JPH08169174A - Ink-jet recording sheet - Google Patents

Abstract

PURPOSE: To improve printing density, ink fixing, cockling and curling properties by a method in which the babe paper of an ink-jet recording sheet which contains wood pulp as a main component is impregnated with a specified amount of a specified ionizing radiation setting compound, and then the compound is cured by being irradiated with an ionizing radiation. CONSTITUTION: In an ink-jet recording sheet in which an ink receiving layer is formed at least on one side of a support, the support is formed by a method in which base paper containing wood pulp as a main component is impregnated with a hydrophilic ionizing radiation setting compound having two or more ethylenic double bonds in a molecule in an amount of 5-80% of the basis weight of the base paper, and the compound is cured by being irradiated with an ionizing radiation. The ionizing radiation setting compound contains an ethylene oxide unit in a molecule. The support is treated with a radical polymerization inhibitor. In this way, printing density, ink fixing, and hue are improved, and cockling and curling properties are improved irrespective of an ink placing amount and ink absorption of the ink receiving layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording sheet, more specifically, printing density,
The present invention relates to an inkjet recording sheet which is excellent in ink fixing property and hue, and has improved cockling property and curl property regardless of the amount of ejected ink and the ink absorption property of the ink receiving layer, which is suitable for a high-definition inkjet recording system. is there.

[0002]

2. Description of the Related Art Inkjet recording systems use various types of operating principles typified by a deflection system, a cavity system, a thermojet system, a bubble jet system, a thermal inkjet system, a slit jet system, and a spark jet system. Although droplets are ejected and deposited on an inkjet recording sheet such as paper to record images and characters, high speed, low noise, easy multicoloring, great flexibility in recording patterns, development- It has the advantage that it does not require fixing, and is rapidly spreading in various applications as a recording device for various figures including Kanji and color images.

As the ink jet recording sheet used in this ink jet recording system, an ink jet recording apparatus, a dye structure and an ink composition can be used so that general paper such as high quality paper or coated paper used for ordinary printing and writing can be used. The focus has been on areas such as surfaces. However, with the improvement in the performance of the inkjet recording apparatus such as high speed, high definition or full color, the inkjet recording sheet is required to have higher characteristics. That is, as an inkjet recording sheet,
The density of print dots is high, the color tone is bright and vivid, the absorption of ink is fast, the ink does not run or bleed even when the print dots overlap, and the horizontal spreading of the print dots is more than necessary. It was necessary to satisfy various requirements such as not becoming large, the shape of the ink dot being close to a perfect circle, the periphery being smooth and unblurred, the whiteness being high, and the contrast with the ink dot being large.

Along with the high definition of the ink jet recording apparatus, the amount of ejected ink per unit area has greatly increased. Therefore, among the above-mentioned requirements, sufficient ink absorbency and ink fixability are essential. There is a strong demand for an inkjet recording sheet that is excellent in so-called cockling and curling properties, that is, the printed portion of the inkjet recording sheet swells and undulates due to absorption of ink in order not to deteriorate the image quality.

As a method of obtaining excellent ink absorption,
Many proposals have been made in the past, for example, using synthetic amorphous silica or a salt thereof or a mixture thereof as an inorganic pigment in an ink receiving layer provided on a support (JP-A-57-157786). ) Or containing a porous cation-hydrated aluminum oxide (JP-A-60-232990). Among these, among them, JP-A-60-204390 and JP-A-60-204390 are particularly preferable. 2-198889, etc.,
A recording sheet containing a synthetic amorphous silica having a large specific surface area by the BET method or a cationic hydrated aluminum oxide which is a cationic colloidal particle has advantages of high printing density and excellent ink absorbability. In order to improve the ink absorbability by such an ink receiving layer and obtain a print dot having a higher print dot density and ink bleeding, for example, JP-A Nos. 55-51583 and 56-56.
No. 157, it is proposed to add non-colloidal silica powder. Also, for example, Japanese Patent Laid-Open No. 55-1441
No. 72, etc., paying attention to the fact that the color property and the sharpness are distribution states of the dye in the ink in the ink receiving layer,
Proposals have also been made to use specific agents that adsorb dye components.

[0006] The cockling property and the curl property tend to be improved by coating a large amount of the ink receiving layer excellent in the ink absorbing property as described above, however, however, the ink receiving layer having such an ink absorbing property is high. The layer needs to have many voids in the ink receiving layer in order to absorb and retain the ink, so that the incident light to the ink receiving layer is scattered and becomes opaque because the transmission is blocked, and the layer penetrates into the voids. Since it is difficult for light to reach the ink, there is a problem that the image becomes white and the print density and color reproducibility are lowered. Therefore, it is difficult to simultaneously improve the ink jet aptitude such as the print density and the cockling property and the curl property only by coating a large amount of the ink receiving layer.

Further, as a market need, there is a demand for an ink jet recording sheet which is more like plain paper and is compatible with high definition, that is, a fine coating type ink jet recording sheet. There was a need to obtain an inkjet recording sheet with improved cockling and curl regardless of ink absorbency.

[0008]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide excellent print density, ink fixability and hue, and to improve cockling and curling properties regardless of the amount of ejected ink and the ink absorbability of the ink receiving layer. It is an object of the present invention to provide an inkjet recording sheet which is improved and suitable for a high-definition inkjet recording system.

[0009]

Means for Solving the Problems As a result of intensive studies made by the present inventors on the above-mentioned problems in ink jet recording sheets, as a result, it was found that the base paper containing wood pulp as a main component of ink jet recording sheets has a specific ionizing radiation curability. When a specific amount of the compound is impregnated and cured by irradiation with ionizing radiation, the resin is excellent in print density and ink fixability without deteriorating the ink absorbency, and a resin that is strongly crosslinked in three dimensions is used as a resin. It was found that the cockling property and the curling property due to the moisture absorption of the wood pulp can be improved by filling the voids.

It has also been found that ink fixability can be further improved by incorporating a cationic compound into such a support.

