DE102005050418A1 - Heat-sensitive recording material e.g. for printed images, has intermediate layer containing organic hollow-sphere pigments - Google Patents

Abstract

A heat-sensitive recording material has a carrier/support substrate and two thermo-reaction layers formed on both sides and intermediate layers between the carrier/support substrate and the thermo-reaction layers as well as, depending on requirements, further layers and/or upper layers. At least one of the intermediate layers contains organic hollow-sphere pigments in a binding agent. The binding agent is present in the form of a synthetic and/or natural polymer.

Description

The The invention relates to a heat-sensitive Recording material with a carrier substrate and two on both sides trained thermal reaction layers and with between the carrier substrate and the thermal reaction layers intermediate layers and optionally with further layers and / or top layers.

One thermosensitive Recording material of the type described above results from US-A-6 759 366. This shows on the top and the bottom of the carrier substrate in each case a thermal reaction layer. The carrier substrate is preferably based on cellulose. It is thermally insulating. This is assured that with thermal printing only on the printed side a symbol appears in appearance. Preferably, between carrier substrate and the thermal reaction layers, a primer layer is formed, which serves to improve the adhesion of the layers. Furthermore, should the thermal reaction layer before the action of active ingredients Protect the substrate. The primer layers be based on an aqueous Mixture made mainly Clays contains. About that In addition, the known thermosensitive Recording material so-called topcoats, the other desirable Effect properties of the material.

The from US-A-6,759,366 known heat-sensitive recording material shows several disadvantages: So are the above-mentioned insulating properties not satisfying. When using a thin carrier substrate with normal insulating ability It is necessary to coat the primer layers with a high weight form, otherwise the unwanted breakdown of a would be done to the other side. Would you a stronger one carrier substrate choose, then they are higher Cost, an undesirable high rigidity of the material and a poor nestling of the Thermal head connected to the substrate surface. In addition, at the simultaneous formation of the clay-containing interlayers in the Order of the respective coating difficulties occur so that the rheology properties of the coatings are targeted and must be controlled consuming. After all is the maximum job speed due to the rheological problematic behavior of the clay-containing coating composition limited. Further Disadvantages are that in terms of cost simultaneous formation of the clay-containing intermediate layers in The selection of the order procedure is limited, if that's the reason goes, the printing properties particularly favoring high surface smoothness To achieve intermediate layers.

Of the Invention is therefore based on the object, the above-designated Further develop recording material so that the addressed Disadvantages are resolved. In particular, a satisfactory Insulating effect if possible small basis weight the intermediate layers and low basis weight of the carrier substrate guaranteed become. About that In addition, the intermediate layers should have the opacity of the entire recording material favor, so that a show through of the respective labels of the two Pages of the recording material reduced or largely excluded becomes. The recording material should be inexpensive to produce. Especially should the possibility the simultaneous formation of the mutual intermediate layers and / or the thermal reaction layers at a high coating speed possible be.

According to the invention this Task by a heat-sensitive Solved recording material, the characterized in that at least one of the intermediate layers Hollow spherical organic pigments with a smooth or porous surface in one Contains binder. The person skilled in the art will readily understand what is meant by this is. in principle could the core idea of the invention is the characteristic "organic Hohlkugelpigmente ". A more extensive specification, however, is that the surface is smooth or porous can be. Under "smooth" should the smoothness of a usual Plastic surface be understood. "Porous" should mean that the surface the hollow ball indentations or pores. Furthermore lets that go Wall material of the hollow spheres water outlet too. This will be explained below detailed in detail.

The core idea of the invention is therefore the special design of the intermediate layers, of which at least one intermediate layer contains organic hollow-sphere pigments in a suitable binder. Preferably, the binder is in the form of a synthetic and / or natural polymer. Here, the invention is essentially free to select, unless the desirable thermoreaction is impaired becomes. A binder in the form of water-soluble starches, starch derivatives, hydroxyethylcelluloses, polyvinyl alcohols, modified polyvinyl alcohols, acrylamide (meth) acrylate copolymers and / or acrylamide-acrylate-methacrylate terpolymers is preferred. Such materials result in a coating that is water soluble. On the other hand, in addition to such materials, there are also those which, when the intermediate layers are formed, lead to a water-insoluble structure. These are, for example, latices such as polyacrylate esters, styrene-acrylate ester copolymers, styrene-butadiene copolymers, polyurethanes, acrylate-butadiene copolymers, polyvinyl acetates and / or acrylonitrile-butadiene copolymers and the like. The binder serves in all cases to combine the intermediate layers favorably with the carrier substrate, but also to ensure optimum bonding to the subsequent layer. It is the expert's intention to use here in a particular case a particularly suitable binder or a binder mixture.

