JP4519671B2 - Thermal recording material - Google Patents

Description

  The present invention relates to a thermosensitive recording medium provided with a thermosensitive recording layer and an overcoat layer containing at least an electron donor composed of a colorless or light leuco dye and an electron acceptor on a support. The present invention relates to a heat-sensitive recording material that has little stickiness and less adhesion of the heat-sensitive surface even if water is attached to the surface.

  A heat-sensitive recording material provided with a heat-sensitive recording layer containing an electron donor composed of a colorless or light leuco dye and an electron acceptor composed of a developer can produce a recorded image with a relatively simple device and does not generate noise. For example, it is used in a wide range of fields such as facsimiles, label printers, handy terminals, registers, ticket vending machines, recorders, etc.

  However, a heat-sensitive recording layer containing an electron donor composed of a colorless or light leuco dye and an electron acceptor composed of a developer and an overcoat layer on the heat-sensitive recording layer are wet with water. When the heat-sensitive surfaces provided with the heat-sensitive recording layer come into contact with each other, the heat-sensitive recording layer may peel off and the image may become unclear.

Also, it may be used outside even in rainy weather, such as a handheld terminal for meter reading. If rain adheres to thermal recording paper, stickiness and adhesion may occur, and these improvements are desired (for example, patent documents). 1 or Patent Document 2).
JP-A-11-0778240 Japanese Patent Application Laid-Open No. 11-078241

  Accordingly, an object of the present invention is to provide a heat-sensitive recording material that does not cause stickiness or adhesion even when wet.

The present invention, as a result of intensive studies to solve the above problems, as a resin of the overcoat layer provided on the support of the heat-sensitive recording medium, by containing a Veova acrylic resin, even if it gets wet, The inventors found that no adhesion occurred and completed the present invention. That is, the heat-sensitive recording material according to the present invention comprises a heat-sensitive recording layer containing at least a leuco dye and a developer that causes the leuco dye to develop color when heated, and an overcoat layer on the heat-sensitive recording layer. sensitive recording body provided, the overcoat layer is characterized by containing only Beobaakuriru resin as a resin component serving as an adhesive. Here, the heat-sensitive recording material according to the present invention includes a form in which the overcoat layer does not contain a waterproofing agent.

  In the heat-sensitive recording material according to the present invention, when the heat-sensitive recording material is immersed in tap water for 5 seconds and then the surfaces on the heat-sensitive recording layer side are brought into contact with each other and dried at room temperature, the surfaces do not adhere to each other, and The heat-sensitive recording layer is preferably not peeled off.

  The thermosensitive recording material according to the present invention includes a case where an undercoat layer is provided on the support as a lower layer of the thermosensitive recording layer.

  When the heat-sensitive recording paper of the present invention is immersed in tap water for 5 seconds and then brought into contact with each other and dried at room temperature, the heat-sensitive recording paper does not adhere to each other when peeled off. Further, even when a drop of water was dropped on the heat-sensitive surface and touched by hand, it had a non-sticky property.

  Hereinafter, the present invention will be described in detail, but the present invention is not construed as being limited to these descriptions. That is, the main main components used in the heat-sensitive recording material are specifically described below, but are not limited thereto.

The heat-sensitive recording material according to the present embodiment comprises a heat-sensitive recording layer containing at least a leuco dye and a developer that causes the leuco dye to develop a color when heated, and an overcoat layer on the heat-sensitive recording layer. sensitive recording body provided, the overcoat layer contains only Beobaakuriru resin as a resin component serving as an adhesive. The case where an undercoat layer is provided on the support as the lower layer of the heat-sensitive recording layer is included. At this time, an undercoat layer, a heat-sensitive recording layer, and an overcoat layer are sequentially formed on the support. Note that other layers may be provided between the undercoat layer, the heat-sensitive recording layer, and the overcoat layer as long as they do not contradict the gist of the present invention, and the undercoat layer, the heat-sensitive recording layer, or the overcoat layer may be provided. Each may be formed of a plurality of layers. For example, in the case of a heat-sensitive recording layer, a two-layer structure of a high temperature coloring layer and a low temperature coloring layer may be used. The present invention is characterized in that a baobaacrylic resin is contained as a resin component in the overcoat layer of the heat-sensitive recording material. Veova acrylic resin mainly serves as an adhesive for the overcoat layer.

