JP2006044030A - Double-sided recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording/thermosensitive recording hybrid double-sided recording medium, in which the recordability of an inkjet recording surface is favorable and neither fogging nor decolorizing develops in the thermosensitive recording surface. <P>SOLUTION: In this double-sided recording medium, the inkjet recordability is imparted to one side of a support mainly made of pulp, on the opposite side of which a thermosensitive color developing layer and a protective layer, the protective layer includes a self-emulsifiable polymeric acrylic resin and a water-soluble modified polyamine resin. In at least one kind of the double-sided recording media, an electron acceptable compound is selected from the group consisting of 2,4'-dihydroxy diphenyl sulfone, 4,4'-dihydroxy diphenyl sulfone, bis(3-allyl-4-hydroxy phenyl)sulfone and 4-hydroxy-4'-isopropoxy diphenyl sulfone. This double-sided recording medium, at least one layer of intermediate layers is mainly made of plastic spherical microballoons. In this double-sided recording medium, the Cobb water absorption degree of the surface, especially the surface having a fitness to inkjetting is at least 10 g/m<SP>2</SP>and not more than 50 g/m<SP>2</SP>. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a double-sided recording medium having a thermal recording aptitude on one side and an ink jet recording aptitude on the opposite side.

  The ink jet recording method using water-based ink is suitable for terminal printers, facsimiles, plotters, form printing, etc. for reasons such as low noise during recording, easy colorization, and high-speed recording. Application is underway. High-quality paper and coated paper used for general printing have poor ink absorbability, so the printed ink will not dry on the paper surface and will remain for a long time, contaminating the device and continuously printed sheets. Since the image is dirty, it is not practical. In order to solve such problems, proposals have been made to use a recording paper having a low sizing degree or to impregnate a base paper internally containing urea-formalin resin with a water-soluble polymer. Furthermore, a recording paper is disclosed in which various porous inorganic pigments such as amorphous silica are coated on the surface for the purpose of improving the color development and reproducibility of the ink. In addition, for the purpose of obtaining high-definition images with reduced blurring, improvements such as defining physical properties of these porous pigments have been proposed.

  Also, as inkjet recording methods become more common, it is proposed to use two or more types of porous pigments with different pore radii as appropriate in order to achieve both paper suitability and recording suitability, such as writing with a pencil. It has been achieved for the time being. However, the development of inkjet printer technology in recent years has been remarkable, and recently, there are also developments that are almost comparable to the image quality of silver halide photography. However, as the accuracy of the printer has improved and it has penetrated into offices and homes, A new request has emerged that could not be seen too much. One of these is high-speed double-sided recording.

  The ink jet recording method is a method of recording by causing the ejected ink droplets to land on the surface of the recording medium. Therefore, it is necessary to improve the landing accuracy in order to obtain a recorded material with high accuracy and excellent image reproducibility. For this reason, the direction in which ink is ejected from the head is limited to the direction in which gravity is applied, that is, the direction from top to bottom, and it is difficult to record both sides simultaneously. Although it is possible to invert the recording medium and record the opposite side after recording one side, it is not a means for speeding up, it is practical because the mechanism of the printer becomes complicated and the size increases It's hard to say.

  By the way, considering the practical usage of the printer, the case where high-speed double-sided recording is most urgently needed is when a large amount of double-sided printing is required. In ordinary households, this is equivalent to printing postcards such as New Year's cards, summer greetings, greetings, and invitations. In these cases, various designs and characters are recorded on the back side, but the front side is usually only the address, and there is almost no problem in monochrome printing. However, when this is processed only by the conventional ink jet printer, it has been necessary to reset all sheets to the printer again after the recording on one side is completed and to perform recording on the opposite side.

  In order to solve this problem, a double-sided recording medium that does not cause problems such as fogging of the thermosensitive coloring layer due to the solvent in the inkjet ink or decoloration of the printing of the thermosensitive coloring layer during simultaneous recording by the inkjet printer and the thermal printer. However, the effect is insufficient, and there is a problem that the heat-sensitive color forming layer is fogged by the solvent in the ink-jet ink, and the print on the heat-sensitive color developing layer is decolored. (For example, Patent Document 1)

On the other hand, in the field of thermosensitive recording paper, it has been proposed to provide various protective layers for the purpose of improving the chemical resistance of the thermosensitive coloring layer, and a protective composition containing a self-emulsified acrylic resin and polyvinyl alcohol. Although a layer has been proposed, the effect is insufficient with respect to the solvent in the inkjet ink, and when the recording surface of the thermal recording material comes into contact with the recording surface of the inkjet recording material, the background of the thermal recording material is covered with the fog. And the problem that the density of the image area is reduced cannot be solved. (For example, Patent Document 2)
JP 2000-272235 A JP 2000-006525 A

  An object of the present invention is to solve the above problems, and to provide a recording method capable of high-speed double-sided recording and at least one side suitable for color recording and a recording medium suitable for the method. With respect to ink jet recording, it has good ink jet recording suitability, and on the heat sensitive recording surface, the solvent in the ink jet ink does not cause fogging on the heat sensitive color developing layer, and the printing on the heat sensitive color developing layer is not erased. A double-sided recording medium for thermal recording and inkjet recording is provided.

  As a result of intensive studies, the inventor has provided a heat-sensitive color developing layer containing an electron-donating colorless dye and an electron-accepting compound on one side of a support mainly composed of pulp, and a protective layer on the heat-sensitive color developing layer. In a double-sided recording medium with ink jet aptitude provided on the surface, it can provide a recording medium that can meet the above-mentioned requirements by containing an acrylic resin self-emulsified in the protective layer and a water-soluble modified polyamine resin. As a result, the present invention has been completed. Preferably, by providing an intermediate layer between the recording medium support and the thermosensitive coloring layer, an intermediate layer mainly composed of plastic spherical fine hollow particles is suitable for high-speed double-sided recording, and at the same time, the thermosensitive coloring layer. It has been found that a recording medium free from fogging and decoloring can be obtained.

The present invention includes the following embodiments.
[1] A heat-sensitive color-forming layer containing an electron-donating colorless dye and an electron-accepting compound and a protective layer on the heat-sensitive color-generating layer are provided on one side of a support mainly composed of pulp, and ink jet suitability is imparted to the other side. A double-sided recording medium comprising an acrylic resin self-emulsified and polymerized in a protective layer and a water-soluble modified polyamine resin.
[2] The electron-accepting compound is 2,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4′-isopropoxy. A double-sided recording medium comprising at least one selected from diphenylsulfone.
[3] A double-sided recording medium, wherein the surface having ink jet aptitude has a 30-second Cobb water absorption measured with a 5% isopropyl alcohol aqueous solution of 10 g / m ² or more and 50 g / m ² or less.
[4] A double-sided recording medium, wherein the surface having ink jet recording suitability contains a cationic resin.
[5] A double-sided recording medium, wherein an ink receiving layer having ink jet suitability is provided on the other surface of the support.
[6] The double-sided recording medium, wherein the ink receiving layer contains a cationic resin.
[7] A double-sided recording medium, wherein one or more intermediate layers are provided between the support and the thermosensitive coloring layer.
[8] A double-sided recording medium, wherein at least one of the intermediate layers is mainly composed of plastic spherical fine hollow particles.

