JP2936550B2 - Thermal recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material which can be manufactured by using a support containing a high-yield pulp to save wood resources. .

[0002]

2. Description of the Related Art In recent years, with the progress of office equipment such as word processors and the spread of computers, the use of paper has increased significantly. In particular, thermal recording media are used in large quantities in fields such as facsimile machines, various printers, and ticketing machines because the maintenance of recording equipment is relatively easy.Thus, a large amount of wood pulp is consumed in the production of thermal recording media. ing. On the other hand, recently, the destruction of the global environment has increased the importance of environmental protection, and the conservation and recycling of timber resources has been encouraged to prevent excessive deforestation of forests.

[0003] Therefore, even in the production of thermal recording media that consumes a large amount of wood pulp, in order to fulfill social responsibilities of saving and recycling wood resources, not only chemical pulp and the like having only half the yield of raw wood but also chemical pulp etc. It has become necessary to use high-yield pulp and wastepaper which generally contains high-yield pulp. For this reason, a thermal recording medium using a support containing waste paper and mechanical pulp, which is a kind of high-yield pulp, has been developed in place of the conventional thermal recording medium using a high-quality paper made of chemical pulp as a support. JP-A-58-25986 discloses a thermal recording medium using a support containing waste paper pulp.
No. 88 discloses a thermal recording medium using a support containing mechanical pulp.

However, a thermosensitive recording medium produced using a support containing a high-yield pulp has a problem that the coloring ability is significantly reduced during storage.

[0005]

By using a support containing a high-yield pulp, it is possible to save wood resources in the production of a heat-sensitive recording medium, and it is excellent in coloring properties and does not decrease in coloring ability during storage. Another object of the present invention is to provide a thermosensitive recording medium using a support containing pulp with high yield.

[0006]

Means for Solving the Problems The inventors of the present invention have found that in a heat-sensitive recording material manufactured using a support containing a high-yield pulp, the color-developability during storage is significantly reduced in the high-yield pulp. Sensitive groups of the contained lignin, such as phenolic OH groups, alcoholic OH groups, and methoxy groups, react with the phenolic OH groups of the developer that dissociates under high humidity, and gradually the active phenol of the developer It was found that this was due to the loss of color, and a study was conducted on a developer that was not easily affected by lignin. As a result, by using a phenolic compound having a molecular weight of 270 or more as a color developer together with a support containing a high-yield pulp, it is possible to prevent a significant decrease in the coloring ability of a heat-sensitive recording medium that occurs during storage. The present inventors have found that a heat-sensitive recording medium exhibits excellent color-forming ability when used, and completed the present invention.

The present invention relates to a heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye and a color developer on a support, wherein the pulp constituting the support is 50 to 100% by weight of a high yield pulp ( (Excluding waste paper pulp) , and the developer is a phenolic compound having a molecular weight of 270 to 480 . The support used in the present invention is a paper made of a pulp comprising a high yield pulp of 50 to 100% by weight and a pulp having a low lignin content such as a conventional chemical pulp, and has a basis weight of 10 to 300 g / m. ² , preferably 30 to 200 g /
m ² .

The term "high-yield pulp" refers to pulp manufactured so that the yield is at least 70% with respect to the raw wood used as a raw material.
% Or more is preferable. As this high yield pulp,
For example, groundwood pulp, refiner ground pulp,
Chemifiner pulp, chemiground pulp, thermomechanical pulp, chemithermomechanical pulp, pressurized ground pulp and the like can be mentioned.

