U.S. patent number RE30,797 [Application Number 05/850,027] was granted by the patent office on 1981-11-17 for associated dye salts and method of forming colored indicia therewith.
This patent grant is currently assigned to Scott Paper Company. Invention is credited to Chester Davis.
United States Patent |
RE30,797 |
Davis |
November 17, 1981 |
Associated dye salts and method of forming colored indicia
therewith
Abstract
.Iadd.Described herein are methods of printing which comprise
applying to an unfired silicate surface characterized by high
ionizing power a substantially colorless associated salt of an
arylmethane dye base characterized by a logarithmic dissociation
constant below 7 and an organic sulfinic acid whereby physical
contact of the associated compound and the silicate dissociates the
compound to the intensely colored cation of the dye and produces
color on the silicate surface. .Iaddend. .Iadd.
Inventors: |
Davis; Chester (Cincinnati,
OH) |
Assignee: |
Scott Paper Company
(Philadelphia, PA)
|
Family
ID: |
25307080 |
Appl.
No.: |
05/850,027 |
Filed: |
November 9, 1977 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
800377 |
Mar 19, 1959 |
|
|
|
|
658249 |
May 10, 1957 |
|
|
|
|
533877 |
Sep 12, 1955 |
|
|
|
|
533878 |
Sep 12, 1955 |
|
|
|
Reissue of: |
200052 |
Jun 5, 1962 |
03193404 |
Jul 6, 1965 |
|
|
Current U.S.
Class: |
427/288;
101/DIG.29; 427/150; 503/201; 503/219; 503/224 |
Current CPC
Class: |
B41M
5/1366 (20130101) |
Current International
Class: |
B41M
5/132 (20060101); B41M 5/136 (20060101); B41M
005/14 () |
Field of
Search: |
;427/150,288
;101/426,DIG.1 ;106/31 ;260/391,57R,501.18,501.21 ;282/275
;346/135 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
507001 |
|
Nov 1954 |
|
CA |
|
14822 of |
|
1888 |
|
GB |
|
Other References
Karrer, "Organic Chemistry", 1946, p. 406. .
Hinsberg, "Veber Benzolsulfinsaure als Reagens. II", Berichte der
Deutschen Chemischen Gesellschaft, vol. III (1897), pp. 2803-2805.
.
Hinsberg, "Uber die Reaktion Zwischen Aromatischer Sulfinsaure und
Di-und Triphenyl-Carbinol", Berichte der Deutschen Chemischen
Gesellschaft, vol. 50 (1917), pp. 468-473. .
Beilsteins Handbuch der Organischen Chemie, Vierte Auflage,
Dreizehnter Band, 1930, pp. 700 and 704..
|
Primary Examiner: Hoffman; James R.
Attorney, Agent or Firm: Connolly and Hutz
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS .Iaddend.
This application is a continuation-in-part of my copending
application Ser. No. 800,377, filed on Mar. 19, 1959, for
"Colorless Dye Salts and Nonstaining Transfer Sheet," now
abandoned.Iadd., said application Ser. No. 800,377 in turn being a
continuation-in-part of application Ser. No. 658,249, filed May 10,
1957, now abandoned, and said application Ser. No. 658,249 being a
continuation-in-part of applications Ser. Nos. 533,877 and 533,878
both filed Sept. 12, 1955 and both now abandoned. .Iaddend.
Claims
Having described my invention, I claim:
1. The method of printing which comprises applying to an unfired
silicate surface characterized by high ionizing power a
substantially colorless associated salt of an arylmethane dye base
characterized by a logarithmic dissociation constant below 7 and an
organic sulfinic acid whereby physical contact of the associated
compound and the silicate dissociates the compound to the intensely
colored cation of the dye and produces color on the silicate
surface.
2. The method of printing which comprises applying to a surface
characterized by high ionizing power a substantially colorless
liquid, said liquid comprising a substantially colorless associated
salt wherein the anion is an organic sulfinic acid anion and the
cation is a colored dye cation of an arylmethane dye base
characterized by a logarithmic dissociation constant below 7,
whereby physical contact of the colorless associated compound and
the ionizing surface dissociates the compound to the intensely
colored cation of the dye and produces color on the ironizing
surface.
