JP2012076230A - Thermosensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive recording body which is excellent in color developing sensitivity, printing image quality, glossiness, water resistance, scratch resistance and plasticizer resistance.SOLUTION: The thermosensitive recording body includes an undercoat layer containing organic hollow particles, a thermosensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer, and a protection layer which are successively provided on a support. The protection layer in a wet state is pressed to a heated mirror surface drum and dried thereby. Furthermore, the protection layer has a specific structure whereby a particularly satisfactory quality can be obtained.

Description

  The present invention relates to a heat-sensitive recording material excellent in color development sensitivity, print image quality, gloss, water resistance, scratch resistance, and plasticizer resistance.

  In general, a heat-sensitive recording material is usually a colorless or light-colored electron-donating leuco dye (hereinafter also referred to as “leuco dye”) and an electron-accepting developer (hereinafter also referred to as “developer”) such as a phenolic compound. Are dispersed in fine particles, then mixed together, and a paint obtained by adding a binder, a filler, a sensitivity improver, a lubricant and other auxiliaries to paper, synthetic paper, film, It is coated on a support such as plastic, and develops color by an instantaneous chemical reaction by heating with a thermal head, hot stamp, thermal pen, laser light, etc., and a recorded image is obtained. Compared with other recording systems that have been put to practical use, this thermal recording system has no noise during recording, does not require development and fixing, is maintenance-free, is relatively inexpensive, and is compact. The developed color is very clear, and it is widely used in facsimiles, computer terminal printers, automatic ticket vending machines, measuring recorders, and so on.

  In recent years, thermal recording media have been used for various types of tickets, receipts, labels, bank ATMs, gas and electricity meter readings, and car tickets, etc. The required quality for thermal recording media Is becoming more advanced. For example, with regard to the color development sensitivity, high sensitivity capable of printing even with a small amount of energy is required as the recording apparatus becomes smaller. In addition, it is often used outdoors, and quality performance that can withstand use in harsh environments compared to conventional ones is required so that it is not difficult to read the recorded part due to moisture, moisture, solvents such as rain. ing. Furthermore, in applications such as tickets and cash vouchers, high gloss for producing a high-class feeling is preferred.

  In response to these requirements, Patent Document 1 discloses a heat-sensitive recording material that is improved in sensitivity by using a specific developer and a sensitizer in combination, and has improved storage stability by using a specific stabilizer. In Patent Document 2, acetoacetyl-modified polyvinyl alcohol is used in the heat-sensitive recording layer, and a (meth) acrylamide copolymer having a core-shell structure as a water-dispersible resin in the protective layer is contained. By including a crosslinking agent in the protective layer, the thermal recording material excellent in thermal responsiveness, water resistance, water-resistant blocking, and the like, Patent Document 3, provides an undercoat layer between the support and the thermal recording layer, A thermal recording material excellent in sensitivity, dot reproducibility, and the like has been disclosed by including organic spherical hollow particles in the undercoat layer.

JP 2005-014329 A JP 2006-198781 A JP 05-000573 A

  However, the thermal recording material of Patent Document 1 using a specific coloring material is not sufficiently effective in both coloring sensitivity and storage stability. In addition, the thermal recording materials of Patent Document 2 and Patent Document 3 have relatively good storage stability, but are not effective enough for use in applications that require particularly high quality, such as video printer paper. The color development sensitivity, print quality, and gloss obtained are not sufficient.

  Therefore, an object of the present invention is to provide a heat-sensitive recording material having sufficient color development sensitivity, print image quality, gloss, water resistance, scratch resistance, and plasticizer resistance.

  The above-mentioned problem is a thermal recording in which an undercoat layer containing organic hollow particles, a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer, and a protective layer are sequentially provided on a support. It was achieved by a thermal recording medium in which the protective layer in a wet state was pressed against a heated mirror drum and dried.

  According to the present invention, it is possible to provide a heat-sensitive recording material having sufficient color development sensitivity, print image quality, gloss, water resistance, scratch resistance, and plasticizer resistance.

  Embodiments of the present invention will be described below.

