EP1363786A1

EP1363786A1 - Thermosensitive recording material and use thereof

Info

Publication number: EP1363786A1
Application number: EP02722100A
Authority: EP
Inventors: Bernd Gerecht; Matthias Marx
Original assignee: Mitsubishi HiTech Paper Flensburg GmbH
Current assignee: Mitsubishi HiTech Paper Flensburg GmbH
Priority date: 2001-02-23
Filing date: 2002-02-20
Publication date: 2003-11-26
Anticipated expiration: 2022-02-20
Also published as: DE10108982A1; US20040132616A1; JP2004520974A; WO2002068207A1; ATE285335T1; DE50201836D1; US7008902B2; ES2235028T3; EP1363786B1

Abstract

The invention relates to a thermosensitive recording material, comprising a substrate ( 1 ), a thermosensitive recording layer ( 4 ) containing a colour former and colour acceptors, a protective layer ( 5 ) configured on the recording layer, whereby a coat ( 6 ) that covers the surface and is locally delimited is printed onto the protective layer. The invention also relates to the use of the inventive recording material as a ticket.

Description

Heat sensitive recording material and its use

The invention relates to a heat-sensitive recording material with a substrate, a heat-sensitive recording layer containing color formers and color acceptors and a protective layer formed on the recording layer, and to its use as a ticket.

A heat-sensitive recording sheet of the type mentioned is known from EP-ß-0909242. With a pigment content of 20 to 40% by weight, the protective layer of the recording sheet, which can be used as a label, receipt or ticket and can be easily printed using the wet offset process, has in particular bentonite as a pigment, while the binder content consists largely of water-insoluble binder in the form of a polymer dispersion and consists to a lesser extent of an aqueous solution of a polymer. In this document, natural calcium carbonate, precipitated calcium carbonate, silicon dioxide, atomic oxide and titanium oxide are disclosed as further pigments in the protective layer. While polyvinyl alcohol is preferably mentioned as the water-soluble binder, the water-insoluble binders are preferably self-crosslinking copolymers of acrylonitrile methacrylamide and acrylic ester.

A protective layer is known from EP-A-0 344705, in which 0.5 to 3 parts by weight of pigment are present per part by weight of binder. Suitable binders for the protective layer include polyvinyl alcohol, carboxymethyl methulose, starch and starch derivatives, and copolymer emulsions of styrene-butadiene, vinyl acetate-ethylene, vinyl acetate-vinyl chloride-ethylene and methacrylic butadiene. Precipitated calcium carbonate, ground calcium carbonate, talc, kaolin, silicon dioxide anhydride, magnesium carbonate, zinc oxide, aluminum oxide and aluminum hydroxide in addition to organic pigments are mentioned as suitable pigments. Protective layers containing pigment, which only contain water-soluble binder, are described by way of example. EP-B-0373903 relates to a heat-sensitive recording paper with an internal adhesive strength of 2.5 kgcm or more, which has a protective layer with a smoothness of at least 500 Bekk-seconds, preferably from 700 to 1500 Bekk-seconds, on a fine particle of a Styrene-acrylate polymer and an intermediate layer containing a binder is applied. Suitable binders for the protective layer are both water-soluble and water-insoluble high polymers with sufficient film-forming capacity. Any pigment addition to the protective layer is also disclosed, but the document does not provide any indication of the type of suitable pigments.

The well-known heat-sensitive recording materials have undoubtedly proven themselves in numerous areas of application, for example as office paper as well as tickets, however, new, often contradicting requirement profiles always require completely new, innovative products that break with the known approaches.

