|Publication number||US3846153 A|
|Publication date||Nov 5, 1974|
|Filing date||Jul 24, 1972|
|Priority date||Aug 5, 1971|
|Also published as||DE2237288A1, DE2237288B2, DE2237288C3|
|Publication number||US 3846153 A, US 3846153A, US-A-3846153, US3846153 A, US3846153A|
|Inventors||Futaki K, Haino K, Kohmura I|
|Original Assignee||Mitsubishi Paper Mills Ltd|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (10), Classifications (10)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Nov. 5, 1974 yos FUTAKl E'I'AL 3,846,153
' HEAT SENSITIVE COMPOSITION AND THERMAL RECORDING SHEET CONTAINING THE SMIE Filed July 2 1972 DE/VS/T) 0F GRCUND COLOR (40 6' AF 727?? ONE WEEK Q O 0.3 XI
1 l l l i l l l l l 1 I I l l 0 80 90 ,/00//0 /20 B0 /40 /50 COLOR FORM/N6 WERE ("6'1 United States Patent 3,846,153 HEAT SENSITIVE COMPOSITION AND THERMAL RECORDING SHEET CONTAINING THE SAME Kiyoshi Futaki, Isao Kohmura, and K020 Haino, Kyoto, Japan, assignors to Mitsubishi Paper Mills, Ltd., Tokyo, Japan Filed July 24, 1972, Ser. No. 274,618 Claims priority, application Japan, Aug. 5, 1971, 46/ 59,143 Int. Cl. B41m /18 US. Cl. 11736.9 5 Claims ABSTRACT OF THE DISCLOSURE In the heat sensitive composition and thermal recording sheet comprising combination of a color forming lactone compound and a phenol compound, the compound having the formula Il-OsHu is used as said phenol compound, whereby excellent preservability and stability of the composition is attained.
The present invention relates to a heat sensitive composition which comprises combination of an ordinarily colorless or light-colored color forming lactone compound and -a phenol compound. Furthermore, the present invention concerns a thermal recording sheet which contains said composition.
'0. Fischer and F. Rorner already reported in Berichte der Deutschen hemischen Gesellschaft (Vol. 42, pages 2934-2935, 1909) that a color forming lactone compound such as Crystal Violet Lactone reacts with phenols to form color and application of such reaction to thermal recording sheet is disclosed in Japanese Patent Publication No. 14,039/70. Besides said recording sheets, a great number of thermal recording sheets have been proposed. However, for industrial utilization thereof, the following requirements must be met; namely, (1) ground color of the sheet must be colorless or light color, (2) it must be stable for a long period of preservation at room temperature, (3) it must rapidly form deep color at a certain temperature, e.g., a temperature of 70 C.- 200 C., (4) the color formed must be clear and fully stable against light and moisture, (5) it must have no smell and toxicity and moreover -(6) it must be able to be economically produced. It is extremely difiicult to produce thermal recording sheet which satisfies all of the above requirements. The most difficult requirement is to improve preservability. This purpose may be attained by setting the color forming temperature of the heat sensitive composition at a high level, but in this case a large amount of heat is required for recording. Thus, a large amount of electric power is required for thermal pen or thermal printer and high speed recording becomes difiicult. Therefore, such method is practically disadvantageous. On the other hand, when color forming temperature is set at a low level, recording can be carried out with a small amount of electric power. In this case, however, the stability of the part of the sheet where no color is formed is lowered and the possibility of color-forming during preservation increases. Therefore, such thermal recording sheet as being highly stable at room temperature and having a color-forming temperature of as low as possible is desired, but it is very difiicult to produce a heat sensitive composition which simultaneously meets the above two requirements. Practically, the thermal recording sheet is often inadvertently placed near a heater or other heat sources and therefore, special care must be given in handl-ing of the thermal recording sheet which has too low color forming temperature. Therefore, a thermal recording sheet which rapidly forms color at a temperature of about -l00 C. and is highly stable at room temperature has been desired for practical use. To meet such requirements has been technically very difiicult. In this connection, the color forming temperature has a close relation with melting point of the compounds which constitute the heat sensitive composition. This fact will be explained with reference to the system comprising an ordinarily colorless or light-colored color forming lactone compound and a phenol. A color forming lactone compound and a phenol which are solid at room temperature are separately ground to a particle size of less than about several microns in solvents which do not dissolve them with use of e.g. a ball mill. Thereafter, they are mixed and the mixture is applied together with a binder to a paper and is dried to obtain a thermal recording sheet. In this case, when mono-phenols such as 4-tert.buty1 phenol (melting point: 9499 C.), u-naphthol (melting point: 9596 C.), B-naphthol (melting point: 119- 122 C.), etc. are used, the preservability and stability of the thermal recording sheet are low and not only it gradually forms color at room temperature, but it has the s-o-called phenol smell. Diphenols include compounds excellent for thermal recording sheet and when 4,4'-cyclohexylidene diphenol (melting point: C.) or 4,4- is'opropylidene diphenol (melting point: 156 C.) is used, such sheet as having clear thermal color formation and practically high stability can be obtained. However, in case of the former compound, the color forming temperature :is too high and in case of the latter compound, the color forming temperature is sometimes also too high. Therefore, the recording sheet having lower color forming temperature without damaging practical stability and preservability has been demanded.
