JP3353438B2 - Thermal recording paper - 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 medium, and more particularly to an improvement in a heat-sensitive recording paper provided with a heat-sensitive coloring layer containing a colorless or slightly light-colored leuco dye and a color developer which develops color when heated. .

[0002]

2. Description of the Related Art A heat-sensitive recording system using a colorless or slightly pale leuco dye and a color developing agent which causes the leuco dye to develop color when heated does not require a developing step and is easy to maintain hardware. Because of these features, it is widely used for various printers, facsimile machines, and recording of measuring instruments.

Conventionally, high quality paper has been generally used as a support for thermal paper. In acidic papermaking, papermaking is performed by internally adding a rosin-based sizing agent and fillers such as clay and talc, but a sulfate band is generally used as a fixing agent for the rosin-based sizing agent and remains in the paper. Due to the sulfuric acid radicals, the pH of the paper surface becomes an acidic side, and the coloring material constituting the thermal paper reacts with the acidic ions on the surface of the paper, so that the background is easily covered during the long-term storage period.

As an improvement, Japanese Patent Application Laid-Open No. 55-156087
The use of neutral paper as a heat-sensitive paper support is proposed in Japanese Patent Application Laid-Open No. H10-146, and the surface properties of the support are further improved by using a Yankee dryer to improve the surface properties of the support using neutral paper. Japanese Patent Application Laid-Open No. 62-5880 discloses that the recording clarity is improved.

[0005]

However, when a neutral paper is used as a support for the thermal recording paper, when the thermal paper is stored for a long period of time, the coloring ability may be reduced before recording, or may be reduced after recording. The print will be faint, fuzzy, or even almost invisible. When the thermal paper is stored for a long period of time, there is a phenomenon that the sensitivity and the saturation concentration at the time of production decrease. If the coloring ability is reduced in this manner, the printing density of the thermal recording paper is reduced, making it difficult to read, and there is a problem that the original function as the thermal recording paper is lost.

The present invention has been made in view of the above-mentioned points, and has as its object the object of the present invention to provide a clear recording without a long-term background fogging, a characteristic of neutral paper itself, without a decrease in coloring ability. It is intended to provide a thermal paper that can be used.

[0007]

According to the present invention, there is provided a thermosensitive recording layer comprising, on a support, a thermosensitive coloring layer containing a colorless or slightly light-colored leuco dye and a color developer which is colored upon contact with the leuco dye. In paper, the support is a synthetic sizing agent.
Neutral paper making using alkyl ketene dimer
Paper and under the pH = 8.0 of the synthetic sizing agent.
Kicking zeta potential of the solid concentration of 0.02% solution + 20 mV
A thermosensitive recording paper characterized by the following.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a synthetic sizing agent is used as a sizing agent.
A dimer emulsion type is used. The structure of the alkyl ketene dimer is shown below.

[0009]

Since the above alkyl ketene dimer is lipophilic, it is used by forming an emulsion with a hydrophilic protective colloid. As the hydrophilic protective colloid, cationic starch or a synthetic cationic polymer is generally used.
The inventors of the present application studied protective colloids and found that a difference in the degree of cationization caused a difference in coloring ability.

The thermal recording paper of the present invention uses an alkylketene dimer having a zeta potential of +20 mV or less in a 0.02% solids solution at pH = 8.0 as a sizing agent for neutral paper. Is achieved by

The zeta potential of the sizing agent was measured by adjusting the solid content concentration of the sizing agent to 0.02% and adjusting the pH to 8.0 with sodium hydroxide.

The leuco compound used for forming the heat-sensitive color in the heat-sensitive recording paper of the present invention may be used alone or in a mixture of two or more kinds. Examples thereof include triphenylmethane, fluoran, spiropyran, and the like. Examples include phenothiazine-based, auramine-based, and indolinophthalide-based compounds.