However, such a base paper containing wood pulp as a main component and various additives is lightly colored by unreacted radicals remaining in the ionizing radiation-curable compound cured by irradiation with ionizing radiation. In some cases, it may be colored in yellow, which may affect the color reproducibility of the image. This could be improved by irradiating with ionizing radiation to cure the ionizing radiation-curable compound and then treating with a radical polymerization inhibitor.

That is, in an ink jet recording sheet in which an ink receiving layer is provided on at least one surface of a support, the support contains a hydrophilic ionizing radiation curing material containing two or more ethylenic double bonds in one molecule. The inkjet recording sheet is characterized by being impregnated with a functional compound in an amount of 5 to 80% of the basis weight of a base paper containing wood pulp as a main component, and then being cured by irradiation with ionizing radiation.

Furthermore, the ink jet recording sheet is characterized in that the ionizing radiation-curable compound contains ethylene oxide in the molecule.

An ink jet recording sheet characterized in that the support contains a cationic compound.

An ink jet recording sheet characterized in that the support is treated with a radical polymerization inhibitor.

The present invention will be described in detail below. The ink jet recording sheet of the present invention is a coat type or slightly coated type ink jet recording sheet, which is preferably used in an ink jet recording apparatus for obtaining a high-definition image, in order to maintain a plain paper-like texture. Using a base paper containing wood pulp as a main component, further, in order to improve the print density, ink fixing property, cockling property, and curl property, a specific ionizing radiation-curable compound is impregnated and cured as a support. To do.

The support in the ink jet recording sheet of the present invention includes chemical pulp such as LBKP and NBKP, GP, PGW, RMP, TMP, CTMP, CM.
Mechanical pulp such as P and CGP, wood pulp such as waste paper pulp such as DIP, and conventionally known pigments as main components, and binders and sizing agents, fixing agents, yield improving agents, cationizing agents, paper strengthening agents, etc. A base paper produced by mixing various additives with one or more kinds and using various devices such as a Fourdrinier paper machine, a cylinder paper machine, and a twin wire paper machine, and a base paper, and a size press using starch, polyvinyl alcohol, etc. For base paper with anchor coat layer or coated paper such as art paper, coat paper, cast coat paper, etc.
It is impregnated with an ionizing radiation-curable compound which contains two or more ethylenic double bonds in the molecule and is hydrophilic. Here, examples of the ethylenic double bond include a vinyl group, an acryloyl group, a methacryloyl group, an alicyclic epoxy group, and the like. An unsaturated polyester having such a functional group at a terminal or a side chain, a modified unsaturated Polyesters, acrylic polymers, acrylic oligomers, acrylic monomers, methacrylic polymers, methacrylic oligomers, methacrylic monomers, polymers having vinyl unsaturated bonds, oligomers and monomers, epoxy compounds, etc. are ionizing radiation curable in the present invention. The compound can be used, but a compound having an acryloyl group is particularly preferable because it has excellent ionizing radiation curability.

In order for the ionizing radiation-curable compound having the above structure to have hydrophilicity, a hydroxyl group, a carboxyl group, a secondary amine, a tertiary amine, a quaternary ammonium salt group or the like is included in the molecule. It is necessary to contain a hydrophilic unit such as a polar group, ethylene oxide, diethylene oxide, morpholine or pyrrolidone.
Here, when the ionizing radiation-curable resin compound is monofunctional, it is difficult for the ionizing radiation-curable compound to crosslink, and thus the cockling property of the inkjet recording sheet,
The curl cannot be improved sufficiently. If the ionizing radiation-curable compound is not hydrophilic, the ink absorbability will be significantly reduced, and ink overflow and bleeding will occur.

As such an ionizing radiation curable compound, a commercially available compound can be preferably used. Hereinafter, typical commercially available ionizing radiation-curable compounds that correspond to the above items will be exemplified, but the present invention is not limited thereto.

Kayarad PEG400DA, Kayarad R-167, PET-30, Sartomer SR-230,
Sartomer SR-268, Sartomer SR-344, Sartomer SR-444 (above, Nippon Kayaku, Kayarad and Sartomer series), NK ester A-200,
NK ester A-400, NK ester A-600, N
K ester A-TMM-3, NK ester A-TMM-
3L (above, Shin Nakamura Chemical, NK ester series),
Aronix M-240, Aronix M-245, Aronix M-205, Aronix M-210 (above, Toa Gosei Aronix series), 3EG-A, 4
EG-A, 9EG-A, BP-4EA, PE-3A (above, Kyoeisha Oil and Fat Chemicals, Light acrylate series), PE-200, PE-300, PE-400, E
P-22, BPE4, TMP-3, PET-3, C-1
615, C-1615M (above, Dai-ichi Kogyo Seiyaku, New Frontier series)

Among the hydrophilic ionizing radiation-curable compounds as described above, the compound containing an ethylene oxide segment in the molecule improves cockling property and curl property of the ink jet recording sheet, and further has good ink absorbability. Is particularly preferred because A plurality of ethylene oxide segments may be continuous segments, or other segments may be sandwiched therebetween.

Further, for the purpose of adjusting the curability of the above-mentioned ionizing radiation-curable compound and stabilizing the ink absorbability, monofunctional hydrophilic ionization is carried out, if necessary, within the range not impairing the present invention. A radiation-curable compound can also be impregnated together. As the monofunctional hydrophilic ionizing radiation curing, commercially available products can be preferably used, for example,
N, N-dimethylacrylamide, acryloylmorpholine, N, N-dimethylaminopropylacrylamide, N, N-dimethylaminoethyl acrylate, dimethylaminoethyl acrylate methyl chloride quaternary salt, N,
N-Dimethylaminopropylacrylamide Methyl chloride quaternary salt (above, Kojin), Kayarad R-128H, Kayarad R-564 (above, Nippon Kayaku, Kayarad series), Aronix M-101, Aronix M-
102, Aronix M-114, Aronix M-15
0, Aronix M-154, Aronix M-530
0, Aronix M-5400, Aronix M-55
00, Aronix M-5600, Aronix M-5
700 (above, Toagosei, Aronix series),
NK ester AMP-10G, NK ester AMP-2
0G, NK ester AMP-60G, NK ester AM
P-90G (above, Shin Nakamura Chemical Co., Ltd. NK ester series) etc. can be mentioned.