  As the support, paper, plastic film, synthetic paper, or a composite thereof is used. The support is not particularly limited as long as it can be formed into a sheet.

The undercoat layer is provided between the support and the heat-sensitive recording layer in order to improve characteristics such as color uniformity. This undercoat layer is composed of inorganic pigments such as kaolin, clay, talc, calcium carbonate, aluminum hydroxide, calcined clay, titanium oxide, and particulate anhydrous silica, and / or organic materials such as styrene, styrene / acrylic copolymer, and urea resin. Pigments and water-soluble and water-dispersible resins such as polyvinyl alcohol, methylcellulose, starch, carboxymethylcellulose, hydroxyethylcellulose, casein, acrylate copolymer latex, and styrene / butadiene copolymer latex It is selected as described above, prepared as an undercoat coating liquid, and this undercoat coating liquid is applied on a support and dried. The coating amount of the undercoat layer is, for example, 3 to 10 g / m ² , preferably 5 to 8 g / m ² in terms of dry mass.

  The heat-sensitive recording layer may contain a leuco dye and a developer that causes the leuco dye to develop color when heated, and may contain a sensitizer or an anti-sticking agent used to increase recording sensitivity. Furthermore, an adhesive that holds them together may be contained. You may add a hardening | curing agent as needed.

  Various known leuco dyes such as leuco dyes specifically described in Patent Document 1 or Patent Document 2 can be used as the electron donor made of a colorless or light leuco dye used in the heat-sensitive recording layer. Specific examples thereof include the following. [2-anilide-6- (N-ethyl-N-isopentylamino) -3-methyl] xanthene-9-spiro-1 ′-(3′-isobenzofuranone), 3-N-methyl-N-cyclohexyl Amino-6-methyl-7-anilinofluorane, 3-Nn-propylmethylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 2- (2′-chloroanilino) -6-di-n-butylanilinofluorane, and the like. Of course, it is not limited to these, Two or more types can also be used together as needed.

  As an electron acceptor serving as a developer used together with an electron donor composed of a colorless or light leuco dye, various known developers such as a developer specifically described in Patent Document 1 or Patent Document 2 are used. The agent can be used. For example, 2,2bis (4′-oxyphenyl) 2-propane, 4-4′-dihydroxydiphenyl sulfone, 2,4′-dihydroxydiphenyl sulfone, paraoxybenzoic acid benzyl ester, 4-hydroxy-4′-iso Although propoxy diphenyl sulfone, bis- (3-allyl-4-hydroxyphenyl) -sulfone, etc. are mentioned, it is not limited to this.

  As the sensitizer, various known sensitizers such as a sensitizer specifically described as a sensitivity improver in Patent Document 1 or Patent Document 2 can be used. Specific examples thereof include the following, but are not limited thereto. Parabenzylbiphenyl, dibenzyl terephthalate, 1,2-bis (3,4-dimethylphenyl) ethane, metaterphenyl, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid (P-methylbenzyl), dimethyl terephthalate Such as esters.

Preparation of a coating liquid containing an electron donor composed of the above colorless or light leuco dye, an electron acceptor serving as a developer, and a sensitizer is generally carried out using water as a dispersion medium and stirring such as attritor, ball mill, and sand grinder.・ Use a pulverizer to disperse each heat-sensitive material separately or finely disperse two or more types together with a dispersant so that the average particle size is about 0.5 to 3 μm, then add an adhesive, and stir and mix. Prepare. This is coated on a support or an undercoat layer and dried to form a thermosensitive recording layer. The coating amount of the thermosensitive recording layer is, for example, 3 to 10 g / m ² , preferably 5 to 7 g / m ² in terms of dry mass.

  Specific examples of the adhesive used here include water-soluble and water-dispersible resins such as polyvinyl alcohol, methyl cellulose, starch, carboxymethyl cellulose, hydroxyethyl cellulose, casein, and acrylate copolymer latex. Polyvinyl alcohol, methyl cellulose, starch, carboxymethyl cellulose, hydroxyethyl cellulose, casein, and acrylate copolymer latex are added in an amount of 5 to 50% by mass, preferably about 10 to 30% by mass based on the total solid content.