The used according to the invention Hollow spherical organic pigments are known in the art. They are in the form of watery Dispersions delivered. In the production of the recording material, the aqueous Dispersions used after inclusion of suitable binders become. In the course of the process for producing the recording material, in which drying processes occur, the aqueous portion of the hollow sphere dispersion with the result that also evaporates within the hollow spheres aqueous Phase is evaporated so that air-filled hollow balls remain. These preferably have a mean particle diameter of about 0.2 to 5 μm, in particular about 0.2 to 1.5 microns. It is particularly advantageous when the organic hollow sphere pigments a void volume of about 20 to 70%, especially about 20 up to 55%. The wall material of the organic hollow sphere pigments is designed so that it on the one hand the required strength on the other hand, the exit of the originally contained therein aqueous Phase allows which by a sufficient porosity is reached. The preparation of such organic hollow sphere pigments is in the state the technique common. Thereafter, their wall material generally consists of organic Polymers, in particular based on styrene-acrylic resins.

Other Wall materials can, what in the expert Action is also taken, provided the desirable Thermal reaction not affected becomes.

It It has been shown that the involvement of the designated organic Hollow sphere pigments to an optimal solution the task set, as described above leads. It's surprising that in the entire manufacturing process with noticeable action of shear forces not impaired in their effect be, as with the here advantageously used order by means of a film press. Surprisingly is the achieved smoothness the intermediate layers even without the aid of additional smoothing measures high, which is advantageous on the quality of the printed image.

It is preferred when both intermediate layers of the heat-sensitive invention Recording material containing organic hollow sphere pigments. The quantitative inclusion This pigment is not subject to any critical limitation. Indeed contains at least one of the intermediate layers, the organic hollow sphere pigments in an amount of from 15 to 85% by weight, in particular from 50 to 70% by weight, based on the dry matter of the interlayer material.

In individual cases It has proven to be advantageous that at least one of the intermediate layers other pigments to control porosity and adsorptivity contains the intermediate layer. The optimization of porosity and the Absoptionsverhaltens have an advantageous effect on the quality of the printed image and on the ability to run in the thermal printer off. Thus, the printed image is optimized by a porosity fixed in a particularly advantageous manner.

at the other pigments that are contained in the intermediate layer can, The invention is also not subject to any critical limitation. Conveniently, These are in the form of natural or precipitated Calcium carbonate, clays or calcined clays, diatomaceous earths, Alumina, aluminum hydroxide, silicas, magnesium silicates and / or Magnesium carbonates before. Also organic pigments can be used in Question, such as urea-formaldehyde condensates and the same.

advantageously, the pigments are changed the particle size optimized and to an average particle size of about 0.1 to 10 μm, in particular from about 1 to 5 μm, set.

Also the selection of the carrier substrate in its chemical nature is not critical. So it can be about a paper carrier based on cellulose fibers, a synthetic paper carrier whose Fibers in particular wholly or partly consist of plastic fibers, but also to act a plastic film.

Preferably, the carrier substrate, the intermediate layers and the thermal reaction layers are adjusted to a favorable basis weight. Thereafter, it is preferred that the carrier substrate has a basis weight of about 20 to 600 g / m ² , in particular from about 40 to 300 g / m ² , the intermediate layers have a basis weight of about 1 to 10 g / m ² , in particular from about 2 to 6 g / m ² , and / or the thermal reaction layers have a basis weight of 1 to 8 g / m ² , in particular about 2 to 6 g / m ² . The total basis weight of the heat-sensitive recording material of the present invention is preferably between about 30 and 650 g / m ² , more preferably between about 40 and 100 g / m ² , to meet the practical requirements.

in the Within the scope of the invention, it is also possible to provide further layers. For example, it may be an outer layer that the Function of a protective layer has. Such exists advantageously from film-forming polymers, such as polyvinyl alcohols, modified Polyvinyl alcohols, polyacrylates and polyurethanes, in the still Pigments are introduced. This may be, for example, aluminum hydroxide, natural or precipitated Calcium carbonate, clay or silica or mixtures of such pigments act. Their particle size is preferably between about 0.1 to 10 microns, in particular between about 0.5 to 2 μm. The function of the protective layer is kept particularly favorable if the film-forming polymer is largely crosslinked. The networking finds in general, by incorporating, in particular, crosslinking favorable Means during drying of the used in the formation of the protective layer Coating mass instead.

