JPH04338584A - Thermal recording paper - Google Patents

Abstract

PURPOSE:To conserve wood resources using a support containing high yield pulp and to provide a thermal recording paper not lowering color forming capacity during preservation. CONSTITUTION:In a thermal recording paper wherein a thermal recording layer based on a leuco dye and a developer is provided on a support, the pulp constituting the support contains 10-100wt.% of high yield pulp and a barrier layer is provided between the support and the thermal recording layer and moisture permeability of the support/barrier layer is 1000g/m<2>/24hr or less in an atmosphere of relative humidity of 90%.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to thermal recording paper, and more particularly to thermal recording paper 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, thermal recording paper is used in large quantities in fields such as facsimile machines, various printers, and ticketing machines because the maintenance of recording equipment is relatively easy.For this reason, large amounts of wood pulp are consumed in the production of thermal recording paper. 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.

For this reason, even in the production of thermal recording paper, which consumes a large amount of wood pulp, in order to fulfill the social responsibility of conserving and recycling wood resources, we do 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 paper that uses high-quality paper made of chemical pulp as a support, thermal recording paper that uses a support that includes 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 paper manufactured using a support containing high-yield pulp has a problem in that its coloring ability decreases significantly during storage. The inventors of the present invention have developed a thermal recording paper manufactured using a support containing high-yield pulp.
The reason for the significant decrease in coloring ability during storage is the sensitive groups of lignin contained in high-yield pulp, such as phenolic
It was discovered that this is because OH groups, alcoholic OH groups, methoxy groups, etc. react with the phenolic OH groups of the color developer, which dissociates under high humidity, and the active phenol of the color developer is gradually lost. conducted research on the mechanism that prevents the influence of lignin on color developers. In order to prevent the influence of lignin in the support on the color developer, it was considered to provide a barrier layer between the support and the heat-sensitive recording layer, but it was not possible to sufficiently prevent the decrease in coloring ability.

The inventors of the present invention have focused on the fact that the decline in color development ability is largely related to humidity, and that the lignin in the support and the color developer in the heat-sensitive recording layer react through moisture. By providing a barrier layer between the heat-sensitive recording layer and the heat-sensitive recording layer, which exhibits a certain level of moisture permeability when combined with the support,
The present invention was completed based on the discovery that it is possible to effectively prevent a significant decrease in the coloring ability of thermosensitive recording paper.

[0006]

[Problems to be Solved by the Invention] By using a support containing a high-yield pulp, it is possible to save wood resources in the production of thermal recording paper, and at the same time, the support contains a high-yield pulp that does not lose its coloring ability during storage. The purpose of the present invention is to provide a thermal recording paper using a support.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a heat-sensitive recording paper having a heat-sensitive recording layer containing a leuco dye and a color developer as main components on a support. The constituent pulp contains high-yield pulp of 10 to 100% by weight, a barrier layer is provided between the support and the heat-sensitive recording layer, and the support / The moisture permeability of the barrier layer is 1 per 24 hours.
000 g/m2 or less.

The present invention further provides the heat-sensitive recording paper having a barrier layer on the support opposite the heat-sensitive recording layer. The following materials can be mentioned as barrier coating agents used in the present invention. For example, polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic amide/acrylic ester copolymer,
Water-soluble acrylic acid amide/acrylic ester/methacrylic acid terpolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, etc. In addition to polyvinyl acetate, polyvinyl acetate,
Polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, polybutyl methacrylate ethylene/
Latex such as vinyl acetate copolymer and styrene/butadiene/acrylic copolymer. Note that, if necessary, an inorganic filler can be added to this barrier coating agent and applied to the support.

The coating amount of the barrier layer on the support is not particularly limited as long as it satisfies a predetermined moisture permeability, but it is generally 1 to 10 g/dry solid weight.
m2, preferably 2 to 7 g/m2. Further, as a means for applying the barrier layer, well-known conventional techniques such as an air knife coater, a blade coater, and a size press can be used.

