Heat-sensitive recording medium

Abstract

Disclosed is a heat-sensitive recording medium comprising: a base paper; a resin layer located on at least one surface of the base paper from the side close to the base paper; and a heat-sensitive recording layer containing a leuco dye and a developer, the heat-sensitive recording material having a HAZE value of 80% or less as measured in accordance with JIS K7136, and the resin layer being formed by laminating by a melt extrusion method or by bonding the base paper and the resin layer using an adhesive.

Description

Technical Field

[0001] The present invention relates to a thermosensitive recording medium that utilizes a color development reaction between a leuco dye and a developer. Background Art

[0002] Thermosensitive recording media that utilize a color development reaction between a leuco dye and a developer are inexpensive, the recording devices are small, and their maintenance is easy. Therefore, they are widely used not only as recording media for facsimiles, various computers, CAD plotters, etc., but also for food uses such as fresh food, bento boxes, home-cooked meals, etc., medical uses such as labels for drug management, and labels for engineering management purposes.

[0003] In food uses, when used as labels, top-sealing materials, tapes, etc. in transparent containers containing salads, side dishes, etc., a medium with high transparency is required so that the contents can be seen well in many cases. At this time, a transparent thermosensitive film with a transparent PET film rather than a paper substrate is usually used.

[0004] According to the recent desire to reduce the environmental load, for the purpose of reducing the use of plastics, in some display labels, etc., there is also a trend to return from a PET film substrate to a paper substrate, etc., but the demand for improving the visibility of the contents due to high transparency is still high.

[0005] As such a thermosensitive recording medium, Patent Document 1 reports a thermosensitive recording paper characterized in that an organic solvent coating solution in which a resin is dissolved is coated on one or both sides of cellophane and dried, and a thermosensitive recording layer containing a leuco dye and a color former is provided on at least one surface, and the organic solvent coating solution contains 3 to 35% by weight of a pigment based on the total solid content of the resin.

[0006] In addition, Patent Document 2 discloses, regarding a recording material having a recording layer provided on a support, that the support is a support in which a plastic film layer is provided on at least the surface of the base paper on which the recording layer is provided by a melt extrusion method.

[0007] Furthermore, Patent Document 3 reports a gas barrier laminate formed by laminating a resin layer and a paper substrate layer, wherein the paper substrate layer has a paper substrate, and the basis weight of the paper substrate is 20 g / m 2 above and 40 g / m 2Hereinafter, the total light transmittance of the base paper is 70% or more, and the ratio of the mass per unit area of the resin layer to the mass per unit area of the base paper layer (resin layer / base paper layer) is 1.00 or less. The gas barrier laminate includes a heat-sealing layer containing a heat-sealing agent, a resin layer, and a base paper layer laminated in this order. The resin constituting the resin layer is at least one selected from the group consisting of polyolefin resins, polyester resins, polyamide resins, and biodegradable resins. The gas barrier laminate is formed by laminating the base paper layer and the resin layer by extrusion lamination or by bonding the base paper layer and the resin layer with an adhesive.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: Japanese Patent Laid-Open No. 8-142509

[0011] Patent Document 2: Japanese Patent Laid-Open No. 10-010675

[0012] Patent Document 3: Japanese Patent No. 7095792 Summary of the Invention

[0013] Problems to be Solved by the Invention

[0014] In order to reduce the environmental load and reduce the amount of plastics used, the object of the present invention is to provide a thermal recording body with high transparency using a base paper.

[0015] Solutions to the Problems

[0016] The present inventors have found that by using glassine paper with high transparency in the base paper, forming a resin layer on at least one surface of the glassine paper by melt extrusion, or forming a resin layer by bonding the base paper and the resin layer with an adhesive, and sequentially providing a thermal recording layer and a protective layer on the resin layer, the above problems can be solved, and thus the present invention has been completed. That is, the present invention relates to the following thermal recording body.

[0017] Item 1. A thermal recording body having: a base paper; a resin layer on at least one surface of the base paper starting from the side close to the base paper; and a thermal recording layer containing a leuco dye and a developer,

[0018] The HAZE value of the thermal recording body measured according to JIS K7136 is 80% or less,

[0019] The resin layer is formed by melt extrusion lamination or by bonding the base paper and the resin layer with an adhesive.

[0020] Item 2. The thermosensitive recording body according to Item 1, which has a protective layer mainly containing an adhesive on the thermosensitive recording layer on the side opposite to the resin layer.

[0021] Item 3. The thermosensitive recording body according to Item 1 or 2, having an oxygen permeability at 23 °C and 50% RH measured by JIS K7126 of 10 mL / (m 2 ·24 h·atm) or less.

[0022] Item 4. The thermosensitive recording body according to any one of Items 1 to 3, having a water vapor transmission rate at 40 °C and 90% RH measured by JIS Z 0208 of 50 g / (m 2 ·24 h) or less.

[0023] Item 5. The thermosensitive recording body according to any one of Items 1 to 4, wherein the base paper is glassine paper and has a basis weight of 50 g / m 2 or less.

[0024] Item 6. The thermosensitive recording body according to any one of Items 1 to 5, wherein the resin constituting the resin layer is at least one selected from the group consisting of a polyethylene resin, a polypropylene resin, a polystyrene resin, a polyethylene terephthalate resin, and a biodegradable resin.

[0025] Item 7. The thermosensitive recording body according to Item 6 above, wherein the biodegradable resin is at least one selected from the group consisting of polylactic acid (PLA), polybutylene succinate (PBS), polybutylene adipate succinate (PBSA), and 3-hydroxybutyric acid / 3-hydroxyhexanoic acid copolymer (PHBH).

[0026] Item 8. The thermosensitive recording body according to any one of Items 1 to 7, wherein a resin layer is provided on the base paper on the side opposite to the thermosensitive recording layer.

[0027] Item 9. The thermosensitive recording body according to any one of Items 1 to 8, wherein the basis weight of the resin layer is 10 g / m 2 or more.

[0028] Item 10. The thermosensitive recording body according to any one of Items 1 to 9, wherein the total basis weight of the layers other than the base paper is equal to or less than the basis weight of the base paper.

[0029] Item 11. The thermosensitive recording body according to any one of Items 1 to 10, wherein the color former contains at least one selected from the group consisting of 1,1-bis(4-hydroxyphenyl)-1-phenylethane, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, 5-(N-3-methylphenylsulfonamido)-(N',N''-bis-(3-methylphenyl)-isophthalamide), 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, and N,N'-di[3-(p-toluenesulfonyloxy)phenyl]urea.

[0030] Item 12. The thermosensitive recording body according to any one of Items 1 to 11, wherein the thermosensitive recording layer contains an adhesive having an SP (solubility parameter) value of 7.5 to 9.5 (cal / cm 3 ) 0.5 thereof.

[0031] Item 13. The thermosensitive recording body according to any one of Items 2 to 12, wherein the content ratio of the adhesive in the protective layer is 80% by mass or more of the total solid content.

[0032] Item 14. The thermosensitive recording body according to any one of Items 1 to 13, wherein a thermosensitive recording layer is partially provided on the resin layer.

[0033] Item 15. The thermosensitive recording body according to any one of Items 1 to 14, further having a printing layer.

[0034] Item 16. An image recording method, wherein the image recording method performs image recording by irradiating a laser beam on the thermosensitive recording body according to any one of Items 1 to 15.

[0035] Effects of the Invention

[0036] The thermosensitive recording body of the present invention uses a paper substrate that can reduce the environmental load and reduce the amount of plastic used, and has high transparency. In addition, the thermosensitive recording layer also has excellent adhesion to the base paper, gas barrier property, light resistance, and heat resistance. Detailed Embodiments

[0037] In this specification, the expression "comprising..." includes concepts having the meanings of "containing...", "substantially consisting only of...", and "consisting only of...".

[0038] In this specification, the numerical range indicated by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0039] The latex in the present invention includes: a state of a gel or a dried coating film formed by drying the dispersion medium.

[0040] The thermosensitive recording body of the present invention is characterized by having: a base paper; a resin layer located on at least one surface of the aforementioned base paper starting from the side closer to the base paper; and a thermosensitive recording layer containing a leuco dye and a developer, wherein the HAZE value of the thermosensitive recording body measured according to JIS K7136 is 80% or less.

