Abstract:
A pressure-sensitive record material comprising the colorless chromogenic dye Pyridyl Blue mixed with and adsorbed onto a pigment which is coated on a substrate sheet, and capsules containing an acidic resin dissolved in a suitable solvent, the capsules being coated on the same or an additional sheet. This &#34;reverse&#34; system (where the acidic resin rather than the dye is encapsulated) provides an improved community of properties, including improved image strength, print stability (fade resistance) and resistance to degradation. Pyridyl Blue is a mixture of the isomers 7-(1-ethyl-2-methylindol-3-yl)-7-(4-diethylamino-2-ethoxyphenyl)-5,7-dihydrofuro[3,4-b]pyridin-5-one and 5-(1-ethyl-2-methylindol-3-yl)-5-(4-diethylamino-2-ethoxyphenyl)-5,7-dihydrofuro[3,4-b]pyridin-7-one.

Description:
This application is a Continuation-in-Part of copending application Ser. No. 365, filed on Dec. 29, 1978, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a pressure-sensitive record material. More particularly, the invention relates to a pressure-sensitive record system comprising a specific colorless chromogenic dye material, Pyridyl Blue, as defined hereinafter, mixed with and adsorbed onto a pigment which is coated onto a dyereceiving sheet along with the usual binder and other paper coating ingredients, and capsules containing an acidic resin dissolved in a suitable solvent, which capsules are coated on the same or an additional sheet. 
     DESCRIPTION OF THE PRIOR ART 
     Pressure-sensitive record materials employing colorless chromogenic compounds which form a mark when contacted with an acidic substance are well known in the art. Exemplary thereof are Crystal Violet Lactone (CVL) as described in Reissue patent No. 23,024 and the compouds disclosed in U.S. Pat. Nos. 3,509,173 (3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, also known as Indolyl Red) and 3,681,390 (2&#39;-anilino-3&#39;-methyl-6&#39;-diethylaminofluoran, also known as N-102 dye). 
     Japanese application No. 48-29820, published as a Disclosure on Nov. 13, 1974, and Japanese application No. 48-53691, published as a Disclosure on Jan. 20, 1975, both disclose a colorless marking fluid employed in a pressure-sensitive record paper comprising a homolog of Pyridyl Blue and various solvents. 
     U.S. Pat. No. 3,894,168, which issued on July 8, 1975, discloses a &#34;reverse&#34; system analogous to that employed herein. This prior art, however, does not teach or suggest a reverse system with the use of the Pyridyl Blue dye material as disclosed in the present specification. 
     SUMMARY OF THE INVENTION 
     One of the objects of the present invention is to provide a &#34;reverse&#34; pressure-sensitive record system having an improved community of properties as compared with the systems taught in the prior art. 
     A specific object of the invention is to provide a colorless chromogenic system which imparts improved image strength, print stability (fade resistance) and resistance to degradation in a pressure-sensitive record material. 
     These and other objects and advantages of the present invention will become apparent to those skilled in the art from a consideration of the following specification and claims. 
     In accordance with the present invention, Pyridyl Blue, which is a mixture of the isomers 7-(1-ethyl-2-methylindol-3-yl)-7-(4-diethylamino-2-ethoxyphenyl)-5,7-dihydrofuro[3,4-b]pyridin-5-one, and 5-(1-ethyl-2-methylindol-3-yl)-5-(4-diethylamino-2-ethoxyphenyl)-5,7-dihydrofuro[3,4-b]pyridin-7-one, is mixed with and adsorbed onto a pigment such as calcium carbonate and the resulting dye precursor-coated pigment is coated on a dye-receiving sheet together with a suitable binder and the other usual paper coating ingredients. Capsules containing an acidic material, such as a para-phenylphenol-formaldehyde resin or a para-octylphenol-formaldehyde resin, dissolved in a solvent are coated on the same or an additional sheet. Coreaction between the colorless chromogenic dye material and acidic material released from said capsules by means of pressure produces a colored mark. 
     As noted above, the use of the Pyridyl Blue colorless chromogenic material of the invention imparts improved properties, for example, improved image strength, print stability (fade resistance) and resistance to degradation when compared to systems which employ, for instance, Crystal Violet Lactone in a similar reverse system. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Formulations and techniques for the preparation of carbonless copy paper are well known in the art, for example, as disclosed in U.S. Pat. Nos. 3,627,581, 3,775,424 and 3,853,869. However, it is important to note that in the &#34;reverse&#34; system of the invention, the dye (adsorbed onto a pigment) is coated on a dye receptor (CF-coated front) sheet and the acidic resin dissolved in a solvent is enclosed within capsules, whereas the opposite is true in the usual carbonless copy paper transfer system. 
     The solvent for the acidic resin enclosed within the capsules can be any of those well known in the carbonless copy paper art, e.g., 
     dibenzyl ether 
     Magnaflux oil (saturated hydrocarbon oil, distillation range: 370°-500° F.) 
     benzyl benzoate 
     2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB; U.S. Pat. No. 4,027,065) 
     dibutyl phthalate 
     1,2,4-trimethyl benzene 
     ethyldiphenyl methane (U.S. Pat. No. 3,996,405) 
     C 11  -C 12  alkylbenzene 
     isopropyl biphenyl (U.S. Pat. No. 3,627,581) 
     However, the most preferred is a mixed solvent of dibenzyl ether and Magnaflux oil. 
     Any water-insoluble and approximately chemically neutral pigments such as calcium carbonate, zinc oxide, barium sulfate, titanium oxide, barium carbonate, magnesium carbonate, calcium oxide, magnesium titanate and zinc sulfide can be employed in the present invention. Calcium carbonate is preferred. 
     In a typical formulation, Pyridyl Blue, a neutral pigment, at least one binder (e.g., a styrene-butadiene latex and/or starch) are admixed in water and coated on a CF sheet. Small amounts of conventional materials such as wetting agents and defoamers can also be employed in the formulation. When used in conjunction with the encapsulated acidic resin, either on the same or a separate sheet, an excellent pressure-sensitive record material is obtained. 
     The capsules for the acidic resin can be prepared from gelatin as described in U.S. Pat. No. 3,041,289, from a ureaformaldehyde polymer as disclosed in U.S. Pat. No. 4,001,140, from resorcinol-formaldehyde filled poly(vinyl alcohol) wall material capsules as described in U.S. Pat. No. 3,755,190, or from various melamine-formaldehyde polymers as disclosed in U.S. Pat. No. 4,100,103. 
    
