Note: Descriptions are shown in the official language in which they were submitted.
1213~
This invention relates ~o a thermoresponsive recording paper sheet.
More particularly, the invention relates to a thermoresponsive recording
paper sheet with improved responsiveness in color production, weather-proofness
and preservability.
It has long been known that colorless or pale-colored chromogenic
substances, such as crystal violet lactone, and phenolic compounds can react
to produce a color, and the use of such reaction in thermoresponsive paper
sheet recording is disclosed in U. S. Patent No. 3,539,375, for instance.
~owever, to meet the demands for higher thermal sensitivity and high-
speed responsiveness, for instance, arising from recent advances in recording
devices and diversified use of thermoresponsive recording sheets, it is still
necessary to solve various problems. For instance, for use on thermal printers
or thermal facsimile telegraphs, thermoresponsive paper sheets should have
improved thermal responsiveness in color production, since an insufficient
degree of responsiveness would result in increased electric power consumption
and/or decreased printing velocity. For increasing color-producing responsive-
ness of thermoresponsive sheets, there has already been proposed the use of
such additives as waxes (Japanese Patent Application laid open (Kokai) under
No. 19,231/1973) and nitrogen-containing compounds (Japanese Kokai 34,842/
1974).
In thermoresponsive recording sheets, presumably a chromogenic
substance and a phenolic compound are present each in the stable and finely
divided state dispersedly in the same layer or in different layers and,
when heated, at least one of the two components melts or sublimates or both
give an eutectic mixture, whereby they come into intimate contact with each
other to produce a color. Therefore, it is necessary that each reactive
color-developing component sould be colorless or pale-colored crystals or
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solid at normal temperature, and further it is preferable that said component
should melt at 70C or over and completely liquefy and/or vaporize at 150 to
200C.
U. S. Pa~ent No. 3,539,375 descri~es as a phenolic compound adequate
for such purpose 4,4'-isopropylidenediphenol, which is used today in many
cases.
As a result of intensive research for a thermoresponsi~e recording
paper sheet with improved responsiveness in color production, weather-
proofness and preservability, the present inventors have accomplished this
invention. Thus, the invention relates to a thermoresponsive recording
paper sheet comprising a compound of the formula
Rl_o ~ S2 ~ o R2 (I)
wherein Rl is hydrogen, alkyl of 1 to 5 carbon atoms, benzyl or phenethyl,
and R2 is alkyl of 1 to 5 carbon atoms, benzyl or phenethyl, b~t R2 does
not represent methyl when Rl is hydrogen.
In an aspect, this invention provides a thermoresponsive recording
paper sheet compricing a normally colorless or pale-colored chromogenic
~ substance and a phenolic compound of the formula:
H0 ~ S02 ~ o_R3 (I-a)
wherein R is alkyl of 2 to 5 carbon atoms, benzyl or phenethyl.
The compound of formula (I-a) wherein R is methyl is hardly crystal-
lizable, and so it is unsuited for use in practicing the invention.
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t
In another aspect, the invention provides a thermoresponsive recordin~
paper sheet comprising a normally colorless or pale-colored chromogenic
substance in combination with a phenolic compound, which comprises a compound
of the formula:
R4-o ~ S02 ~ o-R4 (I-b)
wherein R4 is alkyl of 1 to 5 carbon atoms, benzyl or phenethyl.
The compound of formula (~-a) includes, for instance, 4-ethoxy-4'-
hydroxydiphenyl sulfone, 4-propoxy-4'-hydroxydiphenyl sulfone, 4-isopropoxy-
4'-hydroxydiphenyl sulfone, 4-butoxy-4'-hydroxydiphenyl sulfone, 4-isobutoxy-
4'-hydroxydiphenyl sulfone, 4-tert-butoxy-4'-hydroxydiphenyl sulfone,
4-amyloxy-4'-hydroxydiphenyl sulfone, 4-isoamyloxy-4'-hydroxydiphenyl sulfone,
4-tert-a~yloxy-4'-hydroxydiphenyl sulfone, 4-benzyloxy-4'-hydroxydiphenyl
sulfone and 4-phenethyloxy-4'-hydroxydiphenyl sulfone.
The compound of formula (I-b) includes, for examplP, 4,4'-dimethoxy-
diphenyl sulfone, 4,4'-diethoxydiphenyl sulfone, 4,4'-dipropoxydiphenyl
sulfone, 4,4'-dibutoxydiphenyl sulfone, 4,4'-diisobutoxydiphenyl sulfone,
4,4'-di-tert-butyldiphenyl sulfone, 4,4'-diamyloxydipheny] sulfone, 4,4'-
diisoamyloxydiphenyl sulfone, 4,4'-di-tert-amyloxydiphenyl sulfone, 4,4'-
dibenzyloxydiphenyl sulfone and 4,4'-diphenethyloxydiphenyl sulfone.
