Record material

A sensitized record sheet for developing useful color in oily, colorless, chromogenic dye-precursor inks applied thereto. Said record sheet is acid-reacting and bears a liquid ink comprising a non-evaporable liquid organic solvent having dissolved therein an acidic phenolic resin and a lower alkyl gallate.

BACKGROUND OF THE INVENTION 
This invention relates to record sheets bearing an acid-reacting, 
substantially colorless, liquid ink which is readily applied to record 
material in order to make sensitized sheets that will develop color in 
substantially colorless base-reacting chromogenic inks applied thereto. 
Acid-reacting sheets which develop color in applied colorless chromogenic 
inks are known to the art. Such sheets have previously been sensitized by 
a coating of acidic solid material such as an acid clay or solid particles 
of acidic phenolic resin. 
It is an object of this invention to provide an acid-reacting sensitized 
record sheet that can be readily made by standard printing operations, 
such that a printer can prepare the sensitized sheet at will on any record 
material base without having to stock several different grades and colors 
of sensitized record sheets that have previously been coated with the 
sensitizing material. It is a further object of this invention to provide 
an acid-reacting sensitized record sheet material, the manufacture of 
which does not involve the evaporation of a volatile organic 
coating-vehicle or printing-vehicle. It is a further object of this 
invention to provide an acid-reacting sensitized record sheet without the 
use of water as a coating vehicle with the attendant problems of drying as 
well as cockling, buckling and surface roughening that is commonly 
encountered when a water solution or slurry is applied to a paper surface. 
The objects of this invention have been met by the application of an 
organic liquid solution of an acidic phenol formaldehyde resin and a lower 
alkyl gallate. The organic liquid solvent material is selected to be 
non-evaporable so as to remain liquid on the record sheet surface. 
The record sheet is preferably paper or other fibrous material such as the 
so-called plastic papers. When the acid-reacting sensitizing ink of this 
invention is applied to a fibrous record sheet surface, such as paper, the 
sensitizing ink soaks into the fibers, remaining liquid and available for 
color-developing reaction with subsequently applied base-reacting 
colorless chromogenic inks. The acid-reacting sensitizing ink of this 
invention is substantially colorless, although some slight color can be 
tolerated. 
The acid-reacting sensitized sheets of this invention are designed for use 
with colorless chromogenic dye-precursor materials, particularly Crystal 
Violet Lactone, particularly as encountered in carbonless copy-paper 
sheets bearing a coating of pressure-rupturable microcapsules each of 
which contains a droplet of oil having dissolved therein the base-reacting 
colorless chromogenic material. Such microcapsule-coated record sheets are 
commonly used in the art, whereby writing pressure on the surface of the 
record material ruptures the microcapsule wall and expresses the oily 
droplets of base-reacting colorless chromogenic material for development 
of color in the writing pattern on the acid-reacting sensitized record 
sheet surface provided for that purpose. Exemplary of the 
microcapsule-coated sheets, useful with the acid-reacting sensitized 
record sheet of this invention, are commercial "NCR PAPER" CB SHEETS, 
having microcapsular coatings containing oily solution droplets of Crystal 
Violet Lactone (CVL) and benzoyl leuco methylene blue (BLMB). 
When a commercial "NCR PAPER" CB sheet is coupled with the sensitized sheet 
of this invention, so that the microcapsule-coated surface of the CB sheet 
is juxtaposed against the sensitized surface of the record sheet of this 
invention, writing pressure on the uncoated surface of the CB sheet will 
produce a copy of the writing on the sensitized record sheet of this 
invention. 
