JP2006043954A - Thermal recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal recording medium which shows successful printability, scratch resistance, solvent resistance and image preservability, and establish an evaluation method enabling ink adhesion to be simply evaluated. <P>SOLUTION: This thermal recording medium is composed of a protecting layer formed on a thermal recording layer containing a colorless or pale color electron donative leuco dye and an electron acceptive developer as principal components, in that order, on a support. In addition, 0.25 mL solution regulated to the ratio of 40/40/20 = tetrabromoethane C14/cyclopentane/printing UV ink, is dripped onto the protecting layer and a lubricant is added which shows not less than 15,000 integrated number of counts as measured by an ink cure analyzer for 180 sec, 0.1 to 0.3 content ratio of the protecting layer to the total solids and not less than 1.0 ratio of particle diameter to the thickness of a coating layer of the protecting layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat-sensitive recording material excellent in printability, scratch resistance, solvent resistance and image storage stability.

Generally, a heat-sensitive recording material is usually a colorless or light-colored electron-donating leuco dye and an electron-accepting developer, which are ground and dispersed into fine particles, and then mixed together to form a binder, a filler, and a sensitizer. A coating obtained by adding an agent, a lubricant and other auxiliary agents is applied to a support such as paper, synthetic paper, film, plastic, thermal head, hot stamp, thermal pen, label, etc. Color is generated by an instantaneous chemical reaction caused by heating such as a laser beam, and a recorded image is obtained.
With the diversification of applications in recent years, thermal recording media have begun to be used in a wide range of applications such as facsimiles, computer terminal printers, automatic ticket vending machines, measuring recorders, and cash vouchers represented by car betting tickets. The thermal recording medium is used by printing variable information and the like with a thermal printer after printing common parts such as ruled lines and logos by a general printing method in advance. For this reason, there is a demand for a high level of suitability in general printing methods, as well as the stability of the blank paper portion and image stability, which are basic performances as a thermal recording medium. In particular, in printing for cash vouchers, ink adhesion in general printing is regarded as important.

Conventionally, this ink adhesion was evaluated using a sample printed by an actual printing machine. In that case, however, the printing machine itself is large-scale, and as a simple evaluation method, an RI tester is used. It was. However, in the evaluation with the RI tester, there is a case where the behavior of the printing quality differs from that of the actual printing machine depending on the physical properties (tack, viscosity) of the ink, and there is a problem that it is difficult to obtain a sufficient correlation with the actual printing machine. . This problem was particularly noticeable in inks having physical properties with low tack and low viscosity.
Recently, inks having physical properties of low tack and low viscosity have been used for printing thermal recording materials. The reason for this is that since the thermal recording material is generally composed of multiple layers, the surface strength tends to be inferior to that of a general printing substrate. This is because when printing is performed at high speed, problems such as peeling off of the coating layer occur unless the ink tack and the B-type viscosity are lowered from those of conventional inks. For this reason, a simple evaluation method of ink adhesion which shows a high correlation with an actual printer is desired.

Also, since it is handled as a cash voucher, the amount of information printed is very large, and recently, a device for holding a high-definition recorded image for the purpose of preventing forgery such as a two-dimensional bar code is required. In other words, a higher level of scratch resistance (pressure development on the white paper portion) is required in order to prevent reading errors and bar code tampering caused by accidental rubbing of the recorded image portion with nails. ing. For the purpose of eliminating such drawbacks, Patent Document 1 discloses a technique for containing a silicon-based material in a protective layer, but a silicon-based material is not preferable because it tends to deteriorate ink adhesion during printing. .
Furthermore, since the electron-donating leuco dye and the electron-accepting developer contained in the heat-sensitive recording layer are easily dissolved in various solvents, the heat-sensitive recording medium is exposed to inks such as water-based ink pens and oil-based ink pens, and adhesives. There is a problem that the color density is lowered when the white paper portion easily develops color or when a chemical such as a plasticizer adheres to the image. For the purpose of eliminating such drawbacks, Patent Document 2 discloses a technique in which a protective layer mainly composed of a pigment and a resin is provided on a thermal recording layer.
JP 2000-153669 A Japanese Patent Laid-Open No. 06-135137

  However, the heat-sensitive recording medium having the protective layer as described above has ink adhesion and surface strength at the time of printing, scratch resistance that causes color contamination of the white paper portion when rubbed during handling, solvent resistance, image storage stability, etc. Not all the quality was satisfied. Therefore, an object of the present invention is to provide a heat-sensitive recording material having good printability, scratch resistance, solvent resistance, and image storage stability. In addition, in the ink adhesion evaluation, it is difficult to obtain sufficient correlation between an RI tester, which is a simple evaluation machine that has been used conventionally, and an actual printing machine. Therefore, it is an object to establish and provide an evaluation method that can easily evaluate ink adhesion.

