Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~3-21-4569A CN :
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~MPROVE~lENTS RELATING TO P~ESSURE SENSITIVE
~`~RK-RECORDING SYSTEMS
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.This invention relates to solutions ~hich are ...
use~ul in the ~roduction of pressuxe-sen~i.t:ive ma~k-
recording systems and to systems thlls producedO
The most familiar form o~ pressl~e-sensitive mark-
recording system is the so-called carbonle~Qs copyi~g
: paper which comprises a t~vo-.sheet ~7stem i~ vhich the
. under sur8lace of the top sheet has a coati3-~g o~ micro~
capsules of a solution o~ a colourless chromosen3 while
the upper surlace o~ ;he lower (receiver) sheet has an
10 absorbent coating includin~5 a sensitizin~ agent for the .
chromogen. When a markinD instru~ent is applied to the
.
: top sheet, the microcapsules are locally ruptured,
. . thereby releasing the chromogen solution f3~0m the
affected microcapsules to react with the underlying
sensitizing a~ent a~d orm coloured marks on the receiver ..
sheet corresponding to the marks applied to the top
sheet~ .
A successful carbonless copying paper s~rstem n.eeds
to meet a number of criteria For examplè, the marks
on the receiver sheet should develop rapidly to a
legible intensity of colour, and a le~ible mark should :.
persis-t for as long as the sheet is required -to ~e kept~
~hether the various criteria are met depends on a number
of factors including tlle nature of the solvent, the
sensitizing agent and the chromogen, and many different
materials of each category have been proposed.
i~l3~S~
We have now found that improvements are achieved in
respect of the initial intensity of colour of the mark and
-its durability by including in the system certain phenolic
compounds.
A solution of the invention comprises a liquid solvent
comprising an aromatic hydxocarbon in which at least half the
carbon atoms are benzenoid carbon atoms, and, aissolved in
the solvent, a chromogen and a compound (hereinafter referred
to as.a promoter) which is an alkylated, aralkylated or
10 cycloalkylated phenol or which contains an alkylated,
aralkylated or cycloalkylated hydroxyphenyl radical in its
molecule, the structure of the phenol or radical being such
that at least one of the positions ortho to the hydroxyl
group is occupied by an alkyl group of at least four carbon
15 atoms or by an aralk~l or cycloalkyl group, and the solvent
having a low volatility consistent with its use as a chromogen
solvent in a system of the invention.
A pressure-sensitive mark-recording system of the
invention comprises ~a) sheet material, (b) promoted mark-
20 forming components supported by the sheet material and
- arranged in j-uxtaposition but in unreactive condition, the
said components comprising (i) a-chromogen (ii) a sensitizing
agent fo~ the ch~omogen which produces a colour from the
chromogen when brought into contact with the chromogen in the
25 presence of a sol~ent and (iii) a promoter as deEined above,
and (c) the said soivent, which is a ]i~uid comprising an
aromatic hydrocarbon in which at least half the carbon atoms
are benzenoid carbon atoms, and in which solvent both the
chromogen and the promoter are soluble, supported by the
30 sheet material but separated from the sensitizing agent by
a physical barrier which is rupturable on the application
: of a marking instrumentto the sheet material.
; The chromogens, sensitizing agents and the aromatic
hydrocarbons useful in the p~esent invention are,in general,
: 35 materials conventionally employed in the art, and are more
fully described below.
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In the promoter, the or each phenol nucleus may contain ...
from one to three-alkyl, aralkyl or cycloalkyl (including -
alkylcycloalkyl) groups, and pre~erably contains two or ...
three such yroups, each of such groups preferably having ...
5 up to 12 carbon atoms, with the proviso indicated above ..
regarding occupancy of. at least one o~ the positions ortho .
to the hydroxy group. An alkyl group occupying such a ..
position is preferably an alkyl group of ~rom 4 to 12 ..
carbon atoms, especially a tertiary alkyl group, ~or ..
10 example a t-butyl, t-amyl, 1,1,3,3-tetramethylbutyl or ..
