JPH05318906A - Sheet for multicolor recording thermal label - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a sheet for a multi-color recording thermal label capable of multi-color recording. [Structure] A release paper is attached to one side of a support through a pressure-sensitive adhesive layer, and an organic basic compound and a dye precursor A, a phenolic substance or an organic substance that develops a color when heated by the organic basic compound on the other side of the support. An acid and a dye precursor B that develops a color when heated by them, and a multi-color thermosensitive coloring layer having a single layer or more containing an adhesive as a main component,
A multi-color recording thermosensitive label sheet laminated with an overcoat layer, the multicolor thermosensitive coloring layer having a color development start temperature of 85 to 110 ° C.
It is what In particular, it is preferable to provide an undercoat layer composed mainly of a pigment and an adhesive between the thermosensitive coloring layer and the support. [Effect] It is possible to obtain a multi-color recording heat-sensitive label sheet having good recording storability and heat resistance, and having a vivid contrast in the coloring hue.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive label sheet, and more particularly to a multi-color record heat-sensitive label which is capable of multicolor recording with vivid contrast and has excellent heat resistance on the background portion and good storage stability. It is related to the sheet.

[0002]

2. Description of the Related Art Recently, a thermal recording system is often used for bar code labels for POS (point-of-sale information) systems, price display labels, and other applications such as delivery, product classification patches, stamps and postal stickers. ing. The reason is that the printing method obtains a color image by a momentary chemical reaction due to heat, and has advantages such as a small device, high recording speed, low noise and environmental pollution, and low cost. .. However, depending on the intended use, there are data and characters to be clearly displayed, and description items to be distinguished from others, and in those cases, multicolor recording having a vivid contrast is required. Therefore, a heat-sensitive label sheet having a high-temperature and low-temperature color-developing layer that develops different color tones with different coloring heat energy has been developed. It is 2
Divided into types. One of them is a so-called color mixture system, which obtains a single color by heating at a low temperature and a color mixture at a high temperature (JP-A-48-15540).
JP-A-49-4342, JP-A-49-6
No. 5239), the other is a so-called decoloring system in which a color tone close to a single color is obtained by using a decoloring agent for decoloring the low temperature coloring layer when high temperature coloring is performed (Japanese Patent Application Laid-Open No. 48-8251). , JP-A-51-37542 and JP-A-53-47.
843, JP-A-55-139290, JP-A-55-161688). However, in the case of a mixed color system, the hue developed at low temperature is light, and the hue developed at high temperature is limited to colors with low lightness and saturation. On the other hand, the decoloring system is advantageous over the color mixing system because it has an advantage that a color combination can be freely selected and that black type printing, which is frequently used, can be colored at a low temperature.

Further, as the quality required for the heat-sensitive label sheet, (1) the coating layer is not peeled off even when wet with water and the recorded portion is clear, and (2) edible oil, hand cream, hair styling agent. And the like, and the recorded part is clear even after prolonged contact with a packaging film containing a plasticizer. To meet these demands, it has been greatly improved by using a specific adhesive, water resistant agent, water repellent, etc. in the thermosensitive coloring layer, and by providing a layer mainly composed of a specific polymer compound on the surface of the thermosensitive coloring layer. To be done. However, as a further required quality, there is almost no background coloration even in applications such as food labels used in microwave ovens and refrigerators, industrial labels attached to machines that reach high temperatures, etc., and the recording section can be read. Is required. As a method of improving these characteristics, measures have been taken to raise the static color development start temperature by selecting the components of the thermosensitive color development layer, but much energy is required to develop the color to a practically usable concentration. Therefore, in the case of a multi-color recording heat-sensitive label, the low-temperature color development temperature rises, the decoloring agent partially dissolves and inhibits color development, resulting in a decrease in color density or inferior color vividness.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multicolor recording heat-sensitive label sheet which has good recording storability and heat resistance, and has a vivid contrast in color hue.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the multicolor recording heat-sensitive label sheet of the present invention has a pressure-sensitive adhesive layer on one side of a support. An organic basic compound, a dye precursor A capable of being colored by heat with the organic basic compound, a phenolic substance or an organic acid, the phenolic substance or an organic substance is attached to the other surface of the support through a release paper. Dye precursor B capable of developing a color when heated with an acid, a single-layer or two or more multicolor heat-sensitive coloring layer appropriately combined with an adhesive as a main component, and an overcoat layer mainly containing an aqueous polymer compound are sequentially laminated. Is a sheet for a multicolor recording heat-sensitive label, which is formed on the surface of the multicolor recording color-developing layer at a pressure of 500 g / cm ² using a thermal gradient tester.
The temperature at which the optical density when applied for 2 seconds reaches 0.2 is the color formation start temperature, and the color formation start temperature on the surface of the multicolor thermosensitive coloring layer is 85 to 110 ° C.