As a result of intensive studies, the present inventors have found a method for simply evaluating ink adhesion by a measurement method using an ink cure analyzer. Furthermore, the present inventors have found that the content ratio of the lubricant in the protective layer, the particle diameter, and the pigment particle-absorbing oil amount are important, thereby completing the present invention.
That is, the present invention relates to a heat-sensitive recording material obtained by sequentially laminating a protective layer on a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer as main components on a support. 0.25 ml of a solution prepared so that the radioactive substance (tetrabromoethane C14) / solvent (cyclopentane) / printing UV ink = 40/40/20 was dropped on the protective layer and 180 seconds using an ink cure analyzer. In addition, the present invention relates to a heat-sensitive recording material characterized in that the integrated count number (the number of atoms in which C14 is converted to C13 by β decay is measured by a radiation detector (Geiger detector)) is 15000 or more. Further, the thermal recording material contains a lubricant having a particle size of 1.0 or more with respect to the coating layer thickness of the protective layer at a ratio of 0.1 to 0.3 with respect to the solid content of the protective layer. And an integrated count number measured by the above-mentioned measuring method, which contains a pigment having an average particle size of 5 μm or less and an oil absorption of 100 ml / 100 g (JIS K5101) or less (C14 was converted to C13 by β decay) The present invention relates to a thermal recording material having a number of atoms measured by a radiation detector (Geiger detector) of 15000 or more.

  According to the present invention, it is possible to obtain a simple evaluation method for ink adhesion that is highly correlated with a thermal recording material and an actual printing press excellent in printability, scratch resistance, solvent resistance, and image storage stability.

In the present invention, 0.25 ml of a solution in which the ink adhesion of the heat-sensitive recording material is adjusted to be radioactive substance (tetrabromoethane C14) / solvent (cyclopentane) / printing UV ink = 40/40/20 is used as a protective layer. By measuring the cumulative count (measured once per second) dropped on the ink cure analyzer for 180 seconds, evaluation according to the actual printing press can be performed.
The ink cure analyzer used in the present invention is a measuring instrument for evaluating the permeability to a substrate, and a solution containing a radioactive substance (a substance containing C14), printing UV ink, and a solvent is dropped on the sample as a sample. And measure the radiation over time. When the penetration into the sample is high, the radioactive substance is captured near the surface of the substrate when the solution soaks quickly, so the decrease in the number of radiation counts over time is small. On the other hand, when the permeability to the sample is low, since the solution containing the radioactive substance volatilizes before the solution penetrates the base material, the radioactive substance captured in the vicinity of the surface of the base material decreases. For this reason, the decrease in the count of radiation with time is large. That is, as the sample has a higher solution permeability (good ink fixability), the cumulative measured value over time becomes larger.

In the present invention, 0.25 ml of a solution adjusted so as to be tetrabromoethane C14 / cyclopentane / printing UV ink = 40/40/20 is dropped on the protective layer, and the accumulated count number (measured per second) is 180 seconds. When 1 time measurement is 15000 or more, it can be evaluated as a heat-sensitive recording material having sufficient ink permeability and has good ink adhesion. Conversely, if the cumulative count (measured once per second) measured in 180 seconds is less than 15000, the ink is easily peeled off with cello tape, etc., because the ink permeability is insufficient. It becomes an upper problem.
Note that the time for measuring the integrated count is preferably at least 180 seconds. In a time shorter than 180 seconds, the count number fluctuates greatly (decrease process) regardless of the quality of the thermal recording medium. In other words, since the ink is not sufficiently in contact with the base material, the cumulative count number of time shorter than 180 seconds cannot be said to be a value representing the evaluation of the adhesion between the ink and the base material.
On the other hand, for 180 seconds, the count number has almost reached the equilibrium value, and the penetration of the adjusted solution is sufficiently stabilized (the ink is sufficiently in contact with the substrate). For this reason, it is close to the degree of penetration of the ink printed by an actual printing press (ink adhesion to the substrate), and the accumulated count of 180 seconds or more is a value representing the adhesion between the thermal recording medium and the ink. It is.

