Recording sheets containing purine, pyrimidine, benzimidazole, imidazolidine, urazole, pyrazole, triazole, benzotriazole, tetrazole, and pyrazine compounds

Abstract: A recording sheet which comprises a substrate and a material selected from the group consisting of purine compounds, pyrimidine compounds, benzimidazole compounds, imidazolidine compounds, urazole compounds, pyrazole compounds, triazole compounds, benzotriazole compounds, tetrazole compounds, pyrazine compounds, and mixtures thereof. Also disclosed is a recording sheet which consists essentially of a substrate, at least one material selected from the group consisting of purine compounds, pyrimidine compounds, benzimidazole compounds, imidazolidine compounds, urazole compounds, pyrazole compounds, triazole compounds, benzotriazole compounds, tetrazole compounds, pyrazine compounds, and mixtures thereof, an optional binder, an optional antistatic agent, an optional biocide, and an optional filler.

Description: The present invention is directed to recording sheets, such as transparency materials, filled plastics, or papers. More specifically, the present invention is directed to recording sheets particularly suitable for use in ink jet printing processes. The present invention is also directed to ink jet printing processes using said recording sheets. EP-A-0 280 650 and GB-A-2 088 777 disclose recording sheets for ink jet printing processes using phenyl benzotriazole derivatives as additives. The benzotriazole compounds used in the recording sheet of the present invention are not N-phenyl substituted. US-A-4 620 197 is concerned with an ink jet recording method using a recording sheet which contains as the cationic fluorescent agent, amongst others, benzimidazole derivatives. JP-A-62 221 591 describes an ink jet recording sheet with a polymeric coating layer which is mainly composed of an ester acrylate copolymer having a cationic group hardened by UV irradiation. As the UV crosslinking initiator, a triazole compound may be used. JP-A-61 177 279 is related to a recording medium wherein pyrimidine compounds of the general formula III and IV bearing a thio group are incorporated. While known compositions and processes are suitable for their intended purposes, a need remains for improved recording sheets. In addition, there is a need for improved recording sheets suitable for use in ink jet printing processes. Further, a need remains for recording sheets which exhibit rapid drying times when imaged with aqueous inks. Additionally, there is a need for recording sheets which enable precipitation of a dye from a liquid ink onto the sheet surface during printing processes. A need also remains for recording sheets which are particularly suitable for use in printing processes wherein the recorded substrates are imaged with liquid inks and dried by exposure to microwave radiation. Further, there is a need for recording sheets coated with a discontinuous, porous film. There is also a need for recording sheets which, subsequent to being imaged with an aqueous ink, exhibit reduced curling. It is the object of the present invention to provide recording sheets with the above noted advantages, and to provide ink jet printing processes using said recording sheets. This object has been achieved with a recording sheet which comprises a substrate, for example paper or a transparent polymeric material, and an additive material present on the substrate selected from the group consisting of purine compounds, pyrimidine compounds, benzimidazole compounds, imidazolidine compounds, urazole compounds, pyrazole compounds, triazole compounds, benzotriazole compounds, tetrazole compounds, pyrazine compounds, and mixtures thereof; wherein the benzotriazole compounds are selected from the formula wherein R 1 , R 2 , R 3 and R 4 each, independently of one another, are hydrogen, alkyl, substituted alkyl or hydroxyl; the benzimidazole compounds are selected from the group consisting of (1) benzimidazole; (2) 2-aminobenzimidazole; (3) 2-amino-5,6-dimethlybenzimidazole; (4) 5-benzimidazole carboxylic acid; (5) 2,4,5-trimethyl benzimidazole; (6) 2-guanidinobenzimidazole; (7) 2-hydroxybenzimidazole; (8) 4-(2-keto-1-benzimidazolinyl) piperidine; and mixtures thereof; the pyrimidine compounds are selected from the general formula wherein R 1 , R 2 , R 3 and R 4 each, independently of one another, are hydrogen, alkyl, substituted alkyl, halide, nitro, hydroxyl, amino, nitroso, mercaptyl, thio, sulfanilamide, carboxyl, oxo, monosaccharide, oligosaccharide; or wherein one or more of the ring double bonds is saturated and/or wherein one or both of the ring nitrogen atoms is bonded to a substituent and/or wherein one or more of the ring carbon atoms has a double bond to another atom such as carbon, oxygen, or sulfur, or wherein two or more substituents are joined together to form another ring, with the proviso that R 1 , R 4 or R 2 does not represent a thio group. The present invention provides also an ink jet printing process comprising (a) applying an aqueous recording liquid in an imagewise pattern to a recording sheet according to any of claims 1 to 9; or (b) (1) incorporating a recording sheet according to any of claims 1 to 9 into an ink jet printing apparatus containing an aqueous ink, and (2) causing droplets of the ink to be ejected in an imagewise pattern onto the recording sheet thereby generating images on the recording sheet. The recording sheet of the present invention may contain an optional binder, an optional antistatic agent, an optional biocide, and an optional filler. Any suitable substrate can be employed. Examples include transparent materials, such as polyester, and the like, with polyester such as Mylar™ being preferred in view of its availability and relatively low cost. The substrate can also be opaque, including opaque plastics, such as Teslin™, available from PPG Industries, and filled polymers, such as Melinex®, available from ICI. Filled plastics can also be employed as the substrate, particularly when it is desired to make a "never-tear paper" recording sheet. Paper is also suitable, including plain papers such as Xerox® 4024, diazo papers, or the like. The substrate can be of any effective thickness. Typical thicknesses for the substrate are from 50 to 500 µm, and preferably from 100 to 125 µm, although the thickness can be outside these ranges. Situated on the substrate of the present invention is a material selected from the group consisting of purine compounds, pyrimidine compounds, benzimidazole compounds, imidazolidine compounds, urazole compounds, pyrazole compounds, triazole compounds, benzotriazole compounds, tetrazole compounds, pyrazine compounds, and mixtures thereof as disclosed in Claim 1 of the present application. Purine compounds are of the general formula wherein R 1 , R 2 , R 3 , and R 4 each, independently of one another, can be (but are not limited to hydrogen, alkyl, substituted alkyl (such as alkyl hydroxyl or the like), monosaccharide, oligosaccharide, hydroxyl, amine, imine, halide, mercapto, alkoxy, oxo, furfuryl amino, or the like. Other variations are also possible, however, such as wherein substituents are bonded to one or more of the nitrogen atoms in the six-membered ring and the double bonds are rearranged, and/or wherein one of the ring carbon atoms has a double bond to another atom, such as carbon, oxygen, or nitrogen, or the like. Examples of suitable purine compounds include (1) purine (Aldrich P5,580-5), of the formula: (2) 6-amino purine (adenine) (Aldrich 10,496-5), of the formula: (3) 6-methoxy purine hemihydrate (Aldrich 85,270-8), of the formula: (4) 6-mercaptopurine monohydrate (Aldrich 85,267-8), of the formula: (5) 2-amino-6-chloropurine (Aldrich 10,978-9), of the formula: (6) 2-amino-6,8-dihydroxy purine (Aldrich 12,291-2), of the formula: (7) theophylline (3,7 dihydro-1,3-dimethyl-1H-purine-2,6-dione) (Aldrich 26,140-8), of the