The inventors have made extensive researches to succeed in obtaining heat sensitive composition which meets said requirements. That is, this heat sensitive composition comprises combination of at least one of ordinarily colorless or light-colored color forming lactone compounds, namely, Leuco Lactone dye and P,'P'-(l-rnethyl-normal hexylidene)diphenol having the following chemical formula,
The color forming lactone compounds used in the present invention mean the ordinarily colorless or light-colored lactone compounds capable of reacting with said phenol compound to form color. The representative examples of such lactone compounds are the following triphenylmethane l'actones, fluorans, benzofluorans, etc., but the present invention is not limited to use of only these compounds.
Crystal Violet lactone, Malachite Green lactone, 3,3-bis (paradimethyl aminophenyl)-6-aminophthalide, 3,3 bis (paradimethylaminophenyl) 6 (paratoluenesulfonamide)phthalide, 3 diethylamino-7-dibenzylamino-fluoran, 3-diethylamino 7 (N-methylanilino)-fiuoran, 3-diethyl amino 7 (N-methyl-p-toluidino)-fluoran, B-dimethylamino 6 methoxy-fluoran, 3-diethylamino-6-methyl-7- chloro-fiuoran, 3-dibutylarnino-6-methyl-7-chloro-fluoran, 3-diethylamino-7-phenylfluoran, 3-morpholino-5,6-benzofluoran.
A method for producing the phenol compound used in the present invention is disclosed in US. Pat. 2,535,014 (Dec. 19, 1950).
The general method for producing the thermal recording sheet of the present invention is as follows: The phenol compound as mentioned above and the ordinarily colorless or light-colored color forming lactone compound are separately ground together with a binder in a medium which does not dissolve said compounds by ball mill to obtain dispersion liquids. Then, these liquids are mixed. The mixture is applied to a substrate sheet and dried. Alternatively, each dispersion liquid is applied to a substrate sheet in order or one of them is contained in a substrate sheet and the other is applied to the substrate sheet. When the substrate sheet is paper, fine powders of both compounds may be incorporated into the paper at paper making step or one of them may be impregnated in paper as a solution and the other dispersion may be applied to the paper.
As the medium for the dispersion of the compounds, water or petroleums are suitable. As the binder, water soluble high polymer compounds such as polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, styrene, butadiene or acrylic latex may be employed in case of using water as the medium and terpene resins, cyclized rubber, etc. may be used in case of using petroleums as the medium.
Suitable amounts of the lactone compound, the phenol compound and the binder are 13()% by Weight, 45-94% by Weight and -40% by weight (these are dry weight percent), resepectively. If necessary, talc, waxes, surface active agents, defoaming agents etc. may be added to improve application state and recording state. Furthermore, a protective layer may be provided onto the heat sensitive layer to further improve the stability.
EXAMPLE 1 Liquid A G. Crystal Violet lactone 1 5% Aqueous solution of hydroxyethyl cellulose (HEC BL-lS manufactured by Fuji Chemical Co.) 5 Water 4.4
Liquid B P,P'-(lmethyl-normal hexylidene)diphenol 5 5% Aqueous solution of hydroxyethyl cellulose Water 22 Said liquids A and B were separately ground for 2 days in ball mill to produce two dispersion liquids. Then, the two were mixed and the mixed liquid was applied to an ordinary paper having a basis weight of 50 g./m. and dried. The amount of the applied liquid was about 3 g./m. expressed by dry weight. Thus obtained thermal recording sheet was stable at room temperature and the ground color of the applied layer was substantially white and rapidly formed blue color at about 90 C. When a letter was copied with heating, a clear recording of the letter was obtained.
For comparison, the following experiment was carried out. That is, in place of P,P'-(1-rnethyl-normal hexylidene) diphenol in said liquid B, similar compounds mentioned in the following Table 1 were used.