[0041] The aforementioned resin layer is laminated by the melt extrusion method or the base paper and the resin layer are adhered together using an adhesive.

[0042] In the present invention, gas barrier property refers to the barrier property mainly against oxygen and water vapor, and may also have a barrier property against other gases.

[0043] In addition, the base paper is formed of a paper substrate, and the base paper and the paper substrate are sometimes used interchangeably.

[0044] [Base paper]

[0045] The base paper in the present invention is formed of a paper substrate.

[0046] Regarding the basis weight of the base paper, from the viewpoints of ease of manufacture and processing, strength and dimensional stability, and gas barrier property, it is preferably 20 g / m 2 or more, more preferably 25 g / m 2 or more, further preferably 28 g / m 2 or more, and preferably 50 g / m 2 or less, more preferably 40 g / m 2 or less, further preferably 36 g / m 2 or less, particularly preferably 32 g / m 2 or less. It should be noted that the basis weight of the base paper is measured according to JIS P 8124:2011.

[0047] In addition, regarding the thickness of the base paper, from the viewpoints of ease of manufacture and processing, strength and dimensional stability, and gas barrier property, it is preferably 15 μm or more, more preferably 20 μm or more, further preferably 25 μm or more, still further preferably 28 μm or more, and preferably 50 μm or less, more preferably 45 μm or less, further preferably 40 μm or less, still further preferably 35 μm or less.

[0048] Regarding the density (also known as bulk density) of the base paper, from the viewpoints of gas barrier property and ease of manufacture, it is preferably 0.80 g / cm 3 or more, more preferably 0.90 g / cm 3 or more, further preferably 0.95 g / cm 3 or more, and preferably 1.40 g / cm 3Hereinafter, more preferably 1.30 g / cm 3 Hereinafter, further preferably 1.20 g / cm 3 Hereinafter. The density of the base paper is calculated from the basis weight per unit area and the thickness of the base paper obtained by the above-described measurement method.

[0049] Regarding the total light transmittance of the base paper, from the viewpoint of obtaining excellent gas barrier properties, it is 70% or more, preferably 75% or more, more preferably 80% or more, and may be 100%. From the viewpoint of ease of acquisition, it is preferably 95% or less, more preferably 90% or less. The total light transmittance of the base paper is measured in accordance with JIS K7375:2008.

[0050] Regarding the base paper in the present invention, from the viewpoint of improving transparency, the nonstandard freeness of the pulp constituting the base paper is preferably 100 mL or more and 600 mL or less. Here, the nonstandard freeness means the freeness (drainage degree) measured by changing the pulp collection amount from 3 g to 0.3 g and changing the JIS standard sieve plate to an 80-mesh sieve in the Canadian standard freeness method specified in JISP 8121:2012. If the nonstandard freeness of the pulp constituting the base paper is at least the above lower limit value, the dimensional stability of the base paper becomes high and undulations are less likely to occur. If it is at most the above upper limit value, the transparency of the base paper can be maintained, which is preferable. The nonstandard freeness of the pulp fibers constituting the base paper is more preferably 150 mL or more and 500 mL or less, and further preferably 200 mL or more and 400 mL or less. In order to adjust the nonstandard freeness, a known method can be used for the method of beating the pulp. The nonstandard freeness of the pulp constituting the base paper can be measured according to the above method using the pulp obtained by dissociating in accordance with JIS P 8220-1:2012 as a sample.

[0051] Regarding the air permeability of the base paper, from the viewpoint of improving gas barrier properties, it is preferably 30,000 seconds or more, more preferably 50,000 seconds or more, and further preferably 99,999 seconds or more. The air permeability of the base paper is a value measured in accordance with JIS P 8117:2009 using the Wang's method.

[0052] As the base paper, there are no particular limitations on the type, shape, size, etc., and glassine paper is preferred. It should be noted that among glassine papers, glassine paper showing a high total light transmittance with high beating is also called Gurafan paper, and Gurafan paper is more preferably used. Usually, glassine paper is obtained as follows: As a pulp raw material, softwood chemical pulp is used as a main component, high beating is performed, papermaking is carried out under acidic to neutral conditions, and compression treatment and finishing are performed using a supercalender or the like.

[0053] As a specific example of the pulp, for example, chemical pulp formed from coniferous woods such as spruce and hemlock is optimal. However, in addition to this, chemical pulp, mechanical pulp, waste paper, synthetic pulp, etc. formed from broad-leaved woods can also be mixed and blended.

[0054] [Resin layer]

[0055] As the resin layer in the present invention, a single-layer film composed of a single resin, a single-layer or laminated film using multiple resins, etc. can be cited. In addition, a laminated resin layer in which the above resin is laminated on other substrates (metal, wood, paper, ceramic, etc.) can also be used.

[0056] As the resin constituting the resin layer, preferred examples include polyolefin resins (especially polyethylene, polypropylene, etc.), polystyrene resins, polyester resins (especially polyethylene terephthalate resin), polyamide resins (especially nylon), biodegradable resins, etc.

[0057] Regarding the resin constituting the resin layer, from the viewpoint of excellent water vapor barrier properties, polyolefin resins are preferred, polyethylene and polypropylene are further preferred, and polypropylene is more preferred.

[0058] It should be noted that the polyethylene can be low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), or high-density polyethylene (HDPE).

[0059] In addition, the resin layer can be unstretched, or can be uniaxially or biaxially stretched.

[0060] In addition, from the viewpoint of reducing the environmental load, the resin constituting the resin layer is also preferably a biodegradable resin. As the biodegradable resin, for example, polylactic acid (PLA), polybutylene succinate (PBS), polybutylene adipate-co-butylene succinate (PBSA), 3-hydroxybutyric acid / 3-hydroxyhexanoic acid copolymer (PHBH), etc. can be cited.

[0061] The thermosensitive recording body of the present invention can also have a resin layer as a heat-sealing layer on the base paper on the side opposite to the thermosensitive recording layer.

[0062] Regarding the ratio of the unit area mass of the resin layer to the unit area mass of the base paper (resin layer / base paper), from the viewpoints of obtaining appropriate strength (rigidity) as a thermosensitive recording body, water vapor barrier properties, and ease of manufacture, it is preferably 0.50 or more, more preferably 0.60 or more, and further preferably 0.70 or more.

[0063] The unit area mass of the resin layer is not particularly limited, and is preferably 5 g / m 2 or more, more preferably 10 g / m2 More preferably, it is 15 g / m or more 2 Even more preferably, it is 20 g / m or more 2 Moreover, it is preferably 30 g / m or more 2 Less than. The basis weight of the resin layer is measured according to JIS P 8124:2011. When there is also a resin layer on the base paper on the side opposite to the thermal recording layer, the basis weight here refers to the total basis weight of each resin layer.

[0064] Regarding the thickness of the resin layer, from the viewpoints of the density of the resin constituting the resin layer, obtaining an appropriate strength (rigidity) of the thermal recording medium, water vapor barrier property, and ease of forming the resin layer, it is preferably 10 μm or more, more preferably 15 μm or more, even more preferably 18 μm or more, and moreover, preferably 30 μm or less. The thickness of the resin layer is measured according to JIS P 8118:2014. When there is also a resin layer on the base paper on the side opposite to the thermal recording layer, the thickness here refers to the total thickness of each resin layer.

[0065] Regarding the density of the resin layer, from the viewpoints of obtaining an appropriate strength (rigidity), water vapor barrier property, and ease of obtaining, it is preferably 0.70 g / cm³ or more 3 More preferably, it is 0.80 g / cm³ or more 3 Even more preferably, it is 0.85 g / cm³ or more 3 Even further preferably, it is 0.90 g / cm³ or more 3 Moreover, it is preferably 1.80 g / cm³ or more 3 Less than, more preferably 1.50 g / cm³ or less 3 Less than, even more preferably 1.30 g / cm³ or less 3 Less than. The density of the resin layer is calculated from the basis weight and thickness of the resin layer obtained according to the above measurement method.

[0066] The resin layer may also contain additives such as fillers, anti-blocking agents, antistatic agents, plasticizers, plasticizers, oxidants, etc. These additives can be used alone or in combination of two or more.

