[0001] This invention relates to a thermal sensitive recording sheet which has an excellent
image stability.
[0002] In general, a thermal recording sheet can be obtained be obtained by following procedure
; A colourless or pale coloured basic leuco dye and a colour developer such as a phenolic
compound are separately ground to fine particles, then mixed together and dispersed.
By adding a binder, a filler, a sensitizer, a slip agent, and other additives to the
said mixture, a coating colour can be obtained. The obtained coating colour is coated
on a substrate such as paper, synthetic paper, none-woven cloth, film or plastic,
thus a thermal sensitive recording sheet is prepared, which develops colour by a momentary
chemical reaction caused by heating with a thermal pen, a thermal head, a hot stamp,
laser light or the like.
[0003] These thermal recording sheets can be applied in a wide variety of fields such as
measuring recorders, terminal printers for computers, facsimiles, automatic ticket
venders, ATM (Automatic Teller Machine of bank), HT (Handy Terminal), bar code labels
or the like. However, according to the recent advance for manifold application and
high performance of these recording apparatus, a required quality improvement for
the thermal sensitive recording sheet are becoming higher. For instance, accompanied
with high speed recording, it is required to the thermal sensitive recording sheet
to possess features of a high density and clear colour image by lower thermal energy,
and on the other hand, it is required also to possess an excellent feature for preservation
such as light resistance, weather resistance and oil resistance.
[0004] As a conventional example of the thermal sensitive recording sheet, for instance,
thermal sensitive recording materials such as disclosed in Japanese Patent publication
4160/68 or in Japanese Patent publication 14039/70 can be mentioned. However, since
the responding speed of these conventional thermal sensitive recording materials is
slow, a sufficient colour developing density can not be expected when the recording
speed is high.
[0005] As a method to improve above mentioned defect, developments of high sensitive dye
such as a leuco dye which uses 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane
(Japanese Patent Laid-open publication 109120/74) or 3-dibuthylamino-6-methyl-7-anilinofluorane
(Japanese Patent Laid-open publication 190891/84) have been proposed. Further, methods
attempting to obtain a high speed recording and a high sensitivity are proposed by
using a substance which has a good colour developing ability such as 1,7-bis(4-hydroxyphenylthio)-3,5-dioxahepthane
(Japanese Patent Laid-open publication 106456/84), 1. 5-bis (4-hydroxyphenylthio)
-3-oxaheptane (Japanese Patent Laid-open publication 116262/84), 4-hydroky-4'-isopropoxy
diphenylsulfone (Japanese Patent Laid-open publication 106456/84) as a colour developer
have been disclosed.
[0006] Meanwhile, the inventor of this invention has already proposed a thermal sensitive
recording sheet which uses a newly developed derivative of urea (thiourea) as a colour
developer. Said thermal sensitive recording sheet can sufficiently be used for a high
energy printing, but in a case of lower energy printing or a high speed printing,
an enough colour developing density can not be obtained, furthermore, a stability
of recorded image against the plasticizer included in polyvinylchloride film is not
sufficient. So it is thought to be impossible to put said thermal sensitive recording
sheet to a practical use.
[0007] The object of the present invention is to provide a thermal sensitive recording sheet
which has an excellent image stability.
[0008] The inventor has conduced intensive studies to develop a thermal sensitive recording
sheet which has an excellent image stability, and consequently accomplished the present
invention. That is, the above mentioned object can be solved by including a derivative
of urea (thiourea) indicated by general formula (I) or (II) in a thermal sensitive
colour developing layer as an organic colour developer, and also including 0.01-2
parts of a derivative of diphenylsulfone indicated by general formula (III) based
on 1 part of colour developer indicated by general formula (I) or (II) as a stabilizer.

(in this formula, "A" indicates a hydrogen atom, an alkyl group of C
1-C
4, an alkoxy group of C
1-C
4, a hydroxy group or a nitro group, "R
1" "R
2" and "R
3" indicates a hydrogen atom, an alkyl group of C
1-C
4, an alkoxy group of C
1-C
4, a hydroxy group or a nitro group. "R
1" and "R
2" can be mutually combined and form an aromatic ring. Further, "Y" indicates a sulfur
or an oxygen atom.)

(in this formula, "B" indicates a hydrogen atom, an alkyl group of C
1-C
4, an alkoxy group of C
1-C
4, a hydroxy group or a nitro group, "R
1" "R
2" and "R
3" indicates a hydrogen atom, an alkyl group of C
1-C
4, an alkoxy group of C
1-C
4, a hydroxy group or a nitro group. "R
1" and "R
2" can be mutually combined and form an aromatic ring. Further, "Y" indicates a sulfur
or an oxygen atom.)

[0009] A C
1-C
4 alkyl group is, for example, methyl, ethyl, i-propyl, n-propyl, t-butyl, s-butyl
or n-butyl. A C
1-C
4 alkoxy group is, for example, methoxy, ethoxy, i-propoxy, n-propoxy, t-butoxy, s-butoxy
or n-butoxy. When R
1 and R
2 form, together with the carbon atoms to which they are attached, an aromatic ring
that aromatic ring is, for example, a benzene ring which forms a naphthalene ring
system with the benzene ring to which it is attached.