Specifically, 3,3-bis (p-dimethylaminophenyl) phthalide, 3,3-bis (p-dimethylphenyl) -6-dimethylaminophthalide,
Bis (p-dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino -6-chlorofluoran, 3-dimethylamino-
5,7-dimethylfluoran, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluoran, 3-
N-ethyl-N-ethyl-N-isoamyl-6-methyl-7-anilinofluoran, 3-diethylamino-7-
Chlorofluorane, 3-diethylamino-7-methylfluoran, 3-dimethylamino-7,8-benzfluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3- (N-ethyl-N- p-tolyl) -6
Methyl-7-alininofluoran, 3- (Np-tolyl-N-ethylamino) -6-methyl-7-alininofluoran, 3-pyrrolidino-6-methyl-7-alininofluoran, 2- {N-3'-trifluoromethylphenyl) aminofluorane, 2- {3,6-bis (diethylamino) -9- (o-chloroanilino) xanthylbenzoate lactam}, 3-diethylamino-6-methyl-
7- (m-trichloromethylalinino) fluoran, 3
-Diethylamino-7- (o-chloroalinino) fluoran, 3-dibutylamino-7- (o-chloroallinino) fluoran, 3-N-methyl-N-amylamino-
6-methyl-7-anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-
Anilinofluoran, 3-diethylamino-6-methyl-7- (2 ′, 4′-dimethylalinino) fluoran,
3- (N, N-diethylamino) -5-methyl-7-
(N, N-dibenzylamino) fluoran, benzoylleucomethylene blue, 6′-chloro-8′-methoxy-benzoindolino-pyrinospirane, 6′-bromo-3′-methoxy-benzoindolino-pyrrospirane,
3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-chlorophenyl)
Phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-nitrophenyl) phthalide, 3- (2'-hydroxy-4 '
-Diethylaminophenyl) -3- (2-methoxy-
5'-methylphenyl) phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-methylphenyl) phthalide, 3-morpholino-7 -(N-propyl-trifluoromethylarino) fluoran, 3-diethylamino-
5-chloro-7- (N-benzyl-trifluoromethylanilino) fluoran, 3-pyrridino-7- (di-p-
(Chlorophenyl) methylaminofluoran, 3-diethylamino-5-chloro-7- (α-phenylethylamino) fluoran, 3- (N-ethyl-p-toluidino)
-7- (α-phenylethylamino) fluoran, 3-
Diethylamino-7- (o-methoxycarbonylphenylamino) fluoran, 3-diethylamino-5-methyl-7- (α-phenylethylamino) fluoran, 3
-Diethylamino-7-piperidinofluoran, 2-chloro-3- (N-methyltoluidino) -7- (pn-
Butylanilino) fluoran, 3-dibutylamino-6
-Methyl-7-anilinofluoran, 3,6-bis (dimethylamino) fluorenespiro (9,3 ')-6'-
Dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4′-bromofluoran, 3-diethylamino-6-chloro-7-anilino Fluoran, 3-N-
Ethyl-N- (2-ethoxypropyl) amino-6-methyl-7-anilinofluoran, 3-N-ethyl-N-
Tetrahydrofurfurylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7
-Mesitidino-4 ', 5'-benzofluoran and the like are used.

Further, a color developing agent also used in the thermosensitive coloring layer is in contact with the above-mentioned leuco compound or the like, and an electron-accepting compound for forming a color, such as a phenolic compound,
Thiophenolic compounds, thiourea derivatives, organic acids and metal salts thereof, and specifically, 4,4′-isopropylidenebisphenol, 4,4 ′
Isopropylidenebis (o-methylphenol),
4,4'-secondary butylidene bisphenol,
4,4'-isopropylidenebis (2-tert-butylphenol), 4,4'-cyclohexylidenediphenol, 4,4'-isopropylidenebis (2-chlorophenol), 2,2'-methylenebis (4- Methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 4,4′-butylidenebis (6-tert-butyl-2-methylphenol), 1,1,1 3-Tris (2
-Methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-
(Hydroxy-5-cyclohexylphenyl) butane,
4,4′-thiobis (6-tert-butyl-2-methylphenol), 4,4′-diphenolsulfone,
-Isopropoxy-4'-hydroxyphenylsulfone, 4-benzyloxy-4'-hydroxydiphenylsulfone, 4,4'-diphenolsulfoxide, isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, benzyl protocatechinate, Stearyl gallate, lauryl gallate, octyl gallate, 1,7
-Bis (4-hydroxyphenylthio) -3,5-dioxaheptane, 1,5-bis (4-hydroxyphenylthio) -3-oxapentane, 1,3-bis (4-hydroxyphenylthio) -propane , 1,3-bis (4-
(Hydroxyphenylthio) -2-hydroxypropane,
N, N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, saltylanilide, 5-chloro-salicylanilide, 2-hydroxy-3-naphthoic acid, 2-hydroxy-1-naphthoic acid , 1-hydroxy-2-naphthoic acid, metal salts of hydroxynaphthoic acid such as zinc, aluminum and calcium, bis (4-hydroxyphenyl) acetic acid methyl ester, bis (4-hydroxyphenyl) acetic acid benzyl ester, bis (4- Hydroxyphenyl) acetic acid butyl ester, 1,3-bis (4
-Hydroxycumyl) benzene, 1,4-bis (4-hydroxycumyl) benzene, 2,4′-diphenolsulfone, 3,3′-diallyl-4,4′-diphenolsulfone, α, α -Bis (4-hydroxyphenyl) α
-Methyltoluene, zinc thiocyanate antipyrine complex, tetrabromobisphenol A, tetrabromobisphenol S and the like are used.