    
     EXAMPLES OF THE INVENTION 
     The following examples are given merely as illustrative of the present invention and are not to be considered as limiting. Unless otherwise noted, the percentages in the examples and throughout the application are by weight. 
     The test results shown in the Examples were determined in the following manner. 
     In the Typewriter Intensity (TI) test, a standard pattern is typed on a CF-CB (coated front-coated back) pair. The reflectance of the printed area is a measure of color development on the CF sheet and is reported as the ratio of the reflectance of the printed area to that of the untyped area (I/I o ) and is expressed as a percentage. A high value indicates little color development and a low value indicates good color development. The faded print intensity is measured in the same manner. 
     Typewriter Intensity tests were also conducted before and after exposure of the print in various ways, including exposure at the noted times to fluorescent light, to natural sunlight, to ambient conditions and within an oven. The fluorescent light test device comprised a light box containing a bank of 18 daylight fluorescent lamps (21 inches long, 13 nominal lamp watts) vertically mounted on 1-inch centers placed 11/2 inches from the sample being exposed. The wall exposure comprised exposure of the print by hanging the printed sheet on the laboratory wall for the noted times, exposed to air, natural and fluorescent room light, and ambient temperature and moisture levels. 
     The following procedures were used to prepare dye receiving CF sheets containing CVL (Crystal Violet Lactone) and Pyridyl Blue: 
     EXAMPLE 1 
     Dye precursor-coated neutral pigment particles 
     (A) 1 gram of Pyridyl Blue was dissolved in 150 mls of acetone. 70 grams of precipitated CaCO 3 , 20 grams of Cabolite 100 urea-formaldehyde resin pigment (U.S. Pat. No. 3,988,522) and 10 grams of ZnO (Green Seal 8 from New Jersey Zinc Co.) were blended in the above solution and the resulting dispersion was allowed to dry in a hood. 
     (B) 1 gram of CVL was dissolved in 150 mls of acetone. 70 grams of precipitated CaCO 3 , 20 grams of Cabolite 100 and 10 grams of ZnO (Green Seal 8 from New Jersey Zinc Co.) were blended in the above solution and the resulting dispersion was allowed to dry in a hood. 
     Paper-coating slurry of dye precursor-coated pigment 
     The dye precursor-coated pigments (A) and (B) as described above were dispersed individually with the following materials: 
     
         __________________________________________________________________________         I           II         Parts             Parts   Parts                         Parts         Wet Dry Dry %                     Wet Dry Dry %__________________________________________________________________________Pyridyl Blue pigment (A)         84  84  83.4CVL pigment (B)           84  84  83.4Penford Gum 260         100 10  9.9 100 10  9.9(modified corn starch)Dow Latex 620 12  6   6.0 12  6   6.0(carboxylated styrene-butadiene latex)Tamol 731     3   0.75                 0.7 3   0.75                             0.7(25% solution of thesodium salt of apolymeric carboxylicacid, supplied byRohm &amp; Haas)Water         250 --  --  250 --  --Totals        449 100.75                 100.0                     449 100.75                             100.0__________________________________________________________________________ 
    