Further, the multicolor recording heat-sensitive label sheet of the present invention comprises an undercoat layer containing an inorganic or organic pigment and an adhesive as main components between the support and the multicolor heat-sensitive coloring layer.

In the present invention, the color development start temperature is a specific temperature by a thermal gradient tester, and a pressure of 500 g / cm ² is applied to the surface of the multicolor thermosensitive color developing layer for 5 seconds to obtain a Macbeth densitometer RD-514 (filter W- At 106), the optical density of the application section is measured, and the temperature at which the value reaches 0.2 is called the color development start temperature.

The color formation starting temperature of the multicolor thermosensitive coloring layer is 85 to
If it is 110 ° C, there is no problem in discoloration of the background even when stored at high temperature, and the print density of low temperature color development in actual use is sufficient,
The hue contrast with the high temperature color is also clear. on the other hand,
If the temperature is lower than 85 ° C., the background portion is colored when stored at a high temperature, and so-called background fogging occurs. If it exceeds 110 ° C., the printing density of low-temperature color development in actual use is low, and it is still insufficient to provide an undercoat layer between the multicolor thermosensitive color development layer and the support.
Even if the applied energy is increased, the print density does not increase due to the effect of the decoloring agent, and the contrast of the hue with the high temperature coloring becomes unclear.

As the release paper of the present invention, for example, paper whose surface is treated with a release agent such as silicone resin is generally used, but the base is synthetic paper or synthetic resin film in addition to paper. Etc. can be used.

Examples of pressure-sensitive adhesives include styrene / butadiene block copolymers, styrene / isoprene block copolymers, natural rubber latex, isobutylene latex, polyvinyl alcohol, polyvinyl acetate,
Examples thereof include acrylic emulsions such as polyacrylic acid.

Between the pressure-sensitive adhesive and the support, polyvinyl alcohol, styrene / maleic anhydride copolymer, styrene / butadiene block copolymer, polyacrylamide, hydroxymethyl cellulose, starch, or derivatives thereof are mainly used. You may provide the coating layer which consists of a high molecular compound used as a component.

The organic basic compound used in the heat-sensitive recording layer of the present invention, the dye precursor A which can be colored by the organic basic compound, the phenolic substance or the organic acid, and the dye formed by the phenolic substance or the organic acid. Specific examples of the dye precursor B and the adhesive that can be used are as follows.
These do not limit the invention.

Although the guanidine derivative is excellent as the organic basic compound of the present invention, other than that, phenylthiourea, hexadecylamine, tribenzylamine,
Decamethylenediamine, 2-aminobenzoxazole, 2-aminobenzimidazole, quinine, cyclohexylbenzylamine, octadecylbenzylamine and the like can be used. Guanidine derivatives include 1,3-diphenylguanidine and 1,3-dicyclohexyl-2-
Phenylguanidine, 1,3-dicyclohexyl-2
(2 ', 4'-Dimethyl) phenylguanidine, 1,3
-Dicyclohexyl-2 (2 ', 5'-dimethoxy) phenylguanidine, 1,3-dicyclohexyl-2-cyclohexylguanidine, etc.
No. 5,196, page 11, column 21, line 40 to line 16
Those described in page 31, column 33 line can be used.

The dye precursor A which is colored by the organic basic compound of the present invention includes a pH indicator, a fluorescein derivative, a phenolphthalein derivative, and a change in pH value toward the alkaline side, which are alkaline and cause coloration or color change. Therefore, a substance such as a ninhydrin derivative or the like that causes a discoloration phenomenon by being oxidized or reduced in a broad sense is used. Specifically, 2,4,5,7-tetrabromofluorescein, 3,4,5,6-tetrachlorofluorescein,
3,6-diacetyloxyfluorane, 1,8-dimethylfluorescein, etc.
Those described in the description of page 96, page 3, column 6, line 22 to page 10, page 20, column 20, line 21 can be used.