  As described above in detail, the double-sided recording medium of the present invention in which the thermosensitive coloring layer and the protective layer are provided on one side of the support and the other side has ink jetting aptitude is good on both the front and back sides. A recorded image can be obtained, high-speed recording on both sides is possible, and the amount of recorded information can be increased.

Hereinafter, the double-sided recording medium of the present invention will be described in the order of the protective layer, the thermosensitive coloring layer, the intermediate layer, the support and the ink jet aptitude to the support.
<< 1. Protective layer >>
A protective layer is provided on the thermosensitive coloring layer. In particular, by including an acrylic resin self-emulsified and a water-soluble modified polyamine resin in the protective layer, the ink on the ink jet recording surface can be prevented from adversely affecting the adjacent thermosensitive coloring layer.

  Self-emulsion polymerized acrylic resins include hydrophobic acrylic monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylate-2-ethylhexyl. (Meth) acrylic acid, itakoic acid, maleic acid, (meth) acrylic acid-2-aminoethyl, (meth) acrylic acid-2- (N-dimethylamino) ethyl, (meth) acrylic acid-2- After emulsification with a hydrophilic monomer such as hydroxyethyl or glycidyl (meth) acrylate, it can be obtained by a radical polymerization method. In particular, a nonionic self-emulsion polymerized acrylic resin is preferred. The molecular weight of the self-emulsion polymerized acrylic resin is about 10,000 to 1,000,000.

  The amount of the self-emulsion-polymerized acrylic resin is not particularly limited, but if it is less than 10% by mass based on the total solid content of the protective layer, there is a possibility that the adhesion of the protective layer to the thermosensitive coloring layer may not be sufficient. Depending on the solvent in the ink, fogging may occur in the thermosensitive coloring layer, or printing on the thermosensitive coloring layer may be erased. On the other hand, if it exceeds 50% by mass, the solvent in the ink-jet ink may penetrate into the thermosensitive coloring layer, causing fogging in the thermosensitive coloring layer or decoloring the printing of the thermosensitive coloring layer. About mass% is particularly preferable. In addition, a normal resin emulsion-polymerized using an emulsifier, that is, a latex is not preferable because the emulsifier in the latex promotes the penetration of the solvent in the ink-jet ink into the thermosensitive coloring layer.

  Examples of the water-soluble modified polyamine resin used in the present invention include carboxyl-modified, hydroxyl-modified, and imino-modified polyamine resins. Further, the amount of the water-soluble modified polyamine resin is not particularly limited, but if it is less than 10% by mass with respect to the total solid content of the protective layer, the solvent in the ink-jet ink may cause fogging in the thermosensitive coloring layer, Printing on the coloring layer may be erased. On the other hand, if it exceeds 80% by mass, the protective layer may not be sufficiently adhered to the heat-sensitive color developing layer, and the heat-sensitive color developing layer may be fogged or the print on the heat sensitive color developing layer may be erased. About 10-80 mass% is especially preferable.

  In order to further improve the chemical resistance of the heat-sensitive recording material in the protective layer of the present invention, a crosslinking agent having the ability to crosslink the water-soluble modified polyamine resin can be added as necessary. Specifically, aldehyde compounds such as formalin and glyoxal, methylol compounds such as urea resin, melamine resin and phenol resin, epoxy compounds such as polyfunctional epoxy resin and polyamide epichlorohydrin resin, polyvalent isocyanate compound, block isocyanate compound, etc. Oxidants such as isocyanate compounds, persulfates and peroxides. These preferable addition amounts are in the range of 0.1 to 10 parts by mass of the crosslinking agent with respect to 100 parts by mass of the water-soluble modified polyamine resin. When the amount is less than this, the chemical resistance is lowered. On the other hand, when the amount is more than 10 parts by mass, the printing sensitivity and the recording running property are lowered.

  A higher fatty acid metal salt can be added to the protective layer in the present invention as needed for the purpose of further improving chemical resistance. Examples of the higher fatty acids include saturated fatty acids such as lauric acid having 10 or more carbon atoms, palmitic acid, stearic acid, behenic acid, oleic acid, and elaidic acid, and unsaturated fatty acids.

  Examples of the metal atom of the metal salt include alkali metal atoms such as sodium, potassium and lithium, alkaline earth metals such as magnesium, calcium and barium, and transition metals such as aluminum, nickel, copper, zinc and tin. However, calcium, aluminum, zinc, and tin are preferably used, and zinc is more preferably used from the viewpoint of improving the intended chemical resistance and coloring of the layer, safety, cost, and the like.

  A preferable addition amount of the higher fatty acid metal salt is 5 to 50 parts by mass of the higher fatty acid metal salt with respect to 100 parts by mass of the water-soluble modified polyamine resin. If the addition amount is less than this, no improvement is observed in chemical resistance. Even if the addition amount is more than this, the formation of a uniform film is hindered, resulting in a decrease in chemical resistance.

  In addition to the above-mentioned compounds, conventionally known water-soluble resins or water-dispersible resins can be mixed in the protective layer in the present invention. For example, polyvinyl alcohol, modified polyvinyl alcohol, starch or derivatives thereof, cellulose derivatives such as hydroxyethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid Acid terpolymer, alkali salt of polyacrylic acid, alkali salt of polymaleic acid, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, isobutylene / maleic anhydride copolymer A combined alkali salt, sodium alginate, gelatin, casein, an acid neutralized product of chitosan, and the like can be used.

  The protective layer can contain a pigment for the purpose of improving the recording runnability and the writing property. Specifically, diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, Inorganic pigments such as amorphous silica, amorphous calcium silicate and colloidal silica, and organic pigments such as melamine resin filler, urea-formalin resin filler, polyethylene powder and nylon powder can be used. Among these pigments, aluminum hydroxide is preferably used because it is effective for preventing wear of the thermal recording head, and amorphous silica is effective for preventing sticking.

  In addition, for the purpose of improving the recording runnability such as head wear prevention and sticking prevention, the protective layer may contain higher fatty acid amides such as stearamide, waxes such as paraffin, polyethylene wax, polyethylene oxide, and caster wax as necessary. Added.

  A preferable addition amount of the pigment and wax is 5 to 50 parts by mass of the pigment and 5 to 50 parts by mass of the lubricant with respect to 100 parts by mass of the water-soluble modified polyamine resin. If the addition amount is less than this, the recording running property is lowered, and if the addition amount is more than this, the formation of a uniform film is hindered, the chemical resistance is lowered, and the printing sensitivity is further lowered.

The coating amount of the protective layer in the present invention, 0.3 to 10 / m ² are preferred. Here, if the coating amount is less than 0.3 g / m ² , sufficient image storage stability and background storage stability cannot be obtained, and conversely if it exceeds 10 g / m ² , the printing sensitivity is remarkably lowered.