  The heat-sensitive recording material of the present invention comprises, on the support, an undercoat layer containing hollow organic particles, a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer, and a protective layer in this order. The provided heat-sensitive recording material is characterized in that the wet protective layer is pressed against a heated mirror drum and dried.

  The reason why the heat-sensitive recording material of the present invention has excellent quality is presumed as follows. There are voids in the protective layer provided by coating, which is a factor of reducing thermal conductivity (color development sensitivity), plasticizer resistance, smoothness, gloss, and the like. By pressing the wet protective layer against a heated mirror drum and drying, the voids are crushed and the entire protective layer becomes a compact state like a film. In addition, the surface property and thermal conductivity of the protective layer are improved, and matching with the printer head is improved. Due to these synergistic effects, the color development sensitivity, print image quality, plasticizer resistance, gloss and the like are improved, and the quality is greatly improved.

In the present invention, when the protective layer contains a carboxyl group-containing resin, the wet protective layer is pressed against a heated mirror drum and dried, whereby the bond between the carboxyl group-containing resin and other materials is strengthened. This is preferable because a compact protective layer is formed. Furthermore, it is preferable that the carboxyl group-containing resin is an acrylic resin because a particularly good surface can be obtained without excessively taking in moisture during the rewet treatment by the rewet cast method described later.

In the present invention, the acrylic resin contained in the protective layer includes (meth) acrylic acid and a monomer component copolymerizable with (meth) acrylic acid, and the (meth) acrylic acid is 100 wt. It is preferable that it is 1-10 weight part in a part. (Meth) acrylic acid is alkali-soluble and has the property of making an acrylic resin a water-soluble resin by the addition of a neutralizing agent. By changing the acrylic resin to a water-soluble resin, particularly when a pigment is contained in the protective layer, the binding property to the pigment is remarkably improved, and a protective layer having excellent strength even when containing a large amount of pigment is formed. be able to. Examples of components copolymerizable with (meth) acrylic acid include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, By alkyl acrylate resins such as pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, and epoxy resins, silicone resins, styrene or derivatives thereof Modified alkyl acrylate resins such as the above-mentioned alkyl acrylate resins, (meth) acrylonitrile, acrylate esters, and hydroxyalkyl acrylate esters can be exemplified, but in particular, (meth) acrylonitrile and / or methyl methacrylate is blended. Is preferred. (Meth) acrylonitrile is preferably blended in an amount of 15 to 70 parts per 100 parts of the acrylic resin. Moreover, it is preferable that methyl methacrylate contains 20-80 parts in 100 parts of acrylic resins. When (meth) acrylonitrile and methyl methacrylate are included, it is preferable to blend 15 to 18 parts of (meth) acrylonitrile in 100 parts of acrylic resin and 20 to 80 parts of methyl methacrylate in 100 parts of acrylic resin.

In the present invention, the acrylic resin contained in the protective layer preferably has a glass transition point (Tg) higher than 30 ° C. and 130 ° C. or lower, and more preferably Tg higher than 50 ° C. and 95 ° C. or lower. . When Tg is 30 ° C. or less, the water resistance is sufficient, but the heat resistance is not sufficient, so that a good surface can be obtained when the protective layer in a wet state is pressed against a heated mirror drum and dried. Therefore, sufficient stick resistance may not be obtained. On the other hand, when Tg is high, stick resistance and scratch resistance tend to be improved. However, when Tg is higher than 130 ° C., the protective layer becomes brittle and water resistance, plasticizer resistance and solvent resistance are not sufficient. , The desired effect may not be obtained. The Tg of acrylic resin is measured by differential scanning calorimetry (DSC).

In the present invention, the acrylic resin contained in the protective layer is preferably a non-core shell type. In general, the core-shell type acrylic resin is frequently used because it has better heat resistance than the non-core-shell type acrylic resin, and has excellent stick resistance when used in a coating layer. However, since the shell portion of the core-shell type acrylic resin usually has a low thermal conductivity, it also has the disadvantage of poor color development sensitivity. On the other hand, the normal non-core shell type acrylic resin has low heat resistance and has the disadvantage that sticks and head debris are easily generated. However, the non-core shell type has a Tg of 30 ° C. or higher and 130 ° C. or lower. Acrylic resins are excellent in heat resistance, and therefore have the advantage of good color development sensitivity and good stick resistance and head residue resistance.

