JPS62290577A - Heat-sensitive recording material for labeling - Google Patents

Abstract

PURPOSE:To improve storing performance, water-proof performance, oil-proof performance and anti-plasticizer performance of an image being colored through heating, by containing polyester resin which contains sulfonic acid base as main component into one of a heat-sensitive coloring layer or a barrier layer. CONSTITUTION:A leuco dye system heat-sensitive coloring layer, a barrier layer and a protection layer are provided sequentially onto the surface of a supporting material. A lamination structure having a separator is provided through an adhesive layer onto the rear face of the supporting material, and polyester resin containing sulfonic acid base simultaneously satisfying the condition that a monomer containing sulfonic acid base occupies 6-15 mol.% of the entire dicarboxylic acid while ethylene glycol and ether glycol occupy respectively 85 mol.% or more and 15 mol.% or less of the entire glycol component is contained as main component in one of the heat-sensitive coloring layer or the barrier layer. Consequently, the heat-sensitive coloring layer exhibits excellent water-proof performance, temperature/humidity dependance, anti- plasticizer performance, etc. under severe environment.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a heat-sensitive recording material for labels,
More specifically, the present invention relates to a heat-sensitive recording material for labels which has excellent storage stability, water resistance, and chemical resistance, and whose heat-sensitive colored images have practically excellent durability.

<Prior Art> In recent years, there has been an increasing demand for the use of labels using heat-sensitive recording materials for displaying product prices, product names, store names, etc., and for managing parts in production processes.

In this case, the heat-sensitive recording material is one in which a heat-sensitive coloring layer made of a binder containing a leuco dye such as a lactone compound and an organic acid or phenol compound such as bisphenol A dispersed in a binder is coated on a support, and is heated in a pixel pattern. As a result, the color-forming lactone compound in the heated portion and the organic acid or phenol compound chemically react to develop color. In this case, the basic properties required of a heat-sensitive recording material are good color development, an appearance as white as possible (similar to natural paper), and long-term storage stability. ) High sensitivity, (b) No sticking property, (c) No lees adhering to the thermal head (
Good compatibility with thermal heads is required.

In this way, heat-sensitive recording materials are desired to have the above-mentioned properties depending on their use, but this type of coloring dye is unstable to light, water, temperature, plasticizers, oil, etc. Moreover, changes over time during storage are always a problem. Therefore, when desired printing is performed on such a heat-sensitive recording material, even if the recorded color is extremely clear,
When used for labels such as the one of the present invention, extremely harsh usage characteristics are required in terms of customer handling, usage environment, usage frequency, etc., unlike ordinary facsimile applications. For example, if a plastic film containing a large amount of plasticizer (for example, a soft film made of polyvinyl chloride) is placed in close contact with this coloring area, or if it is stored with oil or fat attached, the color may fade. Significant discoloration often occurs when the color is stored away or when the colored part comes into contact with water for a long period of time.

Therefore, there has been a strong demand for the development of measures to prevent the above-mentioned fading phenomenon, which occurs when a heat-sensitive recording material comes into contact with oil or plasticizer.

Therefore, in order to improve these drawbacks, it is proposed to provide a protective layer on the heat-sensitive coloring layer, for example, as disclosed in JP-A-48-51644.
It was proposed in the Publication No. 59-9909, etc.
No. 1, it was proposed that a barrier layer consisting of a water-soluble polymeric substance and a water-resistant agent to make it water-resistant be provided on the heat-sensitive coloring layer.

However, it has not been possible to obtain a thermosensitive recording material that can withstand practical use as a label.

<Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned circumstances, and aims to improve the storage stability, water resistance, oil resistance, and plasticizer resistance of images colored by heating, and to improve the storage stability, water resistance, oil resistance, and plasticizer resistance of images colored by heating. The purpose of the present invention is to provide a heat-sensitive recording material that can withstand practical use.

Means for Solving Problems> The present invention comprises sequentially providing a leuco dye-based heat-sensitive coloring layer, a barrier layer and a protective layer on the surface of a support, and providing a separator on the back surface of the support with an adhesive layer interposed therebetween. It has a laminated structure, and at least one of the thermosensitive coloring layer and the barrier layer contains (a) 6 to 15 mol % of a sulfonic acid group-containing monomer in all dicarboxylic acids (b) ethylene glycol in all glycol components This heat-sensitive recording material for labels is characterized in that it contains as a main component a sulfonic acid group-containing polyester resin which satisfies the following conditions: 85 mol % or more of ether glycol and 15 mol % or less of ether glycol.

The specific sulfonic acid group-containing polyester resin as described above is synthesized, for example, as follows.