3. The method of claim 2 wherein the colored dye cation of an
arylmethane dye base characterized by a logarithmic dissociation
constant below 7 is an N,N'-alkylated-4,4'-diaminobenzhydryl
cation.
4. The method of claim 2 wherein the colored dye cation of an
arylmethane dye base characterized by a logarithmic dissociation
constant below 7 is a triarylmethane dye cation.
5. The method of printing which comprises applying to a surface
having thereon a coating comprising an unfired silicate
characterized by high ionizing power a substantially colorless
liquid which comprises an oil-soluble, water-insoluble salt wherein
the anion is an organic sulfinic acid anion and the cation is a
colored dye cation of an arylmethane dye base characterized by a
logarithmic dissociation constant below 7, whereby physical contact
of the colorless associated salt and the ionizing silicate
dissociates the salt to the colored cation of the dye to provide a
colored print. .[.6. A recording fluid comprising a solution in a
nonaqueous solvent of an associated arylmethane dye salt wherein
the anion is an organic sulfinic acid anion and the cation is the
intensely colored cation of an arylmethane dye base characterized
by a logarithmic dissociation constant below 7..]. .[.7. A
recording fluid comprising a solution in a nonaqueous solvent of an
associated dye salt wherein the anion is an organic sulfinic acid
anion and the cation is an N,N'-alkylated-4,4'-diaminobenzhydryl
cation..]. .[.8. A recording fluid comprising a solution in a
nonaqueous solvent of an associated dye salt wherein the anion is
an organic sulfinic acid anion and the cation is the intensely
colored cation of Dinitro Crystal Violet Base..]. .[.9. A new
composition of matter comprising the associated dye salt wherein
the anion is an organic sulfinic acid anion and the cation is the
intensely colored
cation of Dinitro Crystal Violet Base..]. 10. The method of
printing which comprises applying to a surface characterized by
high ionizing power a substantially colorless associated salt of an
arylmethane dye base characterized by a logarithmic dissociation
constant below 7 and an organic sulfinic acid whereby physical
contact of the associated compound and the ionizing surface
dissociates the compound to the intensely colored cation of the dye
and produces color on the ionizing surface. .[.11. A recording
fluid comprising a solution in a nonaqueous solvent of a
substantially colorless associated dye salt wherein the anion is a
xylenesulfinic acid anion and the cation is an
N,N'-alkylated-4,4'-diaminobenzhydryl cation..]. .[.12. A recording
fluid comprising a solution in a nonaqueous solvent of a
substantially colorless associated dye salt wherein the anion is a
diethylbenzenesulfinic acid anion and the cation is an
N,N'-alkylated-4,4'-diaminobenzhydryl cation..]. .[.13. A new
composition of matter comprising the substantially colorless
associated dye salt wherein the cation is an
N,N'-alkylated-4,4'-diaminobenzhydryl cation and the anion is a
xylenesulfinic acid anion..]. .[.14. A new composition of matter
comprising the substantially colorless associated dye salt wherein
the cation is an N,N'-alkylated-4,4'-diaminobenzhydryl cation and
the anion is a diethylbenzenesulfinic acid anion..]. .[.15. A new
composition of matter comprising the substantially colorless
associated dye salt of xylenesulfinic acid and
4,4'-bis(dimethylamino)benzhydrol..]. .[.16. A new composition of
matter comprising the substantially colorless associated dye salt
of diethylbenzenesulfinic acid and
4,4'-bis(dimethylamino)benzhydrol..]. .Iadd. 17. The method
according to claim 10 wherein the associated salt is Michler's
hydrol p-toluenesulfinate.
Description
The purpose of this invention is to describe a new type of
recording system which depends for its action upon the equilibrium
between a colored and a colorless dye salt. In particular, it has
been found that the sulfinic acid salts and hydrazoic acid salts of
intensely colored cations from diarylmethane and triarylmethane dye
bases characterized by a logarithmic dissociation constant below 7
may exist in two forms: (1) an intensely colored dissociated form
and (2) a substantially colorless associated form depending upon
environmental conditions (solvent, temperature, etc.) which
prevail.
This equilibrium has been admirably adapted to the preparation of
nonstaining nonaqueous recording solutions for use in marking
fluids, spirit duplicating, and as a recording media for
nonstaining copy papers.
