JPH0768940A - Heat-sensitive recording body - Google Patents

Abstract

PURPOSE:To provide a heat-sensitive recording body wherein a clear coloring image with an absorption region in near infrared part is obtd. and there exists no possibility of growing of fog of the skin even if it is kept under high temp. and high humidity and stability of the skin is excellent and furthermore, there exists no possibility that the fog of the skin grows with passage of time after a coating liq. is prepd. when a heat-sensitive coloring layer is formed and quality of the heat-sensitive coloring layer is good. CONSTITUTION:A heat-sensitive coloring layer formed on a substrate is a heat- sensitive recording body which consists of a coloring system of ferric salt of a fatty acid and incorporated with a chelate reagent and zirconium ammonium carbonate in the heat-sensitive coloring layer.

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 material to be subjected to heat recording, and in particular, a colored image having an absorption region in the near infrared region can be obtained, and there is no background fog and the storage stability of the background. (EN) A heat-sensitive recording material having excellent properties and having a constant quality.

[0002]

2. Description of the Related Art A thermosensitive recording medium has a substrate and a thermosensitive coloring layer formed on the substrate. A typical coloring system in the thermosensitive coloring layer is a leuco dye type.

The leuco dye-type thermosensitive coloring layer comprises a color-forming system comprising an electron-donating colorless or pale-colored leuco compound and an electron-accepting developer for coloring the leuco compound. Recording is performed by heating with a thermal head, a heating pen, a laser beam or the like, whereby the leuco compound in the thermosensitive color-developing layer and the developer are allowed to react instantaneously to form a recorded image (for example, Japanese Patent Publication No. 43-4
No. 160, Japanese Patent Publication No. 45-14039, etc.).

The heat-sensitive recording material used for heat-sensitive recording is not limited to the case of the above-mentioned leuco dye-type heat-sensitive color developing layer, but generally, a recorded image can be obtained by a relatively simple apparatus and maintenance is easy. In addition, there is an advantage that no noise is generated during operation. For example, a recorder for measurement,
It is used in a wide range of fields such as facsimiles, printers, computer terminals, labels, and vending tickets for transportation.

In particular, heat-sensitive recording labels are used in application fields that require sticking after printing, such as bar code labels for POS (point-of-sale information) systems, price display labels, and shipping / shipping labels. It is widely used in large-scale mass retailers such as supermarkets and department stores, as well as specialty stores and restaurants that are developing chains.

In this POS system, a method of optically reading a displayed bar code or OCR character with a scanner is rapidly spreading.

At present, various printing methods have been attempted for labels for POS systems. Among them, the thermal recording method utilizing a thermal recording medium is a printing method in which the printing method chemically or physically Since the image is formed by utilizing the change, it has various merits such as no need for steps such as development and fixing, and no need for supplementation of printing ink.

Further, in the thermal recording system, the machine can be downsized, simplified, and the recording speed can be increased, and there is no fear that the fingertips or products will be stained with ink.
It also has the advantage that the colored image does not have ink fading.

By the way, in reading a bar code or the like by a color image obtained by the thermal recording system, it is 633 conventionally.
He / Ne laser light having red light with a wavelength of nm has been used, but recently, semiconductor laser light has been used.

This semiconductor laser light can be directly modulated by an electric current, and the size of the device can be reduced.
It is easy to use, supplied at a low price, and has an oscillation wavelength of 700.
Since it is located in the near-infrared region of ˜1500 nm, it has advantages such as less malfunction due to dirt, and is becoming widely used.

Therefore, in recent years, there has been an increasing demand for a heat-sensitive recording material capable of obtaining a color image which can be read by a semiconductor laser beam.

However, a heat-sensitive recording material having a two-component type heat-sensitive color developing layer containing a leuco compound and a color developer, which have been conventionally used, has an absorption wavelength of a color image even in a black color system. 550 to 620 even on the long wavelength side
However, it is possible to read with a He / Ne laser beam, but it is impossible to read with a semiconductor laser beam in the near infrared region having an oscillation wavelength of 700 to 1500 nm.

On the other hand, as a thermosensitive recording medium utilizing a mechanism in which one or both of the components in the thermosensitive color developing layer are melted and reacted to form a chelate compound, a color is formed from an organic acid heavy metal salt or an organic acid noble metal salt. With one component,
A coloring system is known which is combined with a chelating reagent which is the other component composed of one of an organic reducing agent, a sulfur compound and an amino compound.
A thermosensitive coloring layer utilizing a coloring system composed of a combination of a fatty acid iron salt and a polyhydric phenol, a combination of a fatty acid iron salt and a dithiocarbamate salt, etc. is known.

