JPH10278433A - Thermal recording medium and method of manufacturing the same - Google Patents

Abstract

(57) Abstract: In a heat-sensitive recording paper containing a colorless or light-colored basic dye and a color developer capable of reacting with the dye, 2,4'-dihydroxydiphenyl is used as the color developer. Using sulfone, 4-benzyloxy-4'-
By adding (2,3-epoxy-2-methylpropyl-1-yloxy) diphenylsulfone, image storability (plasticizer resistance) is good, print coloring and whiteness are high, and whiteness is reduced. Provide a less heat-sensitive recording medium. SOLUTION: The developer uses 2,4'-dihydroxydiphenylsulfone, and further has a volume-average particle size distribution and a limited amount of 4-benzyloxy-4 '-(2,4).
A heat-sensitive recording material comprising 3-epoxy-2-methylprop-1-yloxy) diphenylsulfone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording paper, and more particularly to a thermosensitive recording paper. The present invention relates to a material for a thermosensitive recording medium having a property and a manufacturing method thereof.

[0002]

2. Description of the Related Art A thermosensitive recording medium generally comprises a support having thereon a thermosensitive recording layer mainly composed of an electron-donating colorless dye precursor and an electron-accepting developer. pen,
By heating with a laser beam or the like, the colorless dye precursor and the color developer react instantaneously to obtain a recorded image. These heat-sensitive recording materials are described in JP-B-43-4160 and JP-B-45-14039. It is disclosed in gazettes and the like.

[0003] Such a thermosensitive recording medium has the advantages that recording can be obtained with a relatively simple apparatus, maintenance is easy, and there is no noise. For example, a measuring recorder, a facsimile, a printer, Computer terminals, labels,
It is used in a wide range of fields such as automatic ticket vending machines such as tickets.

[0004] The color-forming layer of a heat-sensitive recording medium that forms an image by heating to form an image contains a combination of a color-forming substance and a color-developing substance that reacts with the color-forming substance during heating to form a color. In this case, as the color-forming substance, for example, a colorless or light-colored leuco dye having a lactone, lactam, or spiropyran ring is used.
Various acidic substances such as 4′-isopropylidene diphenol (generic name bisphenol A) are used.

[0005] Such a combination of a color-forming substance and a color-developing substance has been applied to a larger number of heat-sensitive recording materials than before because of its vivid color tone. The heat-sensitive recording material using such an electron-donating colorless dye precursor and an electron-accepting color developer has excellent properties such as good appearance, good feel, high color density, and various color hues. On the other hand, the thermosensitive coloring area (recorded image area) comes into contact with plastics such as polyvinyl chloride and disappears due to plasticizers and additives contained in the plastics, or is contained in foods and cosmetics It has the drawback that it easily disappears upon contact with chemicals, and its record preservation is inferior. Due to this drawback, its use is subject to certain restrictions at present, and its improvement is strongly desired. ing.

[0006]

The present invention relates to a thermosensitive recording medium. More specifically, in a heat-sensitive recording paper containing a colorless or light-colored basic dye and a color developer capable of reacting with the dye to produce a color, 2,4′-dihydroxydiphenyl sulfone is used as the color developer. The volume average particle size is set to 0.
4-benzyloxy-4 ′ adjusted to 8-5.0 μm
-(2,3-epoxy-2-methylpropyl-1-yloxy) diphenylsulfone was added to the developer 2,4 ′
-By adding 5 to 30% by weight to dihydroxydiphenyl sulfone, it has extremely clear color printability, has high whiteness, and its whiteness is little reduced with time and under any environment, and furthermore, print color development. It is an object of the present invention to provide a thermosensitive recording medium that minimizes the decoloration of a printed portion due to a plasticizer or the like, and a method of manufacturing the same.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made a thermosensitive recording containing a colorless or pale-colored basic dye and a color developer which can react with the dye to form a color. In paper, 2,4'-dihydroxydiphenylsulfone is used as the color developer, and more preferably, 4-benzyloxy-4 '-(2,3- Epoxy-2-methylpropyl-1
-Yloxy) diphenylsulfone was added to the developer 2,5′-dihydroxydiphenylsulfone in 5
By adding up to 30% by weight, it has extremely vivid color printability, high whiteness, little decrease in whiteness over time and under any environment, and printing with a plasticizer or the like after printing. The inventors have found that the decoloration of the part can be suppressed as much as possible, and have completed the present invention.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS That is, the present invention is as follows. In a heat-sensitive recording material containing a colorless or light-colored basic dye and a color developer capable of reacting with the dye to produce a color, 1) using 2,4'-dihydroxydiphenyl sulfone as the color developer, Benzyloxy-4'-
(2,3-Epoxy-2-methylpropyl-1-yloxy) diphenylsulfone is added. 2) 4-benzyloxy-4 '-(2,3-epoxy-
The particle size distribution of (2-methylpropyl-1-yloxy) diphenyl sulfone is in the range of 0.8 to 5.0 μm in volume average. 3) 4-benzyloxy-4 '-(2,3-epoxy-
The amount of 2-methylpropyl-1-yloxy) diphenylsulfone to be added is in the range of 5 to 30% by weight based on 2,4′-dihydroxydiphenylsulfone as the color developer.

