JPH0159919B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermal recording paper, and more particularly to a thermal recording paper characterized by containing a colorless or light-colored color-forming compound, an organic acid, and a compound represented by the formula (). R ₁ SO ₂ OR ₂ () In formula (), R ₁ is a C _1-4 alkyl group or a phenyl group optionally substituted with a halogen or a C _1-4 alkyl group, and R ₂ is a C _1-4 alkyl group. An alkyl group, a halogen, a nitro group, an amino group, an acetylamino group, a C _1-4 alkyl group, a phenyl group optionally substituted with a C _1-4 alkoxy group, a naphthyl group, or -R ₆ -O- It has long been known that a color-forming lactone compound such as crystal violet lactone, which represents an R ₇ group (R ₆ is a C _1-2 alkylene R ₇ represents a phenyl group or a naphthyl group), reacts with an organic acid to produce color. The application of this reaction to thermal paper is known, for example, from JP-A-45-14039. However, when thermal recording paper is actually used in a thermal printer, the color development sensitivity is often insufficient and the printing speed is often reduced, and additives are used to improve these problems. For example, JP-A-48-1923 describes the use of waxes as additives, but since waxes hardly dissolve color-forming compounds or organic acids, their effectiveness is limited to limited uses. It is difficult to match with a thermal head due to its non-adhesive properties and low mold releasability. Mata Tokuko Showa 51-
27599 describes the use of fatty acid amide waxes, but in this type, the boundaries between colored and non-colored areas are unclear, causing so-called smearing in printing. Furthermore, an example of using acetalinide is described in Japanese Patent Publication No. 43-4160, but when it is used, the ground color (whiteness of thermal paper) is extremely poor, and when color is developed, the gradient of color density is small with respect to the applied temperature, resulting in poor contrast. Good printing cannot be obtained. Furthermore, since acetalinide itself has sublimation properties, thermal paper containing it has poor storage stability. The present inventors have conducted extensive research into additives that improve color development sensitivity in order to improve the above-mentioned drawbacks, and as a result, the compound represented by formula () has a high color development density and a large concentration gradient with respect to the applied temperature. We have discovered that we can provide recording paper with good storage stability that does not cause printing smearing and does not disappear even when exposed to plasticizers, surfactants, etc., without the need for a protective layer on the top or back side of the coloring layer. The invention has been completed. Specific examples of the sulfonic acid ester derivative represented by formula () include the following. Methanesulfonic acid phenyl ester, methanesulfonic acid-4-chlorophenyl ester, methanesulfonic acid-4-bromphenyl ester, methanesulfonic acid-P-tolyl ester, methanesulfonic acid-4-nitrophenyl ester, methane Sulfonic acid-2,4-dinitrophenyl ester, methanesulfonic acid-4-aminophenyl ester, methanesulfonic acid-2,4-diaminophenyl ester, methanesulfonic acid-4-acetylaminophenyl ester, methanesulfone acid-
2,4-bisacetylaminophenyl ester,
Methanesulfonic acid 4-methoxyphenyl ester, benzenesulfonic acid 2-aminonaphthyl ester, p-chlorobenzenesulfonic acid methyl ester, P-bromobenzenesulfonic acid methyl ester, P-toluenesulfonic acid phenyl ester, P- Toluenesulfonic acid-4-chlorophenyl ester, P-toluenesulfonic acid-4-bromobromphenyl ester, P-toluenesulfonic acid-4-chloro-3-methylphenyl ester, P-toluenesulfonic acid-3- Methyl phenyl ester, P-toluenesulfonic acid-4-chloro-2,6-dinitrophenyl ester, P-toluenesulfonic acid-6-bromo-2,4-dinitrophenyl ester, P-toluenesulfonic acid-
4-chloro-2,6-dinitro-3-methylphenyl ester, P-toluenesulfonic acid-4-nitrophenyl ester, P-toluenesulfonic acid-6-nitro-2-methylphenyl ester, P
-Toluenesulfonic acid-4-nitro-2-methylphenyl ester, P-toluenesulfonic acid-
2,4-dinitrophenyl ester, P-toluenesulfonic acid-2,6-dinitro-4-methylphenyl ester, P-toluenesulfonic acid-4,
6-dinitro-2-methylphenyl ester, P
-Toluenesulfonic acid-4,6-dinitro-3-
Methyl phenyl ester, P-toluenesulfonic acid-2,6-dinitro-4-methylphenyl ester, P-toluenesulfonic acid-4-aminophenyl ester, P-toluenesulfonic acid-4-methoxyphenyl ester, P-toluenesulfonic acid-2-amino-4-methylphenyl ester,
