Thermosensitive recording material

A thermosensitive recording material is disclosed, which comprises a colorless or light-colored coloring material, and a color developer capable of inducing color formation in the colorless or light-colored coloring material upon application of heat thereto, in which the color developer is a phenolic material of the formula ##STR1## wherein R is an alkylene group selected from the group consisting of an alkylene group having 1 to 10 carbon atoms; an alkylene group having 1 to 8 carbon atoms which are not directly bonded to S in the formula, with 1 to 3 carboxylic groups contained therein; and an alkylene group having 2 to 15 carbon atoms, with 1 to 5 ether bonds contained therein.

BACKGROUND OF THE INVENTION 
The present invention relates to a thermosensitive recording material, and 
more particularly to a thermosensitive recording material capable of 
forming images with high density at high speed recording. 
In general, a conventional thermosensitive recording material comprises a 
support material made of, for example, paper or a film, and a 
thermosensitive coloring layer formed on the support material, which 
thermosensitive coloring layer comprises as the main components, a 
colorless or light colored dye such as leuco dye, and a color developer 
such as a phenolic material which is capable of inducing color formation 
in the colorless or light colored dye upon application of heat thereto, 
for example, through a thermal head of a thermal printer. This thermal 
recording is attained by a chemical reaction between the colorless or 
light colored dye and the color developer upon application of heat 
thereto. As compared with other conventional recording materials, the 
above described type thermosensitive recording materials have advantages 
in that recording can be performed without requiring complicated steps 
such as development and image fixing; therefore, such recording is done 
speedly, quietly and at a low cost. Because of these advantages, the 
thermosensitive recording materials are widely used, for instance, for use 
with computers, facsimile apparatus, telex, medical measurement 
instruments and other measuring instruments in a variety of fields. 
In accordance with the recent general demand for high speed recording, 
there is a great demand for a thermosensitive recording material that is 
suitable for use in high speed recording, in particular, for use with the 
above-mentioned fields. 
Conventionally, thermosensitive recording materials for use in high-speed 
recording have been proposed, for instance, in Japanese Laid-Open Patent 
Application No. 53-39139, Japanese Laid-Open Patent Application No. 
53-26139, Japanese Laid-Open Patent Application No. 53-5636, and Japanese 
Laid-Open Patent Application No. 53-11036. In those thermosensitive 
recording materials, thermo-fusible materials with a low melting point, 
such as a variety of waxes, fatty acid amides, alkylated biphenyls, 
substituted biphenyl alkanes, coumarinic acid derivatives, biphenyl 
amines, are added to the thermosensitive coloring layer as a sensitizer or 
as an agent for reducing the melting point of the thermosensitive coloring 
layer. 
In the case where the above described sensitizer agents are employed, it is 
necessary that the sensitizer agent be melted prior to the coloring 
reaction. Therefore, in the high-speed recording by application of a small 
amount of heat energy in an extremely short time, for instance, by 
heat-application impulses, a sufficiently high thermal response for 
practical use cannot be obtained. In addition to the above problem, in the 
above case, since the thermo-fusible materials are melted within the 
thermosensitive coloring layer, the accumulation of the melted 
thermo-fusible materials on a thermal head during an image recording 
process, trailing of the printed images and formation of ghost images are 
apt to occur. Furthermore, fogging is apt to occur in the background of 
thermosensitive recording material during storage at high temperatures and 
high humidities. As a result, the contrast of the recorded images 
decreases during storage. 
Therefore, it is more preferable not to use the above described sensitizer 
agents or melting-point reducing agents in the thermosensitive recording 
materials for use in high speed recording. 
Conventional colorless or light-colored dyes which are colored upon 
application of heat thereto for use in the thermosensitive recording 
materials, for example, dyes having lactone rings, lactam rings or 
spiro-pyran rings, usually have the melting points in the range of 
160.degree. C. to 240.degree. C. Due to such high melting points of the 
colorless or light colored dyes, when the above described sensitizer dyes 
or melting points reducing agents are not employed, phenolic materials 
with particularly low melting points are used in combination as a color 
developer for inducing color formation in the above-mentioned colorless or 
light-colored dyes, in order to obtain thermal recording materials with 
high thermal sensitivities suitable for use in high-speed recording. 