The 4-benzyloxy-4'- according to the present invention
The particle size distribution of (2,3-epoxy-2-methylpropyl-1-yloxy) diphenylsulfone is preferably in the range of 0.8 to 5.0 μm, more preferably 1.
The range is from 0 to 2.0 μm. When the volume average of the particle size distribution is less than 0.8 μm, the whiteness decreases over time and discoloration of the background (ground fog) occurs under high humidity conditions. No preservative effect was observed.

According to the present invention, 4-benzyloxy-4'-
The amount of (2,3-epoxy-2-methylpropyl-1-yloxy) diphenylsulfone was 5 to 5% of 2,4′-dihydroxydiphenylsulfone as the developer.
The range is preferably from 30 to 30% by weight, more preferably from 7 to 25% by weight. If the added amount is less than 5% by weight based on 2,4′-dihydroxydiphenyl sulfone, the effect of preservability on the plasticizer properties is not recognized, and if it exceeds 30% by weight, the whiteness over time is reduced. Deterioration causes background fog.

In the present invention, the colorless or light-colored basic dyes constituting the recording layer of the heat-sensitive recording material are used alone or as a mixture of two or more as necessary. Any type of heat-sensitive material may be arbitrarily applied, for example, trianylmethane-based, fluoran-based, thiazine-based, spiropyran-based, and lactam-based leuco compounds are preferably used, particularly fluoran-based leuco. Dyes are widely and generally used, and specific examples thereof include the following.

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-methylindole -3-yl)
-5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl)- Triallylmethane dyes such as 6-dimethylaminophthalide, 6 '-[ethyl (3-methylbutyl) amino] -3'-methyl-2'-(phenylamino) -spiro [isobenzylfuran-1-9 ' −
Xanthen] -3-one, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-methyl-N
-Propylamino) -6-methyl-7-anilinofluoran, 3- (N-cyclohexyl-N-methylamino)
-6-methyl-7-anilinofluoran, 3-dimethylamino-6-methyl-7-chlorofluorane, 3-dimethylamino-7-methyl-7-chlorofluoran, 3-
Dimethylamino-6-methyl-7-anilinofluoran, 3,3-bis (4-dimethylaminophenyl) 6-
Diethylaminophthalide, 3-diethylamino-7 (2
-Chloroanilino) fluoran, 3-dibutylamino-
Fluoran dyes such as 7 (2-chloroanilino) fluoran; thiazine dyes such as benzoyl leucomethylene blue and p-nitribenzoyl leuconnetylene blue;
Spiropyrans such as -methyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran And lactam dyes such as rhodamine (p-nitroanilino) lactam and rhodamine (o-chloroanilino) lactam.

Further, in the present invention, as the binder for binding and supporting the heat-sensitive coloring layer on the support, the following various binders are applied.