Further, in the paint for forming the thermosensitive coloring layer, the polymer used as a binder includes starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose and ethylcellulose, and polyvinyl. Alcohol, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid copolymer, styrene / maleic anhydride copolymer alkali salt, isobutyl / maleic anhydride copolymer Alkaline salts, polyacrylamide, sodium alginate, gelatin, water-soluble polymers such as casein, polyvinyl acetate, polyurethane, polyacrylate, polymethacrylic Ester, vinyl chloride, vinyl acetate copolymer, water-based emulsion by ethylene-vinyl acetate copolymers, styrene-butadiene copolymer, latexes such as by styrene-butadiene-acrylic copolymer or the like is used.

In the coating for forming the thermosensitive coloring layer, there may be further used ordinary auxiliary additives such as fillers (inorganic or organic pigments), heat-soluble substances, lubricants, surfactants, coloring dyes, coloring pigments, and the like. Fluorescent dyes, fluorescent pigments, optical brighteners,
It is a matter of course that a storage stabilizer such as an ultraviolet absorber can be used in combination if necessary, and more specifically, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, sulfuric acid. Inorganic fine particles such as barium, clay, talc, surface-treated calcium and silica,
Urea-formalin resin, styrene-methacrylic copolymer, filler such as organic fine powder such as polystyrene resin, stearic acid, fatty acids such as behenic acid, stearic acid amide, p-benzylbiphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β
-Benzyloxynaphthalene, β-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid methyl ester, diphenyl carbonate, terephthalic acid dibenzyl ester, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dibenzyloxoinaphthalene, 1,2-bis (phenoxy) ethane, 1,2-
(3-methylphenoxy) ethane, 1,2-bis (4-
Methylphenoxy) ethane, 1,4-bis (phenoxy) butane, 1,4-bis (phenoxy) -2-butene, dibenzoylmethane, 1,4-bis (phenylthio) butane, 1,4-bis (phenylthio) -2-butene, 1,3-bis (2-vinyloxyethoxy) benzene, 1,4-bis (2-vinyloxyethoxy) benzene, p- (2-vinyloxyethoxy) biphenyl, p
-Aryloxybiphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, 1,3-dibenzoyloxypropane, dibenzyldisulfide, 1,
1-diphenylethane, 1,1-diphenylpropanol, p- (benzyloxy) benzyl alcohol,
3-diphenoxy-2-propanol, N-octadecylcarbonyl-p-methoxycarbonylbenzene, N-
A heat-fusible substance such as octadecylcarbamoylbenzene is used.

Various fillers and fixing agents of various sizes, such as calcium carbonate, can be used for the support. Further, in order to improve the dot reproducibility of the heat-sensitive recording paper, a large amount of filler is added or the amount of oil absorption is reduced. Larger fillers can also be used.

Further, the thermosensitive recording paper of the present invention may be provided with an inorganic pigment and a binder as a main component or an intermediate layer containing a binder as a main component between the support and the thermosensitive coloring layer, if necessary. An overcoat layer can also be provided on the heat-sensitive recording layer.

Next, the test method will be described. As for the color developing ability test method, the obtained thermosensitive recording paper is originally stored under normal environmental conditions (for example, 20 ° C.-65% RH) for 1 to 2 years, a print test is performed after storage, and a print density before storage is obtained. It is necessary to compare the print density after storage with the print density. However, since the test itself requires a long period of time, the inventors of the present application have enthusiastically pursued a test method for the color forming ability. An accelerated test method equivalent to storage for about one year under normal storage conditions by storing for 10 days under the environmental conditions of
We decided to apply and test this. That is, the sample
The test was performed using an accelerated test method in which the sample was stored for 10 days at 90 ° C.-90% RH.

Hereinafter, the present invention will be described in detail with reference to specific examples, but the present invention is not limited to these examples. Preparation of heat-sensitive paint Liquid A: 3-dibutylamino-6-methyl-7-anilinofluoran 9 parts by weight Polyvinyl alcohol: 12% aqueous solution 15 parts by weight Polystyrene ammonium acrylate: 12% aqueous solution 0.7 part by weight Water 30 Parts by weight Liquid B: 2,2'-bis (4-hydroxyphenyl) propane 20 parts by weight m-terphenyl 20 parts by weight Polyvinyl alcohol: 12% aqueous solution 50 parts by weight Polystyrene ammonium acrylate: 12% aqueous solution 3 parts by weight 62.3 parts by weight of water

Each liquid of the above composition was separately dispersed by a sand grinder until the average particle diameter became 1 μm or less.