  In the present invention, as physical properties of the printing UV ink used, DIGITAL INKOMETER manufactured by Toyo Seiki Co., Ltd. (ink accumulation amount of 1 cc, roll temperature of 30 ° C., roll rotation speed of 400 rpm, coefficient of 1.00, numerical value after 1 minute of measurement start) The tack measured in step 1 is preferably 10 or less and the B-type viscosity (6 rpm, No. 4) is preferably 100,000 mPa · s or less. Evaluation of ink adhesion using ink having such physical properties was difficult to obtain a correlation between the RI tester and an actual printing machine, but it was possible to easily evaluate by using the evaluation method of the present invention.

As for the pigment used in the protective layer of the present invention, the blending ratio and physical properties greatly affect the printability such as adhesion and surface strength of printing UV ink, scratch resistance, solvent resistance, and image storage stability.
As the blending ratio of the pigment, the content ratio of the protective layer to the total solid content is preferably 0.25 or more and 0.50 or less. When the content ratio of the pigment is lower than 0.25, the printing UV ink is difficult to permeate, so that the ink adhesion is inferior, and the component that promotes fading such as a plasticizer cannot be held by the pigment, and the image storage stability is inferior. On the other hand, when the pigment content is higher than 0.50, the binder component for binding the pigment in the protective layer is insufficient and the surface strength is weak, which causes a decrease in operability in printing. In addition, bare pigment that is not protected by the binder increases on the surface of the protective layer and the coefficient of friction increases, so the scratch resistance when rubbing with a nail or the like deteriorates, or the excess pigment absorbs the solvent, so the solvent resistance Is also not preferable. The physical properties of the pigment used in the present invention are preferably an average particle diameter of 5 μm or less and an oil absorption of 100 ml / 100 g (JIS K5101) or less. When the average particle size is larger than 5 μm, the coefficient of friction on the surface of the protective layer is likely to be increased, the scratch resistance is inferior, and it is difficult to obtain smoothness, so that sensitivity and image quality are also deteriorated. Further, when the oil absorption is larger than 100 ml / 100 g (JIS K5101), the pigment absorbs an excessive amount of solvent, so that the solvent resistance is also inferior.
Further, in the present invention, a lubricant having a content ratio of 0.1 to 0.3 with respect to the total solid content of the protective layer and a ratio of the particle diameter with respect to the coating layer thickness of the protective layer being 1.0 or more is included. It is valid. When the content ratio of the lubricant is lower than 0.1, the lubricant present on the surface of the protective layer is insufficient, so that a sufficient effect of reducing the friction coefficient is not seen and satisfactory scratch resistance cannot be obtained. Moreover, when the content rate of a lubricant is higher than 0.3, since the excess lubricant absorbs a solvent, solvent resistance is also inferior, which is not preferable. Furthermore, when the ratio of the particle size of the lubricant to the coating layer thickness is less than 1.0, the lubricant is buried in the coating layer, and a sufficient friction coefficient reduction effect cannot be obtained, thereby improving the scratch resistance. It is hard to let you. Furthermore, the content ratio of the lubricant to the pigment in the protective layer is preferably 0.25 or more. When the content ratio is less than 0.25, sufficient scratch resistance cannot be obtained.

  As the binder used in the present invention, fully saponified polyvinyl alcohol having a polymerization degree of 200 to 1900, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, and others Modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer and cellulose derivatives such as ethyl cellulose, acetyl cellulose, polyvinyl chloride, polyvinyl acetate, poly Acrylamide, polyacrylic ester, polyvinyl butyllar, polystyrose and their copolymers, polyamide resin, silico Resins, petroleum resins, terpene resins, ketone resins, and the Khumalo resin. These polymer substances are used by dissolving them in solvents such as water, alcohol, ketones, esters, hydrocarbons, etc., and are used in the state of being emulsified or pasted in water or other media to achieve the required quality. It can also be used in combination.

Examples of the pigment used in the present invention include inorganic or organic fillers such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, and aluminum hydroxide. As the pigment used in the protective layer, aluminum hydroxide is preferable in consideration of the wearability of the thermal head.
Examples of the lubricant used in the present invention include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, silicone resins and the like, but in consideration of the effect of improving scratch resistance and printability, stearic acid is used. Zinc is preferred.

In the present invention, 4,4′-butylidene (6-tert-butyl-3-methylphenol) is used as an image stabilizer for imparting oil resistance and the like of a recorded image within a range that does not impair the desired effect on the above-described problems. ), 2,2'-di-t-butyl-5,5'-dimethyl-4,4'-sulfonyldiphenol, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) Butane, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenylbutane, 4-benzyloxy-4 '-(2,3-epoxy-2-methylpropoxy) diphenylsulfone, epoxy A resin or the like can also be added.
In addition, benzophenone-based or triazole-based UV absorbers, UV reflectors, water-resistant agents such as glyoxal, dispersants, antifoaming agents, antioxidants, fluorescent dyes, and the like can be used.