Phenolic color developers are described in many references including 
Japanese Patent Publication No. 45-14039. Among a large number of phenolic 
color developers, 2,2-bis(4'-hydroxyphenyl)propane (or Bisphenol A, m.p. 
156.degree.-158.degree. C.) is preferably used, because of the stability 
of the quality as the color developer, and the reasonable price and 
availability. Bisphenol A, however, has the shortcoming that its color 
inducement temperature is relatively high. 
In contrast to this, in the case where phenolic materials with low melting 
points, for instance, monohydric phenols, such as 4-t-butylphenol (m.p. 
94.degree.-99.degree. C.), .alpha.-naphthol (m.p. 95.degree.-96.degree. 
C.), and .beta.-naphthol (m.p. 119.degree.-122.degree. C.) are employed, 
the preservability and stability of the thermal recording materials are so 
poor that the background thereof is discolored with time at room 
temperature during storage. Further, thermal recording materials 
containing such monophenols therein have a characteristics phenolic odor 
and are not suitable for practical use. 
In Japanese Patent Publication No. 54-12819 and Japanese Patent Laid-Open 
Application No. 55-27253, 2,2-bis(4'-hydroxyl phenyl)-n-hexane (m.p. 
99.degree.-103.degree. C.) and 1,1-bis(4'-hydroxyl phenyl)alkane (the 
alkane having 3 to 13 carbon atoms) are respectively disclosed as having 
low melting points and being capable of yielding images in a stable manner 
when they are employed in thermosensitive recording materials. However, 
these materials are difficult to synthesize and cannot be obtained easily. 
In Japanese Laid-Open Publication No. 56-144193, it is described that a 
lower alkyl ester and a benzyl ester of p-hydroxybenzoic acid can be 
easily synthesized, and, by use of the esters, thermosensitive recording 
materials with high sensitivity can be prepared. However, the 
thermosensitive recording materials using the esters have the shortcomings 
that the colored portions easily discolor and the phenolic materials are 
separated in the developed image areas in the form of white crystals or 
powders. 
As described above, there are known no thermosensitive recording materials 
which yield images with high density, high sharpness and high stability in 
high-speed recording, using a color developer that can be employed for 
industrial and practical use. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide an improved 
thermosensitive recording material which is capable of yielding images 
with high density and high sharpness in a stable manner in high-speed 
recording, by use of a color developer that can be employed for industrial 
and practical use. 
The object of the present invention can be attained by using a phenolic 
material of the following formula as a color developer in the 
thermosensitive recording material which employs a coloring reaction 
between a colorless or light-colored leuco dye and a color developer: 
##STR2## 
wherein R represents an alkylene group having 1 to 10 carbon atoms; an 
alkylene group having 1 to 8 carbon atoms, with 1 to 3 carbonyl groups 
contained within the alkylene group, without being bonded to S in the 
formula; or an alkylene group having 2 to 15 carbon atoms, with 1 to 5 
ether bonds contained within the alkylene group. 
Among the color developers covered by the above formula, the color 
developers with R being the alkylene group having 1 to 5 ether bonds 
induce color formation in a fluoran compound of the following formula 
(II), with particularly excellent image quality and high resistance to 
plasticizers contained, for example, in a polyvinyl chloride film, 
##STR3## 
wherein R.sup.1 and R.sup.2 each represent an alkyl group having 1 to 6 
carbon atoms of a cyclohexyl group; R.sup.3 represents an alkyl group 
having 1 to 2 carbon atoms; and n is an integer of 0 or 1. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The phenolic compounds of the previously described formula (I) employed as 
the color developers can be prepared without difficulty as described later 
by reacting monothiohydroquinone with its counter part dihalogenoalkanes, 
dihalogenoketones or dihalogenoalkyl ethers in the presence of an alkali, 
with high yield and high purity and at a comparatively low cost. 
In the thermosensitive recording material according to the present 
invention, a leuco dye and the color developer can be supported on the 
same support material or they can be supported separately on two different 
support materials. In the case where a leuco dye and the color developer 
are supported on the same support material, a thermosensitive coloring 
layer comprising the leuco dye and the color developer is formed on the 
support material, with addition of a binder agent thereto, or a 
thermosensitive coloring layer comprising two layers, with the leuco dye 
contained in one layer, and the color developer contained in the other 
layer. 