Specifically, a dicarboxylic acid component, ethylene glycol, ether glycol component, and a dicarboxylic acid containing a sulfonic acid group are subjected to an esterification reaction at a temperature of 170 to 280°C in the presence of an esterification catalyst such as dibutyltin oxide or antimony trioxide. 0.5 in the presence of condensation catalyst
It can be obtained by polycondensation reaction at 240 to 280°C under a vacuum of ~1,0 i+nHg. Said (
The content of each component specified in a) and (b) roughly corresponds to the amount of each raw material, so if you decide the amount of material according to the target content of components (a) and (b), good.

If the content of component (a) is less than 6 mol%, the water solubility decreases, making it difficult to prepare a coating solution.On the other hand, if the content of component (a) is 15 mol% or more, it causes a decrease in the water resistance of the recording paper, making it difficult to put into practical use. lacking in sex.

Further, the amount of ethylene glycol in component (b) must be 85 mol % or more, and if it is less than this, the solvent resistance will decrease. Furthermore, when 15 mol% or more of ether glycol is introduced, Betokki,
There are drawbacks such as blocking, etc., and inhibiting the stability of the color developer.

The dicarboxylic acid used above may be acids such as terephthalic acid, isophthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, and sebacic acid, or their anhydrides, esters, and chlorides.

In addition, to introduce the ether glycol component, the general formula H-(O
Polyethylene glycol represented by CH2CH2)-;OH (n; an integer of 2 or more) is used, and specific examples include diethylene glycol, triethylene glycol, and tetraethylene glycol.

Furthermore, examples of the sulfonic acid group-containing dicarboxylic acid include 5-sodium sulfoisophthalic acid, 5-sodium sulfophthalic acid, 5-potassium sulfoisophthalic acid, 5-potassium sulfophthalic acid, and alkyl esters thereof. Of course, the polyester resin of the present invention may contain saturated or unsaturated mono- or polycarboxylic acids other than those mentioned above, 1,3-butylene glycol, 1,4-butylene gellicol, (1), 6-hexanediol, if necessary. , polyhydric alcohol such as neopentyl glycol can also be used in combination.

When the above-mentioned sulfone base-containing polyester resin is used in the leuco dye-based thermosensitive coloring layer, it is used as a binder for the coloring agent, but in that case, it is also possible to use it in combination with a water-based resin as shown below. If the polyester resin is not used, the present invention can be carried out using the following aqueous resin alone.

For example, polyvinyl alcohol, starches, hydroxyethylcellulose, gum arabic, polyvinylpyrrolidone, alkali salts of acrylic or methacrylic acid ester copolymers, alkali salts of styrene/maleic anhydride copolymers, isobutylene/maleic anhydride copolymers, etc. This includes alkali salts of polymers, water-soluble polymer compounds such as acrylamide copolymers, polymer latexes such as styrene/butadiene copolymers, polyvinyl acetate, and acrylic acid ester copolymers, and water-based resins such as emulsions. .

Leuco dyes dispersed in such binders are usually colorless or light-colored triphenylmethane-based, fluoran-based,
Leuco bodies such as phenothiozine type, auramine type, spiropyran type, etc. are applied, and α-naphthol, which causes a thermochromic reaction with the leuco body and causes the leuco body to develop color;
Acidic substances such as β-naphthol, bisphenol A1 benzoic acid, and salicylic acid are blended into the leuco dye-based heat-sensitive coloring layer in the present invention. A heat-sensitive coloring coating liquid consisting of a binder resin, a leuco dye, and an acidic substance as described above is applied to the surface of a support and dried to provide a leuco dye-based heat-sensitive coloring layer.

In this case, the supports include sheets of vinyl chloride resin, polyester resin, polypropylene, etc., synthetic resin sheets with high water resistance, chemical resistance, and durability such as synthetic paper or laminated paper, paper, and metal foil. A substrate is applied. Particularly preferred are vinyl chloride resins and polyester resin sheets that exhibit strong binding strength with the sulfonic acid group-containing polyester resin having the specific composition referred to in the present invention. Furthermore, it is also possible to matt the surface of the support made of these resin sheets or provide an anchor coat layer to increase the binding force between the support and the heat-sensitive layer.

The barrier layer referred to in the present invention is used to separate a protective layer made of a solvent-based paint from a heat-sensitive coloring layer, and a commonly known water-soluble resin is used as the material. It is preferable to use the above-mentioned sulfonic acid group-containing polyester resin as the main component in terms of properties, solvent resistance, and affinity with the leuco dye-based heat-sensitive coloring layer. In addition, additives such as a resin curing agent and a coating property modifier may be added to the barrier layer in the present invention, if necessary.