≪2. Thermal coloring layer >>
In thermal recording, a thermosensitive coloring layer containing an electron-donating colorless dye and an electron-accepting compound is heated by a thermal head or the like to be colored and recorded. This method is suitable for various printers, facsimiles and the like because the maintenance of the machine device is easy. In thermal recording, the positional relationship between the recording head and the recording layer is not limited as in inkjet recording, and the apparatus can be downsized. The thermosensitive coloring layer contains at least an electron donating colorless dye and an electron accepting compound, and preferably further contains a sensitizer and a pigment.
<Electron donating colorless dye>
Examples of the electron-donating colorless dye include the following compounds. However, the present invention is not limited to these. That is, as an electron-donating colorless dye that develops a black color, 3-di (n-butylamino) -6-methyl-7-anilinofluorane, 2-anilino-3-methyl-6-N-ethyl-N -Sec-butylaminofluorane, 3-di (n-pentylamino) -6-methyl-7-anilinofluorane, 3- (N-isoamyl-N-ethylamino) -6-methyl-7-anilino Fluorane, 3- (Nn-hexyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- [N- (3-ethoxypropyl) -N-ethylamino) -6-methyl -7-anilinofluorane, 3-di (n-butylamino) -7- (2-chloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-methyl-7- Nirinofuruoran, 3- (N-cyclohexyl--N- methylamino) -6-methyl-7-anilinofluoran, and the like.

Among these, 3-di (n-butylamino) -6-methyl-7-anilinofluorane, 2-anilino-3-methyl-6-N-ethyl-N-sec is preferred in terms of background fogging in the non-image area. -Butylaminofluorane, 3-diethylamino-6-methyl-7-anilinofluorane are preferred. Examples of the coating amount of the electron-donating colorless dye is preferably 0.1 to 1.0 g / m ^2, more preferably 0.2-0.5 g / m ² in terms of color density and background fog density.

<Electron-accepting compound>
The double-sided recording medium of the present invention has 2,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4 ′ as an electron-accepting compound. -At least one selected from isopropoxydiphenyl sulfone. The addition amount of the electron-accepting compound is preferably 50 to 400% by mass, and particularly preferably 100 to 300% by mass with respect to the electron-donating colorless dye. As the electron-accepting compound of the present invention, in addition to the above compounds, other known electron-accepting compounds may be used in combination as long as the effects of the present invention are not impaired. The known electron-accepting compounds can be appropriately selected and used, but phenolic compounds or salicylic acid derivatives and polyvalent metal salts thereof are particularly preferable from the viewpoint of suppressing background fogging.

  Examples of the phenolic compound include 2,2′-bis (4-hydroxyphenol) propane (bisphenol A), 4-t-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, and 1,1′-bis. (4-hydroxyphenyl) cyclohexane, 1,1′-bis (3-chloro-4-hydroxyphenyl) cyclohexane, 1,1′-bis (3-chloro-4-hydroxyphenyl) -2-ethylbutane, 4,4 '-Sec-isooctylidene diphenol, 4,4'-sec-butylene diphenol, 4-tert-octylphenol, 4-p-methylphenylphenol, 4,4'-methylcyclohexylidenephenol, 4,4' -Isopentylidenephenol, benzyl p-hydroxybenzoate, etc. It is below.

  Examples of the salicylic acid derivative include 4-pentadecyl salicylic acid, 3-5-di (α-methylbenzyl) salicylic acid, 3,5-di (tert-octyl) salicylic acid, 5-octadecylsalicylic acid, 5-α- (p-α-methylbenzylphenyl) ethylsalicylic acid, 3-α-methylbenzyl-5-tert-octylsalicylic acid, 5-tetradecylsalicylic acid, 4-hexyloxysalicylic acid, 4-cyclohexyloxy Examples include salicylic acid, 4-decyloxysalicylic acid, 4-dodecyloxysalicylic acid, 4-pentadecyloxysalicylic acid, 4-octadecyloxysalicylic acid and the like, and zinc, aluminum, calcium, copper, lead salts and the like thereof. In the present invention, when the known electron accepting compound is used in combination, the content of 2,4′-dihydroxydiphenyl sulfone according to the present invention is 50% by mass or more, particularly 70% by mass in the total electron accepting compound. % Or more is preferable.

  In the present invention, when preparing the coating liquid for the thermosensitive coloring layer, the particle diameter of the electron-accepting compound is preferably 1.0 μm or less, more preferably 0.5 to 0.7 μm in terms of volume average particle diameter. When the volume average particle size exceeds 1.0 μm, the color density may decrease. The volume average particle size can also be easily measured by a laser diffraction type particle size distribution analyzer (for example, LA500 (manufactured by Horiba)).

<Sensitizer>
In the double-sided recording medium of the present invention, the sensitivity can be greatly improved by using a sensitizer in the thermosensitive coloring layer. The content of the sensitizer is preferably 75 to 200 parts by mass and more preferably 100 to 150 parts by mass with respect to 100 parts by mass of the electron-accepting compound. When the amount of the sensitizer used is in the range of 75 to 200 parts by mass, the effect of improving the sensitivity is great, the image storability is good, and the background fog is good.

  As the sensitizer, conventionally, any sensitizer used in the field of thermal recording is preferably used. For example, 2-benzyloxynaphthalene, p-benzyloxybenzoic acid benzyl ester, 4,4′-dimethoxy In addition to benzophenone, stearyl urea, p-benzylbiphenyl, di (2-methylphenoxy) ethane, di (2-methoxyphenoxy) ethane, β-naphthol- (p-methylbenzyl) ether, α-naphthylbenzyl ether, 1, 4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-isopropylphenyl ether, 1,4-butanediol-p-tert-octylphenyl ether, 1-phenoxy-2- (4-ethylphenoxy) ) Ethane, 1-phenoxy-2- (chlorophenoxy) ethane, 1 , 4-butanediol phenyl ether, diethylene glycol bis (4-methoxyphenyl) ether, m-terphenyl, oxalic acid methylbenzyl ether, 1,2-diphenoxymethylbenzene, 1,2-bis (3-methylphenoxy) ethane 1,4-bis (phenoxymethyl) benzene and the like.

<Pigment>
In the double-sided recording medium of the present invention, it is preferable to contain a pigment in the thermosensitive coloring layer. For example, one or more pigments usually used in thermal recording, such as amorphous silica, calcium carbonate, aluminum hydroxide, and kaolin, can be suitably used.

  In the present invention, the electron-donating colorless dye, the electron-accepting compound, the sensitizer and the like are dispersed in a water-soluble binder. The water-soluble binder used in this case is preferably a compound that is soluble in 5% by mass or more with respect to 25 ° C. water. Specific examples of the water-soluble binder include polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, starches (including modified starch), gelatin, gum arabic, casein, saponified styrene-maleic anhydride copolymer, and the like. These binders are used not only for dispersion but also for the purpose of improving the coating strength of the thermosensitive coloring layer. For this purpose, styrene-butadiene copolymer, vinyl acetate copolymer, acrylonitrile-butadiene are used. Synthetic polymer latex binders such as copolymers, methyl acrylate-butadiene copolymers, and polyvinylidene chloride can also be used in combination.

  The above-mentioned dispersion of the electron-donating colorless dye, the electron-accepting compound, the sensitizer, and the like are simultaneously or separately dispersed by a stirring / pulverizing machine such as a ball mill, an attritor, and a sand mill to prepare a coating liquid. If necessary, a metal soap, wax, surfactant, antistatic agent, ultraviolet absorber, antifoaming agent, fluorescent dye, and the like may be added to the coating solution. As the metal soap, a higher fatty acid metal salt is used, and zinc stearate, calcium stearate, aluminum stearate and the like are used. As the above wax, paraffin wax, microcrystalline wax, carnauba wax, methylol stearamide, polyethylene wax, polystyrene wax, fatty acid amide wax and the like are used alone or in combination. As the surfactant, an alkali metal salt or ammonium salt of alkylbenzene sulfonic acid, a sulfosuccinic acid-based alkali metal salt, a fluorine-containing surfactant, or the like is used.