[0010] In the present invention, a derivative of urea (thiourea) indicated by general formula
(I) or (II) indicates stronger acidity than a phenolic compound which is a well-known
colour developer, and performs very strong colour developing ability to a basic leuco
dye. The ground of said fact is explained as follows. That, is in a molecule of a
derivative of urea (thiourea) used in this invention, since two electron extractive
groups e.g. a sulfonyl group, a carbonyl group or a thiocarbonyl group exist so as
to put one benzene ring between, an electron density surrounding a nitrogen atom is
remarkably fallen down and consequently results a strong colour developing ability
to a basic leuco dye.
[0011] Further, in this invention, since the molecule of stabilizer indicated by general
formula (III) possesses a sulfone group, when it is fused by heat together with the
organic colour developer indicated by general formula (I) or (II), it makes an electron
density surrounding a nitrogen atom fall down more, and consequently effects to improve
the preservable stability of a recording image.
[0012] As the substantial examples of a derivative of urea (thiourea) used in this invention,
following compounds are mentioned, however, it is not intended to be limited to them.
This derivatives of urea (thiourea) can be used alone or by mixing with others.
N-(benzenesulfonyl)-p-(phenylureylene)benzamide
N-(4-toluenesulfonyl)-p-(phenylureylene)benzamide
N-(4-ethylphenylsulfonyl)-p-(phenylureylene)benzamide
N-(4-n-propylphenylsulfonyl)-p-(phenylureylene)benzamide
N-(4-iso-propylphenylsulfonyl)-p-(phenylureylene)benzamide
N-(t-butylphenylsulfonyl)-p-(phenylureylene)benzamide
N-(4-methoxyphenylsulfonyl)-p-(phenylureylene)benzamide
N-(4-ethoxyphenylsulfonyl)-p-(phenylureylene)benzamide
N-(4-hydroxyphenylsulfonyl)-p-(phenylureylene)benzamide
N-(2-hydroxyphenylsulfonyl)-p-(phenylureylene)benzamide
N-(4-nitrophenylsulfonyl)-p-(phenylureylene)benzamide
N-(benzenesulfonyl)-p-(4-tolylureylene)benzamide
N-(4-toluenesulfonyl)-p-(4-tolylureylene)benzamide
N-(4-ethlphenylsulfonyl)-p-(4-tolylureylene)benzamide
N-(4-iso-propylphenylsulfonyl)-p-(4-tolylureylene)benzamide
N-(n-butylphenylsulfonyl)-p-(4-tolylureylene)benzamide
N-(4-methoxyphenylsulfonyl)-p-(4-tolylureylene)benzamide
N-(4-hydroxyphenylsulfonyl)-p-(4-tolyoureylene)benzamide
N-(2-hydroxyphenylsulfonyl)-p-(4-tolyoureylene)benzamide
N-(4-nitrophenylsulfonyl)-p-(4-tolylureylene)benzamide
N-(benzenesulfonyl)-p-(2-naphthylureylene)benzamide
N-(4-toluenesulfonyl)-p-(2-naphthylureylene)benzamide
N-(4-iso-propylphenylsulfonyl)-p-(2-naphthylureylene) benzamide
N-(4-methoxyphenylsulfonyl)-p-(2-naphthylureylene)benzamide
N-(4-hydroxyphenylsulfonyl)-p-(2-naphthylureylene)benzamide
N-(4-nitrophenylsulfonyl)-p-(2-naphthylureylene)benzamide
N-(benzenesulfonyl)-p-(phenylthioureylene)benzamide
N-(4-toluenesulfonyl)-p-(phenylthioureylene)benzamide
N-(4-ethylphenylsulfonyl)-p-(phenylthioureylene)benzamide
N-(4-n-propylphenylsulfonyl)-p-(phenylthioureylene) benzamide
N-(4-iso-propylphenylsulfonyl)-p-(phenylthioureylene) benzamide
N-(4-methoxyphenylsulfonyl)-p-(phenylthioureylene)benzamide
N-(4-ethoxyphenylsulfonyl)-p-(phenylthioureylene)benzamide
N-(4-hydroxyphenylsulfonyl)-p-(phenylthioureylene)benzamide
N-(2-hydroxyphenylsulfonyl)-p-(phenylthioureylene)benzamide
N-(4-nitrophenylsulfonyl)-p-(phenylthioureylent)benzamide
N-(benzenesulfonyl)-p-(4-tolylthioureylene)benzamide
N-(4-toluenesulfonyl)-p-(4-tolylthioureylene)benzamide
N-(4-n-propylphenylsulfonyl)-p-(4-tolylthioureylene) benzamide
N-(4-methoxyphenylsulfonyl)-p-(4-methylphenylthioureylene) benzamide
N-(4-hydroxyphenylsulfonyl)-p-(4-tolylthioureylene) benzamide
N-(2-hydroxyphenylsulfonyl)-p-(4-methylphenylthioureylene) benzamide