[0067] The resin layer can be formed by extruding and laminating the resin on the base paper. Alternatively, the base paper can be adhered to the resin layer (such as a resin film, etc.) using an adhesive.

[0068] When using an adhesive for adhesion, the adhesive used is not particularly limited and can be a solventless type, an organic solvent type, an aqueous type, etc., but from the viewpoint of ensuring the shape stability of the base paper, it is preferably an organic solvent type adhesive or a solventless type adhesive.

[0069] As the main components constituting the adhesive, examples include (meth)acrylate copolymers, α-olefin copolymers, ethylene-vinyl acetate copolymers, polyvinyl alcohol, polyurethanes, styrene-butadiene copolymers, polyvinyl chloride, epoxy resins, melamine resins, silicone resins, natural rubbers, casein, starches, etc. Among these, from the viewpoints of easy availability and good adhesiveness, (meth)acrylate copolymers and ethylene-vinyl acetate copolymers are preferred, and ethylene-vinyl acetate copolymers are more preferred.

[0070] It should be noted that after applying the adhesive on the resin layer, the resin layer and the base paper can be laminated, or after applying the adhesive on the base paper, the base paper and the resin layer can be laminated. Additionally, after applying the adhesive on both the resin layer and the base paper, the resin and the base paper can be laminated, without particular limitation. From the viewpoint of shape stability, it is preferred to laminate the base paper after applying the adhesive on the resin layer.

[0071] As the coating method of the adhesive, it can be appropriately selected from conventionally well-known methods without particular limitation, and examples include roll coaters, die coaters, sprayers, etc.

[0072] The amount of the adhesive applied is not particularly limited. For the applied amount (coating amount) after drying, from the viewpoint of improving the adhesion between the resin layer and the base paper, it is preferably 1 g / m 2 or more, more preferably 2 g / m 2 or more, further preferably 4 g / m 2 or more, and moreover, it is preferably 40 g / m 2 or less, more preferably 20 g / m 2 or less, further preferably 10 g / m 2 or less.

[0073] [Thermosensitive recording layer]

[0074] In the thermosensitive recording layer of the thermosensitive recording body of the present invention, various conventionally well-known leuco dyes that are colorless or light-colored can be contained. Specific examples of such leuco dyes are given below.

[0075] As specific examples of leuco dyes, for example, the following can be cited: 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylamino-2-methylphenyl)-3-(4-dimethylaminophenyl)-6-dimethylaminophthalide, blue color-developing dyes such as fluoran, 3-(N-ethyl-N-p-tolyl)amino-7-N-methylanilinofluoran, 3-diethylamino-7-anilinofluoran, 3-diethylamino-7-dibenzylaminofluoran, green color-developing dyes such as rhodamine B-anilide, 3,6-bis(diethylamino)fluoran-γ-anilide, 3-cyclohexylamino-6-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7-chlorofluoran and other red color-developing dyes, 3-(N-ethyl-N-isopentyl)amino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-cyclohexyl)amino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di(n-butyl)amino-6-methyl-7-anilinofluoran, 3-di(n-pentyl)amino-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isopentylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-7-(m-trifluoromethylanilino)fluoran, 3-(N-isopentyl-N-ethylamino)-7-(o-chloroanilino)fluoran, 3-(N-ethyl-N-2-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran, 3-(N-n-hexyl-N-ethylamino)-6-methyl-7-anilinofluoran, 3-[N-(3-ethoxypropyl)-N-ethylamino]-6-methyl-7-anilinofluoran, 3-[N-(3-ethoxypropyl)-N-methylamino]-6-methyl-7-anilinofluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-di(n-butylamino)-7-(2-chloroanilino)fluoran, 4,4'-bis-dimethylaminobenzyl alcohol benzyl ether, N-2,4,5-trichlorophenyl leucoauramine, 3-diethylamino-7-butylaminofluoran, 3-ethyl-toluidino-6-methyl-7-anilinofluoran, 3-cyclohexyl-methylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-(β-ethoxyethyl)aminofluoran, 3-diethylamino-6-chloro-7-(γ-chloropropyl)aminofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N-isopentyl-N-ethylamino)-6-methyl-7-anilinofluoran, 3-dibutylamino-7-chloroanilinofluoran, 3-diethylamino-7-(o-chlorophenylamino)fluoran, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-p-toluidino)-6-methyl-7-(p-toluidino)fluoran, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-dimethylamino-6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 2,2-bis{4-[6'-(N-cyclohexyl-N-methylamino)-3'-methylspiro[tetrachlorophthalide-3,9'-xanthene]-2'-ylamino]phenyl}propane, 3-diethylamino-7-(3'-trifluoromethylphenyl)aminofluoran and other black color-developing dyes, 3,3-bis[1-(4-methoxyphenyl)-1-(4-dimethylaminophenyl)ethen-2-yl]-4,5,6,7-tetrachlorophthalide, 3,3-bis[1-(4-methoxyphenyl)-1-(4-pyrrolidinophenyl)ethen-2-yl]-4,5,6,7-tetrachlorophthalide, 3-p-(p-dimethylaminoanilino)anilino-6-methyl-7-chlorofluoran, 3-p-(p-chloroanilino)anilino-6-methyl-7-chlorofluoran, 3,6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)tetrachlorophthalide and other dyes having an absorption wavelength in the near-infrared region, etc. Of course, it is not limited to these, and two or more compounds can be used in combination as needed.,

[0076] The content ratio of the above-mentioned leuco dye is not particularly limited, and it is preferably about 3 to 30% by mass, more preferably about 5 to 25% by mass, and further preferably about 7 to 25% by mass in the total solid content of the thermosensitive recording layer. By setting it to 3% by mass or more, the color-developing ability can be improved and the printing density can be improved. By setting it to 30% by mass or less, the heat resistance can be improved.,

[0077] As specific examples of the color former, for example, the following can be cited: phenolic compounds such as 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-dihydroxydiphenylmethane, 4,4'-isopropylidenediphenol, 4,4'-cyclohexylidenebiphenyl, 4,4'-cyclohexylidenediphenol, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 4,4'-bis(p-toluenesulfonylaminocarbonylamino)diphenylmethane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2'-bis[4-(4-hydroxyphenyl)phenoxy]diethyl ether, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thio-bis(3-methyl-6-tert-butylphenol), 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-n-propoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, 4-hydroxy-4'-benzyloxydiphenyl sulfone, 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone, butyl bis(p-hydroxyphenyl)acetate, methyl bis(p-hydroxyphenyl)acetate, hydroquinone monobenzyl ether, bis(3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-allyloxy-4'-hydroxydiphenyl sulfone, 3,4-dihydroxyphenyl-4'-methylphenyl sulfone, 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, sec-butyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, 4,4'-dihydroxydiphenyl ether; or aromatic carboxylic acids such as benzoic acid, p-chlorobenzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-butylsalicylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3-(α-methylbenzyl)salicylic acid, 3,5-ditert-butylsalicylic acid, 4-[2-(p-methoxyphenoxy)ethoxy]salicylic acid, 4-[3-(p-toluenesulfonyl)propoxy]salicylic acid, 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]salicylic acid, 4-[3-(p-toluenesulfonyl)propoxy]salicylic acid zinc, and their phenolic compounds; salts of aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, etc.; furthermore, organic acidic substances such as an antipyrine complex of zinc thiocyanate, a composite zinc salt of p-formylbenzoic acid and other aromatic carboxylic acids;Urea compounds such as N-p-toluenesulfonyl-N'-3-(p-toluenesulfonyloxy)phenylurea, N-p-toluenesulfonyl-N'-p-butoxycarbonylphenylurea, N-p-toluenesulfonyl-N'-phenylurea, 4,4'-bis(p-toluenesulfonylaminocarbonylamino)diphenylmethane, 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, etc.; thiourea compounds such as N,N'-di-m-chlorophenylthiourea; organic compounds having an -SO2NH- bond in the molecule such as N-(p-toluenesulfonyl)carbamic acid p-cumylphenyl ester, N-(p-toluenesulfonyl)carbamic acid p-benzyloxyphenyl ester, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, N-(o-toluoyl)-p-toluenesulfonamide, etc.; inorganic acidic substances such as activated clay, attapulgite, colloidal silica, aluminum silicate, etc.