In the heat-sensitive recording material having this heat-sensitive color developing layer, a color image which can be read by a semiconductor laser beam can be obtained by selecting a chelating reagent used for the heat-sensitive color developing layer.

However, the conventional thermosensitive recording medium utilizing the coloring mechanism associated with the formation of this kind of chelate compound has a drawback that the fog is apt to occur in the thermosensitive coloring layer containing the chelating agent.

This background fog in the thermosensitive coloring layer is
(1) When the thermal recording medium is stored in an atmosphere of high temperature and high humidity, (2) When the thermal recording medium is exposed to light for a long period of time, (3) Coating when forming the thermal recording layer After the preparation of the liquid, a time elapses until the heat-sensitive recording layer is formed by the coating liquid, so that the color development occurs in the coating liquid over time, for example.

Therefore, the present inventors have found that the specific fatty acid second
By using a combination of an iron salt and a chelating agent, it is possible to improve the background fog in the cases of (1), (2) and (3) above, and to coat the thermosensitive recording layer. It was proposed that the fog in the case of the above (3) can be improved by adjusting the pH of the liquid.

Although the background fog in the thermosensitive color developing layer is improved by such technical means, a thermosensitive recording material having a more stable quality is required.

[0019]

On the other hand, the present invention provides a heat-sensitive recording material capable of obtaining a clear color image having an absorption wavelength in the near infrared region, especially when it is stored under high temperature and high humidity. Less occurrence, excellent storage stability of the background, moreover, even after a lapse of time after adjustment of the coating liquid when forming the thermosensitive color developing layer, the coloring reaction does not occur in the coating liquid and fogging does not occur. (EN) Provided is a thermosensitive recording medium having no variation in the quality of the thermosensitive coloring layer.

[0020]

According to the invention of claim 1, the thermosensitive coloring layer formed on the substrate comprises a coloring system of a ferric fatty acid ferric salt and a chelating agent, and the thermosensitive coloring layer comprises: It is composed of a thermosensitive recording medium to which ammonium zirconium carbonate is added.

According to a second aspect of the present invention, in the heat-sensitive recording material according to the structure of the first aspect, the heat-sensitive recording material uses polyhydric phenol and / or dithiocarbamate as a chelating agent.

The inventors of the present invention have mentioned the above-mentioned drawbacks in the heat-sensitive recording material which utilizes the color-forming mechanism associated with the formation of the chelate compound.
That is, when using a material that has passed a time after adjustment of the coating liquid for forming the heat-sensitive recording layer, the heat-sensitive recording material has a background fog, and heat-sensitive when stored in a high temperature and high humidity atmosphere. The drawbacks such as the occurrence of background fog on the recording material are solved by adding zirconium ammonium carbonate in the thermosensitive coloring layer in the thermosensitive recording layer comprising a coloring system of a ferric acid fatty acid salt and a chelating agent. They have found that they can do so and have completed the present invention.

The heat-sensitive color forming layer of the heat-sensitive recording material of the present invention having the above-mentioned constitution is a substrate in the heat-sensitive recording material, for example, paper, various non-woven fabrics, plastic film, synthetic paper, metal foil, etc.
Alternatively, an aqueous dispersion containing a ferric acid ferric salt forming a coloring system and a chelating agent, ammonium zirconium carbonate, and a water-soluble or water-dispersible binder is added to a substrate composed of a composite sheet or the like in which these are combined. It is obtained by forming a coating layer with a system coating liquid.

Specific examples of the fatty acid ferric iron salt used in the heat-sensitive color forming layer include a linear or branched saturated fatty acid or unsaturated fatty acid having 6 to 25 carbon atoms, preferably 9 to 22 carbon atoms.
An iron salt, more specifically a ferric stearate salt,
Examples include ferric myristic acid, ferric behenic acid, ferric lauric acid, ferric pelargonic acid, and the like.

Particularly, the height (H) of the main peak and the peak half value width (W) existing within the range of the diffraction angle (2θ) of 21.8 ± 0.5 degrees in the X-ray diffraction analysis curve with Cu-Kα ray. ) And the ratio (H / W) is 10 or more, and
The main endothermic peak in the differential thermal analysis curve is 100
A ferric fatty acid ferric salt composed of a ferric stearate salt, a ferric behenate salt, or a mixture thereof having a high crystallinity and having a temperature of not less than 0 ° C. is preferable.