at the selection of the color former and the color developer within the formed according to the invention Thermal reaction layers, there is no relevant restriction. there it is preferred to use color formers in the form of 2-anilino-3-methyl-6-diethylamino-fluoran, 2-anilino-3-methyl-6-di-n-buthylamino-fluoran, 2-anilino-3-methyl-6- (N-ethyl-, N-p-toluidinoamino) -fluoran, 2-anilino-3-methyl-6- (N-methyl-, N-propyl-amino) -fluoran, and / or 3,3-bis (4-dimethylaminophenyl) -6-dimethyl-amino-phthalide, and the color developers in the form of phenolic derivatives such as 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, 4-hydroxy-4'-iso-propoxy-diphenyl sulfone, Bis- (3-allyl-4-hydroxyphenyl) sulfone, 2,2-bis- (4-hydroxyphenyl) -4-methyl-pentane, N- (benzenesulfonyl) -N '- (3-p-toluenesulfonyl-oxy-phenyl) -urea, Zinc salts of derivatives of salicylic acid, the binder in the form of water-soluble Strengthen, Starch derivatives, Hydroxyethylcelluloses, polyvinyl alcohols, acrylamide (meth) acrylate copolymers, Acrylamide-acrylate-methacrylate terpolymers and / or latices, such as Polyacrylates, poly (meth) acrylic esters, Styrene-butadiene copolymers, polyurethanes, acrylate-butadiene copolymers. In the thermal reaction layer can still various other properties or substances favoring the property be included. This can be, for example, sensitizing Melting aids, lubricants, rheological aids, fluorescent Substances and the like.

The sensitizing melt aids are e.g. in the form of 2-Benzyloxy-naphthalene (BON), p-benzylbiphenyl (PBBP), oxalic acid dibenzyl ester, Oxalic acid-di (p-methylbenzyl) ester, 1,2-bis (phenoxy-methyl) benzene, 4- (4-tolyloxy) biphenyl, ethylene glycol diphenyl ether, Ethylene glycol m-tolyl ether and 1,2-bis (3,4-dimethyl-phenyl) -ethane and the lubricants in the form of fatty acid amides, such as. Stearic acid amide, fatty acid alkanolamides, such as Stearic acid methylolamide, Ethylene-bis-alkanoylamides, such as. B. Ethylene-bis-stearoylamide, synthetic Grow, such. B. paraffin waxes of various melting points, ester waxes different molecular weights, ethylene waxes, propylene waxes different hardnesses or natural Grow, such. As carnauba wax and / or fatty acid metal soaps, such as. Zinc stearate, Calcium stearate or behenate salts, the rheology aids in the form of water-soluble Hydrocolloids, e.g. Strengthen, Starch derivatives, Sodium alginates, polyvinyl alcohols, methylcelluloses, hydroxyethyl or hydroxypropylmethylcelluloses, carboxymethylcelluloses, poly (meth) acrylates, the optical brighteners in the form of whiteners z. B. from the substance groups Diaminostilbene-disulfonic acid, Distyryl-biphenyls, benzoxazole derivatives, the fluorescent substances in the form of daylight fluorescent pigments of different shades or fluorescent fibers, the aging inhibitor in the form of steric hindered phenols, e.g. 1.1.3-tris (2-methyl-4-hydroxy-5-cyclohexyl-phenyl) butane, 1.1.3-Tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1'-bis (2-methyl-4-hydroxy-5-tert-butyl-phenyl) -butane and 1,1'-bis (4-hydroxyphenyl) cyclohexane.

from Principle forth with the formation of the heat-sensitive invention Recording material, which has been presented above, a functional material available. It is useful in some cases, more Layers on-line or off-line on the thermal reaction layer as Protective layer and / or as a the printability favoring Train shift.

The skilled person are various methods available to the heat-sensitive Aufzeich produce material according to the invention. Thus, for example, both sides of the carrier substrate can be provided on-line in the paper machine simultaneously with the coating compound for forming the intermediate layers. It is also possible first to provide the one and then the other side of the carrier substrate with intermediate layers. The respective order procedure is therefore subject to no restrictions and can be carried out in the usual way. The same applies to the formation of the thermal reaction layer, in which an aqueous dispersion containing the necessary and promoting constituents is applied and dried in a conventional manner. The skilled person therefore requires no further technical instructions.

