Desensitization system for carbonless copy paper

Desensitization of carbonless copy systems is provided by contacting an electron-accepting, color-reactant material capable of reacting with a substantially colorless chromogenic compound to form a visible image with a desensitizing agent comprising, in combination, a non-volatile, polyoxygenated compound and a strong chelating agent. In this manner, acid-reactive clay coatings typically used in carbonless copy paper systems are effectively desensitized and prevented from reacting with conventional chromogens, such as crystal violet lactone and benzoyl leuco methylene blue.

This invention relates to the desensitization of carbonless copy paper 
systems and to the desensitizing agents used therefor. More particularly, 
this invention relates to the desensitization of carbonless copy paper 
systems by the treatment of electron-accepting, color-reactant material 
with desensitizing agents for local desensitization. 
Carbonless copy paper systems have found a widespread commercial 
acceptance, and the transfer copy form of such system has been 
particularly successful. One of the most widely utilized transfer copy 
systems involves the use of a coating of microscopic capsules containing a 
colorless dye intermediate material, such as crystal violet lactone, which 
is dispersed or dissolved in an oily solvent forming the nucleus or core 
of the microcapsules. The microcapsular coating is provided on the 
underside of a transfer sheet, and upon local application of a stylus to 
the upper side of the transfer sheet, the underlying capsules are ruptured 
and the chromogenic compound is released and transferred to an underlying 
copy sheet that is coated with an electron-accepting material, such as 
acid-acting clay, that will react with the chromogen causing a visible, 
colored mark at the points where the microcapsules have been ruptured and 
the dye transferred. 
Transfer copy systems generally involve multi-part forms including a "CB" 
sheet, wherein the back or underside of the sheet is coated with the 
microcapsules containing chromogenic compounds, a "CFB" sheet which is a 
middle sheet having a coating on the upper side comprising an 
electron-accepting material of the Lewis acid type, and a coating of the 
image-forming microcapsules on its underside. The CB and CFB sheets are 
placed in register with a "CF" sheet, which has a coating of acid-acting 
clay or the like on its upper side. Thus, when the localized pressure is 
applied to the top side of the CB sheet, the microcapsules coated on the 
underside thereof are ruptured to release the chromogen, which reacts with 
the upper side of the CFB sheet to produce an image, while the very same 
localized pressure is transferred through the CFB sheet to the underside 
thereof in order to rupture the microcapsules thereunder and thus release 
the chromogenic material for reaction with the upper side of the CF sheet 
and produce an image thereon. 
Multi-part forms involving such transfer copy systems have been 
conventionally employed in various applications, such as for invoices for 
billing purposes or the like, wherein it is desired to exclude data on 
certain copies while including such data on others. Thus, for example, a 
customer's copy of an order acknowledgment should not contain data which 
must be entered on copies to be used for internal purposes. 
In order to provide multi-part forms, in which data can be included on one 
sheet, while excluded on another, the practice has been for the 
manufacturer of the carbonless copy paper system to provide the coated CF, 
CFB and CB paper webs to the printer, who then employs various 
desensitizing inks in order to block out certain selected areas of the 
form on one or more copies. The desensitizing agents prevent the chromogen 
that is released from the CB and CFB coating from contacting a sensitized 
CF surface and thereby form an image. However, many of the conventional 
desensitizing agents have certain drawbacks. For example, one conventional 
desensitizing agents involves ammonium compounds as desensitizers. 
However, organic ammonium compounds are quite toxic and may provide a 
health hazard for the user. 
Other desensitizing methods are based upon the use of lacquers which 
provide an impermeable barrier over the acid-reactive coating. However, 
this technique has the disadvantage that the lacquer compounds tend to 
become yellow upon aging. 
Still another form of desensitizing agent that has been proposed is 
ethylenediaminetetraacetic acid (EDTA), as described in U.S. Pat. No. 
3,809,668 to Yarian. However, the application of EDTA and its derivatives 
has generally been limited to specific types of copy systems, such as 
those employing dithiooxamide (DTO) or DTO derivatives as the dye 
precursor material. Although the suggestion has been made to use EDTA with 
the more conventional dye precursor materials, such as crystal violet 
lactone and benzoyl leuco methylene blue, coatings of EDTA on acid-acting 
clay does not provide complete desensitization at commercially desirable 
concentration levels. 