formula: (8) kinetin (6-furfuryl amino purine) (Aldrich 85,264-3), of the formula: (9) 1-methyl adenine (Aldrich 21,532-5), of the formula: (10) 3-methyl adenine (Aldrich 28,087-9), of the formula: (11) (-)-adenosine (Aldrich 14,659-5), of the formula: (12) (-)-inosine (Aldrich l-640-7), of the formula: (13) 6-mercaptopurine riboside (Aldrich 85,268-6), of the formula: Included within the class of purine compounds are purine salt compounds, which are of the same general formula as purine compounds except that they are associated with compounds of the formula xH n Y n- , wherein n is an integer of 1, 2, or 3, x is a number indicating the relative ratio between pyrrole or pyrrolidine and acid (and may be a fraction), and Y is an anion, such as Cl - , Br - , I - , HSO 4 - , SO 4 2- , NO 3 - , HCOO - , CH 3 COO - , HCO 3 - , CO 3 2- , H 2 PO 4 - , HPO 4 2- , PO 4 3- , SCN - , BF 4 - , ClO 4 - , SSO 3 - , CH 3 SO 3 - , or CH 3 C 6 H 4 SO 3 - , as well as mixtures thereof. Examples of suitable purine salt compounds include (1) 6-amino purine hydrochloride hemihydrate (Aldrich 27,193-4), of the formula: (2) 6-amino purine sulfate (Aldrich 14,581-5), of the formula: (3) 2,6-diamino-8-purinol hemisulfate monohydrate (Aldrich 11,187-2), of the formula: Pyrimidine compounds are those of the general formula wherein R 1 , R 2 , R 3 , and R 4 each, independently of one another, are hydrogen, alkyl, substituted alkyl (such as hydroxy alkyl, or the like), halide, nitro, hydroxyl amino, nitroso, mercaptyl, thio, sulfanilamide, carboxyl, oxo, monosaccharide, or oligosaccharide. Other variations are also possible, such as wherein one or more of the ring double bonds is saturated, and/or wherein one or both of the ring nitrogen atoms is bonded to a substituent, and/or wherein one or more of the ring carbon atoms has a double bond to another atom such as carbon, oxygen, or sulfur, or wherein two or more substituents are joined together to form another ring, with the proviso that R 1 , R 2 or R 4 do not represent a thio group. Examples of suitable pyrimidine compounds include (a) amino pyrimidines, such as (1) 2-amino pyrimidine (Aldrich A7,860-8), of the formula: (2) 2-amino-4-methyl pyrimidine (Aldrich A6,570-0), of the formula: (3) 2-amino-5-nitropyrimidine (Aldrich A7,083-6), of the formula: (4) 2-amino-5-bromopyrimidine (Aldrich 30,352-6), of the formula: (5) 2-amino-4-chloro-6-methyl pyrimidine (Aldrich A4,600-5), of the formula: (6) 2-amino-4,6-dimethyl pyrimidine (Aldrich A5,200-5), of the formula: (7) 2-amino-4-hydroxy-6-methyl pyrimidine (Aldrich A5,800-3), of the formula: (8) 2-amino-4,6-dichloropyrimidine (Aldrich A4,860-1), of the formula: (9) 2-amino-5-bromo-6-methyl-4-pyrimidinol (Aldrich 20,520-6), of the formula: (10) 4-aminopyrimidine (Aldrich 26,182-3), of the formula: (11) 4,5-diamino pyrimidine (Aldrich D2,450-1), of the formula: (12) 4-amino-2,6-dimethyl pyrimidine (Aldrich 18,675-9), of the formula: (13) 2,4-diamino-6-hydroxypyrimidine (Aldrich D1,920-6), of the formula: (14) 2,6-diamino-4-chloro pyrimidine (Aldrich C3,320-4), of the formula: (15) 4,6-diamino-2-mercaptopyrimidine hemihydrate (Aldrich 12,580-3), of the formula: (16) 2,4,6-triamino pyrimidine (Aldrich T4,580-2), of the formula: (17) 5-nitroso-2,4,6-triamino pyrimidine (Aldrich 19,420-4), of the formula: Also suitable are (b) hydroxy pyrimidines, such as(1) 4,6-dihydroxy pyrimidine (Aldrich D12,040-5), of the formula: (2) 4,6-dihydroxy-2-amino pyrimidine (Aldrich A5,040-1), of the formula: (3) 4,6-dihydroxy-2-methyl pyrimidine (Aldrich D11,525-8), of the formula: (4) 4,6-dihydroxy-5-nitropyrimidine (Aldrich 12,623-3), of the formula: (5) 2,4-dihydroxy-5-methyl pyrimidine (Aldrich 13,199-7), of the formula: (6) 2,4-dihydroxy-6-methyl pyrimidine (Aldrich D 11,520-7), of the formula: (7) 2,4-dihydroxy-5,6-dimethyl pyrimidine (Aldrich 16,536-0), of the formula: (8) 2,6-dihydroxy pyrimidine-5-carboxylic acid hydrate (Aldrich 27,770-3), of the formula: (9) 2,6-dihydroxy-4-amino pyrimidine (Aldrich A5,060-1), of the formula: (10) 2,4,5-trihydroxy pyrimidine (Aldrich T6,670-2), of the formula: Also suitable are (c) pyrimidine dione compounds, of the general formula wherein R 1 , R 2 , R 3 , and R 4 each, independently of one another, can be (but are not limited to) hydrogen, alkyl, substituted alkyl (such as hydroxy alkyl, or the like), halide, nitro, hydroxyl, amino, nitroso, mercaptyl, thio, sulfanilamide, carboxyl, oxo, monosaccharide, or oligosaccharide. Other variations are also possible, such as hydrogenation of the ring double bond, Examples of suitable pyrimidine dione compounds include (1) 2,4 (1H,3H)-pyrimidine dione (uracil) (Aldrich 13,078-8), of the formula: (2) 5-amino uracil (Aldrich 85,528-6), of the formula: (3) 5-nitrouracil (Aldrich 85,276-7), of the formula: (4) 5-iodouracil (Aldrich 85,785-8), of the formula: (5) 5-(hydroxymethyl) uracil hydrate (Aldrich 85,258-9), of the formula: (6) 5,6-dihydrouracil (Aldrich 21,964-9), of the formula: (7) 6-amino-1-methyl uracil (Aldrich 34,679-9), of the formula: (8) 5,6-diamino-1,3-dimethyl uracil hydrate (Aldrich D,1590-1), of the formula: (9) uridine (Aldrich U288-1), of the formula: (10) 5-methyl uridine (Aldrich 28,669-9), of the formula: (11) 5-iodouridine (Aldrich 85,259-7), of the formula: (12) thimidine (Aldrich 85,500-6), of the formula: Also suitable are (d) thiouracil compounds, such as (2) 5-methyl-2-thiouracil (Aldrich 23,346-3), of the formula: (4) 4-thiouridine (Aldrich 28,729-6), of the formula: (5) 2-thiocytidine dihydrate (Aldrich 86,083-2), of the formula: Also suitable are (e) orotic acid compounds, such as (1) orotic acid monohydrate (Aldrich 0-840-2), of the formula: (2) L-hydroorotic acid (Aldrich 28,559-5), of the formula: (3) 5-aminoorotic acid (Aldrich 19,121-3), of the formula: (4) methylorotate (orotic acid methyl ester) (Aldrich 22,478-2), of the formula: Also suitable are (f) pyrimidine trione compounds, such as(1) barbituric acid (Aldrich B20-8), of the formula: (2) 5-nitrobarbituric acid trihydrate (Aldrich N1,070-5), of the formula: (3) violuric acid monohydrate (Aldrich 26,083-5), of the formula: (4) alloxan monohydrate [2,4,5,6-(1H,3H)-pyrimidine-tetrone] (Aldrich 23,437-0), of the formula: (5) 1-methyl uric acid (Aldrich 36,023-6), of the formula: Also suitable are (g) guanine compounds, including (1) guanine (Aldrich G1,195-0), of the formula: (2) guanosine hydrate (Aldrich G1,200-0), of the formula: Also suitable are (h) xanthine compounds, including (1) xanthine (Aldrich 10,954-1), of the formula: (2) 1-methylxanthine (Aldrich 28,098-4), of the formula: (3) 3-methyl xanthine (Aldrich 22,252-6), of the formula: (4) 3-isobutyl-1-methyl xanthine (Aldrich 85,845-5), of the formula: (5) hypoxanthine (Aldrich H6,120-0), of the formula: (6) xanthosine dihydrate (Aldrich 22,334-4), of the formula: (7) 6-thioxanthene (Aldrich 85,257-0), of the formula: Also suitable are (i) pyrazole pyrimidines, including (1) 4-hydroxypyrazolo [3,4-d] pyrimidine (Aldrich H5,660-6), of the formula: (2) 4-mercapto-1H-pyrazolo-[3,4-d]-pyrimidine (Aldrich 15,306-0), of the formula: Also suitable are (j) pyrimidine acids and their salts, including (1) folic acid dihydrate (Aldrich 23,587-3), of the formula: (2) folinic acid, calcium salt hydrate (Aldrich 86,189-8), of the formula: Included within the class of pyrimidine compounds are pyrimidine salt compounds, which are of the same general formula as pyrimidine compounds except that they are associated with compounds of the formula xH n Y n- , wherein n is an integer of 1, 2, or 3, x is a number indicating the relative ratio between pyrrole or pyrrolidine and acid (and may be a fraction), and Y is an anion, such as Cl - , Br - , I - , HSO 4 - , SO 4 2- , NO 3 - , HCOO - , CH 3 COO - , HCO 3 - , CO 3 2- , H 2 PO 4 - , HPO 4 2- , PO 4 3- , SCN - , BF 4 - , ClO 4 - , SSO 3 - , CH 3 SO 3 - , or CH 3 C 6 H 4 SO 3 - , as well as mixtures thereof. Examples of