The chelating reagent used for the thermosensitive coloring layer is
Examples thereof include polyhydric phenol, dithiocarbamate, diphenylcarbazone, hexamethylenetetramine, spirobenzopyran, 1-formyl-4-phenylsemicarbazide. These chelating reagents form chelate compounds with ferric fatty acid ferric salts.

Since the chelate compound of the fatty acid ferric iron salt and the chelating agent has absorption in the near infrared region, the thermosensitive coloring layer of the thermosensitive recording material of the present invention can form a colored image readable by a semiconductor laser. Is formed.

As the chelating agent, polyhydric phenol and / or dithiocarbamate are preferable, and among them,
As the polyhydric phenol, gallic acid ester, dihydroxybenzoic acid ester, and the like are most suitable, and those exemplified below are used as the chelating reagent.

Gallic acid ester; general formula C ₆ H ₂ (O
H) ₃ (COOR), a gallic acid ester in which R is an alkyl group having 1 to 28 carbon atoms, a phenyl group or a benzyl group and derivatives thereof, for example, methyl gallate, propyl gallate, octyl gallate, gallic acid Lauryl, cetyl gallate, stearyl gallate, behenyl gallate, etc.

Dihydroxybenzoic acid ester; (1) 2,4-dihydroxybenzoic acid propyl ester (2) 2,4-dihydroxybenzoic acid butyl ester (3) 2,4-dihydroxybenzoic acid cyclohexyl ester (4) 2,4 -Dihydroxybenzoic acid benzyl ester (5) 2,4-dihydroxybenzoic acid-p-methylbenzyl ester (6) 2,4-dihydroxybenzoic acid-p-chlorobenzyl ester (7) 2,4-dihydroxybenzoic acid-α -Phenylethyl ester (8) 2,4-dihydroxybenzoic acid-β-phenylethyl ester (9) 2,4-dihydroxy-6-methylbenzoic acid ethyl ester (10) 2,4-dihydroxy-6-methylbenzoic acid Propyl ester (11) 2,4-dihydroxy-6-isopropylbenzoic acid ethyl ester (12) 2,4-dihydroxy ester Droxy-6-pentylbenzoic acid ethyl ester (13) 2,4-dihydroxy-6-methoxybenzoic acid butyl ester (14) 2,4-dihydroxy-6-methylbenzoic acid cyclohexyl ester (15) 2,4-dihydroxy- 6-Methylbenzoic acid benzyl ester (16) 2,4-dihydroxy-6-propylbenzoic acid-p
-Chlorobenzyl ester (17) 2,4-dihydroxy-6-methoxybenzoic acid-p
-Methylbenzyl ester (18) 2,4-dihydroxy-6-methylbenzoic acid-p-
Isopropylbenzyl ester (19) 2,4-dihydroxy-6-methylbenzoic acid-p-
Methylphenoxyethyl ester (20) 2,4-dihydroxy-5-chlorobenzoic acid-p-
Chlorobenzyl ester (21) 3,4-dihydroxybenzoic acid butyl ester (22) 3,4-dihydroxybenzoic acid benzyl ester (23) 3,4-dihydroxybenzoic acid-β-phenylethyl ester (24) 3,4- Dihydroxy-5-chlorobenzoic acid benzyl ester (25) 3,4-dihydroxybenzoic acid-α-phenylethyl ester

(1) sodium dibutyldithiocarbamate (2) copper dimethyldithiocarbamate (3) ferric dimethyldithiocarbamate (4) tellurium diethyldithiocarbamate (5) zinc butylxanthogenate (6) dibutyldithiocarbamate Zinc (7) N-Ethyl-N-phenyldithiocarbamate (8) Zinc dibenzyldithiocarbamate (9) Zinc N-pentamethylenedithiocarbamate (10) Sodium dimethyldithiocarbamate (11) Sodium diethyldithiocarbamate (12) Penta Methylenedithiocarbamic acid piperidine salt (13) Pipecolyl dithiocarbamic acid pipecoline salt (14) Zinc dimethyldithiocarbamate (15) Zinc diethyldithiocarbamate

The water-soluble or water-dispersible binder used for forming the thermosensitive coloring layer includes various starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, and styrene-anhydrous. Water-soluble binders such as water-soluble binders such as maleic acid copolymers and ethylene-maleic anhydride copolymers, and styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, acrylic ester-butadiene copolymers, etc. It is a binder.