In the case where a leuco dye and the color developer are separately 
supported on the support materials, those support materials are 
superimposed on each other in such a manner that the surface of one 
support material which bears the leuco dye and the surface of the other 
support material which bears the color developer come into contact with 
each other when thermal printing is performed. Thereafter, the two support 
materials are separated, whereby color images are obtained in one support 
material. In other words, the present invention can be applied to any 
conventional thermosensitive recording materials which utilize the 
coloring reaction between a leuco dye and a color developer. 
The thermosensitive recording according to the present invention can also 
be used as a thermal-image-transfer-type thermosensitive recording 
material which comprises an image transfer sheet consisting of a support 
material and an image transfer layer formed on the support material, 
containing a leuco dye, and an image acceptor sheet consisting of a 
support material and an image acceptor layer formed on the support 
material, containing the color developer. 
In the case of the thermal-image-transfer-type recording material, the 
image transfer sheet is superimposed on the image acceptor sheet in such a 
manner that the image acceptor layer comes into contact with the image 
transfer layer of the image transfer sheet, so that thermal printing is 
performed on the front side or back side of the superimposed sheets, 
whereby the desired developed images are formed on the image acceptor 
layer of the acceptor sheet. 
The thermosensitive recording material according to the present invention 
can be prepared, for example, by application of a thermosensitive coloring 
layer formation liquid containing the above described components to a 
support material, for example, paper, synthetic paper or a plastic film, 
and by drying the same. When the leuco dye and the color developer are 
supported on two separate support materials, a leuco dye dispersion or 
solution and a color developer dispersion or solution are applied to each 
support material. 
As colorless or light-colored dyes for use in the present invention, a 
variety of conventional dyes can be employed. 
The following are examples of such colorless or light-colored dyes for use 
in the present invention. 
Crystal Violet Lactone, 
3-diethylamino-6-methyl-7-anilinofluoran, 
3-(N-ethyl-p-toluidino)-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-(o-chloroanilino)fluoran, 
3-diethylamino-7-(m-trifluoromethylanilino)fluoran, 
3-diethylamino-6-methyl-7-chlorofluoran, 
3-diethylamino-6-methylfluoran, and 
3-cyclohexylamino-6-chlorofluoran. 
As a matter of course, the dyes for use in the present invention are not 
limited to the above examples. 
It is preferable that the phenolic materials of the formula (I) for use in 
the present invention be employed in an amount of 1 to 6 times the amount 
of the leuco dye. 
Specific examples of the phenolic materials of the formula (I) in which R 
is an alkylene group having 1 to 10 carbon atoms are as follows: 
______________________________________ 
Compound 
No. 
______________________________________ 
No. 1-1 
##STR4## 
No. 1-2 
##STR5## 
No. 1-3 
##STR6## 
No. 1-4 
##STR7## 
No. 1-5 
##STR8## 
No. 1-6 
##STR9## 
No. 1-7 
##STR10## 
No. 1-8 
##STR11## 
No. 1-9 
##STR12## 
______________________________________ 
Specific examples of the phenolic material of the formula (I) in which R is 
an alkylene group having 1 to 8 carbon atoms, with 1 to 3 carbonyl groups 
contained in the alkylene group, but not directly bonded to S, are as 
follows: 
______________________________________ 
Com- 
pound 
No. 
______________________________________ 
No. 2-1 
##STR13## 
No. 2-2 
##STR14## 
No. 2-3 
##STR15## 
No. 2-4 
##STR16## 
No. 2-5 
##STR17## 
______________________________________ 
Specific examples of the phenolic compounds of the formula (I) in which R 
is an alkylene group having 2 to 15 carbon atoms, with 1 to 5 ether bonds 
contained in the alkylene group, are as follows: 
__________________________________________________________________________ 
Compound No. 
__________________________________________________________________________ 
No. 3-1 
##STR18## 
No. 3-2 
##STR19## 
No. 3-3 
##STR20## 
No. 3-4 
##STR21## 
No. 3-5 
##STR22## 
No. 3-6 
##STR23## 
No. 3-7 
##STR24## 
No. 3-8 
##STR25## 
No. 3-9 
##STR26## 
__________________________________________________________________________ 
In the above phenolic compounds, the ether bonds can be contained in the 
main chain of the alkylene group or can be bonded to the side chain of the 
alkylene group. As indicated above, the number of carbon atoms contained 
in the alkylene group is usually 2 to 15 for use in the present invention. 