suitable pyrimidine salt compounds include (1) 2-hydroxypyrimidine hydrochloride (Aldrich H5,740-8), of the formula: (2) 2-hydroxy-4-methyl pyrimidine hydrochloride (Aldrich H4,320-2), of the formula: (3) 4,6-dimethyl-2-hydroxypyrimidine hydrochloride (Aldrich 33,996-2), of the formula: (4) 2-mercapto-4-methyl pyrimidine hydrochloride (Aldrich M480-5), of the formula: (5) 4,6-diamino pyrimidine hemisulfate monohydrate (Aldrich D2,480-3), of the formula: (6) 4,5,6-triamino pyrimidine sulfate hydrate (Aldrich T4,600-0; 30,718-1), of the formula: (7) 4,5-diamino-6-hydroxy pyrimidine sulfate (Aldrich D1,930-3), of the formula: (8) 2,4-diamino-6-mercapto pyrimidine hemisulfate (Aldrich D1,996-6), of the formula: (9) 2,4-diamino-6-hydroxy pyrimidine hemisulfate hydrate (Aldrich 30,231-7), of the formula: (10) 6-hydroxy-2,4,5-triamino pyrimidine sulfate (Aldrich H5,920-6), of the formula: (11) 5,6-diamino-2,4-dihydroxy pyrimidine sulfate (Aldrich D1,510-3), of the formula: (12) N 4 -(2-amino-4-pyrimidinyl) sulfanilamide monohydrochloride (Aldrich 15,237-4), of the formula: (13) 4,5,6-triamino-2(1H)-pyrimidinethione sulfate (Aldrich 26,096-7), of the formula: (14) 2,4,5,6-tetraamino pyrimidine sulfate (Aldrich T380-7), of the formula: (15) (-)-cyclocytidine hydrochloride (Aldrich 85,883-8), of the formula: (16) cytosine arabinoside hydrochloride (Aldrich 85,585-5), of the formula: The benzimidazole compounds are selected from (1) benzimidazole (Aldrich 11,669-6), of the formula: (2) 2-aminobenzimidazole (Aldrich 17,177-8), of the formula: (3) 2-amino-5,6-dimethlybenzimidazole (Aldrich A5,120-3), of the formula: (4) 5-benzimidazole carboxylic acid (Aldrich 29,678-3), of the formula: (5) 2,4,5-trimethyl benzimidazole (Aldrich T7,400-4), of the formula: (6) 2-guanidinobenzimidazole (Aldrich G1,180-2), of the formula: (7) 2-hydroxybenzimidazole (Aldrich H1,985-9), of the formula: (8) 4-(2-keto-1-benzimidazolinyl) piperidine (Aldrich 12,955-0), of the formula: Imidazolidine compounds are of the general formula wherein R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 each, independently of one another, can be (but are not limited to) hydrogen, alkyl, substituted alkyl (such as alkyl carboxyl or the like), oxo, amino, amide, amino amide, carboxyl, or the like and X is oxygen, sulfur, or nitrogen (imino). Other variations are also possible, such as wherein one or more of the ring carbon atoms has a double bond to another atom such as carbon, oxygen, or sulfur. Examples of suitable imidazolidine compounds include (1) 2-imidazolidine thione (Aldrich l-50-4), of the formula: (2) 2-imidazolidone (Aldrich 1-60-1), of the formula: (3) hydantoin (Aldrich 15,631-1), of the formula: (4) 1-methyl hydantoin (Aldrich M4,988-7), of the formula: (5) creatinine (Aldrich 85,970-2), of the formula: (6) 2-thiohydrantoin (Aldrich T3,040-6), of the formula: (7) 5-hydantoin acetic acid (Aldrich 85,062-4), of the formula: (8) 5-ureidohydantoin (allantoin) (Aldrich A2,839-2), of the formula: (9) 5,5-dimethyl hydantoin (Aldrich D16,140-3), of the formula: (10) 2-imidazolidone-4-carboxylic acid (Aldrich 8,6016-6), of the formula: Urazole compounds are of the general formulae wherein R 1 , R 2 , R 3 , and R 4 each, independently of one another, can be (but are not limited to) hydrogen, alkyl, substituted alkyl, aryl (such as phenyl or the like), substituted aryl (such as phenol or the like), arylalkyl, or substituted arylalkyl. Examples of suitable urazole compounds include (1) urazole (Aldrich U 260-1), of the formula: (2) 1-methyl urazole (Aldrich 27,619-7), of the formula: (3) 4-phenyl urazole (Aldrich 18,895-6), of the formula: (4) D,L-5-(4-hydroxyphenyl)-5-phenyl hydantoin (Aldrich 16,154-3), of the formula: (5) β-tetralone hydantoin (Aldrich B635-2), of the formula: Pyrazole compounds are of the general formula wherein R 1 , R 2 , R 3 , and R 4 each, independently of one another, can be (but are not limited to) hydrogen, alkyl, substituted alkyl (such as hydroxy alkyl or the like), amide, hydroxyl, amino, carboxyl, ester, nitrile, alkoxy, halide, or carboxamidinyl. Examples of suitable pyrazole compounds include (1) pyrazole (Aldrich P5,660-7), of the formula: (2) 4-pyrazole carboxylic acid (Aldrich 30,071-3), of the formula: (3) ethyl 4-pyrazole carboxylate (Aldrich 30,078-0), of the formula: (4) 3,5-pyrazole dicarboxylic acid monohydrate (Aldrich P5,680-1), of the formula: amino pyrazole compounds, such as (5) 3-amino pyrazole (Aldrich 16,064-4), of the formula: (6) 3-amino-5-hydroxypyrazole (Aldrich 33,144-9), of the formula: (7) 3-amino-5-methylpyrazole (Aldrich 34,020-0), of the formula: (8) 3-amino-4-pyrazole carbonitrile (Aldrich 15,304-4), of the formula: (9) 3-amino-4-pyrazolecarboxylic acid (Aldrich A7,740-7), of the formula: (10) 3-amino-4-carbethoxypyrazole (Aldrich A4,500-9), of the formula: (11) 5-amino-1-ethylpyrazole (Aldrich 29,576-0), of the formula: methyl pyrazole compounds and dimethyl pyrazole compounds, such as (12) 4-bromo-3-methyl pyrazole (Aldrich 27,823-8), of the formula: (13) 3,5-dimethyl pyrazole (Aldrich D18,200-1), of the formula: (14) 3,5-dimethyl pyrazole-1-carboxamide (Aldrich D18,220-6), of the formula: (15) 4-bromo-3,5-dimethyl pyrazole (Aldrich B6,440-7), of the formula: (16) 3,5-dimethylpyrazole-1-methanol (Aldrich 33,145-7), of the formula: The class of pyrazole compounds includes pyrazole salts, which are of the same general formula as pyrazole compounds except that they are associated with compounds of the formula xH n Y n- , wherein n is an integer of 1, 2, or 3, x is a number indicating the relative ratio between pyrrole or pyrrolidine and acid (and may be a fraction), and Y is an anion, such as Cl - , Br - , I - , HSO 4 - , SO 4 2- , NO 3 - , HCOO - , CH 3 COO - , HCO 3 - , CO 3 2- , H 2 PO 4 - , HPO 4 2- , PO 4 3- , SCN - , BF 4 - ClO 4 - , SSO 3 - , CH 3 SO 3 - , or CH 3 C 6 H 4 SO 3 - , as well as mixtures thereof. Examples of suitable pyrazole salt compounds include (1) 4-methyl pyrazole hydrochloride (Aldrich 28,667-2) (2) 3,4-diamino-5-hydroxy pyrazole sulfate (Aldrich D1,900-1) (3) (3,5-dimethyl pyrazole-1-carboxamidine nitrate) (Aldrich D18,225-7) (4) 3-amino-4-pyrazole carboxamide hemisulfate (Aldrich 15,305-2) (5) acid salt of 6-amino indazole hydrochloride (Aldrich A5, 955-7) Triazole compounds are of the general formulae wherein R 1 , R 2 , and R 3 each, independently of one another, can be (but are not limited to) hydrogen, alkyl, substituted alkyl (such as mercapto alkyl or the like), amino, mercaptyl, carboxyl, hydrazinyl, aryl, or substituted aryl. Examples of suitable triazole compounds include (1) 1,2,4-triazole (Aldrich T4,610-8), of the formula: (2) 1,2,4-triazole sodium derivative (Aldrich 19,764-5), of the formula: (3) 3-amino-1,2,4-triazole (Aldrich A8,160-9), of the formula: (4) 4-amino-1,2,4-triazole (Aldrich A8,180-3), of the formula: (5) 3,5-diamino-1,2,4-triazole (Aldrich D2,620-2), of the formula: (6) 3-amino-5-mercapto-1,2,4-triazole (Aldrich 14,026-0), of the formula: (7) 3-amino-5-methylthio-1H-1,2,4-triazole (Aldrich 19,068-3), of the formula: (8) 3-amino-1,2,4-triazole-5-carboxylic acid hemihydrate (Aldrich 28,207-3), of the formula: (9) 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (Aldrich 16,289-3), of the formula: (10) 1,2,3-triazole-4,5-dicarboxylic acid monohydrate (Aldrich 26,972-7), of the formula: (11) nitron [4,5-dihydro-2,4-diphenyl-5-(phenylimino)-1H-1,2,4-triazolium hydroxide inner salt] (Aldrich 24,326-4), of the formula: Benzotriazole compounds are of the general formula wherein R 1 , R 2 , R 3 , and R 4 each, independently of one another, are hydrogen, alkyl, substituted alkyl, hydroxyl. Examples of suitable benzotriazole compounds include (1) benzotriazole (Aldrich B1,140-0), of the formula: (2) 1-hydroxybenzotriazole hydrate (Aldrich 15,726-0), of the formula: Tetrazole compounds are of the general formula wherein R 1 and R 2 each, independently of one