As the colorless to light-colored electron-donating leuco dye used in the heat-sensitive recording material of the present invention, all known ones in the field of conventional pressure-sensitive or heat-sensitive recording paper can be used, and are not particularly limited. Triphenylmethane compounds, fluorane compounds, fluorene compounds, divinyl compounds and the like are preferable. Specific examples of typical colorless or light-colored electron-donating leuco dyes are shown below. These electron donating leuco dyes may be used alone or in combination of two or more.
<Triphenylmethane leuco dye>
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone)
3,3-bis (p-dimethylaminophenyl) phthalide (also known as malachite green lactone)

<Fluoran leuco dye>
3-diethylamino-6-methylfluorane 3-diethylamino-6-methyl-7-anilinofluorane 3-diethylamino-6-methyl-7- (o, p-dimethylanilino) fluorane 3-diethylamino-6-methyl -7-chlorofluorane 3-diethylamino-6-methyl-7- (m-trifluoromethylanilino) fluorane 3-diethylamino-6-methyl-7- (o-chloroanilino) fluorane 3-diethylamino-6-methyl- 7- (p-chloroanilino) fluorane 3-diethylamino-6-methyl-7- (o-fluoroanilino) fluorane 3-diethylamino-6-methyl-7- (m-methylanilino) fluorane 3-diethylamino-6-methyl- 7-n-octylanilinofluorane 3-diethylamino- 6-methyl-7-n-octylaminofluorane 3-diethylamino-6-methyl-7-benzylaminofluorane 3-diethylamino-6-methyl-7-dibenzylaminofluorane

3-diethylamino-6-chloro-7-methylfluorane 3-diethylamino-6-chloro-7-anilinofluorane 3-diethylamino-6-chloro-7-p-methylanilinofluorane 3-diethylamino-6- Ethoxyethyl-7-anilinofluorane 3-diethylamino-7-methylfluorane 3-diethylamino-7-chlorofluorane 3-diethylamino-7- (m-trifluoromethylanilino) fluorane 3-diethylamino-7- ( o-chloroanilino) fluorane 3-diethylamino-7- (p-chloroanilino) fluorane 3-diethylamino-7- (o-fluoroanilino) fluorane 3-diethylamino-benzo [a] fluorane 3-diethylamino-benzo [c] fluorane 3 -Dibutylamino-6- Chill - fluoran

3-dibutylamino-6-methyl-7-anilinofluorane 3-dibutylamino-6-methyl-7- (o, p-dimethylanilino) fluorane 3-dibutylamino-6-methyl-7- (o- Chloroanilino) fluorane 3-dibutylamino-6-methyl-7- (p-chloroanilino) fluorane 3-dibutylamino-6-methyl-7- (o-fluoroanilino) fluorane 3-dibutylamino-6-methyl-7- (M-trifluoromethylanilino) fluorane 3-dibutylamino-6-methyl-chlorofluorane 3-dibutylamino-6-ethoxyethyl-7-anilinofluorane 3-dibutylamino-6-chloro-7-ani Linofluorane 3-dibutylamino-6-methyl-7-p-methylanilinofluorane 3-dibutylamino -7- (o-chloroanilino) fluorane 3-dibutylamino-7- (o-fluoroanilino) fluorane 3-di-n-pentylamino-6-methyl-7-anilinofluorane 3-di-n-pentyl Amino-6-methyl-7- (p-chloroanilino) fluorane 3-di-n-pentylamino-7- (m-trifluoromethylanilino) fluorane 3-di-n-pentylamino-6-chloro-7- Anilinofluorane 3-di-n-pentylamino-7- (p-chloroanilino) fluorane 3-pyrrolidino-6-methyl-7-anilinofluorane 3-piperidino-6-methyl-7-anilinofluorane

3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluorane 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane 3- (N -Ethyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane 3- (N-ethyl-N-xylamino) -6-methyl-7- (p-chloroanilino) fluorane 3- (N-ethyl- p-Toluidino) -6-methyl-7-anilinofluorane 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane 3- (N-ethyl-N-isoamylamino) -6-chloro-7-anilinofluorane 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane 3- (N-ethyl-N-isobutane) Arylamino) -6-methyl-7-anilinofluoran 3- (N- ethyl--N- ethoxypropylamino) -6-methyl-7-anilinofluoran