Polyvinyl alcohol, starch and derivatives thereof, derivatives such as methylcellulose, hydroxymethylcellulose, carboxymethylcellulose and ethylcellulose, polyvinylpyrrolidone, polyacrylamide, sodium polyacrylate, acrylamide / acrylate copolymer, acrylamide / acrylate / Water-soluble polymers such as methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of isobutylene / maleic anhydride copolymer, sodium alginate, gelatin, casein, gum arabic, etc.
Aqueous emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, polymethacrylate, vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer, polybutyl methacrylate, etc. Can be used as

In the heat-sensitive recording material of the present invention, the above-mentioned leuco dye and the developer may be added in the heat-sensitive coloring layer, if necessary,
Auxiliary additives commonly used in this type of heat-sensitive recording material, such as fillers, surfactants and lubricants, can be used in combination.
In this case, as the filler, for example, calcium carbonate,
Inorganic fine powders such as silica, alumina, magnesium, talc, barium sulfate, zinc oxide, titanium oxide, surface-treated calcium and silica, as well as urea / formalin resin, styrene / methacrylic acid copolymer, and organic such as polystyrene System fine powder. As the lubricant, for example, in addition to higher fatty acids or their esters, amides or metal salts, various waxes, condensates of aromatic carboxylic acids with amines, benzoic acid phenyl esters, higher linear glycols, and other heat-fusible organic compounds Compounds. Add fine powder such as aluminum stearate to improve the clarity of the color image, and add lubricants such as linseed oil, tung oil, wax, paraffin, polyethylene wax, paraffin chloride, metal salts of higher fatty acids, etc. The traveling performance of the head can be further improved.

An overcoat layer can be provided on the recording layer for the purpose of protecting the recording layer and the like, and a protective layer can be provided on the back surface of the support or an under layer can be provided on the support. Of course, it is possible, and various known techniques in the field of thermal recording medium production, such as applying an adhesive treatment to the back surface of the support, can be added.

As a binder for forming the overcoat layer, for example, polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, casein, gum arabic, oxidized starch And etherified starch, esterified starch, styrene-butadiene copolymer emulsion, vinyl acetate-ethylene copolymer emulsion, methacrylate-butadiene copolymer, and styrene-acryl copolymer emulsion.

If necessary, a surfactant (dispersant, wetting agent) such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, alginate, fatty acid metal, etc. may be contained in the overcoat layer. Glyoxal, methylolmelamine, potassium persulfate, sodium persulfate,
Water-proofing agents such as ammonium persulfate and nitric acid, benzophanone-based and triazole-based ultraviolet absorbers, defoamers, various assistants such as fluorescent dyes and colored dyes, and the like can also be added.

A pigment may be added to such an overcoat layer in order to impart suitability for writing implements and fixability for printing. Such pigments include light calcium carbonate,
Heavy calcium carbonate, talc, kaolin, silicic acid, magnesium carbonate, clay, zinc oxide, aluminum oxide,
Examples include inorganic pigments such as aluminum hydroxide, organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formaldehyde resin filler, and raw starch.

As the support, paper is generally used, but it is also possible to use a resin film, synthetic paper, cloth or the like. It is also possible to provide an under layer on the support and between the heat-sensitive layer. As an apparatus used for coating the under layer and the heat-sensitive recording layer, a coater head such as a blade coater, an air knife coater, a roll coater, a rod coater, and a curtain coater can be used.

Further, in order to improve the surface smoothness of the coated product, an apparatus such as a machine calender, a super calender, a gloss calender, and a brushing can be used. In addition, the amount of coating when the under layer is provided is not particularly limited, but 3 to 20 g / m ^2, preferably 5 to 10 g / m ² is appropriate. The coating amount of the heat-sensitive recording layer on the support is not limited, but is usually 3 to 15 g.
/ M ^2, preferably in the range of 4 to 10 g / m ² .

[0022]

The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In addition, all the parts and% shown below are based on weight.

Example 1 [Adjustment of Intermediate Layer] Water 107 parts by weight 10% sodium hexametaphosphate 8 parts by weight Calcined kaolin (trade name: Ansilex manufactured by Engelhard Co.) 100 parts by weight 25% starch oxide solution 24 parts by weight 48% SBR latex 25 parts by weight An intermediate layer liquid having a solid content ratio of 45% was prepared from the above composition.

[Formation of Intermediate Layer]
50 g / m ² base paper with a coating amount of 6 with a blade coater
g / m ² and dried by application to form an intermediate layer.