When impregnated with the above-mentioned ionizing radiation-curable compound, a fluorescent whitening agent, an ultraviolet absorber, an antioxidant, a light stabilizer, a radical polymerization initiator, within the range that does not impair the effects of the present invention. Agents, surfactants, lubricants, cationic dye fixing agents, thickeners, fluidity improvers, defoamers, foam suppressants, foaming agents,
It is also possible to add various additives such as a penetrant, a coloring dye, a coloring pigment, an antiseptic agent, an antifungal agent, a water resistance agent, a wet paper strength enhancer, and a dry paper strength enhancer. Here, the fluorescent whitening agent to be added in combination with the ionizing radiation-curable compound as described above is not particularly limited, but a radiation brightening agent containing a thiophene skeleton excellent in radiation resistance, weather resistance and the like is used. Particularly preferred.

The ionizing radiation for curing the ionizing radiation-curable compound in the gloss developing layer of the ink jet recording sheet of the present invention is generally ultraviolet rays, α rays, β rays, γ.
Rays, X-rays, electron rays, etc., but α rays, β rays, γ
Since X-rays or X-rays are accompanied by a problem of danger to the human body, ultraviolet rays and electron beams, which are easy to handle and widely used industrially, are effective.

In the present invention, when an electron beam is used,
The irradiation electron dose is preferably in the range of about 0.1 to 10 Mrad. Here, if it is less than 0.1 Mrad, sufficient curing effect cannot be obtained and curing is insufficient, and if it exceeds 10 Mrad, the support is deteriorated, which is not preferable. As an electron beam irradiation method, a scanning method, a curtain beam method, or the like can be used, and the electron beam acceleration voltage is preferably about 100 to 300 KV.

In the irradiation of electron beams, if the oxygen concentration in the atmosphere is high, the curing of the ionizing radiation-curable compound is hindered, so replacement with an inert gas such as nitrogen, helium or carbon dioxide is carried out, and the oxygen concentration is 600 ppm or less. In general, it is preferable to irradiate in an atmosphere in which the amount is suppressed to 400 ppm or less.

When ultraviolet rays are used in the present invention, a sensitizer must be incorporated in the adhesive layer. Specific examples thereof include acetophenones such as di- or trichloroacetophenone and benzophenone. , Michler's ketone, benzyl, benzoin, benzoin alkyl ether, benzyl dimethyl ketal, tetramethyl thiuram monosulfide, thioxanthones, azo compounds, etc., and the polymerization reaction type of radiation curable resin, stability, and compatibility with ionizing radiation irradiation equipment It is selected from the viewpoint of sex. The amount of the sensitizer used is usually about 1 to 5% by weight based on the ionizing radiation-curable compound. In addition, a storage stabilizer such as hydroquinone may be used in combination with the sensitizer. As the light source, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a xenon lamp, a tungsten lamp or the like is used.

The amount of the ionizing radiation-curable compound impregnated into the support in the ink jet recording sheet of the present invention is 5 to 80% of the basis weight of the base paper, and more preferably 20 to 7.
It is 0%. Here, if the amount of the ionizing radiation-curable compound impregnated is less than 5% of the basis weight of the base paper, the cockling property and curl property of the inkjet recording sheet cannot be sufficiently improved. Further, when the impregnation amount exceeds 80%, not only the plain paper-like texture is offset, but even if the hydrophilic ionizing radiation-curable compound is excellent in ink absorption, the voids between the wood pulps are Since the amount is too small, the ink absorbency is lowered.

The method for impregnating the support in the ink jet recording sheet of the present invention with the ionizing radiation-curable compound is to dissolve the ionizing radiation-curable compound in water or an organic solvent, or dilute the ionizing radiation-curable compound. In the case of a hydrophilic monomer or oligomer, it can be coated and impregnated using a conventionally known coating method without a solvent.
Here, when a solvent is used when impregnating the ionizing radiation-curable compound, the solvent is dried by a drying device such as a hot air dryer or an infrared dryer, and then the compound is irradiated with ionizing radiation. The solvent can be dried using the drying device after curing or after curing. As the coating method, for example, a blade method, an air doctor method,
Examples thereof include a squeeze system, an air knife system, a reverse roll system, a gravure roll and a transfer roll system, a bar system, a curtain system, a short dwell system, a size press system and a spray system.
Further, the support after curing the ionizing radiation curable compound,
It can be finished using a calendar such as a machine calendar, a TG calendar, a super calendar, and a soft calendar.

The basis weight of the support in the ink jet recording sheet of the present invention is usually 40 to 300 g / m ² , but is not particularly limited.

The support obtained by curing the ionizing radiation-curable compound impregnated with the ionizing radiation as described above is further treated with a radical polymerization inhibitor to surely prevent the coloration of pale yellow over time. be able to. This is presumably because unreacted radical species trapped in the ionizing radiation-curable compound cured by ionizing radiation are inactivated by the radical polymerization inhibitor. Such radical polymerization inhibitors include dichlorobenzoquinones, trinitrobenzenes, nitrosobenzenes, butylcatechols, picric acids, nitrobenzoic acids, oxygen and active oxygen, cupric chloride, ferric chloride, halogenated compounds. Cobalt, diphenylpicrin hydrazyl, tetraethylphenylenediamine,
Generally known radical polymerization inhibitors such as chloranil and iodine can be used. These radical polymerization inhibitors may be used alone or in the form of a mixture of two or more thereof. For example, conventionally known air knife coaters, curtain coaters, die coaters, blade coaters, gate roll coaters, bar coaters, rod coaters, It can be coated on the support by various devices such as a roll coater, a bill blade coater, a short dwell blade coater, a size press and a sprayer.