These materials are mixed and then applied to the support. The coating method is not particularly limited. For example, the coating method is performed using an air knife coater, a roll coater, a blade coater, a curtain coater or the like, dried, and smoothed with a calendar for use. A curtain coater is particularly preferred for the present invention. Further, the coating amount of the thermosensitive coloring layer is not limited and is usually preferably about ² to 10 g / m ² in terms of dry mass.

<< 3. Middle layer >>
The resin contained in the intermediate layer is selected from water-soluble polymers or latexes. For example, starch and derivatives thereof, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, natural or semi-synthetic polymers such as casein, gelatin and soybean protein, polyvinyl alcohols such as polyvinyl alcohol and silyl-modified polyvinyl alcohol, and cation-modified polyvinyl alcohol , Polyvinyl butyral resin, polyethyleneimine resin, polyvinylpyrrolidone resin, poly (meth) acrylic acid resin, acrylate ester resin, polyamide resin, polyacrylamide resin, polyester resin, urea resin, melamine resin, styrene Aqueous solution or aqueous dispersion of vinyl copolymer resin such as butadiene copolymer, methyl methacrylate / butadiene copolymer, ethylene / vinyl acetate copolymer, or the above Known materials modified polymer or the like by introducing anionic or cationic residues resins can be used as appropriate.

  The intermediate layer of the present invention may contain a pigment as necessary, calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, silicic acid Inorganic pigments such as calcium, magnesium silicate, white carbon, alumina, aluminum hydroxide, and organic pigments such as styrene, acrylic, urea resin, melamine resin, and benzoguanamine resin can be used.

Intermediate layer 2 to 15 g / m ² as a solid mass as the coating amount, preferably from 4~8g / m ^2, if less than 2 g / m ² difficult to obtain the effect of anti-solvent permeable, 15 g / m ² When the amount is larger, there is no problem with respect to the solvent permeation resistance, but it is often disadvantageous in terms of operation or economy.

  In the present invention, when an intermediate layer mainly composed of plastic spherical fine hollow particles is provided between the support and the heat-sensitive recording layer, the effects of improving sensitivity and improving image storage stability are further enhanced.

  The intermediate layer composed mainly of plastic spherical fine hollow particles acts as a heat insulating layer and as a solvent permeation preventive layer for ink-jet inks, and at the same time provides improved sensitivity through efficient use of thermal energy from a thermal head, etc. Contributes to the prevention of background fogging of the coloring layer and the improvement of image storage stability. When the plastic spherical fine hollow particles have an average particle diameter of 2 to 10 μm and a hollow ratio of 90% or more, flexibility is further improved, adhesion with the head is improved, and dot reproducibility is improved.

  The plastic spherical micro hollow particles used in the present invention are micro hollow particles having a thermoplastic resin as a shell and containing air or other gas inside, and are already in a foamed state. A 10 μm one is used. When the average particle diameter (particle outer diameter) is smaller than 2 μm, there are production problems such as it is difficult to obtain an arbitrary hollow ratio. Conversely, when the average particle diameter is larger than 10 μm, the smoothness of the surface after coating and drying. Therefore, the adhesiveness with the thermal head is reduced, and the sensitivity improvement effect is reduced. Therefore, it is preferable that such particle distribution has a uniform particle size distribution peak with little variation at the same time. Further, the fine hollow particles used in the present invention are preferably those having a hollow ratio of 50% or more, more preferably 90% or more, from the heat insulating effect. A material with a low hollowness has an insufficient heat insulation effect, so that heat energy from the thermal head is released to the outside of the heat-sensitive recording material through the support, resulting in poor sensitivity improvement effect. In addition, the hollow ratio said here is ratio of the outer diameter of a hollow particle, and an internal diameter, and is represented by a following formula.

  Hollow ratio = (inner diameter of hollow particles) / (outer diameter of hollow particles) × 100 Incidentally, the fine hollow particles used in the present invention have a thermoplastic resin as a shell as described above. In particular, a copolymer resin mainly composed of vinylidene chloride and acrylonitrile is preferable.

<< 4. Giving supportability and inkjet suitability to support >>
The pulp for paper used for the support of the present invention includes chemical pulp such as softwood bleached kraft pulp (hereinafter referred to as NBKP) and hardwood bleached kraft pulp (hereinafter referred to as LBKP), mechanical pulp such as GP, BCTMP, MP, and kenaf. Pulp obtained from non-wood raw materials such as, and papermaking pulp represented by pulp such as DIP. Based on this, polyolefin fibers such as polyethylene, polypropylene, ethylene / propylene copolymer, polystyrene, ethylene / vinyl acetate copolymer, halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride, 6-nylon, 66 -Polyamide fiber such as nylon, polyethylene succinate, polycaprolactone, polylactic acid, aliphatic polyester fiber such as polyhydroxybutyrate / valerate copolymer, vinylon fiber and the like may be mixed. If necessary, inorganic pigments such as talc, kaolin, calcined kaolin, calcium carbonate, white carbon, amorphous silica, diatomaceous earth, titanium oxide, activated clay, barium sulfate, organic pigments such as urea formalin resin, nylon powder, polyethylene powder, etc. As a filler, and can be prepared by conventional methods using acidic or neutral papermaking.

  Further, sizing agents represented by rosin-based sizing agents, alkenyl succinic anhydrides, alkyl ketene dimers, etc., starches such as oxidized starch, enzyme-modified starch, cation-modified starch, esterified starch and etherified starch, methylcellulose, ethylcellulose , Cellulose derivatives such as carboxymethyl cellulose, methoxy cellulose, hydroxy cellulose, fully saponified or partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyvinyl alcohols such as silicon-modified polyvinyl alcohol, polyacrylamide, polyvinyl pyrrolidone, acrylic acid amide / acrylic acid ester Copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid copolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride Polymer alkali salts, water-soluble polymers such as casein, polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate ester, polybutyl methacrylate, styrene / butadiene copolymer, vinyl chloride / vinyl acetate copolymer, styrene / A base paper to which an adhesive represented by latex such as butadiene / acrylic copolymer is internally added or coated can be used as appropriate.

  As the support, a smooth support having a smoothness defined by JIS-P8119 of 300 seconds or more is preferable from the viewpoint of dot reproducibility.

  In the case where a support mainly composed of pulp and having inkjet suitability is used, ink jet recording can be performed directly on the surface of the support opposite to the thermosensitive coloring layer.

  However, when ink jet recording is directly performed on a support mainly composed of pulp, if the ink permeability of the support is too high, the printing density may not be obtained or the ink may bleed along the fibers on the support surface. A phenomenon called a ring occurs. On the other hand, if the penetrability of the ink into the support is too low, when different colors are adjacent to each other, a phenomenon called bleeding occurs in which the inks are mixed and smeared at the boundary line. Therefore, in order to make the support have inkjet suitability, it is necessary to have a sizing degree that allows the ink to permeate the support appropriately.