The sensitizing ink of this invention can be applied by any and all 
conventional printing techniques such as letterpress, dry offset, wet 
offset and rubber plate. The record sheet can be printed so as to 
sensitize the entire surface of the sheet or so as to selectively 
sensitize any portion of the record sheet as desired. Application of the 
sensitizing printing ink of this invention allows for much greater 
versatility than the sensitizing coatings currently used in the art, which 
coatings are commonly applied from water systems and are applied on 
full-width continuous coaters. One acid-reacting sensitized sheet, 
manufacturable by printing methods, has previously been known to the art 
in U.S. Pat. No. 3,466,184 which issued on application of Robert E. Miller 
on Sept. 9, 1969. The latter acid-reacting printed sensitized sheet, 
however, involves use of volatile solvent so as to leave a coating of 
solid acid-reacting phenolic material lightly invested on the record 
material surface. U.S. Pat. No. 3,466,185 which issued on application of 
John E. G. Taylor on Sept. 9, 1969, represents an improvement of U.S. Pat. 
No. 3,466,184 but also involves the use of evaporable solvent to leave a 
solid acid-reacting sensitizing material on the record sheet surface. 
The art has apparently previously been limited to solid acid-reacting 
sensitizing materials, because clays are of necessity solid, and phenolic 
resins generally do not develop satisfactory color in applied chromogenic 
oils except in the solid, undiluted state. The color-developing reaction 
between phenolic resins and chromogenic inks has been envisioned as a 
solution reaction, wherein the solid phenolic resin material is dissolved 
in the oil of the chromogenic ink as the instant of use. However, liquid 
solutions of acid-reacting phenolic resin materials have not been found 
useful in the art as sensitizing agents because they develop little or no 
color in applied chromogenic oils. 
The instant combination of acidic phenolic resin and lower alkyl gallate in 
non-evaporable oil solution has been found to overcome this problem, and 
to yield a satisfactory print with applied base-reacting chromogenic oils 
giving an intense and satisfactory color development with good fade 
resistance. 
The acid phenolic polymeric materials useful in this invention include 
oil-soluble phenol aldehyde polymers and phenol acetylene polymers. 
Among the phenolic polymers found useful are paraphenyl phenols and 
aklyl-phenol-acetylene resins, which are soluble in common organic 
solvents and possess permanent fusibility in the absence of being treated 
by cross-linking materials. A specific group of useful phenol-aldehyde 
polymers are members of the type commonly referred to as "novolaks", (as 
sold by Union Carbide Corp., New York, N.Y.) which are characterized by 
solubility in common organic solvents and which are, in the absence of 
cross-linking agents, permanently fusible. Generally, the phenolic polymer 
material found useful in practicing this invention is characterized by the 
presence of free hydroxyl groups and the absence of groups such as 
methylol, which tend to promote infusibility or cross-linking of the 
polymer, and by their solubility in organic solvent and relative 
insolubility in aqueous media. Again, obviously, mixtures of these 
phenolic polymers can be employed. 
Resoles, if they are still soluble, may be used, though subject to change 
in properties upon aging. 
A laboratory method useful in the selection of suitable phenolic resins is 
the determination of the infra-red absorption pattern. It has been found 
that phenolic resins showing an absorption in the 3200-2500 c.m..sup.-1 
region (which is indicative of the free hydroxyl groups) and not having an 
absorption in the 1600-1700 cm..sup.-1 region are suitable. The latter 
absorption region is indicative of the desensitization of the hydroxyl 
groups and, consequently, makes such groups unavailable for reaction with 
the chromogenic materials. 
The preparation of phenolic formaldehyde polymeric materials for practicing 
this invention is described in "Industrial and Engineering Chemistry", 
volume 43, pages 134 to 141, January 1951, and a particular polymer 
thereof is described in Example 1 of United States Pat. No. 2,052,093, 
issued to Herbert Honel on Aug. 25, 1936, and the preparation of the 
phenol-acetylene polymers is described in "Industrial and Engineering 
Chemistry", volume 41, pages 73 to 77, January, 1949. 
The gallate esters useful herein are lower alkyl esters, particularly 
propyl gallate, but also octyl gallate. 