     The above paper-coating slurries were coated on 34 pound bond paper with a No. 12 Mayer rod. After drying, the coating weight was about 4.5 pounds per ream of 500 sheets, measuring 25 by 38 inches. 
     EXAMPLE 2 
     Alternate method of manufacture of dye precursor-coated neutral pigment particles and pigment coated sheets 
     (C) 300 grams of Pyridyl Blue, 600 grams of calcium carbonate, 300 grams of 10% solids Penford Gum 230 (modified corn starch), 1200 grams of water and 30 grams of 25% solids Tamol 731 were attritored for 45 minutes. A few drops of octanol were added, to reduce foaming. 
     (D) 300 grams of CVL, 300 grams of calcium carbonate, 300 grams of zinc resinate, 300 grams of 10% solids Penford Gum 230, 1200 grams of water and 30 grams of 25% solids Tamol 731 were attritored for 45 minutes. A few drops of octanol were added to reduce foaming. 
     These attritor grinds were used to formulate dye receiving sheet coating formulas having the following compositions: 
     
         ______________________________________      III         IV      Parts Parts  Dry    Parts Parts                                     Dry      Wet   Dry    %      Wet   Dry  %______________________________________Pyridyl Blue 6.3     2.0    3.0Grind (C)CVL Grind (D)                    6.4   2.0  3.0CaCO.sub.3   43.4    43.4   65.8 43.4  43.4 68.8Ansilex Clay 9.9     9.9    15.0 9.9   9.9  15.0(U.S. Pat. 3,586,523)Penford Gum 230        66.0    6.6    10.0 66.0  6.6  10.0Dow Latex 620        8.0     4.0    6.0  8.0   4.0  6.0Calgon T     .1      .1     .1   .1    .1   .1(a fused sodium-zincphosphate glasscomposition inpowder form)Water        110.3   --     --   110.3 --   --Totals       224.0   66.0   99.9 244.0 66.0 99.9Coating Solids        27%           27%Viscosity    58 cps        57 cps______________________________________ 
    
     These coating slurries were applied to a 34 pound base sheet at a rate of 4.5 lbs. (500 sheets measuring 25 by 38 inches) with an air knife coater. 
     EXAMPLE 3 
     Preferred encapsulated acidic marking liquid 
     The following procedure was used to prepare phenolic resin transfer (CB) sheets to be used in conjunction with the dye receiving (CF) sheets described above: 
     (E) 1200 grams of para-phenylphenol resin (PPP resin) were dissolved in 3200 grams of dibenzyl ether and 1600 grams of Magnaflux oil. Sufficient heat and agitation were applied to effect solution. 200 grams of EMA 31 (ethylene-maleic anhydride copolymer with a molecular weight range of 75,000 to 90,000) was dissolved in 1800 grams of deionized water with sufficient heat and agitation to effect solution. The prepared EMA solution was diluted with 6000 grams of deionized water and the pH adjusted to 4.0 with 20% sodium hydroxide solution. The oil solution of PPP resin was then emulsified in the EMA water solution with a Cowles Dissolver at 25° C. Emulsification was continued until an average oil drop size of approximately 2 microns was attained. Total drop size distribution ranged from approximately 0.5 microns to 15 microns. The resulting emulsion was then transferred to a water bath controlled at 55° C. and with rapid agitation, 1000 grams of 80% Resloom 714 (etherified methylol melamine) diluted with 1000 grams of deionized water was added. The resulting mix was kept at 55° C. for 2 hours under constant agitation to effect capsule formation. After 2 hours, the temperature was allowed to slowly equilibrate with the ambient temperature. Agitation was continued for an additional 16 hours. 
     (F) An oil solution of 1400 grams of para-octylphenol resin (POP resin), 3200 grams of dibenzyl ether and 1600 grams of Magnaflux oil was prepared using sufficient heat and agitation to effect solution. This solution was then encapsulated using the procedure described above. 
     Coating slurries of the above capsules were prepared having the following composition: 
     
