Thermal transfer printing

Claim 2

A thermal transfer printing sheet comprising a substrate having a coating comprising a binder and at least one azo dye of Formula I: wherein; R is the residue of an active methylene compound; X is hydrogen; halogen; optionally substituted alkyl; optionally substituted aryl or optionally substituted heteroaryl; Y is -S- or a group of the formula > N - R¹ wherein R¹ represents hydrogen or an optionally substituted C₁₋₄-alkyl; and E is the residue of a coupling component.

Claim 3

A thermal transfer printing sheet according to Claim 1 wherein R in the azo dyes is a group of Formula II: wherein: R² is cyano; acetyl; optionally substituted C₁₋₁₀-alkoxy-­carbonyl; optionally substituted C₃₋₈-alkenyloxycarbonyl; C₁₋₄-alkylsulphonyl; optionally substituted phenylsulphonyl; optionally substituted aminocarbonyl; optionally substituted C₁₋₄-alkylamino- carbonyl; optionally substituted di(C₁₋₄-alkyl)aminocarbonyl; optionally substituted phenyl or optionally substituted benzoyl.

Claim 4

A thermal transfer printing sheet according to Claim 1 or claim 2 wherein E in the azo dyes is a group of Formula III: wherein: R³ & R⁴ are independently hydrogen; optionally substituted C₁₋₄-alkyl; C₄₋₈-cycloalkyl; C₃₋₄-alkenyl; phenyl-C₁₋₄-alkyl or phenyl; R⁵ is hydrogen; halogen; C₁₋₄-alkyl; C₁₋₄-alkoxy; C₁₋₄-alkylthio; C₁₋₄-alkylcarbonylamino; phenylcarbonylamino or C₁₋₄-alkylsulphonylamino; and R⁶ is hydrogen; C₁₋₄-alkyl or C₁₋₄-alkoxy.

Claim 5

A thermal transfer printing sheet according to Claim 1 or claim 2 wherein E in the azo dyes is a group of Formula III wherein: R³ & R⁴ are independently hydrogen; C₁₋₄-alkyl; C₄₋₈-cycloalkyl; phenyl or C₁₋₄-alkyl substituted by a group selected from -OH, -CN, halogen, C₁₋₄-alkoxy, C₁₋₄-alkoxy-C₁₋₄-alkoxy, C₁₋₄-alkyl-CO-, C₁₋₄-alkoxy-CO-, C₁₋₄-alkyl-COO-, C₁₋₄-alkoxy-­C₁₋₄-alkoxy-CO-, C₁₋₄-alkoxy-COO- and C₁₋₄-alkoxy-­C₁₋₄-alkyl-COO-; R⁵ is hydrogen; C₁₋₄-alkyl; cyano-C₁₋₄-alkyl; C₁₋₄-alkoxy or -NHCOT¹ wherein T¹ is C₁₋₄-alkyl or phenyl; and R⁶ is hydrogen.

Claim 6

A thermal transfer printing sheet according to any one of Claims 1 to 4 wherein the azo dye is of the Formula V: wherein: R² represents cyano; acetyl and optionally substituted C₁₋₆-alkoxycarbonyl; optionally substituted C₃₋₈alkenyloxycarbonyl; optionally substituted C₁₋₄-alkylsulphonyl; optionally substituted phenylsulphonyl; optionally substituted aminocarbonyl; optionally substituted C₁₋₄-alkylaminocarbonyl; optionally substituted di(C₁₋₄-alkyl)aminocarbonyl; optionally substituted phenyl and optionally substituted benzoyl; X represents hydrogen; halogen; optionally substituted alkyl; optionally substituted aryl and optionally substituted heteroaryl; Y represents -S- and > N - R¹ wherein R¹ is hydrogen or optionally substituted C₁₋₄-alkyl; R³ & R⁴ independently represent H; C₁₋₄-alkyl; phenyl; C₄₋₈-cycloalkyl and C₁₋₄-alkyl substituted by a group selected from OH, CN, halogen, aryl, C₁₋₄-alkoxy, C₁₋₄-alkoxy-C₁₋₄-alkoxy, C₁₋₄-alkyl-CO-, C₁₋₄-alkoxy-CO-, C₁₋₄-alkoxy-COO-, C₁₋₄-alkyl-COO-, C₁₋₄alkoxy-C₁₋₄-alkoxy-CO-; R⁵ represents H; C₁₋₄-alkyl; cyano-C₁₋₄-alkyl; C₁₋₄-alkoxy; -NHCOT¹; wherein T¹ is C₁₋₄-alkyl; or phenyl; and R⁶ represents H; C₁₋₄-alkyl or C₁₋₄-alkoxy.