The solvent useful herein must of necessity have a boiling point greater 
than three hundred degrees (300.degree.) C. and a vapor pressure not to 
exceed 1 mm. of mercury at one hundred degrees (100.degree.) C. Best 
results are generally achieved with a blend of solvents. The solvents are 
selected on the basis of their ability to promote a speedy reaction 
between the acid-reacting phenolic resin and the base-reacting 
chromogenic-material and preserve the solubility of all reacting 
components over a range of temperatures. Blends of an oily sulfonamide and 
a chlorinated paraffin are preferred for this purpose. Other high-boiling 
solvents which may be used to manufacture the sensitizing ink of this 
invention include chlorinated lower-alkyl phosphates, hydrogenated 
lower-alkyl abietates, lower-alkyl phthalates, lower-alkyl adipates, 
lower-alkyl phosphates, lower-alkyl glycallates, lower-alkyl sebacates, 
chlorinated biphenyls, lower-alkyl biphenyls, lower-alkyl biphenyl oxides, 
and lower-alkyl benzoates.

The invention having been set out above is here exemplified, but not 
limited, by the following specific examples in which percents represent 
percents by weight. 
EXAMPLE 1 
A sensitizing, acid-reacting printing ink was prepared of the following 
formulation: 
______________________________________ 
Range Preferred 
______________________________________ 
N-ethyl-o,p-toluenesulfonamide 
10-50% 35% 
Chlorinated paraffine oil (50-75% Cl) 
10-50% 35% 
Propyl gallate 0.5-10% 2% 
Tertiary butyl phenol formaldehyde 
1-40% 28% 
condensation product 
______________________________________ 
By N-ethyl-o,p-toluenesulfonamide is meant a mixture of 
N-ethyl-o-toluenesulfonamide, and N-ethyl-p-toluenesulfonamide, such as is 
commonly encountered in commercial preparations. The mixture sold as 
"Monsanto Santicizer 8" was used herein. Although more expensive, pure 
N-ethyl-o-toluenesulfonamide or pure N-ethyl-p-toluenesulfonamide could 
also be used herein. 
Paper sheets were printed by letterpress to give a color-developing, 
acid-reacting sensitized record sheet, which when coupled with an "NCR 
PAPER" CB sheet, gave, in response to writing pressure, an intense blue 
copy of the written indicia which was stable and resistant to fading when 
exposed to heat and light. 
EXAMPLE 2 
As in Example 1, a sensitized, acid-reacting record sheet was prepared by 
printing on paper the following formulation: 
______________________________________ 
Range Preferred 
______________________________________ 
N-ethyl-o,p-toluenesulfonamide 
10-50% 35% 
Hydrogenated methyl abietate 
10-50% 35% 
Propyl gallate 0.5-10% 2% 
Tertiary butyl phenol formaldehyde 
1-40% 28% 
condensation product 
______________________________________ 
The sensitized, acid-reacting record sheet produced by printing paper with 
the above formulation was satisfactory with respect to intensity of print 
and fade-resistance to heat and light. However, the formulation of Example 
1 was slightly better in intensity to the instant formulation. 
______________________________________ 
Range Preferred 
______________________________________ 
N-ethyl-o,p-toluenesulfonamide 
10-50% 11.9% 
Chlorinated paraffine oil (50-75% Cl) 
10-50% 17.8% 
Propyl gallate 0.5-10% 1.8% 
Tertiary butyl phenol formaldehyde 
condensation product 1-45% 41.7% 
Lipophilic pyrogenic silica 
1-4 % 2.8% 
Butyl benzoate 10-35% 24% 
______________________________________ 
The formulation set forth above was found to provide, in some applications, 
better physical characteristics in reduced viscosity with respect to the 
other formulations. 
Although the preferred embodiment of the composition has been described, it 
will be understood that within the purview of this invention various 
changes may be made in the form, proportion and ingredients and the 
combination thereof, which generally stated consist in a composition 
capable of carrying out the objects set forth, as disclosed and defined by 
the appended claims.