Source: https://patents.justia.com/patent/4399188
Timestamp: 2020-03-28 15:52:21
Document Index: 201118678

Matched Legal Cases: ['arts\n36', 'arts\n9', 'arts  8', 'arts\n4', 'arts\n4', 'art\n4']

US Patent for Heat-sensitive recording sheet Patent (Patent # 4,399,188 issued August 16, 1983) - Justia Patents Search
Justia Patents US Patent for Heat-sensitive recording sheet Patent (Patent # 4,399,188)
Jun 29, 1981 - Jujo Paper Co., Ltd.
A heat-sensitive recording sheet containing in its color-forming layer a colorless or pale colored chromogenic fluoran-type dyestuff and p-hydroxybenzoic acid ester having the following general formula ##STR1## wherein R represents ##STR2## This heat-sensitive recording sheet incorporates high image density and very preferable recording aptitude with less abrasiveness and less residues accumulated even for long time recording.Furthermore, a phenol substance having a melting point of more than 90.degree. C. and a solubility of less than 0.1 g per 100 g water, which is used together with said p-hydroxybenzoic acid ester, is useful for lowering the yellowing of the heat-sensitive sheet.
Latest Jujo Paper Co., Ltd. Patents:
Transparent recording medium
Light-responsive plate containing the metal salt of a phthalic acid derivative
In printers, e.g. a dot matrix of 5.times.7 array is previously sufficient to express the alphabet and numerals, but a dot matrix of 16.times.18 array or 32.times.32 array is now required for the exact expression of Chinese characters.
Facsimile equipment requires, nowadays, less than one minute for recording a sheet of A4-size (210 mm.times.297 mm), although, previously, several minutes for recording was required.
Therefore, a colorless dyestuff or an acidic material, such as organic acids and phenols, in the color-forming layer must be melted with minimized heat energy to cause the color-forming reaction. If possible, it is desirable to cause the color-forming at a temperature of 70.degree. C. to 120.degree. C.
The colorless chromogenic dyestuffs for thermal recording sheets which have the structure of lactones, lactams, spiropyrans etc. possess usually a melting point of 160.degree. C. to 240.degree. C., but there are no stable dyestuffs that are melted at the aforementioned low temperature.
On the other hand, there are many color-developing agents, such as organic acids and phenolic substances, which were used in combination with a colorless chromogenic dyestuff and which were disclosed in the Japanese Patent Publication No. 14039/1970 and various literatures. Particularly, 4,4'-isopropylidendiphenol (bisphenol A, having a melting point: 156.degree. C. to 158.degree. C.) is a useful, desirable phenolic substance and is now widely put into practical use, since it is stable, inexpensive and readily available. But 4,4'-isopropylidendiphenol has as its disadvantage a high heat color-forming temperature.
Then, phenolic substances of low melting point, for example, monomeric phenols such as 4-tertiary-butylphenol (m.p. 94.degree.-99.degree. C.), .alpha.-naphthol (m.p. 95.degree.-96.degree. C.), .beta.-naphthol (m.p. 119.degree.-122.degree. C.) etc., deteriorate preservability and stability of a heat-sensitive recording sheet, which is gradually colored at room temperature and has a phenolic odor. Therefore, such phenolic substances are not acceptable for practical use. The Japanese Patent Publication No. 12819/1979 discloses that p,p'-(1-methyl-normalhexylidene-) diphenol has a low melting point (m.p. 99.degree.-103.degree. C.) and gives a heat-sensitive recording paper with excellent stability and color-forming property, but there is a shortcoming that such substance has difficulty in synthesis and is not readily available.
It is the sixth object of the present invention to provide a heat-sensitive recording sheet which has various sensitivities by the choice of p-hydroxybenzoic acid esters (m.p. approximately 60.degree.-120.degree. C.) used in the present invention.
It is the seventh object of the present invention to provide a heat-sensitive recording sheet which has excellent yellow-resistance by using a phenol with a melting point of more than 90.degree. C. and a solubility of less than 0.1 g per 100 g water together with the p-hydroxybenzoic acid ester.
Compound       --R             point
95-98.degree. C.
iso C.sub.3 H.sub.7
84-85.degree. C.
--C.sub.4 H.sub.9
69-72.degree. C.
iso C.sub.4 H.sub.9
--CH.sub.2 --C.sub.6 H.sub.5
108-113.degree. C.
--CH.sub.2 --C.sub.6 H.sub.4 --m-CH.sub.3
methylbenzyl ester
As the substances having a similar structure to the above-mentioned compounds of the present invention, the Japanese Patent Publication No. 14039/1970 discloses methyl-4-hydroxybenzoate having a melting point of 125.degree.-128.degree. C., and the Japanese Patent Publication No. 35095/1979 discloses phenyl-4-hydroxybenzoate having a melting point of 150.degree.-158.degree. C.