In the present invention, the method of pressing and drying the wet protective layer on a heated mirror drum is not particularly limited, but a cast coating method is usually used. As the cast coating method, in general, (1) a wet casting method (direct method) in which a coating layer is pressed against a heated drum that is mirror-finished while the coating layer is in a wet state (direct method), and (2) a wet coating layer is formed. Once (semi-) dried, swell plasticized with a rewetting liquid (rewetting liquid), pressed against a heated drum with a mirror finish and dried (rewetting method), (3) solidified wet coating layer It is classified into the gelation cast method (coagulation method) in which the gel state is obtained by the treatment, and it is pressed against a heated mirror drum and dried. Because of the following characteristics, it is desirable to use the rewet cast method (rewetting method) in the present invention.

  The wet cast method and gelled cast method are pressed against the mirror drum and dried while the coating layer is in a wet state, which increases the drying load on the mirror drum, but there is a limit to improving the drying capability of the mirror drum. Because there is, it is forced to operate at low speed. On the other hand, in the rewet cast method, the dried coating layer is rewet with the rewet liquid and then brought into pressure contact with the mirror drum. Therefore, the drying itself can be performed in the previous step, and the mirror drum needs only a small drying load. The coating speed is easy to increase compared to the coating method and solidification method.

  The rewetting liquid (rewetting liquid) used in the rewetting cast method is not particularly limited, but usually a fatty acid such as stearic acid or oleic acid or a salt thereof, or a release agent such as polyethylene wax or lecithin. An aqueous liquid having a main component is used. The main action of the rewetting liquid is to wet plasticize the upper layer portion of the dried coating layer with water occupying most of the liquid. As a result, the wet coating layer is brought into close contact with the mirror drum to copy the mirror surface, thereby improving the surface properties and the like. In addition to the above releasing agent, a fluorescent dye, a dye, an ink fixing agent, a colloidal pigment, a surfactant, and the like may be added to the rewetting liquid as long as the effects of the present invention are not impaired. In addition, a pigment dispersant, a water retention agent, a thickening agent, an antifoaming agent, a preservative, a coloring agent, a water resistant agent, a wetting agent, an ultraviolet absorber, a cationic polymer electrolyte, and the like may be appropriately added as necessary. it can.

In the present invention, the temperature of the mirror drum and the pressure to be pressed when the protective layer in a wet state is pressed against the heated mirror drum and dried are not particularly limited, and it is desirable to adjust appropriately. The temperature of the mirror drum is 30 to 130 ° C., preferably 60 to 100 ° C., and the pressure is linear pressure 50 to 300 kN / m, preferably 100 to 250 kN / m.
If the temperature of the mirror drum is too low, the protective layer will be insufficiently dried, and if it is too high, there may be a problem that the white paper portion of the thermal recording medium is colored by heat. On the other hand, if the pressure to be pressed is too low, a heat-sensitive recording material having good surface properties cannot be obtained. If the pressure is too high, the heat-sensitive recording layer of the heat-sensitive recording material may be crushed and color development may be deteriorated.
In the present invention, a particularly good surface can be obtained by adjusting the temperature of the mirror drum to a temperature higher than the glass transition point (Tg) of the acrylic resin, and the effects of the present invention are remarkably exhibited. Therefore, it is preferable.

The undercoat layer containing the organic hollow particles of the present invention acts as a heat insulating layer during printing by a printer or the like, and it is possible to efficiently use thermal energy from a thermal head, etc. Bring. In addition, the heat-sensitive recording material having the undercoat layer is excellent in print image quality (dot reproducibility) because of its high elasticity.

Further, the undercoat layer containing the organic hollow particles of the present invention also acts as a heat insulating layer when the wet protective layer is pressed against a heated mirror drum and dried. For this reason, it is possible to efficiently use the heat energy from the mirror drum, and the protective layer is consolidated or the surface property and thermal conductivity of the protective layer are remarkably improved, and particularly good quality is obtained.

