JP2002160439A - Ink jet recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pigment-based high-performance ink jet recording body, which has a crack-free porous ink accepting layer, is excellent in gloss, transparency and water resistance and favorable in image quality and ink drying properties. SOLUTION: In the ink jet recording body having one or more coating layers on a base material, in at least one layer, the porous ink accepting layer is formed by coating a water-based paint prepared by mixing 1 to 100 pts.wt. of a hydrophilic resin (b), which has no radical polymerizable unsatured bonding and forms a hydrogel through an electron beam irradiation of an aqueous solution, with 100 pts.wt. of fine pigment (a), the mean particle diameter of which is 1 μm or less and the pore volume of 0.4 to 2.5 ml/g, and then hydrogelating the coating layer through the electron beam irradiation and finally drying so as to form the porous ink accepting layer of the ink jet recording body.

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 material having an ink receiving layer mainly composed of a pigment, and more particularly to a high performance ink jet recording material having excellent gloss, transparency and water resistance, and also having good image quality and ink drying property. .

[0002]

2. Description of the Related Art Conventionally, various systems such as a wire dot recording system, a thermosensitive color recording system, a fusion heat transfer recording system, a sublimation recording system, an electrophotographic system, and an ink jet recording system have been developed for outputting to a computer or the like. .
Among them, the ink jet recording method is recognized as a recording method suitable for personal use, because plain paper can be used as a recording sheet, running cost is low, and hardware is compact and inexpensive. Further, in recent years, the achievement of full color and high resolution has attracted attention as a means for easily outputting color images, and the number of printers sold has rapidly increased.

The ink jet recording medium used for the output of these ink jet printers is capable of quickly absorbing ink containing water, a dye, an organic solvent, an additive, etc., reproducing a fine character or image, and having a color density of the image. It is required as basic performance that it is high and there is no bias in color tone. In order to satisfy this requirement, many high-performance ink jet recording media are provided with a dedicated ink receiving layer on a base material, and these receiving layers can be roughly classified into two types, a resin type and a pigment type. . The resin-based receiving layer is usually formed by applying an aqueous solution of a water-soluble resin such as polyvinyl alcohol, polyvinylpyrrolidone, a water-soluble cellulose derivative, or gelatin to a base sheet and drying the base sheet. Inexpensive and easy to manufacture. The resin-based receiving layer is often used as an ink jet recording medium for an overhead projector (hereinafter abbreviated as OHP), which requires transparency, by taking advantage of its high transparency. In addition, there is an advantage that the ink absorption amount per unit weight of the receiving layer is larger than that of the pigment system.

[0004] However, not only are the requirements for image quality already mentioned for the ink jet recording medium, but also the drying properties of the ink,
Various performances such as water resistance of the printed matter, that the image is not deteriorated even when posted indoors and outdoors for a long time, and that no blocking occurs even when stored in a laminated state are required. In particular, the resin-based receiving layer is inferior to the pigment-based receiving layer in ink drying property and water resistance, and it has been required to improve them. As general quality improvement measures, attempts have been made to crosslink the water-soluble resin of the receptor layer using a crosslinker, or to impart water resistance by mixing a hydrophobic resin. However, no matter what kind of cross-linking agent or hydrophobic resin is used, if sufficient water resistance is imparted, the ink absorbing ability of the receiving layer is remarkably reduced, and it is impossible to achieve both image quality and water resistance.

Accordingly, the present inventors have developed an aqueous composition containing, as a main component, a water-soluble resin having no radically polymerizable unsaturated bond and forming a hydrogel by irradiating an aqueous solution with an electron beam. Was applied to a base sheet, and then irradiated with an electron beam to form a hydrogel, and then dried, to propose a resin-based receiving layer (JP-A-11-157).
No. 202). This resin-based receiving layer was provided with water resistance without significantly deteriorating the image quality as compared with the uncrosslinked receiving layer not irradiated with the electron beam. However,
This resin-based receiving layer is not porous and has a mechanism to absorb ink by swelling, so there is a limit to the ink absorption speed, and to satisfy image quality and ink drying time with a recent inkjet printer with a large amount of ink ejection, Further improvements were needed. Also, the water resistance of the resin-based receiving layer was very high, but the water resistance of the high-performance pigment-based receiving layer was inferior. JP 8
JP-207423 and JP-A-8-267905 disclose examples of an inkjet recording sheet having an electron beam-cured outer layer containing a polyalkylene oxide-based water-soluble polymer and colloidal silica. Since the pigment was only dispersed in the resin and was not porous, the ink absorption proceeded only by swelling of the receiving layer, as in the case of the receiving layer composed of only the resin.

On the other hand, a pigment-based receiving layer produced by solidifying a pigment with a binder resin receives ink quickly by capillary action in pores secured inside and outside the pigment to form an image, and the ink is dissolved or swelled by swelling. A higher level of image quality and ink drying property can be easily obtained as compared with a resin-based receiving layer that absorbs water. In the pigment-based receiving layer, if the binder resin has water resistance, the water resistance of the receiving layer also becomes very high. However, in order to obtain a high-quality image, it is necessary to secure a sufficient pore volume in the receiving layer to sufficiently correspond to the ink to be ejected. Requires a very large amount of coating.