With the already known use of heat-sensitive recording materials as a ticket and in particular as a ticket, the need for those materials which on the one hand have a high environmental resistance increased. This means the outstanding resistance of the heat-sensitive recording material to water, plasticizers, oils and greases. The demand for resistance to water arises from the fact that typefaces generated on a ticket by means of heat supply must remain decipherable and controllable for the duration of a usage interval even if the ticket cannot be kept protected on rainy days. In the same way, the ticket must not lose its typeface if it comes into contact with fats and oils. Since tickets are often stored in insert sleeves to protect them from mechanical destruction, it is also necessary that the heat-sensitive recording materials used in this way have a high resistance to plasticizers, as are usually contained in insert sleeves. On the other hand, there is a demand for an increased wipe resistance compared to the prior art and thus a more reliable validation, which is to be understood in the sense of the object on which this invention is based, that stamped validation marks cannot be smeared dry or wet after about 10 seconds. Up to now, only those heat-sensitive recording materials are known in which the devaluation stamp ink applied to the protective layer cannot be completely wiped off dry or wet from the protective layer, but the wiping resistance is still not fully satisfactory in that wiping results in a noticeably more blurred printed image compared to same print image before wiping.

Since tickets and, in particular, tickets usually have imprints applied by means of flexographic or, in particular, wet offset printing processes, the printability on the entire surface of the protective layer at the points where a validator imprint is not provided is a further requirement.

Not to be underestimated is the necessity that suitable recording materials have to be inexpensively manufactured for use as tickets. So far, none of the known heat-sensitive recording materials has been able to fully meet this range of requirements.

In summary, it is an object of the present invention to provide a heat-sensitive recording material which, as a ticket and here in particular as a ticket, guarantees excellent locally limited validity through increased smudge resistance of prints with the validation stamp color. The new recording material must be characterized by a high level of environmental resistance. An essential part of the new recording material must be its cost-effective production method. In addition, the invention sees its task in developing a recording material which, in addition to the range of requirements listed above, also has excellent printability the entire surface of the protective layer at the points where a validation print is not provided.

As a result of extensive preliminary work, the inventors recognized that such a large number of contradicting requirements can be met by a heat-sensitive recording material having a substrate, a heat-sensitive recording layer containing color formers and color acceptors and a protective layer formed on the recording layer, with a full-surface, locally limited coating is printed.

A particularly suitable embodiment of the present invention provides for the single-layer formation of the protective layer for economic reasons.

The thermal head which triggers the color-forming reaction of the color formers with the color acceptors in the heat-sensitive recording layer causes the wax-like constituents in the recording layer to melt. To prevent these wax-like constituents from adhering to the thermal head as a melt, it is preferred that an intermediate layer containing a pigment or a pigment mixture be formed between the heat-sensitive recording layer and the substrate, the pigments of this intermediate layer causing the melt to be absorbed. It is particularly advantageous if the pigment of the intermediate layer of at least 80 ^cm3 / 100 g, and more preferably of 100 cm, having an oil absorption ^3/100 g, determined according to the Japanese standard JIS K 5,101th Calcined kaolin has proven particularly useful due to its large absorption reservoir in the cavities. Numerous tests have shown that it is advantageous to choose pigments with a higher oil absorption in the intermediate layer than in the "spot" coating, that is the full-area and locally limited coating printed on the protective layer. Because the air in the cavities the pigments of the intermediate layer represent a good heat insulator, an intermediate layer formed in this way acts as a heat reflection layer, as a result of which the heat sensitivity of the recording material and thus the Print speed in the thermal printer can be increased. Furthermore, such an intermediate layer can make a positive contribution to the leveling of the substrate surface, thus reducing the amount of coating color which is necessarily to be applied for the heat-sensitive recording layer. The formation of an intermediate layer with a mass per unit area in a range from 5 to 20 g / m ² and even better between 7 and 10 g / m ^{2 has a} particularly advantageous effect.

A coating color, as proposed in P-B-0 909 242, is well suited for forming the protective layer for the new recording material. Such a protective layer combines high environmental resistance with excellent printability in the wet offset process. The protective layer is also relatively inexpensive to manufacture and apply in one layer.