N-(4-nitrophenylsulfonyl)-p-(4-methylphenylthioureylene) benzamide
N-(benzenesulfonyl)-p-(2-naphthylthioureylene)benzamide
N-(4-toluenesulfonyl)-p-(2-naphthylthioureylene)benzamide
N-(4-methoxyphenylsulfonyl)-p-(2-naphthylthioureylene) benzamide
N-(4-hydroxyphenylsulfonyl)-p-(2-naphthylthioureylene) benzamide
N-(2-hydroxyphenylsulfonyl)-p-(2-naphthylthioureylene) benzamide
N-(4-nitrophenylsulfonyl)-p-(2-naphthylthioureylene) benzamide
N-(phenyl)-N'-(p-benzoylaminosulfonyl)phenylurea
N-(phenyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylurea
N-(phenyl)-N'-{p-(2-naphthoylaminosulfonyl)}phenylurea
N-(phenyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)}phenylurea
N-(phenyl)-N'-{p-(2-hydroxybenzoylaminosulfonyl)}phenylurea
N-(phenyl)-N'-{p-(4-methoxybenzoylaminosulfonyl)}phenylurea
N-(phenyl)-N'-{p-(4-ethoxybenzoylaminosulfonyl)}phenylurea
N-(phenyl)-N'-{p-(4-n-propoxybenzoylaminosulfonyl)} phenylurea
N-(phenyl)-N'-{p-(4-iso-propoxybenzoylaminosulfonyl)} phenylurea
N-(phenyl)-N'-{p-(4-nitrobenzoylaminosulfonyl)}phenylurea
N-(4-toluyl)-N'-(p-benzoylaminosulfonyl)phenylurea
N-(4-toluyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylurea
N-(4-toluyl)-N'-{p-(2-naphthoylaminosulfonyl)}phenylurea
N-(3-toluyl)-N'-(p-benzoylaminosulfonyl)phenylurea
N-(3-toluyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylurea
N-(3-toluyl)-N'-{p-(3-toluoylaninosulfonyl)}phenylurea
N-(3-toluyl)-N'-{p-(2-toluoylaminosulfonyl)}phenylurea
N-(3-toluyl)-N'-{p-(2-naphthoylaminosulfonyl)}phenylurea
N-(4-toluyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)} phenylurea
N-(4-toluyl)-N'-{p-(2-hydroxybenzoylaminosulfonyl)} phenylurea
N-(4-toluyl)-N'-{p-(4-methoxybenzoylaminosulfonyl)} phenylurea
N-(4-toluyl)-N'-{p-(4-nitrobenzoylaminosulfonyl)}phenylurea
N-(phenyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylthiourea
N-(phenyl)-N'-{p-(2-naphthoylaminosulfonyl)}phenylthiourea
N-(phenyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)} phenylthiourea
N-(phenyl)-N'-{p-(4-methoxybenzoylaminosulfonyl)} phenylthiourea
N-(phenyl)-N'-{p-(4-nitrobenzoylaminosulfonyl)} phenylthiourea
N-(4-toluyl)-N'-(p-benzoylaminosulfonyl)phenylthiourea
N-(4-toluyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylthiourea
N-(4-toluyl)-N'-{p-(3-toluoylaminosulfonyl)}phenylthiourea
N-(4-toluyl)-N'-{p-(2-naphthoylaminosulfonyl)} phenylthiourea
N-(3-toluyl)-N'-(p-benzoylaminosulfonyl)phenylthiourea
N-(3-toluyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylthiourea
N-(3-toluyl)-N'-{p-(3-toluoylaminosulfonyl)}phenylthiourea
N-(3-toluyl)-N'-{p-(2-naphthoylaminosulfonyl)} phenylthiourea
N-(4-toluyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)} phenylthiourea
N-(4-toluyl)-N'-{p-(4-methoxybenzoylaminosulfonyl)} phenylthiourea
N-(4-toluyl)-N'-{p-(4-nitrobenzoylaminosulfonyl)} phenylthiourea
[0013] In this invention, as a stabilizer, a derivative of diphenylsulfone indicated by
general formula (III) is used. In this invention, if the proportion of a stabilizer
indicated by general formula (III) is smaller than 0.01 parts based on 1 part of an
organic colour developer indicated by general formula (I) and (II), the stabilizing
effect is not sufficient, and if it is bigger than 2 parts based on 1 part of an organic
colour developer the enough stabilizing effect can not be expected. Therefore, the
most desirable proportion of the stabilizer is 0.01-2 parts based on 1 part of the
organic colour developer.
[0014] As the basic leuco dye used in this invention, triphnylmethane type, fluorane type,
fluorene type and divinyl type are desirably used, however, it is not intended to
be limited to them. The substantial examples of them are indicated below. These dyes
can be used alone or by mixing with others.