By adding a cationic compound to the support in the ink jet recording sheet of the present invention,
Further, the ink fixability can be improved. The cationic compound according to the present invention means a compound that dissociates into a cation in an aqueous medium, and a typical cationic group is 1
Examples include secondary, secondary, tertiary amino groups, and quaternary ammonium salts. Any kind of such a cationic compound can be applied, and the kind thereof is not particularly limited, but the cationic compound applied to the support has a number average molecular weight of 100,000 or less. Must be selected. When the molecular weight of the cationic compound exceeds 100,000, the film formed after drying lowers the ink absorption capacity of the support, which causes ink overflow.

The cationic compound applied to the support may be any of a monomer, an oligomer and a polymer. Examples of the polymer include polyalkylene polyamide; polyalkylene polyurea; polyamide polyurea; polyaminoepoxy resin; or Reaction products of these with aldehydes and reaction products with alkylating agents; ring-opening polymerization products of ethyleneimine; homopolymers of cationic vinyl polymers or copolymers with other polymerizable monomers; N-vinylamides Monomers of monomers or copolymers with other polymerizable monomers; Mannich reaction products obtained by reacting a polymer having active hydrogen with ammonia, primary amine, secondary amine and formamide; polymer having active hydrogen and cation Reaction products with agents; polymers with active hydrogen and ammonia, amine S, reaction product of epihalohydrin;
Examples include chitosan obtained by hydrolyzing chitin; a copolymer obtained by reacting a polymer having active hydrogen and any of the above polymers with a crosslinking agent such as aldehyde, epihalohydrin and polyisocyanate. Further, a cation-modified ionizing radiation-curable compound is radically polymerized with the above-mentioned ionizing radiation-curable compound, which is a more preferable form.

The cationic compound contained in the support is coated or impregnated on the support or the base paper. By distributing the compound in the depth direction of the support, the effect of the present invention can be more surely obtained. Therefore, the compound is preferably impregnated, and may be impregnated with the above ionizing radiation-curable compound at the same time.

The amount of the cationic compound coated or impregnated on the base paper or the support is preferably determined based on the cationic charge amount per unit area of the support. Here, the cation charge amount means the cation charge amount per unit weight [meq./g] of the compound measured by colloid titration and the content per unit area [g / m ² ] of the compound. Is the product [meq./m ² ].

In the ink jet recording sheet of the present invention, the cation charge amount per unit area is 0.8 meq./m ^2.
As described above, it is preferable to coat or impregnate the support or the base paper so that the amount becomes 1.0 meq./m ² or more.

[Ink Receiving Layer] As the ink receiving layer of the ink jet recording sheet of the present invention, any conventionally known ink receiving layer can be preferably used, however, for example, JP-A-60-224578. Rather than an ink-receiving layer consisting of only a water-soluble resin as proposed in JP-A-60-234879 or containing water-soluble resin as a main component, for example, JP-A-60-204390. An ink receiving layer mainly composed of an inorganic pigment having a large specific surface area by the BET method, as proposed in Japanese Patent Laid-Open Publication No. Hei 2-198889, etc., has excellent ink absorbency, sharpness of image, color reproducibility and the like. It is preferable from the point.

The ink receiving layer mainly containing an inorganic pigment, which is more preferable as the ink receiving layer of the ink jet recording sheet of the present invention, will be specifically shown below. Here, the inorganic pigment, the specific surface area by the BET method is not less 100 m ² / g or more, further preferably inorganic pigments 100~700m ² / g. By using an inorganic pigment having such a specific surface area, high printing density and excellent ink absorbency can be exhibited. BET specific surface area of inorganic pigment is 100
If it is less than m ² / g, sufficient print density and ink absorbency cannot be obtained.

As such an inorganic pigment, one or more conventionally known white pigments may be used alone or in combination, and examples thereof include light calcium carbonate, heavy calcium carbonate, kaolin, talc and calcium sulfate. , Barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate,
Satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, colloidal alumina, pseudo-boehmite,
Aluminum hydroxide, alumina, lithopone, zeolite, hydrohaloysite, magnesium carbonate, magnesium hydroxide and the like can be mentioned.

Among the above-mentioned inorganic pigments, it is particularly preferable to use synthetic amorphous silica for the ink jet recording sheet of the present invention, and an ink jet recording sheet excellent in print density, ink absorbability, sharpness of printed images, etc. is obtained. Obtainable. Such synthetic amorphous silica is
For example, JP-A-57-157786 and JP-A-61-1.
No. 41584, No. 61-230979, No. 6
A _two- dimensional structure of SiO ₂ was formed by gelation of silicic acid as described in JP-A-2-292476.
It is microporous and irregularly shaped fine particles, and as a typical physical property value range, it has an average particle diameter of about 10 nm to 20 μm, a Hunter whiteness of 90 or more, and a pore diameter of about 10 to 2000 angstrom.

As such synthetic amorphous silica, commercially available products can be preferably used. For example, Mizukasil P-
526, Mizukasil P-801, Mizukasil NP-8,
Mizukasil P-802, Mizukasil P-802Y, Mizukasil C-212, Mizukasil P-73, Mizukasil P
-78A, Mizukasil P-78F, Mizukasil P-8
7, Mizukasil P-705, Mizukasil P-707, Mizukasil P-707D, Mizukasil P-709, Mizukasil C-402, Mizukasil C-484 (manufactured by Mizusawa Chemical Co., Ltd.), Tokusil U, Tokusil UR, Tokusil G
U, Tokuseal AL-1, Tokuseal GU-N, Tokuseal N, Tokuseal NR, Tokuseal PR, Sorex, Fineseal E-50, Fineseal T-3
2, fine seal X-37, fine seal X-7
0, Fineseal RX-70 Fineseal A, Fineseal B (above, manufactured by Tokuyama Soda), Carplex FPS-101, Carplex CS-7, Carplex 80, Carplex XR, Carplex 67
(Above, manufactured by Shionogi Pharmaceutical Co., Ltd.), Syloid 63, Syloid 65, Syroid 66, Syroid 77, Syroid 7
4, Syloid 79, Syloid 404, Syloid 6
20, Thyroid 800, Thyroid 150, Thyroid 244, Thyroid 266 (above, manufactured by Fuji Silysia Chemical Ltd.) and the like.

