JPH02227280A - Thermosensitive recording paper - Google Patents

Abstract

PURPOSE:To obtain thermosensitive recording paper which does not become curled easily even under low humidity condition and stacks up smoothly by using base paper as a support which indicates a dynamic wetting value as specified two seconds after being soaked in water, and providing a layer containing salt at the specified vapor pressure of an unsaturated aqueous solution at 20 deg.C on the rear. CONSTITUTION:The wetting value of base paper as a support two seconds after being soaked in water ranges from -0.30 to 0.20g. If the value is higher than 0.20g, the coating of a recording layer deteriorates and subsequently, the recording density reduces. In the meantime, if the value is not more than -0.30g, the adhesion between the base paper and the recording layer decreases. In addition, a layer containing salt at the vapor pressure of a saturated aqueous solution at 20 deg.C on the rear of the support is provided. If salt at the vapor pressure of less than 3.0mmHg is used, the recording layer becomes too hygroscopic and generates blocking. If salt at the vapor pressure of 3.0mmHg or more is used, the recording layer becomes less hygroscopic so that the base paper cannot be kept flexible by maintaining the moisture contact at high level under low humidity condition. Consequently, the desired favorable effect cannot be obtained. This type of salt is, for example, calcium chloride or magnesium chloride.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a thermal recording paper, and particularly to a thermal recording paper that has excellent stackability during printing by a recording device such as a printer facsimile.

``Prior Art'' Conventionally, thermal recording paper utilizes the reaction between a colorless or light-colored basic dye and an organic or inorganic coloring agent to bring both light-colored substances into contact with each other using heat to obtain a recorded image. well known. Such thermal recording paper is relatively inexpensive, the recording device is compact, and its maintenance is relatively easy, so it is used not only as a medium for facsimiles and various computers, but also in a wide range of fields.

Thermosensitive recording paper is desired to always provide stable recorded images even under various external environmental conditions.

However, when recording under low humidity, problems such as paper jams and paper jams may occur due to the tendency of the paper to curl. .

In order to solve these problems, a method of providing a back coat layer on the back side of the support has been proposed, but there has not been sufficient research on how to improve the curling tendency of recording paper and the suitability of paper passing through recording equipment. is the current situation.

"Problems to be Solved by the Invention" In view of the current situation, the present inventors have conducted extensive research on supports used in thermal recording paper, and have found that a specific back coat layer is provided on a support having a specific dynamic wetting value. It was found that the stacking aptitude was improved extremely efficiently.

``Means for Solving the Problems'' The present invention provides a heat-sensitive recording layer comprising a support and a heat-sensitive recording layer containing a colorless or light-colored basic dye and a coloring agent capable of forming a color upon contact with the dye. In the case of paper, a base paper with a dynamic wettability value of -0°30 to 0.20 g after 2 seconds of immersion in water is used as the support, and the vapor pressure of a saturated aqueous solution at 20°C is 3.0 on the back side. This thermal recording paper is characterized by being provided with a layer containing salt at ~13°0 mmHg.

[Effect]

The dynamic wettability value is the dynamic wettability tester (WET-3000
/■Resca) was used to determine the wettability of the base paper (
This is the value measured over time (adhesion force). Specifically, using the above tester, a 2 x 5 cm test piece was
This method measures the degree of wetting over time (adhesion force) when immersed in water for 10 seconds at a speed of 12 mm/second.

As a result of further research on this wettability value, the present inventors found that
It has been found that, as a temporal wetting value measured with this tester, the wetting value 2 seconds after immersion in water has a very large effect on the smoothness of the thermosensitive recording paper.

Therefore, the dynamic wetting value in the present invention refers to the wetting value 2 seconds after immersion in water.

That is, when this value is large (the wettability of the base paper is high), water permeates into the base paper in a large amount, and the coverage of the surface of the base paper with the recording layer decreases, resulting in a decrease in smoothness. It has also been found that when the value is small, quality deterioration occurs such as poor compatibility between the recording layer (coating liquid) and the base paper, resulting in a decrease in surface strength.