another, can be (but are not limited to) hydrogen, alkyl, substituted alkyl, or amine. Examples of suitable tetrazole compounds include (1) 1-H-tetrazole (Aldrich 15,569-1), of the formula: (2) 5-amino tetrazole monohydrate (Aldrich A8,060-2), of the formula: Pyrazine compounds are of the general formula wherein R 1 , R 2 , R 3 , and R 4 each, independently of one another, can be (but are not limited to) hydrogen, alkyl, substituted alkyl, carboxyl, amide, hydroxyl, or amine. Other variations are also possible, such as when two or more substituents are joined together to form another ring. Examples of suitable pyrazine compounds include (1) 5-methyl-2-pyrazine carboxylic acid (Aldrich 34,764-7), of the formula: (2) pyrazine amide (Aldrich 13,157-1), of the formula: (3) 2,3-pyrazine dicarboxamide (Aldrich P5,615-1), of the formula: (4) 4-pyridazine carboxylic acid (Aldrich 29,776-3), of the formula: (5) 2,3-pyrazine dicarboxylic acid (Aldrich P5,620-8), of the formula: (6) lumazine monohydrate (Aldrich L 330-7), of the formula: (7) xanthopterin monohydrate (Aldrich X 70-8), of the formula: (8) 2-quinoxazoline carboxylic acid (Aldrich 29,340-7), of the formula: (9) 2-quinoxalinol (Aldrich 26,051-7), of the formula: (10) 2,3-dihydroxy quinoxaline (Aldrich 14,478-9), of the formula: (11) phenazine methosulfate (Kodak 1360155, available from Eastman Kodak Co.), of the formula: Mixtures of any two or more of the above materials can also be employed. The purine compound, pyrimidine compound, benzimidazole compound, imidazolidine compound, urazole compound, pyrazole compound, triazole compound, benzotriazole compound, tetrazole compound, pyrazine compound, or mixture thereof is present in any effective amount relative to the substrate. Typically, the purine compound, pyrimidine compound, benzimidazole compound, imidazolidine compound, urazole compound, pyrazole compound, triazole compound, benzotriazole compound, tetrazole compound, pyrazine compound, or mixture thereof is present in an amount of from 1 to 50 percent by weight of the substrate, preferably from 5 to 30 percent by weight of the substrate, although the amount can be outside this range. The amount can also be expressed in terms of the weight of purine compound, pyrimidine compound, benzimidazole compound, imidazolidine compound, urazole compound, pyrazole compound, triazole compound, benzotriazole compound, tetrazole compound, pyrazine compound, or mixture thereof per unit area of substrate. Typically, the purine compound, pyrimidine compound, benzimidazole compound, imidazolidine compound, urazole compound, pyrazole compound, triazole compound, benzotriazole compound, tetrazole compound, pyrazine compound, or mixture thereof is present in an amount of from 0.8 to 40 grams per square meter of the substrate surface to which it is applied, and preferably from 4 to 24 grams per square meter of the substrate surface to which it is applied, although the amount can be outside these ranges. When the purine compound, pyrimidine compound, benzimidazole compound, imidazolidine compound, urazole compound, pyrazole compound, triazole compound, benzotriazole compound, tetrazole compound, pyrazine compound, or mixture thereof is applied to the substrate as a coating, the coatings employed for the recording sheets of the present invention can include an optional binder in addition to the purine compound, pyrimidine compound, benzimidazole compound, imidazolidine compound, urazole compound, pyrazole compound, triazole compound, benzotriazole compound, tetrazole compound, pyrazine compound, or mixture thereof. Examples of suitable binder polymers include (a) polysaccharides, e.g. hydrophilic polysaccharides and their modifications, (b) vinyl polymers, (c) formaldehyde resins, (d) ionic polymers, (e) latex polymers, (f) maleic anhydride and maleic acid containing polymers, (g) acrylamide containing polymers, and (h) poly(alkyleneimine) containing polymers, where alkylene has two (ethylene), three (propylene), or four (butylene) carbon atoms; as well as blends or mixtures of any of the above, with starches and latexes being particularly preferred because of their availability and applicability to paper. A quartenary acrylic Copolymer latex may also be employed as the binder. Any mixtures of the above ingredients in any relative amounts can be employed. If present, the binder can be present within the coating in any effective amount; typically the binder and the purine compound, pyrimidine compound, benzimidazole compound, imidazolidine compound, urazole compound, pyrazole compound, triazole compound, benzotriazole compound, tetrazole compound, pyrazine compound, or mixture thereof are present in relative amounts of from 10 percent by weight binder and 90 percent by weight purine compound, pyrimidine compound, benzimidazole compound, imidazolidine compound, urazole compound, pyrazole compound, triazole compound, benzotriazole compound, tetrazole compound, pyrazine compound, or mixture thereof to 99 percent by weight binder and 1 percent by weight purine compound, pyrimidine compound, benzimidazole compound, imidazolidine compound, urazole compound, pyrazole compound, triazole compound, benzotriazole compound, tetrazole compound, pyrazine compound, or mixture thereof, although the relative amounts can be outside of this range. In addition, the coating of the recording sheets of the present invention can contain optional antistatic agents. Any suitable or desired antistatic agent or agents can be employed, such as quaternary salts and other materials. The antistatic agent can be present in any effective amount; typically, the antistatic agent is present in an amount of from 1 to 5 percent by weight of the coating, and preferably in an amount of from 1 to 2 percent by weight of the coating, although the amount can be outside these ranges. Further, the coating of the recording sheets of the present invention can contain one or more optional biocides. Examples of suitable biocides include (A) non-ionic biocides, (B) anionic biocides, (C) cationic biocides; as well as mixtures thereof. The biocide can be present in any effective amount; typically, the biocide is present in an amount of from 10 parts per million to 3 percent by weight of the coating, although the amount can be outside this range. Additionally, the coating of the recording sheets of the present invention can contain optional filler components. Fillers can be present in any effective amount, and if present, typically are present in amounts of from 1 to 60 percent by weight of the coating composition. Examples of filler components include colloidal silicas, such as Syloid 74®, available from Grace Company (preferably present, in one embodiment, in an amount of 20 weight percent). The coating containing the purine compound, pyrimidine compound, benzimidazole compound, imidazolidine compound, urazole compound, pyrazole compound, triazole compound, benzotriazole compound, tetrazole compound, pyrazine compound, or mixture thereof is present on the substrate of the recording sheet of the present invention in any effective thickness. Typically, the total thickness of the coating layer (on each side, when both surfaces of the substrate are coated) is from 1 to 25 µm and preferably from 5 to 10 µm, although the thickness can be outside of these ranges. The purine compound, pyrimidine compound, benzimidazole compound, imidazolidine compound, urazole compound, pyrazole compound, triazole compound, benzotriazole compound, tetrazole compound, pyrazine compound, or mixture thereof or the mixture of purine compound, pyrimidine compound, benzimidazole compound, imidazolidine compound, urazole compound, pyrazole compound, triazole compound, benzotriazole compound, tetrazole compound, pyrazine compound, or mixture thereof, optional binder, optional antistatic agent, optional biocide, and/or optional filler can be applied to the substrate by any