The organic hollow particles contained in the undercoat layer of the present invention are fine hollow particles that are already foamed and contain a thermoplastic resin as a shell and contain air or other gas inside. Examples of the thermoplastic resin include polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylic acid ester, polyacrylonitrile, polybutadiene, and copolymers thereof. In particular, styrene resins such as polystyrene, acrylic resins such as polyacrylic acid esters and polyacrylonitrile, copolymers thereof, or copolymer resins mainly composed of polyvinylidene chloride and polyacrylonitrile are preferable. Such organic hollow particles are available as SX8782 manufactured by JSR, MH5055 and MH8103K manufactured by Nippon Zeon, and Ropaque HP-91 manufactured by Rohm & Haas Japan.

The hollow ratio of the organic hollow particles of the present invention is preferably 40 to 90%, more preferably 50 to 90%. If the hollow ratio is less than 40%, the heat insulating property is insufficient, and heat energy from a thermal head or a mirror drum is likely to be released to the outside of the thermal recording medium through the support, so that the effect may be insufficient. .
Here, the hollow ratio is calculated from the outer diameter and inner diameter of the hollow particles, and is represented by the hollow ratio = (the inner diameter of the hollow particles / the outer diameter of the hollow particles) ³ × 100 (%).

The average particle diameter of the organic hollow particles of the present invention is preferably 0.5 to 10 μm, more preferably 1 to 5 μm. When the average particle size is larger than 10 μm, the smoothness of the surface after coating and drying is lowered, and thus the adhesion between the thermal recording medium and the thermal head or the like or the mirror drum is lowered, and a sufficient effect may not be obtained. is there. On the other hand, if the average particle diameter is smaller than 0.5 μm, the amount of the gas contained in the hollow particles is small, so that the heat insulating property is lowered and a sufficient effect may not be obtained.
Here, the average particle diameter is indicated by a median diameter d _{50 in} which the particles on the large side and the small side are equivalent (volume basis) when the particles are divided into two according to the diameter. Can be measured.

In the present invention, in order to provide the undercoat layer on a support, an undercoat layer coating solution in which the organic hollow particles are dispersed in a solvent such as water together with a binder such as a water-soluble polymer substance and an aqueous polymer emulsion is supported. It is obtained by coating and drying on the body surface. In this case, the content of the organic hollow particles in the undercoat layer is preferably 10% by weight or more, more preferably 20% by weight or more, and particularly preferably 50% by weight or more based on the total solid content of the undercoat layer. When the content of the organic hollow particles in the undercoat layer is less than 10% by weight, the heat insulation becomes insufficient, and heat energy from a thermal head or a mirror drum is likely to be released out of the thermal recording medium through the support. The effect may be insufficient.
Further, the coating amount of the organic hollow particles is preferably a dry weight is 1.5 g / ^{m 2} or ^more, and more preferably ^{2.0g / m 2 ~7.0g / m 2} . When the coating amount of the organic hollow particles is less than 1.5 g / m ² in terms of dry weight, the heat insulation becomes insufficient, and heat energy from a thermal head or mirror drum is released to the outside of the thermal recording medium through the support. Because it is easy to be done, the effect may become insufficient.

In the present invention, the binder used when the undercoat layer is provided includes fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, and sulfonic acid-modified polyvinyl alcohol. , Butyral modified polyvinyl alcohol, olefin modified polyvinyl alcohol, nitrile modified polyvinyl alcohol, pyrrolidone modified polyvinyl alcohol, silicone modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer Styrene-butadiene copolymer and ethyl cellulose, Cellulose derivatives such as cetyl cellulose, casein, gum arabic, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylate, polyvinyl butyral, polystyrose and the like Examples of such copolymers, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, coumarone resins, and the like can be given. 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.
The content of the binder in the undercoat layer is not particularly limited as long as it is sufficient to bind the undercoat layer to the support, but is usually 5% by weight to the total solid content of the undercoat layer. About 40% by weight.

In the undercoat layer of the present invention, together with the organic hollow particles and the binder, known pigments, for example, silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, as long as the desired effects on the above problems are not impaired. Inorganic or organic fillers such as aluminum hydroxide can be included.

Next, various materials used in the heat-sensitive recording layer of the heat-sensitive recording material of the present invention are exemplified, but a binder, a crosslinking agent, a pigment, and the like are provided as necessary as long as the desired effects on the above-described problems are not inhibited. It can also be used for each coating layer.