[0078] Furthermore, examples include: 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, 4,4'-bis[(2-methyl-5-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, 4-(2-methyl-3-phenoxycarbonylaminophenyl)ureido-4'-(4-methyl-5-phenoxycarbonylaminophenyl)ureido diphenylsulfone and other urethane derivatives represented by the following general formula (1), diphenylsulfone derivatives represented by the following general formula (2), 5-(N-3-methylphenyl-sulfonamide)-(N',N''-bis-(3-methylphenyl)-isophthalamide, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, N,N'-di[3-(p-toluenesulfonyloxy)]phenylurea, etc. Of course, it is not limited to these, and two or more compounds can also be used in combination as needed.

[0079]

[0080]

[0081] (In the formula, n represents an integer from 1 to 6.)

[0082] As the color former, among these, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, 5-(N-3-methylphenyl-sulfonamide)-(N',N''-bis-(3-methylphenyl)-isophthalamide, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, N,N'-di[3-(p-toluenesulfonyloxy)]phenylurea, etc. are preferred, and 1,1-bis(4-hydroxyphenyl)-1-phenylethane, N-[2-(3-phenylureido)phenyl]benzenesulfonamide and N,N'-di[3-(p-toluenesulfonyloxy)]phenylurea are more preferred.

[0083] The content of the above-mentioned developer is not particularly limited and can be adjusted according to the leuco dye used. Generally, per 1 part by mass of the leuco dye, it is preferably 0.5 part by mass or more, more preferably 0.8 part by mass or more, further preferably 1 part by mass or more, still more preferably 1.2 part by mass or more, and particularly preferably 1.4 part by mass or more. In addition, the content of the developer per 1 part by mass of the leuco dye is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, further preferably 4 parts by mass or less, and particularly preferably 3.5 parts by mass or less. By setting it to 0.5 part by mass or more, the recording performance can be improved. On the other hand, by setting it to 10 parts by mass or less, the background fogging under high-temperature environments can be effectively suppressed.

[0084] In the present invention, in the thermosensitive recording layer, in order to further improve the storage stability of mainly the developed image, a storage stability improver can be further contained. As such a storage stability improver, for example, at least one selected from phenolic compounds such as 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1-bis(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisphenol, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisphenol; epoxy compounds such as 4-benzyloxyphenyl-4'-(2-methyl-2,3-epoxypropoxy)phenyl sulfone, 4-(2-methyl-1,2-epoxyethyl)diphenyl sulfone, 4-(2-ethyl-1,2-epoxyethyl)diphenyl sulfone; and isocyanuric acid compounds such as 1,3,5-tris(2,6-dimethylbenzyl-3-hydroxy-4-tert-butyl)isocyanuric acid can be used. Of course, it is not limited to these, and two or more compounds can also be used in combination as needed.

[0085] When using the storage stability improver, its amount can be set to an effective amount that can achieve the improved storage stability. Generally, in the total solid content of the thermosensitive recording layer, it is preferably about 1 to 30% by mass, more preferably about 5 to 20% by mass.

[0086] The thermal recording layer in the present invention may also contain a sensitizer. Thereby, the recording sensitivity can be improved. Examples of the sensitizer include: stearamide, methoxycarbonyl-N-benzoyl stearamide, N-benzoyl stearamide, N-eicosanamide, ethylene bisstearamide, behenamide, methylene bisstearamide, N-hydroxymethyl stearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, diphenyl sulfone, benzyl p-benzylhydroxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthyl benzyl ether, m-terphenyl, p-benzylbiphenyl, bis(p-chlorobenzyl) oxalate, bis(p-methylbenzyl) oxalate, dibenzyl oxalate, p-tolyldiphenyl ether, bis(4-methoxyphenoxyethyl) ether, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, 1,2-bis(4-methoxyphenoxy)ethane, 1,2-bis(4-chlorophenoxy)ethane, 1,2-diphenoxyethane, 1-(4-methoxyphenoxy)-2-(3-methylphenoxy)ethane, p-methylthiophenyl benzyl ether, 1,4-bis(phenylthio)butane, 4-methylacetanilide, p-acetophenetidine, N-acetoacetyl-p-toluidine, 1,2-bis(phenoxymethyl)benzene, bis(β-biphenylylethoxy)benzene, p-bis(vinyloxyethoxy)benzene, 1-isopropylphenyl-2-phenylethane, bis(o-chlorobenzyl) adipate, 1,2-bis(3,4-dimethylphenyl)ethane, 1,3-bis(2-naphthyloxy)propane, biphenyl, benzophenone, etc. They can be used in combination within a non-obstructive range. The content ratio of the sensitizer can be set to an effective amount that can achieve sensitization. Generally, it is preferably about 2 to 40% by mass, more preferably about 5 to 25% by mass, based on the total solid content of the thermal recording layer.

[0087] As other component materials constituting the thermal recording layer, an adhesive is used, and further, a crosslinking agent, waxes, metal soaps, water repellents, pigments, dispersants, colored dyes, fluorescent dyes, etc. can be used as needed.

[0088] As the binder used in the coating liquid for the heat-sensitive recording layer, for example, any aqueous binder such as a water-soluble binder and a water-dispersible binder can be used. As the water-soluble binder, for example, modified polyvinyl alcohols such as polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol, starch and its derivatives, methoxycellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, methylcellulose, ethylcellulose and other cellulose derivatives, sodium polyacrylate, polyvinylpyrrolidone, polyamide, diisobutene-maleic anhydride copolymer salt, styrene-acrylic copolymer salt, styrene-maleic anhydride copolymer salt, ethylene-maleic anhydride copolymer salt, acrylamide-acrylate copolymer, acrylamide-acrylate-methacrylic acid copolymer, polyacrylamide, sodium alginate, gelatin, casein, gum arabic, etc. can be cited. As the water-dispersible binder, emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer, or latexes of water-insoluble polymers such as styrene-butadiene copolymer, styrene-butadiene-acrylic copolymer, etc. can be cited. As the binder, preferably, the binder has an SP (solubility parameter) value of 7.5 to 9.5 (cal / cm 3 ) 0.5 . By using a binder having an SP within this range, the adhesion between the heat-sensitive recording layer and the resin layer can be improved. As the binder having an SP value of 7.5 to 9.5 (cal / cm 3 ) 0.5 , for example, styrene-butadiene copolymer latex, acrylic acid-modified polypropylene resin, etc. can be cited. The solubility parameter is calculated based on the solubility parameter calculation method of the Hildebrand method. The binder can be used alone or in combination of two or more. In the total solid content of the heat-sensitive recording layer, at least one of the binders is preferably compounded in a range of about 5 to 50% by mass, more preferably about 10 to 40% by mass.

[0089] A crosslinking agent that cures the adhesive of the thermosensitive recording layer or other layers may be contained in the thermosensitive recording layer. Thereby, the water resistance of the thermosensitive recording layer can be improved. Examples of the crosslinking agent include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, glyoxylates, dimethylolurea compounds, aziridine compounds, blocked isocyanate compounds; inorganic compounds such as ammonium persulfate, iron chloride, magnesium chloride, sodium tetraborate, potassium tetraborate; boric acid, boric acid triester, boron-based polymers, hydrazine compounds, glyoxylates, etc. They can be used alone or in combination of two or more. The amount of the crosslinking agent is preferably in the range of about 1 to 10 parts by mass with respect to 100 parts by mass of the total solid content of the thermosensitive recording layer. Thereby, the water resistance of the thermosensitive recording layer can be improved.

[0090] Examples of the wax include waxes such as paraffin wax, carnauba wax, microcrystalline wax, polyolefin wax, polyethylene wax; higher fatty acid amides such as stearamide, ethylene bisstearamide, higher fatty acid esters, and their derivatives, etc.

[0091] Examples of the metal soap include polyvalent metal salts of higher fatty acids such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate. In addition, within the range not impairing the effects of the present invention, various additives such as oil repellents, defoamers, and viscosity regulators may be added to the thermosensitive recording layer as needed.