suitable technique, such as size press treatment, dip coating, reverse roll coating, extrusion coating, or the like. For example, the coating can be applied with a KRK® size press (Kumagai Riki Kogyo Co., Ltd., Nerima, Tokyo, Japan) by dip coating and can be applied by solvent extrusion on a Faustel Coater®. The KRK® size press is a lab size press that simulates a commercial size press. This size press is normally sheet fed, whereas a commercial size press typically employs a continuous web. On the KRK® size press, the substrate sheet is taped by one end to the carrier mechanism plate. The speed of the test and the roll pressures are set, and the coating solution is poured into the solution tank. A 4 liter stainless steel beaker is situated underneath for retaining the solution overflow. The coating solution is cycled once through the system (without moving the substrate sheet) to wet the surface of the rolls and then returned to the feed tank, where it is cycled a second time. While the rolls are being "wetted", the sheet is fed through the sizing rolls by pressing the carrier mechanism start button. The coated sheet is then removed from the carrier mechanism plate and is placed on a 30.5 x 101.6 cm (12 inch by 40 inch) sheet of 750 µm (micron) thick Teflon® for support and is dried on the Dynamic Former® drying drum and held under restraint to prevent shrinkage. The drying temperature is approximately 105°C. This method of coating treats both sides of the substrate simultaneously. In dip coating, a web of the material to be coated is transported below the surface of the liquid coating composition by a single roll in such a manner that the exposed site is saturated, followed by removal of any excess coating by the squeeze rolls and drying at 100°C in an air dryer. The liquid coating composition generally comprises the desired coating composition dissolved in a solvent such as water, methanol, or the like. The method of surface treating the substrate using a coater results in a continuous sheet of substrate with the coating material applied first to one side and then to the second side of this substrate. The substrate can also be coated by a slot extrusion process, wherein a flat die is situated with the die lips in close proximity to the web of substrate to be coated, resulting in a continuous film of the coating solution evenly distributed across one surface of the sheet, followed by drying in an air dryer at 100°C. Recording sheets of the present invention can be employed in ink jet printing processes. One embodiment of the present invention is directed to a process which comprises applying an aqueous recording liquid to a recording sheet of the present invention in an imagewise pattern. Another embodiment of the present invention is directed to a printing process which comprises (1) incorporating into an ink jet printing apparatus containing an aqueous ink a recording sheet of the present invention, and (2) causing droplets of the ink to be ejected in an imagewise pattern onto the recording sheet, thereby generating images on the recording sheet. Ink jet printing processes are well known, and are described in, for example, US-A-4,601,777, US-A-4,251,824, US-A-4,410,899, US-A-4,412,224, and US-A-4,532,530. In a particularly preferred embodiment, the printing apparatus employs a thermal ink jet process wherein the ink in the nozzles is selectively heated in an imagewise pattern, thereby causing droplets of the ink to be ejected in imagewise pattern. in another preferred embodiment, the substrate is printed with an aqueous ink and thereafter the printed substrate is exposed to microwave radiation, thereby drying the ink on the sheet. Printing processes of this nature are disclosed in, for example, US-A-5,220,346. The recording sheets of the present invention can also be used in any other printing or imaging process, such as printing with pen plotters, handwriting with ink pens, offset printing processes, or the like, provided that the ink employed to form the image is compatible with the ink receiving layer of the recording sheet. Recording sheets of the present invention exhibit reduced curl upon being printed with aqueous inks, particularly in situations wherein the ink image is dried by exposure to microwave radiation. Generally, the term "curl" refers to the distance between the base line of the arc formed by recording sheet when viewed in cross-section across its width (or shorter dimension - for example 21.6 cm (8.5 inches) in an 21.6 × 27.9 cm (8.5 × 11 inch) sheet, as opposed to length, or longer dimension - for example, 27.9 cm (11 inches) in an 21.6 × 27.9 cm (8.5 × 11 inch) sheet) and the midpoint of the arc. To measure curl, a sheet can be held with the thumb and forefinger in the middle of one of the long edges of the sheet (for example, in the middle of one of the 27.9 cm (11 inch) edges in an 21.6 × 27.9 cm (8.5 × 11 inch) sheet) and the arc formed by the sheet can be matched against a pre-drawn standard template curve. Specific embodiments of the invention will now be described in detail. These examples are intended to be illustrative, and the invention is not limited to the materials, conditions, or process parameters set forth in these embodiments. All parts and percentages are by weight unless otherwise indicated. The optical density measurements recited herein were obtained on a Pacific Spectrograph® Color System. The system consists of two major components, an optical sensor and a data terminal. The optical sensor employs a 6 inch integrating sphere to provide diffuse illumination and 8 degrees viewing. This sensor can be used to measure both transmission and reflectance samples. When reflectance samples are measured, a specular component may be included. A high resolution, full dispersion, grating monochromator was used to scan the spectrum from 380 to 720 nanometers. The data terminal features a 30.5 cm (12 inch) CRT display, numerical keyboard for selection of operating parameters and the entry of tristimulus values, and an alphanumeric keyboard for entry of product standard information. EXAMPLE I Transparency sheets were prepared as follows. Blends of 70 percent by weight hydroxypropyl methyl cellulose (K3SLV®, obtained from Dow Chemical Co.) and 30 percent by weight of various additive compositions, each obtained from Aldrich Chemical Co., were prepared by mixing 56 grams of hydroxypropyl methyl cellulose and 24 grams of the additive composition in 1,000 milliliters of water in a 2 Liter jar and stirring the contents in an Omni® homogenizer for 2 hours. Subsequently, the solution was left overnight for removal of air bubbles. The blends thus prepared were then coated by a dip coating process (both sides coated in one operation) by providing Mylar® base sheets in cut sheet form 21.6 x 27.9 cm (8.5 × 11 inches), 21.6 x 27.9cm) in a thickness of 100 µm. Subsequent to air drying at 25°C for 3 hours followed by oven drying at 100°C for 10 minutes and monitoring the difference in weight prior to and subsequent to coating, the dried coated sheets were each coated with 1 gram, 10 µm in thickness, on each surface (2 grams total coating weight for 2-sided transparency) of the substrate. For comparison purposes, a transparency sheet was also prepared in which the coating consisted of 100 percent by weight hydroxypropyl methyl cellulose and contained no additive composition. The transparency sheets thus prepared were incorporated into a Hewlett-Packard 500-C® color ink jet printer containing inks of the following compositions: Cyan: 20 percent by weight ethylene glycol, 2.5 percent by weight benzyl alcohol, 1.9 percent by weight ammonium chloride, 0.1 percent by weight Dowicil® 150 biocide, obtained from Dow Chemical Co., Midland, MI, 0.05 percent by weight polyethylene oxide (molecular weight 18,500), obtained from Union Carbide Co.), 30 percent by weight Projet Cyan 1 dye, obtained from ICI, 45.45 percent by