At present, a pigment-based receiving layer is manufactured by coating a powdery synthetic amorphous silica having an average particle diameter of 1 to 20 μm in water and mixing it with a water-resistant binder resin and additives. Is applied. Such a pigment-based receiving layer has water resistance and a large amount of ink absorption, but the transparency of the ink-receiving layer is low because the average particle diameter of the pigment is large. When the transparency of the ink receiving layer is low, it is not only unsuitable for producing a translucent recording medium using a transparent substrate, but also when an opaque substrate is used, the print density of an image is low. This is disadvantageous. Further, the synthetic amorphous silica used here has a large particle size and is non-uniform, so that the glossiness of the receiving layer is low, and is not suitable for producing a glossy ink jet recording material.

In view of the above, in order to produce a high-quality ink jet recording medium with emphasis on the glossiness and ink absorbing power of the ink receiving layer, it is necessary to have a large pore volume, a small average particle size, and a uniform fineness. Pigments are preferably used. In particular, fine pigments such as silica, aluminum hydroxide, boehmite, pseudo-boehmite, and alumina are preferably used.
However, since these fine pigments have a large pore volume and a small pore diameter, contraction due to capillary force generated during drying after coating is remarkable, so that the coating layer is very easily cracked. According to the study of the present inventors, when a receiving layer is formed using these fine pigments, a highly saponified polyvinyl alcohol having a high polymerization degree, which has a strong binder power and crystallizes after drying to become water-resistant, is mixed. Then, multi-layer coating with low coating amount divided into several times, and by reducing the shrinkage force generated during one drying, cracking of the receiving layer, and decrease in gloss and transparency caused by cracking Can be suppressed. However, such multi-layer coating is not only low in production efficiency,
Coating of the second and subsequent layers requires care so as not to damage the voids formed in the lower layer, and tends to cause operational problems such as generation of air bubbles. Therefore, it is desirable that the required coating amount can be secured by one coating if possible. However, if the amount of the binder resin is simply increased in order to prevent cracking, the resin fills the pores formed by the fine pigments, which adversely affects the ink absorbency.

In Japanese Patent Application Laid-Open No. 7-76161, polyvinyl alcohol and boric acid or borate are added to a fine pigment dispersion to gel a coating film during drying, and to cause fine cracks which cause cracks. It has been proposed to suppress the occurrence of. It is thought that if the coating film before drying is gelled, the binder power is increased and it is considered to be effective in preventing cracking. However, this method has a problem in the stability of the coating liquid. In addition, as a method for gelling a coating film before drying, Japanese Patent Application Laid-Open No.
JP-A-218324 discloses a sol coating method in which a fine pigment dispersion stabilized by an acid or alkali deflocculant is applied and then the deflocculant is removed by exposure to an alkali or acidic gas. . This technique can also be expected to have a certain degree of crack suppression effect, but it is necessary to handle a high concentration of gas at the time of manufacturing the receiving layer, or the odor remains in the dried coating film, and the final pH is remarkably biased to acidity or alkalinity Because of the potential, the feasibility is problematic.
Japanese Patent Application Laid-Open No. 9-263038 discloses a method for gelling a coating film before drying by applying a coating liquid mainly composed of an inorganic sol and an ionizing radiation-curable compound, and then irradiating the coating solution with ionizing radiation. A method has been proposed in which after a step of curing a reactive compound, a coating film is dried to form an ink receiving layer. However, even if we tried this method,
If a gel with sufficient strength cannot be obtained and a fine pigment with a high pore volume with high ink absorption performance is used,
The receiving layer cracked during drying. In addition, since many ionizing radiation-curable compounds have a relatively low molecular weight or a strong skin irritation property, there are many concerns about adverse effects on printing quality due to uncured components and safety. Furthermore, since most ionizing radiation-curable compounds on the market have low hydrophilicity, they are not suitable for general aqueous coating for coating the ink jet receiving layer, and the range of material selection becomes extremely narrow. . On the other hand, even if gelation is attempted using a chemical crosslinking agent, which is a general method, chemical crosslinking requires a certain amount of heat and time, and the gelation speed cannot keep up with the drying speed of the coating layer, and gelation proceeds. Cracks will occur before doing so.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pigment-based ink having a porous ink-receiving layer without cracks, having excellent gloss, transparency and water resistance, and having good image quality and ink drying properties. It is intended to provide a high performance ink jet recording medium. It is another object of the present invention to provide a pigment-based high-performance ink jet recording medium which uses a fine pigment which is easily cracked and which does not crack even when the coating amount of the ink receiving layer is large.

[0011]

The present invention employs the following configuration to solve the above-mentioned problems. That is, the first invention of the present invention relates to “an ink-jet recording medium having one or more coating layers on a substrate, wherein at least one of (a) the average particle size is 1 μm or less and the pore volume is 0.4 to 0.4 μm. 2.5 ml / g of a fine pigment and (b) a hydrophilic resin having no radically polymerizable unsaturated bond and forming a hydrogel by irradiating an aqueous solution with an electron beam, A water-based paint containing (b) 1 to 100 parts by weight is applied to 100 parts by weight, and then the coating layer is hydrogelled by irradiating with an electron beam, and then dried to form a porous layer. Ink-jet recording material which is a high-quality ink-receiving layer ".