[0092] The thermosensitive recording layer is usually formed as follows: Using various stirring and wet pulverizers such as ball mills, conical ball mills, grinders, vertical and horizontal sand mills, with water as the dispersion medium, the leuco dye, developer, sensitizer and preservative improver as needed are dispersed together or separately with water-soluble synthetic polymer compounds such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, methyl cellulose, styrene-maleic anhydride copolymer salt, and surfactants, and after forming a dispersion, it is dispersed so that the average particle size becomes 2 μm or less to obtain a dispersion. Using the obtained dispersion, adhesives, additives, etc. are mixed as needed to prepare a coating liquid for the thermosensitive recording layer, and after coating the prepared coating liquid for the thermosensitive recording layer, it is formed on the base paper. The coating amount of the thermosensitive recording layer is not particularly limited, and in terms of dry mass, it is preferably about 1 to 12 g / m 2 and more preferably 2 to 10 g / m 2 and further preferably 2.5 to 8 g / m 2 and particularly preferably 3 to 5.5 g / m 2 . It should be noted that the thermosensitive recording layer may be formed in two or more layers as needed, and the composition and coating amount of each layer may be the same or different.

[0093] [Protective layer]

[0094] In the thermal recording medium, a protective layer may be provided as needed on the thermal recording layer on the side opposite to the resin layer. The protective layer preferably mainly contains a binder. Further, in the protective layer, in order to prevent adhesion to the thermal head, lubricants such as polyolefin wax and zinc stearate are preferably contained, and an ultraviolet absorber and a pigment may also be contained. In addition, by providing a protective layer with gloss, the added value of the product can also be improved.

[0095] The pigment contained in the protective layer is not particularly limited. For example, amorphous silica, kaolin, clay, light calcium carbonate, heavy calcium carbonate, calcined kaolin, titanium oxide, magnesium carbonate, aluminum hydroxide, colloidal silica, synthetic phlogopite and other inorganic pigments, urea-formaldehyde resin fillers and other plastic pigments can be cited. The content ratio of the pigment is preferably about 1 to 20% by mass, more preferably about 1 to 10% by mass, and further preferably about 1 to 5% by mass in the total solid content of the protective layer.

[0096] The binder contained in the protective layer is not particularly limited, and a water-soluble or water-dispersible aqueous binder can be used. The binder can be appropriately selected from those that can be used for the thermal recording layer. Among these binders, various modified polyvinyl alcohols such as acetoacetyl-modified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, and diacetone-modified polyvinyl alcohol are more preferably used. The content ratio of the binder is preferably 80% by mass or more, preferably about 90 to 100% by mass, and more preferably about 95 to 100% by mass in the total solid content of the protective layer. By setting it to 80% by mass or more, the oxygen permeability can be suppressed and the light resistance can be improved.

[0097] The protective layer is formed, for example, as follows: After coating a protective layer coating prepared by mixing a pigment, a binder, and, if necessary, an auxiliary agent with water as a dispersion medium, it is dried to form on the thermal recording layer. The coating amount of the protective layer coating is not particularly limited, and is preferably 0.3 to 15 g / m 2 or so, more preferably 0.3 to 10 g / m 2 or so, further preferably 0.5 to 8 g / m 2 or so, particularly preferably 1 to 8 g / m 2 or so, and even more preferably 1 to 5 g / m 2 or so. It should be noted that the protective layer can be formed in two or more layers as needed, and the composition and coating amount of each layer can be the same or different.

[0098] [Printing layer]

[0099] In the present invention, a printing layer may be provided on the protective layer, between the thermosensitive recording layer and the protective layer, on the thermosensitive recording layer, between the resin layer and the thermosensitive recording layer, between the base paper and the resin layer, and on at least one of the surfaces of the base paper on the opposite side to the thermosensitive recording layer. As the printing ink used in the formation of the printing layer, if based on the classification of printing plates, there are inks for relief printing, lithography, gravure printing, stencil printing, etc. In addition, if classified based on the form of drying, penetration drying, evaporation drying, oxidative polymerization drying, photopolymerization drying (ultraviolet curing) inks, etc. can be cited. Printing methods such as flexographic printing, offset printing, gravure printing, and screen printing can be used in the formation of the printing layer. Digital printing methods such as on-demand printing and direct printing without a plate can also be used. As the color tone of the printing ink, there is no particular limitation. In particular, when no thermosensitive recording is performed on the part of the printing layer, the optical density of the printing layer is preferably lower than the optical density of the recording part of the thermosensitive recording layer. As the printed pattern, a background pattern having an optical density of about 0.1 to 0.6 or fixed information that does not overlap with thermal recording is preferred.

[0100] [Other layers]

[0101] In the present invention, it is preferred to have an adhesive layer on at least one side of the base paper. Thus, the added value of the thermosensitive recording body can be improved. As an adhesive layer, for example, by applying a coating process based on an adhesive, a rewetting adhesive, a delayed tack type adhesive, etc. to one side, adhesive paper, rewetting adhesive paper, delayed tack paper, etc. can be formed. In addition, by using the surface of the base paper on the opposite side to the thermosensitive recording layer, it is given the function of thermal transfer paper, inkjet recording paper, carbonless paper, electrostatic recording paper, electrostatic copying paper, etc., and a recording paper that can record on both sides can also be formed. Of course, two-sided thermosensitive recording bodies can also be formed. In addition, in order to suppress the penetration of oil and plasticizer from the back of the thermosensitive recording body, or for curl control, or for antistatic, a back layer can also be provided. A peeling layer containing silicone is coated on the protective layer, and an adhesive is coated on one side, thereby, a linerless label (linerless label) without peeling paper can also be formed.

[0102] [Thermosensitive recording medium]

[0103] The thermosensitive recording body can be manufactured by forming the above-mentioned layers on the resin layer of the base paper. As the method for forming the above-mentioned layers on the resin layer, any of known coating methods such as the air knife method, the doctor blade method, the gravure method, the roll coater method, the spraying method, the dipping method, the bar method, the curtain coating method, the slot die method, the slide die method, and the extrusion method can be used. In addition, each coating material can be coated and dried layer by layer to form each layer, or the same coating material can be coated in two or more layers. Furthermore, simultaneous multi-layer coating of two or more layers can also be carried out. In addition, after forming each layer or at any process after forming all the layers, a smoothing treatment can be performed by a known method such as a supercalender or a soft calender. In addition, after forming the thermosensitive recording layer (and the protective layer) on the resin layer first, the base paper can be adhered to the resin layer using an adhesive.

[0104] The lower the HAZE value of the thermosensitive recording body of the present invention, the higher the transparency, so it is preferred. The HAZE value is 80% or less, preferably 75% or less, and more preferably 70% or less. The HAZE value is measured according to JIS K7136.

[0105] The lower the oxygen transmission rate of the thermosensitive recording body of the present invention, the less oxygen will permeate, so it is preferred. The oxygen transmission rate at 23°C and 50% RH (relative humidity) is preferably 10 mL / (m 2 ·24 h·atm) or less, more preferably 5 mL / (m 2 ·24 h·atm) or less, and further preferably 2 mL / (m 2 ·24 h·atm) or less. The oxygen transmission rate of the thermosensitive recording body is measured as follows: According to JIS K7126, using an oxygen transmission rate measuring device (manufactured by MOCON, Inc., OX-TRAN2 / 20), the measurement is carried out under the above conditions.

[0106] The lower the water vapor transmission rate of the thermosensitive recording body of the present invention, the less water vapor will permeate, so it is preferred. Specifically, it is preferably 50 g / (m 2 ·24 h) or less, more preferably 30 g / (m 2 ·24 h) or less, further preferably 20 g / (m 2 ·24 h) or less, and even more preferably 10 g / (m 2 ·24 h) or less. The water vapor transmission rate is measured as follows: According to JIS Z 0208:1976, a moisture permeation cup is made with the thermosensitive recording layer on the outside to measure (Condition B: temperature 40 ± 0.5°C, relative humidity 90 ± 2%).

[0107] In the thermal recording medium of the present invention, it is preferable that the total unit area mass of the layers other than the base paper (resin layer, thermal recording layer, protective layer, etc.) is equal to or less than the unit area mass of the base paper. Thus, by making the unit area mass of the base paper greater than the total unit area mass of the other layers, the amount of plastic used can be reduced, and the environmental load can be decreased.