weight water. Magenta: 20 percent by weight ethylene glycol, 2.5 percent by weight benzyl alcohol, 1.9 percent by weight ammonium chloride, 0.1 percent by weight Dowicil® 150 biocide, obtained from Dow Chemical Co., Midland, MI, 0.05 percent by weight polyethylene oxide (molecular weight 18,500), obtained from Union Carbide Co.), 2.5 percent by weight Triton Direct Red 227, obtained from Tricon, 72.95 percent by weight water. Yellow: 20 percent by weight ethylene glycol, 2.5 percent by weight benzyl alcohol, 1.9 percent by weight ammonium chloride, 0.1 percent by weight Dowicil® 150 biocide, obtained from Dow Chemical Co., Midland, MI, 0.05 percent by weight polyethylene oxide (molecular weight 18,500), obtained from Union Carbide Co.), 3 percent by weight Hoechst Duasyn Brilliant Yellow SF-GL VP220, obtained from Hoechst, 72.45 percent by weight water. Images were generated by printing block patterns for magenta, cyan, yellow, and black. The images thus formed were dried by exposure to microwave radiation with a Citizen Model No. JM55581®, obtained from Consumers, Mississauga, Ontario, Canada, set at 700 Watts output power at 2450 MHz frequency. The black images were "process black" (i.e., formed by superimposition of cyan, magenta, and yellow images). The drying times and optical densities for the resulting images were as follows: Additive Drying Time (seconds) Optical Density black cyan magenta yellow black cyan magenta yellow none 30 20 30 20 2.50 2.07 1.45 0.99 4,6-dimethyl-2-hydroxy pyrimidine hydrochloride 20 10 40 10 1.80 1.65 1.37 0.95 6-amino purine 10 20 20 20 2.00 2.00 1.50 0.90 1,4-bis (2-hydroxyethyl) piperazine 20 30 20 20 2.40 2.31 1.69 0.90 4-(2-hydroxyethyl)-1-piperazine propane sulfonic acid 10 10 40 30 2.00 1.78 1.70 0.92 1-(2-methoxyphenyl) piperazine hydrochloride 10 15 15 20 1.80 2.00 1.51 0.93 3,5-dimethylpyrazole-1-carboxamidine nitrate 10 10 20 20 1.88 1.85 1.63 0.96 As the results indicate, the drying times of the process black images were faster in the presence of the additives than in their absence. In addition, the optical densities of all images were also acceptable and in some instances were improved. EXAMPLE II Transparency sheets were prepared as follows. Blends of 90 percent by weight hydroxypropyl methyl cellulose (K35LV®, obtained from Dow Chemical Co.) and 10 percent by weight of various additive compositions, each obtained from Aldrich Chemical Co., were prepared by mixing 72 grams of hydroxypropyl methyl cellulose and 8 grams of the additive composition in 1,000 milliliters of water in a 2 Liter jar and stirring the contents in an Omni homogenizer for 2 hours. Subsequently, the solution was left overnight for removal of air bubbles. The blends thus prepared were then coated by a dip coating process (both sides coated in one operation) by providing Mylar® base sheets in cut sheet form (8.5 × 11 inches; 21.6x27.9cm) in a thickness of 100 µm. Subsequent to air drying at 25°C for 3 hours followed by oven drying at 100°C for 10 minutes and monitoring the difference in weight prior to and subsequent to coating, the dried coated sheets were each coated with 1 gram, 10 µm in thickness, on each surface (2 grams total coating weight for 2-sided transparency) of the substrate. For comparison purposes, a transparency sheet was also prepared in which the coating consisted of 100 percent by weight hydroxypropyl methyl cellulose and contained no additive composition. The transparency sheets thus prepared were incorporated into a Hewlett-Packard 500-C color ink jet printer containing inks of the following compositions: Cyan: Same as Example I. Magenta: Same as Example I. Yellow: Same as Example I. Images were generated by printing block patterns for magenta, cyan, yellow, and black. The images thus formed were allowed to dry at 25°C. The black images were "process black" (i.e., formed by superimposition of cyan, magenta, and yellow images). The drying times and optical densities for the resulting images were as follows: Additive Drying Time (minutes) Optical Density black cyan magenta yellow black cyan magenta yellow none 10 5 5 2 2.95 2.10 1.37 0.99 4,6-dimethyl-2-hydroxy pyrimidine hydrochloride 8 3 5 1.5 1.70 1.70 1.50 0.80 6-amino purine (adenine) sulfate 8 3 4 1.5 1.65 1.60 1.10 0.92 6-amino purine hydrochloride hemihydrate 8 4 4 1.5 2.50 2.00 1.20 0.80 orotic acid monohydrate 8 4 4 1.5 2.40 1.81 0.91 0.77 1,4-bis (2-hydroxyethyl) piperazine 6 2.5 2.5 1.5 1.90 2.37 1.43 0.82 sarcosine anhydride 7 2.5 5 1.5 2.00 1.79 1.30 0.90 4-(2-hydroxyethyl)-1-piperazine propane sulfonic acid 6 2.5 2.5 1.5 1.90 1.90 1.40 0.82 1-(2-methoxyphenyl) piperazine hydrochloride 6 3 3 1.5 1.88 1.95 1.45 0.82 1-(2-ethoxyphenyl) piperazine monohydrochloride (methanol) 6 3 3 1.5 1.52 1.80 1.27 0.87 L-histidine monochloride 7 3 3 2 2.70 1.75 1.15 0.85 As the results indicate, the drying times of the transparencies containing the additives were generally equivalent to or faster than the drying times of the transparency containing no additives. In addition, the optical densities of the images on the transparencies containing the additives were acceptable and in some instances improved compared to those on the transparencies containing no additives. EXAMPLE III Transparency sheets were prepared as follows. Blends of 54 percent by weight hydroxypropyl methyl cellulose (K35LV®, obtained from Dow Chemical Co.), 36 percent by weight poly(ethylene oxide) (POLY OX WSRN-3000®, obtained from Union Carbide Corp., and 10 percent by weight of various additive compositions, each obtained from Aldrich Chemical Co., were prepared by mixing 43.2 grams of hydroxypropyl methyl cellulose, 28.8 grams of poly(ethylene oxide), and 8 grams of the additive composition in 1,000 milliliters of water in a 2 Liter jar and stirring the contents in an Omni® homogenizer for 2 hours. Subsequently, the solution was left overnight for removal of air bubbles. The blends thus prepared were then coated by a dip coating process (both sides coated in one operation) by providing Mylar® base sheets in cut sheet form (8.5 × 11 inches; 21.6x27.9cm) in a thickness of 100 µm. Subsequent to air drying at 25°C for 3 hours followed by oven drying at 100°C for 10 minutes and monitoring the difference in weight prior to and subsequent to coating, the dried coated sheets were each coated with 1 gram, 10 µm in thickness, on each surface (2 grams total coating weight for 2-sided transparency) of the substrate. For comparison purposes, a transparency sheet was also prepared in which the coating consisted of 60 percent by weight hydroxypropyl methyl cellulose and 40 percent by weight poly(ethylene oxide) and contained no additive composition. The transparency sheets thus prepared were incorporated into a Hewlett-Packard 500-C color ink jet printer containing inks of the following compositions: Cyan: Same as Example I. Magenta: Same as Example I. Yellow: Same as Example I. Images were generated by printing block patterns for magenta, cyan, yellow, and black. The images thus formed were allowed to dry at 25°C. The black images were "process black" (i.e., formed by superimposition of cyan, magenta, and yellow images). The drying times and optical densities for the resulting images were as follows: Addtitive Drying Time (minutes) Optical Density black cyan magenta yellow black cyan magenta yellow none 15 10 10 10 1.40 1.46 1.34 1.02 2-hydroxy pyrimidine hydrochloride 10 6 6 5 1.40 1.35 1.20 0.83 4-(2-hydroxyethyl)-1-piperazine propane sulfonic acid 10 6 5 4 1.42 1.40 1.22 0.82 2-methylthio-2-imidazoline hydriodide 9 5 5 4 1.38 1.58 1.30 0.93 urazole 8 5 4 4 1.41 1.44 1.18 0.85 As the results indicate, the drying times of the transparencies containing the additives were generally faster than the drying times of the transparency containing no additives. In addition, the optical densities of the images on the transparencies containing the additives were acceptable in all instances. EXAMPLE