In order to make the support suitable for inkjet, the sizing degree of the support is such that the 30 second Cobb water absorption measured with a 5% isopropyl alcohol aqueous solution is 10 to 50 g / m ² , preferably 14 to 25 g / m ^2. Control. When the 30-second Cobb water absorption measured with a 5% isopropyl alcohol aqueous solution is less than 10 g / m ² , the sizing degree of the support is too high and the feathering is good, but the bleeding deteriorates. On the other hand, when the 30-second Cobb water absorption measured with a 5% isopropyl alcohol aqueous solution exceeds 50 g / m ² , the bleeding is good, but the feathering deteriorates. The Cobb water absorption by 5% isopropyl alcohol is measured according to JIS P8140 except that 5% isopropyl alcohol aqueous solution is used instead of distilled water and the contact time with the test piece is 30 seconds.

  As a means for controlling the sizing degree of the support, the amount of the internally added size and the amount of ash are adjusted when making the support, and the surface of the support is a water-soluble binder such as oxidized starch or polyvinyl alcohol. The method of apply | coating by adjusting the application amount is mentioned. Styrene / acrylic acid copolymer, styrene / methacrylic acid copolymer, acrylonitrile / vinyl formal / acrylic acid ester copolymer, styrene / maleic anhydride together with water-soluble binders such as oxidized starch and polyvinyl alcohol A surface sizing agent such as a copolymer is also effective.

In addition, various additives can be added to the support used in the present invention for the purpose of improving ink jet suitability. The additive may be added internally to the paper support or may be treated with a tab size, size press, or the like. An example of the additive is a cationic resin, which is a monomer, oligomer, or polymer of a primary to tertiary amine or quaternary ammonium salt that dissociates and exhibits cationic properties when dissolved in water. Preferably, it is an oligomer or a polymer. Especially when the cationic resin is a compound mainly composed of dimethylamine / epichlorohydrin polycondensate, acrylamide / diallylamine copolymer, polyvinylamine copolymer, dicyandiamide, dimethyl / diallyl / ammonium chloride. Has been found to be obtained. Thus, when a cationic resin is used, the sizing degree of the paper support is not particularly restricted, but preferably has a 30 second Cobb water absorption of 10 to 50 g measured with a 5% isopropyl alcohol aqueous solution. / m ² .

  In addition, an ink receiving layer having ink jet aptitude (hereinafter, abbreviated as an ink receiving layer) may be provided on the support surface on which ink jet recording is performed, according to the purpose and necessity. Specific examples include a fine coat type ink receiving layer as disclosed in JP-A-7-290817, and a coat type ink reception as disclosed in JP-A-6-234268. Examples include layers. For purposes such as the formation of photographic images, an ink receiving layer can be formed using inorganic ultrafine particles such as vapor phase silica and fine particle alumina.

  The ink receiving layer in the present invention is mainly composed of a pigment and a binder.

  In the ink receiving layer used in the present invention, one or more known white pigments can be used. For example, light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic non Crystalline silica, colloidal silica, colloidal alumina, pseudoboehmite, aluminum hydroxide, alumina, lithopone, zeolite, hydrous halloysite, magnesium carbonate, magnesium hydroxide, white inorganic pigments, styrene plastic pigments, acrylic plastic pigments, polyethylene micro Examples thereof include organic pigments such as capsules, urea resins, and melamine resins. In the ink receiving layer of the present invention, the white pigment contained as a main component among the above pigments is any one of porous synthetic amorphous silica, colloidal silica, porous magnesium carbonate, and porous aluminum hydrate. In particular, porous synthetic amorphous silica having a large pore volume is preferable. Moreover, it is preferable that the average secondary particle diameter of porous synthetic amorphous silica is in the range of 0.1 μm to 20 μm.

  Binders contained in the ink receiving layer include polyvinyl alcohol, polyvinyl acetate, oxidized starch, etherified starch, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, casein, gelatin, soy protein, silyl-modified polyvinyl alcohol, anhydrous male Conjugated diene copolymer latex such as acid resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, polymer or copolymer of acrylic acid ester and methacrylic acid ester, polymer of acrylic acid and methacrylic acid Or acrylic polymer latex such as copolymer, vinyl polymer latex such as ethylene vinyl acetate copolymer, or functional group-modified polymer latex with functional group-containing monomers such as carboxyl groups of these various polymers , Mela Water-based adhesives such as thermosetting synthetic resins such as vinyl resins and urea resins, and synthetic resin adhesives such as polymethyl methacrylate, polyurethane resins, unsaturated polyester resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, alkyd resins, etc. And used in one or more kinds.

  The total amount of the binder can be appropriately adjusted according to the properties of the target ink-receiving layer, but is generally 5 to 60% by mass with respect to 100% by mass of the pigment.

  In addition, various additives can be added to the ink receiving layer in the present invention for the purpose of improving ink jet aptitude. In particular, as the additive, it is preferable to use a cationic resin as exemplified in the internal addition to the support or the size press. Furthermore, in the ink receiving layer, as other additives, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, foam suppressors, mold release agents, foaming agents, penetrants, colored dyes, colored pigments , Fluorescent whitening agents, ultraviolet absorbers, antioxidants, preservatives, antifungal agents, wet paper strength enhancers, dry paper strength enhancers, and the like can be appropriately blended.

When providing the ink-receiving layer in the present invention, the coating amount is preferably from ^{0.5g / m 2 ~30g / m 2} . When the coating amount is less than 0.5 g / m ² , the ink-jet suitability is inferior, and even if the coating amount is 30 g / m ² or more, the effect on the coating amount reaches its peak. Further, the Cobb water absorption of the ink receiving layer is preferably 10 to 50 g / m ² in 30 second Cobb water absorption measured with a 5% isopropyl alcohol aqueous solution.

  In the present invention, the ink receiving layer is formed by coating or impregnation by turning on various devices such as various blade coaters, roll coaters, air knife coaters, bar coaters, rod blade coaters, curtain coaters, short dwell coaters, and size presses. It can be used on a machine or off-machine. In addition, after coating or impregnation, it may be finished using a calendar such as a machine calendar, a TG calendar, a super calendar, or a soft calendar.

  The printer used in the present invention preferably has two recording units, an ink jet recording unit and a thermal recording unit. Both recording units may be ordinary single recording units. That is, the inkjet recording unit does not have to be particularly different from that of a commercially available inkjet printer, and the thermal recording unit is different from that of a thermal recording printer. However, it is desirable that the head of the thermal recording unit is upward or sideways, and it is further preferable that the thermal recording unit is positioned in front of the ink jet recording unit. When the thermal recording unit faces downward, it is not preferable because the recording paper needs to be reversed for ink jet recording for the above-mentioned reason. When there is an ink jet recording unit in front of the thermal recording unit, thermal recording is performed after the ink jet recording. For thermal recording, it is necessary to place a platen roll on the part where the head hits. Immediately after recording by inkjet, the platen roll and the thermal head nip may cause contamination of the platen roll with undried ink. is there. In addition, when the paper is swollen due to water-based ink, wrinkles or the like may occur. The recording head may be either a serial head or a line head for both the ink jet recording unit and the thermal recording unit, but is preferably a line head for high-speed recording.