1,1,3-trimethylhexyl group. Alkyl substituents in other ....
positions can have straight or branched chains, and usually
contain from 1 to 12 carbon atoms,examples being methyl, . .
ethyl, isopropyl, n-hexyl, 2-ethy].hexyl, nonyl, decyl, and
15 the tertiary alkyl groups named above. An alkyl group in ..
such other position is often preferably an alkyl group
containing from one to three carbon atoms, e.g. methyl, .
ethyl, or isopropyl, for example where the alkyl group ...
_ concerned is a third alkyl group in a di-tertiary alkyl ..
20 phenol, in a diaralkylated phenol or in a dicycloalkyl
phenol, or where the alkyl group is presen- in an ortho-
tertiary alkyIated, aralkylated or cycloalkylated hydroxy- .
phenyl nucleus that is linked to other atoms in the molecule .
of ~.he promoter. :.:
An aralkyl substituent in a promoter molecule is ..
preferably a benzyl, alpha-methylbenzyl or alpha, alpha-
dimethylbenzyl group. The last two are especially preferred
where the substituent occupies a position ortho to a
hydroxyl group. A cycloalkyl group occupying such a .-.
30 position is preferably an alpha-alkyl cycloalkyl group, ......
for example an alpha-methylcyclohexyl or alpha-ethylcyclo- .
hexyl group. .
....
,.....
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Pre~erred promoters are mononuclear phenols,
substituted in the manner definedi compounds containing
two hydroxyphenyl radicals, each substituted in the manner
defined, and linked, preferably ~t the 2- or.4- positions,
5 through a sulphur atom or through an alkylene or alkylidene
group, usually a Cl_4 alkylene o:r alkylidene group; and
compounds having the general formula
~ A-(CH2)pC0~ mR
where A represents a hydroxyphenyl radica~ substituted in the
10 manner defined, preferably linked at-the 2- or 4-position to
the (CH2)p radical, p is an integer of ~rom 1 to 4, m.is an
integer of from l to 4 and R represents a radical derived by
the loss of m hydrogen atoms from an alkane o~ the formula
C H2n + 2 where n is an integer o~ from 1 to 24, preferably
15 of from m to 24.
Specific examples of promote^s that are alkylated,
aralkylated or cycloalkylated mono-nuclear phenols are ortho
(alpha-methylbenzyl)phenol, 2,4-di(alpha-methylbenzyl)phenol,
2,6-di(alpha-methylbenzylphenol) and 2,4,6-tri(alpha-
20 methylbenzyl)phenol and mixtures of these mono, di and
tri(alpha-methylbenzYlated)phenols~ 2(alpha-methylbenzyl)-4-
methylphenol, 2,6-di-t-butyl-4-methylphenol, 2,5-di-t-amyl-
hydro~uinone, 4,6-di-nonyl-2-methylphenol, 2,4-dimethyl-6
(~-melhylcyclohexyl)phenol and 2~6-di(d-methylcyclohexyl)-4
25 methylphenol.
Examples o~ promoters containing two hydroxyphenyl
radicals substituted and linked in the manner defined above
are 4,4'-thiobis(2-t-~utyl-5-methylphenol), 4,4'-butylidene-
bis(2-t-butyl-5-methylphenol), 2,2'-methylenebis(4-methyl-
30.6-t-butylphenol), 2,2'-methylenebis(4-ethyl`6-t-butylphenol)~
and bisr2-hydroxy-3(~-methylcyclohexyl)-5-methylphenyl~
methane.
Examples of compounds having the general formula
[A-(CH2)pCOO] mR
35 are octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate
and tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl-
oxymethyl~methane.
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Such promoters are co~ercially available materials.
The amount of the promoter used in a solution o the
_invention can be, for example, from 0.05 to 10% by weight
of the solvent, but i9 preferably from 0.1 to 3%. The :
5 optimum will vary with the particular solvent and promoter
used, but is often in the range 0.5 to 2æ by weight of the
solvent.
In addition to improving the initial intensity and
durability of the mark, the presence of the promoter has
10 been found to increase the solubility of the chromogen in
the solvent. This effect could be used to increase the
concentration o the chromogen in the solvent and thus
obtain darker marks, but is mainly of interest in that it
helps to avoid precipitation of the chromogen when the
15 latter is used at conventional concentrations and the - -
solution or system is stored at low temperatures.