The phenolic substances or organic acids of the present invention include 4,4'-isopropylidenediphenol, 4,4'-isopropylidenebis (2-chlorophenol) and 4,4'-isopropylidenebis (2). -Tert-butylphenol), 4,4'-secondary butylidene diphenol, 4,4 '-(1-methyl-normal-hexylidene) diphenol, 4-phenylphenol, 4-hydroxydiphenol, methyl-4-
Hydroxybenzoate, phenyl-4-hydroxybenzoate, 4-hydroxyacetophenone, salicylic acid anilide, 4,4'-cyclohexylidene diphenol, 4,4'-cyclohexylidenebis (2-methylphenol), 4,4'- Benzylidene diphenol,
4,4'-thiobis (6-tersialybutyl-3-methylphenol), 4,4'-isopropylidenebis (2-methylphenol), 4,4'-ethylenebis (2-methylphenol), 4, 4'-cyclohexylidene bis (2-isopropylphenol), 2,2'-
Dihydroxydiphenyl, 2,2'-methylenebis (4
-Chlorophenol), 2,2'-methylenebis (4-
Methyl-6-t-butylphenol), 1,1′-bis (4-hydroxyphenol) -cyclohexane, 2,
2'-bis (4'-hydroxyphenyl) propane, novolac type phenol resin, halogenated novolac type phenol resin, α-naphthol, β-naphthol, 3,
5-di-t-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 3-methyl-5-t-butylsalicylic acid, monoanilide paraethoxybenzoic acid phthalate, bis (4-hydroxyphenyl) sulfone, 4-
Hydroxy-4′-isopropyloxydiphenyl sulfone, di- (3-allyl-4-hydroxyphenyl)
Sulfone, 4-hydroxy-4′-benzyloxydiphenyl sulfone, 4-hydroxy-4′-t-octyloxydiphenyl sulfone, parabenzyloxybenzoic acid, parahydroxybenzoic acid benzyl ester and the like are used.

Examples of the dye precursor B which is colored by the phenolic substance or the organic acid of the present invention include crystal violet lactone, 3-indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide and 3-diethylamino-7. -Chlorofluorane, 3-diethylamino-7-cyclohexylaminofluorane, 3-diethylamino-5-methyl-7-t-butylfluorane, 3
-Diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-p-butylanilinofluorane, 2- (N-phenyl-N-ethyl) aminofluorane, 3-diethylamino -7-Dibenzylaminofluorane, 3-cyclohexylamino-
6-chlorofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 2-anilino-3-methyl-6- (N-ethyl-p-toluidino) fluorane, 3-pyrrolidino-6-methyl- 7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-piperidino-6-methyl-7-toluidinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3 -(N-methylcyclohexylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-
Dibutylamino-6-methyl-7-anilinofluorane or the like is used.

Examples of the adhesive of the present invention include starches such as oxidized starch, phosphoric esterified starch and etherified starch, hydroxyethyl cellulose, methylene cellulose, polyvinyl alcohol, styrene-acryl, polyacrylamide, carboxymethyl cellulose, gum arabic, Water-soluble binders such as casein, or derivatives thereof, and latexes such as styrene-butadiene latex are used.

Pigments used in the multicolor thermosensitive coloring layer of the present invention include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide,
Examples thereof include zinc oxide, silicon oxide, aluminum hydroxide, and urea-formalin resin. Moreover, you may use together these pigments 1 or more types. Other additives include higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, oxidized paraffin, polyethylene,
Waxes such as polyethylene oxide, wetting agents such as dioctyl sulfosuccinate, UV absorbers such as benzophenone and benzotriazole, surfactants, fluorescent dyes and the like are used.

As the main component of the overcoat layer of the multicolor thermosensitive coloring layer of the present invention, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic amide, carboxymethyl cellulose, hydroxyethyl cellulose, styrene-butadiene polymer, etc., or derivatives thereof are used. Can be mentioned.

As the support used in the present invention, paper is used, and synthetic paper, metal foil, laminated paper of polyethylene or the like, film of polyethylene terephthalate or the like is used alone, or a sheet obtained by combining them is used. You can also do it.

An undercoat layer may be provided on the support used in the present invention. The main components of the undercoat layer are inorganic or organic pigments and adhesives. Hollow resin particles such as styrene-acrylic resin, which is an organic pigment, are particularly preferable as the pigment. or,
As the adhesive, the one used in the above-mentioned multicolor thermosensitive coloring layer can be used.