  As described above, the ink jet recording unit of the printer used in the present invention may be similar to a commercially available ink jet printer. The recording head may be a serial head or a line head, but is preferably a line head for high-speed recording. Further, the ink to be used is not particularly limited. The water-based ink used in the present invention contains at least one of a water-soluble direct dye, a water-soluble acid dye, and a color pigment as a dye. In addition, a wetting agent, a dye-dissolving agent, a preservative, Contains glaze etc. Examples of water-soluble direct dyes include CI. Direct black, CI. Direct yellow, CI. Direct Blue, CI. Direct red and the like, and water-soluble acid dyes include CI. Acid Black, CI. Acid Yellow, CI. Acid Blue, CI. Although acid red etc. can be mentioned, it is not necessarily limited to these.

  Wetting agents and dye solubilizers include alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol and glycerin and derivatives thereof, nitrogen compounds such as formamide, dimethylacetamide and N-methyl-2-pyrrolidone, dimethyl sulfoxide, Sulfur compounds such as sulfolane are included.

  Among these, substances that induce color development of the thermosensitive coloring layer are also included. Therefore, if the support is a substance that easily permeates the wetting agent, dye dissolving agent, etc. in the ink, it can be used in the thermosensitive coloring layer. It may permeate to induce color development and cause a so-called fogging phenomenon. In addition, the wetting agent and dye solubilizing agent in the ink also contain a substance that induces decoloration of the color developing portion of the heat sensitive color developing layer, which may cause the disappearance of the image of the heat sensitive color developing layer. Therefore, as in the present invention, it is necessary to provide a protective layer and an intermediate layer so that the solvent such as the wetting agent and the dye dissolving agent does not penetrate into the thermosensitive coloring layer.

When the 30-second Cobb water absorption measured with a 5% isopropyl alcohol aqueous solution on the surface imparted with ink jet recording suitability is 10 g / m ² or more and 50 g / m ² or less, the penetration of the solvent can be substantially prevented. it can. Further, 2,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4′-iso is used as the electron-accepting compound in the thermosensitive coloring layer. By containing at least one selected from propoxydiphenylsulfone and containing an amino group-modified polyvinyl alcohol in the protective layer, the ink-jet ink resistance can be further improved.

  In order to achieve this object, there are various methods such as thickening the support, increasing the size of the support, and selecting the type and amount of the resin for the ink receiving layer (first aspect of the present invention). Further, since a blur is generated when a support such as a synthetic resin film is used so that the solvent does not permeate, the second aspect of the present invention is an intermediate that does not allow the solvent to permeate between the thermosensitive coloring layer and the support. Providing an intermediate layer and / or providing an intermediate layer between the ink receiving layer and the support. However, if an intermediate layer is provided between the ink receiving layer and the support, the absorbability of the ink-jet ink is often lowered, and there is a possibility that the ink-jet recorded image may be blurred. A double-sided recording medium in which an intermediate layer is provided between layers is preferable.

  The double-sided recording medium of the present invention can be used not only for high-speed simultaneous recording of ink-jet recording and thermal recording, but also for recording when using an ink-jet printer, a thermal printer, and each printer alone if necessary. It is. Even in such a case, since double-sided recording can be performed with one recording medium, there is an advantage that a large amount of information can be recorded on the double-sided recording medium of the present invention. In addition, an information recording material provided with, for example, a heat-sensitive color developing layer only on one side of a support that has been widely used in the past can function as an information recording material in the event of some trouble in the recording layer. Absent. On the other hand, as in the present invention, a double-sided recording medium having different recording layers on both sides of the support functions as an information recording material even if some trouble occurs in one of the recording layers. It is possible to collate two types of records as well as to obtain (double check of safety), so that not only can the reliability of the recorded information be improved, but it can also be extremely useful in preventing counterfeiting it can. In addition, color information can be recorded on the ink jet recording surface, and high-quality, high-impact information can be recorded.

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples. In addition,% and part shown below are mass% and mass part, respectively.

<Production of support>
A 1: 1 mixture of hardwood bleached kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP) was dispersed in water at a concentration of 4%, and the freeness was measured with a Canadian Standard Freeness Tester using a double disc refiner. Beat to 300ml. To this pulp slurry, 10% light calcium carbonate as a filler, 0.5% sulfuric acid band to pulp, 0.08% alkyl ketene dimer as a sizing agent, and 1.0% cationized starch to pulp, Diluted with water to give a 1% slurry. This slurry was made with a long paper machine so that the basis weight was 70 g / m ² . On the base paper, 30 seconds of Cobb water absorption measured with a 5% isopropyl alcohol aqueous solution in a size press solution consisting of 3 parts of oxidized starch, 0.2 part of a surface sizing agent which is a styrene / acrylic acid copolymer, and 96.8 parts of water. A size press treatment was performed so that the degree was 20 g / m ² to produce a support used for the double-sided recording medium of the present invention.

<Formation of thermosensitive coloring layer>
(Preparation of coating solution for thermosensitive coloring layer)
<Preparation of liquid A (electron-donating colorless dye)>
A dispersion having an average particle size of 0.8 μm was obtained with a ball mill using the following composition.
3-diethylamino-6-methyl-7-anilinofluorane 10 parts polyvinyl alcohol 2.5% solution (PVA-105)
(Saponification degree: 98.5 mol%, polymerization degree: 500, manufactured by Kuraray Co., Ltd.) 50 parts <Preparation of liquid B (electron-accepting compound)>
A dispersion having an average particle size of 0.8 μm was obtained with a ball mill using the following composition.
2,4′-dihydroxydiphenylsulfone 20 parts Polyvinyl alcohol 2.5% solution (PVA-105) 100 parts <Preparation of liquid C (sensitizer)>
A dispersion having an average particle size of 0.8 μm was obtained with a ball mill using the following composition.
2-Benzyloxynaphthalene 20 parts Polyvinyl alcohol 2.5% solution (PVA-105) 100 parts <D liquid (pigment) preparation>
A pigment dispersion having an average particle size of 2.0 μm was obtained with a sand mill using the following composition.
Calcium carbonate 40 parts Sodium polyacrylate 1 part Water 60 parts

  60 parts of the above liquid A, 120 parts of liquid B, 120 parts of liquid C, 101 parts of liquid D, 15 parts of 30% zinc stearate dispersion, 15 parts of paraffin wax (30% dispersion), dodecyl 4 parts of sodium benzenesulfonate (25%) was mixed to obtain a coating solution for a thermosensitive coloring layer.

<Preparation of coating solution for protective layer>
The following were dispersed with a sand mill to obtain a pigment dispersion having an average particle size of 2 μm.
Calcium carbonate 2 parts Sodium polyacrylate 0.1 part Water 8 parts Nonionic self-emulsion polymerized acrylic latex (trade name: Dicknal RT22, solid concentration 40%, manufactured by Dainippon Ink & Chemicals, Inc.) 30 parts And 20 parts of a 70% modified polyamine resin aqueous solution (PA-622 manufactured by Japan PMC), 2 parts of an epoxy-based crosslinking agent (solid content 20%), 60 parts of water, and the above pigment dispersion are further mixed. 2.5 parts of 0.15 μm diameter zinc stearate emulsified dispersion (Hydrin F115 manufactured by Chukyo Yushi Co., Ltd.) and 12.5 parts of 2% aqueous solution of 2-ethylhexyl sulfosuccinate soda salt are mixed to obtain a coating solution for protective layer It was.