Previous workers in the field of colorless or nonstaining recording
systems have always utilized chemical reactions between two active
chemical components to obtain colored characters. For example,
earlier workers, such as Groak, used metathetical ionic reactions
between colorless cations and anions to form colored compounds,
such as iron gallate. These reactions required moist conditions,
and coatings containing such hygroscopic reagents were subject to
premature rupture and discoloration. More recent workers, such as
Davis and Thacker, have used nonaqueous systems for their
reactions, such as the formation of a colored salt from a colorless
base and a strong acid. All of these systems are chemical in nature
and possess certain inherent defects in their actual commercial
application.
Inasmuch as the major objection to the use of triarylmethane dye
solutions in recording systems (marking fluids, typewriter ribbons,
copy papers, etc.) is due to the ability of these dyes to stain
skin and clothing an intense color, what has long been desired is
an intensely colored dye salt which will not stain ordinary
surfaces but will give an intense character only on a desired
surface.
The author of the present invention has now found that the sulfinic
acid salts and hydrazoic acid salts of diarylmethane and
triarylmethane color bases characterized by a logarithmic
dissociation constant below 7 may exist completely in the colored
dissociated form, completely in the substantially colorless
associated form, or in equilibrium between the two forms depending
upon the ionization power of their environment.
In particular, it has been found that upon exposure to heat or upon
contact with highly ionizing reagents or solids such as unfired
kaolin, bentonite, and similar surfaces bearing a high permanent
electric dipole moment, the colorless associated form dissociates
into ions, one of which is intensely colored, which dissociation
can be used for the recording of data and for duplicating
purposes.
It appears that equilibrium exists between the forms: ##STR1##
which may be written in the form of Kekule bonds as: ##STR2## where
Y is chosen from the group consisting of aliphatic radicals having
from one to twelve carbon atoms, phenyl, and substituted phenyl.
##STR3## in which the quanticule (e.sub.2.sup.- v) of the sulfinate
and azide ions contribute to the screening of the central carbon
core only under low energy conditions; but upon exposure to higher
energy, ionizing conditions, the central core is now adequately
screened by only three substituents, and the molecule ionizes.
The peculiar stability of Crystal Violet Cyanide apparently is due
to the fact that the electrically unbalanced cyanide ion
effectively distorts the Crystal Violet ion so that maximum
screening of the central core is achieved. So strongly screened is
the central core in Crystal Violet Cyanide that dissociation occurs
only under the high-energy conditions existing in the far
ultra-violet region; and Crystal Violet Cyanide cannot be
dissociated by heat or chemical action alone (lead peroxide will
not oxidize it to Crystal Violet dye). Only in alcohol solutions
(and in similar ionizing solvents) exposed to extremely high-energy
ionizing radiation will the molecule ionize. This is not
remarkable; for in this high-energy spectral region even oxygen
dissociates to form ozone.
The dye salts of the present invention are chosen so that an
essentially unsaturated core is completely screened by other groups
only at low-energy (normal) conditions. Upon exposure to a
high-energy environment, the core is then adequately screened by
fewer groups; and the molecule dissociates into ions, at least one
of which is colored. The dye salt to be used for a given
application becomes a matter of determining the screening
characteristics of the ions used. Previous experience in this area
before the work of the author of the present invention is extremely
limited. Many chemists assume that all organic azides are
dangerously explosive; yet the author of the present invention has
found certain organic azides (which are ionic in character but are
not ionized) to be quite stable. Michler's hydrol azide, for
example, melts at 80.degree. C. and begins to decompose slowly at
160.degree.-220.degree. C., resembling sodium azide in this
respect. No explosion has ever been obtained under normal working
conditions with this compound, which is very soluble in
toluene.
The only know member of this type, that from Michler's hydrol and
benzenesulfinic acid (called
phenyl-(4,4'-bis(dimethylamino)-benzhydryl)-sulfone) is completely
insoluble at room temperature in the usual solvents used in
recording systems. It has been found by the author of the present
invention, however, that the use of aliphatic sulfinic acids and
the use of substituted aromatic sulfinic acids, where the
substituent is one of a series of oil-solubility promoting
(lipophilic) groups such as alkyl, halogen, ether, etc., gives
solvent-soluble sulfinates which are stable, substantially
colorless, and non-staining to skin, paper, and textile fibers.