[Adjustment of Thermosensitive Layer] (1) Adjustment of Liquid A Liquid A and Liquid B having the following component compositions were obtained by dispersing for 10 hours. 100% by weight of a 10% modified polyvinyl alcohol solution (Gosenol L3266, manufactured by Nippon Gosei Co., Ltd.) 100 parts by weight of 3-dibutylamino-6-methyl-7-anilinofluoran 150 parts by weight of water (Made by Enterprises) to a volume average of 1.5 μm. (2) Preparation of Solution B 15% styrene maleic anhydride copolymer ammonium salt 35 parts by weight 2,4'-dihydroxydiphenyl sulfone 40 parts by weight 2-benzyloxy-naphthalene 55 parts by weight N-methylol stearic acid amide 10 parts by weight 250 parts by weight of water Solution B was pulverized using a Dynomill (manufactured by Shinmaru Enterprises) to a volume average of 1.5 μm. (3) Preparation of solution C 15% styrene maleic anhydride copolymer ammonium salt 14 parts by weight 4-benzyloxy-4 ′-(2,3-epoxy-2-methylpropyl-1-yloxy) diphenylsulfone 40 parts by weight Part 46 parts by weight of water Liquid C was pulverized to 1.5 μm in volume average using a Dynomill (manufactured by Shinmaru Enterprises). (4) Preparation of Solution D 15% styrene maleic anhydride copolymer ammonium salt 35 parts by weight 4,4'-isopropylidene diphenol 40 parts by weight 2-benzyloxy-naphthalene 55 parts by weight N-methylol stearic acid amide 10 parts by weight Part 250 parts by weight of water Liquid D was pulverized to 1.5 μm in volume average using Dynomill (manufactured by Shinmaru Enterprises).

[Formation of heat-sensitive layer]
Using [Solution B] and [Solution C], a thermosensitive coloring layer coating solution comprising the following components was prepared, and a dry weight of 5% was formed on the under layer.
g / m ² with air knife coater 300m
/ Min. Thereafter, the coated paper was calendered and finished so that the Beck smoothness became 400 to 600 seconds, thereby obtaining a thermosensitive recording medium of Example 1. Polyvinyl alcohol solution (10% aqueous solution) 50 parts by weight Calcium carbonate 10 parts by weight Liquid A 10 parts by weight Liquid B 40 parts by weight Liquid C 1.5 parts by weight 40% zinc stearate dispersion 4 parts by weight Water 25 parts by weight

Example 2 Example 2 was performed in the same manner as in Example 1 except that the volume average of the particle size distribution was adjusted to 0.8 μm in the preparation of the liquid C of Example 1.
Was obtained.

Example 3 Example 3 was carried out in the same manner as in Example 1 except that the volume average of the particle size distribution was adjusted to 2.0 μm in the preparation of solution C of Example 1.
Was obtained.

Example 4 A heat-sensitive recording material of Example 4 was obtained in the same manner as in Example 1 except that the amount of the liquid C added in Example 1 was changed to 0.5 part by weight.

Example 5 A thermosensitive recording medium of Example 5 was obtained in the same manner as in Example 1 except that the addition amount of Solution C was changed to 2.8 parts by weight.

Example 6 [Preparation of overcoat liquid] Water 115 parts by weight 5% PVA 100 parts by weight 20% acrylic emulsion resin (trade name: OM1050 manufactured by Mitsui Toatsu Co., Ltd.) 50 parts by weight Fine silica powder (trade name: Mizusawa Chemical) Mizukasil P527) 10 parts by weight 40% zinc stearate dispersion 5 parts by weight

[Preparation of Overcoat Layer] The overcoat layer prepared above was coated on the heat-sensitive recording layer prepared in Example 1 with a rod coater so as to have a coating amount of 2 g / m ^2, and then dried. The paper was calendered and finished to a Beck smoothness of 700 to 1000 seconds.

Comparative Example 1 A thermosensitive recording medium of Comparative Example 1 was obtained in the same manner as in Example 1 except that the liquid C was not used in forming the heat-sensitive layer of Example 1.