IV Paper recording sheets were prepared as follows. Coating compositions containing various additive compositions, each obtained from Aldrich Chemical Co., were prepared by dissolving 50 grams of the additive in 500 milliliters of water in a beaker and stirring for 1 hour at 25°C. The additive solutions thus prepared were then coated onto paper by a dip coating process (both sides coated in one operation) by providing paper base sheets in cut sheet form (8.5 × 11 inches; 21.6x27.9cm) in a thickness of 100 µm. Subsequent to air drying at 100°C for 10 minutes and monitoring the difference in weight prior to and subsequent to coating, the sheets were each coated on each side with 500 milligrams, in a thickness of 5 µm (total coating weight 1 gram for two-sided sheets), of the additive composition For comparison purposes, an uncoated paper sheet treated with a composition containing only water by the same procedure was also imaged. The paper sheets thus prepared were incorporated into a Hewlett-Packard 500-C® color ink jet printer containing inks of the following composition: Cyan: Same as Example I. Magenta: Same as Example I. Yellow: Same as Example I. Images were generated with 100 percent ink coverage. After the image was printed, the paper sheets were each weighed precisely in a precision balance at time zero and periodically after that. The difference in weight was recorded as a function of time, 100 minutes being considered as the maximum time required for most of the volatile ink components to evaporate. (Volatiles were considered to be ink components such as water and glycols that can evaporate, as compared to components such as dyes, salts, and/or other non-volatile components. Knowing the weight of ink deposited at time zero, the amount of volatiles in the image can be calculated.) After 1000 minutes, the curl values of thepaper were measured and are listed in the Table below. The black images were "process black" (i.e., formed by superimposition of cyan, magenta, and yellow images). Additive percent weight-loss of volatiles at various times (minutes) 1,000 minutes 5 10 15 30 60 120 wt. loss % curl in mm none 32 43 45 48 50 53 65 125 2-amino pyrimidine 41 54 58 64 66 68 100 5 2-hydroxy pyrimidine hydrochloride 33 48 52 56 62 64 85 25 4,6-dimethyl-2-hydroxy pyrimidine hydrochloride 35 49 56 60 62 65 85 10 2,4,5,6-tetra amino pyrimidine sulfate 32 47 51 60 69 78 95 5 purine 33 45 50 57 59 63 75 35 6-aminopurine hydrochloride hemihydrate 31 45 50 56 58 60 89 20 1,4-bis(2-hydroxyethyl) piperazine 33 52 57 64 65 66 91 25 1,4-dimethyl-2,5-piperazine dione 40 49 53 56 59 66 83 35 4-(2-hydroxyethyl)-1-piperazine ethane sulfonic acid 29 44 50 56 59 60 88 25 1-(4-chlorophenyl) piperazine dihydrochloride 29 38 43 47 50 53 78 55 1-(2-methoxyphenyl) piperazine hydrochloride 36 45 50 53 57 60 78 25 1-(0-tolyl) piperazine hydrochloride 38 51 56 61 65 68 99 20 2-methylthio-2-imidazoline hydriodide 37 50 52 54 58 66 78 25 L-histidine monochloride monohydrate 34 51 55 60 63 68 91 15 urazole 29 38 40 43 46 52 81 20 1-H-tetrazole 31 44 49 52 54 58 81 25 3-amino pyrazole 40 45 49 52 53 59 69 65 3,5-dimethyl pyrazole-1-carboxamidine nitrate 24 43 48 54 56 58 76 30 As the results indicate, the papers coated with the additives exhibited higher weight loss of volatiles at time 1,000 minutes compared to the paper which had been treated with water alone. In addition, the papers coated with the additives exhibited lower curl values compared to the curl value for the paper treated with water alone. EXAMPLE V Paper recording sheets were prepared as follows. Coating compositions containing various additive compositions, each obtained from Aldrich Chemical Co., were prepared by dissolving 50 grams of the additive in 500 milliliters of water in a beaker and stirring for 1 hour at 25°C. The additive solutions thus prepared were then coated onto paper by a dip coating process (both sides coated in one operation) by providing paper base sheets in cut sheet form (8.5 × 11 inches; 21.6x27.9cm) in a thickness of 100 µm. Subsequent to air drying at 100°C for 10 minutes and monitoring the difference in weight prior to and subsequent to coating, the sheets were each coated on each side with 500 milligrams, in a thickness of 5 µm (total coating weight 1 gram for two-sided sheets), of the additive composition For comparison purposes, an uncoated paper sheet treated with a composition containing only water by the same procedure was also imaged. The paper sheets thus prepared were incorporated into a Hewlett-Packard 500-C® color ink jet printer containing inks of the following composition: Cyan: Same as Example I. Magenta: Same as Example I. Yellow: Same as Example I. The black images were "process black" (i.e., formed by superimposition of cyan, magenta, and yellow images). The optical densities for the resulting images were as follows: Additive Optical Density black cyan magenta yellow none 1.08 1.18 1.03 0.80 2-amino pyrimidine 1.16 1.29 1.14 0.89 2-hydroxy pyrimidine hydrochloride 0.99 1.03 0.80 0.74 4,6-dimethyl-2-hydroxy pyrimidine hydrochloride 0.98 0.99 0.82 0.70 2,4,5,6-tetra amino pyrimidine sulfate 1.05 1.15 1.00 0.80 purine 1.00 1.10 0.95 0.75 6-aminopurine hydrochloride hemihydrate 0.95 0.99 0.82 0.67 1,4-bis (2-hydroxy ethyl) piperazine 1.10 1.25 1.03 0.75 1,4-dimethyl-2,5-piperazine dione 1.15 1.29 0.96 0.75 4-(2-hydroxyethyl)-1-piperazine ethane sulfonic acid 1.22 1.34 1.12 0.77 1-(4-chorophenyl) piperazine dihydrochloride 1.12 1.09 1.01 0.74 1-(2-methoxyphenyl) piperazine hydrochloride 1.24 1.13 0.97 0.77 1-(0-tolyl) piperazine hydrochloride 1.14 1.11 0.98 0.75 2-methylthio-2-imidazoline hydriodide 1.25 1.15 1.10 0.80 L-histidine monochloride monohydrate 1.30 1.15 1.13 0.89 urazole 1.18 1.22 1.12 0.92 1-H-tetrazole 1.09 1.05 0.93 0.77 3-amino pyrazole 1.34 1.23 1.16 0.91 3,5-dimethyl pyrazole-1-carboxamidine nitrate 1.08 1.11 0.96 0.81 As the results indicate, the papers coated with the additive compositions exhibited acceptable optical densities for all colors.

Claims: A recording sheet which comprises a substrate, for example paper or a transparent polymeric material, and an additive material present on the substrate selected from the group consisting of purine compounds, pyrimidine compounds, benzimidazole compounds, imidazolidine compounds, urazole compounds, pyrazole compounds, triazole compounds, benzotriazole compounds, tetrazole compounds, pyrazine compounds, and mixtures thereof; wherein the benzotriazole compounds are selected from the formula wherein R 1 , R 2 , R 3 and R 4 each, independently of one another, are hydrogen, alkyl, substituted alkyl or hydroxyl; the benzimidazole compounds are selected from the group consisting of (1) benzimidazole; (2) 2-aminobenzimidazole; (3) 2-amino-5,6-dimethlybenzimidazole; (4) 5-benzimidazole carboxylic acid; (5) 2,4,5-trimethyl benzimidazole; (6) 2-guanidinobenzimidazole; (7) 2-hydroxybenzimidazole; (8) 4-(2-keto-1-benzimidazolinyl) piperidine; and mixtures thereof; the pyrimidine compounds are selected from the general formula wherein R 1 , R 2 , R 3 and R 4 each, independently of one another, are hydrogen, alkyl, substituted alkyl, halide, nitro, hydroxyl, amino, nitroso, mercaptyl, thio, sulfanilamide, carboxyl, oxo, monosaccharide, oligosaccharide; or wherein one or more of the ring double bonds is saturated and/or wherein one or both of the ring nitrogen atoms is bonded to a substituent and/or wherein one or more of the ring carbon atoms has a double bond to another atom such as carbon, oxygen, or sulfur, or wherein two or more substituents are joined together to form another ring, with the proviso that R 1 , R 4 or R 2 does not represent a thio group. The recording sheet according to claim 1, further containing at least one component selected from the group consisting of a binder, an antistatic agent, a biocide and a filler. The recording sheet according to claim 1 or 2, wherein the