         ______________________________________      V           VI      Parts           Parts   Dry    Parts                               Parts Dry      Wet  Dry     %      Wet  Dry   %______________________________________PPP Capsules (E)        26.60  12.50   71.4POP Capsules (F)                 27.30                                 12.50 71.4Stilt Starch 3.20   3.12    17.9 3.20 3.12  17.9Stayco S Starch        6.30   .63     3.6  6.30 .63   3.6Dow Latex 638        2.50   1.25    7.1  2.50 1.25  7.1(carboxylated styrene-butadiene latex)Water        26.40  --      --   25.20                                 --    --Totals       65.00  17.50   100.0                            65.00                                 17.50 100.0Coating Solids        27%           27%Viscosity    68 cps        68 cps______________________________________ 
    
     These coating slurries were applied to a 34 lb. base sheet at a rate of 3.75 lbs. (500 sheets measuring 25 by 38 inches) with an air knife coater. In addition, formulation V was applied to the back side of 34 lb. base sheets having the first side coated with formulations III and IV, respectively, to make CFB (coated front and back) papers. 
     The CB, CFB and CF papers prepared above were placed in proper imaging sequence and typewriter images were produced thereon. The intensity of these images after print development (24 hours) was determined with an opacimeter. The images were then subjected to various exposures to determine (a) The stability of the imaged print (fade resistance) and (b) The ability of the dye containing receiving (CF) sheet to produce a new print after exposure (CF Decline Resistance), shown below as &#34;New Print Intensity&#34;. 
     The CF sheets prepared in Example 1 produced the following test results: 
     48 Hour South Window Exposure Test. Imaging done with IBM Memory Typewriter using an &#34;X&#34; character: 
     
         ______________________________________                  Intensity        Original  After Exposure                              New PrintCB    CF     Intensity (Fade)      Intensity______________________________________V     I      40        41          65VI    I      52        53          75V     II     40        52          88VI    II     56        74          96______________________________________ 
    
     The CF sheets prepared in Example 2 produced the following test results: 
     1. 48 Hour Fluorescent Light Box Exposure Test. Imaging done with IBM Executive Typewriter using 4-bar cross hatch character: 
     
         ______________________________________                    Intensity           Original After Exposure                               New PrintCB       CF     Intensity                    (Fade)     Intensity______________________________________V        III    38       48         55V        IV     51       74         78V/III CFB       49       51         56V/IV CFB        52       68         75______________________________________ 
    
     2. 3 week 140° F. oven exposure test. Imaging the same as in Test 1 above: 
     
         ______________________________________                    Intensity           Original After Exposure                               New PrintCB       CF     Intensity                    (Fade)     Intensity______________________________________V        III    40       49         52V        IV     48       49         75V/III CFB       48       45         51V/IV CFB        51       51         68______________________________________ 
    
     3. 9 week wall test (ambient conditions). Imaging done with a solid block character using an IBM Selectric typewriter: 
     
         ______________________________________                    Intensity           Original After Exposure                               New PrintCB       CF     Intensity                    (Fade)     Intensity______________________________________V        III    32       42         44V        IV     34       54         76V/III CFB       33       42         45V/IV CFB        35       55         76______________________________________ 
    
     4. 7 week wall test (ambient conditions). Imaging done as in Test 3 above 
     
         ______________________________________                    Intensity         Original   After Exposure                               New PrintCB    CF      Intensity  (Fade)     Intensity______________________________________V     III     33         38         48VI    III     44         56         54V     IV      34         45         72VI    IV      57         73         89______________________________________ 
    
     Therefore, when used as described herein and when compared with Crystal Violet Lactone at the same concentration, Pyridyl Blue shows the following characteristics: 
     Equivalent image strength with respect to CVL when imaged with PPP Resin solution. 
     Superior image strength with respect to CVL when imaged with POP Resin solution. 
     Superior print stability (fade resistance) with respect to CVL under all exposed tests. 
     Superior resistance to degradation (CF decline) with respect to CVL under all exposure tests. 
     In a typical procedure the Pyridyl Blue employed in the above examples is prepared in the following manner. A quantity of 58.0 g (0.188 mole) of (1-ethyl-2-methylindol-3-yl) (3-carboxypyridin-2-yl)ketone and its isomer is stirred for 2 hours at 60°-65° C. with 35.3 g (0.188 mole) of N,N-diethyl-m-phenetidine and 250 ml of acetic anhydride. The reaction mixture is poured into 500 ml of water and the acetic anhydride hydrolyzed by slowly adding 450 ml of 29% ammonium hydroxide. After stirring for 2 hours, the resulting solid is filtered. It is washed with water, 200 ml of 40% methanol/water and 50 ml of petroleum ether (b.p. 60°-110° C.). The solid is dried in a 75° C. oven to a constant weight of 80.5 g (90%) of the desired product, Pyridyl Blue, mp 134°-137° C. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications are intended to be included within the scope of the following claims.