[0108] In the thermal recording medium of the present invention, the thermal recording layer (and protective layer) may be provided over the entire surface of the resin layer, or the thermal recording layer (and protective layer) may be provided partially on the resin layer.

[0109] The method of image recording on the thermal recording medium of the present invention is not particularly limited and may be appropriately selected according to the purpose. As the image recording method, for example, a thermal head printer, a laser beam (such as a carbon dioxide gas laser, a UV laser, a semiconductor laser beam, a YAG laser beam, a fiber laser beam, a solid laser beam, a dye laser beam, etc.) can be used. The wavelength of the laser beam when using a laser beam is not particularly limited and may be appropriately selected according to the purpose.

[0110] The thermal recording medium of the present invention has high transparency, and the thermal recording layer has excellent adhesion to the base paper, gas barrier properties, light resistance, and heat resistance. Therefore, for example, in food applications, it is suitable for use as a label, a top seal material, a tape, etc. in a transparent container containing salad, side dishes, etc. Specific Examples

[0112] The present invention will be described in further detail based on the examples, but the present invention is not limited thereto. It should be noted that unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass", respectively.

[0113] Example 1

[0114] · Preparation of Liquid A (leuco dye dispersion)

[0115] Using a sand mill, a composition containing 100 parts of 3 - bis(n - butyl)amino - 6 - methyl - 7 - anilinofluoran, 50 parts of a 20% aqueous solution of sulfone - modified polyvinyl alcohol (trade name: Gohsenex L - 3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), 10 parts of a 5% emulsion of a natural oil - based antifoaming agent (trade name: NOPCO 1407H, manufactured by SANNOPCO LIMITED), and 90 parts of water was pulverized until the median particle diameter based on a laser diffraction particle size distribution measuring device SALD2200 (manufactured by Shimadzu Corporation) became 0.5 μm to obtain Liquid A.

[0116] · Preparation of Liquid B (color former dispersion)

[0117] Using an Ultra visco mill, a composition containing 100 parts of 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 40 parts of a 20% aqueous solution of a sulfone-modified polyvinyl alcohol (trade name: Gohsenex L-3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), 1 part of a 5% emulsion of a natural oil-based antifoaming agent (trade name: NOPCO 1407H, manufactured by SANNOPCO LIMITED), and 80 parts of water was pulverized until the median particle size based on a dynamic light scattering type particle size distribution measuring device LB-500 (manufactured by Horiba, Ltd.) became 0.2 μm to obtain Liquid B.

[0118] · Preparation of Coating Liquid for Thermal Recording Layer

[0119] A composition containing 36 parts of Liquid A, 47.8 parts of Liquid B, 33.5 parts of colloidal silica (trade name: SNOWTEX N, average particle size 10 - 15 nm, manufactured by Nissan Chemical Industries, Ltd., solid content concentration 20%), 28.5 parts of a styrene-butadiene latex (trade name: SMARTEX PA9281, manufactured by Japan A&L Co., Ltd., solid content concentration 48%, SP value 8.4), 38 parts of a 10% aqueous solution of a diacetone-modified polyvinyl alcohol (trade name: DF-17, manufactured by JAPAN VAM&POVAL CO.,LTD.), 10 parts of a 10% aqueous solution of methyl cellulose (trade name: Metolose 60SH-03, manufactured by Shin-Etsu Chemical Co., Ltd.), 1 part of a polyvinyl wax emulsion (trade name: Nopcote PEM17, manufactured by SANNOPCO LIMITED, solid content concentration 40%), 6 parts of a 10% aqueous solution of dioctyl sulfosuccinate (trade name: SN WET OT-70, manufactured by SANNOPCO LIMITED), and 18 parts of water was mixed and stirred to prepare a coating liquid for the thermal recording layer.

[0120] · Preparation of Coating Liquid for Protective Layer

[0121] A composition containing 428.6 parts of a 14% aqueous solution of an acetoacetylated polyvinyl alcohol (Gohsenex Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., fully saponified, degree of polymerization 1100), 200.0 parts of an aromatic polyester-based polyurethane resin (trade name: HYDRAN AP-30F, manufactured by DIC Corporation, solid content concentration 20%), and 100.0 parts of water was mixed and stirred to prepare a coating liquid for the protective layer.

[0122] · Production of Support 1

[0123] Glassine paper (product name: Gurafan, manufactured by Oji F-Tex Co., Ltd., basis weight 35 g / m2 , with a thickness of 35 μm, a HAZE of 72%, and an unstandardized freeness of the disintegrated pulp of 250 mL), so as to have a basis weight of 12 g / m² 2 (with a thickness of 13 μm), low-density polyethylene LC607K (manufactured by Japan Polypropylene Corporation) was extrusion-laminated on the base paper to produce the support 1 of the single-sided laminate.

[0124] · Fabrication of the thermosensitive recording medium

[0125] With the dried coating amount being 4.0 g / m² 2 The coating liquid for the thermosensitive recording layer was coated on the laminated surface of the support 1 and dried to form a thermosensitive recording layer. Further, with the dried coating amount being 2.0 g / m² 2 The coating liquid for the protective layer was coated on the thermosensitive recording layer and dried to form a protective layer, obtaining the thermosensitive recording medium.

[0126] Example 2

[0127] · Fabrication of the support 2

[0128] Low-density polyethylene LC607K (manufactured by Japan Polypropylene Corporation) was extrusion-laminated on the non-laminated surface (the base paper surface) of the support 1 so as to have a basis weight of 12 g / m² 2 (with a thickness of 13 μm) to produce the support 2 of the double-sided laminate.

[0129] · Fabrication of the thermosensitive recording medium

[0130] With the dried coating amount being 4.0 g / m² 2 The coating liquid for the thermosensitive recording layer prepared in Example 1 was coated on one side of the support 2 and dried to form a thermosensitive recording layer. Further, with the dried coating amount being 2.0 g / m² 2 The coating liquid for the protective layer prepared in Example 1 was coated on the thermosensitive recording layer and dried to form a protective layer, obtaining the thermosensitive recording medium.

[0131] Example 3

[0132] · Fabrication of the support 3

[0133] Glassine paper (product name: Gurafan, manufactured by Oji F-Tex Co., Ltd., basis weight 35 g / m²) was used in the base paper 2, thickness 35 μm, HAZE 72%, non-standard freeness of disintegrated pulp 250 mL), and polypropylene resin PHA03A (manufactured by SunAllomer Ltd.) was extruded and laminated on both sides of the above-mentioned base paper at a rate of 12 g / m² on one side to produce the support 3 of the double-sided laminate. 2 (with a thickness of 13 μm) to produce the support 3 of the double-sided laminate.

[0134] · Production of the thermosensitive recording body

[0135] The coating liquid for the thermosensitive recording layer prepared in Example 1 was coated on the polypropylene laminated surface of the support 3 and dried at a dried coating amount of 4.0 g / m² to form the thermosensitive recording layer. Further, the coating liquid for the protective layer prepared in Example 1 was coated on the thermosensitive recording layer and dried at a dried coating amount of 2.0 g / m² to form the protective layer, obtaining the thermosensitive recording body. 2 to form the thermosensitive recording layer. Further, the coating liquid for the protective layer prepared in Example 1 was coated on the thermosensitive recording layer and dried at a dried coating amount of 2.0 g / m² to form the protective layer, obtaining the thermosensitive recording body. 2 to form the protective layer, obtaining the thermosensitive recording body.

[0136] Example 4

[0137] · Production of the support 4

[0138] An adhesive mixed with 10 parts of DICDRY LX-500 (manufactured by DIC Corporation) and 1 part of DICDRY KW-75 (manufactured by DIC Corporation) was coated on a transparent PET film of 12 g / m² 2 (with a thickness of 5 μm) (manufactured by FUWEI Co., Ltd., 12 μm), and then dry laminated with the non-laminated surface (the base paper surface) of the support 1 to produce the support 4. 2 (manufactured by FUWEI Co., Ltd., 12 μm), and then dry laminated with the non-laminated surface (the base paper surface) of the support 1 to produce the support 4.