Therefore, the dynamic wetting value of the base paper in the present invention is −0.
, 30 to 0.20 g. Incidentally, 0°20g
If it becomes higher, the coverage by the recording layer will decrease, and the recording density will decrease. On the other hand, if it is less than -0.30 g, the adhesive force between the base paper and the recording layer will decrease, which is not preferable.

Further, in the present invention, a layer containing a salt having a vapor pressure of a saturated aqueous solution of 3.0 to 13.0 mmHg at 20 DEG C. is provided on the back surface of the support. Vapor pressure is 3.0 mmHg
If a salt less than 13. Omn+Hg
If the salt exceeds the above, the desired effect cannot be obtained because the salt has low hygroscopicity and cannot maintain the moisture content of the base paper at low humidity and maintain the flexibility of the base paper.

Examples of such salts include calcium chloride, magnesium chloride, copper chloride, zinc nitrate, calcium nitrate, magnesium nitrate, ammonium nitrate, calcium bromide, sodium bromide, acetoxypotassium, acetoxymagnesium, sodium iodide, potassium iodide, etc. can be mentioned.

The amount of these salts applied to the support is not particularly limited, but if it is too large, blocking tends to occur, and if it is too small, the effect of the present invention cannot be obtained, so it is generally 0.01 to 2.0 g/ level, preferably 0.04
It is adjusted within a range of about 0.5 g/rrf.

Further, the layer containing this salt may be formed as a coating liquid obtained by mixing the salt with a suitable binder, and if necessary, inorganic pigments, waxes, waterproofing agents, etc. may be added to the coating liquid. It is also possible to add suitable auxiliaries.

As for the coating method, it can be formed according to conventionally well-known and commonly used techniques, and for example, an appropriate coating device such as an air knife coater, a blade coater, a bar coater, a gravure coater, a curtain coater, etc. is used.

In the present invention, there are various known colorless or light-colored basic dyes constituting the recording layer of the thermal recording paper.
For example, the following are exemplified.

3.3-bis(p-dimethylaminophenyl)6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2 -dimethylindol-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-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoolamine, N-2,4,
Diphenylmethane dyes such as 5-trichlorophenylleucoauramine, benzoylleucomethylene blue, p
- Thiazine dyes such as nitrobenzoylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho(6 '-Methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran and other spiro-based dyes, rhodamine-B-anilinolactam,
Lactam dyes such as rhodamine (p-nitroanilino)lactam and rhodamine (0-chloroanilino)lactam, 3-dimethylamino-7-medoxyfluorane, 3-
Diethylamino-6-medoxyfluorane, 3-diethylamino-7-medoxyfluorane, 3-diethylamino-7-lyrolofluorane, 3-diethylamino-6-
Methyl-7-chlorofluorane, 3-diethylamino-
6,7-dimethylfluorane, 3-(N-ethyl-p-
) Luidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-? -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-)luidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-P-)luidino)-6-methyl-7-(p-)luidino)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-phenylaminofluorane,
3-Piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluorane, 3-dibutylamino-
7-(0-chlorophenylamino)fluorane, 3-pyrrolidino-6methyl-7-p-butylphenylaminofluorane, 3-(N-methyl-Nn-amyl)amino-6-methyl-7-phenylaminofluoran Oran, 3-(
N-ethyl-Nn-amyl)amino-6-methyl-7
-phenylaminofluorane, 3-(N-ethyl-N-
isoamyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-methyl-Nn-hexyl)amino-6-methyl-7-phenylaminofluorane, 3
- (N-ethyl-N-n-hexyl)amino-6-methyltophenylaminofluorane, 3-(N-ethyl-N-β-ethylhexyl)amino-6-methyl-7-
Phenylaminofluorane, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-cyclopentyl)amino-6-methyl-7- Fluoran dyes such as phenylaminofluorane. Of course, the dyes are not limited to these dyes, and two or more types of dyes can be used in combination.

Furthermore, various compounds are known as coloring agents used in combination with the above-mentioned basic dyes, for example, the following are exemplified.