3-cyclohexylamino-6-chlorofluorane 2- (4-oxahexyl) -3-dimethylamino-6-methyl-7-anilinofluorane 2- (4-oxahexyl) -3-diethylamino-6-methyl -7-anilinofluorane 2- (4-oxahexyl) -3-dipropylamino-6-methyl-7-anilinofluorane 2-methyl-6-p- (p-dimethylaminophenyl) aminoanilino Fluorane 2-methoxy-6-p- (p-dimethylaminophenyl) aminoanilinofluorane 2-chloro-3-methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane 2-chloro- 6-p- (p-dimethylaminophenyl) aminoanilinofluorane 2-nitro-6-p- (p-diethylaminophenyl) amino Nirinofuruoran 2-amino -6-p- (p- diethylaminophenyl) amino anilinofluoran

2-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane 2-phenyl-6-methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane 2-benzyl-6-p -(P-phenylaminophenyl) aminoanilinofluoran 2-hydroxy-6-p- (p-phenylaminophenyl) aminoanilinofluorane 3-methyl-6-p- (p-dimethylaminophenyl) aminoani Linofluorane 3-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane 3-diethylamino-6-p- (p-dibutylaminophenyl) aminoanilinofluorane 2,4-dimethyl-6 [(4-Dimethylamino) anilino] -fluorane

<Fluorene leuco dye>
3,6,6′-tris (dimethylamino) spiro [fluorene-9,3′-phthalide]
3,6,6′-tris (diethylamino) spiro [fluorene-9,3′-phthalide]
<Divinyl leuco dye>
3,3-bis- [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrabromophthalide 3,3-bis- [2- ( p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide 3,3-bis- [1,1-bis (4-pyrrolidinophenyl) ethylene -2-yl] -4,5,6,7-tetrabromophthalide 3,3-bis- [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-yl]- 4,5,6,7-tetrachlorophthalide

<Others>
3- (4-Diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide 3- (4-diethylamino-2-ethoxyphenyl) -3- (1 -Octyl-2-methylindol-3-yl) -4-azaphthalide 3- (4-cyclohexylethylamino-2-methoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4- Azaphthalide 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide 3,6-bis (diethylamino) fluorane-γ- (3'-nitro) anilinolactam 3,6-bis (diethylamino) Fluoran-γ- (4′-nitro) anilinolactam

1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2,2-dinitrileethane 1,1-bis- [2 ′ , 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2-β-naphthoylethane 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -Tetrakis- (p-dimethylaminophenyl) -ethenyl] -2,2-diacetylethane bis- [2,2,2 ', 2'-tetrakis- (p-dimethylaminophenyl) -ethenyl] -dimethyl methylmalonate ester

  As the electron-accepting developer used in the heat-sensitive recording material of the present invention, a conventionally known electron-accepting developer that develops a colorless or light-colored electron-donating leuco dye can be used in combination. Examples of such electron-accepting color developers include inorganic acidic substances such as activated clay, attapulgite, colloidal silica, aluminum silicate, 4,4′-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane. 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4′-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4′-dihydroxydiphenyl sulfone, 2, 4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxy-4′-n-propoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4 '-Methyldiphe Sulfone, 4-hydroxyphenyl-4′-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl-4′-methylphenylsulfone, aminobenzenesulfonamide derivatives described in JP-A-8-59603, bis (4-hydroxyphenyl) Thioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, butyl bis (p-hydroxyphenyl) acetate, methyl bis (p-hydroxyphenyl) acetate, 1,1-bis (4 -Hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4′-hydroxy) Phenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, 2,2 '-Thiobis (3-tert-octylphenol), 2,2'-thiobis (4-tert-octylphenol).

  Furthermore, phenolic compounds such as diphenylsulfone cross-linking compounds described in International Publication WO 97/16420, compounds described in International Publication WO 02/081229 or JP-A No. 2002-301873, and N, N′-di-m- Thiourea compounds such as chlorophenylthiourea, p-chlorobenzoic acid, stearyl gallate, zinc bis [4- (n-octyloxycarbonylamino) salicylate] dihydrate, 4- [2- (p-methoxyphenoxy) ethyloxy ] Salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid aromatic carboxylic acids, and of these aromatic carboxylic acids Zinc, magnesium, aluminum, calcium, titanium, manga , Tin, salts of polyvalent metal salts such as nickel, more like antipyrine complex of zinc thiocyanate, etc. composite zinc salt of terephthalaldehyde acid with other aromatic carboxylic acids.