As the leuco dye that can be used in the heat-sensitive recording material of the present invention, those known in the field of conventional pressure-sensitive or heat-sensitive recording paper can be used, and are not particularly limited. Fluorane compounds, fluorene compounds, divinyl compounds and the like are preferable. Specific examples of typical colorless or light-colored dyes (dye precursors) are shown below. These dye precursors 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-di Tilamino-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-ethoxy Ethyl-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-methyl-fluorane, 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-7-chlorofluorane, 3-dibutylamino-6-ethoxyethyl-7-anilinofluorane, 3-dibutylamino-6-chloro-7-anilinofluorane, 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-pentylamino-6-methyl-7- (p-chloroanilino) fluorane, 3-di-n-pentylamino-7- (m-trifluoro Methylanilino) fluorane, 3-di-n-pentylamino-6-chloro-7-anilinofluorane, 3-di-n-pentylamino-7- (p-chloro) Nilino) 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-toludino) -6-methyl-7-ani Linofluorane, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamylamino) -6-chloro-7-a Linofluorane, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isobutylamino) -6-methyl-7-anilinofur Oran, 3- (N-ethyl-N-ethoxypropylamino) -6-methyl-7-anilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2- (4-oxahexyl) -3-dimethyl Amino-6-methyl-7-anilinofluorane, 2- (4-oxahexyl) -3-diethylamino-6-methyl-7-anilinofluorane, 2- (4-oxahexyl) -3-dipropyl Amino-6-methyl-7-anilinofluorane, 2-methyl-6-p- (p-dimethylaminophenyl) aminoanilinofluorane, 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) aminoanilinofluorane, 2-amino-6-p- (p-diethylaminophenyl) aminoanilinofluorane, 2-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane, 2-phenyl-6-methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane, 2-benzyl-6 -P- (p-phenylaminophenyl) aminoanilinofluorane, 2-hydroxy-6-p- (p-phenylamino) Nophenyl) aminoanilinofluorane, 3-methyl-6-p- (p-dimethylaminophenyl) aminoanilinofluorane, 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) fluorane-γ- (4′-nitro) anilinolactam, 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylamino) Enyl) -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] -methylmalonic acid dimethyl ester

As the developer that can be used in the heat-sensitive recording material of the present invention, those known in the field of conventional pressure-sensitive or heat-sensitive recording paper can be used, and are not particularly limited. For example, activated clay Inorganic acid substances such as 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, 4-hydroxybenzoic acid benzyl, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'- Isopropoxydiphenyl sulfone, 4-hydroxy-4'-n-propoxy Diphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl-4'- Methylphenylsulfone, aminobenzenesulfonamide derivatives described in JP-A-8-59603, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, bis ( p-hydroxyphenyl) butyl 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′-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, 2,2′-thiobis (3-tert-octylphenol), 2,2′-thiobis (4-tert-octylphenol) , Phenolic compounds such as diphenylsulfone crosslinking type compounds described in WO97 / 16420, compounds described in WO02 / 081229 or JP2002-301873, and thios such as N, N′-di-m-chlorophenylthiourea Urea compound, 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] aromatic carboxylic acids of salicylic acid and polyvalent metal salts of these aromatic carboxylic acids such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, etc. Examples thereof include an antipyrine complex of zinc thiocyanate and a complex zinc salt of terephthalaldehyde acid and other aromatic carboxylic acid. The diphenylsulfone cross-linking compound described in WO 97/16420 is available as a trade name D-90 manufactured by Nippon Soda Co., Ltd. Moreover, the compound as described in WO02 / 081229 etc. is available as Nippon Soda Co., Ltd. brand name NKK-395 and 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. These developers can be used alone or in combination of two or more.

  As the sensitizer usable in the heat-sensitive recording material of the present invention, conventionally known sensitizers 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, phenyl p-toluenesulfonate, and the like. These sensitizers may be used alone or in combination of two or more.