Comparative Example 2 A heat-sensitive recording material of Comparative Example 2 was obtained in the same manner as in Example 1 except that Liquid D was used instead of Liquid B in forming the heat-sensitive layer of Example 1.

Comparative Example 3 A thermosensitive recording medium of Comparative Example 3 was obtained in the same manner as in Example 1 except that the volume average of the particle size distribution was adjusted to 0.65 μm in the preparation of the liquid C of Example 1.

Comparative Example 4 A thermosensitive recording medium of Comparative Example 4 was obtained in the same manner as in Example 1 except that the volume average of the particle size distribution was adjusted to 6.0 μm in the preparation of the liquid C in Example 1.

Comparative Example 5 A thermosensitive recording medium of Comparative Example 5 was obtained in the same manner as in Example 1 except that the amount of the liquid C added in Example 1 was changed to 0.3 part by weight.

Comparative Example 6 A heat-sensitive recording material of Comparative Example 6 was obtained in the same manner as in Example 1, except that the amount of the liquid C added in Example 1 was changed to 3.5 parts by weight.

Comparative Example 7 A thermal recording medium of Comparative Example 7 was obtained in the same manner as in Example 6, except that the thermal recording medium of Comparative Example 1 was used. The following items were evaluated for the above-mentioned heat-sensitive recording medium.

[Evaluation of Sensitivity] Using a tester manufactured by Okura Electric Co., Ltd., using a head having a head resistance of 1335Ω (manufactured by Kyocera), printing was performed at an energy of 0.25 mj / dot at 10 ms / Line, and the background and image at that time were printed. The print density of each part was measured, and the storage stability under all environmental conditions was evaluated. As a result, Tables 1 and 2 show Examples, and Table 3 shows Comparative Examples. The print density was measured using Macbeth RD918.

[Evaluation of Whiteness] The whiteness was measured according to JIS-
According to P8123, the reflectance was measured with an amber filter using a Hunter reflectometer. [Evaluation of whiteness after lapse of time]
% RH (Wet) and 60 ° C. · Dry,
It was left for 1, 3, 5, 10, 20, and 30 days, and the whiteness at that time was measured. The higher the value of whiteness, the better.

[Evaluation of plasticizer resistance] A diamond wrap was superimposed on the print sample surface of the print sample, and a load of 5 kg was further applied thereto. After standing at 25 ° C. and 65% for 24 hours, the density of the print portion was adjusted to Macbeth RD918. Measured.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

As shown in the table, in a thermosensitive recording paper containing a colorless or light-colored basic dye and a color developer capable of reacting with the dye to give a color, 2,4 'is used as the color developer. −
4-benzyloxy-4 ′-(2,3-epoxy-2-methylpropyl-1-yloxy) diphenylsulfone using dihydroxydiphenylsulfone and having a volume average particle size distribution adjusted to 0.8 to 2.0 μm The added heat-sensitive recording paper has extremely vivid color printability, high whiteness, little decrease in whiteness over time and under any environment, and minimizes decoloration of the printed area by a plasticizer after printing. It was a thermosensitive recording medium to be suppressed.

Claims (4)

[Claims] 1. A thermosensitive recording paper containing a colorless or light-colored basic dye and a color developer capable of reacting with the dye to form a color, wherein 2,4′-dihydroxydiphenyl sulfone is used as the color developer. And 4-benzyloxy-4 '
A heat-sensitive recording material comprising-(2,3-epoxy-2-methylpropyl-1-yloxy) diphenylsulfone. (2) 4-benzyloxy-4 ′-(2,3-
Epoxy-2-methylpropyl-1-yloxy) diphenylsulfone has a volume average particle size of 0.8 to 5.0 μm.
The heat-sensitive recording medium according to claim 1, wherein the heat-sensitive recording medium is adjusted to fall within the range of (3) 4-benzyloxy-4 ′-(2,3-
The amount of (epoxy-2-methylpropyl-1-yloxy) diphenylsulfone is 5 to 30% by weight of 2,4'-dihydroxydiphenylsulfone as the color developer. No thermal recording medium. 4. The thermosensitive recording medium according to claim 1, wherein at least one overcoat layer is provided on the thermosensitive recording layer.
The thermosensitive recording medium as described.