From the viewpoint of classic theory, these salts are for the most
part the salts of weak bases and moderately strong acids. It is
axiomatic in chemistry that the salts of strong bases-strong acids
(sodium chloride, Crystal Violet Chloride, etc.) are always one
hundred percent dissociated; but the salts of weak acids-strong
bases and of weak bases-strong acids may be more or less associated
depending upon environmental conditions. It would appear that one
method of adapting other dye bases for use in the present invention
would be to lower their base strength by suitable substitution.
This is achieved in quanticule-donating systems by incorporating
quanticule-attracting groups (nitro, trifluoromethyl, etc.) into
the aryl group.
It was found that Crystal Violet dye, for example, could be
nitrated to give
2,2'-dinitro-4,4',4"-tris(dimethylamino)-triphenylcarbinol, a weak
base. This weak base can form undissociated dye salts with suitable
anions as well as dissociated dye salts with other anions.
Similarly, 2-nitro-4',4"-bis(dimethylamino-triphenylcarbinol is
easily prepared for use in the present invention, as are other
nitrated triarylmethane dye derivatives. While these nitrated dye
bases containing only one nitro group are not always completely
nonstaining, their associated salts are nonstaining and one can use
associated salts for purposes where the free color bases are
unsatisfactory.
Although the associated salts of nitrated triarylmethane dye bases
are not completely colorless, being a light orange in color,
transfer sheets containing these salts are the same light yellow
color as standard yellow commercial papers and may be substituted
into any form where a pale-colored base web is not objectionable.
The nonstaining nature of solutions of these salts renders their
use far more attractive than the violet-colored, strongly-staining
solutions of Methyl Violet Oleate.
The use of other meta-directing groups than the nitro group to
reduce the base strength of triarylmethane dyes, such as
trifluoromethyl and N,N-dialkylsulfonamido, will also furnish
intermediates for the dye salts of the present invention. In these
cases, the parent carbinol bases are substantially colorless, as
are the resultant salts.
The salts of the present invention are all water-insoluble.
Inasmuch as water is ionizing in nature, colorless solutions of
these associated salts in acetone, alcohol, etc. become colored
upon addition of water; for this reason the associated salts of the
present invention should be used only in systems which do not have
an appreciable water-content. Water-soluble salts of triarylmethane
color bases are discussed in my copending application, Stable
Triarylmethanesulfonic Acid Derivatives and Method of Forming
Colored Indicia Therewith, Ser. No. 200,056, filed June 5,
1962.
The author has found that certain unfired silicates such as
diatomaceous earth, kaolin, and bentonite possess high ionizing
properties apart from their acid-base and oxidation-reduction
properties. A clay molecule may be pictured as a large molecule of
polymerized silica containing calcium, iron, and other cations. The
iron silicate structure gives oxidizing properties to the clay and
the calcium silicate gives acidic and ion-exchange properties to
the clay; but it is the polymerized silica structure which gives a
high electric dipole moment over the surface of the clay. This
electric dipole is stable until the clay is calcined at high
temperature, at which point the electric dipole moment disappears;
and the aforementioned clays lose their ionizing properties.
Although other workers in the recording field, notably Bjorksten,
Green, and Bour, have utilized certain silicates in recording
papers, no worker has yet utilized the clays as other than chemical
reagents. It is the purpose of this application to describe a
practical utilization of the ionizing properties of silicates
possessed of a high dipole moment.
The compounds of the present invention offer certain advantages
over the color bases from which they are derived: (1) As the method
of color formation by dissociation is different from the method of
color formation by reaction of a dye base with an acid, there is
oftentimes a marked increase in the rate of reaction. Dinitro
Crystal Violet Base, for example, when pure forms a colored salt
with acid silicates only very slowly (3-5 minutes or longer); but
the dissociation of Dinitro Crystal Violet Azide to the colored ion
under the influence of the acid silicates' electric dipole moment
is immediate, and the intense colored print appears immediately
upon recording with this azide. (2) The stability and reactivity of
certain color bases, such as mononitro Crystal Violet Base, which
have logarithmic dissociation constants between 5 and 7, is
improved, and this is of value in manifolding sheets which must be
stored indefinitely before use. (3) The associated salts formed can
be more safely handled without chemical staining than can the more
reactive color bases because of lower water-solubility (i.e., they
are less-soluble in the skin perspiration).
