JPH03239585A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide sufficient dynamic characteristics and to perform highly detailed printing by successively providing an undercoat layer based on a film forming hydrophobic polymer, a thermal color forming layer and a protective layer on a support composed of a polyolefinic cross-laminated film. CONSTITUTION:A polyolefinic cross-laminated film is formed by laminating two films oriented in a direction of 45 deg. with respect to a flow direction so as to cross both films mutually. A hydrophobic polymer having glass transition temp. (Tg) of 50 deg.C or lower is used in an under layer and, as the hydrophobic polymer, at least one of SBR, a styrene/acrylic ester copolymer and a styrene/ methacrylic ester copolymer is designated. It is necessary to use a polymer binder having good film forming properties in a protective layer as a main component and a water-soluble resin is pref. and used by mixing latex with said resin or adding a water resistance imparting agent thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a heat-sensitive recording material that has excellent mechanical strength, typified by tear strength, and excellent recording sensitivity.

<Prior Art> Generally, a heat-sensitive recording material having a heat-sensitive recording layer mainly composed of a colorless or light-colored leuco dye and a color developer that develops color by reacting with the leuco dye when heated is disclosed in Japanese Patent Publication No. 4514035, It has been widely put into practical use. A thermal printer with a built-in thermal head is used to record on this thermal recording medium, but this thermal recording method produces less noise during recording than other recording methods that have been put to practical use. Excellent, no need for developing and fixing. Due to its features such as being maintenance-free, the equipment is relatively inexpensive and compact, and the resulting colors are very clear, it is useful for computer output, facsimiles, recorders such as calculators and measuring machines, and ticket paper for automatic ticket vending machines. It is widely used for labeling purposes.

In recent years, one field of application of the above-mentioned heat-sensitive recording that has rapidly become popular is airline rigs.

An airline tag is attached to the luggage of passengers traveling on an aircraft in order to identify its owner, destination, etc. The environment in which they are used is harsh, and when they are moved, they rub against other items or get caught between items, which can cause damage to the recording part due to scratches, and damage to the tag itself due to tearing force if pulled. There are many things that occur.

Conventionally, heat-sensitive recording paper for airline tags used under such harsh conditions has been laminated with a synthetic resin film, which has a protective layer on a heat-sensitive coloring layer, to provide mechanical strength to the synthetic resin film. Techniques such as having it held in the

However, laminating thermal recording paper and film increases the manufacturing process and costs, and the adhesive used when laminating thermal recording paper and film may cause background coloring on the thermal paper, or the cross-section of the adhesive may Problems such as damage to the thermal head may occur due to protrusion from the film, and damage due to tearing may occur depending on the selection of the synthetic resin film.

Furthermore, due to the recent trend toward higher resolution printing with thermal barcode printers, thermal recording media using paper supports have limited reproducibility of minute dots, and from this point of view, thermal recording media with higher performance The appearance of the body was desired.

<Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned problems. Specifically, the present invention has been made in view of the above-mentioned problems. The purpose of the present invention is to provide a heat-sensitive recording material that can be used.

<Means for Solving the Problems> The present invention provides an under layer containing a film-forming hydrophobic polymer as a main component, a colorless or light-colored leuco dye, and a color developer on a support made of a polyolefin cross-laminated film. This is a heat-sensitive recording material which is formed by sequentially providing a heat-sensitive coloring layer and a protective layer containing as the main components. There is a heat-sensitive recording material that is characterized by pasting.

The components of the present invention will be described in detail below.

The polyolefin cross-laminated film, which is the support of the heat-sensitive recording material of the present invention, is produced by laminating two films oriented at 45 degrees to the flow direction so as to cross each other in a lamination process. The intermediate adhesive layer is laminated using polyolefin resin. Its feature is that it maintains the flexibility and strength of a polyolefin film, while reducing the tear strength of the film in the orientation direction by cross-laminating it, making it a material with little mechanical anisotropy. The preferred thickness of the support constituting the heat-sensitive recording material of the present invention is about 50 to 100 μm, and is characterized in that sufficient strength can be obtained with a relatively small thickness.