The aromatic hydrocarbons suitable for use in the
present invention can be single compounds, but are often
mixtures of individual compounds, the aromatic hydrocarbon
20 being such that at least half the carbon atoms in the
_ compound or mixture ar2 benzenoid carbon atoms. Aromatic
hydrocarbons which can be used as, or as components of, -
the solvent in this invention include partially hydrogenatea
terphenyls, for example hexahydroterphenyls and dodeca-
hydroterphenyls. As normally produced, materials of this
type are mixtures containing in various proportions, ~ully
hydrogenated terphenyls, partially hydrogenated terphenyls,
and terphenyl itself. The terphenyl which is partially
hydrogenated in obtaining such mixtures is itsel~ a mixture -
30 of isomers. Other hydrocarbons include benzylated and a]pha-
methylbenzylated alkylbenzene~, e-g- mono- and dibenzyl ethyl-
benzene and mono(alpha-methylbenzyl)toluene, alkylnaphthalenes,
e.g. dipropylnaphthalene and mono-alpha or -beta~2-hexyl)
naphthalene, alkylbiphenyls, e.g. mono- and diisopropyl-
35 biphenyls.
The solvent can be an aromatic hydrocarbon ~providedthe hydrocarbon is a liquid at room temperature) or a
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mixture of aromatic hydrocarbons, or an aromatic hydrocarbon
or mixture together with a diluent, a diluent being an inert
liquid miscible with the aromatic hydrocarbon(s). Examples
of suitable diluents include mineral and vegetable oils,
5 such as kerosene, paraf~in oil, castor oil, soybean oil,
corn oil and (long-chain alkylated)benzenes, for example
(C7-C16 alkylated)benzenes. The d:iluent in a solvent o~
the invention unctions to alter physical properties of
the solvent, for instance viscosity or vapour pressure, where
10 such alteration may be desired for optimum handling or
processing. The solvent preferably con~ains at least 50%
by weight of aromatic hydrocarbon but in some instances, the
aromatic hydrocarbon may be dilute~ with up to, for example,
3 times its own weight of diluent. For rapid development of
15 print intensi-ty, the solvent is preferably one having a
viscosity in the range 5 to 15 centiso~es at 38C.
The chromogen used in the presentinvention is usually
an aromatic compound containing a double bond system which
is converted to a more highly polarized conjugated and
20 coloured form when reacted with an acidic sensitizing
material. A-particularly preLerred class o~ chromogens
includes compounds of the phthalide type, for instance
crystal violet lactone which is 3,3-bis(p-dimethylamino-
phenyi)-6-dimethylaminonaphthalide, and malachite green
25 lactone which is 3~3-bistp-dimethylaminophenyl)phthalide~
Other phthalide-derived chromogens include 3,3-bis(p-
dipropylaminophenyl)phthalide, 3,3-bis(p-methylaminophenyl)
phthalide, 3-(substituted-phenyl)-3-(indole-3-yl)-phthalides
such as 3-(p-dimethylaminopheryl)-3-(1,~-dimethylindol-3-
30 yl)phthalide, 3,3-bis(methylindol-3-yl)-phthalides such
as 3,3-bis(1,2-dimethylindol-3-yl)phthalide, 3-(phenyl)-
3-(heterocyclic-substituted)
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11 13~ 0
phthalides such as 3-(p-dimethylaminophenyl)-3-(1-methyl
-pyrr-2-yl) 6-dimethylaminophthalide, indole and
carbazole-substituted phthalides such as 3,3-bis(1,2- ..
- dimethylindol-3-yl)-5-dimethylaminophthalide and 3,3-bis
(9-ethylcarbazol-3-yl)-5-dimethylaminophthalide7 and
substituted indole phthalides such as 3-(1,3-dimethyl~
indol-3-yl)-3-(2-meth~rlindol-3-yl)-phthalide~
Other chromogens which can be u~ed in the present
invention include 3-dialkylamino-6-alkyl-7-alkylaminO-
10 fluorans, 3-dialkylamino-7-dia~.]-.ylan~i.nofluorans and- ..