While the compounds of the present invention cannot be used in
aqueous soluitons and are more reactive than the water-soluble
triarylmethanesulfonates, which are disclosed in my copending
application, they do, however, have applications in recording
systems where a non-volatile color-former is desired which will
record colored indicia on selected areas from a lipophilic
solvent.
Description
Michler's hydrol (4,4'-bis-(dimethylamino)-benzhydrol), ethyl
hydrol (4,4'-bis-(diethylamino)benzhydrol), Dinitro Crystal Violet
Carbinol, and other compounds of this type are dissolved in glacial
acetic acid to form the intensely colored acetate. To this colored
dye solution is added the desired sulfinic acid either as the free
sulfinic acid or as its sodium salt (the sodium salt form is
preferred because the sulfinic acid salts have greater storage
stability than the free sulfinic acids which tend to polymerize
upon standing in the air) until the intense color is discharged or
until the solution becomes a markedly lighter color. The sulfinate
may deposit at this time or may be retained in solution. The
solution is then poured into cold water or cold ammonium hydroxide
solution to precipitate out the water-insoluble sulfinate. The
precipitate is collected, washed with water, dried, and
recrystallized from alcohol to give the colorless sulfinate.
The reaction may be carried out in dilute aqueous acids or in
acidic alcohol. All that is necessary is that the dye base should
be converted to the colored salt before adding the sulfinate ion.
The sulfinic acids may be obtained by decomposition of a
sulfur-dioxide containing diazonium salt solution (Gattermann
reaction), by reduction of the sulfonyl chloride with zinc duct or
sodium sulfite, or by the aluminum chloride catalyzed addition of
sulfur dioxide to an olefinic or aromatic compound. The yield of
colorless sulfinate is usually above ninety percent and is often
quantitative.
The melting points of these colorless dye salts depends on the rate
of heating and cannot be used to characterize pure isomers (ortho,
meta, para, for example); for comparison purposes, however, the
melting points of some of the more simple colorless dye salts are
listed below:
______________________________________ Michler's hydrol azide
.degree.C. 79-80 Michler's hydrol p-toluenesulfinate .degree.C.
183-184 Michler's hydrol xylenesulfinate .degree.C. 156-157
Michler's hydrol 2,5-dichlorobenzene- sulfinate .degree.C.
177-178.5 Michler's hydrol 3,4-dichlorobenzenesul- finate
.degree.C. 191-192 Michler's hydrol p-ethoxybenzenesul- finate
.degree.C. 161-162 Ethyl hydrol p-toluenesulfinate .degree.C.
142.5-143.5 Ethyl hydrol xylenesulfinate .degree.C. 130-131
Michler's hydrol ethylsulfinate .degree.C. 148.5-150 Michler's
hydrol n-butylsulfinate .degree.C. 112-114
p-Methoxy-p-dimethylaminobenzhydryl azide Oil
p-Methoxy-p-dimethylaminobenzhydryl p-toluenesulfinate .degree.C.
84-86 Michler's hydrol dodecylbenzenesulfinate Oil
______________________________________
The most light-stable colored indicia are obtained from the salts
of substituted triarylmethane color bases such as: ##STR4## where R
is a lower alkyl group or hydrogen.
Color is developed in the associated dye salts after they have been
placed or transferred to a receiving sheet, as imprinted indicia,
by exposing said receiving sheet to a highly ionizing environment.
Three highly ionizing environments are particularly useful for this
purpose. These are a polarizing reagent, a high temperature, and a
surface carrying a high permanent electric dipole moment. For
example, if a recording fluid comprising a sulfinate salt and a
solvent therefor is used to imprint indicia on an ordinary paper,
after the solvent has evaporated color is imparted to the imprinted
dye salt by exposing the paper either to an elevated temperature or
to a polarizing reagent, such as ammonium persulfate, water, etc.