<triphenylmethane-based leuco dye>
[0015] 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide [another name is crystal
violet lactone]
<fluoran-based leuco dye(I)>
[0016]
3-diethylamino-6-methyl-7-anilinofluoran
3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran
3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran
3-diethylamino-6-methyl-7-(o,p-dimethylanilino)fluoran
3-pyrrolidino-6-methyl-7-anilinofluoran
3-piperidino-6-methyl-7-anilinofluoran
3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran
3-diethylamino-7-(m-trifluoromethylanilino)fluoran
3-N-n-dibutylamino-6-methyl-7-anilinofluoran
3-N-n-dibutylamino-7-(o-chloroanilino)fluoran
3-(n-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran
3-dibutylamino-6-methyl-7-(o,p-dimethylanilino)fluoran
3-(n-methyl-N-propylamino)-6-methyl-7-anilinofluoran
3-diethylamino-6-chloro-7-anilinofluoran
3-dibutylamino-7-(o-chloroanilino)fluoran
3-diethylamino-7-(o-chloroanilino)fluoran
3-diethylamino-6-methyl-chlorofluoran
3-diethylamino-6-methyl-fluoran
3-cyclohexylamino-6-chlorofluoran
3-diethylamino-benzo[a]-fluoran
3-n-dipentylamino-6-methyl-7-anilinofluoran
2-(4-oxo-hexyl)-3-dimethylamino-6-methyl-7-anilinofluoran
2-(4-oxo-hexyl)-3-diethylamino-6-methyl-7-anilinofluoran
2-(4-oxo-hexyl)-3-dipropylamino-6-methyl-7-anilinofluoran
<fluorene-based leuco dye>
[0017]
3,6',6'-tris(dimethylamino)spiro(fluorene-9, 3'-phthalide]
3,6',6'-tris(diethylamino)spiro[fluorene-9,3'-phthalide]
<fluoran-based leuco dye(II)>
[0018]
2-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran
2-methoxy-6-p-(p-dimethylaminophenyl)aminoanilinofluoran
2-chloro-3-methyl-6-p-(p-phenylaminophenyl) aminoanilinofluoran
2-chloro-6-p-(p-dimethylaminophenyl)aminoanilinofluoran
2-nitro-6-p-(p-diethylaminophenyl)aminoanilinofluoran
2-amino-6-p-(p-diethylaminophenyl)aminoanilinofluoran
2-diethylamino-6-p-(p-diethylaminophenyl) aminoanilinofluoran
2-phenyl-6-methyl-6-p-(p-phenylaminophenyl) aminoanilinofluoran
2-benzyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran
2-hydroxy-6-p-(p-phenylaminophenyl)aminoanilinofluoran
3-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran
3-diethylamino-6-p-(p-diethylaminophenyl) aminoanilinofluoran
3-diethylamino-6-p-(p-dibutylaminophenyl) aminoanilinofluoran
<divinyl-based leuco dye>
[0019]
3,3-bis-[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl) ethenyl] -4,5,6,7-tetrabromophthalide
3,3-bis-(2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl) ethenyl]-4,5,6,7-tetrachlorophthalide
3, 3-bis- [1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl] -4, 5, 6, 7-tetrabromophthalide
3,3-bis-[1-(4-methoxyphenyl)-1-(4-pyrrolidinophenyl) ethylene-2-yl]-4,5,6, 7-tetrachlorophthalide
<others>
[0020]
1,1-bis-[2',2',2",2"-tetrakis-(p-dimethylaminophenyl)ethenyl]-2,2-dinitrileethane
1,1-bis-[2',2',2",2"-tetrakis-(p-dimethylaminophenyl)ethenyl]-2-β-naphthoylethane
1,1-bis-[2',2',2",2"-tetrakis-(p-dimethylaminophenyl)ethenyl]-2,2-diacetylethane
bis-[2,2,2',2'-tetrakis-(p-dimethylaminophenyl)-ethenyl]methymalonatedimethyl ester
[0021] In the present invention, the conventional public known sensitizer can be used as
far as it does not hurt the necessary effects of this invention. As the substantial
example of the sensitizer, following compounds can be mentioned :
fatty acid amide such as amide stearate or amide palmitate
ethylene bisamide
montane-based wax
polyethylene wax
dibenzyl terephthalate
p-benzyloxybenzylbenzoate
di-p-tolylcarbonate
p-benzylbiphenyl
phenyl-a-naphthylcarbonate
1,4-diethoxynaphthalene
l-hydroxy-2-naphthoeic acid phenyl ester
1,2-di-(3-methylphenoxy)ethane
di(p-methylbenzyl)oxalate
β-benzyloxynaphthalene
4-biphenyl-p-tolyleter
o-xylylene-bis-(phenylether)
4-(m-methylphenoxymethyl)biphenyl
[0022] These sensitizers can be used alone or by mixing with others.
