JPH04332682A - Thermal recording material - Google Patents

Abstract

PURPOSE:To conserve wood resources in the manufacturing of a thermal recording material by using a support containing high yield pulp and to provide the thermal recording material using said support excellent in color forming properties and generating no lowering of color forming capacity even during preservation. CONSTITUTION:In a thermal recording material wherein a thermal recording layer containing a leuco dye and a developer is provided on a support, the pulp constituting the support contains 10-100wt.% of high yield pulp and the developer is a phenolic compound with an MW of 270-1000.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a heat-sensitive recording material, and in particular to a heat-sensitive recording material that can be manufactured while saving wood resources by using a support containing high-yield pulp. .

0002

BACKGROUND OF THE INVENTION In recent years, with the advancement of office equipment such as word processors and the spread of computers, the use of paper has increased significantly. In particular, heat-sensitive recording media are used in large quantities in fields such as facsimile machines, various printers, and ticket issuing machines because the maintenance of recording equipment is relatively easy, and for this reason, large amounts of wood pulp are consumed in the production of thermal recording media. ing. On the other hand, in recent years, environmental protection has become more important as the destruction of the global environment has progressed, and conservation and recycling of wood resources are being encouraged to prevent excessive deforestation.

[0003] For this reason, even in the production of heat-sensitive recording media, which consumes a large amount of wood pulp, in order to fulfill the social responsibility of conserving and recycling wood resources, we not only use chemical pulp, etc., which has only half the yield of raw wood. It has become necessary to use high-yield pulps and generally wastepapers containing high-yield pulps. For these reasons, instead of the conventional thermal recording medium that uses high-quality paper made of chemical pulp as a support, a thermal recording medium that uses a support containing waste paper and mechanical pulp, which is a type of high-yield pulp, has been developed. JP-A-58-25986 discloses a heat-sensitive recording material using a support containing waste paper pulp, and JP-A-2-5518 discloses a heat-sensitive recording material using a support containing waste paper pulp.
No. 8 discloses a heat-sensitive recording material using a support containing mechanical pulp.

[0004] However, heat-sensitive recording materials produced using supports containing high-yield pulp have a problem in that their coloring ability is significantly reduced during storage.

[0005]

[Problem to be solved by the invention] By using a support containing high-yield pulp, it is possible to save wood resources in the production of heat-sensitive recording materials, and the coloring ability is excellent and the coloring ability does not deteriorate during storage. An object of the present invention is to provide a heat-sensitive recording material using a support containing high-yield pulp.

[0006]

[Means for Solving the Problems] The inventors of the present invention have discovered that in heat-sensitive recording materials manufactured using a support containing high-yield pulp, the reason why the coloring ability significantly decreases during storage is due to the high-yield pulp. The sensitive groups contained in lignin, such as phenolic OH groups, alcoholic OH groups, and methoxy groups, and the phenolic OH of the color developer that dissociates under high humidity.
We discovered that this is because the active phenol of the color developer is gradually lost as the groups react, and we conducted research on a color developer that is less affected by lignin. As a result, by using a phenolic compound with a molecular weight of 270 or more as a color developer together with a support containing high-yield pulp, it is possible to prevent a significant decrease in the coloring ability of a heat-sensitive recording material that occurs during storage. The present invention was completed by discovering that a thermosensitive recording material exhibits excellent coloring ability during use.

The present invention provides 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 a high-yield pulp of 10 to 100% by weight. The object of the present invention is to provide a heat-sensitive recording material, characterized in that the color developer is a phenolic compound having a molecular weight of 270 to 1,000. The support used in the present invention is 10 to
Paper made from pulp with low lignin content such as 100% by weight high yield pulp and conventional chemical pulp, and has a basis weight of 10 to 300 g/
m2, preferably 30 to 200 g/m2.

[0008] This high-yield pulp refers to pulp manufactured so that the yield is 70% or more based on the raw wood used as raw material, and when considering the conservation of wood resources, the yield is 80% or more.
% or more is preferable. As this high yield pulp,
For example, ground wood pulp, refined ground pulp,
Examples include chem refiner pulp, chem ground pulp, thermomechanical pulp, chem thermomechanical pulp, and pressurized ground pulp. Recycled paper made from waste paper also has a high-yield pulp content of 1.
When it exceeds 0%, it can be used as a support in the present invention. The reason is that newspapers, which are the main raw material for recycled paper,
Paper such as magazines is usually made from high-yield pulp,
This is because recycled paper uses a large amount of deinked pulp containing waste paper from newspapers, magazines, etc.