In the multicolor recording heat-sensitive label sheet of the present invention, the coating amount of each coating layer is not particularly limited. However, as the multicolor thermosensitive coloring layer, if the black color density at 120 ° C. is an optical density of 0.9 or more and the red color density at 160 ° C. is an optical density of 0.7 or more, there is no problem in actual use. The coating amount may be appropriately adjusted as a reference. The overcoat layer preferably has a dry solid content of 0.5 to 10 g / m ² . Further, the undercoat layer preferably has a dry solid content of ² to 15 g / m ² .

The apparatus used for coating the undercoat layer, the multicolor thermosensitive coloring layer, the overcoat layer, etc. of the present invention is an air knife coater, a gravure coater, a roll coater,
A rod coater, a curtain coater, a die coater, a lip coater, a blade coater, etc. are used. Particularly in the case of the undercoat layer, a size press device, a gate roll device or the like used in the paper making process of paper is also used.
Also, printing methods such as offset and silk screen are used. Further, in order to improve the surface smoothness of the coated product, machine calender, super calender, gloss calender, brushing and the like are used.

[0024]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.
The parts and% in the examples mean parts by weight and% by weight.

Example 1 (1) Preparation of Undercoat Paper An undercoat coating solution was prepared by stirring and dispersing the following liquids to prepare a base paper having a basis weight of 70 g / m ² and a coating amount after drying. The undercoat paper (a) was obtained by coating and drying so that the amount was 6 g / m ² . Undercoat coating liquid: calcined kaolin (Engelhard, Ansilex) (solid) 100 parts Acrylic dispersant 10% aqueous solution (solid) 0.5 part Oxidized starch 20% aqueous solution (solid) 10 parts Styrene-butadiene latex 48% aqueous dispersion (solid) 10 parts Water (solid) 80 parts

(2) Preparation of coating solution for multicolor heat-sensitive recording layer Solution A, solution B, solution C and solution D having the following formulations are separately pulverized for 3 hours with a sand grinder. Solution A: 3-diethylamino-6-methyl-7-anilinofuriolane (solid) 100 parts Styrene-maleic anhydride copolymer salt 25% aqueous solution (solid) 5 parts Water 150 parts Solution B: 4-hydroxy-4 '-Isopropyloxydiphenyl sulfone (solid) 100 parts Styrene-maleic anhydride copolymer salt 25% aqueous solution (solid) 5 parts Water 150 parts C liquid: 2,4,5,7-tetrabromofluorescein (solid) 100 parts Hydroxyethyl cellulose 5% aqueous solution (solid) 5 parts Water 200 parts Liquid D: 1,3-dicyclohexyl-2-phenylguanidine (solid) 100 parts Hydroxyethyl cellulose 5% aqueous solution (solid) 5 parts Water 200 parts

A coating solution for a thermosensitive recording layer was prepared using the solutions A, B, C, and D obtained above. (3) Thermosensitive recording undercoat layer liquid D: 10 parts Hydroxyethyl cellulose 10% aqueous solution 10 parts Water 10 parts The above thermosensitive recording undercoat layer liquid was applied to undercoat paper (a).
Was coated and dried so that the coating amount after drying was 4 g / m ² to obtain a heat-sensitive recording undercoat paper (b).

(4) Thermosensitive recording topcoat layer liquid Calcined kaolin (Engelhard, Ansilex) (solid) 20 parts A liquid 4 parts B liquid 15 parts C liquid 6 parts Styrene-maleic anhydride 25% aqueous solution 20 parts Water 60 parts The above thermosensitive recording overcoat layer liquid was added to thermosensitive recording undercoat paper (b).
On the above so that the coating amount after drying is 7 g / m ² .
It was dried to obtain a multicolor recording thermal paper (C).

(5) Overcoat Liquid Calcium Carbonate (Brt15 manufactured by Shiraishi Industry Co., Ltd.) (solid) 8 parts Polyvinyl alcohol 10% aqueous solution (solid) 30 parts The above overcoat liquid was applied onto a multicolor recording thermal paper (c). Multi-color recording heat-sensitive overcoated paper (d) was obtained by coating and drying so that the coating after drying was 3 g / m ² .

A pressure-sensitive adhesive was applied to the back surface of the obtained multicolor recording heat-sensitive overcoated paper (d) and bonded to a release paper to prepare a multicolor recording heat-sensitive label sheet of the present invention.