[0023] As a binder to be used in this invention, full saponificated polyvinylalcohol having
200-1900 polymerization degree, partially saponificated polyvinylalcohol, denatured
polyvinylalcohol such as carboxy denatured polyvinylalcohol, amide denatured polyvinylalcohol,
sulfonic acid denatured polyvinylalcohol and buthylal denatured polyvinylalcohol,
hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, copolymer of styrene-maleic
anhydryde, copolymer of styrene-buthadien, derivatives of cellulose such as ethyl-cellulose
or acetyl-cellulose, polyvinylchrolide, polyvinylacetate, polyacrylicamide, polyacrilate,
polyvinylbuthylal, polystyrene and copolymer of these polymers, polyamide resin, silicon
resin, petroleum resin, terpene resin, ketone resin, cumarone resin can be mentioned.
These kinds of macromolecule compound can be used by dissolving in water or in solvents
such as alcohol, ketone, ester of hydrocarbon, and also can be used by dispersing
it by emulsion or paste state in water or other solvent. These methods can be used
in combination with, if necessary.
[0024] As a filler to be used in this invention, following inorganic or organic filler such
as silica, calcium carbonate, kaoline, calcined kaoline, diatomaceous earth, talk,
titanium oxide, aluminium hydroxide, urea-formalin resin or hollow plastic pigment
can be mentioned.
[0025] Further, parting agents such as metallic salt of fatty acid, lubricant such as wax,
ultra violet lay absorder such as benzophenone group or triazole group, waterproof
agent such as glyoxal, dispersing agents and deformer can be used in this invention.
EXAMPLES
[0026] The present invention will be more clearly understood with reference to the following
Examples.
[0027] The thermal sensitive recording sheet of this invention can be obtained by following
procedure, that is ; prepare the coating colour of thermal sensitive colour developing
layer by grinding and dispersing a basic leuco dye, a derivative of urea (thiourea)
indicated by aforementioned general formula (I) or (II) as an organic colour developer
and a derivative of diphenylsulfone indicated by aforementioned general formula (III)
as a stabilizer together with a binder, and adding a filler and other additives according
to the necessity, then coating the obtained coating colour on the substrate and drying
it up. A proportion of a derivative of diphenylsulfone indicated by aforementioned
general formula (III) to be added to one part of an organic developer indicated by
general formula (I) or (II) is 0.01-2 parts.
[0028] The type and the amount of an organic developer, a basic leuco dye and other additives
are decided according to the required features and to the recording property, and
generally the preferable amount of these compounds are follows, however, are not intended
to be limited. That is, 0.01-2 parts of stabilizer indicated by general formula (III),
0.1-2 parts of basic leuco dye and 0.5-4 parts of filler based on 1 part of organic
developer indicated by general formula (I) or (II). The preferable amount of binder
is 5-25 % to the total amount of solid.
[0029] By coating the coating colour having above mentioned composition on a voluntarily
selected supporter such as a paper, a non woven cloth, a film or a plastic, an objected
thermal sensitive recording sheet can be obtained. Further, for the purpose of improve
the preservability, an overcoat layer of a macromolecule including a filler can be
prepared on the thermal sensitive colour developing layer. And, furthermore, for the
purpose to improve both preservability and sensitivity, an undercoat layer including
an organic or an inorganic filler can be prepared under the thermo sensitive colour
developing layer.
[0030] These organic developer, basic leuco dye, sensitizer and other additives to be added
as necessary are ground to the fine particles smaller than one micron size level by
means of a pulverizer such as a ball mill, an attritor or a sand grinder, or by means
of an adequate emulsifying apparatus, and binder and other additives are added in
accordance with the necessity, thus the coating colour is prepared.
[0031] The present invention is further illustrated by following Examples and Comparative
Examples. In the illustration, the term of "parts" means "parts by weight".
EXAMPLE 1 (experiment No. 1-32)
[0032]
Solution A (dispersion of dye) |
3-N-n-dibuthylamino-6-methyl-7-anilinofluoran |
2.0 parts |
10% polyvinylalcohol aqueous solution |
4.6 parts |
water |
2.5 parts |
Solution B (dispersion of colour developer) |
colour developer (refer to table 1 and 2) |
6.0 parts |
10% polyvinylalcohol aqueous solution |
18.8 parts |
water |
11.2 parts |
Solution C (dispersion of stabilizer) |
stabilizer 4-benziloxy-4'-(2,3-epoxy-2-methylpropoxy) diphenyl sulfone |
4.0 parts |
10% polyvinylalcohol aqueous solution |
12.5 parts |
water |
7.5 parts |
[0033] These three kinds of dispersion are separately ground to average diameter of 1µm
by means of a sand grinder. Then the resulting dispersion are mixed together in the
proportion below so as to prepare the coating colour.

[0034] The prepared coating colours are applied to one side of 50g/m
2 sheet paper so as obtain a coating weight of 5.0g /m
2 amount, dried up and the sheet is processed by a super calender to surface smoothness
of 400-500 second. Thus the thermal sensitive recording paper can be obtained.