The zirconium ammonium carbonate added to the heat-sensitive color forming layer of the heat-sensitive recording material of the present invention reacts with the above water-soluble or water-dispersible binder to improve the water resistance of the heat-sensitive color forming layer. Also has.

In the coating liquid for forming the thermosensitive coloring layer, as a pigment, diatomaceous earth, clay, calcined clay, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, alumina. Inorganic pigments such as aluminum hydroxide, synthetic magnesium silicate and synthetic aluminum silicate, and organic pigments such as polystyrene, polymethacrylic acid ester, urea resin and urea-formalin resin may be added.

Further, for the purpose of preventing head wear and sticking, higher fatty acid metal salts such as zinc stearate and calcium stearate, and waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearic acid amide and castor wax are used. ,Also,
Various oxalic acids such as metaterphenyl, parabenzylbisphenyl, esters of hydroxynaphthoic acid, stearic acid amide, tribenzylamine, naphthalene derivative, dibenzyl terephthalate, dibenzyl oxalate, bis (paramethylbenzyl oxalate), etc. You may add ester etc.

Further, a dispersant such as sodium dioctylsulfosuccinate, a UV absorber such as a benzophenone type or a benzotriazole type, a surfactant, a fluorescent dye and the like may be added, if desired.

In the heat-sensitive recording layer of the heat-sensitive recording material of the present invention,
The aforementioned zirconium ammonium carbonate is a solid component of 0.
It is sufficient if it is added in a proportion of from 05 to 10% by weight, and if it is less than 0.05% by weight, the effect of addition of ammonium zirconium carbonate is not remarkable, and if it exceeds 10% by weight, the recording density of the heat-sensitive recording layer is increased. Occurs.

The coating solution for forming the thermosensitive recording layer is prepared in substantially the same manner as the conventional coating solution for forming the leuco dye type thermosensitive coloring layer.

Specifically, a sand grinder, an attritor, a ball mill, etc. are separately provided for each of an aqueous dispersion containing a ferric fatty acid as a main component and an aqueous dispersion containing a chelating agent as a main component. After using the obtained solution, a method of adding an aqueous solution of ammonium zirconium carbonate to either or both of these solutions and mixing them, or
This can be adjusted by, for example, adding an aqueous zirconium carbonate carbonate solution after mixing an aqueous dispersion containing a ferric fatty acid as a main component with an aqueous dispersion containing a chelating agent as a main component.

The heat-sensitive recording material of the present invention having the above constitution is
It is also used for ordinary applications such as facsimiles and printers, as well as special applications for detecting near-infrared light. By forming a protective layer that covers the thermosensitive coloring layer, especially when high storability of colored images is desired. It is preferable to protect the uncolored part and the colored image part from the external environment.

As the main component of the protective layer, various water-soluble resins, latexes, ionizing radiation curable resins by ultraviolet rays or electron beams, etc. are used, and further, if necessary, pigments, water-proofing agents and repellants. A water solution, a defoaming agent, an ultraviolet absorber, etc. can be added.

[0042]

EXAMPLES The specific constitution of the heat-sensitive recording material of the present invention will be described based on manufacturing examples, and various characteristics of the heat-sensitive recording material will be described in comparison with the heat-sensitive recording material of the comparative example.

Example 1 The following composition (A) and composition (B) were separately dispersed by a sand grinder to prepare a solution (a) according to the composition (A) and a solution (b) according to the composition (B). (A) liquid 1 after obtaining
20 parts by weight, 200 parts by weight of the solution (b) and 50 parts by weight of a 12% by weight aqueous solution of polyvinyl alcohol were mixed and stirred to obtain a solution (c).

Subsequently, an aqueous zirconium carbonate solution having a solid content concentration of 13% "Zircosol AC-7 (trade name) manufactured by Daiichi Rare Element Chemical Industry Co., Ltd." was used as a solid component in the solution (c) of zirconium ammonium carbonate. Was added so as to be a ratio of 1.0% by weight to obtain a coating liquid (1) for forming a thermosensitive coloring layer.