[0010] The support used in the present invention is a paper made of pulp consisting of a pulp with a low lignin content such as a high yield pulp of 10 to 100% by weight and a conventional chemical pulp, and the basis weight thereof is 10 to 100% by weight. 300g/m2,
Preferably it is 30 to 200 g/m2. This high-yield pulp has a yield of 70% compared to the raw wood that is the raw material.
Refers to the pulp produced as above, and in consideration of saving wood resources, pulp with a yield of 80% or more is preferable. Examples of this high-yield pulp include ground wood pulp, refiner ground pulp, chem refiner pulp, chem ground pulp, thermomechanical pulp, chemothermomechanical pulp, and pressurized ground pulp.

[0011] Recycled paper made from waste paper can also be used as a support in the present invention if the content of high-yield pulp exceeds 10%. The reason is that paper for newspapers, magazines, etc., which is the main raw material for recycled paper, is usually made from high-yield pulp, and recycled paper uses a large amount of deinked pulp containing waste paper from newspapers, magazines, etc. This is because they are doing so.

[0012] Considering that a barrier layer will be provided on the support later, the sizing degree of the support is preferably relatively high, and is generally 3 to 100 seconds, preferably 5 to 50 seconds. In the heat-sensitive recording paper of the present invention, the following leuco dyes can be mentioned as leuco dyes constituting the heat-sensitive recording layer. 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-dimethylaminophthalide, 3,3-
Triallyl such as bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylpyrrol-3-yl)-6-dimethylaminophthalide, etc. Methane dye, 4,4
'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoolamine, N-2,
Diphenylmethane dyes such as 4,5-trichlorophenylleucoolamine, thiazine dyes such as benzoylleucomethylene blue and p-nitrobenzoylleucomethylene blue, 3-methyl-spirodinaphthopyran, 3
Spiro dyes such as -ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo)spiropyran, and 3-propyl-spiro-dibenzopyran , lactam dyes such as rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluoran,
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-dibenzylamino Fluoran, 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)fluoran, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3
-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3-(N-methyl-N-n-amyl)
amino-6-methyl-7-phenylaminofluorane,
3-(N-ethyl-N-n-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-iso-amyl)amino-6-methyl-7-phenylaminofluorane Orane, 3-(N-methyl-N-n-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-n-hexyl)amino-6-methyl-7-phenyl Aminofluorane, 3-(
N-ethyl-N-β-ethylhexyl)amino-6-methyl-7-phenylaminofluorane and the like.

Further, in the present invention, the color developer used in combination with the leuco dye is not particularly limited, and has the property of being liquefied, vaporized, or dissolved by an increase in temperature, and has the property of being liquefied, vaporized, or dissolved when it comes into contact with the leuco dye. These are various color developers that have the property of causing color development. Typical examples of color developers include the following. 4-t
ert-butylphenol, α-naphthol, β-naphthol, 4-acetylphenol, 4-tert-octylphenol, 4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-dihydroxy-diphenylmethane, 4, 4'-isopropylidene diphenol, hydroquinone, 4,4'-cyclohexylidene diphenol, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis(6-ter
t-butyl-3-methylphenol), 4,4'-dihydroxydiphenylsulfone, hydroquinone monobenzyl ether, 4-hydroxybenzophenone, 2,4
-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate,
sec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, 4-hydroxybenzoic acid Phenylpropyl, phenethyl 4-hydroxybenzoate, p-chlorobenzyl 4-hydroxybenzoate, p-4-hydroxybenzoate
Phenolic compounds such as methoxybenzyl, novolac type phenolic resins, phenolic polymers, benzoic acid, p
-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec -butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3-(α-
methylbenzyl) salicylic acid, 3-chloro-5-(α-
methylbenzyl)salicylic acid, 3,5-di-tert-
Aromatic carboxylic acids such as butylsalicylic acid, 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids, etc. Zinc, magnesium, aluminum, calcium, titanium,
These include organic acidic substances such as salts with polyvalent metals such as manganese, tin, and nickel.

The amount of the leuco dye used in the heat-sensitive recording layer is 0.1 to 2.0 g/m2, preferably 0.3 to 2.0 g/m2.
It should be 1.0g/m2. The ratio of the leuco dye to the color developer is generally 100 to 700 parts by weight, preferably 100 parts by weight of the color developer to 100 parts by weight of the leuco dye.
It is 50 to 400 parts by weight. Note that two or more of the leuco dye and color developer may be used in combination, if necessary.