3-methyl-2,2'-spirobi(benzo/f7chromene)
An auxiliary colouring agent can be employed ~Yith
the above chromogens. For e~arnpleycr~stal violet lactone
(CVL) is usually used in conjunction \Yith be~oyl leuco -
methylene blue (BLh~). The colouring agent compleme~ts
the chromogen bacause on contact wi1h the sensiti2ing
agent the CVL produces an i~edi.ate dark blue
colouration~ but the colour tellds to fade over a period .-
of timeO The BL.~.IB when in contact ~vith the sensitizing ;:
agent produces a somewhat pale initial colour, but the
colbur gradually intensifies by oxidation of the dye~ :.
--The sensitizing agent used in a system o~ the
present invention can be~ for e~ample; an acid clay, for
instance an attapulgite or bentonite clay, or an acidic ..
organic polymer, for example a phenol-aldehyde polymer
or a partially or wholly h~drolysed styrene/maleic .:
anhydride or eihylene/maleic anhydride polymer.
Part-cularly good results are obtained in the present
invention using an acid clay as the sensitizing agentO
A system of the present invention can be prepared
according to well Xnown conventional procedures t~hich
are adequately described in the literature~
~lthough a preferred e~.bodiment of this invention
comprises a two-sheet system tvherein the sensiti~in~ agen-t
is carried by one sheet and a m~rl;ing fluid comprising
a solu-tion of the invention is carried by a second sheet,
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the invention is not limited to such systems aloneD
The only essential requirement is that the chromogen
and the-sensitizing agent be maintained in a separate
or unreactive.condition until pressure is applied to the
system, and that upon the a~plication of pressure the
chromogen and the sensitizlng age~t are brought into
reactive con-tact in the presence of the solvent and o~
the promoter. Thus it is possible to have the chromo~en
and sensitizin~ agent present in a dry and unreactive
10 state on a common c~rrier and to have a solution of the
promoter in the solvent.carried on a separate shee~
whereupon the application o pressure would release
the solution into the chro~ogen/sensitizing agent mixture
and promote localized reaction and colour development
Obviously, many other arrangements, configurætions and
relationships OI the solven+ and the promoted mar~
forming materials ~vith respPct to their encapsulation
and location on the supportin~ sheet or webs can be
envisaged, and such arran~e~ents are within. the scope
of the present invention. For example, it is possible
to coat a sinDle paper or supportmember with all the
components of this system to form a single sel-E-
contained unit ~hich can be marked by th~ move~ent o
a stylus or other pressure-imparting me~ns upon the
~5 sur~ace of the paperO Such papers are particularly
useful for use in inkless recording instrumentsO
Solutions of Lhe invention were evaluated by the
following technlque :
A soluLion of a blend of equal parts by we-ght o~
CVL and BL~B in the solvenL ~Yas preparedO ~ por-tion
of this solution was used ~s the control, and in other
portions there ~Yere dissolved the promoters to be
evaluatedO To estimate pri~t intensity, a plate eng~raved
with a p~ttern of dots ~as coated with sufficiellt OI the
solution to gi~e a co~ting lS microns in thickness,
usinC~ a doctor ~lade. A carriage-supported roller
~ ~3q561~ , ~
having a paper sheet coated ~Yith an acid clay sensitizing .. :
agent wrapped round the roller ~vas then moved slowly ....
across the solution-coated plate under constant pressure.
Colour developed on the paper. The paper was removed
5 from the roller, and the intensity o~ colour was measured
using a Macbeth RD 51~ reflectometer calibra-ted against
a "perfect white" of 0.07 units of optical density and ...
a "perfect black" of 1-78 units of optical density, using ..
standard "perfect ~vhite" and "perfect hlack" plates
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10 supplied by the manufacturer. A.fter the i.nitial rea~ing, ..
the paper was transPerred to a humidi~ied oven, and.was
removed at intervals for further colour ~ntensity ~ .
measurements. . .
To obt~in the results shown in the Tahles below5 the ..
15 colour intensity ~Yas measured each time at 20 diIferent .:
points on the paper surface and the ~alues were averagedo
The figures in the column headed "Standardized" are values
of the average colour irltensity on .a scale on which the
a~erage i~litial colou.~ inten~ity o~ the control is 100.