COMPARATIVE EXAMPLE 1 (experiment No.33-37)
[0035]
Solution A (dispersion of dye) |
3-N-n-dibuthylamino-6-methyl-7-anilinofluoran |
2.0 parts |
10% polyvinylalcohol aqueous solution |
4.6 parts |
water |
2.5 parts |
Solution D (dispersion of colour developer) |
colour developer (refer to table 5) |
6.0 parts |
10% polyvinylalcohol aqueous solution |
18.8 parts |
water |
11.2 parts |
[0036] These two kinds of dispersion are separately ground to average diameter of 1µm by
means of a sand grinder. Then the resulting dispersion are mixed together in the proportion
below so as to prepare the coating colour.
Solution A (dispersion dye) |
9.1 parts |
Solution D (dispersion of colour developer) |
36.0 parts |
Kaoline clay (50% dispersion) |
12.0 parts |
[0037] The prepared coating colours are applied to one side of 50g/m
2 sheet paper so as obtain a coating weight of 5.0g /m
2 amount, dried up and the sheet is processed by a super calender to surface smoothness
of 400-500 second. Thus the thermal sensitive recording paper can be obtained.
COMPARATIVE EXAMPLE 2 (experiment No.38-42)
[0038]
Solution A (dispersion of dye) |
3-N-n-dibuthylamino-6-methyl-7-anilinofluoran |
2.0 parts |
10% polyvinylalcohol aqueous solution |
4.6 parts |
water |
2.5 parts |
Solution E (dispersion of colour developer) |
colour developer (refer to table 5) |
6.0 parts |
10% polyvinylalcohol aqueous solution |
18.8 parts |
water |
11.2 parts |
Solution C (dispersion of stabilizer) |
stabilizer 4-benziloxy-4'-(2,3-epoxy-2-methylpropoxy) diphenyl sulfone |
4.0 parts |
10% polyvinylalcohol aqueous solution |
12.5 parts |
water |
7.5 parts |
[0039] These three kinds of dispersion are separately ground to average diameter of 1µm
by means of a sand grinder. Then the resulting dispersion are mixed together in the
proportion below so as to prepare the coating colour.
Solution A (dispersion dye) |
9.1 parts |
Solution E (dispersion of colour developer) |
36.0 parts |
Solution C (dispersion of stabilizer) |
24.0 parts |
Kaoline clay (50% dispersion) |
12.0 parts |
[0040] The prepared coating colours are applied to one side of 50g/m
2 sheet paper so as obtain a coating weight of 5.0g /m
2 amount, dried up and the sheet is processed by a super calender to surface smoothness
of 400-500 second. Thus the thermal sensitive recording paper can be obtained.
[0041] Quality evaluation tests mentioned below are carried out on thermal sensitive recording
papers prepared in above mentioned Examples and Comparative Examples. The obtained
results are summarized in table 3, 4 and 6. In the tables, stabilizer (III) indicates
compound of 4-benziloxy-4'-(2,3-epoxy-2-methylpropoxy)diphenylsulfone.
[0042] Remark (1) resistance against plasticizer ; are carried out using TH-PMD (thermal
sensitive recording paper testing apparatus, to which thermal head [Kyosera Ltd.]
is installed) made by Ohkura Denki Ltd., by 0.38mj/dot impressive energy. Image density
of the recorded portion of each specimen is measured by a Macbeth densitometer (RD-914,
an amber filter is used), and the obtained results are regarded as the image density
of untreated specimen. Wrapping film of polyvinylchloride (High Wrap KMA ; product
of Mitsui Toatsu Ltd.) is wound around a paper tube to form a single layer, recorded
sheet of the thermal sensitive recording paper is stuck on it, then the wrapping film
of polyvinylchloride is wound over the sheet to form a quarto layer. This specimen
is left for 4 hours in the chamber of 40°C, then the Macbeth density of image portion
is measured and the obtained results are regarded as the image density after treated.