Cationic colloid particles can be added to the ink receiving layer in the present invention in combination with the above-mentioned inorganic pigment. Here, the cationic colloidal particles are the same as the cationic colloidal particles constituting the gloss developing layer, and reliably fix a trace amount of the dye that has not penetrated into the ink receiving layer but is fixed in the gloss developing layer. Can be made.

In the ink receiving layer of the ink jet recording sheet of the present invention, a binder resin may be used if necessary for the purpose of firmly fixing the above-mentioned inorganic pigment on the support. Examples of binder resins that can be suitably used include polyvinyl alcohol, silanol-modified polyvinyl alcohol, vinyl acetate, oxidized starch, etherified starch, carboxymethyl cellulose, cellulose derivatives such as hydroxyethyl cellulose, casein, gelatin, soybean protein, and silyl modified. Polyvinyl alcohol, etc .; maleic anhydride resin, styrene-
Conjugated diene copolymer latex such as butadiene copolymer and methyl methacrylate-butadiene copolymer; polymer or copolymer of acrylic acid ester and methacrylic acid ester, polymer or copolymer of acrylic acid and methacrylic acid, etc. Acrylic polymer latex; vinyl polymer latex such as ethylene-vinyl acetate copolymer; or functional group-modified polymer latex with a functional group-containing monomer such as carboxyl group of these various polymers; melamine resin, urea Water-based adhesive such as thermosetting synthetic resin such as resin; polymethylmethacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer,
One or more synthetic resin adhesives such as polyvinyl butyral and alkyd resin may be used alone or in combination. In addition, the use of known natural or synthetic resin binders alone or in combination is not particularly limited.

Here, in the ink receiving layer of the present invention,
The compounding amount of the binder resin with respect to 100 solid parts by weight of the inorganic pigment as described above is 3 to 70 solid parts by weight, more preferably 5 to 50 solid parts by weight, and if it is less than 3 solid parts by weight, the coating strength of the ink receiving layer is low. Is insufficient, and if it exceeds 70 parts by weight, the ink absorption capacity is insufficient depending on the type of ink jet recording apparatus, which is not preferable because the ink overflows.

Further, as other additives, a cationic dye fixing agent, a pigment dispersant, a thickener, a fluidity improver, a defoaming agent, a foam suppressor, a release agent, a foaming agent, a penetrating agent, a coloring dye. A color pigment, a fluorescent whitening agent, an ultraviolet absorber, a preservative, an antifungal agent, a water resistance agent, a wet paper strength enhancer, a dry paper strength enhancer, an antioxidant and the like can be appropriately added.

In particular, when a cationic dye fixing agent consisting of a secondary amine, a tertiary amine or a quaternary ammonium salt which forms an insoluble salt with the sulfone group, carboxyl group, amino group or the like of the dye in the ink is added, Since the dye is satisfactorily captured by the receiving layer, it is possible to improve the color property and to prevent the ink from flowing or bleeding due to the dropping of water or the absorption of moisture.

As a method for providing the ink receiving layer of the ink jet recording sheet of the present invention on the support, a hydrophilic organic solvent such as water or alcohol, or a mixed solvent thereof is used, for example, a conventionally known air knife coater. It can be coated on the support by various devices such as a curtain coater, die coater, blade coater, gate roll coater, bar coater, rod coater, roll coater, bill blade coater, short dwell blade coater and size press. Further, after coating the ink receiving layer, a smoothing treatment can be carried out using a calendar device such as a machine calendar, a TG calendar, a super calendar and a soft calendar.

The coating amount of the ink receiving layer in the ink jet recording sheet according to the present invention is such that the support is impregnated with the ionizing radiation-curable compound and cured, and the problems of cockling property and curling property are improved. Because it has been
It is not particularly limited, for example, without regard even fine coating of about 0.5 to 3 g / m ^2, usually at 5 to 30 g / m ^2. However, if the coating amount of the ink receiving layer exceeds 30 g / m ² , the printing density and color reproducibility are deteriorated due to the problem of the ink receiving layer, which is not preferable. Further, the ink receiving layer can be applied by applying a certain amount of coating in several times.

A back coat layer may be provided on the opposite surface of the ink receiving layer sandwiching the support in order to impart curl aptitude, and the tabular pigment is used as a pigment at that time. Or hydrolyzed halloysite is preferable, and even if no back coat is provided, curl can be forced by injecting water vapor with a humidifier such as Fludex.