4-tert-butylphenol, α-naphthol, β
-naphthol, 4-acetylphenol, 4-tar
t-octylphenol, 4.4'-5ec-butylidene diphenol, 4-phenylphenol, 4.4'-
Dihydroxy-diphenylmethane, 4゜4'-isopropylidenediphenol, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, hydroquinone, 4
．． 4'-cyclohexylidene diphenol, 4.4'
-(1,3-dimethylbutylidene)bisphenol,
4.4' dihydroxydiphenyl sulfide, 4.4
'-thiobis(6-tart-butyl-3-methylphenol), 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-methoxydiphenylsulfone, 4- Hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-3'4'-1-limethylenediphenylsulfone,4-hydroxy-3',4
'-tetramethylenediphenylsulfone,3,4-dihydroxy-4'-methyldiphenylsulfone, bis(3
-allyl-4-hydroxyphenyl)sulfone, 1.3
-di(2-(4-hydroxyphenyl)-2-propyl)benzene, hydroquinone monobenzyl ether, bis(4-hydroxyphenyl)acetic acid butyl ester, 4-
Hydroxybenzophenone, 2゜4-dihydroxybenzophenone, 2.4.4'-trihydroxybenzophenone, 2.2', 4゜4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, 4 -ethyl hydroxybenzoate,
Propyl 4-hydroxybenzoate, 5ec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, 4
-chlorophenyl hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, p-chlorobenzyl 4-hydroxybenzoate, p-methoxybenzyl 4-hydroxybenzoate,
Phenolic compounds such as novolac type phenolic resins and phenol polymers, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-se
c-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,
5-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3-(α-methylbenzyl)salicylic acid,
3-chloro-5-(α-methylbenzyl) salicyl fi
, 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid, aromatic carboxylic acids such as 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids such as zinc, magnesium , organic acidic substances such as salts with polyvalent metals such as aluminum, calcium, titanium, manganese, tin, and nickel. In addition,
Of course, two or more of these coloring agents can be used in combination as necessary.

The ratio of the basic dye and coloring agent to be used is appropriately selected depending on the type of basic dye and coloring agent used, and is not particularly limited, but is generally based on 100 parts by weight of the basic dye. 100-700 parts by weight, preferably 150-4
About 0.00 parts by weight of coloring agent is used.

Coating liquids containing these substances generally use water as a dispersion medium,
It is prepared by dispersing the dye and coloring agent together or separately using a stirring/pulverizing machine such as a ball mill, attritor, or sand mill.

Such coating liquids usually contain starches and binders as binders.
Hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene/maleic anhydride copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion, etc. have a total solid content. 2 to 40% by weight, preferably 5 to 25% by weight.

Furthermore, various auxiliary agents can be added to the coating liquid.
Examples include dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, oil foaming agents thereof, fluorescent dyes, and coloring dyes.

Furthermore, 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 improve the adhesion of residue to the recording head. In addition, stearic acid, polyethylene, carnauba wax, bar 7, etc. are used to prevent sticking from contact with recording equipment or recording heads.
A dispersion or emulsion of fine wax, zinc stearate, calcium stearate, ester wax, etc. can also be added.

Furthermore, if necessary, stearic acid amide and fatty acid amides such as stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, and coconut fatty acid amide; 2.
2'-methylenebis(4-methyl-5-tert-butylphenol), 4,4'-butylidenebis(6-te
rt-butyl-3-methylphenol), 1,1.3-
1-Lis(2-methyl-4-hydroxy-5-tert
Hindered phenols such as -butylphenyl)bukun, p-benzylbiphenyl, 1,2-bis(phenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, 1,2-bis(3-methylphenoxy) ) ethane, 2
-Ethers such as naphthol benzyl ether, dibenzyl terephthalate, esters such as l-hydroxy-2naphthoic acid phenyl ester, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2
Ultraviolet absorbers such as -hydroxy-4-benzyloxybenzophenone and various known thermofusible substances can also be used together as sensitizers.

In the thermosensitive recording paper of the present invention, the method for forming the recording layer is not particularly limited, and the coating apparatus described above can be used.

Furthermore, the amount of coating liquid to be applied is not particularly limited, and is generally 2 to 12 g/rr in terms of dry weight. , preferably within the range of 3 to 10 g/rd.

Note that it is also possible to provide an overcoat layer on the recording layer for purposes such as protecting the recording layer.