The 'chromogenic substance~ as used herein means a compound capable
of producing a color upon reaction with a phenolic compound and includes,
among others, crystal violet lactone, malachite green lactone, 3,3-bis-
~p-dimethylaminophenyl)-4,5,6,7-tetrachIorophthalide, benzo-~ -naphtho-
spiropyran, 3-methyl-di-~ -naphthospiropyran, 1,3,3-trimethyl-6'-chloro-
8'-methoxyindolinobenzospiropyran, N-phenylrhodamine lactam, 3-ethylamino-
6-chlorofluoran, 3-morpholino-5,6-benzofluoran, 3-die~hylamino-6-methyl-
:~Zl~
7-anilinofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-
6,7-dimethylfluoran, 3-dimethylamino-7,8-benzofluoran, 3-diethylamino-6-
methoxyfluoran, 3-die~hylamino-7-dibenzylamino~luoran, 3-diethylamino-7-
anilinofluoran, 3-diethylamino-5,6-benzo-7-benzylaminofluoran, 3-piperidino-
6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methy-7-anilinofluoran, 3-~-
ethyl-tolylamino-6-methyl-7-anilinofluoran and 3-diethylamino-7~ 3-
trifluoromethylphenyl)aminofluoran, but is not limited to these.
The compounds of formula (I-a) can be used in combination with another
phenolic compound which melts generally at 70C or above and thereby reacts
with the above~mentioned chromogenic substance to produce a color and
includes, but is not limited to, 4-phenylphenol, 4-methyl-2,6-di-ter~-butyl-
phenol, 4,4'-dihydroxydiphenyl, 4,4'-isopropylidenediphenol, 4,4'-isopropylidene-
bis(2-chlorophenol), 4,4'-isopropylidenebis(2-methylphenol), 4,4'-isopropylidene-
bis(2-tert-butylphenol), 4,4'-isopropylidenebis(2,6-dimethylphenol~, 4,4'-
~5 sec-butylidenediphenol, 4,4'-cyclohexylidenediphenol, 4,4'-cyclohex~lidene-
bis(2-methylphenol), 4,4'-cyclohexylidenebis(2-isopropylphenol), 2,2'-
methylenebis(4-chlorophenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol),
2,2-bis(4-hydroxyphenyl)hexane, 2,2-bis(4-hydroxyphenyl)heptane, 2,2-bis-
(4-hydroxyphenyl)octane, 4,4'-thiodiphenol, 4,4'-thiobis(3-methyl-6-tert-
butylphenol), methyl p-hydroxybenæoate, ethyl p~hydroxybenzoate, benzyl
p-hydroxybenzoate, tolylmethyl p-hydroxybenzoate; phenethyl p-hydroxybenzoate,
3-phenylpropyl p-hydroxybenzoate, phenyl p-hydroxybenzoate, 4--nydroxyaceto-
phenone, 4-hydroxybenzophenone, salicylanilide, novolak type phenolic resin,
halogenated novolak type phenolic resin, d-naphthol and ~-naphthol.
-25 In a thermoresponsive recording paper sheet comp~ising the compound
of formula (I-b) as an agent for increasing responsiveness in color production,
weather-proofness and preservability, the 'phenolic compound' as used herein
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means the compound of formula (I-a) and/or ~he above-mentioned another
phenolic compound. The compound of formula (I-b) is used, for example,
in an amount of 0.01 to 1 part by weight per part by weight of such phenolic
compound.
The thermoresponsive recording paper sheet in accordance with the
present invention can be prepared by a conventional method, for instance,
(1) by c = inuting the chromogenic substance and the phenolic compound
separately, if necessary tDgether with a surfactant, binder and/or dispersing
agent, in water or in an organic solvent, or (2) by comminuting the
chromogenic substance, the phenolic compound and the compound of formula
(I-b) each separately, or the chromogenic substance and the phenolic compound
separately with the compound of formula (I-b) combined with the chromogenic
substance and/or the phenolic compound~ if necessary together with a surfactant,binder and/or dispersing agent, in water or in an organic solvent, in a crusher
such as ball mill or sand grinder and coating a paper sheet with the resulting
dispersions, followed by heat drying.
Some of compounds of formula (I) are described in Beilsteins ~andbuch,
and the compounds ~f formula (I) can be produced by alkylation of 4,4'-
bisphenol sulfone.