Example 2 In the preparation of the multicolor heat-sensitive recording layer coating solution of Example 1, the dye precursor B of the solution A was changed to 3- (N-methylcyclohexylamino) -6-methyl-7-anilinofluorane. Instead, B
A multicolor recording heat sensitive label sheet was prepared in the same manner except that the phenolic substance of the liquid was replaced with bis (4-hydroxyphenyl) sulfone.

Example 3 In Example 1, the undercoat coating liquid was not applied,
A multicolor recording heat-sensitive label sheet was obtained in the same manner except that the base layer paper was directly coated with the heat-sensitive recording undercoat layer liquid.

Comparative Example 1 Multicolor was prepared in the same manner as in Example 1 except that the phenolic substance of solution B was replaced with bis (4-hydroxyphenyl) acetate-n-butyl in the preparation of the multicolor heat-sensitive recording layer coating solution. A recording heat sensitive label sheet was obtained.

Comparative Example 2 In the preparation of the coating liquid for the multicolor heat-sensitive recording layer of Example 1, the dye B of the liquid A was changed to 3- (N-methylcyclohexylamino) -6-methyl-7-anilinofluorane. Instead, B
A multicolor recording heat-sensitive label sheet was obtained in the same manner except that the phenolic substance in the liquid was changed to 4,4′-isopropylidenediphenol.

The multicolor recording heat-sensitive label sheets obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were evaluated by the following methods. The evaluation results are shown in Table 1.

(Coloring start temperature) A thermal gradient tester was applied at a specific test temperature at a pressure of 500 g / cm ² for 5 seconds,
The density of the applied portion is measured with a Macbeth densitometer RD-514 (filter W-106), and the temperature at which the value reaches 0.2 is defined as the color development start temperature. (Heat resistance) The density of the background part after being left for one day under the dry condition of 80 ° C is Macbeth densitometer RD-514 (filter W
-106). (Color density) Color was developed under the same conditions as the measurement of the color start temperature at a specific test temperature by using a thermal gradient tester, and 120 ° C. and 16
Macbeth densitometer RD-514 (120 ℃
Is filter W-106, 160 ° C is filter W-5
It was measured in 8).

[0037]

[Table 1]

In Table 1, each of the examples and comparative examples has 12
With applied energy of 0 ° C, it develops black color and appears at 160 ° C.
With the applied energy of 1, the above black color is erased to give a red color. In Examples 1 to 3, since the color formation starting temperature is within the range of the present invention, the heat resistance test shows that each of them is 0.0
The optical density of the background is low at 9, 0.06 and 0.08. On the other hand, in Comparative Example 1, the color development start temperature was 76 ° C., which was below the range, and the optical density of the background was as high as 0.28 in the heat resistance test.
There is background fog. Further, in Comparative Example 2, the color development start temperature is 115 ° C., which is out of the range, so that the optical density of the background is as low as 0.06, but the color development density at 120 ° C. is also low, which is not practical.

[0039]

INDUSTRIAL APPLICABILITY The multicolor recording heat-sensitive label sheet of the present invention has good record storability and heat resistance, and can provide a multicolor recorded image having a vivid contrast in the coloring hue.
It is highly practical.

Claims (2)

[Claims] 1. A release paper is attached to one side of a support through a pressure-sensitive adhesive layer, and an organic basic compound is attached to the other side of the support.
Dye precursor A capable of coloring with heat by the organic basic compound, phenolic substance or organic acid, dye precursor B capable of coloring with heat by the phenolic substance or organic acid, and an adhesive as appropriate as a main component A sheet for a multi-color recording heat-sensitive label comprising a single-layer or two or more multi-color heat-sensitive coloring layers and an overcoat layer containing an aqueous polymer as a main component, which are sequentially laminated. The temperature at which the optical density when applied to the surface of the multicolor recording color developing layer for 5 seconds at a pressure of / cm ² reaches 0.2 is the color development start temperature, and the color development start temperature on the surface of the multicolor thermosensitive color development layer is 85 to 110. A sheet for a multicolor recording heat-sensitive label, which has a temperature of ℃. 2. A multicolor recording thermosensitive label according to claim 1, wherein an undercoat layer containing an inorganic or organic pigment and an adhesive as a main component is provided between the support and the multicolor thermosensitive coloring layer. Sheet.