The barrier may contain, for example, casein, gelatin, styrene-maleic anhydride resin, polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, starch, etc., in order to modify the coating properties, coating properties, and coating film of the barrier layer. Modified starch, isobutylene-maleic anhydride resin, diisobutylene-maleic anhydride resin, polyacrylamide, modified polyacrylamide, methyl vinyl ether, maleic acid copolymer, carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and water-soluble As a polyester emulsion, resins such as vinyl acetate, polystyrene, acrylic ester, vinyl chloride-vinyl acetate copolymer, etc. can be mixed with the above-mentioned sulfonic acid group-containing polyester resin. Furthermore, when the sulfonic acid group-containing polyester resin is not used in the barrier layer, the various water-soluble resins described above can be used alone.

In addition, the barrier layer may contain a curing agent, a surfactant, or an antioxidant to improve the light resistance of the heat-sensitive recording material, if necessary.
It may also contain an ultraviolet absorber or the like.

Furthermore, the protective layer referred to in the present invention is provided on the heat-sensitive coloring layer to improve water resistance, chemical resistance, abrasion resistance, etc., and to match with a recording thermal head, and includes, for example, polyurethane resin,
Although various solvent-type polymers such as acrylic resins, epoxy resins, and fluorine-based resins are applicable, polyurethane resins are particularly preferably used in the present invention in terms of water resistance and abrasion resistance.

Next, the adhesive used for the adhesive layer is an emulsion type adhesive such as acrylic ester resin, ethylene/vinyl acetate copolymer resin, natural rubber type, synthetic rubber type, etc.
Solution-type products such as polyacrylic acid ester and polyvinyl alcohol are used, and when forming the adhesive layer and attaching the separator, the adhesive is applied to the back of the support and attached to the separator by dry lamination, or the separator is attached to the adhesive layer. This is done by applying an adhesive to the back of the support and bonding it to the back side of the support.

As the separator, there may be used a support such as paper coated and impregnated with a release agent such as a silicone resin or a fluorine-based resin, or a plastic tape made of a silicone resin or a fluorine-based resin having an excellent release effect.

In addition, in the present invention, if a moisture-sensitive adhesive is used in the adhesive layer, it is possible to carry out the process without using a separator.

Moisture-sensitive adhesives used as adhesives include polyvinyl alcohol, dextrin starch, and the like, which are normally dry and become sticky upon absorbing moisture.

The present invention will be explained in detail below using Examples and Comparative Examples. Note that all parts in the recipe table indicate parts by weight.

<Examples> Example 1 A leuco dye-based coloring layer was formed on the surface of a support made of a polyester film kneaded with titanium oxide having a thickness of 188 μm.
A barrier layer and a protective layer were sequentially coated and laminated according to the following formulation.

[Leuco dye-based thermosensitive coloring layer]

First, a sulfonic acid group-containing polyester resin having a specific composition to be used as a binder was synthesized as follows.

Terephthalic acid 76, 4 g % isophthalic acid 7 in a 500 gloss flask with stirrer, thermometer, nitrogen blowing device, and packed tower.
6.4g, 5-sodium sulfoisophthalic acid dimethyl ester 23.7g, ethylene glycol 93.1g,
After charging 0.2 g of zinc acetate and 0.4 g of antimony trioxide and carrying out an esterification reaction at 190 to 220°C for 4 hours, a condensation reaction was carried out at 230 to 250°C under lmmHg.
8 mol% of sulfonic acid group-containing monomers in all dicarboxylic acids, 10 mol% of ethylene glycol in all glycol components
A sulfonic acid group-containing polyester resin containing 0 mol% of ether glycol and 0 mol% of ether glycol was synthesized. 90% of this resin
A 20% sulfonic acid group-containing polyester aqueous solution was prepared with hot water at .degree.

Next, in order to obtain a heat-sensitive paint, each mixture consisting of the following formulations was ground and dispersed in a ball mill for one day to prepare solutions A to C.

Solution A Solution B Solution Solution 10 parts of Solution A, 3 parts of Solution B, 49 parts of Solution C, 15 parts of an aqueous sulfonic acid group-containing polyester solution, and 46 parts of water were mixed to obtain a heat-sensitive recording paint.

The coating material was applied to the surface of the support in an amount of 6 g/- after drying, and dried to provide a leuco dye-based heat-sensitive coloring layer.

[Barrier layer]

A barrier layer coating solution having the following formulation was prepared using the polyester resin used in the heat-sensitive color forming layer, and was coated on the heat-sensitive color forming layer and dried to form a barrier layer with a coating weight of 3 g/-.

[Protective layer]

A protective layer coating solution having the following formulation was prepared, and an adhesive made of ethylene-vinyl acetate copolymer resin was applied to a barrier side, a separator made of silicone release paper with a basis weight of 85 g/d. A heat-sensitive recording material for a label according to the present invention was prepared by laminating the surface thereof to the back surface of the support provided with the heat-sensitive coloring layer and the like.