P-toluenesulfonic acid-2,4-bisacetaminophenyl ester, P-toluenesulfonic acid tolyl ester, P-toluenesulfonic acid-β
-Phenoxyethyl ester, P-toluenesulfonic acid-β-naphthyloxyethyl ester, P
-Toluenesulfonic acid naphthyl ester, P-toluenesulfonic acid-4-nitronaphthyl(2) ester, P-toluenesulfonic acid-2,4-dinitronaphthyl(1) ester, P-toluenesulfonic acid-
4-chloronaphthyl ester, P-toluenesulfonic acid-4-methylnaphthyl ester, P-toluenesulfonic acid-4-methoxynaphthyl ester. The colorless or light-colored color-forming compounds used in the present invention are compounds that can develop color by reacting with organic acids, such as triphenylmethane-based, triphenylmethane-phthalide-based,
Examples include various leuco bodies such as fluoran type, diphenylmethane type, leuco auramine type, spiropyran type, indoline type, and indico type. Specifically, crystal violet lactone, malachite green lactone, 3-diethylamino-7-methylfluoran, 3-diethylamino-7-(o-chloroanilino)fluoran,
3-diethylamino-7-(m-fluoromethylanilino)fluorane, 3-diethylamino-6
-Methyl-7-anilinofluoran, 3-diethylamino-7-(o-fluoroanilino)fluoran, benzo-β-naphthospiropyran, rhodamine lactone, etc., but are not particularly limited to these. On the other hand, organic acids are substances that are solid at room temperature, dissolve when heated, and react with colorless or light-colored color-forming compounds to become color developers, such as bisphenol A, 2,2'-bis(4 -hydroxyphenyl)pentane, phenolic substances such as 2,6-tert-butylphenol, fatty acids or aromatic carboxylic acids such as oxalic acid, maleic acid, citric acid, succinic acid, stearic acid and benzoic acid, etc. . Next, a general method for manufacturing the thermal recording paper of the present invention will be described. A color-forming compound, an organic acid, and an additive of formula () can be mixed separately with a binder in water or an organic solvent, or a color-forming compound, an organic acid, and one or both of the additives of formula () can be mixed with a binder. Grind in water or in an organic solvent using a ball mill, attritor, sound glider, etc., together with a surfactant if necessary. In some cases, the color-forming compound, the organic acid, and the compound of formula () may be ground in advance in a powder state and then dispersed in water or an organic solvent containing a surfactant or a binder. The following methods can be used to apply the thus obtained dispersion onto a support. (1) Mix each grinding solution and apply it to the support. (2) Without mixing the color-forming compound liquid and the organic acid liquid, mix the additive pulverized liquid of formula () with either or both of them and apply them sequentially on the same sheet. (3) Either a color-forming compound or an organic acid is present in the sheet by impregnating the support or drawing it,
A pulverized solution of the additive of formula () is applied onto the sheet. (4) Apply a color-forming compound alone or a mixture of a pulverized solution of the additive of formula () and an organic acid solution to two sheets, and bring the coated surfaces into close contact. In this case, at least one sheet contains an additive of formula (). Binders used in the present invention include starch, polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, alkali salts of styrene-maleic anhydride copolymers, styrene-acrylic acid copolymers,
A water-soluble polymer compound such as modified polyacrylamide or a latex is used, and a surfactant is also used if necessary, and the surfactant can be arbitrarily selected from anionic and nonionic surfactants. Clays, starches, waxes, etc. can also be added to the heat-sensitive coating liquid, if necessary. Paper is most suitable as the support sheet, and other materials such as synthetic resin films and woven fabric sheets may also be used depending on requirements. In the present invention, the molar ratio between the color-forming compound and the organic acid is generally from 1:2 to 1:20, and the amount of the color-forming compound on the support is generally from 0.1 to 0.6 g/m ² . The additive of formula (2) is generally effective when applied in an amount equal to to 10 times the weight of the color-forming compound, preferably in a range of 1 to 5 times the weight. Next, in order to explain the present invention more specifically, Examples will be described and the effects thereof will be shown, but the present invention is not limited to these Examples. Example 1

[Table] Both liquids A and B were prepared separately in a ball mill.