additive material is present on the substrate in an amount of (1) from 1 to 50 percent by weight of the substrate, and/or (2) from 0.8 to 40 grams per square meter of the substrate. The recording sheet according to any of claims 1 to 3, wherein the binder comprises (1) a polysaccharide, or (2) a quaternary acrylic copolymer latex. The recording sheet according to any of the preceding claims wherein a binder and the additive material (1) are present in relative amounts of from 10 percent by weight binder and 90 percent by weight additive material to 99 percent by weight binder and 1 percent by weight additive material, and/or (2) are coated onto the substrate in a thickness of from 1 to 25 µm. The recording sheet according to any of the preceding claims wherein the additive is (A) a purine compound, (B) selected from the group consisting of (1) purine; (2) 6-amino purine; (3) 6-methoxy purine; (4) 6-mercaptopurine; (5) 2-amino-6-chloropurine; (6) 2-amino-6,8-dihydroxy purine; (7) theophylline; (8) kinetin; (9) 1-methyl adenine; (10) 3-methyl adenine; (11) adenosine; (12) inosine; (13) 6-mercaptopurine riboside; (14) 6-amino purine acid salts; (15) 2,6-diamino-8-purinol acid salts; and mixtures thereof, (C) a pyrimidine compound, (D) selected from the group consisting of (a) amino pyrimidine compounds; (b) dihydroxypyrimidine compounds; (c) pyrimidine dione compounds; (d) thiouracil compounds; (e) orotic acid compounds; (f) pyrimidine trione compounds; (g) guanine compounds; (h) xanthine compounds; (i) pyrazole pyrimidine compounds; (j) pyrimidine acids; and mixtures thereof (E) selected from the group consisting of (1) 2-amino pyrimidine; (2) 2-amino-4-methyl pyrimidine; (3) 2-amino-5-nitropyrimidine; (4) 2-amino-5-bromopyrimidine; (5) 2-amino-4-chloro-6-methyl pyrimidine; (6) 2-amino-4,6-dimethyl pyrimidine; (7) 2-amino-4-hydroxy-6-methyl pyrimidine; (8) 2-amino-4,6-dichloropyrimidine; (9) 2-amino-5-bromo-6-methyl-4-pyrimidinol; (10) 4-aminopyrimidine; (11) 4,5-diamino pyrimidine; (12) 4-amino-2,6-dimethyl pyrimidine; (13) 2,4-diamino-6-hydroxypyrimidine; (14) 2,6-diamino-4-chloro pyrimidine; (15) 4,6-diamino-2-mercaptopyrimidine; (16) 2,4,6-triamino pyrimidine; (17) 5-nitroso-2,4,6-triamino pyrimidine; and mixtures thereof, or (F) selected from the group consisting of (1) 4,6-dihydroxy pyrimidine; (2) 4,6-dihydroxy-2-amino pyrimidine; (3) 4,6-dihydroxy-2-methyl pyrimidine; (4) 4,6-dihydroxy-5-nitropyrimidine; (5) 2,4-dihydroxy-5-methyl pyrimidine; (6) 2,4-dihydroxy-6-methyl pyrimidine; (7) 2,4-dihydroxy-5,6-dimethyl pyrimidine; (8) 2,6-dihydroxy pyrimidine-5-carboxylic acid; (9) 2,6-dihydroxy-4-amino pyrimidine; (10) 2,4,5-trihydroxy pyrimidine; and mixtures thereof. The recording sheet according to any of claims 1 to 5, wherein the additive is (A) selected from the group consisting of (1) 2,4 (1H,3H)-pyrimidine dione; (2) 5-amino uracil; (3) 5-nitrouracil; (4) 5-iodouracil; (5) 5-(hydroxymethyl) uracil; (6) 5,6-dihydrouracil; (7) 6-amino-1-methyl uracil; (8) 5,6-diamino-1,3-dimethyl uracil; (9) uridine; (10) 5-methyl uridine; (11) 5-iodouridine; (12) thimidine; and mixtures thereof, (B) selected from the group consisting of (1) 2-thiouracil; (2) 5-methyl-2-thiouracil; (3) 6-amino-5-nitroso-2-thiouracil; (4) 4-thiouridine; (5) 2-thiocytidine; (5) orotic acid; (6) L-hydroorotic acid; (7) 5-aminoorotic acid; (8) methylorotate; (9) barbituric acid; (10) 5-nitrobarbituric acid; (11) violuric acid; (12) alloxan monohydrate; (13) 1-methyl uric acid; (14) guanine; (15) guanosine monohydrate; (16) xanthine; (17) 1-methylxanthine; (18) 3-methyl xanthine; (19) 3-isobutyl-1-methyl xanthine; (20) hypoxanthine; (21) xanthosine dihydrate; (22) 6-thioxanthene; (23) 4-hydroxypyrazolo [3,4-d] pyrimidine; (24) 4-mercapto-1H-pyrazolo-[3,4-d]-pyrimidine; (25) folic acid; (26) folinic acid, salts; and mixtures thereof, (C) a pyrimidine salt compound, (D) selected from the group consisting of (1) 2-hydroxypyrimidine acid salts; (2) 2-hydroxy-4-methyl pyrimidine acid salts; (3) 4,6-dimethyl-2-hydroxypyrimidine acid salts; (4) 2-mercapto-4-methyl pyrimidine acid salts; (5) 4,6-diamino pyrimidine acid salts; (6) 4,5,6-triamino pyrimidine acid salts; (7) 4,5-diamino-6-hydroxy pyrimidine acid salts; (8) 2,4-diamino-6-mercapto pyrimidine acid salts; (9) 2,4-diamino-6-hydroxy pyrimidine acid salts; (10) 6-hydroxy-2,4,5-triamino pyrimidine acid salts; (11) 5,6-diamino-2,4-dihydroxy pyrimidine acid salts; (12) N 4 -(2-amino-4-pyrimidinyl) sulfanilamide acid salts; (13) 4,5,6-triamino-2(1H)-pyrimidinethione acid salts; (14) 2,4,5,6-tetraamino pyrimidine acid salts; (15) cyclocytidine acid salts; (16) cytosine arabinoside acid salts; and mixtures thereof. The recording sheet according to any of claims 1 to 5, wherein the additive is (A) an imidazolidine compound, (B) selected from the group consisting of (1) 2-imidazolidine thione; (2) 2-imidazolidone; (3) hydantoin; (4) 1-methyl hydantoin; (5) creatinine; (6) 2-thiohydrantoin; (7) 5-hydantoin acetic acid; (8) 5-ureidohydantoin; (9) 5,5-dimethyl hydantoin; (10) 2-imidazolidone-4-carboxylic acid; and mixtures thereof, (C) a urazole compound, (D) selected from the group consisting of (1) urazole; (2) 1-methyl urazole; (3) 4-phenyl urazole; (4) D,L-5-(4-hydroxyphenyl)-5-phenyl hydantoin; (5) β-tetralone hydantoin; and mixtures thereof, (E) a pyrazole compound, or (F) selected from the group consisting of (1) pyrazole; (2) 4-pyrazole carboxylic acid; (3) ethyl 4-pyrazole carboxylate; (4) 3,5-pyrazole dicarboxylic acid; (5) 3-amino pyrazole; (6) 3-amino-5-hydroxypyrazole; (7) 3-amino-5-methylpyrazole; (8) 3-amino-4-pyrazole carbonitrile; (9) 3-amino-4-pyrazolecarboxylic acid; (10) 3-amino-4-carbethoxypyrazole; (11) 5-amino-1-ethylpyrazole; (12) 4-bromo-3-methyl pyrazole; (13) 3,5-dimethyl pyrazole; (14) 3,5-dimethyl pyrazole-1-carboxamide; (15) 4-bromo-3,5-dimethyl pyrazole; (16) 3,5-dimethylpyrazole-1-methanol; (17) 4-methyl pyrazole acid salts; (18) 3,4-diamino-5-hydroxy pyrazole acid salts; (19) 3,5-dimethyl pyrazole-1-carboxamidine acid salts; (20) 3-amino-4-pyrazole carboxamide acid salts; (21) of 6-amino indazole acid salts; and mixtures thereof. The recording sheet according to any of claims 1 to 5, wherein the additive is (A) selected from the group consisting of triazole compounds and benzotriazole compounds, (B) selected from the group consisting of (1) 1,2,4-triazole; (2) 1,2,4-triazole salts; (3) 3-amino-1,2,4-triazole; (4) 4-amino-1,2,4-triazole; (5) 3,5-diamino-1,2,4-triazole; (6) 3-amino-5-mercapto-1,2,4-triazole; (7) 3-amino-5-methylthio-1H-1,2,4-triazole; (8) 3-amino-1,2,4-triazole-5-carboxylic acid; (9) 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole; (10) 1,2,3-triazole-4,5-dicarboxylic acid; (11) nitron; (12) benzotriazole; (13) 1-hydroxybenzotriazole; and mixtures thereof, (C) a tetrazole compound, (D) selected from the group consisting of (1) 1-H-tetrazole; (2) 5-amino tetrazole; and mixtures thereof, (E) a pyrazine compound, or (F) selected from the group consisting of (1) 5-methyl-2-pyrazine carboxylic acid; (2) pyrazine amide; (3) 2,3-pyrazine dicarboxamide; (4) 4-pyridazine carboxylic acid; (5) 2,3-pyrazine dicarboxylic acid; (6) lumazine; (7) xanthopterin; (8) 2-quinoxazoline carboxylic acid; (9) 2-quinoxalinol; (10) 2,3-dihydroxy quinoxaline; (11) phenazine acid salts; and mixtures thereof. An ink jet printing process comprising (a) applying an aqueous recording liquid in an imagewise pattern to a recording sheet according to any of claims 1 to 9; or (b) (1) incorporating a recording sheet according to any of claims 1 to 9 into an ink jet printing apparatus containing an aqueous ink, and (2) causing droplets of the ink to be ejected in an imagewise pattern onto the recording sheet thereby generating images on the recording sheet.

Inventors: MALHOTRA SHADI L, MALHOTRA, SHADI L.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1995
Main classification: B41M5
IPC codes: B41M5