In other words, color is imparted to the dye salt either by heating
the imprinted dye salt or an imprinted dispersion thereof in a
nonvolatile vehicle, or alternatively by exposing the paper to a
polar developing fluid. The developing fluids preferably contain
water, but water alone cannot be used by itself since the sulfinate
dye salts are insoluble therein. It is necessary therefore in the
case of water as a developing reagent to use in addition to water a
mutual solvent for it and the sulfinate dye salt. Among useful
solvents are acetone, ethanol and other alcohols,
dimethyl-sulfoxide and the like. Alternatively, if the receiving
sheet is coated with a film comprising a material having a
permanent electric dipole moment, this surface comprises a third
type of highly ionizing environment. The associated dye salts of
this invention dissociate immediately upon contact with a surface
of this type, thus giving a highly colored cation directly. A
recording fluid or a transfer sheet employing associated dye salts
can be used therefore in conjunction with a specially coated paper
having a high permanent electric dipole moment to provide novel
recording systems.
Exemplary of the recording fluids of this invention is a recording
fluid comprising a solution of Michler's hydrol
diethylbenzenesulfinate in oleic acid, which solution can be used
to saturate a stamp pad. When such a recording fluid is transferred
by means of a stamp to a fabric coated with a material having a
high permanent electric dipole moment, the indicia imparted thereto
become colored immediately. Alternatively, the stamp can be used to
transfer the recording fluid to an ordinary sheet of paper in which
case the color of the imparted indicia is developed by contacting
the paper with a developing fluid comprising, for example, 25
percent water and 75 percent acetone.
By way of further illustration, recording systems of this invention
can be prepared employing ethyl hydrol xylenesulfinate or an
equivalent colorless dyestuff salt of the type described above. In
a recording system of this type, such as carbon paper, the
associated dye salt is dispersed in a heavy oil or wax-oil mixture
and applied to a master sheet. Typewriter type, or a stylus, when
pressed against the surface of this master sheet, will cause some
of the associated dye salt to be transferred to a receiving sheet.
If the receiving sheet has an ionizing surface, an immediate color
will develop comprising the colored cation of the dye. If an
ordinary sheet is used, the color can be developed by the use of a
developing fluid or by heat as previously described.
The surfaces whose use is indicated in conjunction with the
associated dye salt of this invention are those which, as
previously stated, bear a high permanent electric dipole moment.
Numerous examples of this type of surface are known to the art.
Unfired silicates are particularly useful in this regard. Examples
of suitable ionizing surfaces are those prepared from unfired
silicates such as kaolin, bentonite, and the like. Papers bearing
such a coating can be manufactured by methods well known to the
art.
The recording fluids and recording systems of this invention will
not stain skin or fabrics until the final stage of their use when
the color is developed in situ on an ionizing surface or by the use
of developing chemicals or by heat. In addition, "carbon" and other
copy papers and master sheets prepared from the associated dye
salts of this invention are either colorless or very
lightly-colored. Thus, the recording fluids and recording systems
provided by this invention are especially advantageous when
compared with those commonly employed. Furthermore, since the
surfaces of most fabrics are not highly ionizing for the associated
salts of the present invention, the recording fluids employed by
this invention are nonstaining and therefore are particularly
useful for the printing of price tags or quality control tags on
bolts of goods, dresses, clothing and the like.
An example of a recording solution contains a colorless associted
dye salt is a 2% solution of Michler's hydrol azide in paraffin
oil. This gives an intense blue coloration with an unfired
kaolin-coated receiving sheet.
Another example of this invention is a 2.5% solution of dinitro
Crystal Violet Azide in toluene. This gives an immediate blue-black
coloration with an unfired kaolin-coated receiving sheet.
Another example of this invention is a 3% solution of ethyl hydrol
xylenesulfinate in distilled oleic acid. This gives an intense blue
coloration with an unfired diatomaceous earth-coated paper. A blue
coloration is also obtained when the colorless prints on ordinary
paper are heated to about 150.degree.-175.degree. C.
Another example of this invention is a 2.5% solution of Michler's
hydrol-xylenesulfinate in chlorinated diphenyl. This gives an
intense blue coloration upon contact with an activated
silica-coated paper.
Still another example of this invention is a 3% solution of
p-methoxy-p'-dimethylaminobenzhydryl azide in chlorinated diphenyl.