For the heat-sensitive coloring layer of the heat-sensitive recording material for labels of the present invention,
Using a line-tod type thin film thermal head, 0.45W (1
When an image was recorded with an energy of
A clear colored image of 0 was obtained. Next, as a water resistance test, the sample immediately after color development was immersed in water at 20° C. for 3 days, and the decrease in concentration was measured using a Macbeth densitometer, and the result was 1.18, confirming sufficient water resistance. In addition, in order to check the storage stability in temperature and humidity, we looked at the color development characteristics after leaving it in a constant temperature bath at a temperature of 40℃ and a relative humidity of 90% for one week.
．． 17 was obtained, and excellent storage stability was confirmed. Furthermore, the colored recording surface was overlapped with a plasticizer-containing plastic eraser and pressed together with a pressure of 2 kg/c+J, and after being left for 24 hours, the eraser was removed and the recording surface was examined. No change was observed, indicating excellent plasticization resistance. The drug properties were confirmed.

Example 2 A heat-sensitive recording material for labels of the present invention was obtained in the same manner as in Example 1 except that the barrier layer in Example 1 was changed to the following formulation.

The properties of the obtained heat-sensitive recording material for labels were evaluated in the same manner as in Example 1, and it was confirmed that the leuco dye-based heat-sensitive coloring layer had excellent coloring properties, water resistance, storage stability, and plasticizer resistance.

Example 3 The properties of the heat-sensitive recording material for labels obtained were evaluated in the same manner as in Example 1 in the same manner as in Example 1 except that the protective layer in Example 1 was replaced with an ultraviolet curing protective layer having the following formulation. , excellent coloring properties, water resistance, storage stability, and plasticizer resistance were confirmed for the leuco dye-based thermosensitive coloring layer.

Comparative Example A comparative heat-sensitive recording material for labels was prepared in the same manner as in Example 1, except that a sulfonic acid group-containing polyester resin produced by the synthesis method shown below was used in place of the sulfonic acid group-containing polyester resin used in Example 1. I got the material.

That is, a stirrer, a thermometer, a nitrogen blowing device, and a packed tower 5
In a 00cc flask, 116.3 g of terephthalic acid, 21.9 g of adipic acid, 44.4 g of 5-sodium sulfoisophthalic acid dimethyl ester, and 62.0 g of ethylene glycol were added.
1gs diethylene glycol 53.1g, zinc acetate 0.
2g, antimony trioxide 0.4g 190-22
After esterification reaction at 0℃ for 4 hours, 230-250
A condensation reaction was carried out at ℃ and 1 nm + Hg to obtain a sulfonic acid group-containing polyester resin containing 8 mol% of sulfonic acid group monomers in all carboxylic acids, 67 mol% of ethylene glycol and 33 mol% of ether glycol in all glycol components. Synthesized.

The obtained heat-sensitive recording material for labels was coated with a line-tod type thin film thermal head in the same manner as in Example 1, and was heated to a temperature of 0.45.
An image was recorded with an energy of W (1 mJ/dat), and the solid black part was measured with a Macbeth densitometer.
A clear colored image of 1.18 was obtained. Next, as a water resistance test, the sample immediately after color development was immersed in water at 20°C for 3 days, and the concentration drop was 0.41 using a Macbeth densitometer.
It was confirmed that the water resistance was insufficient. In addition, in order to check the storage stability in temperature and humidity, we looked at the color development characteristics after leaving it in a constant temperature bath at a temperature of 40°C and a relative humidity of 90% for one week, and the Macbeth densitometer showed a value of 0.37, indicating that the storage stability was also good. This had a significant problem in terms of practical characteristics.

<Effects of the Invention> The heat-sensitive recording material for labels of the present invention has a sulfonic acid group-containing polyester resin having a specific composition blended into at least one of the leuco dye-based heat-sensitive coloring layer and the barrier layer in its laminated structure. Therefore, even when the heat-sensitive coloring layer is used under harsh customer usage conditions, it has been confirmed that it has extremely excellent durability in terms of water resistance, temperature/humidity dependence, plasticizer resistance, etc.

In addition, the sulfonic acid group-containing polyester resin having the specific composition referred to in the present invention has good adhesion to various synthetic resin supports, so when it is blended as a binder for a heat-sensitive coloring layer, the coating layer does not change even when bent. Excellent practical properties can be obtained without peeling.

Claims (1)

[Scope of Claims] It has a laminated structure in which a leuco dye-based thermosensitive coloring layer, a barrier layer, and a protective layer are sequentially provided on the surface of a support, and a separator is provided on the back surface of the support with an adhesive layer interposed therebetween, and At least one of the heat-sensitive coloring layer and the barrier layer contains (a) 6 to 15 mol% of the sulfonic acid group-containing monomer in the total dicarboxylic acids (b) 85 mol% of ethylene glycol in the total glycol components
1. A heat-sensitive recording material for labels, comprising as a main component a polyester resin containing a sulfonic acid group, which satisfies the following conditions: 15 mol% or more of ether glycol.