The Advantages associated with the present invention leave essentially summarized as follows: the two thermal reaction layers are excellently isolated during the thermal printing process. This leads to high quality printing. This will be at a small basis weight reached the intermediate layers. The intermediate layers favor continue the opacity of the recording material, so that a show through the respective Labels of both sides of the recording material reduced or excluded as far as possible. The recording material is economical and technically easy to manufacture. This can with high coating speeds, which is true for all layers applies.

The Invention is intended below by way of non-limiting Examples are presented in detail:

The order of an application suspension for forming the intermediate layer of a thermal paper was done on both sides online in the paper machine by means of a film press at an operating speed of 1300 m / min on a paper web of a basis weight of 43 g / m ² . After the application of the aqueous application suspension, the drying process of the coated paper support took place in the usual way (note: all information given here relates to otro weight percent (oven-dry)).

Based the information given above, a thermal paper was produced, the following formulations of aqueous coating suspensions to form a composite structure with intermediate layer on a carrier substrate were used and then the other layers, in particular thermal reaction layer, were formed in a conventional manner.

An aqueous coating suspension containing a hollow sphere pigment was used in accordance with the procedure described above to produce a composite of paper support and intermediate layer. Recipe 1:

Remarks:

• ^{* 1} styrene-butadiene latex type binder
• ^{* 2} hollow sphere pigment Fa. (Rohm & Haas) (styrene-acrylate polymer / smooth surface / diameter: about 1 micron, wall diameter: about 0.1 micron)
• ^{* 3} optical brightener (anionic stilbene derivative) (Clariant company)
• ^{* 4} Sterocoll type (BASF) (copolymer of acrylic acid esters and carboxylic acids)

The coating composition given above gives a dry content of about 29.2% by weight. Further information: pH 7.8 to 8.2; Viscosity (according to Brookfield 100 rpm, spindle 3, 20 ° C) 400 mPas. The total application (both sides) took place with about 6 g / m ² (otro) on the paper support. Recipe 2:

Remarks:

• ^{* 1} Dispex type (Allied Colloids)
• ^{* 2} styrene-butadiene latex type binders
• ^{* 3} calcined kaolin (Engelhard)
• ^{* 4} hollow sphere pigment (Dow) (particle diameter: about 1 μm)
• ^{* 5} optical brightener (see above)
• ^{* 6} Sterocoll type (BASF) (see above)

The Composition corresponded with the exception of Formulation 1 that a pigment mixture of a hollow sphere pigment and an inorganic one Pigment was used. The coating weight according to recipe 2 gave the following Key figures: dry content of about 32.8% by weight, pH 8.0-8.4, Viscosity (after Brookfield 100 rpm, spindle 3, 20 ° C) 450 mPas.

The total application (both sides) took place at about 7.0 g / m ² (otro) on the paper support. Recipe 3:

Remarks:

• ^{* 1} Dispex type (Allied Colloids / CIBA)
• ^{* 2} styrene-butadiene latex type binders
• ^{* 3} urea-formaldehyde resin (Martinswerke)
• ^{* 4} hollow sphere pigment (Rohm & Haas) (see above)
• ^{* 5} optical brightener (see above)
• ^{* 6} Sterocoll type (BASF) (see above)

The Composition corresponded to Formulation 1 except that a pigment mixture of a hollow sphere pigment and a urea-formaldehyde condensate was used.

The coating weight according to recipe 3 gave the following characteristics: dry content of about 32.8% by weight, pH 7.9 to 8.3, viscosity (according to Brookfield 100 rpm, spindle 3, 20 ° C.) 480 mPas. The total application (two-sided) took place at about 6.5 h / m ² (otro) on the paper support.

The order of an aqueous application suspension for forming the thermal reaction layer on the formed intermediate layers was carried out by means of the curtain coating process. The viscosity of the aqueous coating suspension was about 450 mPas (according to Brookfield, 100 rpm, 20 ° C.) (deaerated state). Their surface tension was 46 mN / m (statistical ring method). The coating was arranged in-line. The application of the aqueous application suspension was carried out on one side of the composite paper support and intermediate layer with a basis weight of about 50 g / m ² . The curtain coating process was operated at a speed of 1300 m / min. After application of the aqueous application suspension, the drying process of the coated paper support was carried out in a customary manner. In the same way, the coating was done on the back.