  Furthermore, an anti-sticking agent may be added to the coating solution so that the thermal recording material does not cause sticking due to contact with the recording device or the recording head. Anti-sticking agents include dispersions of zinc stearate, calcium stearate, paraffin wax, etc. and kaolin, clay, talc, calcium carbonate, aluminum hydroxide, calcined clay, oxidation to improve adhesion of recording head residue. There are inorganic pigments such as titanium and fine anhydrous silica.

The heat-sensitive recording material according to the present embodiment contains only Beobaakuriru resin as a resin component which becomes adhesive in the overcoat layer. If a water-soluble resin such as polyvinyl alcohol is used as an adhesive instead of using a veobaacrylic resin, it will stick to the finger when touched by water, or adhere when the heat sensitive surfaces are stacked. Here, the content of the veobaacrylic resin contained in the overcoat layer is 100 % by mass of the total resin amount contained in the overcoat layer. A high content is preferable. When the content of the veobaacrylic resin is less than 50% by mass, stickiness when touched with water occurs, and adhesion between heat-sensitive surfaces occurs.

In the overcoat layer, calcium carbonate, zinc oxide, titanium oxide, aluminum hydroxide, kaolin, talc, clay, or the like may be contained as a pigment for the purpose of improving matching with the thermal head. Moreover, you may contain zinc stearate, paraffin wax, etc. as a lubricant. The pigments and lubricants can be used alone or in combination of two or more. Of course, it is not limited to these. The overcoat layer is formed by preparing an overcoat coating solution containing an adhesive, pigment and lubricant containing Veova acrylic resin, applying this overcoat coating solution on the thermal recording layer, and drying. The The coating amount of the overcoat layer is, for example, 0.5 to 5 g / m ² , preferably 1 to 3 g / m ² in terms of dry mass.

  An antifoaming agent and a dispersing agent may be appropriately added to each coating liquid for forming the heat-sensitive recording material according to the present invention.

  The heat-sensitive recording material according to the present invention thus obtained is obtained by immersing the heat-sensitive recording material in tap water for 5 seconds and then bringing the heat-sensitive recording layer-side surfaces into contact with each other and drying at room temperature. The surfaces are not bonded to each other, and the heat-sensitive recording layer is not peeled off.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an Example and a comparative example show a mass part and mass%, respectively.
Example 1

表１の組成物を混合しアンダーコート用塗液を調製した。この液を乾燥後の塗布量が６ｇ／ｍ^２となるように上質紙に塗布・乾燥しアンダーコート層を形成した。 (1) Formation of undercoat layer

The composition of Table 1 was mixed to prepare an undercoat coating solution. This liquid was applied and dried on fine paper so that the coating amount after drying was 6 g / m ² to form an undercoat layer.

表２の組成物をサンドグラインダーで平均粒子径が１μｍとなるまで粉砕した。 (2) Solution A preparation

The composition of Table 2 was pulverized with a sand grinder until the average particle size became 1 μm.

表３の組成物をサンドグラインダーで平均粒子径が１μｍとなるまで粉砕した。 (3) Solution B preparation

The composition of Table 3 was pulverized with a sand grinder until the average particle size became 1 μm.

表４の組成物を混合、攪拌し、塗液とした。得られた塗液を上記アンダーコート層上に乾燥質量が６ｇ／ｍ^２となるように塗布、乾燥して感熱記録層を得た。 (4) Formation of thermosensitive recording layer

The compositions in Table 4 were mixed and stirred to obtain a coating solution. The obtained coating liquid was applied on the undercoat layer so as to have a dry mass of 6 g / m ² and dried to obtain a thermosensitive recording layer.

表５の組成物を上記感熱記録層の上に乾燥質量が２．０ｇ／ｍ^２となるように塗布、乾燥して感熱記録紙を得た。 (5) Formation of overcoat layer

The composition shown in Table 5 was applied on the heat-sensitive recording layer so that the dry mass was 2.0 g / m ² and dried to obtain a heat-sensitive recording paper.