The binder usable in the heat-sensitive recording material of the present invention includes fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, and butyral-modified. Polyvinyl alcohol, olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, other modified polyvinyl alcohols, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene- Butadiene copolymer and ethyl cellulose, acetyl cellulose Cellulose derivatives such as casein, arabic gum, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylate, polyvinyl butyral, polystyrose and their co-polymers Examples include coalescence, polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, coumarone resin, and the like. 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 cross-linking agent that can be used in the heat-sensitive recording material of the present invention include glyoxal, methylol melamine, melamine formaldehyde resin, melamine urea resin, polyamine epichlorohydrin resin, polyamide epichlorohydrin resin, potassium persulfate, ammonium persulfate, persulfate. Examples thereof include sodium sulfate, ferric chloride, magnesium chloride, borax, boric acid, alum, and ammonium chloride.

  Examples of the pigment that can be used in the heat-sensitive recording material of the present invention include inorganic or organic fillers such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, and aluminum hydroxide. The pigment used in the protective layer is preferably kaolin, calcined kaolin, or aluminum hydroxide in consideration of thermal head wear and the like.

Examples of the lubricant that can be used in the heat-sensitive recording material of the present invention include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, and silicone resins.

Further, in the present invention, 4,4′-butylidene (6-tert-butyl-3-methylphenol) is used as an image stabilizer exhibiting an oil resistance effect of a recorded image and the like within a range that does not hinder a desired effect on the above 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-butylphenyl) butane, 4-benzyloxy-4 ′-(2,3-epoxy-2-methylpropoxy) diphenyl sulfone, etc. Can also be added.
In addition, benzophenone or triazole ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, and the like can be used.

  The leuco dye, developer, sensitizer and materials added as necessary for the heat-sensitive recording layer of the heat-sensitive recording material of the present invention are added by a pulverizer such as a ball mill, an attritor or a sand glider, or an appropriate emulsifying device. It is atomized to a particle size of several microns or less, and various additive materials are added depending on the binder and purpose to obtain a coating solution. The amount of the material is determined according to the required performance and recording suitability and is not particularly limited. However, the developer is 0.5 to 10 parts by weight, and the sensitizer 0.5 to 1 part by weight with respect to 1 part by weight of the leuco dye. The amount is preferably about 10 parts by weight.

In the present invention, an undercoat layer containing the organic hollow particles and the binder on an arbitrary support such as paper, recycled paper, synthetic paper, film, plastic film, foamed plastic film, nonwoven fabric, and a composite sheet combining these Then, after sequentially applying the heat-sensitive recording layer having the above composition, the protective layer is applied, and the protective layer in a wet state is pressed against a heated mirror drum and dried to obtain the desired heat-sensitive recording. The body is obtained.
The coating amount of the thermosensitive recording layer provided on the undercoat layer is not particularly limited, but is preferably in the range of ² to 12 g / m ² by dry weight. The coating amount of the protective layer provided on the heat-sensitive recording layer is not particularly limited, but it is preferably in the range of 0.5 to 5 g / m ² in terms of dry weight because particularly good print density and image quality can be obtained.

  The heat-sensitive recording material of the present invention can further provide curl correction by providing a backcoat layer on the opposite surface of the support to the heat-sensitive recording layer.

The means for applying each layer such as the undercoat layer, the heat-sensitive recording layer, the protective layer, and the backcoat layer is not particularly limited, and can be applied according to well-known conventional techniques. Coating methods for each layer include air knife method, rod blade method, vent blade method, bevel blade method, roll method, slot type curtain method, slide type curtain method, slide hopper type curtain method, bead type curtain method, spray method The die method and the like can be exemplified, and these coating methods are appropriately selected and used.
Further, 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 thermal recording material of the present invention will be described below with reference to examples and comparative examples. In the description, parts and% represent parts by weight and% by weight, respectively. Various 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 1.
<Undercoat layer coating solution 1>
Organic hollow particles 1 (manufactured by Zeon Corporation: MH8103K, hollow ratio 50%,
400 parts styrene-butadiene copolymer latex (manufactured by Nippon Zeon Co., Ltd .: ST5526)
Solid content 48%) 40 parts completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd .: PVA117,
Solid content 10%) 30 parts Water 30 parts

Next, after coating the undercoat layer coating liquid 1 on one side of a support (basic paper having a basis weight of 60 g / m ² ) by a vent blade method so that the coating weight is 8.0 g / m ² by dry weight. Then, drying was performed to obtain an undercoat layer-coated paper.