It is more preferable that the number of carbon atoms in the alkylene 
group be 2 to 7 and the alkylene group have 1 to 3 ether bonds. 
As mentioned previously, the phenolic compounds of the general formula (I) 
can be prepared without difficulty. For example, the compound No. 3-2 and 
the compound No. 3-6 were respectively prepared as follows: 
(1) Preparation of Compound No. 3-2 of the formula of 
##STR27## 
6.4 g of sodium hydroxide was dissolved in 22 g of methanol. To this 
solution, 20.2 g of p-hydroxybenzenethiol was added. Further, 10.4 g of 
bis(2-chloroethyl)ether was added dropwise to this mixture at room 
temperature. 
After addition of the bis(2-chloroethyl)ether, the reaction mixture was 
cooled and freed of methanol under reduced pressure. To the residue was 
added 300 ml of water. Crystals were separated, which were filtered off, 
sufficiently washed with water and dried. 
The thus obtained crystals were recrystallized from a mixed solvent of 
toluene and ethyl acetate, so that 15.5 g of 
1,5-di(4-hydroxyphenylthio)-3-oxapentane was obtained in the form of white 
crystals (m.p. 93.degree.-94.degree. C.). 
The results of elemental analysis of the product, 
1,5-di(4-hydroxyphenylthio)-3-oxapentane, were as follows: 
______________________________________ 
% C % H % S 
______________________________________ 
Found 59.81 5.78 19.77 
Calculated 59.60 5.63 19.89 
______________________________________ 
(2) Preparation of Compound No. 3-6 of the formula 
##STR28## 
6.4 g of sodium hydroxide was dissolved in 22 g of methanol. To this 
solution, 20.2 g of p-hydroxybenzenethiol was added. Further, 12.6 g of 
bis(2-chloroethoxy)methane was added dropwise to this mixture at room 
temperature. 
After addition of the bis(2-chloroethoxy)methane, the reaction mixture was 
refluxed at a methanol-refluxing temperature for 2 hours. The reaction 
mixture was then cooled and freed of methanol under reduced pressure. 
To the residue was added 500 ml of water. Crystals separated, which were 
filtered off, sufficiently washed with water and dried. 
The thus obtained crystals were recrystallized from a mixed solvent of 
toluene and ethyl acetate, so that 17.2 g of 
1,7-di(4-hydroxyphenylthio)-3,5-dioxaheptane was obtained in the form of 
white crystals (m.p. 108.degree.-109.degree. C.). 
The results of elemental analysis of the product, 
1,7-di(4-hydroxyphenylthio)-3,5-dioxyheptane were as follows: 
______________________________________ 
% C % H % S 
______________________________________ 
Found 58.08 5.75 18.14 
Calculated 57.93 5.72 18.19 
______________________________________ 
When the phenolic materials of the formula (I) in which R is an alkylene 
group having 2 to 15 carbon atoms, with 1 to 5 ether bonds contained in 
the alkylene group, are employed in combination with the particular 
fluoran compounds of the following formula, the developed images are 
particularly stable against plasticizers and do not discolor when they are 
brought into contact with a film containing a plasticizer, for instance, a 
polyvinyl chloride film. 
##STR29## 
wherein R.sup.1 and R.sup.2 each represent an alkyl group having 1 to 6 
carbon atoms or a cyclohexyl group; R.sup.3 represents an alkyl group 
having 1 to 2 carbon atoms; and n is an integer of 0 or 1. 
Specific examples of the fluoran compounds of the above formula are as 
follows: 
3-diethylamino-6-methyl-7-anilinofluoran, 
3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 
3-(N-methyl-N-n-hexylamino)-6-methyl-7-anilinofluoran, and 
3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran. 
The above fluoran compounds can be used alone or in combination. 
In the thermosensitive coloring layer of a thermosensitive recording 
material according to the present invention, the following binder agents 
can be employed: Water-soluble organic polymers such as polyvinyl alcohol, 
methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, 
polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid, starch and 
gelatin; and water emulsions of polystyrene, copolymer of vinyl chloride 
and vinyl acetate, and polybutyl methacrylate. 