Composition (A) ferric stearate: 10 parts by weight clay: 20 parts by weight Polyvinyl alcohol 12% by weight solution ... 40 parts by weight Water ... 50 parts by weight

Composition (B) Stearyl gallate: 40 parts by weight Clay: 20 parts by weight 12% by weight polyvinyl alcohol solution 70 parts by weight water 70 parts by weight

Subsequently, a coating liquid (1) for forming a thermosensitive coloring layer
Immediately after adjusting the value, a Beck smoothness can be obtained by applying a coating amount of 7 g (dry) / m ² on a substrate made of high-quality paper of 50 g / m ² , drying, and further performing a calendering treatment. A thermosensitive recording medium (a) which is an example product of the present invention having a thermosensitive coloring layer for 500 seconds was obtained.

Example 2 The coating liquid (1) for forming a thermosensitive color developing layer prepared in the same manner as in Example 1 was allowed to stand in an atmosphere at 30 ° C. for 24 hours, and then it was treated with 50 g / m ² of high quality. It was applied on a substrate made of paper in the same manner as in Example 1, and in the same manner as in Example 1 below, a thermosensitive recording medium (b) which was an example product of the present invention was obtained.

Example 3 The coating liquid (1) for forming a thermosensitive color-developing layer prepared in the same manner as in Example 1 was allowed to stand in an atmosphere of 30 ° C. for 48 hours, and then it was treated with 50 g / m ² of high quality. The heat-sensitive recording material (C), which is an example product of the present invention, was obtained by applying the composition on a substrate made of paper in the same manner as in Example 1 and in the same manner as in Example 1.

Comparative Example 1 Immediately after preparing the liquid (c) during the manufacturing process of the thermosensitive recording medium (a) of Example 1, the liquid (c) was immediately applied onto a substrate made of high-quality paper of 50 g / m ^2. It was applied in the same manner as in Example 1 and the same procedure as in Example 1 was followed to obtain a thermosensitive recording medium (D) for comparison.

Comparative Example 2 The liquid (c) of Comparative Example 1 was allowed to stand in an atmosphere of 30 ° C. for 24 hours, and then applied on a substrate made of high-quality paper of 50 g / m ^{2 in} the same manner as in Comparative Example 1. Then, a thermal recording material (e) for comparison was obtained in the same manner as in Comparative Example 1.

Comparative Example 3 The liquid (c) of Comparative Example 1 was allowed to stand in an atmosphere of 30 ° C. for 48 hours, and then applied on a substrate made of high-quality paper of 50 g / m ^{2 in} the same manner as in Comparative Example 1. Then, a thermal recording material (f) for comparison was obtained in the same manner as in Comparative Example 1.

[Evaluation 1] Examples 1 to 3 and Comparative Examples 1 to 3
The magnetic densitometer Macbeth R was used to determine the background density and the color density (image density) of printing of each of the thermosensitive recording materials (a) to (f) obtained in
It was measured using D918.

Printing on each thermal recording medium is carried out by the thermal printer "DPU-41" manufactured by Seiko Denshi Kogyo KK
2 ". The results are shown in [Table 1].

[0055]

[Table 1]

[Evaluation 2] The thermosensitive recording media of Examples 1 to 3 and Comparative Examples 1 to 3 printed by the formulation of [Evaluation 1] were stored in an atmosphere of 50 ° C. and 80% RH for 24 hours, and then, The background density of the thermal recording material and the color density (image density) of the print were measured in the same manner as in [Evaluation 1]. The results are shown in [Table 2].

[0057]

[Table 2]

[0058]

[Effect] Since the thermosensitive recording material of the present invention records a clear colored image having an absorption region in the near infrared region, it can be read by a semiconductor laser beam, and a coating liquid for forming a thermosensitive coloring layer. When a thermosensitive coloring layer is formed using a material that has passed a certain time after adjustment, or when the thermosensitive recording medium is stored in a high-humidity atmosphere, there is no background fog and the thermal recording medium has uniform quality. For example, it is highly practical as a thermal recording material in the field of thermal recording labels, etc., and has a high utility value.

Claims (2)

[Claims] 1. A thermosensitive coloring layer formed on a substrate,
A thermosensitive recording medium comprising a coloring system of a ferric acid fatty acid salt and a chelating agent, and ammonium zirconium carbonate being added to the thermosensitive coloring layer. 2. The thermosensitive recording medium according to claim 1, wherein the chelating agent is a polyhydric phenol and / or a dithiocarbamate.