Table 1
The Results of Quality Evaluation Tests |
Test No. |
colour developer |
stabilizer |
Ex.1 |
1 |
N-(benzenesulfonyl)-p-(phenylureylene)benzamide |
(III) |
2 |
N-(4-toluenesulfonyl)-p-(phenylureylene)benzamide |
(III) |
3 |
N-(benzenesulfonyl)-p-(phenylthioureylene)benzamide |
(III) |
4 |
N-(4-toluenesulfonyl)-p-(phenylthioureylene)benzamide |
(III) |
5 |
N-(4-methoxyphenylsulfonyl)-p-(phenylureylene)benzamide |
(III) |
6 |
N-(2-hydroxyphenylsulfonyl)-p-(phenylureylene)benzamide |
(III) |
7 |
N-(4-toluenesulfonyl)-p-(4-tolylureylene)benzamide |
(III) |
8 |
N-(n-butylphenylsulfonyl)-p-(4-tolylureylene)benzamide |
(III) |
9 |
N-(2-hydroxyphenylsulfonyl)-p-(4-tolylureylene)benzamide |
(III) |
10 |
N-(4-toluenesulfonyl)-p-(2-naphthylureylene)benzamide |
(III) |
11 |
N-(4-hydroxyphenylsulfonyl)-p-(2-naphthylureylene)benzamide |
(III) |
12 |
N-(4-toluenesulfonyl)-p-(phenylureylene)benzamide |
(III) |
13 |
N-(4-iso-propylphenylsulfonyl)-p-(phenylthioureylene)benzamide |
(III) |
14 |
N-(4-hydroxyphenylsulfonyl)-p-(phenylthioureylene)benzamide |
(III) |
15 |
N-(benzenesulfonyl)-p-(4-tolylthiourne)benzamide |
(III) |
16 |
N-(4-methoxyphenylsulfonyl)-p-(4-methylphenylthioureylene)benzamide |
(III) |
Table 2
The Results of Quality Evaluation Tests |
|
Test No. |
colour developer |
stabilizer |
Ex.1 |
17 |
N-(phenyl-N'-(p-benzoylaminosulfonyl)phenylurea |
(III) |
18 |
N-(phenyl)-N'-{p-(benzoylaminosulfonyl)} |
(III) |
19 |
N-(phenyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)}phenylurea |
(III) |
20 |
N-(phenyl)-N'-{p-(4-ethoxybenzoylaminosulfonyl)}phenylurea |
(III) |
21 |
N-(phenyl)-N'-{p-(4-nitrobenzoylaminosulfonyl)}phenylurea |
(III) |
22 |
N-(4-toluyl)-N'-{p-(2-naphthoilaminosulfonyl)}phenylurea |
(III) |
23 |
N-(3-toluyl)-N'-{p-(3-toluoylaminosulfonyl)}phenylurea |
(III) |
24 |
N-(4-toluyl)-N'{p-(4-hydroxybenzoylaminosulfonyl)}phenylurea |
(III) |
25 |
N-(4-toluyl)-N'-{p-(4-nitrobenzoylaminosulfonyl)}phenylurea |
(III) |
26 |
N-(phenyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylthiourea |
(III) |
27 |
N-(phenyl)-N'-{p-(2-naphthoylaminosulfonyl)}phenylthiourea |
(III) |
28 |
N-(phenyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)}phenylthiourea |
(III) |
29 |
N-(phenyl)-N'-{p-(4-methoxybenzoylaminosulfonyl)}phenylthiourea |
(III) |
30 |
N-(4-toluyl)-N'-{p-(2-naphthoylaminosulfonyl)}phenylthiourea |
(III) |
31 |
N-(3-toluyl)-N'-(p-benzoylaminosulfonyl)phenylthiourea |
(III) |
32 |
N-(3-toluyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylthiourea |
(III) |
Table 3
The Results of Quality Evaluation Tests |
|
Test No. |
resistance against plasticizer (1) |
|
|
untreated |
treated |
Example-1 |
1 |
1.19 |
0.81 |
2 |
1.19 |
0.76 |
3 |
1.18 |
0.72 |
4 |
1.25 |
0.73 |
5 |
1.19 |
0.76 |
6 |
1.26 |
0.73 |
7 |
1.18 |
0.76 |
8 |
1.22 |
0.74 |
9 |
1.17 |
0.79 |
10 |
1.24 |
0.74 |
11 |
1.19 |
0.72 |
12 |
1.22 |
0.71 |
13 |
1.19 |
0.75 |
14 |
1.25 |
0.81 |
15 |
1.23 |
0.79 |
16 |
1.21 |
0.78 |
Table 4
The Results of Quality Evaluation Tests |
|
Test No. |
resistance against plasticizer (1) |
|
|
untreated |
treated |
Example-2 |
17 |
1.21 |
0.81 |
18 |
1.22 |
0.75 |
19 |
1.23 |
0.78 |
20 |
1.19 |
0.84 |
21 |
1.18 |
0.75 |
22 |
1.20 |
0.76 |
23 |
1.21 |
0.71 |
24 |
1.19 |
0.72 |
25 |
1.23 |
0.77 |
26 |
1.24 |
0.74 |
27 |
1.20 |
0.73 |
28 |
1.18 |
0.76 |
29 |
1.24 |
0.74 |
30 |
1.23 |
0.79 |
31 |
1.20 |
0.77 |
32 |
1.18 |
0.75 |
Table 5
The Results of Quality Evaluation Tests |
|
Test No. |
colour developer |
stabilizer |
Com. Ex.1 |
33 |
N-(benzenesulfonyl)-p-(phenylthioureylene)benzamide |
none |
34 |
N-(4-toluenesulfonyl)-p-phenylthioureylene)benzamide |
none |
35 |
N-(benzenesulfonyl)-p-(phenylureylene)benzamide |
none |
36 |
N-(4-toluenesulfonyl)-p-phenylthioureylene)benzamide |
none |
37 |
N-(4-methoxyphenylsulfonyl)-p-(phenylureylene)benzamide |
none |
Com. Ex.2 |
38 |
4,4'-dihydroxydiphenylsulfone |
(III) |
39 |
4-hydroxy-4'-isopropoxydiphenylsulfone |
(III) |
40 |
4-hydroxy-4'-n-butoxydiphenylsulfone |
(III) |
41 |
4,4'-isopropylidenediphenol |
(III) |
42 |
4-hydroxy-4'-n-propoxydiphenylsulfone |
(III) |
Table 6
The Results of Quality Evaluation Tests |
|
Test No. |
resistance against plasticizer (1) |
|
|
untreated |
treated |
Com. Ex.1 |
33 |
1.18 |
0.26 |
34 |
1.19 |
0.28 |
35 |
1.17 |
0.27 |
36 |
1.18 |
0.29 |
37 |
1.16 |
0.28 |
Com. Ex.2 |
38 |
1.21 |
0.23 |
39 |
1.23 |
0.22 |
40 |
1.24 |