A aqueous Application suspension was prepared as follows: First an aqueous one Dispersion of the color former by milling 20 parts by weight of 2-anilino-3-methyl-6- (N-ethyl, N-isopentyl-amino) -fluoran with 35 parts by weight of a 15% aqueous polyvinyl alcohol in a mill produced. Then a watery Color developer dispersion by milling 45 parts by weight of 2,2-bis (4-hydroxyphenyl) propane together with 30 parts by weight of a 15% aqueous polyvinyl alcohol solution in a mill produced. This was followed by the production of a heat-meltable Dispersion. This was prepared by milling 50 parts by weight of benzyl naphthyl ether with 30 parts by weight of a 15% aqueous polyvinyl alcohol solution in a mill produced. These three starting dispersions were in a simple Mixer with 200 parts by weight of a 55% dispersion of a precipitated calcium carbonate, 50 parts by weight of a 25% ethylene-bis-stearic acid amide dispersion, 50 parts by weight of a 20% zinc stearate dispersion and 280 parts a 10% aqueous polyvinyl alcohol mixed well.

The resulting aqueous coating composition gives a dry content of about 36.5 wt .-%. Further on 460 mPas viscosity of the vented coating (according to Brookfield 100 rpm, spindle 3, 20 ° C).

The heat-sensitive coating suspension thus obtained was used to prepare a thermosensitive recording material in the form of a thermal paper by the above-described procedure. The order was carried out with 5.0 g / m ² (otro) on the front and back of the paper carrier.

Claims (17)

Heat-sensitive recording material having a carrier substrate and two thermoreactive layers formed on both sides and intermediate layers present between the carrier substrate and the thermal reaction layers and optionally further layers and / or top layers, characterized in that at least one of the intermediate layers contains organic hollow-sphere pigments in a binder. Recording material according to claim 1, characterized that the binder is in the form of a synthetic and / or natural Polymer is present. Recording material according to claim 2, characterized in that in that the binder is in the form of water-soluble starches, starch derivatives, hydroxyethylcelluloses, Polyvinyl alcohols, modified polyvinyl alcohols, acrylamide (meth) acrylate copolymers and / or latices, such as polyacrylates, styrene-butadiene copolymers, Polyurethanes, acrylate-butadiene copolymers, Polyvinyl acetates and / or acrylonitrile-butadiene copolymers present. Recording material according to one of claims 1 to 3, characterized in that the organic hollow sphere pigments an average diameter of about 0.2 to 5 microns, in particular about 0.5 to 1.5 μm, exhibit. Recording material according to at least one of the preceding Claims, characterized in that the organic hollow sphere pigments a void volume of about 20 to 70%, especially about 20 up to 55%. Recording material according to at least one of the preceding Claims, characterized in that the wall material of the organic hollow sphere pigments based on organic polymers, in particular styrene / acrylic resins. Recording material according to one of the preceding Claims, characterized in that both intermediate layers, the organic Hollow sphere pigments included. Recording material according to one of the preceding Claims, characterized in that at least one of the intermediate layers the organic hollow-sphere pigments in an amount of 15 to 90% by weight, in particular from 50 to 80 wt .-%, based on dry matter. Recording material according to at least one of the preceding Claims, characterized in that at least one of the intermediate layers other pigments to control porosity and adsorptivity contains the intermediate layer. Recording material according to claim 9, characterized that the further pigments are in the form of natural or precipitated calcium carbonate, Clays or calcined clays, diatomaceous earths, alumina, aluminum hydroxide, silicas, Magnesium silicates and / or magnesium carbonates. Recording material according to claim 9 or 10, characterized characterized in that the further pigments have a particle size of about 0.1 to 10 μm, in particular from about 1 to 5 μm, exhibit. Recording material after at least one of previous claims, characterized in that included for property favorability further additives are, in particular optical brighteners. Recording material according to at least one of the preceding claims, characterized in that the carrier substrate is a cellulose fiber-based paper carrier, a synthetic paper carrier, whose fibers are wholly or partly made of plastic fibers, or is a plastic film. Recording material according to at least one of the preceding claims, characterized in that the carrier substrate has a basis weight of about 20 to 600 g / m ² , in particular from about 40 to 300 g / m ² , the intermediate layers has a basis weight of about 1 to 12 g / m ² , In particular from about 2 to 7 g / m ² , and / or the Thermoreakti onsschichten a basis weight of 1 to 8 g / m ² , in particular about 2 to 6 g / m ² , have. Recording material after at least one of previous claims, characterized in that it is a protective layer as outer layer of film-forming polymers containing pigments. Recording material according to claim 15, characterized characterized in that the film-forming polymer is crosslinked. Recording material according to at least one of the preceding claims, characterized in that the basis weight of the recording material is between about 30 and 650 g / m ² , in particular between about 40 and 100 g / m ² .