Typical examples of the compound of formula (I~ are:
(1) 4-Ethoxy-4'-hydroxydiphenyl sulfone, m.p. 163-164C
(2) 4-Propoxy-4'-hydroxydiphenyl sulone, m.p. 138-140.5C
(3) 4-Butoxy-4'-hydroxydiphenyl sulfone, m.p. 118-119C
~4) 4-Benzyloxy-4'-hydroxydiphenyl sulfone, m.p. 162-164C
(5~ 4-Phenethyloxy-4'-hydroxydiphenyl sulfone, m.p. 143-144C
(6) 4,4'-Dimethoxydiphenyl sulfone, m.p. 129-130C
(7) 4,4'-Diethoxydiphenyl sulfone, m.p. 164C
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~8) 4,4'-Dipropoxydiphenyl sulfone, m.p. 142-143C
(9~ 4,4'-Diisopropoxydiphenyl sulfone, m.p. 157C
(10) 4,4'-Dibutoxydiphenyl sulfone, m.p. 92.5C
(11) 4,4'-Diamyloxydiphenyl sulfone, m.p. 86.5C
(12) 4,4'-Diisoamyloxydiphenyl sulfone, m.p. 98C
(13) 4,4'-Dibenzyloxydiphenyl sulfone, m.p. 188-189C and
(14) 4,4'-Diphenethyloxydiphenyl sulfone, m.p. 136-138C
Preparative Example 1
A mixture of 5 g of 4,4'-bisphenol sulfone, 40 ml of dimethyl sulfoxide,
1 g of sodium hydroxide and 2.7 g of propyl bromide is stirred at room
temperature for 5 hours. The reaction mixture is then made acidic with
hydrochloric acid and extracted with ethyl acetate. The extract is washed
with aqueous hydrochloric acid and adjusted to pH 10 with aqueous sodium
hydroxide to remove the unreacted starting materials which pass over into
the aqueous layer. The organic layer i5 washed with aqueous hydrochloric
acid and concentrated. The residue is crystallized from toluene to give
4-propoxy-4'-hydroxydiphenyl sulfone, melting at 138-140.5C.
Preparative Example 2
A mixture of 5 g of 4,4'-bisphenol sulfone, 40 ml of methyl cellosolve,
1 g of sodium hydroxide and 4.1 g of phenethyl bromide is stirred at 90C
for 5 hours. The reaction mixture is concentrated, and to the residue is
ad~ed aqueous sodium hydroxide until the pH of the aqueous layer reachs
p~ 10. The aqueous layer is extracted with ethyl acetate, and the extract
is washed with aqueous hydrochloric acid and concentrated. The residue is
crystallized from toluene to give 4-phenethyloxy-4'~hydroxydiphenyl sulfone,
melting at 143-144C.
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Brief Explanation of the Drawing
Fig. 1 shows the temperature-dependency of the optical density as
measured with a photoelectric densitometer. In Fig. 1, curve (1) is for
the thermoresponsive recording paper sheet of Comparative Example 1, curve
(2) for that of Exa~ple 6, curve (3) for that of Example 7, and curve (4)
for that of Example 8.
The present invention will be better unders~ood from the following
examples, but they are not to be construed as limiting the present invention.
'Part(s)' means 'part(s) by weight'.
Comparative ~xample 1
Dispersion Al
Crystal violet lactone 1 part
5% Polyvinyl alcohol solution 5 parts
Water 40 parts
Dispersion B:
4,4'-Isopropylidenediphenol 5 parts
5Z Polyvinyl alcohol solution 25 parts
Water 20 parts
Comparative Rxample 2
Dispersion A:
Same as Dispersion A in Comparative Example 1 46 parts
Dispersion B:
4,4'-Butylidenebis(6-tert-butyl-m-cresol) 5 parts
5% Polyvinyl alcohol solution 25 parts
Water 20 parts
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g
Ex~pLe 1
~ispersion A: .
Same as Dispersion A in Comparative Example 1 46 parts
Dispersion B:
4-Propoxy-4'-hydroxydiphenyl sulfone5 parts
5% Polyvinyl alcohol solution 25 parts
Water 20 parts
Example Z
Dispersion A:
Same as Dispersion A in Comparative Example 1 46 parts
Dispersion B:
4-Ethoxy-4'-hydroxydiphenyl sulfone5 parts
5% Pol~vinyl alcohol solution 25 parts
Water 20 parts
Example 3
Dispersion A:
Same as Dispersion A in Comparative Example 1 46 parts
Dispersion B:
4-Butoxy-4'-hydroxydiphenyl sulfone5 parts
5% Polyvinyl alcohol solution 25 parts
Water 20 parts
Example 4
Dispersion A:
Same as Dispersion A in Comparative Example 1 46 parts
Dispersion B: .