0.23 |
41 |
1.22 |
0.22 |
42 |
1.25 |
0.20 |
[0043] As clearly understood from the test results shown in table 3, 4 and 6, the specimens
of thermal sensitive recording sheets prepared by Examples 1 of this invention which
use the colour developer indicated by general formula (I) and (II) and the stabilizer
indicated by general formula (III) have a remarkable superior image stability to a
plasticizer. On the contrary, the effects of image stability to a plasticizer of the
specimens prepared by Comparative Example 1 which do not use the stabilizer indicated
by general formula (III) and the specimens prepared by Comparative Example 2 which
use a typical well-known phenolic colour developer (for instance, bisphenol A) in
combination with the stabilizer indicated by general formula (III) are inferior, and
the image density after treated is low. Therefore, it is clearly understood that an
excellent effect can be expected only in a case using the compound of general formula
(I) or (II) together with the compound of general formula (III).
[0044] In the present invention, by using a derivative of urea (thiourea) indicated by aforementioned
general formula (I) or (II) as a colour developer, and by using a derivative of diphenylsulfone
indicated by aforementioned general formula (III) as a stabilizer, an excellent sharp
recording image which has good preserving stability can be obtained even in a high
speed and high density recording condition.
1. A thermally sensitive recording sheet which comprises, on a substrate, a thermally
sensitive colour developing layer comprising:
(a) a colourless or pale coloured basic leuco dye;
(b) an organic colour developer of formula (I):

wherein A is hydrogen, C1-C4 alkyl, C1-C4 alkoxy, hydroxy or nitro, each of R1, R2 and R3, which may be the same or different, is hydrogen, C1-C4 alkyl, C1-C4 alkoxy, hydroxy or nitro, or R1 and R2 form, together with the carbon atoms to which they are attached, an aromatic ring,
and Y is sulfur or oxygen; or an organic colour developer of formula (II):

wherein B is hydrogen, C1-C4 alkyl, C1-C4 alkoxy, hydroxy or nitro, each of R1, R2 and R3, which may be the same or different, is hydrogen, C1-C4 alkyl, C1-C4 alkoxy, hydroxy or nitro, or R1 and R2 form, together with the carbon atoms to which they are attached, an aromatic ring,
and Y is sulfur or oxygen; and
(c) 0.01-2 parts, based on 1 part of colour developer of formula (I) or (II), of a
stabiliser which is a diphenylsulfone derivative of formula (III):

2. A recording sheet according to claim 1 wherein, in the organic colour developer of
formula (I) or (II), A or B, respectively, is hydrogen, methyl, ethyl, n-propyl, i-propyl,
t-butyl, methoxy, ethoxy, n-propoxy, i-propoxy, hydroxy or nitro.
3. A recording sheet according to claim 1 or 2 wherein, in the organic colour developer
of formula (I) or (II), each of R1, R2 and R3, which may be the same or different, is hydrogen, methyl, ethyl, n-propyl, i-propyl,
t-butyl, methoxy, ethoxy, n-propoxy, i-propoxy, hydroxy or nitro.
4. A recording sheet according to any one of the preceding claims wherein the thermally
sensitive colour developing layer further includes a sensitizer, binder, metallic
salt, filler, lubricant, UV absorbent, waterproofing agent, dispersing agent, deformer,
antioxidant or fluorescent dye.
5. A recording sheet according to any one of the preceding claims wherein the colourless
or pale coloured basic leuco dye is selected from fluoran-based leuco dyes, triphenylmethane-based
leuco dyes, fluorene-based leuco dyes and divinyl-based leuco dyes.
6. A recording sheet according to any one of the preceding claims which further includes,
on the thermally sensitive colour developing layer, an overcoating layer which comprises
macromolecules.
7. A recording sheet according to any one of the preceding claims which further includes,
between the thermally sensitive colour developing layer and the substrate, an undercoating
layer which comprises an organic or inorganic filler.
8. A recording sheet according to any one of the preceding claims wherein the substrate
is paper, synthetic paper, plastic film, non-woven cloth or metallic foil, or comprises
a combination thereof.
9. A recording sheet according to any one of the preceding claims wherein the thermally
sensitive colour developing layer is present on the substrate in a coating weight
of 5.0 g/m2.