<Preparation of coating solution for intermediate layer>
Fine hollow particle dispersion (copolymer based on vinylidene chloride and acrylonitrile) (solid content concentration 32%, average particle size 5 μm, hollow rate 92%) 30 parts styrene / butadiene copolymer latex (solid content concentration 47 %) 20 parts water 60 parts

(Production of double-sided recording medium)
On the support, the intermediate layer coating solution was applied and dried so that the weight after drying was 5 g / m ² to obtain an intermediate layer coated paper. The coating solution for the thermosensitive coloring layer is applied with an air knife so that the coating amount after drying is 4 g / m ² , dried and calendered, and then the protective layer coating solution is applied onto the thermosensitive coloring layer. Applying with an air knife so that the coating amount after drying is 2 g / m ² , drying and calendering, providing a thermosensitive coloring layer and a protective layer on one side of the support, and the other side being ink jet aptitude A double-sided recording medium of Example 1 having

  Example 2 was carried out in the same manner as in Example 1 except that 4,4′-dihydroxydiphenylsulfone was used instead of 2,4′-dihydroxydiphenylsulfone as the electron-accepting compound in the thermosensitive coloring layer. No. 2 double-sided recording medium.

  In Example 1, the same procedure as in Example 1 was performed except that bis (3-allyl-4-hydroxyphenyl) sulfone was used instead of 2,4′-dihydroxydiphenylsulfone as the electron-accepting compound in the thermosensitive coloring layer. Thus, a double-sided recording medium of Example 3 was obtained.

  In Example 1, the same procedure as in Example 1 was used except that 4-hydroxy-4'-isopropoxydiphenylsulfone was used instead of 2,4'-dihydroxydiphenylsulfone as the electron-accepting compound in the thermosensitive coloring layer. A double-sided recording medium of Example 4 was obtained.

The size press solution of Example 1 was changed to a size press solution consisting of 3 parts of oxidized starch, 3 parts of a cationic resin (polyvinylamine copolymer), and 94 parts of water, subjected to size press treatment, and each dried solid content was A double-sided recording medium of Example 5 was produced in the same manner as in Example 1 except that it was applied and dried so as to be 1.2 g / m ² and 0.8 g / m ² . The 30-second Cobb water absorption measured with the 5% isopropyl alcohol aqueous solution of Example 5 was 20 g / m ² .

In the production of the support of Example 1, sizing control by size press treatment is not performed, and the following ink receiving layer is provided on the support surface on which ink jet recording is performed. Thus, a double-sided recording medium of Example 6 was produced. That is, 100 parts of colloidal silica as an ink receiving layer composition and 10 parts of polyvinyl alcohol as an adhesive were prepared to a solid content concentration of 30%. Both surfaces of Example 6 were used in the same manner as in Example 1 except that the prepared ink-receiving layer coating liquid was applied and dried with an air knife coater so that the coating amount was 10.0 g / m ^2. A recording medium was manufactured.

In the double-sided recording medium of the present invention produced in Example 6, the following ink receiving layer was provided in place of the ink receiving layer used in Example 6, and the same as in Example 6 except that A double-sided recording medium was manufactured. That is, as the ink receiving layer composition, 100 parts of synthetic amorphous silica and 50 parts of polyvinyl alcohol were prepared to give a solid content concentration of 18%. Both surfaces of Example 7 were used in the same manner as in Example 6 except that the prepared ink-receiving layer coating liquid was applied and dried with an air knife coater so that the coating amount became 7.0 g / m ^2. A recording medium was manufactured.

In the double-sided recording medium of the present invention prepared in Example 7, the following ink receiving layer was provided instead of the ink receiving layer used in Example 7, and the same as in Example 7 was repeated. A double-sided recording medium was manufactured. That is, as an ink receiving layer composition, 100 parts of synthetic amorphous silica, 50 parts of polyvinyl alcohol, and 10 parts of a cationic fixing agent (Acurac 41: manufactured by Mitsui Cyanamid Co., Ltd.) were prepared and mixed to obtain a solid content concentration. 18%. Both surfaces of Example 8 were used in the same manner as Example 7 except that the prepared ink-receiving layer coating liquid was applied and dried with an air knife coater so that the coating amount became 7.0 g / m ^2. A recording medium was manufactured.

In the double-sided recording medium of the present invention produced in Example 8, in the production of the support, the basis weight of the support is 43 g / m ^2, and the following intermediate layer is provided between the thermosensitive coloring layer and the support. A double-sided recording medium of Example 9 was produced in the same manner as Example 8 except for the above. That is, as an intermediate layer composition, except that 100 parts of 10% polyvinyl alcohol and 30 parts of 20% silica (Mizukasil P527) were coated and dried with an air knife coater so that the coating amount was 3 g / m ² . In the same manner as in Example 8, the double-sided recording medium of Example 9 was produced.

In the double-sided recording medium of the present invention produced in Example 9, in the production of the support, the basis weight of the support is 43 g / m ² and the following intermediate layer is provided between the thermosensitive recording layer and the support. A double-sided recording medium of Example 10 was produced in the same manner as Example 9 except for the above. That is, as an intermediate layer composition, calcined kaolin (ANSILEX manufactured by Engelhard) 100 parts, 10% sodium hexametaphosphate 4 parts, 48% styrene-butadiene latex 40 parts, 20% phosphate esterified starch (MS-4600 manufactured by Japanese Foods) ) Was used to prepare a solid content concentration of 35%. Using the prepared intermediate layer coating solution, the double-sided recording medium of Example 10 was prepared in the same manner as in Example 9, except that the coating amount was 3 g / m ² by an air knife coater and dried. Manufactured.

  In Example 8, except that 2,4′-dihydroxydiphenyl sulfone was used instead of 2,4′-dihydroxydiphenyl sulfone as the electron accepting compound in the thermosensitive coloring layer, Example 2 was used. In the same manner as in Example 1, a double-sided recording medium of Example 11 was obtained.

A double-sided recording medium of Example 12 was produced in the same manner as Example 5 except that the size press treatment was not performed in the production of the support of Example 5. In addition, the 30 second Cobb water absorption measured with 5% isopropyl alcohol aqueous solution of the support is 55 g / m ² .

In the production of the support of Example 5, both sides of Example 13 were made in the same manner as Example 5 except that the addition amount of the alkyl ketene dimer as a sizing agent was 0.3% and no size press treatment was performed. A recording medium was manufactured. The 30-second Cobb water absorption measured with a 5% isopropyl alcohol aqueous solution of the support is 5 g / m ² .

(Comparative Example 1)
In Example 1, the double-sided recording medium of Comparative Example 1 was produced in the same manner as in Example 1 except that the water-soluble modified polyamine resin was removed from the binder of the protective layer coating solution.

(Comparative Example 2)
In Example 1, a double-sided recording medium of Comparative Example 2 was produced in the same manner as in Example 1 except that the self-emulsified acrylic latex was removed from the binder of the protective layer coating solution.