Liquid C: Light calcium carbonate 20 parts by weight Water 80 parts by weight Liquid C was dispersed using a homomixer for 15 minutes.

Solution A prepared above: 54.7 parts by weight, B
Liquid: 155.3 parts by weight and Liquid C: 100 parts by weight, and zinc stearate (30% dispersion) 3
3.3 parts by weight, 100 parts by weight of polyvinyl alcohol (12% aqueous solution) and 80 parts by weight of water were added to obtain a heat-sensitive paint.

Example 1 70 parts of bleached hardwood kraft pulp and bleached softwood kraft pulp 30 beaten to 350 ml of CSF with a labus beater
Part, and an alkylketene dimer having a zeta potential of +4 mV (trade name: AS262; manufactured by Nippon PMC Co., Ltd.) is added as a neutral sizing agent at 1% per pulp, and sedimentable calcium carbonate [Shiraishihana PC; Manufactured by KK Co., Ltd.], and hand-pressed with a TAPPI type sheet machine, and air-dried after pressing to obtain a neutral paper having 50 g of rice tsubo and a ash content of 25%.

On the support obtained above, a heat-sensitive paint was applied so that the coating amount after air-drying was 4 g / m ² , and the coating was further subjected to a gloss treatment to obtain a surface smoothness of about 500 seconds. To obtain a thermosensitive recording paper.

Example 2 In Example 1, an alkyl ketene dimer having a zeta potential of +10 mV [trade name: AS273;
Thermorecording paper was obtained in the same manner as in Example 1 except that the following was used.

Example 3 In Example 1, an alkyl ketene dimer having a zeta potential of +17 mV [trade name: Sizepine K-287;
Thermal recording paper was obtained in the same manner as in Example 1 except that Arakawa Chemical Co., Ltd. was used.

Comparative Example 1 In Example 1, an alkyl ketene dimer having a zeta potential of +30 mV [trade name: AS263;
Thermorecording paper was obtained in the same manner as in Example 1 except that the following was used.

Comparative Example 2 A thermosensitive recording paper was prepared in the same manner as in Example 1, except that an alkyl ketene dimer having a zeta potential of +40 mV (trade name: Silene S94; manufactured by Kao Soap Co., Ltd.) was used. Obtained.

Comparative Example 3 In Example 1, an alkyl ketene dimer having a zeta potential of +45 mV [trade name: Sizepine K-903;
Thermal recording paper was obtained in the same manner as in Example 1 except that Arakawa Chemical Industry Co., Ltd. was used.

A color-forming ability test was performed on the heat-sensitive recording paper obtained above. 40 ° C-90% RH for color development test
Store under atmosphere for 10 days, then 20 ° C-65% RH
An accelerated test method was used in which temperature and humidity were adjusted under the following conditions, printing was performed, and comparison was made with the printing density of the thermosensitive recording paper before storage. The test results are shown in the following table.

[0033]

[Table 1]

In the above table, ○ indicates that the print density after storage was unchanged from that before storage, △ indicates that the print density after storage was slightly lower than before storage, and X indicates that after storage. The print density is clearly inferior to that before storage, and the XX marks show almost no print even after printing.

As shown in the above evaluation results, in Examples 1 to 3 of the present invention, an alkyl ketene dimer was used as a synthetic sizing agent, and the solid content concentration of the synthetic sizing agent at pH = 8.0 was 0. The zeta potential of the .02% solution is +2
The recording density after storage is equal to or less than 0 mV, and the print density after storage is not different from the print density before storage. Further, in all of Comparative Examples 1 to 3 outside the above-mentioned conditions, even after printing after storage, the print density was reduced, or the print was hardly visible, and there was a problem of the coloring ability.

[0036]

As described above, the heat-sensitive recording paper of the present invention uses, as a support, neutral paper formed by using an alkylketene dimer having a zeta potential of +20 mV or less as a neutral sizing agent. As a result, it is possible to obtain a heat-sensitive recording paper having good long-term storage properties as compared with conventional ones.

Claims (1)

(57) [Claims] To 1. A on a support, heat-sensitive recording paper having a heat-sensitive color developing layer containing a color developer which develops color in contact with a colorless or slightly pale leuco dye and said leuco dye, the support is synthetic Use alkyl ketene dimer as sizing agent
Neutral paper-making paper, and said synthetic sizing agent
Wherein the zeta potential of a 0.02% solids solution at pH = 8.0 is +20 mV or less.