Further, the surface of the support used in the present invention is preferably subjected to corona discharge treatment in order to improve adhesion, which is a drawback of polyolefin films.

Next, the under layer constituting the heat-sensitive recording medium of the present invention is provided for the purpose of improving the adhesiveness between the support and the heat-sensitive color forming layer, and improving the recording sensitivity and printing accuracy. The hydrophobic polymer in the under layer is thought to work effectively to prevent the thermal energy transferred to the thermosensitive coloring layer from diffusing to the cross-laminated film support, and the lower the Tg, the greater the heat insulating effect. This is effective in improving recording sensitivity and printing accuracy. Therefore, the under layer in the present invention has a glass transition temperature (Tg) of 50°C or less, more preferably 30°C.
The following hydrophobic polymers are used. Examples of the hydrophobic polymer include at least one of SBR, styrene-acrylic ester copolymer, and styrene-methacrylic ester copolymer. Although it is possible to use an organic solvent-soluble resin as the hydrophobic polymer, since the residual organic solvent has an effect such as causing background fog in the heat-sensitive coloring layer, it is not possible to use an aqueous latex or emulsion type resin. It is preferable to use

Furthermore, pigments may be added to the under layer constituting the present invention, if necessary.

Pigments that may be added to the under layer as necessary include inorganic and organic pigments, such as heavy and light calcium carbonate,
Examples include aluminum hydroxide, titanium oxide, zinc oxide, barium sulfate, talc, clay, satin white, kaolinite, polyolefin particles, polystyrene particles, urea-formalin resin particles, and the like. The weight mixing ratio of the hydrophobic polymer and the pigment in the under layer is in the range of 1O20 to 1:9, preferably 1O00 to 3Nia from the viewpoint of recording properties. Further, the thickness of the under layer is preferably 1 μm or more, preferably 3 μm or more from the viewpoint of recording characteristics.

The heat-sensitive color forming layer of the heat-sensitive recording material of the present invention contains as main components a colorless or light-colored leuco dye and a color developer that causes the leuco dye to develop color.

Typical leuco dyes used include crystal violet lactone, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6-methyl-7-
Chlorofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylami/-7-dibenzylaminofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl- 7-
Anilinofluorane, 3-cyclohexylmethylamino-6-methyl-7-anilinofluorane, 3-ethylisoamylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7-(0-chloroanilino) Examples include, but are not limited to, fluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, and the like.

In addition, the color developer that reacts with the above leuco dye to develop color includes α-naphthol, β-naphthol, 4-[-butylphenol, 4-1-octylphenol, 4-phenylphenol, 2.2-bis(p- hydroxyphenyl)propane, 2゜2-bis(p-hydroxyphenyl)butane, 4゜4'-cyclohexylidene diphenol, 2.2-bis(2,5-dibromo-4-hydroxyphenyl)furopane, 4.4 '-isopropylidene bis(2-[-butylphenol), 2.2'-methylenebis(4-chlorophenol), 4.4'-sulfonyldiphenol, 4.4'-thiobisphenol, benzoic acid, salicylic acid, gallic acid, etc. derivatives, etc., but are not limited to these.

Furthermore, in the present invention, in order to improve recording sensitivity,
Various thermofusible substances can be added to the heat-sensitive coloring layer as necessary. Examples of thermofusible substances include organic compounds with a suitable melting point, such as higher fatty acid amides such as stearic acid amide, animal waxes such as beeswax and Sierra black wax, vegetable waxes such as carnauba wax, and montane waxes. Mineral waxes such as wax, waxes such as paraffin wax and microcrystalline wax, higher fatty acids, higher fatty acid esters, aromatic carboxylic acid esters such as dimethyl terephthalate and diphenyl phthalate, alkylnaphthalene derivatives, alkyldiphenyl derivatives, alkaline ether Phenyl derivatives and the like are used.

The above-mentioned leuco dye, color developer, and thermofusible substance added as necessary are pulverized using a media-type wet dispersion machine and prepared as dispersion waves, and the particle size of the dispersed elements is as follows:
It is 5 μm or less, preferably 3 μm or less.