The developer used in the thermosensitive coloring layer of the present invention is a phenolic compound having a molecular weight of 270 to 480 . For example, monophenol, bisphenol, triphenol, polyphenol, etc.
It can be used irrespective of the number of radicals, and may contain a sulfur atom in the molecule. The following are specific examples. Monophenols such as N-stearyl-P-aminophenol, 4-hydroxy-4'-isopropoxydiphenylsulfone, and 4,4 '
-(1-methylbenzilidene) bisphenol, tetramethylbisphenol A, 4,4 '-(α-methylbenzylidene) bisphenol, 4,4'-(P-phenylenediisopropylidene) bisphenol, 4,4'-
[1,3-phenylenebis (1-methylethylidene)]
Bisphenol, 4,4′-cyclohexylidenebisphenol, 2,2-bis (4-hydroxy-3-isopropylphenyl) propane, α, α′-bis (3-methyl-4-hydroxyphenyl) -m-diisopropylbenzene, n-butylbis (hydroxyphenyl) acetate, 4,4'-thiobis (6-t-butyl-m-cresol), 2,2-bis (3-allyl-4-hydroxyphenyl) sulfone, tetramethylbisphenol S, etc. Bisphenols, α, α ′, α ″ -tris (4-hydroxyphenyl) -1,3,5-triisopropylbenzene, 4,4 ′-[1- [4- [1- (4-hydroxyphenyl)- 1-methylethyl] phenyl] ethylidene] triphenols such as bisphenol and polyvalent phenols such as stearyl gallate These are knols.

The leuco dyes usable in the heat-sensitive recording medium of the present invention include the following. 3,3
-Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylindole -3-yl)
Phthalide, 3- (p-dimethylaminophenyl) -3-
(2-methylindol-3-yl) phthalide, 3,3
-Bis (1,2-dimethylindol-3-yl) -5
-Dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazole-3-
Yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3
Triallylmethane dyes such as-(1-methylpyrrol-3-yl) -6-dimethylaminophthalide; 4,4'-
Bis-dimethylaminobenzhydryl benzyl ether, N-halophenyl-leuco auramine, N-2,
Diphenylmethane dyes such as 4,5-trichlorophenyl leuco auramine, thiazine dyes such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue, 3-methyl-spirodinaphthopyran,
3-ethyl-spiro-dinaphthopyran, 3-phenyl-
Spiro-based dyes such as spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho (6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine ( lactam dyes such as p-nitroanilino) lactam and rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3
-Diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluoran, 3- (N- Ethyl-p-toluidino) -7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluoran, 3-diethylamino-7-N-methylaminofluoran, 3-diethylamino-7-di Benzylaminofluoran, 3-diethylamino-7-N-methyl-
N-benzylaminofluoran, 3-diethylamino-
7-N-chloroethyl-N-methylaminofluoran,
3-diethylamino-7-N-diethylaminofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-phenylaminofluoran, 3- (N-ethyl-
(p-Toluidino) -6-methyl-7- (p-toluidino) fluoran, 3-diethylamino-6-methyl-7
-Phenylaminofluoran, 3-dibutylamino-6
-Methyl-7-phenylaminofluoran, 3-diethylamino-7- (2-carbomethoxy-phenylamino) fluoran, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluoran 3-pyrrolidino-6-methyl-7-phenylaminofluoran, 3-piperidino-6-methyl-7-phenylaminofluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino- 7
-(O-chlorophenylamino) fluoran, 3-dibutylamino-7- (o-chlorophenylamino) fluoran, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, 3- (N-methyl-N -N-
Amyl) amino-6-methyl-7-phenylaminofluoran, 3- (N-ethyl-Nn-amyl) amino-
6-methyl-7-phenylaminofluoran, 3- (N
-Ethyl-N-iso-amyl) amino-6-methyl-
7-phenylaminofluoran, 3- (N-methyl-N
-N-hexyl) amino-6-methyl-7-phenylaminofluoran, 3- (N-ethyl-N-n-hexyl) amino-6-methyl-7-phenylaminofluoran, 3- (N-ethyl —N-β-ethylhexyl) amino-6-methyl-7-phenylaminofluoran and the like.

The amount of the leuco dye used is 0.1 to 2.0 g / m ² , preferably 0.3 to 2.0 g / m ² in the heat-sensitive recording layer.
It is adjusted to 1.0 g / m ² . The ratio of the leuco dye to the developer is generally 100 to 700 parts by weight, preferably 150 to 4 parts by weight, per 100 parts by weight of the dye.
00 parts by weight. The leuco dye and the developer may be used in combination of two or more as necessary.