This gives a wine-red color upon contact with an activated
silica-coated paper. This has very poor light-stability.
Still another example of this invention is a three percent solution
of dinitro Fuchsin-xylenesulfinate in chlorinated diphenyl. This
gives a magenta color upon contact with an activated silica-coated
paper.
Similar recording fluids can be prepared by substituting other
associated salts of diarylmethane and triarylmethane dyes falling
within the scope of this invention in the above nonionizing
solvents or their equivalents. These recording fluids will yield
colored indicia upon contact with a highly ionizing surface or, if
printed upon a plain surface, the color can be developed by
contacting the surface with an ionizing reagent such as aqueous
alcohol or simply by applying heat to the surface.
For the preparation of transfer sheets, the associated salts of
arylmethane dyes can be dissolved in a hot wax melt and then coated
onto the base web in a standard hot melt coating machine. The
colorless dye salt should be sufficiently soluble in the cold wax
mixture so that it does not crystallize out from the hot melt upon
cooling. In dissolving the associated dye salt, temperatures in
excess of 110.degree. C. should be avoided since the compounds will
dissociate into ions at temperatures much above 135.degree. C.
In general, in preparing transfer sheets the wax is melted, a
nonvolatile, nonionizing plasticizing oil is added, as for example
paraffin oil or oleic acid, and the associated dye salt is
dissolved in the hot melt, usually at about 85.degree. C. If a
filler or an activator is desired, it can be dispersed in the hot
melt at this point. Among useful fillers are starches, starch
derivatives, and a fired diatomaceous earth sold under the
trademark "Dicalite."
More specifically, a transfer sheet using the recordng fluids of
this invention is prepared by melting together 35 parts of
Gersthofen wax, 15 parts of high-melting (155.degree. F.) paraffin
wax, and 50 parts of a nonvolatile paraffin plasticizing
lubricating oil with a flash point over 400.degree. F. and a
viscosity of 150 Saybolt seconds. To this mixture is added at 180
F. an amount of ethyl hydrol xylenesulfinate equal to 2.5 percent
of the amount of lubricating oil used. The solution is stirred
until clear, and the molten wax is applied to paper by standard
coating procedures to give a coating weight of 5 lbs./ream.
Another example of the process of preparation of a transfer sheet
utilizing the recording fluids of the present invention comprises
melting together 36 parts by weight of refined ouricury wax, 19
parts by weight of a high melting paraffin wax, and 45 parts by
weight of oleic acid containing 3 percent Michler's hydrol
diethylbenzenesulfinate. This melt is coated on paper at a
temperature near the solidifying point in order to minimize "strike
through" into the base paper. A transfer sheet prepared in this
fashion, when used in conjunction with a receiving sheet coated
with unfired diatomaceous earth, gives an intense blue transfer
pattern on the receiving sheet.
It should be clearly understood that the invention is not limited
to the examples set forth but is generally applicable to any
associated dye salt which is water-insoluble and which can be
ionized to a colored cation by application of heat or by contact
with highly ionizing liquids or solids.
It is also to be understood that the associated dye salts of this
invention may be used to make recordings on appropriate surfaces by
any desired or conventional method or technique. For instance, the
salt dissolved in a solvent may be used for direct printing on
appropriately coated paper or the salt may be utilized as a
component of the coating of a transfer sheet. In other words, the
recording media of this invention may be used in a great variety of
recording, printing, and manifolding systems.
The invention will be better understood in relation to the
accompanying drawing which is a diagrammatic representation of the
physical dissocation which takes place in the practice of this
invention. FIG. 1 of the drawing discloses colorless associated
molecules RX of the associated dye salt of an organic sulfinic acid
and an arylmethane dye base characterized by a logarithmic
dissociation constant below 7 wherein R.sup.+ is the dye cation and
X.sup.- is the sulfinic acid anion and an unfired silicate surface
S characterized by high ionizing power wherein +--+-- represents
the electric dipole moment on the silicate surface. FIG. 2
represents the change which takes place when the colorless
associated molecules contact the electric dipole moment of the
ionizing surface whereby dissociation of the colorless salt RX to
the intensely colored cation R.sup.+ of the dye occurs to form
color on the ionizing surface.
* * * * *