[Ink] The ink referred to in the present invention is a recording liquid containing the following dyes, solvents and other additives, and the dyes have good coloring properties, vividness, stability, etc., for example, C. I. Direct Yellow 1
2, C.I. I. Direct Yellow 24, C.I.
I. Direct Yellow 26, C.I. I. Di
rect Yellow 44, C.I. I. Direct
Yellow 86, C.I. I. Direct Yel
low 98, C.I. I. Direct Yellow
100, C.I. I. Direct Yellow 14
2, C.I. I. Direct red 1, C.I. I. Di
rect red 4, C.I. I. Direct red
17, C.I. I. Direct red 28, C.I. I.
Direct red 83, C.I. I. Direct O
range 34, C.I. I. Direct Orange
e 39, C.I. I. Direct Orange 4
4, C.I. I. Direct Orange 46, C.I.
I. Direct Orange 60, C.I. I. Di
rect Violet 47, C.I. I. Direct
Violet 48, C.I. I. Direct Blu
e 6, C.I. I. Direct Blue 22, C.I.
I. Direct Blue 25, C.I. I. Dire
ctBlue 71, C.I. I. Direct Blue
86, C.I. I. Direct Blue 90, C.I.
I. Direct Blue 106, C.I. I. Dir
ect Blue 199, C.I. I. Direct B
rack 17, C.I. I. Direct Black
19, C.I. I. Direct Black 32, C.I.
I. Direct Black 51, C.I. I. Dir
ect Black 62, C.I. I. Direct B
rack 71, C.I. I. Direct Black
108, C.I. I. Direct Black 146,
C. I. Direct dyes such as Direct Black 154, C.I. I. Acid Yellow 11, C.I. I.
Acid Yellow 17, C.I. I. Acid Y
ellow 23, C.I. I. Acid Yellow
25, C.I. I. Acid Yellow 29, C.I. I.
Acid Yellow 42, C.I. I. Acid Y
ellow 49, C.I. I. Acid Yellow
61, C.I. I. Acid Yellow 71, C.I.
I. Acid red 1, C.I. I. Acid red
6, C.I. I. Acid red 8, C.I. I. Aci
d red32, C.I. I. Acid red 37,
C. I. Acid red 51, C.I. I. Acid
red 52, C.I. I. Acid red 80, C.I.
I. Acid red 85, C.I. I. Acid re
d 87, C.I. I. Acidred 92, C.I. I. A
cid red 94, C.I. I. Acid red11
5, C.I. I. Acid red 180, C.I. I. Ac
id red 256, C.I. I. Acid red 3
17, C.I. I. Acid red 315, C.I. I. A
cid Orange 7, C.I. I. Acid Ore
nge 19, C.I. I. Acid Violet 4
9, C.I. I. Acid Blue 9, C.I. I. Aci
d Blue 22, C.I. I. Acid Blue 4
0, C.I. I. Acid Blue 59, C.I. I. Ac
id Blue 93, C.I. I. Acid Blue
102, C.I. I. Acid Blue 104, C.I.
I. Acid Blue 113, C.I. I. Acid
Blue 117, C.I. I. Acid Blue 12
0, C.I. I. Acid Blue 167, C.I. I. A
cid Blue 229, C.I. I. Acid Blu
e 234, C.I. I. Acid Blue 254,
C. I. Acid Black 2, C.I. I. Acid
Black 7, C.I. I. Acid Black 2
4, C.I. I. Acid Black 26, C.I. I. A
cid Black 31, C.I. I. Acid Bla
ck 52, C.I. I. Acid Black 63,
C. I. Acid Black 112, C.I. I. Ac
Acid dyes such as id Black 118, and other basic dyes, reactive dyes, or water-soluble dyes such as food dyes can be used.

As the solvent for the ink, water and various water-soluble organic solvents such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol and isobutyl are used. Alkyl alcohols having 1 to 4 carbon atoms such as alcohols; amides such as dimethylformamide and dimethylacetamide; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyethylene glycol, polypropylene glycol, etc. Polyalkylene glycols; ethylene glycol, propylene glycol, butylene glycol,
Alkylene glycols having 2 to 6 alkylene groups such as triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and diethylene glycol; glycerin, ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether , Lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether, and the like.

Among the above water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether are particularly preferable.

As other additives to be added to the ink, for example, PH adjusting agent, sequestering agent, antioxidant,
Examples thereof include antifungal agents, viscosity modifiers, surface tension modifiers, wetting agents, surfactants, and rust preventives.

[0054]

In recent years, the amount of ink ejected per unit area of an ink jet recording sheet has increased with the increase in definition of ink jet recording apparatuses. Here, the amount of ejected ink is usually about 7 to 10 g / m ^{2 for} a single color,
Therefore, it is 30 to 40 g / m ² in full-color printing with yellow, magenta, cyan, and black inks. Further, in an inkjet recording device for obtaining a high-definition image, the amount is about 60 to 100 g / m ² .

On the other hand, there is a demand for an ink jet recording sheet having a more plain paper-like texture, that is, a slightly coated ink jet recording sheet.

In the fine coating type ink jet recording sheet in which the ink ejection amount is increased due to the high definition of the ink jet recording apparatus and the coating amount of the ink receiving layer is reduced as compared with the conventional coat type ink jet recording sheet, The cockling property and the curl property, which are generated by the swelling of the paper support due to absorption, are contradictory properties. However, if the inkjet recording sheet of the present invention is prepared by impregnating a specific amount of a specific ionizing radiation-curable compound with a cured support, cockling property and curl can be obtained even with a fine coating type inkjet recording sheet. Good printed images with improved properties are obtained. The support impregnated with the specific ionizing radiation-curable compound in the invention has a form in which the compound is impregnated to fill the voids between the wood pulps, but if the impregnation amount is within a specific range, the ink absorbency may be reduced. In addition, the print density and the ink fixability can be improved.

Further, in general, irradiating the base paper with the ionizing radiation for the purpose of curing the ionizing radiation-curable compound adversely affects the wood pulp and various additives constituting the base paper, but after the irradiation, radicals are generated. By treating with a polymerization inhibitor, for example, the disadvantage that the base paper is colored pale yellow can be improved.

[0058]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.
Further, “parts” and “%” shown in the examples represent parts by weight and% by weight, unless otherwise specified.

Example 1 80 parts of LBKP (freezing degree of 400 mlcsf) and NBKP
Pigment 20 in which the ratio of light calcium carbonate / heavy calcium carbonate / talc is 10/10/10 with respect to 100 parts of wood pulp consisting of 20 parts (freeness 480 mlcsf)
Parts, commercially available alkyl ketene dimer 0.10 parts, commercially available cationic acrylamide 0.03 parts, commercially available cationized starch 1.0 part, and sulfuric acid band 0.5 parts, and papermaking with a Fourdrinier paper machine, basis weight 100 g A base paper of / m ² was obtained.

A 60% IPA / water solution of a hydrophilic ionizing radiation-curable compound (Nippon Kayaku, PET-30: pentaerythritol acrylate) was applied to this base paper at a dry weight of 5 g / m ² using a size press. It was impregnated as described above, and the compound was cured by irradiating it with an electron beam under the irradiation conditions of an accelerating voltage of 175 KV and an irradiation dose of 3 Mrad, and then the solvent was dried using a hot air dryer to obtain a support.