The color developer used in the heat-sensitive color forming layer of the present invention has a molecular weight of 270 to 1000, preferably 270 to 600.
It is a phenolic compound. For example, monophenol, bisphenol, triphenol, polyhydric phenol, etc. can be used regardless of the number of OH groups in the phenol, and the phenol may contain a sulfur atom in the molecule. Specific examples include the following: Monophenols such as N-stearyl-P-aminophenol, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4,4'-(1-methylbentridene)bisphenol, tetramethylbisphenol A, 4
,4'-(α-methylbenzylidene)bisphenol,
4,4'-(P-phenylene diisopropylidene)bisphenol, 4,4'-[1,3-phenylenebis(1
-methylethylidene)] bisphenol, 4,4'-cyclohexylidene bisphenol, 2,2-bis(4-
Hydroxy-3isopropylphenyl)propane, α,
α′-bis(3-methyl-4-hydroxyphenyl)-
m-diisopropylbenzene, n-butylbis(hydroxyphenyl)acetate, 4,4'-thiobis(6-
bisphenols such as t-butyl-m-cresol), 2,2-bis(3-allyl-4-hydroxyphenyl)sulfone, and tetramethylbisphenol S, α, α′,
α″-tris(4-hydroxyphenyl)-1,3,5
-triisopropylbenzene, 4,4'-[1-[4-
These are triphenols such as [1-(4-hydroxyphenyl)-1-methylethyl]phenyl]ethylidene]bisphenol and polyhydric phenols such as stearyl gallate.

[0010] Leuco dyes that can be used in the heat-sensitive recording material 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-ethylcarbazol-3-yl)-6-dimethylamino Phthalide, 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-leucoauramine, N-2,4,5-
Diphenylmethane dyes such as 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- Spiro dyes such as dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine (p- nitroanilino) lactam, rhodamine (
Lactam dyes such as o-chloroanilino)lactam, 3
-dimethylamino-7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-
7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,
7-dimethylfluorane, 3-(N-ethyl-p-toluidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3
-diethylamino-7-N-methylaminofluorane,
3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-N-methyl-N-benzylaminofluorane, 3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino- 7-N-diethylaminofluorane, 3-(N
-ethyl-p-toluidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-(p-toluidino)fluorane, 3-diethylamino-6- Methyl-7-phenylaminofluorane, 3-dibutylamino-6-methyl-7-
Phenylaminofluorane, 3-diethylamino-7-
(2-carbomethoxy-phenylamino)fluorane,
3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-
Piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluorane, 3-dibutylamino-7-
(o-chlorophenylamino)fluoran, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, 3-(N-methyl-Nn-amyl)amino-
6-Methyl-7-phenylaminofluorane, 3-(N
-ethyl-Nn-amyl)amino-6-methyl-7-
Phenylaminofluorane, 3-(N-ethyl-N-i
so-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-methyl-Nn-hexyl)
amino-6-methyl-7-phenylaminofluorane,
3-(N-ethyl-N-n-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-β-ethylhexyl)amino-6-methyl-7
-phenylaminofluorane, etc.

The amount of these leuco dyes used in the heat-sensitive recording layer is 0.1 to 2.0 g/m2, preferably 0.3 g/m2.
~1.0g/m2. The ratio of the leuco dye to the color developer is generally 100 to 700 parts by weight, preferably 150 parts by weight, per 100 parts by weight of the dye.
~400 parts by weight. Note that two or more of the leuco dye and color developer may be used in combination, if necessary.

The reason why the amount used is limited in this manner is that if the color developer is contained in excess of this amount, sticking will occur, and the adhesion of residue on the thermal head will increase, reducing running performance. Even with conventional color developers with a molecular weight of 270 or less, if the amount consumed by reacting with lignin is added, the decline in coloring ability can be prevented, but as mentioned above, sticking occurs and the running of the thermal head is reduced. It cannot be used in practice because it reduces performance.

[0013] Generally, a coating solution containing these is prepared by dispersing the leuco dye and color developer together or separately using water as a dispersion medium, stirring with a ball mill, attritor, sand grinder, etc., or dispersing the color developer separately. Prepare as a liquid. Such coating liquids usually contain binders such as starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene/maleic anhydride copolymer salt, styrene/butadiene copolymer emulsion, etc. 2-40% by weight of total solids, preferably 5-2%
5% by weight is used. Furthermore, various auxiliary agents can be added to the coating liquid as necessary. Examples include dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, other antifoaming agents, fluorescent dyes, and coloring dyes.