The phenolic substance as yellowing-resistance agent, which is used together with p-hydroxybenzoic acid ester, includes phenols which have a melting point of more than 90.degree. C. and a solubility of less than 0.1 g per 100 g water, and do not have a color forming ability in the presence of the colorless or pale colored fluoran-type dyestuff.
Phenols with a melting point of less than 90.degree. C. are not suitable for practical use, since they are sublimable and unstable in other properties and they lower production efficiency due to a required dryer-temperature of less than 90.degree. C. after their coating.
It is desirable that phenols having a melting point of more than 90.degree. C. and a solubility of less than 0.1 g per 100 g water have a specific gravity of 0.9-1.15, taking an appropriate coating into consideration. Phenols with a specific gravity of more than 1.15 precipitate in coating colors even when they are ground to fine particles in aqueous solution. On the other hand, phenols with a specific gravity of less than 0.9 float on the surface of coating colores. Examples of the phenolic substance as yellowing-resistance agent includes 4,4'-butylidene-bis(3-methyl-6-tertiary-butylphenol), 2,2'-methylene-bis(4-ethyl-6-tertiary-butylphenol), 2,5-di-tertiary-butylhydroquinone, 2,5-di-tertiary-amylhydroquinone, 1,1'-bis(4-hydroxyphenyl)-cyclohexane, 2,6-bis(2'-hydroxy-3'-tertiary-butyl-5-methylbenzyl)-4-methylphenol, 2,2'-methylene-bis(4-ethyl-6-tertiary-butylphenol), 2,2'-iso-butylidene-bis(4,6-di-methylphenol), 1'-oxy-3-methyl-4-iso-propylbenzene, 2-hydroxy-4-benzyloxy-benzophenone, bis-[3,3'-bis-(4'-hydroxy-3'-tertiary-butylphenol)-butyric acid] glycol ester, bis(3-methyl-4-hydroxy-5-tertiary-butyl-benzyl) sulfide, 2,2'-methylene-bis(4-methyl-6-cyclohexyl-phenol) and hydroquinone-mono-benzyl ether.
Solution A (dispersion of dyestuff)
water                      2.5 parts
Solution B (dispersion of color-developing agent)
color-developing agent *(see Table 2)
zinc stearate              0.5 parts
*As colordeveloping agent, there were used bisphenol A and phydroxybenzoi
9.1     parts
36.5    parts
Kaolin clay (50% aqueous dispersion)
12      parts
The coating colors were applied on one side of the base paper weighing 50 g/m.sup.2 at a coating weight of 6.0 g/m.sup.2, and were then dried.
Color       Background (1)
developing         After a
agent       Immediately
C.sub.2 H.sub.5 as R
0.05   0.05
1.15 No trouble
C.sub.3 H.sub.7 as R
1.13 No trouble
iso C.sub.3 H.sub.7 as R
0.09        1.08   1.15
nC.sub.4 H.sub.9 as R
0.07        1.20   1.15
iso C.sub.4 H.sub.9 as R
0.07        1.18   1.15
CH.sub.2C.sub.6 H.sub.5 as R
1.20 No trouble
##STR6##   0.05   0.06
Bisphenol A 0.08   0.12
0.81 White spots in image
example                                 Noise in recording
CH.sub.3 as R
0.06   0.07
1.00 No white spots in
image but noise in
C.sub.6 H.sub.5 as R
0.76 White spots in image
(1) Optical density of background was measured by a Macbeth densitometer
RD514 (lower optical density shows higher brightness).
(2) The heatsensitive recording sheets were pressed down for 5 seconds
under pressure of 10 g/cm.sup.2 on a hot plate heated at 105.degree. C.
and optical density of statically developed image was measured by a
Macbeth densitometer RD514 (higher optical density shows darker color).
(3) The heatsensitive recording sheets were recorded in a pulse width of
3.0 milliseconds and an impressed voltage of 18.0 volt by using the
thermal facsimile KB4800 manufactured by TOSHIBA CORPORATION and optical
density of recorded image was measured by a Macbeth densitometer RD104.
(4) Allmark print was recorded by using a thermal facsimile KB500
manufactured by TOSHIBA CORPORATION, then recording aptitude sticking,
noise etc. and quality of recorded image are checked.
10% aqueous solution of hydroxyethylcellulose
water                       2.5 parts
Solution B(1) (Dispersion of color-developing agent)
zinc stearate               0.5 parts
Solution B(2) (Dispersion of color-developing agent)
bisphenol A                 6.0 parts
stearic acid amide          3.0 parts
Solution A    9.1   parts
9.1   parts
Solution B    (1) 36.5
(2) 49.0
Coating      Calcined kaolin
10    parts
color        (50% aqueous dis-
Coating weight     5.0     g/m.sup.2
5.8   g/m.sup.2
Storage          (2)
at high  Static  Dynamic
Imme-       tempera- image   image
diately     ture     density density
0.05    0.07     1.30  0.90   No trouble
0.08    0.14     1.35  0.28   White spots
example 2                             in image.