20 The results glven.in Table 1 were obtained usin~ a ..
. solution containing 2.94% by weight of the blend o~ CVL
and BLMB alld l.9~o hy wei~]lt of the promoter in a solvent
-- consisting of a mix~ure of 7 parts by ~Yeight o~ h~drogena-ted
terphenyls obtained by ~he hydrogenation of terphenyl with
25 approxima-tely 4~,~0 of the amount o~ hydrogen required for .-.
complete hydrogenation, and 3 parts by ~eight of a
(C9-Cll al~yl)benzeneD The oven was held at 75C~ and 60~o
relative hum dity. The promoters used ~Yere as follows:
Mixture ol mono- and di(~-meth~lbenz~lated)phenol ..
30 ~ - 4,6-di~onyl-2-~ethylphenol
C - Tetrakis~3-(3,5-di-t-butyl-4-hydroxypllen.yl)
propionyl)oxymethy~methane ....
D - Octadecyl 3-(3,~-di-t-butyl-4-hydroxyphenyl) ...
propionate .
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-- 10~ ,. ......
_ Table 1
I~ltial Intensity Intensity after 4S hours
in oven
Promo~er . _
Direct Standardized Direct Standardized
. ...... _ ':,'.
A 0.63 1120 5 0054 96~4 :.. '
B 0.67 119~6 0.53 94L 6
C 0.60 107.1 0.54 96.4
D 0.64 114 D 2 0 53* 94 r 6* ..
None 0.56 100.0 0.44 ----.-- T - '''
After 20 hours in oven
The results given in Table ~I were obtained using
a solution containin~ 2.97qo by weight of the blend of
CVL and BL~IB and 0.96% by weight of the promo-ter i~ a
solvent consistin~ o~ a mi~ture of 7 parts by weight
of hydrogenated terphenyls obtained by the
hydrogenation of terphenyl with approximately 40% of
the amount OI hydrogen required for complete
hydrogenation, and 3 parts by ~eight of kero~ene~ The
oven W2S held at 70 C. and 50~c relative hu~idity~ -
- Table II
Initial Intensi y ~Intensity after 96 hours
- I - i~ oven
Promoter ~
Direct ~Standaràized Direct Standardized
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B j 0064 11004 0~36 62 D
C ~ 0 D 63 10806 0031 5304
None ~ 0058 100 0024 41~4
The improvements obtained in the presence of the
- promoter, both in respect of initial colour intensity
and persistence o~ colour durin~ accelerated storage,
are apparent from the above resultsD
The efIects of varying the proportions of CVL and
BL~IB in the blend in the presence and absence of
promoter were investi~ated, with the results 5ho~Yn in
Table III. The solvent was the same mixture as that
35 used to ob~ain the results of Table II, and the oven
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was maint~ined at 75 C. and 60% relative humidity.
Table ~II
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Percent by weight in solution
;CVL 1.5 1051~5 1~5 1~0 l~0
B~ 1.5 1~5l~0 0~5 1~0 1~0 ,
Promoter B 01.0 1~0 l~,0 0 l~0
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Time (Hours) D rect I~ tensit~
~ ~ -. --------I ' '''
0 0,61 0.65 0066 0~7~0.61 0.64 :
23 0.50 0~53 0059 0~56~Sl 0057 .
00~8 O.SS 0.53 0O5~ _ 0.47 .
47 0.50 0.5~ 0O55 0~5500~4 0~51 :
54 0047 0~54 0.~5 0,580~43 0.55 .
126 ~5 0051 00~9 00520~41 0,51 .
156 0.4~ 0054 0050 0.5~ _ OOS0
These results demonstrate the improvement o~tainable
-- by the addition of the promoter, and tha~ when using a :
solution containing a promoter, the amounts of chromogen
and auxiliary colouring a~ent can be reduced ~Yhile
maintaining good print-intensity and dura~ilit~, :
The cor.cen~ra~ion of the chromogen in a solution o*
the invention is usually 0075 - 2% by weight of the
solu-tion. Where both a ohromogen and an auxiliary
colo~lring agent are used, their proportions by weight
may be, for example, from 40:60 to 80:20~ and are
25 pre~erably uithin the range 50:50 -to 75:25.
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