The second invention of the present invention relates to an ink-jet recording material having one or more coating layers on a substrate, wherein at least one of the ink-jet recording material comprises (c) a fine pigment having an average particle diameter of 1 μm or less; A hydrophilic resin having no radically polymerizable unsaturated bond and forming a hydrogel by irradiating an aqueous solution with an electron beam, and (d) 1 to 100 parts by weight of (c) A water-based paint containing 100 parts by weight is applied, and then the applied layer is irradiated with an electron beam to hydrogel, and then dried to form a pore volume of 0.2 to 2.0 ml / g. The ink-jet recording material which is a porous ink-receiving layer of the invention.

[0013] The third invention of the present invention relates to "the ink-jet recording material according to the first or second invention, wherein the ink receiving layer has a dry weight reduction of 10% or less after immersion in water for one hour". is there.

The fourth invention of the present invention is directed to a hydrophilic resin which has no radically polymerizable unsaturated bond and forms a hydrogel by irradiating an aqueous solution with an electron beam. , Polyalkylene oxide, polyvinylpyrrolidone, water-soluble polyvinyl acetal, poly-N-vinylacetamide, polyacrylamide, polyacryloylmorpholine, polyhydroxyalkylacrylate, polyacrylic acid, hydroxyethylcellulose, methylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, gelatin , Casein, a water-soluble derivative thereof, and an inkjet according to any one of the first to third inventions, wherein the inkjet is at least one selected from the group consisting of copolymers thereof. Recording body ".

[0015] The fifth invention of the present invention relates to a method wherein the hydrophilic resin having no radically polymerizable unsaturated bond and forming a hydrogel by irradiating an aqueous solution with an electron beam is a cationic derivative. The inkjet recording material according to the fourth aspect of the invention ".

[0016] The sixth invention of the present invention relates to a method wherein the fine pigment is silica, aluminum hydroxide, boehmite, pseudo-boehmite,
And the ink-jet recording material according to any one of the inventions 1 to 5, which is at least one selected from the group consisting of alumina and alumina.

The seventh invention of the present invention provides a method for producing a fine pigment, which comprises a primary pigment having an average particle diameter of 3 to 40 nm and an average particle diameter of 8 to 40 nm.
The inkjet recording material according to any one of the first to sixth inventions, wherein the inkjet recording material is a secondary particle having a particle size of 800 nm.

The inventors of the present invention can use the fine pigment, which can be a raw material of the ink receiving layer excellent in image quality and ink drying property, which is liable to crack upon drying, how to form the ink receiving layer. Various studies were made. As a result, in order to obtain an ink receiving layer with a high coating amount that is compatible with recent ink jet printers with a large amount of ink discharge, and that has no cracks, high gloss, and high transparency, it is necessary to use a binder resin used for the coating layer. I realized again that strength had to be increased considerably. However, the conventional technology has not been able to impart sufficient strength to the binder resin.

Therefore, first, a water-based paint obtained by mixing a generally used fine pigment and fully saponified polyvinyl alcohol as a binder resin is applied in an amount of 25 g / dry weight.
It was applied to the base material so as to obtain m ^{2, and} was immediately irradiated with an electron beam. As a result, it was found that the binder resin was crosslinked and the entire coating layer became a hydrogel having high gel strength. When the coating film was further dried, a high gloss and high transparency ink receiving layer free of cracks was obtained by the action of the binder resin which had become a high molecular weight gel by crosslinking. When printing was performed on this coating film using an inkjet printer, a high-quality image was obtained, and the ink drying property was also good. On the other hand, as a comparison, even if an attempt was made to produce an ink receiving layer without performing electron beam irradiation, severe cracks occurred on the entire surface, and thus the ink receiving layer was unsuitable for an ink jet recording medium. In addition, when examining the effect of electron beam irradiation under a low coating amount condition that allows film formation without cracking without electron beam irradiation, the electron beam irradiation was compared with the coating layer without electron beam irradiation. It was found that in the coating layer subjected to the irradiation with light, aggregation of fine pigments occurring during drying was suppressed, and gloss and transparency were increased. Further, since the binder resin gels before drying and increases in strength, migration of the binder resin during drying, powdering of fine pigments from the surface of the receiving layer is prevented, and the water resistance of the coating film is improved. It turned out that there was also. In addition, since the crosslinking of the binder resin by electron beam irradiation is not limited to a resin having a specific functional group, various hydrophilic resins other than the fully saponified polyvinyl alcohol, which is relatively unlikely to crack, are used as a binder. Even when used as a resin, it was confirmed that a high-performance ink jet recording body having the same effect of preventing cracking, improving gloss, transparency, and water resistance, and also having good image quality and ink drying properties could be produced. Was completed.