(Comparative Example 3)
A double-sided recording medium of Comparative Example 3 was obtained in the same manner as in Example 1 except that the protective layer of Example 1 was not applied.

  Table 1 shows the evaluation results for the double-sided recording media obtained in Examples 1 to 13 and Comparative Examples 1 to 3. In the table, the suitability for inkjet, the background fogging of the thermosensitive coloring layer, the image storage stability, and the inkjet ink resistance were evaluated as follows.

<Inkjet aptitude evaluation>
(1) Feathering A black ink-jet printer (BJC-420J: manufactured by Canon Inc.) is used on the surface of the double-sided recording medium prepared in Examples 1 to 13 and Comparative Examples 1 to 3 without a thermosensitive coloring layer. Characters and ruled lines composed of a single ink color were printed, and the bleeding of the characters and ruled lines was visually evaluated according to the following criteria. The results are summarized in Table 1. Evaluation is a five-level evaluation, and if it is 3 points or more, it is a practical level.

Evaluation criteria:
5: Extremely good.
4: Almost no ink bleeding along the fiber.
3: There are spots of ink along the fibers, but there is no problem.
2: Ink bleeding along the fibers along the characters and ruled lines is observed, and the print quality is poor.
1: Ink bleeding along the fibers along the characters and ruled lines is seen everywhere, and the characters are poorly identified.

(2) Bleeding On the surface of the double-sided recording medium prepared in Examples 1 to 13 and Comparative Examples 1 to 3 on which the heat-sensitive color-developing layer is not provided, an inkjet printer (BJC-420J: manufactured by Canon Inc.) is used. Cyan, magenta, and yellow solid print sections are printed on each. At this time, the solid print portions of the respective colors are arranged adjacent to other solid print portions. After printing, the degree of bleeding of the boundary line between adjacent colors was visually evaluated according to the following criteria. The results are summarized in Table 1. The evaluation is in 5 stages, and if it is 3 points or more, it is a practical level.

Evaluation criteria:
5: Extremely good.
4: There is almost no blur between colors at the boundary.
3: There are some color blurs at the boundary, but there is no problem.
2: The blur between colors at the boundary line can be clearly confirmed, and the boundary line is difficult to understand.
1: The blurring of the colors at the boundary line is severe, the colors of the boundary line part are mixed, and the color of the boundary line part is discolored.

<Inkjet ink resistance>
(3) Evaluation of fogging of thermosensitive coloring layer 1 (ink penetration fogging)
Using a Seiko Epson ink jet printer, PM-700C, 200% density printing was performed at a recording density of 720 dpi, and after standing in an environment of 20 ° C. and 65% RH for 10 days, the occurrence of fogging of the thermosensitive coloring layer was visually observed. evaluated. As a result, the case where fog was not recognized at all was ranked as A, the case where slight fog was observed but at a level where there was no problem in practical use was ranked as B, and the case where fog was strong and could not be used practically was ranked as C.
(4) Evaluation of fog of heat-sensitive color developing layer 2 (ink transfer fog)
Immediately after 200% density printing was performed at a recording density of 720 dpi using a Seiko Epson inkjet printer, PM-700C, two recording media were stacked so that the inkjet recording layer and the thermosensitive coloring layer were in contact with each other, 10 g / cm The plate was left in an environment of 20 ° C. and 65% RH for 10 days while applying a pressure of ² , and the fogging state of the thermosensitive coloring layer was visually evaluated. As a result, the case where fog was not recognized at all was ranked as A, the case where slight fog was observed but at a level where there was no problem in practical use was ranked as B, and the case where fog was strong and could not be used practically was ranked as C.

(5) Evaluation 1 of decoloring of thermal recording image (ink penetrating decoloring)
After forming a thermal recording image by the above method, 200% density printing was performed at a recording density of 720 dpi using an Seiko Epson ink jet printer, PM-700C, and left in an environment of 20 ° C. and 65% RH for 10 days. The state of occurrence of decoloring of the thermal recording image was visually evaluated. As a result, the case where no erasing was recognized was ranked as A, the case where slight erasing was recognized but a level where there was no problem in practical use was ranked as B, and the case where erasing was strong and unbearable was ranked as C.
(6) Evaluation 2 of decoloring of thermal recording image (ink transfer decoloring)
After the thermal recording image was formed by the above method, immediately after 200% density printing was performed at a recording density of 720 dpi using a Seiko Epson inkjet printer, PM-700C, two recording media and thermal coloring were formed on the two recording media. The layers were placed in contact with each other and left to stand in an environment of 20 ° C. and 65% RH for 10 days while applying a pressure of 10 g / cm ² , and the state of occurrence of decoloration of the thermal recording image was visually evaluated. As a result, the case where no erasing was recognized was ranked as A, the case where slight erasing was recognized but a level where there was no problem in practical use was ranked as B, and the case where erasing was strong and unbearable was ranked as C.

<Evaluation>
The double-sided recording media produced in Examples 1 to 13 have no coloration or fogging on the heat-sensitive recording surface even after ink-jet printing on the surface not provided with the heat-sensitive coloring layer, and the information on the heat-sensitive recording surface can be identified. Met. Among them, the double-sided recording media of Examples 5 to 8 and 13 were good, and Example 8 containing a cationic fixing agent in the ink receiving layer was particularly good. In Examples 1 to 4 and Examples 9 to 12, coloring and fogging occurred slightly on the background of the color image of the heat-sensitive recording layer, but there was no problem in identifying the information on the front and back. On the other hand, in Comparative Examples 1 and 2, since only one of the acrylic resin and water-soluble modified polyamine resin self-emulsified and polymerized in the protective layer was used, coloring and fogging occurred on the thermal recording surface. There was a problem in identifying the information on the front and back. Further, in Comparative Example 3, when a double-sided recording medium is used after recording because the protective layer is not provided, the ink-jet ink is transferred to the heat-sensitive color developing layer and becomes dirty, and the double-sided recording medium is overlapped. There was a problem identifying the information.

Claims (8)

  Double-sided recording in which a protective layer is provided on one side of a support mainly composed of pulp and a heat-sensitive color-developing layer containing an electron-donating colorless dye and an electron-accepting compound, and the other side is provided with inkjet suitability A double-sided recording medium comprising an acrylic resin self-emulsified and a water-soluble modified polyamine resin in a protective layer.   The electron-accepting compound is 2,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone. The double-sided recording medium according to claim 1, wherein the double-sided recording medium is at least one selected. 3. The double-sided recording medium according to claim 1, wherein the surface having ink jet aptitude has a 30-second Cobb water absorption measured with a 5% isopropyl alcohol aqueous solution of 10 g / m ² or more and 50 g / m ² or less. .   The double-sided recording medium according to any one of claims 1 to 3, wherein the surface having ink jet recording suitability contains a cationic resin.   3. The double-sided recording medium according to claim 1, wherein an ink receiving layer having ink jet suitability is provided on the other surface of the support.   The double-sided recording medium according to claim 5, wherein the ink receiving layer contains a cationic resin.   7. The double-sided recording medium according to claim 1, wherein one or more intermediate layers are provided between the support and the thermosensitive coloring layer.   8. The double-sided recording medium according to claim 7, wherein at least one of the intermediate layers is mainly composed of plastic spherical fine hollow particles.