On the support thus obtained, a 14% solids aqueous solution of the coating composition for the ink-receiving layer described below was applied by an air knife coater to a dry coating amount of 10 g / m ^2. The ink jet recording sheet of Example 1 was obtained by manufacturing and drying. [Ink receiving layer coating composition] Synthetic amorphous silica (Powdered by Mizusawa Chemical Co., P-527, specific surface area 60 m ² / g) 100 parts Polyvinyl alcohol (Kuraray Co., PVA117) 30 parts Cationic dye fixing agent (Sumitomo Chemical Made, Sumirez Resin 1001) 30 parts

Example 2 The impregnation amount of the ionizing radiation-curable compound was 15 g / dry weight.
Example 2 was prepared in the same manner as in Example 1 except that m ² was used.
To obtain an inkjet recording sheet.

Example 3 The impregnation amount of the ionizing radiation-curable compound was 30 g / dry weight.
Example 3 was prepared in the same manner as in Example 1 except that m ² was used.
To obtain an inkjet recording sheet.

Example 4 The impregnation amount of the ionizing radiation-curable compound was 50 g / dry weight.
Example 4 was prepared in the same manner as in Example 1 except that m ² was used.
To obtain an inkjet recording sheet.

Example 5 The impregnation amount of the ionizing radiation-curable compound was 80 g / dry weight.
Example 5 was prepared in the same manner as in Example 1 except that m ² was used.
To obtain an inkjet recording sheet.

Example 6 An ink jet recording sheet of Example 6 was obtained in the same manner as in Example 3 except that diethylene glycol diacrylate (SR-230 manufactured by Nippon Kayaku Co., Ltd.) was used as the ionizing radiation curable compound. .

Example 7 An ionizing radiation-curable compound was used as polyethylene glycol 4
00 diacrylate (Nippon Kayaku, PEG400DA)
An inkjet recording sheet of Example 7 was obtained in the same manner as in Example 3 except for the above.

Example 8 An inkjet recording sheet of Example 8 was obtained in the same manner as in Example 3 except that ethylene oxide-modified trimethylolpropane triacrylate was used as the ionizing radiation-curable compound.

Example 9 A cationic compound (dimethylamine epichlorohydrin, number average molecular weight: 1200, cationic charge: 7.0 meq./g) was applied to the base paper of Example 1 using a size press.
0.5 g / m ² of a 30% aqueous solution of The cation charge amount per unit area of the base paper is 1.05 meq./g. An ink jet recording sheet of Example 9 was obtained in the same manner as in Example 3 except that the base paper thus produced was used.

Example 10 Using the size press on the base paper of Example 1, two cationic compounds (acrylamide diallylamine polymer, number average molecular weight: 9000, cationic charge: 3.5 meq./g) were used.
A 0% aqueous solution was impregnated with 5 g / m ² . The cation charge amount per unit area of the base paper is 0.88 meq./g. An inkjet recording sheet of Example 10 was obtained in the same manner as in Example 3 except that the base paper thus produced was used.

Example 11 Using the size press on the base paper of Example 1, a cationic compound (dicyandiamide formaldehyde polymer, number average molecular weight: 4000, cationic charge amount: 10.0 meq./
15 g / m ² of 6% aqueous solution of g) was impregnated. The cation charge amount per unit area of the base paper is 9.00 meq./g. An inkjet recording sheet of Example 11 was obtained in the same manner as in Example 3 except that the base paper thus produced was used.

Example 12 In the same manner as in Example 3 except that the inorganic pigment in the ink receiving layer was synthetic amorphous silica (Fineseal X37B, manufactured by Tokuyama Soda) having a specific surface area of 270 m ² / g by the BET method. The inkjet recording sheet of Example 12 was prepared.

Example 13 An ink jet recording sheet of Example 13 was obtained by spraying a 0.5% 2,6-dichlorobenzoquinone alcohol solution as a radical polymerization inhibitor onto the support prepared in Example 3. .

Example 14 A 0.5% 2,6-dichlorobenzoquinone alcohol solution as a radical polymerization inhibitor was sprayed on the support prepared in Example 7 to obtain an ink jet recording sheet of Example 14. .

Example 15 An ink jet recording sheet of Example 15 was obtained in the same manner as in Example 3 except that the dry coating amount of the ink receiving layer was 5 g / m ² .

Example 16 An ink jet recording sheet of Example 16 was obtained in the same manner as in Example 3 except that the dry coating amount of the ink receiving layer was 3 g / m ² .

Comparative Example 1 An ink jet recording sheet of Comparative Example 1 was obtained in the same manner as in Example 3 except that the base paper was used as it was as a support without being impregnated with an ionizing radiation-curable compound.

Comparative Example 2 The same as Example 3 except that the base paper was used as it was as a support without being impregnated with the ionizing radiation-curable compound, and the dry coating amount of the ink receiving layer was 5 g / m ^2. An inkjet recording sheet of Comparative Example 2 was obtained in the same manner.

Comparative Example 3 The same as Example 3 except that the base paper was used as a support without impregnating the ionizing radiation-curable compound, and the coating amount of the ink receiving layer was 3 g / m ^{2 in} terms of dry coating amount. An ink jet recording sheet of Comparative Example 3 was obtained in the same manner.

Comparative Example 4 The impregnation amount of the ionizing radiation-curable compound was 1 g / m ² on a dry weight basis.
An ink jet recording sheet of Comparative Example 4 was obtained in the same manner as in Example 1 except for the above.

Comparative Example 5 The impregnation amount of the ionizing radiation-curable compound was 3 g / m ² in terms of dry weight.
An ink jet recording sheet of Comparative Example 5 was obtained in the same manner as in Example 1 except for the above.

Comparative Example 6 The impregnation amount of the ionizing radiation-curable compound was 87 g / dry weight.
Comparative Example 6 was prepared in the same manner as in Example 1 except that m ² was used.
To obtain an inkjet recording sheet.

Comparative Example 7 The impregnation amount of the ionizing radiation-curable compound was 95 g / dry weight.
Comparative Example 7 was prepared in the same manner as in Example 1 except that m ² was used.
To obtain an inkjet recording sheet.

Evaluations of Examples 1 to 16 and Comparative Examples 1 to 7 were carried out by the methods described below, and the results are summarized in Table 1.