[0020]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a fine pigment having an average particle size of 1 μm or less is used. As a result, a receiving layer having excellent ink absorbency and excellent transparency and gloss can be obtained. Here, the average particle size is a particle size measured by a dynamic light scattering method (a value obtained by a cumulant method). Types are not limited, but commercially available pigments such as silica, aluminosilicate, kaolin, clay, calcined clay, zinc oxide, tin oxide, aluminum hydroxide, boehmite, pseudo-boehmite,
Alumina, calcium carbonate, satin white, aluminum silicate, smectite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, urea resin plastic pigment, benzoguanamine plastic pigment, etc. Various pigments known in the art can be mentioned. Among these fine pigments, silica, aluminum hydroxide, boehmite, pseudoboehmite, and alumina are particularly preferably used because of their large pore volume and excellent ink absorbability.

Particularly, silica is preferable because it has the largest pore volume. Silica includes wet-process silica using alkali silicate as a raw material, and dry-process silica that decomposes volatile silicon compounds such as silicon tetrachloride in a flame, and both are preferable. Suitable silica pore volumes are 0.4-2.1 ml / g
It is. There is also silica generally called colloidal silica, which is usually treated with an aqueous solution of an alkali silicate with an ion exchange resin to produce an aqueous solution of silicic acid, and after adding an alkali to stabilize the aqueous solution of silicic acid, It is produced by heating to form a liquid in which fine silica is monodispersed, and gradually adding a silicic acid aqueous solution to grow the silica fine particles. As can be seen from the production method of colloidal silica, the silica particles do not form secondary particles. For this reason, the pore volume is in the range of 0.2 to 0.3 ml / g, which is disadvantageous even when used in an ink receiving layer because the amount of absorbed ink is small.

In order to obtain a highly glossy and highly transparent ink receiving layer, a fine pigment having an average particle size of 1 μm or less is used. Preferably, the fine pigment is formed by aggregation of primary particles having an average particle size of 3 to 40 nm. Secondary particles having an average particle size of 8 to 800 nm. In particular, the particle size of the secondary particles is preferably 9 to 700 n.
m, more preferably 10 to 500 nm. Such secondary particles have a large pore volume because there are voids inside the secondary particles. Further, the gap between the secondary particles can also be used for ink absorption, so that the ink absorption capacity is high. In addition, since the primary particles are sufficiently smaller than the wavelength of light, there is an advantage that the light-scattering ability is smaller and the transparency of the ink receiving layer is higher than that of the pigment having no secondary particles. If the primary particle diameter or the secondary particle diameter of the pigment is too small, it is difficult to form voids contributing to ink absorption, and the ink absorption of the receiving layer may be poor. Conversely, if the primary particle diameter or the secondary particle diameter is too large, the transparency of the recording layer is reduced, and it may be difficult to obtain a high print density. On the other hand, if the secondary particle size is too large, not only may the gloss of the receiving layer be reduced, but also the surface may become rough and powder may fall off. In addition, the primary particle diameter of the pigment referred to in the present invention is a particle diameter (Martin diameter) observed with an electron microscope (SEM and TEM) (refer to “Microparticle Handbook”, Asakura Shoten, p. 52). The secondary particle size is
It is the particle size measured by the dynamic light scattering method.

In order to obtain an ink receiving layer having a high ink absorption capacity, it is preferable that the fine pigment has a high pore volume, but the fine pigment preferably used in the present invention has a pore volume of 0.4 to 0.4. 2.5 ml / g. Preferably 0.4
２．０2.0 ml / g, more preferably 0.6-1.
9 ml / g, most preferably 0.7 to 1.8 ml / g. This pore volume is a value obtained by using a specific surface area / pore distribution measuring device by a gas adsorption method. In the present invention, the pore volume is the total pore volume of pores having a pore diameter of 100 nm or less. In the fine pigment-based receiving layer, generally, the higher the pore volume of the fine pigment, the higher the ink absorbency of the coating layer, but the larger the contraction due to the capillary force that occurs during drying after coating, the larger the general A poor coating method is liable to cause poor film formation due to cracks and is not practical. However, the ink jet recording medium of the present invention does not need to be concerned about such film formation failure.

The method for producing these fine pigments is not particularly limited, but one of the means is a commercially available pigment (several μm).
And pulverizing and dispersing them by giving a strong force to them by mechanical means. In other words, breaking
It is obtained by a down method (a method of subdividing a bulk raw material). Examples of the mechanical means include mechanical methods such as an ultrasonic homogenizer, a pressure homogenizer, a nanomizer, a high-speed rotation mill, a roller mill, a container driving medium mill, a medium stirring mill, a jet mill, and a sand grinder. The obtained fine pigment may be in the form of a colloid or a slurry. As another preferable method for producing a fine pigment, a method by hydrolysis of a metal alkoxide disclosed in JP-A-5-32413, JP-A-7-76161 and the like can be mentioned.

