXAMPLE 4

When the laser exposure process of Example 3 was repeated on a portion of Sample B, again no marks could be discerned from the laser transmitted light. However, when the Sample was subsequently exposed to short wavelength UV radiation the image of the original laser exposure could be seen as colorless areas against a blue background with a visual contrast exceeding 1.5 du. The markings were evident at exposures equal to or greater than about 50 mJ/cm ² . These markings were extremely well defined and of very high resolution and edge acuity, indicating that the Sample and imaging process were suitable for high resolution imaging or digital data recording.

Inspection of the laser produced markings under a 400 x magnification revealed the presence of closely spaced fine features considerably less than 1 um in width indicating a resolution in excess of 1000 lines/mm.