After pulverizing for several days, liquid A: liquid B = 4:25 (parts by weight) was thoroughly mixed to prepare a heat-sensitive coating liquid. The coating amount after drying is approximately 5 ^.
g/m ² and dried to obtain heat-sensitive recording paper. Next, compared to the heat-sensitive recording paper obtained in Comparative Example 1 and Comparative Example 2, in which color was developed at 100°C for 5 seconds with a thermal head, a recording paper with a whiter ground color, a higher color density, and no bleeding of printed characters was obtained. . (Table 1) Example 2

[Table] Thermosensitive recording paper was obtained using both solutions A and B in the same manner as in Example 1. Next, color development was performed using a thermal head. The heat-sensitive recording paper had much better color density than the heat-sensitive recording papers obtained in Comparative Examples 3 and 4 (Table 2), and as is clear from FIG. Compared to No. 4, the coloring density gradient is larger and the coloring characteristics are excellent. Example 3 In the composition of Solution A of Example 2, 3-(N-methylcyclohexylamino)-6- was used instead of 3-diethylamino-7-o-fluoroanilinofluorane.
Methyl-7-anilinofluorane was heat-sensitive in the same manner as in Example 2 except that in the composition of Solution B, methanesulfonic acid-P-chlorophenyl ester was used instead of P-toluenesulfonic acid phenyl ester. I got the recording paper. The measured values of the ground color and color density of the resulting thermal recording paper using a Macbeth densitometer were 0.12 and 0.12, respectively.
1.12, which was very good, and there was no bleeding of the thermal paper. Example 4 In the composition of liquid B of Example 3, methanesulfonic acid
A thermosensitive recording paper was obtained in the same manner as in Example 3 except that P-toluenesulfonic acid-β-phenoxyethyl ester was used instead of P-chlorophenyl ester. The measured values of the ground color and color density of the obtained thermal paper using a Macbeth densitometer were very excellent, 0.12 and 1.20, respectively, and no bleeding of the thermal paper was observed. Example 5 Thermal recording was carried out in the same manner as in Example 4 except that P-toluenesulfonic acid phenyl ester was used instead of P-toluenesulfonic acid-β-phenoxyethyl ester in the composition of Solution B of Example 4. Got paper. The ground color and color density measured using the Macbeth densitometer were very excellent, 0.12 and 1.19, respectively, and no bleeding of the thermal paper was observed. Comparative Example 1 A recording paper was prepared in the same manner as in Example 1 except that p-toluenesulfonic acid phenyl ester was removed. Comparative Example 2 A recording paper was prepared in the same manner as in Example 1 except that acetanilide was used instead of P-toluenesulfonic acid phenyl ester. Comparative Example 3 A recording paper was prepared in the same manner as in Example 2 except that p-toluenesulfonic acid phenyl ester was removed. Comparative Example 4 In Example 2, Aramide HT (a mixture of palmitylamide, stearylamide, and oleylamide manufactured by Lion Armor) was used in place of P-toluenesulfonic acid phenyl ester to prepare a recording paper. Comparative Example 5 A recording paper was prepared in the same manner as in Example 5 except that p-toluenesulfonic acid phenyl ester was removed. See Figure 2 for the characteristics of the recording paper.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 shows the relationship between the hot plate temperature (applied temperature) and color density (Macbeth reflection density) of Example 2 and Comparative Examples 3 and 4. FIG. 2 shows the relationship between hot plate temperature and Macbeth reflection density in Example 5 and Comparative Example 5.

Claims (1)

[Claims] 1. A colorless to light-colored color-forming compound, an organic acid, and a formula R ₁ SO ₂ OR ₂ () [In the formula (), R ₁ is a C _1-4 alkyl group, or a halogen, or a C _{1-4 R2} is a phenyl group which may be substituted with an alkyl group, or a halogen, a nitro group, an amino group, an acetylamino group, a _C1-4 alkyl group, _{a C1-4} A phenyl group, a naphthyl group, which may be substituted with an alkoxy group,
or _-R6 -O- _R7 ( _R6 represents _C1-2 alkylene _R7 represents a phenyl group or a naphthyl group)] A thermosensitive recording paper characterized by containing a compound represented by the following formula.