The reason for limiting the amount of use in this way is that if the developer is further contained, sticking occurs, and adhesion of scum to the thermal head increases, resulting in a decrease in running performance. Even if a conventional color developer having a molecular weight of 270 or less is added in addition to the amount consumed by reacting with lignin, a decrease in color forming ability can be prevented for the time being. However, as described above, sticking occurs and the thermal head runs. Can not be used in practice because it reduces the properties.

The preparation of a coating solution containing these is generally carried out by using water as a dispersion medium, stirring the ball mill, an attritor, a sand grinder, or the like, and dispersing the leuco dye and the developer together or separately by a pulverizer. Prepare as a liquid. In such a coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene / maleic anhydride copolymer salt, styrene / butadiene copolymer emulsion and the like are usually used as binders. 2-40% by weight of the total solids, preferably 5-2
5% by weight is used. Further, various auxiliaries can be added to the coating liquid as needed. For example, dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium salt of lauryl alcohol sulfate, metal salts of fatty acids and the like, other antifoaming agents, fluorescent dyes, coloring dyes and the like can be mentioned.

Further, it is possible to improve the adhesion of scum to the recording head,
In order to further make the heat-sensitive recording layer whiter, inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica, and activated clay can be added. Also, stearic acid as appropriate,
A wax such as a dispersion or an emulsion such as polyethylene, carnauba wax, paraffin wax, calcium stearate, zinc stearate, or ester wax can be added so that the recording layer does not stick when the recording layer is brought into contact with the recording head.

In the heat-sensitive recording medium of the present invention, the method for forming the recording layer is not particularly limited, and the recording layer can be formed according to a conventionally well-known conventional technique. For example, in a method of applying a heat-sensitive coating solution to a support, an appropriate coating device such as an air knife coater or a blade coater is used. The coating amount of the coating solution is not particularly limited, but is generally ² to 12 g / m ² , preferably 3 to 12 g / m ² in dry weight.
The range is from 10 to 10 g / m ² .

Further, if necessary, an overcoat layer can be provided on the recording layer for the purpose of protecting the recording layer, etc. Further, between the support and the heat-sensitive recording layer, calcined kaolin,
Various known techniques in the field of thermal recording media can be added, such as an intermediate layer using an inorganic pigment such as silica or an organic pigment such as a plastic pigment.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments, but the present invention is of course not limited to the scope of these embodiments. a) Production of heat-sensitive recording medium Liquids A, B, and C having the following compositions were prepared. A liquid black coloring dye S-205 (Yamada Chemical Co.: 3- (N-ethyl--N- isoamyl) amino-6-methyl-7-anilinofluoran) 10 parts by weight m- data - phenyl 25 〃 polyvinyl alcohol 12 % Aqueous solution 30% polystyrene ammonium acrylate 20% aqueous solution 2.5 {water 32.5} The above was dispersed in a paint conditioner for 16 hours. Liquid B 25 parts by weight of the developer described in Table 1 Aqueous solution of polyvinyl alcohol 12% 20% Aqueous solution of polystyrene ammonium 20% 2.5 {Water 32.5} The above was dispersed in a paint conditioner for 16 hours. Liquid C 70 parts by weight heavy calcium carbonate Synthetic silica P-832 (manufactured by Mizusawa Chemical Co., Ltd.) 30 {aqueous solution of 40% sodium polyacrylate 4} water 96% The above was prepared by dispersing with a homomixer for 10 minutes.