It has now been found that desensitization of carbonless copy systems can 
be provided without the toxicity of prior systems, while achieving greater 
desensitization with conventional chromogenic compounds, such as crystal 
violet lactone and benzoyl leuco methylene blue, by employing the 
desensitization agents of the present invention, which comprise, in 
combination, a non-volatile, polyoxygenated compound and a strong 
chelating agent. Moreover, it has been found that the instant composition 
provides desensitization for a wide range of dyes. 
Surprisingly, it has been discovered that the combination of strong 
chelating agents, such as EDTA, and its derivatives, in combination with 
non-volatile, polyoxygenated compounds, such as polyethylene glycols, 
provides desensitization in systems employing conventional chromogens, 
such as crystal violet lactone and benzoyl leuco methylene blue, which 
desensitization is not achievable utilizing either component, 
individually. 
As will be hereinafter demonstrated, the use of EDTA, alone, at the 
concentration indicated therein cannot provide the required 
desensitization to prevent the formation of a perceptible image employing 
either CVL or BLMB in combination with an acidic clay. Likewise, the use 
of polyethylene glycol, alone, is ineffective to inhibit color formation 
in the presence of BLMB. On the other hand, the apparent synergistic 
combination of the EDTA and the polyoxygenated compound provides excellent 
desensitization and the formation of a perceptible image with CVL and BLMB 
is prevented. 
As previously indicated, the desensitizing agent of the present invention 
comprises, in combination, a non-volatile, polyoxygenated compound and a 
complexing agent or strong chelating agent. 
Suitable polyoxygenated compounds include those possessing either 
polyhydroxy groups or polyether groups. Such compounds include those 
compounds, therefore, in which the oxygen exists either as hydroxy 
functional groups or ether functional groups, including polyethylene 
glycol; polyethylene oxide; polyethylene oxide-polypropylene oxide 
copolymers; polypropylene oxide; glycols; polyglycols; glycol ethers; 
glycol esters; polyglycol ethers and esters; pentaerythritol, sorbital, 
and their derivatives; and compounds containing polyethylene oxide groups, 
in general, such as nonionic surfactants. Accordingly, the only 
requirement for the polyoxygenated compound is that it contain oxygen as 
ether or hydroxy functional groups, and that it not be volatile or 
fugative enough to be lost from the CF coating. Thus, the polyoxygenated 
compounds of the present invention must have a lower volatility than 
glycerin or ethylene glycol, for example. 
Such polyoxygenated compounds, such as the polyethylene oxides and 
polyethylene glycols are commercially available from Union Carbide under 
the trade name "Polyox" and BASF Wyandotte under the trade name 
"Pluracol". Similarly, the polyethylene glycols, some of which are end 
capped by alkoxy groups containing from 1 to 5 carbon atoms, e.g., 
methoxy, ethoxy, propoxy, butoxy or pentoxy groups, are available from 
Union Carbide under the trade name "Carbowax", while polyethylene 
oxide-polypropylene oxide block copolymers are available under the trade 
names "Pluronic", "TETRONIC" and "Pluronic R", surfactants available from 
BASF Wyandotte. Still other surfactants, which may be nonionic, include 
ethoxylated nonylphenol, alcohol ethoxylates, and ethoxylated surfactants 
containing anionic groups. Likewise, humectants, such as sorbitol, 
pentaerythritol, and low molecular weight polyglycols, such as 
tetraethylene glycol, may be employed. Such polyoxygenated compounds, 
which may be employed in the present invention, are described throughout 
the literature, and include, for example, U.S. Pat. No. 2,674,619 to 
Lundsted, which describes polyoxyalkaline compounds of the type 
contemplated, and, and article by Stanton in "Soap and Chemical 
Specialties", 1957, Vol. 33, No. 6, pp. 47 et sequa. 
The polyoxygenated compound is used in combination with a complexing agent, 
which is a strong chelating agent. The expression "strong chelating agent" 
as used herein means those complexing or sequestering agents having a 
stability constant with metals, such as iron, zinc or cobalt of greater 
than about 6. Although it is not intended to limit the present invention 
to any particular theory or mechanism, it is believed that metal ions 
participate in the development of color from benzoyl leuco methylene blue, 
for example, and it is therefore the complexing and isolating of metal 
ions which prevents the formation of color from BLMB. 