The water-based paint used in the present invention does not have a radical polymerizable unsaturated bond, which is another main component,
The hydrophilic resin that forms a hydrogel by irradiating the aqueous solution with an electron beam includes fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, water-soluble polyvinyl acetal, and poly-vinyl alcohol.
Examples include N-vinylacetamide, polyacrylamide, polyacryloylmorpholine, polyhydroxyalkyl acrylate, polyacrylic acid, hydroxyethylcellulose, methylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, gelatin, casein, and water-soluble derivatives thereof. Water-soluble derivatives include cationically modified products, anionically modified products, derivatives in which functional groups such as hydroxyl groups, carboxyl groups, and amino groups are chemically modified by esterification, etherification, amidification, and other side chains by graft polymerization. The introduced polymer can be exemplified. Further, a copolymer containing each of the above resins or a water-soluble derivative may be used. As the copolymer, polyvinyl alcohol, polyvinylpyrrolidone, water-soluble polyvinyl acetal, poly-N-vinylacetamide, polyacrylamide, polyacryloyl morpholine, polyhydroxyethyl acrylate, copolymers composed of vinyl monomers such as polyacrylic acid, these Copolymers containing monomers other than the monomers constituting the polymer can be exemplified. These resins can be used alone or in combination of two or more. Among these hydrophilic resins, polyvinyl alcohol is preferable because of its good miscibility with the fine pigment.

Incidentally, the hydrogel is a polymer having a three-dimensional network structure swollen with a solvent containing water as a main component, and has no fluidity. Since the electron beam crosslinking reaction in the present invention mainly starts by hydrogen abstraction, a specific functional group is not crosslinked. The optimum value of the molecular weight of the hydrophilic resin specified in the present invention cannot be said unconditionally because the properties are different for each type of resin, but if it is too high,
When the coating liquid is easily gelled when mixed with the fine pigment, the coating liquid has a high viscosity even without gelling,
A problem may occur in coatability. Conversely, if the molecular weight is too low, the gel strength of the hydrogel obtained by electron beam irradiation becomes insufficient, so that cracks of the dried coating film occur, and the effect of the present invention may not be sufficiently obtained. is there.
Therefore, as a standard of molecular weight, a typical resin is 10,000 to 5
It is preferably about one million, more preferably five to one million.

As the derivative or copolymer of the specific hydrophilic resin, a cation-modified product is particularly preferable. For example, cationic polyvinyl alcohol, cationic polyvinyl pyrrolidone, cationic water-soluble polyvinyl acetal,
Cationic poly-N-vinylacetamide, cationic polyacrylamide, cationic polyacryloylmorpholine, cationic polyhydroxyalkyl acrylate, cationic hydroxyethyl cellulose, cationic methyl cellulose, cationic hydroxypropyl methyl cellulose, cationic hydroxypropyl cellulose, cationic Gelatin, cationic casein and the like. Dyes and pigments, which are coloring components in inks used in ink jet printers, often have an anionic group. Therefore, a cationic ink fixing agent is preferably used in the ink receiving layer. When the main component pigment is an anionic pigment such as silica, the use of a cationic resin as the binder resin not only makes the water resistance of the printed image more robust, but also reduces the coloring substances that occur in the receiving layer after printing. This is preferable because an effect of preventing color change over time due to movement and blurring of an image is expected. In order to change color tone over time after printing, it is also effective to use a resin having a high affinity for a hydrophilic high-boiling point solvent contained in the ink alone or as a mixture. As the hydrophilic high boiling point solvent contained in the ink, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol,
There are dipropylene glycol, diethylene glycol monomethyl ether, 2-pyrrolidone, thiodiglycol, triethylene glycol monobutyl ether, 1,5-pentanediol and the like. Examples of resins having a high affinity for these solvents include polyvinyl pyrrolidone and polyacryloyl. Morpholine, polyhydroxyalkyl acrylate, hydroxypropyl cellulose and the like,
It is not particularly limited to these.

The average particle size of the main component of the ink receiving layer is 1
μm or less, the proportion of a mixture of a hydrophilic resin having no radically polymerizable unsaturated bond and forming a hydrogel by irradiating an aqueous solution with an electron beam is 100 parts by weight of the fine pigment. On the other hand, the hydrophilic resin is 1 to 1
00 parts by weight. The ink jet recording medium of the present invention,
Since an image is formed mainly by receiving ink in pores formed inside and outside the fine pigment, the amount of the hydrophilic resin is preferably suppressed to a minimum amount from the viewpoint of ink absorption. Further, since the hydrophilic resin increases the apparent particle size of the fine pigment in the receiving layer, from the viewpoint of the transparency of the receiving layer, it is preferable that the amount of the hydrophilic resin is as small as possible without cracking. For the above reasons, more preferably, the hydrophilic resin is contained in an amount of 3 to 30 parts by weight, most preferably 5 to 25 parts by weight, based on 100 parts by weight of the fine pigment.

The ink receiving layer has a pore volume of 0.2 to 2.0.
It is preferable to adjust so as to be in the range of ml / g. It can be adjusted within this range by selecting the pore volume of the fine pigment and by appropriately adjusting the amount of the hydrophilic resin added. When the pore volume is less than 0.2 ml / g, the ink cannot be absorbed unless the coating amount is increased, so that the production cost of the ink jet recording body increases. 2.0 ml
If the pore volume exceeds / g, the mechanical strength of the ink receiving layer decreases, and the receiving layer is easily damaged, peeled, or cracked. The pore volume of the present invention is the total pore volume of pores having a pore diameter of 100 nm or less.