Furthermore, in the thermosensitive coloring layer, the following additives 
can be contained in the form of fine powder to obtain clear images and to 
prevent formation of dusts which may accumulate on a thermal head when a 
thermal printer with a thermal head is employed for recording: Calcium 
carbonate, silica, alumina, magnesia, talc, titania, barium sulfate and 
aluminum stearate. 
Embodiments of the thermosensitive recording material according to the 
present invention will now be explained by referring to the following 
examples.

EXAMPLE 1 
A dispersion A-1, a dispersion B-1 and a dispersion C-1 were separately 
prepared by grinding and dispersing the following respective components in 
a ceramic bowl for 2 days: 
______________________________________ 
Parts by Weight 
______________________________________ 
Dispersion A-1 
3-(N--cyclohexyl-N--methylamino)- 
20 
6-methyl-7-anilinofluoran 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
Dispersion B-1 
1,3-di(4-hydroxyphenylthio)propane 
20 
(Compound No. 1-5, m.p. 81-83.degree. C.) 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
Dispersion C-1 
Calcium carbonate 20 
5% aqueous solution of methyl cellulose 
20 
Water 60 
______________________________________ 
10 parts by weight of the dispersion A-1, 30 parts by weight of the 
dispersion B-1, 30 parts by weight of the dispersion C-1 and 10 parts by 
weight of a 20% aqueous solution of polyvinyl alcohol were mixed to 
prepare a thermosensitive coloring layer formation liquid. This 
thermosensitive coloring layer formation liquid was applied to the surface 
of a sheet of commercially available high quality paper (50 g/m.sup.2) by 
a wire bar and was then dried, whereby a thermosensitive coloring layer 
was formed thereon. The deposition of the thermosensitive coloring layer 
on the sheet was in the range of 4 to 5 g/m.sup.2 when dried. The thus 
prepared thermosensitive recording material was subjected to calendering, 
so that surface of the thermosensitive coloring layer was made smooth to 
the degree ranging from 500 to 600 sec in terms of Bekk's smoothness, 
whereby a thermosensitive recording material No. 1 according to the 
present invention was prepared. 
EXAMPLE 2 
Example 1 was repeated except that the dispersion B-1 employed in Example 1 
was replaced by a dispersion B-2 with the following formulation, whereby a 
thermosensitive recording material No. 2 according to the present 
invention was prepared. 
______________________________________ 
Dispersion B-2 Parts by Weight 
______________________________________ 
1,5-di(4-hydroxyphenylthio)pentane 
20 
(Compound No. 1-6, m.p. 98-99.degree. C.) 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
______________________________________ 
EXAMPLE 3 
Example 1 was repeated except that the dispersion B-1 employed in Example 1 
was replaced by a dispersion B-3 with the following formulation, whereby a 
thermosensitive recording material No. 3 according to the present 
invention was prepared. 
______________________________________ 
Dispersion B-3 Parts by Weight 
______________________________________ 
1,3-di(4-hydroxyphenylthio)acetone 
20 
(Compound No. 2-1, m.p. 74-75.degree. C.) 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
______________________________________ 
EXAMPLE 4 
Example 1 was repeated except that the dispersion B-1 employed in Example 1 
was replaced by a dispersion B-4 with the following formulation, whereby a 
thermosensitive recording material No. 4 according to the present 
invention was prepared. 
______________________________________ 
Dispersion B-4 Parts by Weight 
______________________________________ 
1,7-di(4-hydroxyphenylthio)-hepta- 
20 
3,5-dione (Compound No. 2-5) 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
______________________________________ 
COMATIVE EXAMPLE 1 
Example 1 was repeated except that the dispersion B-1 employed in Example 1 
was replaced by a dispersion CB-1 with the following formulation, whereby 
a comparative thermosensitive recording material No. 1 was prepared. 
______________________________________ 
Dispersion CB-1 Parts by Weight 
______________________________________ 
Bisphenol A 20 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
______________________________________ 
COMATIVE EXAMPLE 2 
Example 1 was repeated except that the dispersion B-1 employed in Example 1 
was replaced by a dispersion CB-2 with the following formulation, whereby 
a comparative thermosensitive recording material No. 2 was prepared. 