[0139] · Production of the thermosensitive recording body

[0140] The coating liquid for the thermosensitive recording layer prepared in Example 1 was coated on the PET film side of the support 4 and dried at a dried coating amount of 4.0 g / m² to form the thermosensitive recording layer. Further, the coating liquid for the protective layer prepared in Example 1 was coated on the thermosensitive recording layer and dried at a dried coating amount of 2.0 g / m² to form the protective layer, obtaining the thermosensitive recording body. 2 to form the thermosensitive recording layer. Further, the coating liquid for the protective layer prepared in Example 1 was coated on the thermosensitive recording layer and dried at a dried coating amount of 2.0 g / m² to form the protective layer, obtaining the thermosensitive recording body. 2 to form the protective layer, obtaining the thermosensitive recording body.

[0141] Example 5

[0142] In the preparation of the coating liquid for the protective layer in Example 2, the amount of a 14% aqueous solution of acetoacetylated polyvinyl alcohol (Gohsenex Z-200, manufactured by Nippon Gohsei Chemical Industry Co., Ltd., fully saponified, degree of polymerization 1100) was 342.9 parts instead of 428.6 parts, the amount of an aromatic polyester-based polyurethane resin (trade name: HYDRAN AP-30F, manufactured by DIC Corporation, solid content concentration 20%) was 160.0 parts instead of 200 parts, and further 100 parts of colloidal silica (trade name: SNOWTEX O, average particle size 10 - 15 nm, manufactured by Nissan Chemical Industries, Ltd., solid content concentration 20%) was added. Except for this, a thermosensitive recording body was obtained in the same manner as in Example 2.

[0143] Example 6

[0144] In the preparation of the coating liquid for the protective layer in Example 2, the amount of a 14% aqueous solution of acetoacetylated polyvinyl alcohol (Gohsenex Z-200, manufactured by Nippon Gohsei Chemical Industry Co., Ltd., fully saponified, degree of polymerization 1100) was 278.6 parts instead of 428.6 parts, the amount of an aromatic polyester-based polyurethane resin (trade name: HYDRAN AP-30F, manufactured by DIC Corporation, solid content concentration 20%) was 130.0 parts instead of 200 parts, and further 175 parts of colloidal silica (trade name: SNOWTEX O, average particle size 10 - 15 nm, manufactured by Nissan Chemical Industries, Ltd., solid content concentration 20%) was added. Except for this, a thermosensitive recording body was obtained in the same manner as in Example 2.

[0145] Example 7

[0146] In the preparation of Liquid B in Example 2, 100 parts of N,N'-bis[3-(p-toluenesulfonyloxy)phenyl]urea was used instead of 100 parts of 1,1-bis(4-hydroxyphenyl)-1-phenylethane. Except for this, a thermosensitive recording body was obtained in the same manner as in Example 2.

[0147] Example 8

[0148] In the preparation of Liquid B in Example 2, 100 parts of N-[2-(3-phenylureido)phenyl]benzenesulfonamide was used instead of 100 parts of 1,1-bis(4-hydroxyphenyl)-1-phenylethane. Except for this, a thermosensitive recording body was obtained in the same manner as in Example 2.

[0149] Example 9

[0150] In the preparation of Liquid B of Example 2, 100 parts of 5-(N-3-methylphenyl-sulfonamide)-(N’,N”-bis-(3-methylphenyl)-isophthalamide was used to replace 100 parts of 1,1-bis(4-hydroxyphenyl)-1-phenylethane. Except for this, a thermosensitive recording medium was obtained in the same manner as in Example 2.

[0151] Example 10

[0152] In the preparation of Liquid B of Example 2, 100 parts of 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate was used to replace 100 parts of 1,1-bis(4-hydroxyphenyl)-1-phenylethane. Except for this, a thermosensitive recording medium was obtained in the same manner as in Example 2.

[0153] Example 11

[0154] In Example 4, in such a manner that the thickness of the dried coating layer was the same as the coating amount of 4.0 g / m² during full-surface coating, the coating liquid for the thermosensitive recording layer prepared in Example 1 was partially coated on the surface side of the PET film of the support 4 and dried to form a thermosensitive recording layer. Furthermore, in such a manner that the thickness of the dried coating layer was the same as the coating amount of 2.0 g / m² during full-surface coating, 2 the coating liquid for the protective layer was partially coated on the thermosensitive recording layer and dried to form a protective layer, thereby obtaining a thermosensitive recording medium. 2 In Example 4, in such a manner that the thickness of the dried coating layer was the same as the coating amount of 4.0 g / m² during full-surface coating, the coating liquid for the thermosensitive recording layer prepared in Example 1 was partially coated on the surface side of the PET film of the support 4 and dried to form a thermosensitive recording layer. Furthermore, in such a manner that the thickness of the dried coating layer was the same as the coating amount of 2.0 g / m² during full-surface coating,

[0155] Comparative Example 1

[0156] Cellophane was used in the base paper (product name: Gurafan, manufactured by Oji F-Tex Co., Ltd., basis weight 35 g / m², 2 thickness 35 μm, HAZE 72%, non-standard freeness of the disintegrated pulp 250 mL). In such a manner that the dried coating amount was 4.0 g / m², 2 the coating liquid for the thermosensitive recording layer prepared in Example 1 was coated on the surface of the base paper and dried to form a thermosensitive recording layer. Furthermore, in such a manner that the dried coating amount was 2.0 g / m², 2 the coating liquid for the protective layer prepared in Example 1 was coated on the thermosensitive recording layer and dried to form a protective layer, thereby obtaining a thermosensitive recording medium.

[0157] Comparative Example 2

[0158] · Fabrication of Support 5

[0159] Cellophane was used in the base paper (product name: Hymenu, manufactured by Oji F-Tex Co., Ltd., basis weight 75 g / m², 2, thickness 73 μm, HAZE 98%), with one side having a basis weight of 12 g / m² 2 (with a thickness of 13 μm), low-density polyethylene LC607K (manufactured by Japan Polypropylene Corporation) was extruded and laminated on both sides of the above-mentioned paper substrate to produce the support 5.

[0160] · Fabrication of the thermosensitive recording medium

[0161] With the dried coating amount being 4.0 g / m² 2 , the coating liquid for the thermosensitive recording layer was coated on one side of the support 5 and dried to form the thermosensitive recording layer. Further, with the dried coating amount being 2.0 g / m² 2 , the coating liquid for the protective layer was coated on the thermosensitive recording layer and dried to form the protective layer, obtaining the thermosensitive recording medium.

[0162] Comparative Example 3

[0163] · Preparation of the coating liquid for the resin layer

[0164] In a blender, 70 parts of a vinyl chloride-vinyl acetate copolymer (trade name: Kanebilac L-CN, weight ratio: vinyl chloride:vinyl acetate = 1:1, solid concentration 37%, manufactured by KANEKA CORPORATION) was dissolved in 80 parts of toluene.

[0165] · Fabrication of the support 6

[0166] Glassine paper (product name: Gurafan, manufactured by Oji F-Tex Co., Ltd., basis weight 35 g / m² 2 , thickness 35 μm, HAZE 72%, non-standard freeness of the disintegrated pulp 250 mL) was used as the base paper. With the dried coating amount being 4.0 g / m² 2 , the coating liquid for the resin layer was coated on the above-mentioned paper substrate and dried to produce the support 6.

[0167] · Fabrication of the thermosensitive recording medium

[0168] With the dried coating amount being 4.0 g / m² 2 , the coating liquid for the thermosensitive recording layer prepared in Example 1 was coated on one side of the support 6 and dried to form the thermosensitive recording layer. Further, with the dried coating amount being 2.0 g / m² 2 , the coating liquid for the protective layer prepared in Example 1 was coated on the thermosensitive recording layer and dried to form the protective layer, obtaining the thermosensitive recording medium.

[0169] The thermal recording media produced in the above Examples 1 to 11 and Comparative Examples 1 to 3 were subjected to the following evaluations, and the results are shown in Table 1.

[0170] [Image formation]

[0171] · Examples 1 to 11, Comparative Examples 1 to 3

[0172] Using a thermal evaluation machine (trade name: TH-TMD, manufactured by Okura Electric Co., Ltd.), for each thermal recording medium, a solid print of a 10 mm square was performed with an applied energy of 0.24 mJ / dot and a printing speed of 4 ips, to obtain a thermal recording medium print.