Furthermore, the heat-sensitive coloring layer of the present invention may contain inorganic and organic pigments as fillers, such as heavy and light calcium carbonate, aluminum hydroxide, titanium oxide, zinc oxide, barium sulfate, talc, cresatin white, kaolinite. , polyolefin particles, polystyrene particles, urea-formalin resin particles, etc. can be added to improve the clarity of the colored image.

In addition, various surfactants, antifoaming agents, antioxidants, ultraviolet absorbers, etc. may be added to the heat-sensitive coloring layer as necessary. Examples of binders for binding the materials constituting the heat-sensitive coloring layer include casein, gelatin, polyvinyl alcohol, polyvinylpyrrolidone, starch, modified starch, inbutylene-maleic anhydride resin, diisobutylene-maleic anhydride resin. , styrene-maleic anhydride resin, polyacrylamide, modified polyacrylamide, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, further vinyl acetate, acrylic ester,
Vinyl chloride-vinyl acetate copolymers, emulsions such as SBR and NOR, latte, and sous creams can be used alone or in combination.

The protective layer constituting the heat-sensitive recording material of the present invention is provided for the purpose of preventing pressure coloring caused by smearing, scratching, etc. and preventing chemicals from entering the heat-sensitive coloring layer, so it is basically made of a polymer with good film-forming properties. It is necessary to have a binder as the main component. This polymer binder can be a water-soluble or water-insoluble resin binder, which is the material used in the heat-sensitive coloring layer, but it is not suitable for the purpose of preventing the penetration of lipophilic chemicals such as plasticizers and pigments. , water-soluble resins are preferred. However, since water-soluble resin binders have poor water resistance, they may be mixed with emulsions, latex, etc., or made with water-resistant materials such as Griot Gyuzaar, Chrome Minghan, melamine resin, melamine formaldehyde resin, polyamide resin, boamide-epichlorohydrin resin, etc. It is desirable to use the agent by adding it to the water-soluble resin.

Moreover, various surfactants and antifoaming agents can be added as necessary.

In addition to the film-forming polymer binder mentioned above, the protective layer may contain inorganic or organic pigments, lubricants such as zinc stearate and calcium stearate, and fluorine resins, etc., as necessary to obtain mating properties with the thermal head. It is desirable to add a mold release agent.

The under layer, heat-sensitive coloring layer and protective layer having the above compositions are prepared by sequentially applying paint to the surface of the support using a known coating method such as air knife coach ink, roll coating, bar coating, or blade coating. A coating layer is formed by drying. Note that a back coat may be provided on the back surface of the support constituting the heat-sensitive recording material of the present invention for the purpose of preventing curling, etc., if necessary.

Further, the heat-sensitive recording material of the present invention is used by pasting an adhesive layer and a release sheet such as a silicone-treated release paper on the opposite side of the support surface coated with the above-mentioned under layer, heat-sensitive coloring layer, and protective layer. You can also do that.

Examples of the adhesive used in the adhesive layer include polyacrylic acid ester adhesives commonly known as pressure-sensitive adhesives.

<Examples> Next, the present invention will be described in detail with reference to Examples and Comparative Examples. Note that all parts in Examples and Comparative Examples represent parts by weight.

(Example 1) A 75 μm thick polyolefin cross-laminated film (manufactured by Sunresoku Kogyo Co., Ltd., trade name: KM Film 750W) treated with corona discharge was used as a support, and styrene-butadiene latex with a solid content concentration of 50% was used. (Tg
0°C) to a dry weight of 4 g/m'' to form an under layer.

Next, in order to prepare a paint for the heat-sensitive coloring layer, a mixture having the following composition was dispersed using a sand mill, and dispersions [A] to [C
] was adjusted.

[A] 1ffl [B] Solution [C] Solution Using the dispersions of [A] to [C] obtained as above, a heat-sensitive coloring layer paint with the following formulation was prepared, and dried on the under layer. A thermosensitive coloring layer was formed by coating to a weight of 7 g/m''.