[0014] Also, it improves the adhesion of residue to the recording head,
In addition, inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, and activated clay may be added to further whiten the heat-sensitive recording layer. In addition, waxes such as dispersions or emulsions of stearic acid, polyethylene, carnauba wax, paraffin wax, calcium stearate, zinc stearate, ester wax, etc. may be added as appropriate to prevent the recording layer from sticking when it comes into contact with the recording head. You can also do it.

In the heat-sensitive recording material of the present invention, the method of forming the recording layer is not particularly limited, and can be formed according to conventionally well-known and commonly used techniques. For example, in a method of applying a heat-sensitive coating liquid to a support, an appropriate coating device such as an air knife coater or a blade coater is used. The amount of coating liquid applied is not particularly limited, but is generally 2 to 12 g/m2, preferably 3 g/m2 in terms of dry weight.
-10g/m2.

Furthermore, if necessary, an overcoat layer may be provided on the recording layer for the purpose of protecting the recording layer, and calcined kaolin, calcined kaolin,
Various known techniques in the field of heat-sensitive recording materials 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]

EXAMPLES The present invention will be explained in detail below based on Examples, but the present invention is of course not limited to the scope of these Examples. a) Manufacture of heat-sensitive recording material Liquids A, B, and C having the following compositions were prepared. Liquid A black coloring dye S-205 (Yamada Chemical: 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-anilinofluorane) 10 parts by weight m-terphenyl

25 〃 Polyvinyl alcohol 12% aqueous solution
30 〃 Polystyrene ammonium acrylate 20% aqueous solution 2.
5 Water

32.5 The above was prepared by dispersing it in paint conditioner for 16 hours. B liquid Color developer listed in Table 1

25 parts by weight 12% polyvinyl alcohol aqueous solution

20 〃 Polystyrene ammonium acrylate 20% aqueous solution 2.5
〃 water

32.5 The above was prepared by dispersing it in paint conditioner for 16 hours. C liquid heavy calcium carbonate

70 parts by weight Synthetic silica P-832 (manufactured by Mizusawa Chemical)
3
0 〃 Sodium polyacrylate 40% aqueous solution

4 〃 Water

96 or more were dispersed in a homomixer for 10 minutes.

Next, 100 parts by weight of liquid A, 80 parts by weight of liquid B,
60 parts by weight of liquid C and 20% zinc stearate dispersion 4
0 parts by weight and 75 parts by weight of a 12% polyvinyl alcohol aqueous solution were mixed to prepare a heat-sensitive coating liquid. 50 parts by weight of thermomechanical pulp with a base paper yield of 90%, L
To a pulp suspension consisting of 50 parts by weight of B kraft pulp (LBKP), 1.4 parts by weight of rosin size was added as a sizing agent per 100 parts by weight of the pulp.

[0019] The pH of the pulp slurry was adjusted to 4.
After adjusting to
got the paper. The heat-sensitive paint was coated on the surface of this paper so that the coated amount after drying was 7 g/m2, and then dried, and the surface was further treated with a gloss calender to obtain each heat-sensitive recording paper. Using the color developer listed in Table 1, each Example 1 to
Seventeen thermal recording papers were manufactured. In addition, thermal recording papers of Comparative Examples 1 to 11 were manufactured using the same method and materials as in the Examples except that the color developer was different. [Example 18] The mixing ratio of high yield pulp and chemical pulp is 100:0, 50:50, 10:90 and 0:10
4-hydroxy-4 as a color developer.
A thermosensitive recording material was produced in the same manner as in the previous example except that '-isopropoxydiphenyl sulfone was used. [Comparative Example 12] A heat-sensitive recording material was produced in the same manner as in Example 18, except that bisphenol A was used as a color developer. [Example 19] Using a support in which the mixing ratio of waste newspaper deinked pulp containing about 80% high yield pulp and chemical pulp was 70:30, 4-hydroxy-4'-isopropoxy was used as a color developer. A thermosensitive recording material was produced in the same manner as in Example 18 except that diphenyl sulfone was used. [Comparative Example 13] A heat-sensitive recording material was produced in the same manner as in Example 19, except that bisphenol A was used as a color developer.