Properties of thus obtained thermal recording sheet are shown in Table 2 and FIG. 1.
TABLE 2 Density of Color ground color I forming Phenol temper- Density Color Immediately After 1 compounds ature of color forming after Week at used C.) formed 3 speed production 40 C 145 1 25 Rapid 0.06 0.07
135 1 03 Slow- 0. 02 O. 02
100 1. 12 Rapui 0. 28 0.51
0.78 Slow 0.02 0. 02
90 1.12 Barn 0. l4 0. 26
1 Tem erature of the part of the sheet at which color was formed in a high density when the sheet was allowed to contact with a metal plate having a temperature gradient.
2 The density was measured with the Macbeth densitometer (reflection density).
FIG. 1 shows the relation between color forming temperature at which color is formed in high density for a short period of time and density of ground color formed after lapse of one week at 40 C. of thermal recording sheets using various phenol compounds. In other words, it shows the relation between color forming temperature and stability (density of ground color after one Week at 40 C.). In this FIG. 1, white dot indicates that the color forming speed was high (i.e.: quick response) and black dot indicates that the color forming speed was low (i.e.: slow response).
As is clear from Table 2 and FIG. 1, the recording sheet containing the present phenol compound (X) formed color at the preferred temperature of relatively lower temperature as compared with the recording sheets containing compounds (I) and (II). In case of other phenol compounds (HI), (IV), (V), (VI), (VII), (VIII), (IX) and (XI), the sheets formed color at a preferred temperature of relatively low temperature, but had practically fatal defects. That is, in case of the compounds (111) and (VIII), when liquids A and B were mixed, the liquid severely formed color and hence the liquid when applied to sheet caused formation of deep ground color, which was not practically desired. Furthermore, in case of the compounds (IV), (V), (IX) and (X), formation of ground color immediately after production of recording sheet was not so severe, but with lapse of time (during preservation) the ground color was formed. In case of the compounds (II), (VI) and (VII), the sheet obtained had suitable color forming temperature and good preservability, but the color forming reaction on application of heat occurred slowly and the sheet was not suitable for high speed recording. On the other hand, the compound (X) of the present invention showed substantially no formation of ground color, had rapid color formation reaction and had excellent preservability.
5 EXAMPLE 2 Example 1 was repeated except that 3-dibutylamino-6- methyl-7-chlorofluoran was substituted for Crystal Violet lactone to obtain an excellent thermal recording sheet which formed red color with heat in substantially white ground.
EXAMPLE 3 Example 1 was repeated except that 3-diethylamino-7- (N-methyl-P-toluidino)fiuoran was substituted for Crystal Violet lactone to obtain an excellent thermal recording sheet which formed green color in substantially white ground.
What is claimed is:
1. A thermal recording sheet which contains the phenol compound having the formula:
at least one ordinarily colorless or light-colored lactone compound capable of reacting with said phenol compound upon heating to form a color, and a binder, the proportions of phenol compound, lactone compound and binder being 130% by weight of the lactone compound, 45- 94% by Weight of the phenol compound and 4-40% by weight of a binder, expressed by dry weight percentage.
2. A thermal recording sheet according to claim 1, having said lactone compound and phenol compound in admixture applied on a substrate sheet.
3. A thermal recording sheet according to claim 1, wherein said lactone compound and phenol compound are applied in separate layers on a substrate sheet.
4. A thermal recording sheet according to claim 1, wherein either one of the lactone compounds or the phenol compound is contained in a substrate sheet and the other is applied to said sheet.
5. A heat sensitive room temperature stable composition comprising the phenol compound having the formula:
and at least one ordinarily colorless or light colored lactone compound capable of reacting with said phenol compound upon heating to form a color, said composition comprising 1-30% by weight of the lactone compound,
15 4594% by weight of the phenol compound and 5-40% by weight of a binder expressed by dry Weight percentage.
References Cited 0 UNITED STATES PATENTS 3,539,375 11/1970 Baum 117-368 3,451,338 6/1969 Baum 11736.8 3,466,185 9/1969 Taylor l1736.8 3,244,550 4/1966 Farnham et al 117-368 25 3,666,477 5/1972 Golfe 117'-36.8
WILLIAM D. MARTIN, Primary Examiner B. D. PIANALTO, Assistant Examiner 0 US. 01. X.R.
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|U.S. Classification||503/216, 503/225, 428/531, 428/524|
|International Classification||D06P1/651, B41M5/333, B41M5/30, D06P1/64|