[0015] 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, using a ball mill, an attritor, a sand grinder, or other stirring or pulverizing machine. 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%
It is used in a proportion of 5% by weight. Furthermore, various auxiliary agents can be added to the coating liquid as necessary. for example,
Dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts,
Other examples include antifoaming agents, fluorescent dyes, and colored dyes.

[0016] Also, it improves the adhesion of debris 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 paper 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.
Furthermore, various known techniques in the field of heat-sensitive recording paper can be added, such as an intermediate layer using an inorganic pigment such as calcined kaolin or silica or an organic pigment such as a plastic pigment, between the support and the heat-sensitive recording layer. .

[0019]

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) Production of thermal recording paper A pulp suspension was prepared by blending 60 parts by weight of refiner ground pulp with a base paper yield of 90% and 40 parts by weight of LB kraft pulp (LBKP). In this, rosin size is added as a sizing agent to 100 parts by weight of bone-dried pulp.
4 parts by weight was added. After adjusting the pH of this pulp slurry to 4.6 with sulfuric acid band, papermaking was carried out and the paper weight was 50g
/m2 of paper was obtained. Formation of Barrier Layer Each barrier agent listed in Table 1 was applied to the surface of the support on which the heat-sensitive recording layer was to be provided. Thereafter, the moisture permeability of the support/barrier layer was measured according to the standard specified in JIS Z-0208. Preparation of heat-sensitive coating liquids 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 bisphenol A

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 for 10 minutes using a homomixer.

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. The above-mentioned heat-sensitive coating liquid was applied onto the barrier layer of this paper so that the coated amount after drying was 7 g/m 2 and dried, and the surface was further treated with a gloss calender to obtain each heat-sensitive recording paper.

[0021] After storing each of the heat-sensitive recording papers produced in Examples under the following conditions, a color development test was conducted, and the effects of the barrier layer composed of each barrier agent and the case where no barrier layer was provided were obtained. The results are shown in Table 1. Although the air permeability is also listed for reference, it is clear that there is no correlation between the air permeability and the survival rate, and that there is no relationship between the air permeability and the effects of the present invention. [Evaluation Method] The 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.

[0022]
[Table 1]──────────────
──────────────────────
Barrier agent coating amount
Moisture permeability Air permeability Residual rate Actual concentration
g/
m2 g/m2 24h (sec) %
Front Back────────────────────
──────────────────Polyvinyl acetate emulsion 3.5 90 1
100 94 1.34 1.26 Styrene/maleic anhydride 4.4 15
0 15000 92 1.35
1.24 Copolymer ammonium salt polyurethane 2
．． 9 180 840 90
1.33 1.20 Vinyl chloride/vinyl acetate polymer 3.1 380 12000
85 1.35 1.15 Polyvinyl acetate emulsion 2.8 440
1600 94 1.32 1.24
case in
4.7 650 19000
87 1.33 1.16 Polyvinyl alcohol 5.5 810
9900 81 1.34 1.0
9 Polyurethane
2.4 970 560
72 1.33 0.96
3.2 12
00 12000 54 1.33
0.72 Polyvinylpyrrolidone
1.8 1800 790
43 1.34 0.58 Vinyl chloride/vinyl acetate polymer 1.9 2700
670 41 1.33 0.55 Sodium alginate 2.5 3
900 10000 27 1.3
3 0.36 Polyvinyl alcohol
1.0 4400 660
29 1.30 0.38 None
─
5100 10 12 1
．． 30 0.16 ────────────────
──────────────────────
*Air permeability was measured based on JIS P 8117.

[0023]

Effects of the Invention: By using a support containing high-yield pulp, wood resources can be saved in the production of thermal recording paper, and coloring ability does not deteriorate during storage.
A thermal recording paper using a support containing high-yield pulp could be obtained.

Claims (2)

[Claims] 1. A heat-sensitive recording paper having a heat-sensitive recording layer containing a leuco dye and a color developer as main components on a support,
The pulp constituting the support contains 10 to 100% by weight of high-yield pulp, a barrier layer is provided between the support and the heat-sensitive recording layer, and under an atmosphere of a temperature of 40 ° C. and a relative humidity of 90%, A thermosensitive recording paper characterized in that the moisture permeability of the support/barrier layer is 1000 g/m2 or less per 24 hours. 2. The heat-sensitive recording paper according to claim 1, further comprising a barrier layer on the support opposite to the heat-sensitive recording layer.