(1) The heatsensitive recording sheets were treated for 24 hours under
40.degree. C. and 90% R.H., and the optical density of background was
measured by a Macbeth densitometer RD104.
(2) The heatsensitive recording sheets were recroded by using a thermal
facsimile (FRH type) manufactured by "Matsushita Graphic Communication
Systems, Inc., with a pulse width of 1.0 millisec. and an impressed
voltage of 17.66V, and the recorded image density was measured by a
Macbeth densitometer RD104.
3-diethylamino-6-methyl-7-(o,p-dimethylanilino)
10% aqueous solution of hydroxyethyl cellulose
stearic acid amide          5.0 parts
Each solution of the above-mentioned composition was individually ground to a particle size of 2 microns by means of a sand grinder, and the dispersions were mixed in the hereinaftermentioned proportion to prepare heat-sensitive coating colors. The resultant coating colors were applied on a tissue paper weighing 30 g/m.sup.2. Thereafter, heat-sensitive recording sheets were prepared by treating as in Example 1.
Coating      Solution A
8.9   parts  8.9   parts
parts  (2) 41
Coating weight 4.0     g/m.sup.2
Static   Copied
image    image
density  density
Example 3      0.07        1.20     0.95
0.13        1.30     0.40
zinc stearate               0.5 part
Solution C (dispersion of yellowing-resistance agent)
yellowing-resistance agent (see Tables 5 and 6)
4(b) to 4(g) and
4(i) to 4(n)
Ex. 4(a) and 4(h)
Solution A    9.1 parts
Solution B(1) or
Coating      B(2)
color        Solution C    5.0 parts
Kaolin clay    12 parts
(50% aqueous
Yellowing-resistance
Solubility Melting   Specific
agent         in water   point     gravity
2,5-di-tertiary-
2,5-di-tertiary-amyl-
4,4'-butylidene-bis(3-
209.degree. C.
methyl-6-tertiary-
4,4'-methylene-bis(2,6-di-
tertiary-butylphenol)
2,2'-methylene-bis(4-
119-125.degree. C.
ethyl-6-tertiary-
118.degree. C.
Phenolic substance as
Yellowing-
agent    agent         ground
--          0.06
amylhydroquinone
4,4'-methylene-bis(2,6-
di-tertiary-butylphenol)
2,2'-methylene-bis(4-methyl-
6-cyclohexylphenol)
4,4'-butylidene-bis(3-methyl-
6-tertiary-butylphenol)
2,2' -methylene-bis(4-ethyl-
(1) Background: Optical density of background was measured by a Macbeth
densitometer RD104 (using amber filter)
(2) Image density: The heatsensitive recording sheets were recorded in a
pulse width of 3.2 milliseconds and an impressed voltage of 18.0 volts by
using the thermal facsimile KB4800 manufactured by TOSHIBA CORPORATION an
optical density of recorded image was measured by a Macbeth densitometer
RD104.
(3) Yellowingresistance: The heatsensitive recording sheets were stored i
room for a month and white portions on the sheets were measured by a
Macbeth densitometer RD104 (using blue filter).
Solution A(1) (dispersion of dyestuff)
3-(N--cyclohexyl-N--methylamino)-6-methyl-7-
1.2   parts
4.6   parts
water                       2.5   parts
Solution A(2)
crystal violet lactone      1.2   parts
p-phenylphenol              5     parts
4,4'-butylidene-bis (3-methyl-6-tertiary-
1.0   part
4.0   parts
Example  Example
5(a)   5(b)     5
Solution A(1)
0      0     8.3 parts
Solution B   31.0 parts
Coating      Solution C    5.0 parts
colors       Aluminium hy-
droxide (50% a-
queous dispersion)
Coating weight     6.0 g/m.sup.2
6.0 g/m.sup.2
Back-          one month   Yellowing-
later       resistance
0.06    1.24       1.22    0.07
0.07    1.22       1.20    0.12
0.06    1.22       0.20    0.10
3871900 March 1975 Hayashi et al.
4168845 September 25, 1979 Oeda et al.
50-16969 June 1975 JPX
Patent number: 4399188
Assignee: Jujo Paper Co., Ltd. (Tokyo)
Inventors: Noboru Yamato (Tokyo), Tosimi Satake (Tokyo)
Application Number: 6/278,747
Current U.S. Class: 428/3204; 282/275; 428/211; 428/488; 428/537; Material Designed To Be Responsive To Temperature, Light, Moisture, Etc. (428/913)