Furthermore, a paint having the following formulation was prepared as a paint for the protective layer, and was applied onto the heat-sensitive coloring layer to a dry weight of 4 g/m''.

A polyacrylic acid ester emulsion adhesive was used on the back side of the support on which the under layer, thermosensitive coloring layer, and protective layer were formed, and the silicone-treated release paper was bonded to the back surface to obtain the thermosensitive recording material of the present invention. .

(Example 2) A styrene-methyl methacrylate-2-ethylhexyl methacrylate copolymer emulsion having a Tg of 30°C was placed on the cross-laminated film subjected to the corona discharge treatment of Example 1 at a dry type ff14 g/m”. A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that the under layer was formed.

(Example 3) Using the cross-laminated film subjected to the corona discharge treatment of Example 1, emulsion 1 containing 40% solids of styrene-acrylic acid ester copolymer with Tg of 15°C was prepared.
00 parts, 50 parts of a 30% by weight titanium oxide aqueous dispersion was added and applied to a dry weight of 6 g/m''.
A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the under layer was formed.

(Comparative Example 1) A comparative heat-sensitive recording material was obtained in the same manner as in Example 1 except that the cross-laminated film of Example 1 was used as the support and no under layer was applied.

(Comparative Example 2) A comparative thermosensitive recording material was obtained in the same manner as in Example 1 except that 150 ttm high quality paper was used as the support.

(Comparative Example 3) A comparative heat-sensitive recording material was obtained in the same manner as in Example 1 except that a 100 μm opalescent polyethylene terephthalate film was used as the support.

(Comparative Example 4) Using a 50 μm paper support as a support, an under layer, a thermosensitive coloring layer, and a protective layer were formed in the same manner as in Example 1, and then laminated with a 100 μm milky white polyethylene terephthalate film, and further coated on the back side. A heat-sensitive recording material for comparison was obtained by laminating a silicone-treated release paper using a polyacrylic acid ester emulsion adhesive.

The thermal recording materials of the above Examples and Comparative Examples were printed using a thermal printing device manufactured by Enshita Electronic Parts Co., Ltd. with an applied power of 0.5 W/dot and a pulse width of 1.0 m5ec, and the print density was measured using a Macbeth reflection densitometer. Measured and recorded with RD-914 iMV
was evaluated. In addition, barcodes were printed using a thermal barcode printer manufactured by Antonson Avery, and barcode accuracy was visually determined.

Furthermore, the tear strength in the longitudinal and lateral directions was measured for the heat-sensitive recording materials of Examples and Comparative Examples before adhesive processing was applied to the back surface using an Elmendorf type tear tester based on JIS P-8116, and the mechanical strength was determined. evaluated.

The above evaluation results are shown in Table 1.

Table 1 As is clear from Table 1, the heat-sensitive recording material of the present invention not only has high mechanical strength represented by tear strength, but also has high recording sensitivity and excellent recording clarity. there were.

<Effects of the Invention> Since the heat-sensitive recording material of the present invention uses a polyolefin cross-laminated film as a support, tearing strength in random directions, especially tearing from the periphery (edge) of the heat-sensitive recording material, is low. Due to its excellent strength, it could not only withstand practical use even under harsh usage conditions, but also had extremely good recording characteristics in terms of recording density and bar food sharpness.

Claims (1)

[Scope of Claims] 1) An under layer containing a hydrophobic polymer as a main component on a support made of a polyolefin cross-laminated film;
A heat-sensitive recording material characterized by sequentially providing a heat-sensitive coloring layer and a protective layer containing a colorless or light-colored leuco dye and a color developer as main components. 2) An under layer mainly composed of a hydrophobic polymer on a support made of a polyolefin cross-laminated film,
A heat-sensitive recording characterized in that a heat-sensitive coloring layer containing a colorless or light-colored leuco dye and a color developer as main components and a protective layer are sequentially provided, and a release sheet is attached to the other side of the support via an adhesive layer. body. 3) Glass transition temperature (Tg) of the hydrophobic polymer in the under layer
) is 50°C or less, the heat-sensitive recording material according to claim 1.