In order to support the devaluability of the new recording material at locally limited locations and to make it possible that only the thinnest possible application of the “spot” coating has to be applied, which is conducive to an increased resolution of the heat-induced protective images, it has proven to be turned out to be particularly advantageous if

The pigment of the protective layer consists of one or more inorganic pigments and at least 80% by weight is formed from a highly purified alkaline bentonite,

The binder of the protective layer consists of one or more water-insoluble, self-crosslinking acrylic polymers,

The binder-Z pigment ratio in the protective slide is in a range between 7: 1 and 9: 1,

• The crosslinking agent / binder ratio in the protective layer is greater than 1: 5 and preferably between 1: 5 and 1: 7 and

• The protective layer has a smoothness of at least 900 Bekk seconds. Natural or precipitated calcium carbonate, kaolin or titanium oxide are possible as further inorganic pigments for the protective layer. Cyclic urea, methylol urea, polyamide epichlorohydrin resin and ammonium zirconium carbonate are particularly suitable as crosslinking agents for the protective layer.

An embodiment explained above ensures a heat-sensitive recording material which has good printhead behavior over the entire area and whose protective layer at the same time has good environmental resistance and excellent printability in the flexographic and wet offset processes.

It is preferred to apply the protective layer with a mass per unit area in a range from 1.5 to 6 g / m ² and in particular between 1.8 and 4 g / m ² .

The recording material according to the invention preferably has a backside coating which is applied to the substrate side which is opposite the side provided with the heat-sensitive recording layer. Such a back coating is proposed, for example, in DE-A-9748258 and then serves to improve the printability of the recording sheet on the back in the offset and flexographic printing processes and to improve the blocking effect of the back against plasticizers, oils and greases. For the area-related mass of the back coating, application quantities in a range from 1 to 3 g / m ² and especially between 1.5 and 2.5 g / m ^{2 have} proven to be advantageous.

The full-surface, localized so-called "spot" coating is preferably a rectangle on the edge fitted in the form of as a ticket, that is printed and printed cut heat-sensitive recording material. The used therefor ink preferably contains pigments having an oil absorption of at least 80 ^cm3 / 100 g determined according to the Japanese standard JIS K 5101. As already explained above, it is advantageous to choose a greater oil absorption of the pigments in the intermediate layer than the oil absorption of the pigments in the "spot" coating. Another preferred embodiment provides that the printing ink applied as a “spot” coating is 60 to 90% by weight. of pigment having an oil absorption of at least 80 ^cm3 / 100 consists g. Further constituents of the water-based printing inks for the "spot" coating are alcohols such as isopropanol or ethanol as solvents and, for example, maleate, polyester and acrylate resins as binders, the carboxyl groups of which are saponified with aqueous ammonia or with amines and in water-soluble salts The printing inks produced in this way can be easily stamped and the applied stamping ink is smudge-proof after about 10 seconds.

Even if not limited to paper as the substrate, paper is the substrate which has also become established on the market with a view to its good environmental compatibility due to its good recyclability and which is preferred in the sense of the invention.

The heat-sensitive recording material according to the invention is mainly designed for use as a ticket and here in particular as a ticket. After the purchase and before the start of the journey, the passenger pushes the ticket into a dedicated validation machine so that the validation print is applied to the full-surface, locally limited so-called "spot" coating. After approx. 10 seconds, the validation print is dry-wiped, so that there is no risk of the passenger getting dirty on the inadequately fixed printing ink, and at the same time the printing for control purposes can always be easily deciphered.

Extensive investigations showed that an ink application with a mass per unit area in a range from 1 to 5 g / m ² and especially between 2 and 3.5 g / m ² delivers particularly good results.

Since the intended use of the heat-sensitive recording material according to the invention as a ticket sometimes also requires authenticity features, its integration is also provided in a preferred embodiment. DE-A-199 36030 provides an overview of authenticity features that can be used individually or in combination, but is not limited to the suggestions made there. The information given in the description and in the claims on the mass per unit area and on% by weight (% by weight) relates in each case to the “atπ weight”, ie absolutely dry parts by weight.

Among the high environmental resistance of the recording material according to the invention is its outstanding resistance to the media

• Water,

• plasticizers as well

• Understand oils and fats. The procedure used to prove the resistance to environmental protection provides that a measurement cycle consisting of 3 independent emission values is carried out for each proof of resistance.