Suitable complexing agents include ethylenediaminetetraacetic acid 
tetrasodium salt (EDTA-4Na), sodium citrate, the pentasodium salt of 
diethylenetriaminepentaacetic acid (DTPA-5Na), which is commercially 
available from Mona Industries Inc. under the trade name "Monaquest 
CAI-80", the trisodium salt of hydroxyethylenediaminetetraacetic acid 
(available as "Monaquest ICA-120"); the monosodium salt of 
dihydroxyethylglycine (available as "Monaquest CI"); nitrolotriacetic acid 
trisodium salt (commercially available from Dow Chemical as "Versene NTA") 
and the like. The preferred group of sequestering agents includes the EDTA 
and its derivatives as described in U.S. Pat. No. 3,809,668 and having the 
formula 
##STR1## 
wherein 
X is a divalent aliphatic or cycloaliphatic radical, preferably an alkylene 
radical of the formula 
##STR2## 
or a cyclic radical, such as cyclopentane, cyclohexane, etc., wherein the 
nitrogens are substituted 1,2- or 1,3-; 
A, B, C, and D are selected from the following group of substituents: 
hydrogen, an aliphatic or cycloaliphatic group, 
##STR3## 
where M is an alkali metal ion, such as sodium, potassium or lithium, and 
##STR4## 
where X' is similar to X, E and F are similar to A, B, C, and D; E or F 
can therefore be another --X--N(E)(F) unit, such that structures of the 
following type are formed: 
##STR5## 
where a is 0, 1, 2, 3, 4 or other small integer. A, B, C, and D must 
comprise at least one --CH.sub.2 --COOH or --CH.sub.2 --COOM group. 
The description and production of such compounds is defined in U.S. Pat. 
No. 3,809,668, as well as U.S. Pat. Nos. 2,901,335; 2,794,000; 2,428,353; 
and 3,234,173; the disclosure of EDTA and its derivatives as disclosed 
therein being incorporated herein by reference. 
As previously indicated, the preferred sequestering agent is 
ethylenediaminetetraacetic acid tetrasodium salt. 
In addition to the polyoxygenated and complexing compounds hereinabove 
discussed, an optional component in the form of triethanolamine may be 
employed. 
Any suitable concentration of polyoxygenated compound and complexing agent 
may be employed. Suitable amounts include between about 10 and about 0.5 
parts by weight of polyoxygenated compound per part by weight of 
complexing agent, preferably between about 3 and about 1 parts by weight 
of polyoxygenated compound per part by weight of complexing agent may be 
employed. The combination of polyoxygenated compound and complexing agent 
may be applied to the electron-acceptor sheet at a coat weight of between 
about 0.5 and about 4 pounds per ream, preferably between about 1 and 
about 2 pounds per ream. The term "ream" as employed herein is used to 
designated 3300 square feet. 
The desensitizing agents of the present invention may be utilized in an 
aqueous or non-aqueous coating solution, which is applied to acid-reactive 
receptor coatings, i.e., CF coatings of carbonless copy paper composites 
in order to render the CF coating inactive with respect to chromogenic 
compounds released under pressure from the corresponding CB sheet. In 
addition to the desensitizing agents, the desensitizing formulation may 
include any additives which are compatible with the desensitizing agents 
and which are typically used in printing ink formulations. Such additives 
may include pigments, dyes, viscosity modifiers, solvents, resins and the 
like. By reducing the content of the ionic components of the desensitizing 
composition, a non-aqueous solvent may be used, if desired. This permits 
the use of certain classes of compounds which are not water-soluble, but 
are active in the desensitization of CF coatings. 
The resulting desensitizing solutions may be applied using typical printing 
techniques in order to "spot" desensitize specific areas of a CF receptor 
sheet in a carbonless copy paper manifold. The application of the 
desensitizing agents of the present invention will provide non-reactive 
areas which will not form an image under pressure for use in multi-part 
forms, such as airline tickets, invoices and the like, in which certain 
parts of the form do not require all of the information shown on another 
part. 