  These developers can be used alone or in combination of two or more. The diphenylsulfone cross-linking compound is available as a trade name D-90 manufactured by Nippon Soda Co., Ltd. Moreover, the compound as described in international publication WO02 / 081229 etc. is available as Nippon Soda Co., Ltd. brand name D-100. In addition, a metal chelate color-developing component such as a higher fatty acid metal double salt and a polyvalent hydroxyaromatic compound described in JP-A-10-258577 can also be contained.

  As the sensitizer used in the heat-sensitive recording material of the present invention, a conventionally known sensitizer can be used. Examples of such sensitizers include fatty acid amides such as stearamide and palmitic acid amide, ethylene bisamide, montanic acid wax, polyethylene wax, 1,2-di- (3-methylphenoxy) ethane, p-benzylbiphenyl, β- Benzyloxynaphthalene, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, dibenzyl oxalate, di (p-chlorobenzyl) oxalate, di (p-methylbenzyl) oxalate, Dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate, phenyl-α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, o-xylene-bis -(Phenyl ether), 4- (m-methyl) Ruphenoxymethyl) biphenyl, 4,4′-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, 1,2-di (3-methylphenoxy) ethylene, bis [2- (4-methoxy- Examples thereof include, but are not limited to, phenoxy) ethyl] ether, methyl p-nitrobenzoate and phenyl p-toluenesulfonate. These sensitizers may be used alone or in combination of two or more.

The types and amounts of the electron-donating leuco dye, electron-accepting developer, and other various components used in the heat-sensitive recording material of the present invention are determined according to the required performance and recording suitability, and are not particularly limited. Usually, about 0.5 to 10 parts of an electron accepting developer and about 0.5 to 10 parts of a sensitizer are used with respect to 1 part of the electron donating leuco dye.
By applying the coating liquid having the above composition to any support such as paper, recycled paper, synthetic paper, film, plastic film, foamed plastic film, non-woven fabric, etc., the desired thermal recording material can be obtained. Moreover, you may use the composite sheet which combined these as a support body.
Electron-donating leuco dye, electron-accepting developer, and materials to be added as necessary are finely divided to a particle size of several microns or less by a pulverizer such as a ball mill, an attritor, or a sand glider, or an appropriate emulsifier. Depending on the purpose, various additive materials are added to obtain a coating solution. The application means is not particularly limited, and can be applied according to well-known conventional techniques. For example, an off-machine coating equipped with various coaters such as an air knife coater, rod blade coater, vent blade coater, bevel blade coater, roll coater, etc. A machine or an on-machine coating machine is appropriately selected and used. The coating amount of the heat-sensitive recording layer is not particularly limited and is usually in the range of ² to 12 g / m ^{2 by} dry weight. Further, the coating amount of the protective layer provided on the thermosensitive recording layer is not particularly limited, and is usually in the range of 1 to 5 g / m ² .
In the heat-sensitive recording material of the present invention, an undercoat layer such as a polymer material containing a pigment can be provided under the heat-sensitive recording layer for the purpose of increasing the color development sensitivity. It is also possible to correct the curl by providing a backcoat layer on the opposite side of the support from the thermosensitive recording layer. Also, various known techniques in the heat-sensitive recording material field can be added as appropriate, such as applying a smoothing process such as supercalendering after coating each layer.

  The thermosensitive recording material of the present invention will be described below with reference to examples. In the description, parts and% represent parts by weight and% by weight, respectively. Various solutions, dispersions, or coating solutions were prepared as follows.

[Example 1]
A composition comprising the following composition was stirred and dispersed to prepare an undercoat layer coating solution.
U solution (undercoat layer coating solution)
Baked kaolin (trade name: Ensilex 90, manufactured by Engelhard)
<Oil absorption amount 90 cc / 100 g>) 100 parts Styrene / butadiene copolymer latex (solid content 48%) 40 parts Polyvinyl alcohol 10% aqueous solution 30 parts Water 146 parts Subsequently, the undercoat layer coating liquid is supported by a support (50 g / m ² The base paper was coated on one side and dried to obtain an undercoat layer coated paper with a coating amount of 10.0 g / m ² .
An electron-accepting developer dispersion (liquid A), an electron-donating leuco dye dispersion (liquid B), and a sensitizer dispersion (liquid C) having the following composition were each separately mixed with a sand grinder to obtain an average particle size of 0. Wet milled to 5 microns.
Liquid A (electron-accepting developer dispersion)
4-hydroxy-4'-isopropoxydiphenylsulfone 6.0 parts polyvinyl alcohol 10% aqueous solution 18.8 parts water 11.2 parts Liquid B (electron-donating leuco dye dispersion)
3-Dibutylamino-6-methyl-7-anilinofluorane (ODB-2)
2.0 parts polyvinyl alcohol 10% aqueous solution 4.6 parts water 2.6 parts C liquid (sensitizer dispersion)
Dibenzyl oxalate 6.0 parts Polyvinyl alcohol 10% aqueous solution 18.8 parts Water 11.2 parts