A single value determination provides that a DIN A4 sample is first cut. To determine the individual value, the ratio of two measurements of the dynamic pressure density determined using the Macbeth RD 914 from Karl Schröder KG (Korrillonstrasse 32, D-69469 Weinheim) is recorded. For this purpose, the sample is provided with a typeface using a TP 3000-300 thermal printer from Charles Richiger AG _V Maschinenbau (Bemstrasse 81 _τ CH-3613 Steffisburg). After a first measurement of the dynamic pressure density, the sample is exposed to the corresponding medium for a certain time (exposure time see table). The excess medium is then suctioned off or dabbed off. Medium already taken up by the sample is left to act for a certain time (rest period before measurement see table). Finally, the dynamic print density is measured a second time.

The arithmetic mean is drawn from the 3 individual values determined in this way. The media resistance examined can be described as very good if the arithmetic mean of the quotients determined from two measurement values in each case is greater than the “limit value of image stability” according to Table 1.

The following examples will further illustrate the invention.

Example 1:

A paper web made of bleached and ground hardwood and softwood cellulose with a mass per unit area of 67 g / m ² is added to the substrate on a Fourdrinier paper machine with the addition of conventional admixtures in conventional quantities. A calcined kaolin as a pigment, styrene-butadiene latex as a binder and starch as a cobinder are applied to the front in addition to an additional intermediate layer of 8 g / m ² .

A heat-sensitive recording layer containing color formers and color acceptors and having a mass per unit area of 5.4 g / m ^{2 is} applied to the intermediate layer.

A protective layer of 2 g / m ^{2 is} applied to the dried recording layer. The pigment used is a highly purified, alkaline-processed bentonite with a platelet structure, the self-adhesion of which enables it to be fixed with little need for binding agents, and the specific surface area of which, in the undispersed state, is stated to be 85 m ² / g with an area-to-edge ratio which corresponds to Bentonite in powder form is in a range of between 20 and 50. A binder / pigment ratio of 6: 1 and a crosslinking agent / binder ratio of 1: 5 are set. Polyamide epichlorohydrin resin is used as the crosslinking agent, and the aqueous dispersion of a self-crosslinking copolymer of acrylonitrile, methacrylate and acrylic ester is used as the binder. The coating slip for the production of the protective layer contains, as further components, a defoamer, stearic acid as a lubricant and various dispersants, on the one hand for the pigment and on the other hand for the lubricant. The applied coating slip is dried and the record sheet produced so far is smoothed using a calender, with a smoothness of 2200 Bekk seconds being achieved.

8 mm wide strips are then printed onto the protective layer as "spot" coatings with a mass per unit area of 2.2 g / m ^{2 in} such a way that the "spot" coating strips are arranged on two opposite outer lines of the ticket when the ticket is cut , The printing ink JDG 9033 (matt lacquer) "offered by GSB-Wahl GmbH Buchenteich 1, D-73773 Aichwald is used.

The side of the heat-sensitive recording material according to the invention which has been provided with a protective layer is checked for its environmental resistance at the points not printed with a "spot" coating and is determined to be very good. After 10 seconds, the wipe proof is checked for smudge resistance with a damp finger; the stamp cannot be blurred.

Example 2:

On the protective layer of a heat-sensitive recording material produced in accordance with Example 1 of EP-B-0909242, 10 mm × 50 mm “spot” coating rectangles each with a mass per unit area of 3.2 g / m ^{2 are} printed in such a way that the “spot” Lighting rectangles are arranged with the long side parallel to an outline of the ticket in the finished ticket. The printing ink "DG 9033 (matt lacquer)" offered by GSB-Wahl GmbH, Buchenteich 1, 0-7377.3 Aichwald, is used. The side of the heat-sensitive recording material according to the invention thus produced, which is provided with a protective layer, is not coated with a "spot" coating printed areas checked for their environmental resistance and determined as very good. The validation print is checked after 10 seconds with a damp finger for its smudge resistance; the stamp cannot be blurred. Example 3:

On the protective layer of a heat-sensitive recording material produced in accordance with Example 2 of EP-B-0 909242, 10 mm × 50 mm “spot” coating rectangles each with a surface-related mass of 2.8 gm ^{2 are} printed in such a way that the “spot” coating rectangles at ready-cut ticket with their Jangen side paraäei to an outer line of the ticket are arranged. The printing ink DG 9032 "offered by GSB-Wahl GmbH Buchenteich 1, D-73773 Aichwald, is used. The side of the heat-sensitive material according to the invention thus produced, which is provided with a protective layer, is resistant to the environment at the points not printed with a" spot "coating checked and determined as very good. The validation print is checked after 10 seconds with a damp finger for its smudge resistance; the stamp cannot be blurred.