(Examples) The present invention will be described in more detail below with reference to Examples, but the present invention is of course not limited to these. In addition, "part" and "%" in the examples are "part" and "%" respectively, unless otherwise specified.
"Parts by weight" and "% by weight" are shown.

Example I ■ Preparation of Solution A 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-phenylaminofluorane 10 parts 1.2-bis(3-methylphenoxy)ethane 20 parts Methylcellulose 5% aqueous solution 20 parts water
40 parts of this composition was ground in a sand mill until the average particle size was 2 μm.

■ Preparation of Solution B 4.4'-Isopropylidene diphenol 30 parts Methyl cellulose 5% aqueous solution 40 parts water
20 parts of this composition was ground in a sand mill until the average particle size was 2 μm.

■ Formation of recording layer 90 parts of liquid A, 90 parts of liquid B, silicon oxide pigment (trade name: Mizukashiru P-527, average particle size: 1°8 μm, oil absorption:
180cc/100g, Mizusawa Chemical Co., Ltd.) 30 copies, 20%
150 parts of oxidized starch aqueous solution and 28 parts of water were mixed and stirred to prepare a coating liquid.

The obtained coating liquid was applied to a base paper of 47 g/n (paper made so that the dynamic wetting value was -0.05 g), and the coating amount after drying was 5.
A recording layer was provided by coating and drying so as to give a ratio of g/%.

■Formation of back layer
A 2% aqueous solution of *Hg) was applied and dried at a coating amount of 10 cc/i, followed by supercalender treatment to obtain a thermal recording paper of the present invention.

Example 2 In forming the back side of Example 1, calcium chloride (vapor pressure of a saturated aqueous solution at 20° C., 5.5%) was used instead of zinc nitrate.
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that a 2% aqueous solution of 6 mmHg) was used.

Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that a base paper having a dynamic wetting value of 0.30 g was used.

Comparative Example 2 In forming the back surface of Example 1, potassium nitrate (vapor pressure of a saturated aqueous solution at 20° C. was 16%) was used instead of zinc nitrate.
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that a 2% aqueous solution of 0 mm)Ig) was used.

Comparative Example 3 In forming the back surface of Example 1, lithium chloride (vapor pressure of saturated aqueous solution at 20°C: 2.6) was used instead of zinc nitrate.
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that a 2% aqueous solution of 2% mmHg) was used.

Comparative Example 4 A thermosensitive recording paper was obtained in the same manner as in Example 1, except that a 2% aqueous solution of polyvinyl alcohol was used instead of zinc nitrate in forming the back side of Example 1.

[Stack aptitude]

The six types of thermal recording paper obtained were finished into rolls with a diameter of 40 mm, left for 24 hours under low humidity conditions (20°C, 20% RH), and then sent to a thermal facsimile machine (Matsushita Densen ■, tlF-1000).
Printing was performed on 10 sheets of A4 size paper, and stacking suitability was evaluated based on the following criteria.

H Seal ○Nidoraburu does not occur.

Δ: The recording paper falls off the tray after printing.

×: The recording paper causes a paper jam.

[Blocking aptitude]

The six types of heat-sensitive recording paper obtained were stacked so that the recording side and back side were in contact with each other, a 300 g weight was placed on top of the paper, and after being left at high temperature conditions (30°C, 80% RH) for 24 hours, the recording side and The blocking state of the back side was evaluated.

Note ○ Ni blocking does not occur at all.

× Ni blocking occurs.

Table 1 "Effects" As is clear from the results in Table 1, the thermal recording paper of the present invention was resistant to curling even under low humidity and had excellent stackability.

Claims (1)

[Claims] In a heat-sensitive recording paper in which a heat-sensitive recording layer containing a colorless or light-colored basic dye and a coloring agent capable of forming a color upon contact with the dye is provided on a support, 2 seconds after immersion in water as the support. Using base paper with a dynamic wetting value of -0.30 to 0.20 g,
Moreover, the vapor pressure of a saturated aqueous solution at 20°C on the back surface is 3.
1. A thermal recording paper characterized by being provided with a layer containing salt at 0 to 13.0 mmHg.