In the formulations shown in Tables 1 to 5, for calcined clay, polyvinyl alcohol, calcium carbonate, and aluminum hydroxide, after adjusting each obtained raw material to an aqueous solution or dispersion of a predetermined concentration, the mass of the aqueous solution or dispersion Was added to each composition as a reference. For a 40% aqueous solution of sodium polyacrylate, a 30% paraffin wax solution, a 30% zinc stearate solution and a 50% solution of Veova acrylic resin, the raw materials in solution are obtained and the respective compositions are based on the mass of those solutions as they are. Added to .

(Reference Example 2)
Instead of 11 parts of the overcoat layer of veobaacrylic resin in Example 1, 7 parts of veobaacrylic resin and 20 parts of a 10% aqueous solution of polyvinyl alcohol were mixed. Otherwise, a thermal recording paper was obtained in the same manner as in Example 1 .

(Reference Example 3)
Instead of using 11 parts of the overcoat layer of veobaacrylic resin in Example 1, 5.5 parts of veobaacrylic resin and 27.5 parts of a 10% aqueous solution of polyvinyl alcohol were mixed. Otherwise, a thermal recording paper was obtained in the same manner as in Example 1 .

(Comparative Example 1)
Instead of using 11 parts of the veobaacrylic resin in the overcoat layer in Example 1, 55 parts of a 10% aqueous solution of polyvinyl alcohol was mixed without mixing the veobaacrylic resin. Otherwise, a thermal recording paper was obtained in the same manner as in Example 1 .

(Comparative Example 2)
Instead of using 11 parts of the overcoat layer of veobaacrylic resin in Example 1, 3.7 parts of veobaacrylic resin was used, and 36.5 parts of a 10% aqueous solution of polyvinyl alcohol was mixed. Otherwise, a thermal recording paper was obtained in the same manner as in Example 1.

  The heat-sensitive recording paper thus obtained is developed with a heat-sensitive color former [trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.] with an applied energy of 0.40 mj / dot.

  After immersing each colored thermal recording paper in tap water for 5 seconds, (A) contacting the colored thermal surfaces or (B) contacting the colored thermal surface and the uncolored thermal surface, (1) Adhesiveness is comprehensively determined for each of those peeled off after 1 minute and (2) those peeled off after drying at room temperature. The case where the heat-sensitive recording layer was adhered and peeled off was evaluated as x, the case where the heat-sensitive recording layer was not peeled off was evaluated as Δ, and the case where the heat-sensitive recording layer was not bonded and peeled off was evaluated as ○.

Table 6 shows the results of water-resistant adhesion.

  From the results shown in Table 6, the heat-sensitive recording paper obtained in each example was an extremely excellent heat-sensitive recording paper that did not adhere even if water was attached to the heat-sensitive surface, as compared with the comparative example.

In Example 1, the content of the veobaacrylic resin is 100% by mass of the total resin amount contained in the overcoat layer, 64% by mass in Reference Example 2, and 50% by mass in Reference Example 3. On the other hand, in Comparative Example 1, the content of the veobaacrylic resin is 0% by mass of the total resin amount contained in the overcoat layer, and in Comparative Example 2, it is 34% by mass. It can be seen that by setting the content of the veobaacrylic resin to 100% by mass of the total resin content in the overcoat layer, a heat-sensitive recording paper that does not adhere even if water is attached to the heat-sensitive surface is obtained.

Claims (4)

A thermal recording layer comprising at least a leuco dye and a developer that develops a color when the leuco dye is heated on a support, and a thermal recording body provided with an overcoat layer on the thermal recording layer. layer, heat-sensitive recording material, characterized by containing only Beobaakuriru resin as a resin component serving as an adhesive.   After dipping the heat-sensitive recording material in tap water for 5 seconds, when the surfaces on the heat-sensitive recording layer side are brought into contact with each other and dried at room temperature, the surfaces do not adhere to each other and the heat-sensitive recording layer does not peel off. The heat-sensitive recording material according to claim 1. Wherein on the support, as the lower layer of the thermosensitive recording layer The heat-sensitive recording material according to claim 1 or 2, characterized by providing an undercoat layer. The heat-sensitive recording material according to claim 1, wherein the overcoat layer does not contain a water-proofing agent.