Claim 7

A thermal transfer printing sheet according to Claim 5 wherein in the azo dye of Formula V: R² is C₁₋₆-alkoxycarbonyl or C₁₋₄-alkoxy-C₁₋₄-alkoxycarbonyl; X is chloro; Y is sulphur; R³ & R⁴ independently are C₁₋₄-alkyl or C₁₋₄-alkoxy-CO-C₁₋₄-alkyl; R⁵ is hydrogen; C₁₋₄-alkyl or -NHCOT¹ wherein T¹ is C₁₋₄-alkyl or phenyl; and R⁶ is hydrogen.

Claim 8

A thermal transfer printing sheet according to Claim 5 wherein in the azo dye of Formula V: R² is ethoxycarbonyl or ethoxyethoxycarbonyl; X is chloro; Y is sulphur; R³ & R⁴ independently are ethyl, butyl, 1-methylpropyl, 2-methylpropyl, acetoxyethyl or acetoxybutyl; R⁵ is methyl or acetylamino; and R⁶ is hydrogen.

Claim 9

A thermal transfer printing sheet according to any one of Claims 1 to 7 wherein the substrate is <20 um in thickness and is capable of withstanding temperatures up to 400°C for up to 20 milliseconds and is selected from paper, polyester, polyacrylate, polyamide, cellulosic and polyalkylene films, metallised forms thereof, including co-polymer and laminated films and laminates incorporating polyester receptor layers.

Claim 10

A thermal transfer printing sheet according to any one of Claims 1 to 8 wherein the binder is any resinous or polymeric material suitable for binding the dye to the substrate.

Claim 11

A thermal transfer printing sheet according to Claim 9 wherein the binder is selected from cellulose derivatives such as ethyl hydroxycellulose, hydroxypropylcellulose, methylcellulose, ethylcellulose, cellulose acetate, cellulose acetate butyrate; carbohydrate derivatives such as starch; alginic acid derivatives; alkyd resins; vinyl resins and derivatives such as polyvinylalcohol, polyvinyl butyral and polyvinyl pyrrolidone; polymers and co-polymers derived from acrylates and acrylate derivatives, such as polyacrylic acid, polymethylmethacrylate and styrene-acrylate co-polymers, polyester resins, polyamide resins, such as melamines; polyurea and polyurethane resins; organosilicones, such as polysiloxanes, epoxy resins and natural resins such as gum tragacanth and gum arabic.

Claim 12

A thermal transfer printing sheet according to any one of Claims 1 to 10 wherein the binder to dye ratio is from 1:1 to 4:1.

Claim 13

A process for the preparation of a thermal transfer printing sheet according to any one of Claims 1 to 11 which comprises applying an ink comprising 0.1 to 10% of the dye and 0.1 to 10% of the binder dissolved or dispersed in a solvent and evaporating the solvent to produce a coating of the dye and binder on the substrate.

Claim 14

A transfer printing process which comprises contacting a transfer sheet according to any one of Claims 1 to 11 with a receiver sheet so that the dye is in contact with the receiver sheet and selectively heating areas of the transfer sheet whereby dye in the heated areas of the transfer sheet may be transferred to the receiver sheet.

Claim 15

A transfer printing process according to Claim 13 wherein the transfer sheet is heated to a temperature from 300°C to 400°C for a period of 1 to 20 milliseconds while in contact with the receiver sheet whereby the amount of dye transferred is proportional to the heating period.

Claim 16

A transfer printing process according to Claim 13 or Claim 14 wherein the receiver sheet is white polyester film.