[0173] · Example 12

[0174] Using a UV laser marker (trade name: UV laser marker MD-U1000C, manufactured by KEYENCE CORPORATION), the thermal recording medium of Example 2 was irradiated with laser light from the thermal recording / protective layer coating surface at a wavelength of 355 nm, a power of 1.2 W, a scanning speed of 3000 mm / SEC, and a laser spot diameter of 14 μm, to perform a solid print of a 10 mm square, to obtain a thermal recording medium print.

[0175] [Transparency evaluation]

[0176] The transparency (JIS K7136) of the non-printing part of each thermal recording medium was measured using a HAZE meter (NDH-7000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0177] HAZE value exceeding 80%: When used in food containers, etc., the contents cannot be recognized

[0178] HAZE value of 80% or less: When used in food containers, etc., the contents can be recognized

[0179] [Adhesion evaluation of the coating layer to the laminated layer]

[0180] An adhesive glassine tape was adhered to the protective layer under a pressure of 100 g / cm 2 , and peeled off at a speed of 30 m / minute, and the degree of peeling of the thermal recording layer from the self-supporting body was evaluated visually according to the following criteria.

[0181] A: The thermal recording layer was not peeled off

[0182] B: Peeling was visible on the thermal recording layer

[0183] [Oxygen transmission rate]

[0184] The oxygen transmission rate of the thermosensitive recording medium is measured as follows: In accordance with JIK K7126, using an oxygen transmission rate measuring device (manufactured by MOCON, Inc., OX-TRAN2 / 20), the measurement is carried out under the conditions of 23°C and 50% RH.

[0185] Oxygen transmission rate of 2 mL / (m 2 ·24 h·atm) or less: Extremely excellent as a gas barrier material

[0186] Oxygen transmission rate exceeding 2 mL / (m 2 ·24 h·atm) and 10 mL / (m 2 ·24 h·atm) or less: Excellent as a gas barrier material

[0187] Oxygen transmission rate exceeding 10 mL / (m 2 ·24 h·atm): Cannot be used as a gas barrier material

[0188] 〔Water vapor transmission rate〕

[0189] The water vapor transmission rate of the thermosensitive recording medium is measured as follows: In accordance with JIS Z0208:1976, a moisture permeation cup is fabricated with the thermosensitive recording layer on the outside, and the measurement is carried out (Condition B: temperature 40 ± 0.5°C, relative humidity 90 ± 2%).

[0190] Water vapor transmission rate of 30 g / (m 2 ·24 h) or less: Extremely excellent as a gas barrier material

[0191] Water vapor transmission rate exceeding 30 g / (m 2 ·24 h) and 50 g / (m 2 ·24 h) or less: Excellent as a gas barrier material

[0192] Water vapor transmission rate exceeding 50 g / (m 2 ·24 h): Cannot be used as a gas barrier material

[0193] 〔Light resistance evaluation〕

[0194] Using a xenon weatherometer (manufactured by Suga Test Instruments CO., LTD.), irradiate the printed surface of each thermosensitive recording medium print for 15 hours (black panel temperature 63°C, humidity 40% RH, irradiation illuminance 390 W / m in the wavelength range of 300 - 700 nm 2 ), and then measure the recording part in the visual mode of an X-rite spectrophotometer (trade name: X-rite530, manufactured by X-rite). Then, according to the following formula, calculate the printing residue rate of the recording part.

[0195] Residual rate (%) = (Recorded concentration after treatment / Recorded concentration before treatment) × 100

[0196] Residual rate of 80% or more: Printing is very clear and excellent

[0197] Residual rate of 65% or more and less than 80%: Printing is clear and good

[0198] Residual rate less than 65%: Missing occurs during printing, etc., and it is not practical

[0199] 〔Heat resistance evaluation〕

[0200] After treating each thermal recording medium print for 1 hour in a dryer at 90°C, the non-recording part was measured in the visual mode of an X-rite spectrophotometer (trade name: X-rite530, manufactured by X-rite Corporation).

[0201] Concentration of non-recording part of 0.15 or less: Very little coloring and excellent

[0202] Concentration of non-recording part exceeding 0.15 and being 0.20 or less: Little coloring and good

[0203] Concentration of non-recording part exceeding 0.20: Strong coloring and not practical

[0204] 〔Wear resistance evaluation of thermal head〕

[0205] A 900 g load was applied to a brass ball with a diameter of 0.3175 cm, and the wear depth when the brass ball traveled 375 m on the surface of the protective layer of the thermal recording media of Examples 1 to 11 and Comparative Examples 1 to 3 was measured using a shape measuring device Profle Measurement unit VHX-S15 manufactured by KEYENCE CORPORATION. The smaller the wear depth, the better the head wear resistance can be said to be.

[0206] A: Wear depth less than 10 μm

[0207] B: Wear depth of 10 μm or more

[0208] [Table 1]

[0209]

Claims

1. A thermosensitive recording body, which has: a base paper; a resin layer located on at least one surface of the base paper starting from the side closer to the base paper; and a thermosensitive recording layer containing a leuco dye and a developer, The thermosensitive recording body has a HAZE value measured by JIS K7136 of 80% or less, The resin layer is laminated by a melt extrusion method or the base paper and the resin layer are adhered together using an adhesive.

2. The thermosensitive recording body according to claim 1, wherein, A protective layer mainly containing an adhesive is provided on the thermosensitive recording layer on the side opposite to the resin layer.

3. The thermosensitive recording body according to claim 1 or 2 has an oxygen permeability at 23°C and 50% RH measured in accordance with JIS K7126 of 10 mL / (m 2 ·24 h·atm) or less.

4. The heat-sensitive recording body according to claim 1 or 2, having a water vapor transmission rate at 40 °C and 90% RH measured in accordance with JIS Z 0208 of 50 g / (m 2 ·24 h) or less.

5. The thermosensitive recording body according to claim 1 or 2, wherein, The base paper is cellophane and has a basis weight of 50 g / m 2 or less.

6. The thermosensitive recording body according to claim 1 or 2, wherein, The resin constituting the resin layer is at least one selected from the group consisting of a polyethylene resin, a polypropylene resin, a polystyrene resin, a polyethylene terephthalate resin, and a biodegradable resin.

7. The thermosensitive recording body according to claim 6, wherein, The biodegradable resin is at least one selected from the group consisting of polylactic acid (PLA), polybutylene succinate (PBS), polybutylene adipate succinate (PBSA), and 3-hydroxybutyric acid / 3-hydroxyhexanoic acid copolymer (PHBH).

8. The thermosensitive recording body according to claim 1 or 2, wherein, A resin layer is provided on the base paper on the side opposite to the thermosensitive recording layer.

9. The thermosensitive recording body according to claim 1 or 2, wherein, The mass per unit area of the resin layer is 10 g / m 2 or more.

10. The thermosensitive recording body according to claim 1 or 2, wherein, The total unit area mass of the layers other than the base paper is less than or equal to the unit area mass of the base paper.

11. The thermosensitive recording body according to claim 1 or 2, wherein, As the developer, it contains at least one selected from the group consisting of 1,1-bis(4-hydroxyphenyl)-1-phenylethane, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, 5-(N-3-methylphenyl-sulfonamide)-(N',N''-bis-(3-methylphenyl)-isophthalamide), 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, and N,N'-di[3-(p-toluenesulfonyloxy)phenyl]urea.

12. The thermosensitive recording body according to claim 1 or 2, wherein, The thermosensitive recording layer contains an adhesive with an SP (solubility parameter) value of 7.5 to 9.5 (cal / cm 3 ) 0.5 .

13. The thermosensitive recording body according to claim 2, wherein, The content ratio of the adhesive in the protective layer is 80% by mass or more of the total solid component amount.

14. The thermosensitive recording body according to claim 1 or 2, wherein, A thermosensitive recording layer is partially provided on the resin layer.

15. The thermosensitive recording body according to claim 1 or 2, which further has a printing layer.

16. An image recording method, which performs image recording by irradiating a laser beam on the thermosensitive recording body according to claim 1 or 2.

Images