The electron-acceptor materials which may be desensitized employing the 
desensitizing agents of the present invention include any 
electron-accepting agent including the well-known acidic materials 
conventionally employed in CF coatings including bentonite, kaolin, acidic 
clay, talc, aluminum silicate, calcium citrate, metal oxides, metal 
chlorides, or the like. Additionally, the chemical desensitizers of the 
present invention may be used with CF coatings containing the various 
phenolic compounds and carboxylic acid metal salts. However, the present 
desensitizers are preferably utilized with acid-reactive clay coatings and 
coatings containing metal salts of carboxylic acids. 
As previously indicated, the desensitizer compositions of the present 
invention are particularly effective with the conventional colorless 
chromogenic compounds, such as crystal violet lactone and benzoyl leuco 
methylene blue. However, it should be understood that the desensitizers of 
the present invention may be utilized to desensitize any 
electron-accepting material in a CF coating, and any of the colorless or 
substantially colorless chromogenic compounds that are utilized in 
carbonless copy paper systems, including any of the conventional leuco 
dyes and derivatives of bis(p-dialkylaminoaryl)methane, such as disclosed 
in U.S. Pat. Nos. 2,981,733 and 2,981,738, and the chromogens described in 
U.S. Pat. Nos. 3,819,396; 3,821,010; 3,875,074; and the like. 
Thus, suitable chromogenic compounds include the leuco dyes which are 
capable of reversably forming a colored, carbonium ion species such as 
those having the general formula 
##STR6## 
wherein Ar is an aromatic nucleus capable of supporting a positive charge; 
R is a group capable of stabilizing a positive charge, and X is a 
heteroatom such as oxygen or nitrogen. 
Specific examples of suitable leuco dyes include: leuco triarylmethane dyes 
such as 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal 
violet lactone), 3,3-bis(p-dimethylaminophenyl) phthalide (malachite green 
lactone), 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl) phthalide, 
3-(p-dimethylaminophenyl)-3-(2-phenylindol-3-yl) phthalide, 
3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 
3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 
3,3-bis(9-ethylcarbazol-3-yl)-5-dimethylaminophthalide, 
3-p-dimethylaminophenyl-3-(1-methylpyrrol-2-yl)-6-dimethylaminophthalide, 
7-(1-ethyl-2-methylindol-3-yl)-7-(3-ethoxydiethylaminophen-4-yl)-5, 
7-dihydrofuro [3,4-b]pyrazin-5-one, 
3-(p-dimethylaminophenyl)-3-(1-methylpyrrol-2-yl)-4,5,6,7-tetrachlorophtha 
lide, 7-(1-ethyl-2-methylindol-3-yl)-7-(3-methyldimethylaminophen-4-yl)-5, 
7-dihydrofuro [3,4-b]pyridin-7-one, 3-(4-diethylaminophenyl)-3-(1, 
2-diethylindol-3-yl) napthalide; diphenylmethane compounds such as leuco 
auramine, N-halophenyl lueco auramine, 4,4'-bis-dimethylaminobenzhydrine 
benzyl ether; xanthene compounds such as rhodamine B lactam, rhodamine 
B-(p-chloroanilino)lactam, 7-dimethylamino-2-methoxyfluoran, 2,2'-iminobis 
(6-dimethylaminofluoran), 3-diethylamino- 7-(N'-paramethoxyphenyl) 
piperazinofluoran, 2'-[N-(carbethoxymethyl)amino]-6'-diethylaminofluoran, 
6'-diethylamino-2'-[N-(N,N'-dimethylcarbamoyl) methylamino] fluoran, 
6'-diethylamino-2'-(p-nitrobenzenesulfonamino) fluoran; spiropyran and 
benzopyran compounds such as 3,3'-dichlorospiro-dinapthopyran, 
3-benzyl-spiro-dinapthopyran, 3-propyl-spiro-dibenzopyran, 
2-(2,5-dichloroanilino)-2-(p-methoxyphenyl)-2(H) benzopyran, 
5-dimethylaminospiro-[isofuran-1(3H)-2' (2H)-1-benzopyran-3-one]; acridan 
dyes such as 9-(p-dimethylaminophthalyl-3)-10-methylacridan and the like. 
The foregoing chromogenic compounds are only given for purposes of 
illustration since any chromogenic compound which is capable of reacting 
with an electron-acceptor material may be employed. 