Subsequently, the dispersion liquid was mixed at the following ratio to obtain a coating liquid for the thermosensitive recording layer.
Thermosensitive recording layer coating liquid A liquid (electron accepting developer dispersion) 36.0 parts B liquid (electron donating leuco dye dispersion) 9.2 parts C liquid (sensitizer dispersion) 36.0 parts Polyvinyl 25 parts of alcohol 10% aqueous solution Next, the heat-sensitive recording layer coating solution was applied onto the undercoat layer of the undercoat layer-forming paper so as to have a coating amount of 6.0 g / m ² , followed by drying and heat-sensitive layer-coated paper. Got.
Subsequently, it mixed by the following ratio and was set as the coating liquid of the protective layer.
Aluminum hydroxide (50% dispersion, particle size 1.1 microns,
Oil absorption 36 ml / 100 g) 12.0 parts Polyvinyl alcohol 10% aqueous solution 30 parts Zinc stearate (trade name: Hydrin Z-7-30, solid content 30%,
Particle size 5.5 microns, Chukyo Yushi) 10 parts Melamine formaldehyde resin (trade name: Sumirez resin 613-s,
(Solid content: 60%, Sumitomo Chemical Co., Ltd.) 1.67 parts Next, the protective layer coating solution was applied on the heat-sensitive layer of the heat-sensitive layer coated paper so that the coating amount was 3.0 g / m ^2, and then dried. This sheet was processed with a super calendar so that the smoothness was 1000 to 2000 seconds to obtain a heat-sensitive recording material. The content ratio of aluminum hydroxide is 0.46, the content ratio of lubricant is 0.23, and the coating thickness of the protective layer is 1.5 microns.

[Example 2]
Thermal recording as in Example 1 except that the protective layer coating solution aluminum hydroxide (50% dispersion, particle size 1.1 microns, oil absorption 36 ml / 100 g) of Example 1 was changed from 12 parts to 6 parts. Created the body. The content ratio of aluminum hydroxide is 0.30, the content ratio of lubricant is 0.30, and the coating thickness of the protective layer is 1.5 microns.

[Example 3]
Implemented except that the zinc stearate (trade name: Hydrin Z-7-30, solid content 30%, particle size 5.5 microns, Chukyo Yushi) in the protective layer coating liquid of Example 1 was changed from 10 parts to 2 parts. A heat-sensitive recording material was prepared in the same manner as in Example 1. The content ratio of aluminum hydroxide is 0.57, the content ratio of lubricant is 0.06, and the coating thickness of the protective layer is 1.5 microns.

[Example 4]
Implemented except that the zinc stearate (trade name: Hydrin Z-7-30, solid content 30%, particle size 5.5 microns, Chukyo Yushi) in the protective layer coating liquid of Example 1 was changed from 10 parts to 20 parts. A heat-sensitive recording material was prepared in the same manner as in Example 1. The content ratio of aluminum hydroxide is 0.37, the content ratio of lubricant is 0.37, and the coating thickness of the protective layer is 1.5 microns.

[Example 5]
10 parts of zinc stearate (trade name: Hydrin Z-7-30, solid content 30%, particle size 5.5 microns, Chukyo Yushi) in the protective layer coating solution of Example 1 was zinc stearate (trade name: Hymicron). ZJ-557, solid content 20%, particle size 0.2 micron, Chukyo oil and fat) A heat-sensitive recording material was prepared in the same manner as in Example 1 except that it was changed to 15 parts. The content ratio of aluminum hydroxide is 0.46, the content ratio of lubricant is 0.23, and the coating thickness of the protective layer is 1.5 microns.

[Comparative Example 1]
Thermal recording as in Example 1 except that the protective layer coating solution aluminum hydroxide (50% dispersion, particle size 1.1 microns, oil absorption 36 ml / 100 g) of Example 1 was changed from 12 parts to 3 parts. Created the body. The content ratio of aluminum hydroxide is 0.18, the content ratio of lubricant is 0.35, and the coating thickness of the protective layer is 1.5 microns.

[Comparative Example 2]
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that aluminum hydroxide (50% dispersion, particle size 1.1 microns, oil absorption 36 ml / 100 g) of the protective layer coating liquid of Example 1 was not blended. The content ratio of the lubricant is 0.43, and the coating layer thickness of the protective layer is 1.5 microns.