4-Benzyloxy-4'-hydroxydiphenyl sulfone5 parts
5% Polyvinyl alcohol solution 25 parts
Water 20 parts
12~31~0
-- 10 --
Exam~le 5
Dispersion A:
Same as Dispersion A in Comparative Example 1 46 parts
Dispersion B:
4-Phenethyloxy-4'-hydroxydiphenyl sulfone5 parts
5% Polyvinyl alcohol solution 25 parts
Water 20 parts
Example 6
Dispersion A:
Same as Dispersion A in Comparative Example 1 46 parts
Dispersion B:
4,4'-Isopropylidenediphenol .4 parts
4,4'-Butoxydiphenyl sulfone 1 part
5% Polyvinyl alcohol solution 25 parts
Water 20 parts
Example 7
Dispersion A:
Same as Dispersion A in Comparative Example 1 46 parts
Dispersion B~
4-Propoxy~4' hydroxydiphenyl sulfone 4.75 parts
4,4'-Diamyloxydiphenyl sulfone 0.25 part
5% Polyvinyl alcohol solution 25 parts
Water 20 parts
Example 8
Dispersion A:
Same as Dispersion A in Comparative Example 1 46 parts
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Dispersion B:
4-Butoxy 4'-hydroxydiphenyl sulfone 4 parts
4,4'-Dibutoxydiphenyl sulfone 1 part
5% Polyvinyl alcohol solution 25 parts
Water 20 parts
In each of ~he above examples, Dispersions A and B were prepared
separately (i.e. without mixing Dispersion A with Dispersio~ B) hy diSperS-
ing the solid component by grinding in a ball mill for 2 days and then
combined to give a coating composition for making a thermoresponsive
recording paper sheet. A sheet of fine quality paper having the basis
weight of 50 g/m2 was coated on one side with the coating composition to
the coat amount Of 4 g/m2 (on the dried basis) and dried at 50C in a drier.
The thermoresponsive paper sheet thus obtained was caused to produce a color
by pressing the sheet against a plate heated at 80-150C under the pressure
of 1.5 kg/cm2 (gauge) for 5 seconds.
The thermores?onsive recording paper sheets o f Ex~mples 1 to 5 and
Comparative Examples 1 and 2 were tested for the responsiveness and the
preservability of recorded images. The results are shown in Table 1~
The thermoresponsive recording paper sheets of Examples 6 to 8 and Compara-
tive Example 1 were measured for the intensity of color using a photoelectric
densitometer. The results are shown in Fig, 1.
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Table 1
_
Responsiveness Discoloration of -
in Recording Recorded Images *
Example 1 ++
Example 2 + . _
Example 3 ++
Example 4 .
Example 5 ++ . ~+
Comparative . . . .
Example 1 + +
Comparative _
* After storing at normal temperature for 24 hours
Responsiveness:
~+ : Excellent
+ : Fair
- : Poor
Discoloration of Recorded Images:
++ : No discoloration
+ : Moderate discoloration
- : The image al st disappeared.
Examele 9
In dispersions B in Example 6 and Example 8, the proportion of
4,4'-dibutoxydiphenyl sulfone to the phenolic compound was varied as
specified below in Table 2 while the total amount of the two components
was retained, and thermoresponsive recording paper sheets were prepared
in the same manner as mentioned above.
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Table 2
~ ... .. ~
Thermoresponsive Sheet No.
Compound 1 2 4 5 ~ 8 - _ _
Compound A 2 2 2 1 1 1 0.5 0.5 0.5 O
. _ _
Phenol I 3 _ 4 _ _ 4.5 _ _ 5
Phenol II 3 4 4.5
_~ _._ . _
Phenol III _ 3 4 4.5
Compound A: 4,4'-Dibutoxydiphenyl sulfone
Phenol I : 4,4'-Isopropylidenediphenol
Phenol II : Benzyl p-hydroxybenzoate
Phenol III: 4-Butoxy-4'-hydroxydiphenyl sulfone
When recording was carried out on a thermal printer, the thermorespon-
sive recording paper sheets Nos. 1-9 produced distinct images with good
preservability at high degree of dynamic responsiveness.
Example 10
Dispersion A:
3-Diethylamino-6-methyl-7-anilinofluoran 1 part
5% polyvinyl alcohol solution 5 parts
Water 40 parts
Dispersion B:
Same as Dispersion B in Example 3 50 parts
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Example 11
Dispersion A:
Same as Dispersion A in Example 10 46 parts
Dispersion B:
Same as Dispersion B in Example 6 50 parts
Using Dispersions A and B of Example 10 or 11, thermoresponsive record-
ing pap~r sheets were prepared in the same manner as mentioned above. The
sheets, when recording was performed by means of a thermal printer, gave
distinct images with good preservability at high degree of responsiveness
in color production.