______________________________________ 
Dispersion CB-2 Parts by Weight 
______________________________________ 
Benzyl p-hydroxybenzoate 
20 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
______________________________________ 
The thus prepared thermosensitive recording materials No. 1 through 4 
according to the present invention and the comparative thermosensitive 
recording materials No. 1 and No. 2 were subjected to thermal printing by 
a G-III facsimile apparatus (made by Ricoh Company, Ltd.) at a printing 
speed of 0.94 m/sec, with the voltage applied thereto changed to 3 steps 
of 16 V, 18 V and 20 V. The density of the developed images were measured 
by Macbeth densitometer RD-514. The results are shown in Table 1. 
TABLE 1 
______________________________________ 
Developed 
Thermosensitive 
Image Density 
Back- 
Recording (0.94 m/sec) ground 
Material 16 V 18 V 20 V Density 
______________________________________ 
Example 1 
No. 1 1.30 1.33 1.33 0.14 
Example 2 
No. 2 1.09 1.31 1.34 0.10 
Example 3 
No. 3 1.24 1.27 1.28 0.10 
Example 4 
No. 4 1.23 1.25 1.26 0.09 
Comparative 
No. 1 0.31 0.43 0.86 0.10 
Example 1 
Comparative 
No. 2 0.56 1.04 1.26 0.09 
Example 2 
______________________________________ 
The thermosensitive recording materials with images printed under the 
conditions of the printing speed being 0.94 m/sec and the applied voltage 
being 20 V were allowed to stand at room temperature for one week and the 
image densities were measured again by the Macbeth densitometer RD-514 and 
they were visually checked whether or not crystals of the phenolic 
material were separated on the surface of the recording materials. The 
results are shown in Table 2. 
TABLE 2 
______________________________________ 
Thermosensitive Separation of 
Recording Image Density 
Phenolic 
Material after 1 week 
Material 
______________________________________ 
Example 1 
No. 1 1.33 None 
Example 2 
No. 2 1.33 None 
Example 3 
No. 3 1.27 None 
Example 4 
No. 4 1.25 None 
Comparative 
No. 1 0.84 None 
Example 1 
Comparative 
No. 2 0.97 Observed 
Example 2 
______________________________________ 
As can be seen from the results shown in Table 1 and Table 2, the 
thermosensitive recording materials according to the present invention are 
excellent in development performance in high-speed recording and provided 
stabler images as compared with the comparative thermosensitive recording 
material examples. 
EXAMPLE 5 
A dispersion A-1, a dispersion B-5 and a dispersion C-1 were separately 
prepared by grinding and dispersing the following respective components in 
a ceramic bowl for 2 days: 
______________________________________ 
Parts by Weight 
______________________________________ 
Dispersion A-1 
(the same as that employed in Example 1) 
3-(N--cyclohexyl-N--methylamino)- 
20 
6-methyl-7-anilinofluoran 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
Dispersion B-5 
1,5-di(4-hydroxyphenylthio)-3-oxa-pentane 
20 
(Compound No. 3-2, m.p. 93-94.degree. C.) 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
Dispersion C-1 
(the same as that employed in Example 1) 
Calcium carbonate 20 
5% aqueous solution of methyl cellulose 
20 
Water 60 
______________________________________ 
10 parts by weight of the dispersion A-1, 30 parts by weight of the 
dispersion B-5, 30 parts by weight of the dispersion C-1 and 10 parts by 
weight of a 20% alkali aqueous solution of an isobutylene-maleic anhydride 
copolymer were mixed to prepare a thermosensitive coloring layer formation 
liquid. 
This thermosensitive coloring layer formation liquid was applied to the 
surface of a sheet of commercially available high quality paper (50 
g/m.sup.2) by a wire bar and was then dried, whereby a thermosensitive 
layer was formed thereon. The deposition of the thermosensitive layer on 
the sheet was in the range of 4 to 5 g/m.sup.2 when dried. The thus 
prepared thermosensitive recording material was subjected to calendering, 
so that surface of the thermosensitive layer was made smooth to the degree 
ranging from 500 to 600 sec in terms of Bekk's smoothness, whereby a 
thermosensitive recording material No. 5 according to the present 
invention was prepared. 
EXAMPLE 6 
Example 5 was repeated except that the dispersion B-5 employed in Example 5 
was replaced by a dispersion B-6 with the following formulation, whereby a 
thermosensitive recording material No. 6 according to the present 
invention was prepared. 