Example 4:

On the protective layer of a heat-sensitive recording material produced in accordance with Example 3 of EP-B-0909242, 10 mm × 50 mm “spot” coating rectangles each with a mass per unit area of 3.3 g / m ^{2 are} printed in such a way that the “spot” coating rectangles in the finished cut ticket with its long side arranged parallel to an outside line of the ticket. The printing ink HK 9035 offered by Akzo Nobel, Kreuzauer Strasse 46, D-52301 Duren is used.The side with a protective layer of the heat-sensitive recording material according to the invention thus produced is applied to the areas not printed with a "spot" coating were checked for their resistance to environmental damage and determined to be very good. After 10 seconds, the validation print is checked for smudge resistance with a dampened finger; the validation print cannot be blurred. The invention is explained further below with reference to the two FIGS. 1 and 2.

Figure 1 shows the schematic structure of the heat-sensitive recording material according to the invention in cross section. A back coating (2) is applied to the underside of the substrate (1). An intermediate layer (3), a heat-sensitive recording layer (4) and a protective layer (5) are applied to the front of the substrate (1) in the order shown here. Finally, a full-area, locally limited print job (6) is arranged on the protective layer.

Figure 2 shows an example of the heat-sensitive recording material according to the invention cut to the ticket in the plan. On the protective layer (5) which can only be recognized in the plan, the full-area, locally limited print job (6) is applied in the form of a rectangle, the long side of which is parallel to one Extra line of the ticket is arranged.

Claims

claims

1. Heat-sensitive recording material with a substrate, a color-sensitive and color acceptor-containing heat-sensitive recording layer and a protective layer formed on the recording layer, characterized in that a full-surface, locally limited coating is applied to the protective layer as a "spot" coating

2. Heat-sensitive recording material according to claim 1, characterized in that the applied printing ink contains binders based on polyester or acrylic resin

3. Heat-sensitive recording material according to one of claims 1 or 2, characterized in that the protective layer is formed in one layer.

4. Heat-sensitive recording material according to one of claims 1 to 3, characterized in that the protective layer has a smoothness of at least 900 Bekk seconds.

5. Heat-sensitive Aufieiehnungsmaterial according to any one of claims 1 to 4, characterized in that an intermediate layer containing a pigment or a pigment mixture is formed between the substrate and the heat-sensitive recording layer

6. A heat-sensitive Aufeeiehnungsmaterial of claims 1 to 5, characterized in that the pigments have ³ according to one in the intermediate layer has an oil absorption of at least 80 cm / 100 g.

According to one of claims 1 to 6, characterized in that the applied printing ink contains 7. A heat-sensitive Aufeeiehnungsmaterial pigments having an oil absorption of mimdestens 80 ^cm3 / 100 g.

8. Heat-sensitive recording material according to one of claims 1 to 7, characterized in that the applied printing ink to 60-90 wt.

% consists of pigments with an oil absorption of at least 80 cm 3/100 g.

Heat-sensitive Aufieiehnungsmaterial according to any one of claims 1 to 8, characterized in that the pigments in the intermediate layer have a greater oil absorption than the pigments in the "spot" coating.

10. Heat-sensitive Aufieiehnungsmaterial according to any one of claims 1 to 9, characterized in that on the side of the substrate, which is opposite the side with the heat-sensitive Aufeichnungsschicht, a back coating is applied.

11. Heat-sensitive Aufieiehnungsmaterial according to any one of claims 1 to 10, characterized in that the substrate is paper.

12. Use of a heat-sensitive material according to one of claims 1 to 11 as a ticket.

13. Use of a ticket according to claim 12 for applying at least one stamp on the full-area, locally limited coating.