The chromogenic compounds are isolated from the desensitized CF coating by 
microencapsulation, as previously indicated, and such microcapsules may be 
provided in any conventional manner, such as by the microencapsulation 
systems described, for example, in U.S. Pat. Nos. 3,418,656 and 3,418,250 
to A. E. Vassiliades, or U.S. Pat. No. 3,875,074 to Vassiliades et al, 
which are hereby incorporated by reference.

The following examples illustrate the effectiveness of the desensitizing 
agents of the present invention. The percentages are by weight unless 
otherwise indicated. 
EXAMPLE I 
Fifteen grams of ethylenediaminetetraacetic acid tetrasodium salt (EDTA) 
are dissolved in 85 grams of water and are coated on a CF receptor sheet 
having a coating of acidic clay. A coat weight of about 2 pounds per ream 
(3300 square feet) is employed. 
Meanwhile, a CB coated sheet of the type described in the working examples 
of U.S. Pat. No. 3,875,074 containing only encapsulated crystal violet 
lactone is placed above the CF sheet and pressure is applied over both 
untreated and treated areas of the CF sheet to produce an image. A strong 
blue image appears in the untreated area, while a weak, but still 
perceptible image appears in the area treated by EDTA, alone. 
The results of Example I indicate that EDTA is ineffective at the 
concentration employed to completely desensitize the CF receptor sheet at 
the areas applied. 
EXAMPLE II 
A CF receptor sheet of the type utilized in Example I is treated with a 5 
percent by weight solution of polyethylene glycol (commercially available 
as "Carbowax 350" from Union Carbide) at a coat weight of about 1 pound 
per ream. A CB sheet of the type employed in Example I containing only 
encapsulated crystal violet lactone chromogen is placed over the CF sheet 
and pressure is applied over both the untreated and treated areas of the 
CF layer to form a strong blue image in the untreated area. No color 
develops in the treated area. The CF sheet is exposed to air and 
fluorescent light for a week with no indication of image development in 
the treated area. 
The results of Example II indicate that the polyethylene glycol 
desensitizer is effective as a desensitizing agent in conjunction with CVL 
alone. 
EXAMPLE III 
A CF receptor sheet is treated with a 5 percent solution of triethanolamine 
at a coat weight of about 1 pound per ream. The CB sheet containing 
encapsulated CVL is placed over the CF sheet and pressure is applied over 
both the treated and untreated areas of the CF layer to form a strong blue 
image in the untreated area. A barely perceptible image appears; however, 
it is significantly weaker than that observed with the EDTA treatment. 
The results of this example indicate that triethanolamine is ineffective, 
alone, as a desensitizer for CVL. 
EXAMPLE IV 
The procedures of Examples I through III are repeated using a CB sheet 
containing only encapsulated benzoyl leuco methylene blue (BLMB). As BLMB 
developes color very slowly, no strong image appears, initially, employing 
either the EDTA, the polyethylene glycol or the triethanolamine. However, 
after several hours a strong blue-green image appears in all of the 
untreated areas, while an attenuated, but still clearly visible image 
appears in the treated areas including those areas treated with EDTA. 
This example indicates that neither EDTA, PEG nor triethanolamine, alone, 
are effective as desensitizers for BLMB. 
EXAMPLE V 
A solution containing 10 grams of EDTA tetrasodium salt, 10 grams of 
polyethylene glycol and 80 grams of water is coated on a CF receptor sheet 
of the type described in Example I at a coat weight of about 2 pounds per 
ream. 
Next, a combination of 2.1 parts CVL and 1.8 parts BLMB are applied to the 
treated and untreated areas of the CF sheet using pressure on a 
superimposed CB sheet containing the CVL and BLMB in microcapsules. A 
strong CVL image immediately appears on the untreated image, while a BLMB 
image appears after a longer development time. However, no image developes 
from either the CVL or the BLMB in the treated areas, even after exposure 
to air and fluorescent light for a week. 
This example demonstrates the synergistic combination resulting from the 
use of EDTA tetrasodium salt in combination with polyethylene glycol, 
since the combination was able to desensitize the acidic clay with respect 
to both CVL, and BLMB, whereas neither desensitizing component, alone, was 
capable of doing so. 
Although the invention has been described in considerable detail with 
particular reference to certain preferred embodiments thereof, variations 
and modifications can be effected within the spirit and scope of the 
invention as described hereinbefore, and as defined in the appended 
claims.