Next, the developer dispersion liquid (A liquid), the leuco dye dispersion liquid (B liquid), and the sensitizer dispersion liquid (C liquid) having the following blending were each individually adjusted to an average particle size of 0.5 microns with a sand grinder. Wet grinding was performed until
Developer dispersion (liquid A)
4-hydroxy-4′-n-propoxydiphenylsulfone 6.0 parts fully saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd .: PVA117,
Solid content 10%) 18.8 parts water 11.2 parts leuco dye dispersion (liquid B)
3-dibutylamino-6-methyl-7-anilinofluorane (manufactured by Yamada Chemical Co., Ltd .:
ODB-2) 3.0 parts fully saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd .: PVA117,
6.9 parts water 3.9 parts sensitizer dispersion (liquid C)
Diphenylsulfone 6.0 parts fully saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd .: PVA117,
Solid content 10%) 18.8 parts water 11.2 parts

Subsequently, the dispersion liquid was mixed at the following ratio to prepare a thermosensitive recording layer coating liquid.
<Thermosensitive recording layer coating solution>
Developer dispersion (liquid A) 36.0 parts leuco dye dispersion (liquid B) 13.8 parts Sensitizer dispersion (liquid C) 36.0 parts Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd .: PVA117,
(Solid content 10%) 10.0 parts water 25.0 parts

Next, the thermosensitive recording layer coating solution was applied on the undercoat layer of the undercoat layer-coated paper by the rod blade method so that the coating weight was 5.0 g / m ² by dry weight, followed by drying. A heat-sensitive recording layer coated paper was obtained.

Subsequently, the mixture which consists of the following ratio was mixed and it was set as the protective layer coating liquid.
<Protective layer coating solution>
Aluminum hydroxide (Martinsberg OL: Martin Fin OL)
50% dispersion 12.0 parts non-core shell type acrylic resin (Mitsui Chemicals, Inc .: ASN1004K, Tg55 ° C.,
Solid content 18%) 30.0 parts Zinc stearate (manufactured by Chukyo Yushi Co., Ltd .: Hydrin L536, solid content 40%) 2.0 parts Water 70.0 parts

Next, the protective layer coating solution is applied on the heat-sensitive recording layer of the heat-sensitive recording layer-coated paper by a rod blade method so that the coating amount is 3.0 g / m ² by dry weight, and then dried. A heat-sensitive recording material was produced by treating the surface of the protective layer with a super calendar so that the smoothness of the protective layer was 1000 to 2000 seconds.

A blend consisting of the following blends was stirred and dispersed to prepare a rewetting liquid.
<Rewetting liquid>
Release agent (San Nopco: PEM-17, solid content 40%) 1.25 parts Surfactant (San Nopco: SN-WET-L, solid content 100%) 0.1 part Water 96.4 parts

Next, 50 g / m ² of a rewetting liquid was applied onto the protective layer of the thermal recording material, and the rewetting protective layer was cast onto the cast drum having a surface temperature of 70 ° C. while the protective layer was in a wet state. The heat-sensitive recording material of Example 1 was produced by applying pressure treatment and heating (drying) treatment at a linear pressure of 100 kN / m using a rubber roll. (Rewet cast processing)

[Example 2]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the following undercoat layer coating solution 2 was used.
<Undercoat layer coating solution 2>
Organic hollow particles 1 (manufactured by Zeon Corporation: MH8103K, hollow ratio 50%,
Average particle size 1.1 μm, solid content 25%) 100 parts calcined kaolin (manufactured by Engelhard: Ansilex 90) 75 parts styrene / butadiene copolymer latex (manufactured by Nippon Zeon: ST5526)
Solid content 48%) 40 parts completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd .: PVA117,
Solid content 10%) 30 parts Water 30 parts