The preferred solid content concentration of the water-based paint used in the present invention varies greatly depending on the type of the fine pigment and resin used as the main component, but the higher the concentration, the more stable the water-based paint can be applied. Is preferred. The reason is that the higher the concentration of the water-based paint, the higher the efficiency of the cross-linking reaction that proceeds by electron beam irradiation, the higher the gel strength of the coating layer after gelation, and the lighter the drying load. is there. The hydrophilic resin that has no radical polymerizable unsaturated bond used in the present invention and forms a hydrogel by irradiating an aqueous solution with an electron beam is irradiated with an electron beam in a water-free state. When applied, the disintegration in which the molecular chain is broken proceeds preferentially, and the intended crosslinking reaction may not proceed,
It has been confirmed that when the same amount or more of water is present in the coating liquid with respect to the hydrophilic resin, the crosslinking reaction proceeds predominantly. Actually, since the higher the concentration of the aqueous dispersion of the fine pigment preferably used in the present invention, the higher the concentration, the more easily the gelation occurs, the upper limit of the concentration is often determined in terms of the stability of the aqueous paint. In consideration of the above points, the solid content concentration of the water-based paint is preferably 3 to 40% by weight, more preferably 5 to 25% by weight.

In addition to the main components, the water-based paint must be in a range that does not significantly degrade the coatability of the water-based paint, retains the pores necessary for ink absorption, and does not significantly reduce the water resistance of the receiving layer. For example, other components can be added to the ink receiving layer. These additives themselves may be components that do not form a hydrogel even when the aqueous solution is irradiated with an electron beam. One example is a cationic resin that is an ink fixing agent. Although the kind of the cationic resin is not particularly limited, for example, N, N-dimethylaminoethyl acrylate quaternary, N, N-dimethylaminoethyl methacrylate quaternary, N, N-dimethylaminopropylacrylamide quaternary And resins containing cationic structural units such as graded products, vinyl imidazolium methchloride, diallyl dimethyl ammonium chloride, monoallylamine hydrochloride and diallylamine hydrochloride. In addition, cationic resins containing dicyandiamide / polyalkylene polyamine condensate, secondary amine / epichlorohydrin addition polymer, polyepoxyamine, and the like can be used. It is also possible to mix an inorganic salt, alumina sol, or the like as the cationic substance.

In addition, a surfactant is mixed with an antifoaming agent as an additive to improve workability at the time of coating and to improve the wettability of the base material to obtain a uniform ink receiving layer. They may be blended, and starch or synthetic resin particles may be mixed to prevent blocking of the recording medium and to improve the paper permeability of the printer. In addition, various pigments other than the main component can be added to adjust the transparency and surface gloss, and lightfastness improvers such as ultraviolet absorbers and light stabilizers are added to improve the preservability of printed images. You can also.

As a method for adding these additives, a method may be used in which the additives are mixed in advance with a water-based coating material, or after a coating layer is formed, a solution containing the additives is overcoated, sprayed, or impregnated. May be added later. When the additive is added to the water-based paint in advance, if the paint is gelled by the shock of the addition, re-dispersion using a mechanical means is also an effective means. For example, when a cationic resin is added to a dispersion of an anionic pigment such as silica, the paint temporarily gels due to the electrostatic properties of both, but coating is possible if redispersed using mechanical means. In the dried coating film, both are strongly bound electrostatically, so that the water resistance of the coating film is sufficiently maintained even if the cationic resin is not particularly crosslinked.

The ink-receiving layer obtained in the present invention can exhibit sufficient surface gloss, image quality and ink drying properties when used as a single layer, but can also have a multilayer structure. In that case,
"Applying, electron beam irradiation, drying" may be repeated, or the next layer may be applied after application and electron beam irradiation, or the next layer may be applied immediately after application and subjected to electron beam irradiation. good.
Further, a multi-layer may be simultaneously applied and electron beam irradiation may be performed. Also, for layers that do not need to be irradiated, electron beam irradiation may not be performed. In particular, in the case of a multi-layer structure, it is preferable that the receiving layer of the present invention is used as a surface layer by utilizing very high quality surface properties.

If a plurality of layers are applied by a normal coating method without using an electron beam and then drying is performed at once, the layers are disturbed by the time the drying is completed, and the paints of the respective layers are mixed with each other. In many cases, the coating amount of each layer becomes uneven or the quality is adversely affected. In particular, when the coating material has a low viscosity, the coating speed is low, or the coating amount is high, mixing of the respective layers is likely to occur. It is desirable to repeat "coating and drying". However, repetition of “coating and drying” involves not only poor operability but also generation of waste paper and an increase in drying load, so that the production efficiency must be reduced.
Furthermore, depending on the formulation, the adhesive strength between layers tends to decrease,
The layers are easily separated. In this regard, if the coating material after application is immediately hydrogelated by using electron beam irradiation, a large turbulence between the layers can be suppressed and a multilayer coating layer having high adhesion between the layers can be obtained.