<Printing Density> Each inkjet recording sheet sample was conditioned under the environment of 20 ° C. and 65% RH for 24 hours, and then black ink was printed using an inkjet printer (manufactured by Hewlett Packard, disk writer 550C). Solid printing was carried out with, and the optical reflection density of the printed portion was measured by Macbeth RD-919.

<Water Absorption of Support> The water absorption of the support of each ink jet recording sheet sample is measured according to JIS P814.
It was measured by the method defined as 0.

<Ink Absorbency> Each ink jet recording sheet sample was placed under the environment of 20 ° C. and 65% RH for 24 hours.
After adjusting the humidity for a certain period of time, solid print with black ink using an ink jet printer (manufactured by Hewlett-Packard, disk writer 550C), cover the printed area with a blank sheet immediately after printing, and evaluate according to the following criteria based on how dirty the blank sheet is. did. ◯: No ink transfer was confirmed, and ink absorbability was excellent. Δ: Ink transfer is slightly confirmed. X: Ink transfer is on the entire surface, and ink absorbency is poor.

<Ink Fixability> Each ink jet recording sheet sample was placed under the environment of 20 ° C. and 65% RH for 24 hours.
After adjusting the humidity for a certain period of time, draw a straight line with black ink using an inkjet printer (disc 550C made by Hewlett-Packard) to determine the thickness of the straight line (W
B) is measured. Then, 50 μl of water was dripped on the straight line, and the thickness (WA) of the straight line after standing for 24 hours was measured. When the ink fixability is poor and ink bleeding occurs, the ink bleeding rate (WA / WB) exceeds 1.0. Measurement is performed by the modal method using an image analysis device.
The value is converted into a straight line (L2) perpendicular to the measured straight line (L1), and the parallel line with L2 is moved to the measurement part to obtain the thickness of the straight line (L1) before and after water dropping. It was

<Hue of Inkjet Recording Sheet> The hue change of the inkjet recording sheet was determined in order to know the degree of coloration of the support obtained by impregnating and curing the ionizing radiation-curable compound. Hue L ^* a ^* b ^* (CIE197) of the ink-receiving layer after humidity conditioning of each inkjet recording sheet sample for 24 hours under the environment of 20 ° C. and 65% RH
6) was measured with a color difference meter, CR-100 manufactured by Minolta. Further, the humidity was continuously measured for 3 months, and the hue was measured in the same manner. 24-hour moisture-conditioned samples and three months moisture-conditioned samples of b ^* of the difference between the (△ b ^*) were determined.

<Cockling Property> Each ink jet recording sheet sample (A4 size) was tested at 20 ° C. and 65% RH.
After conditioning the humidity for 24 hours under the environment of, the cockling property of the sample after performing solid printing three times in succession with black ink using an inkjet printer (made by Hewlett Packard, disk writer 550C) Was evaluated according to the following criteria. ◯: Cockling was not observed at all and was good. Δ: There was partial waviness and the quality of the printed image was degraded. X: Vigorous cockling occurred and the quality of the printed image was significantly reduced.

<Curl Property> Each inkjet recording sheet sample (A4 size) was conditioned under an environment of 20 ° C. and 65% RH for 24 hours, and then an inkjet printer (manufactured by Hewlett-Packard, disk writer 5).
Solid printing was performed three times with black ink using 50C), and then the sample was placed on a desk with the printed surface facing up. At this time, the heights of the four corners of the sample from the desk surface were measured, the arithmetic mean value was calculated, and the evaluation was made according to the following criteria. ○: 0 to 0.5 cm △: 0.6 to 3 cm ×: 3.1 cm or more

[0092]

[Table 1]

As shown in Table 1, the ink jet recording sheet of the present invention is excellent in print density, ink fixability and hue, and is excellent in cockling regardless of the amount of ink hit and the ink absorbability of the ink receiving layer. It was shown in Examples 1 to 20 that the curability and curling property are improved. Here, in Examples 6 to 7, as compared with Examples 1 to 5, the ionizing radiation curable compound contained ethylene oxide, and therefore the print density was further improved. Further, in Examples 9 to 11, since the support contained a cationic compound, the print density and the ink fixability were further improved.
In Examples 13 and 14, the support after being impregnated with the ionizing radiation-curable compound and cured was treated with the radical polymerization inhibitor, so that the hue of the sheet was hardly changed even after long-term storage. Further, it was shown in Examples 15 and 16 that the support in the inkjet recording sheet of the present invention can be suitably used for a slightly coated type inkjet recording sheet. However, in Comparative Examples 1 to 3, the cockling property and the curl property were poor. In particular, Comparative Example 2
Since Nos. 3 and 3 were slightly coated ink jet recording sheets, the print density and the ink fixability were poor, and the cockling property and the curl property were significantly deteriorated. Comparative Examples 4 to 7
Then, although a support impregnated with an ionizing radiation-curable compound was used, since the impregnated amount of the compound was not an appropriate amount, the printing density and the ink absorptivity were lowered, and particularly the impregnated amount was too small. In Nos. 5 and 5, the cockling property and the curl property were not sufficiently improved.

[0094]

As is apparent from the above, according to the present invention, the print density, the ink fixing property, and the hue are excellent, and the cockling property and the curl are obtained irrespective of the ink ejection amount and the ink absorbing property of the ink receiving layer. It is possible to obtain an inkjet recording sheet having improved properties and suitable for a high-definition inkjet recording system.

Claims (4)

[Claims] 1. An inkjet recording sheet having an ink-receiving layer on at least one surface of a support, wherein the support contains a hydrophilic ionizing radiation curing material containing two or more ethylenic double bonds in one molecule. An ink jet recording sheet, characterized in that the functional compound is impregnated in an amount of 5 to 80% of the basis weight of a base paper containing wood pulp as a main component, and then cured by irradiation with ionizing radiation. 2. The ionizing radiation-curable compound contains ethylene oxide in the molecule.
The inkjet recording sheet described. 3. The inkjet recording sheet according to claim 1, wherein the support contains a cationic compound. 4. The ink jet recording sheet according to claim 1, wherein the support is treated with a radical polymerization inhibitor.