______________________________________ 
Dispersion B-6 Parts by Weight 
______________________________________ 
1,8-di(4-hydroxyphenylthio)-3,6-dioxa- 
20 
octane (Compound No. 3-6, m.p. 100-101.degree. C.) 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
______________________________________ 
The thus prepared thermosensitive recording materials No. 5 and 6 according 
to the present invention were subjected to thermal printing by a G-III 
facsimile apparatus (made by Ricoh Company, Ltd.) at a printing speed of 
0.94 m/sec, with the voltage applied thereto changed to 3 steps of 16 V, 
18 V and 20 V. The density of each developed image was measured by Macbeth 
densitometer RD-514. The results are shown in Table 3. 
TABLE 3 
______________________________________ 
Developed 
Thermosensitive 
Image Density 
Back- 
Recording (0.94 m/sec) ground 
Material 16 V 18 V 20 V Density 
______________________________________ 
Example 5 
No. 5 1.18 1.30 1.31 0.11 
Example 6 
No. 6 0.71 1.19 1.27 0.08 
Comparative 
No. 1 0.31 0.43 0.86 0.10 
Example 1 
Comparative 
No. 2 0.56 1.04 1.26 0.09 
Example 2 
______________________________________ 
The thermosensitive recording materials with images printed under the 
conditions of the printing speed being 0.94 m/sec and the applied voltage 
being 20 V were allowed to stand at room temperature for one week and the 
image densities were measured again by the Macbeth densitometer RD-514 and 
they were visually checked whether or not crystals of the phenolic 
material were separated on the surface of the recording materials. The 
results are shown in Table 4. 
TABLE 4 
______________________________________ 
Thermosensitive Separation of 
Recording Image Density 
Phenolic 
Material after 1 week 
Material 
______________________________________ 
Example 5 
No. 5 1.30 None 
Example 6 
No. 6 1.20 None 
Comparative 
No. 1 0.84 None 
Example 1 
Comparative 
No. 2 0.97 Observed 
Example 2 
______________________________________ 
As can be seen from the results shown in Table 3 and Table 4, the 
thermosensitive recording materials according to the present invention are 
excellent in development performance in high-speed recording and provided 
stabler images as compared with the comparative thermosensitive recording 
materials. 
EXAMPLE 7 
Example 5 was repeated except that the dispersion A-1 employed in Example 5 
was replaced by a dispersion A-2 with the following formulation, whereby a 
thermosensitive recording material No. 7 according to the present 
invention was prepared. 
______________________________________ 
Dispersion A-2 Parts by Weight 
______________________________________ 
3-(N--ethyl-N--isoamylamino)-6-methyl-7- 
20 
anilinofluoran 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
______________________________________ 
EXAMPLE 8 
Example 5 was repeated except that the dispersion A-1 employed in Example 5 
was replaced by a dispersion A-3 with the following formulation, whereby a 
thermosensitive recording material No. 8 according to the present 
invention was prepared. 
______________________________________ 
Dispersion A-3 Parts by Weight 
______________________________________ 
3-diethylamino-6-methyl-7- 
20 
anilinofluoran 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
______________________________________ 
EXAMPLE 9 
Example 5 was repeated except that the dispersion A-1 employed in Example 5 
was replaced by a dispersion A-4 with the following formulation, whereby a 
thermosensitive recording material No. 9 according to the present 
invention was prepared. 
______________________________________ 
Dispersion A-4 Parts by Weight 
______________________________________ 
3-di-n-butylamino-7-(o-chloroanilino) 
20 
fluoran 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
______________________________________ 
EXAMPLE 10 
Example 5 was repeated except that the dispersion A-1 employed in Example 5 
was replaced by a dispersion A-5 with the following formulation, whereby a 
thermosensitive recording material No. 10 according to the present 
invention was prepared. 
______________________________________ 
Dispersion A-5 Parts by Weight 
______________________________________ 
3-(N--ethyl-N--p-toluidino)-6-methyl- 
20 
7-anilinofluoran 
10% aqueous solution of hydroxyethyl 
20 
cellulose 
Water 60 
______________________________________ 
The thus prepared thermosensitive recording materials No. 7 through 10 
according to the present invention were subjected to thermal printing by 
the G-III facsimile apparatus and to the preservability tests in the same 
manner as in Example 5. The results were as good as in Example 5. 