In particular, when a plurality of layers are successively coated with different heads, an electron beam irradiation step is provided after the lower layer is applied, and then the upper layer is applied, whereby the multilayer coating can be performed in a more stable state. It is preferable because it can be performed. In addition, in such a multilayer coating method, the upper layer is applied in a state where the pores in the lower layer are filled with water, so that the upper layer paint enters the lower layer pores and reduces the volume of the lower layer pores. I won't. Therefore, it is very suitable as a coating method when the coating layer requires porosity as in the ink jet recording medium of the present invention. On the other hand, when performing simultaneous multi-layer coating, relatively high-precision multi-layer coating can be performed than continuous coating with separate heads. It is possible to suppress interlayer turbulence,
A sufficiently high-precision multilayer coating layer can be obtained.

As the base material, as a base material of an ink jet recording medium such as a high quality paper, a medium paper, a coated paper, an art paper, a cast coated paper, a paperboard, a synthetic resin laminated paper, a metallized paper, a synthetic paper, a white film and the like. A commonly used sheet can be used, but is not limited thereto. Above all, when using a base sheet having a relatively smooth surface and a relatively low liquid absorbing property, such as a synthetic resin laminated paper, a metallized paper, a synthetic paper, a white film, and the like, use a method such as a film transfer method or a cast coating method. This is preferable because a very high gloss receiving layer can be obtained without it. Also, when using a plastic film having excellent transparency such as polyethylene terephthalate, polyvinyl chloride, polycarbonate, polyimide, cellulose triacetate, cellulose diacetate, polyethylene, and polypropylene as the base material,
An ink jet recording medium that can be used as a light transmitting recording medium such as a back print or an OHP sheet can be manufactured. The ink receiving layer obtained in the present invention has a very high transparency and can be suitably used for these media.

When the adhesive strength with the ink receiving layer formed on the surface of these substrates is insufficient, an undercoat layer can be applied, or various easy adhesion treatments such as corona discharge treatment can be applied. The thickness of the substrate is preferably 50 to 500 μm in consideration of the paper passing property of the printer.

As a single layer coating method, a known coating apparatus,
For example, a bar coater, a roll coater, a blade coater, an air knife coater, a gravure coater, a die coater, a curtain coater, and the like can be used, but are not limited thereto.

As a device used for the multilayer coating, a known coating device such as a slot die coater, a slide die coater, a curtain coater, a knife coater, a bar coater and the like can be mentioned. In the case of simultaneous coating, a dedicated multilayer slot die coater, multilayer slide die coater,
A simultaneous multi-layer coating device such as a multi-layer curtain coater can be preferably used, but is not limited thereto.

The coating amount is 1 to 60 g / weight as a weight after drying.
m ² is preferable, and more preferably 3 to 50 g / m ^2.
It is about. If the amount is less than 1 g / m ² , the ink absorption tends to be insufficient, and if the amount is more than 60 g / m ² , curling is likely to occur and the cost is increased, which is not preferable.

In order to suppress the curl of the ink jet recording sheet and improve the transportability, a back layer may be provided on the side of the base sheet opposite to the ink receiving layer. The configuration of the back surface layer and the accompanying easy adhesion treatment of the back surface of the base sheet can be selected according to the application, and are not particularly limited. However, in consideration of coating properties and costs, hydrophilic resins are mainly used. It is preferable to provide a back layer as a component.

In the present invention, as a method of irradiating an electron beam, for example, a scanning method, a curtain beam method, a broad beam method, or the like is employed, and an acceleration voltage of about 50 to 300 kV when irradiating the electron beam is appropriate. The irradiation amount of the electron beam is preferably adjusted in a range of about 0.1 to 20 Mrad. If it is less than 0.1 Mrad, it is insufficient to gel the coating layer, and irradiation exceeding 20 Mrad is not preferable because it may cause deterioration and discoloration of the base material and the coating layer.

The ink jet recording medium of the present invention has very high water resistance. Even when a water-soluble resin is used as a binder resin, the resin is cross-linked by electron beam irradiation to form a three-dimensional network. When printing is performed on this recording medium, the crosslinked resin portion in the ink receiving layer also swells by absorbing the ink and expands in volume, but the swelling speed is compared with the ink absorbing speed due to the capillary phenomenon of the entire ink receiving layer. Therefore, the ink absorption speed, which is an advantage of the pigment-based receiving layer, is not impaired.

[0045]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. In addition,% other than haze indicated in this example means weight percent.

[Method of Measuring Pore Volume of Fine Pigment] An aqueous dispersion of the fine pigment was dried at 105 ° C., and the obtained powder sample was subjected to gas adsorption method specific surface area / pore distribution measurement apparatus (Coulter).
(SA3100Plus type, manufactured by the same company) and pre-treatment was performed after vacuum degassing at 200 ° C. for 2 hours. The pore volume is the total pore volume (Tota) of pores having a pore diameter of 100 nm or less.
1 Pore Volume) was determined from the adsorption isotherm. [Method for Measuring Average Particle Size of Fine Pigment] Aqueous Dispersion 1 of Fine Pigment
00 ml into a 500 ml stainless steel cup, and T.K. K. Dispersion treatment (3000 rpm, 5 minutes) using a homodisper, 3
The secondary particles were pulverized and dispersed. The treated aqueous dispersion is sufficiently diluted with distilled water to prepare a sample solution, and a laser particle size analyzer (LPA3000 / 310, manufactured by Otsuka Electronics Co., Ltd.) by a dynamic light scattering method.
Using 0), the average particle size was measured. The average particle size used was a value calculated from analysis using the cumulant method.