The heat-sensitive recording materials produced in Examples and Comparative Examples were stored under the following conditions and then subjected to a color development test. The results obtained for the thermosensitive recording materials of Examples 1 to 17 and Comparative Examples 1 to 11 are shown in Table 2, Table 3, and FIG. 1, and the relationship between the molecular weight of the color developer and the decrease in coloring ability is clarified. In addition, the results obtained with the thermal recording materials of Example 18 and Comparative Example 12 are shown in Tables 4 and 5, respectively, and the decrease in color forming ability of the conventionally used color developer and the color developer used in the present invention is shown. compared. Furthermore, the results obtained with the heat-sensitive recording bodies of Example 19 and Comparative Example 13 are shown in Table 6, respectively. 1 and no.
2, and a comparison was made of the decrease in coloring ability of a conventionally used color developer and a color developer used in the present invention when waste paper pulp was used. [Evaluation method] Color development after storage was tested as follows. 1. Printing density test Using a thermal gradient tester made by Toyo Seiki, color was developed at a temperature of 150°C, a pressing pressure of 2 kg/cm2, and a pressing time of 5 seconds.
The print density was measured using a Macbeth densitometer RD-514. 2. Printing test after storage The product was stored at 40° C. and 90% RH for 7 days, and then a printing test was conducted using the method described above. 3. Color development after storage The color development after storage was evaluated based on the residual rate.

[0021]
[Table 1] Example Molecular weight
Color developer 1
270 4,4'-Cyclohexylidene bisphenol 2 270 4,4'-
(1-Methylbentridene)bisphenol 3
284 Tetramethylbisphenol A
4 290 4,4'-(α-methylbenzylidene)bisphenol 5
291 4-Hydroxy-4'-isopropoxydiphenylsul
Hong 6 300 n-butyl bis(hydroxyphenyl) acetate 7
306 Tetramethylbisphenol S
8 312 2,2-bis(4-hydroxy-3isopropylphenyl
) Propane 9 3
22 4,4'-(P-phenylene diisopropylidene) bisulfate
phenol 10 322 4,4'
-[1,3-phenylenebis(1-methylethyl
Bisphenol 11 330 2,2-bis(
3-allyl-4-hydroxyphenyl)
Ruhon 12
360 4,4'-thiobis(6-t-butyl-
m-cresol) 13 374 α,
α′-bis(3-methyl-4-hydroxyphenyl)
-m-diisopropylbenzene 14 376 N-
Stearyl-P-aminophenol 15 4
06 Stearyl gallate 16 42
4 4,4'-[1-[4-[1-(4-hydroxyphenylene
)-1-methylethyl]phenyl]ethylidene]bisphenol 17 480 α,α′,α″-tris(4-hydroxyphenyl)-
Comparative example of 1,3,5-triisopropylbenzene Molecular weight
Color developer 1 202
4,4'-dihydroxydiphenyl ether 2
210 Hydroxyphthalic acid dimethyl ester 3 214 4,4'-ethylidene bisphenol 4 215
2,4-dihydroxybenzophenone 5
218 Bis(4-hydroxyphenyl)
Sulfide 6 228 Paraoxybenzoic acid benzyl ester 7 22
8 3,4'-bisphenol A 8
228 Bisphenol A 9
229 4-hydroxysalicylanilide
10 246 bis(4-hydroxy-3
-methylphenyl) sulfado 11 250
2,2-bis(4,4'-hydroxyphenyl)sulfone
[Table 2] Example Molecular weight Before storage After storage
Survival rate
concentration concentration
1 270 1.31
1.27 96.9
2 270 1.33
1.31 98.5
3 284 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 96.2
11 330 1.33
1.25 94.0
12 360 1.35
1.32 97.8
13 374 1.34
1.33 99.3 1
4 376 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
Survival rate after storage
Concentration
Concentration 1 20
2 1.35 0.25
18.5 2 21
0 1.25 0.15
12.0 3 21
4 1.37 0.66
48.2 4 21
5 1.33 0.68
51.1 5 21
8 1.37 0.28
20.4 6 22
8 1.28 1.01
78.9 7 22
8 1.32 0.76
57.6 8 22
8 1.35 0.78
57.8 9 22
9 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 Survival rate Before storage
Pulp after storage Pulp
Print density
Print density 100 0
91.0 1.34
1.22 50 5
0 93.2 1.33
1.24 10
90 94.8 1.
34 1.27 0
100 97.0
1.34 1.30
[Table 5]
High yield chemistry Survival 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 1
0 90 67.4
1.35 0.91
0 100 94
．． 0 1.34 1.2
6
[Table 6] Deinking of waste paper
Chemistry Survival 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]

Effects of the Invention: By using a support containing high-yield pulp, wood resources can be saved in the production of heat-sensitive recording materials, and the color-forming ability is excellent and does not deteriorate during storage. A heat-sensitive recording material using a support containing high yield pulp could be obtained.

[Brief explanation of drawings]

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

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

Claims (1)

[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 contains 10 to 100% by weight of high-yield pulp, A heat-sensitive recording material, wherein the color developer is a phenolic compound having a molecular weight of 270 to 1000.