<Recording sensitivity evaluation>
The produced thermal recording material was printed with an applied energy of 0.41 mJ / dot using a TH-PMD manufactured by Okura Electric Co., Ltd. (with a thermal recording paper printing tester and a Kyocera thermal head). The recording density of the recording part was measured and evaluated with a Macbeth densitometer (using RD-19I).
<Ink cure analyzer>
Evaluation was performed using INK CURE ANALYZER (CON TROL-CURE, INC, manufactured by Model 100 ICA) under the following conditions.
Tetrabromoethane C14 / cyclopentane / printing UV ink (tack 7.1, B-type viscosity 17250 mPa · s) = on the protective layer of the heat-sensitive recording medium prepared 0.25 ml of the solution adjusted to be 40/40/20 The total number of counts for 180 seconds (measured once per second) was measured with an ink cure analyzer.

<Ink adhesion evaluation>
(A) Immediately after printing on a heat-sensitive recording material prepared by printing UV ink (tack 7.1, B-type viscosity 17250 mPa · s) with a UV convex printing machine at a speed of 100 m / min, a Nichiban cellophane tape was applied to the printing section. After 5 seconds of pasting, the ink was peeled off and evaluated for ink adhesion to the heat-sensitive recording material.
(B) A printing UV ink (tack 7.1, B-type viscosity 17250 mPa · s) was printed on a thermal recording medium produced at a roll rotation speed of 40 rpm with an RI printer, and immediately after UV treatment, Nichiban Co., Ltd. A cellophane tape was applied and allowed to stand for 5 seconds, and then peeled off to evaluate the ink adhesion to the heat-sensitive recording material.
○: No printing UV ink peeling ×: Printing UV ink peeling <Surface strength evaluation>
The produced thermal recording material was coated with a Nichiban cellophane tape on the coated surface, allowed to stand for 5 seconds, and then peeled off to evaluate the surface strength.
○: No peeling of the coating layer Δ: Some peeling of the coating layer <Scratch resistance evaluation>
The produced thermal recording material was evaluated by scratching the blank paper portion with a nail.
◎: No color development ○: Almost no color △: Slight color development <solvent resistance>
About the produced heat-sensitive recording material, ethyl acetate was applied to a white paper portion with a cotton swab to evaluate the color development.
○: No color development △: Slight color development ×: Color development <Plasticizer resistance>
Regarding the produced thermal recording medium, a paper tube was used for a sample printed at a applied energy of 0.41 mJ / dot using a TH-PMD manufactured by Okura Electric Co., Ltd. (with thermal recording paper printing tester and Kyocera thermal head installed). Wrapped with vinyl chloride wrap (Mitsui Chemicals High Wrap KMA) once, the above sample was pasted, and a vinyl chloride wrap wrapped in three layers was allowed to stand at 40 ° C. for 24 hours. Concentration (using RD-19I) was measured.

As is apparent from Tables 1 and 2, Examples 1 to 2 of the present invention are excellent in printability represented by ink adhesion and surface strength, and excellent in scratch resistance, solvent resistance, and plasticizer resistance. Yes. In addition, in Examples 3 to 5 in which the content ratio of the lubricant to the total solid content of the protective layer and the particle size ratio to the protective layer thickness were not appropriate values, a slight deterioration in quality was observed. On the other hand, about Comparative Examples 1-2 which showed the ink cure analyzer integrated value outside the range prescribed | regulated by this invention, ink adhesiveness is bad and favorable quality is not obtained. It was also shown that ink adhesion evaluation, which was difficult with RI printing, can be easily evaluated with an ink cure analyzer.

Claims (2)

In a heat-sensitive recording material obtained by sequentially laminating a protective layer on a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer as main components on a support, tetrabromoethane C14 / Cyclopentane / printing UV ink = 40/40/20 solution adjusted to be 40/40/20 was dropped onto the protective layer, and the cumulative count measured for 180 seconds with an ink cure analyzer was 15000 or more. A characteristic thermal recording material. A lubricant having a ratio of particles to the coating layer thickness of the protective layer of 1.0 or more is contained in an amount of 0.1 to 0.3 with respect to the total solid content of the protective layer, an average particle size of 5 μm or less, and 2. The heat-sensitive recording material according to claim 1, wherein a pigment having an amount of 100 ml / 100 g (JIS K5101) or less is contained in an amount of 0.25 to 0.50 based on the total solid content of the protective layer.