[0018]

After adjusting the pH of the pulp slurry to 4.6 with a sulfuric acid band, hand-making was carried out to obtain a paper of 50 g / m ² per square meter. The heat-sensitive paint was applied to the surface of the paper so that the applied amount after drying was 7 g / m ² , dried and further subjected to surface treatment with a gloss calender to obtain each heat-sensitive recording paper. Using the developers described in Table 1, the thermal recording papers of Examples 1 to 17 were produced. Further, the heat-sensitive recording papers of Comparative Examples 1 to 11 were produced by the same method and the same materials as in the example except that the color developer was different. [Example 18] The mixing ratio of high yield pulp and chemical pulp was 100:
0, 50:50, 10:90 (Reference Example) and 0: 100
A heat-sensitive recording material was produced in the same manner as in the above example, except that the support of Reference Example was used and 4-hydroxy-4'-isopropoxydiphenyl sulfone was used as a color developer. Comparative Example 12 A thermosensitive recording medium was manufactured in the same manner as in Example 18 except that bisphenol A was used as a color developer. [Reference Example 1] Using a support having a mixing ratio of newspaper waste ink deinking pulp containing about 80% of high yield pulp and chemical pulp having a mixing ratio of 70:30,
A heat-sensitive recording material was produced in the same manner as in Example 18 except that 4-hydroxy-4'-isopropoxydiphenylsulfone was used as a developer. Comparative Example 13 Reference Example except that bisphenol A was used as a color developer
In the same manner as in Example 1 , a thermosensitive recording medium was produced.

The heat-sensitive recording materials produced in Examples and Comparative Examples were stored under the following conditions, and then subjected to a coloring test.
The results obtained for the heat-sensitive recording materials of Examples 1 to 17 and Comparative Examples 1 to 11 are shown in Tables 2 and 3 and FIG. 1 to clarify the relationship between the molecular weight of the color developer and the decrease in coloring ability. Tables 4 and 5 show the results obtained with the heat-sensitive recording materials of Example 18 and Comparative Example 12, respectively, showing that the color developing ability of the conventionally used developer and the developer used in the present invention was reduced. Compared. Further, the results obtained by the heat-sensitive recording media of Reference Example 1 and Comparative Example 13 are shown as No. 1 and No. 2 in Table 6, respectively. The reduction in the color forming ability of the color developer used in the present invention was compared. [Evaluation Method] A test for color development after storage was performed as follows. 1. Print Density Test Using a thermal gradient tester manufactured by Toyo Seiki Co., Ltd., the color was developed under the conditions of a temperature of 150 ° C., a pressing pressure of 2 kg / cm ² , and a pressing time of 5 seconds, and the print density was measured with a Macbeth densitometer RD-514. 2. Print test after storage After storage at 40 ° C. and 90% RH for 7 days, a print test was performed by the above method. 3. Color development after storage The color development after storage was evaluated by the residual ratio.