Further, the thermosensitive recording materials No. 5 and No. 7 through 
No. 10 were subjected to thermal printing by a gradient test apparatus 
(made by Toyo Seiki Co., Ltd.) at 150.degree. C. with a pressure of 2 
kg/cm.sup.2 applied to each thermosensitive recording material for 1 
second. From each thermosensitive recording material, a portion of 4 
cm.sup.2 including a printed area was cut off and was then covered with a 
polyvinyl chloride wrapping film (Trade Name: Polyma-wrap V-300 made by 
Shin-Etsu Polymer Company, Ltd.), with a pressure of 500 g/cm.sup.2 
applied thereto for 5 hours. 
Changes in image density of the printed images in each thermosensitive 
recording material were measured by a Macbeth densitometer RD-514. 
The results of that measurement are shown in Table 5. 
TABLE 5 
______________________________________ 
Thermo- Back- 
sensitive Wrapping Film Contact Test 
ground 
Recording Initial Image 
Image Density 
Den- 
Material Density after 5 hours 
sity 
______________________________________ 
Example 5 
No. 5 1.35 1.08 0.11 
Example 7 
No. 7 1.32 0.91 0.12 
Example 8 
No. 8 1.35 1.02 0.11 
Example 9 
No. 9 1.28 0.11 0.08 
Example 10 
No. 10 1.36 0.09 0.08 
______________________________________ 
As can be seen from the results shown in Table 5, the printed image areas 
of the thermosensitive recording materials No. 5, No. 7 and No. 8 
according to the present invention were more resistant to discoloration 
which may be caused by contact with the polyvinyl chloride wrapping film, 
as compared with the thermosensitive recording materials No. 9 and No. 10. 
The above results indicates that when the phenolic materials of the formula 
(I) in which R is an alkylene group having 2 to 15 carbon atoms, with 1 to 
5 ether bonds contained in the alkylene group, were employed in 
combination with the particular fluoran compounds of the previously 
described formula (II), the developed images were stabler against the 
polyvinyl chloride film and discolored significantly less when they were 
brought into contact with the film, as compared with the thermosensitive 
recording materials in which the above phenolic materials and fluoran 
compounds other than the above particular fluoran compounds were employed 
in combination. 
In any case, according to the present invention, by use of any of the 
phenolic materials for use in the present invention, a thermosensitive 
recording material with the following advantages over the conventional 
thermosensitive recording materials can be obtained: 
(1) High thermal sensitivity (i.e. high thermal response) is obtained, 
without using any sensitizers or melting-point reducing agent. Due to the 
high thermal response, images can be recorded with high density and 
clearness in high speed recording, even if image information to be 
recorded is dense per unit area. 
(2) Printed images do not substantially discolor with time. In other words, 
the quality of printed images is extremely stable, and no components 
contained in the thermosensitive recording material separate out in the 
form of crystals on the surface thereof during storage. 
(3) No components come out from the thermosensitive recording material and 
accumulate on or adhere to a thermal head during thermal printing by use 
of a thermal printer with a thermal head. 
(4) By applying a thermosensitive coloring layer formation liquid prepared 
in accordance with the present invention to a sheet of thin base paper or 
to a film, an excellent thermosensitive copy sheet for use with an 
infrared lamp or a strobo flash can be prepared. 
(5) Since the coating amount of the thermosensitive coloring layer 
formation liquid can be reduced, in comparison with the conventional 
thermosensitive recording materials, the manufacturing efficiency of the 
thermosensitive recording materials according to the present invention can 
be significantly increased as compared with the manufacturing efficiency 
of the conventional thermosensitive recording materials. 
(6) The phenolic materials employed in the present invention as the color 
developer can be synthesized with higher yield and higher purity and at a 
comparatively lower cost, as compared with the conventional color 
developers. 
The thermosensitive recording materials according to the present invention 
can be employed in a variety of fields, for example, as 
thermosensitive-recording-type label sheets or as 
thermosensitive-recording-type magnetic tickets, by utilizing the 
characteristic image stability. 
In the case of a thermosensitive recording label sheet, a thermosensitive 
recording layer comprising any of the above described fluoran compounds 
and the phenolic materials is formed on one side of a support material, 
and to the other side of the support material, a disposable sheet is 
attached through an adhesive layer. 
In the case of a thermosensitive-recording-type magnetic ticket, the 
disposable sheet in the label sheet is replaced by a magnetic recording 
layer comprising as the main components a ferromagnetic material and a 
binder agent.