[Example 3]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the following undercoat layer coating solution 3 was used.
<Undercoat layer coating solution 3>
Organic hollow particles 2 (Rohm & Haas Japan, Inc .: Ropeke HP-91,
Hollow part 51%, average particle size 1.0 μm, solid content 25%) 400 parts styrene / butadiene copolymer latex (manufactured by Nippon Zeon Co., Ltd .: ST5526)
Solid content 48%) 40 parts completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd .: PVA117,
Solid content 10%) 30 parts Water 30 parts

[Comparative Example 1]
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the following undercoat layer coating solution 4 was used.
<Undercoat layer coating solution 4>
Baked kaolin (manufactured by Engelhard: Ansilex 90) 100 parts styrene / butadiene copolymer latex (manufactured by Nippon Zeon: ST5526)
Solid content 48%) 40 parts completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd .: PVA117,
Solid content 10%) 30 parts water 330 parts

[Comparative Example 2]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the rewet casting process was not performed.

The following evaluation tests were performed on the heat-sensitive recording materials obtained in the above Examples and Comparative Examples.

<Color development sensitivity>
The produced thermal recording medium was solid-printed with an applied energy of 0.15 mJ / dot or an applied energy of 0.35 mJ / dot using a printing tester (Okura Electric Co., Ltd .: TH-PMD, equipped with a Kyocera thermal head). . The density of the printed part was measured with a Macbeth densitometer (RD-914, using an amber filter) to evaluate the color development sensitivity.

<Print quality>
The produced heat-sensitive recording material was solid-printed at an applied energy of 0.27 mJ / dot using a printing tester (manufactured by Okura Electric Co., Ltd .: TH-PMD, equipped with a thermal head manufactured by Kyocera Corporation). The image quality after printing was visually evaluated according to the following criteria.
○: Unevenness is not seen at all.
Δ: Slight unevenness is observed.
X: Unevenness is observed.

<Glossy>
About the produced thermosensitive recording material, according to JIS-P8142, the 75 degree glossiness of the surface of a protective layer was measured using the gloss meter (Nippon Denshoku Industries Co., Ltd. product: VG7000).

<Water resistance>
The produced thermosensitive recording medium was solid-printed with an applied energy of 0.35 mJ / dot using a printing tester (Okura Electric Co., Ltd .: TH-PMD, equipped with a Kyocera thermal head). After immersion in water at 23 ° C. and 50% Rh for 24 hours, the recording density of the printed part is measured with a Macbeth densitometer (RD-914, using an amber filter), and the residual rate is calculated from the values before and after the treatment. The water resistance was evaluated.
Residual rate (%) = (recording density after processing / recording density before processing) × 100

<Abrasion resistance>
About the produced thermal recording body, the protective layer surface was rubbed with the steel wool which added the load of 1000 gf / cm < ² >, and the color development was visually evaluated on the following reference | standard.
○: Almost no color developed.
Δ: Lightly colored.
X: Color develops deeply.

<Plasticizer resistance>
The produced thermosensitive recording medium was solid-printed with an applied energy of 0.35 mJ / dot using a printing tester (Okura Electric Co., Ltd .: TH-PMD, equipped with a Kyocera thermal head). A vinyl chloride wrap (manufactured by Mitsui Toatsu Co., Ltd .: High Wrap KMA) is wrapped around a paper tube in a single layer, and the thermal recording medium is placed on the paper so that the printed part is on the outer surface. Was fixed in a three-fold manner. After processing for 24 hours in an environment of 23 ° C. and 50% RH, the recording density of the printed part was measured with a Macbeth densitometer (RD-914, using an amber filter), and the residual ratio was calculated from the values before and after the processing.
Residual rate (%) = (recording density after processing / recording density before processing) × 100

Claims (4)

In a heat-sensitive recording medium in which an undercoat layer containing organic hollow particles, a heat-sensitive recording layer containing a colorless to light-colored electron-donating leuco dye and an electron-accepting developer, and a protective layer are sequentially provided on a support, A heat-sensitive recording material, wherein the protective layer in a state is pressed against a heated mirror drum and dried. The heat-sensitive recording material according to claim 1, wherein the protective layer contains a carboxyl group-containing resin. The heat-sensitive recording material according to claim 2, wherein the carboxyl group-containing resin is an acrylic resin. The heat-sensitive recording material according to claim 1, wherein the protective layer is treated by a rewet cast method.