[0021] [Table 1] Example molecular weight developer 1 270 4,4'-cyclohexylidenebisphenol 2 270 4,4 '-(1-methylbenthylidene) bisphenol 3284 tetramethylbisphenol A 4 290 4,4'-( α-methylbenzylidene) bisphenol 5 291 4-hydroxy-4′-isopropoxydiphenylsulfone 6 300 n-butylbis (hydroxyphenyl) acetate 7 306 tetramethylbisphenol S 8 312 2,2-bis (4-hydroxy-3isopropyl Phenyl) propane 9 322 4,4 '-(P-phenylenediisopropylidene) bisphenol 10 322 4,4'-[1,3-phenylenebis (1-methylethylidene)] bisphenol 11 330 2,2-bis ( 3-allyl-4 (Hydroxyphenyl) sulfone 12 360 4,4'-thiobis (6-t-butyl-m-cresol) 13 374 α, α'-bis (3-methyl-4-hydroxyphenyl) -m-diisopropylbenzene 14 376N -Stearyl-P-aminophenol 15 406 stearyl gallate 16 424 4,4 '-[1- [4- [1- (4-hydroxyphenyl) -1-methylethyl] phenyl] ethylidene] bisphenol 17 480α , Α ′, α ″ -tris (4-hydroxyphenyl) -1,3,5-triisopropylbenzene Comparative Example Molecular Weight Developer 1202 4,4′-dihydroxydiphenylether 2210 Hydroxyphthalic acid dimethyl ester 3214 4, 4'-ethylidenebisphenol 4 215 2,4-dihydro Cibenzophenone 5 218 bis (4-hydroxyphenyl) sulfide 6 228 parahydroxybenzoic acid benzyl ester 7 228 3,4′-bisphenol A 8 228 bisphenol A 9 229 4-hydroxysalicylanilide 10 246 bis (4-hydroxy-3-methyl Phenyl) sulfad 11 250 2,2-bis (4,4'-hydroxyphenyl) sulfone [Table 2] Example Molecular weight Before storage After storage Residual concentration Concentration Concentration 1 270 1.31 1.27 96.9 2 270 1.33 1.31 98.5 3284 1.10 1.06 96.4 4 290 1.28 1.15 89.8 5 291 1.33 1.24 93.2 6 300 1.27 1.16 91.3 7 306 1.32 1.24 93.9 8 312 1.28 1.24 96.9 9 322 1.34 1.29 96.3 10 322 1.30 1.25 6.2 11 330 1.33 1.25 94.0 12 360 1.35 1.32 97.8 13 374 1.34 1.33 99.3 14 376 1.05 1.00 95.2 15 406 1 .34 1.33 99.3 16 424 1.34 1.32 98.5 17 480 1.30 1.22 93.8 [Table 3] Comparative Example Molecular weight Before storage After storage Percentage Concentration Concentration 12021 .35 0.25 18.5 2 210 1.25 0.15 12.0 3 214 1.37 0.66 48.2 4 215 1.33 0.68 51.1 5 218 1.37 0.28 20 .4 6 228 1.28 1.01 78.9 7 228 1.32 0.76 57.6 8 228 1.35 0.78 57.8 9 229 1.32 0.86 65.2 10 246 1. 36 0.94 69.1 11 250 1.34 0.59 44.0 [Table 4] High yield chemistry Residual rate Before storage After storage Pulp Pulp Print density Print density 100 0 91.0 1.34 1. 2 50 50 93.2 1.33 1.24 10 90 94.8 1.34 1.270 1.100 97.0 1.34 1.30 [Table 5] High Yield Chemistry Residual Rate Before Storage After Storage Pulp Pulp Print density Print density 100 0 22.4 1.34 0.30 50 50 57.8 1.35 0.78 10 90 67.4 1.35 0.91 0 100 94.0 1.34 1.26 [Table 6] Waste paper deinking chemistry Residual rate Before storage After storage Pulp Pulp Print density Print density No. 1 70 30 93.2 1.33 1.24 No. 2 70 30 42.1 1.33 0.56

[0022]

According to the present invention, by using a support containing a pulp having a high yield, it is possible to save wood resources in the production of a heat-sensitive recording material, and it is excellent in coloring properties, and the coloring ability does not decrease during storage. A heat-sensitive recording material using a support containing a retention pulp could be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the molecular weight of a developer and the residual ratio.

FIG. 2 is a graph showing the relationship between the content of high yield pulp in the pulp constituting the support and the residual ratio. (a) is the case where 4-hydroxy-4'-isopropoxydiphenylsulfone is used as a color developer, and (b) is the case where bisphenol A is used as a color developer.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-21486 (JP, A) JP-A-4-37579 (JP, A) JP-A-2-117883 (JP, A) JP-A-2- 55188 (JP, A) JP-A-62-280070 (JP, A) JP-A-2-292086 (JP, A) WO 91/2653 (WO, A2) (58) Fields investigated (Int. Cl. ⁶⁾ , DB name) B41M 5/28-5/30

Claims (1)

(57) [Claims] 1. A heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye and a color developer on a support, wherein the pulp constituting the support is 50 to 100% by weight of a high yield pulp ( Excluding waste paper pulp), wherein the color developer has a molecular weight of 270
A heat-sensitive recording material, which is a phenolic compound of from 480 to 480 .