[Production Method of Silica Sol A (Dispersion)] A synthetic amorphous silica having an average particle size of 3 μm (Nipsil HD-2, manufactured by Nippon Silica Co., Ltd., primary particle size = 11 nm) is dispersed in water. Then, after pulverized and dispersed by a sand grinder, a hydraulic ultra-high pressure homogenizer (Microfluidizer M11 manufactured by Mizuho Industry Co., Ltd.)
(0-E / H), and repeatedly pulverized and dispersed until the average particle diameter (average secondary particle diameter) measured by the above-mentioned average particle diameter measuring method reaches 168 nm, to obtain an 11% aqueous dispersion. The pore volume of silica in this aqueous dispersion was measured by the above-mentioned measuring method, and was found to be 1.2 ml / g. To 100 parts of the dispersion, 10 parts of an 11% aqueous solution of diallyldimethylammonium chloride / acrylamide copolymer (trade name: PAS-J-81) as an ink fixing agent was added,
The gelled mixture was further pulverized and dispersed by the same homogenizer to produce an aqueous silica dispersion having an average particle size of 422 nm.
This dispersion had a solid content of 11% and a silica concentration of 1%.
0%, and the diallyldimethylammonium chloride / acrylamide copolymer concentration was 1%. When the pore volume was measured in a state containing the copolymer, it was 1.1 m
1 / g.

[Method for Producing Silica Sol B (Dispersion)] Silica having an average primary particle size of 7 nm (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 30) produced by a gas phase method
The 11% aqueous dispersion of 0) was dispersed three times with the hydraulic ultrahigh-pressure homogenizer used in the method for producing silica sol A. The pore volume of the silica in this aqueous dispersion was measured by the above-mentioned measuring method, and was 1.6 ml / g. The average particle size (average secondary particle size) was 228 nm. Dispersion 10
To 10 parts of 10 parts of an 11% aqueous solution of diallyldimethylammonium chloride / acrylamide copolymer used in the method for producing silica sol A was added, and the gelled mixture was further dispersed with the same homogenizer to obtain an average secondary particle size of 3%.
A 76 nm silica aqueous dispersion was prepared. This dispersion had a solids concentration of 11%, a silica concentration of 10%, and a diallyldimethylammonium chloride / acrylamide copolymer concentration of 1%. Further, the pore volume was measured in a state containing the copolymer, and it was 1.4 ml / g.

Example 1 100 parts of silica sol A was mixed with 23 parts of a 10% aqueous solution of saponified polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name: PVA-420) to obtain a 10.8% solid content paint. Base material thickness 100
μm transparent polyethylene terephthalate film (trade name: Lumirror 100-Q80D, manufactured by Toray Industries, Inc.)
A bar was applied on the top so that the coating amount by dry weight was 25 g / m ² . This was immediately irradiated with an electron beam having an acceleration voltage of 175 kV and an irradiation dose of 5 Mrad by an electron beam irradiation apparatus (Electron Curtain manufactured by ESI). When the coating surface after irradiation was touched, it was found that the coating material was a jelly-like solid and had become a hydrogel. This was dried at a temperature of 100 ° C. to produce an ink jet recording medium of the present invention. The state of the receiving layer of this ink jet recording medium, 75 °
Gloss, haze, water resistance, image quality after printing, ink drying property, and pore volume of the ink receiving layer were evaluated by the following methods. The method for forming the ink receiving layer is shown in Table 1, and the evaluation results are shown in Table 2. Was.

Evaluation Method of Inkjet Recording Material [State of Receptive Layer] The condition of the coating layer of the inkjet recording material was visually evaluated according to the following five grades. 5 points: no cracks / cracks 4 points: cracks in part of the coating layer 3 points: cracks in the entire surface of the coating layer 2 points: cracks have occurred in the entire surface Debris peels off when touching the surface 1 point: Cracks are generated on the entire surface, and the debris peels off naturally during drying

[75 ° gloss] 7 of ink jet recording medium
5 ° gloss was measured according to JIS standard P8142.

[Haze] The haze of an ink jet recording medium using a transparent substrate was measured in accordance with JIS K7105.

[Water Resistance] An ink jet recording medium cut into 10 cm square and weighed was immersed in 1 liter of water.
After 1 hour, the ink jet recording medium is taken out,
And then weighed. The dry weight reduction rate (%) of the ink receiving layer after immersion in water was used as a criterion for evaluating the water resistance of the ink jet recording medium.

[Image Quality] In the ink jet recording medium, the recommended print mode for super fine paper of an ink jet printer (manufactured by EPSON, PM-700C) was set to ISO.
-400 two kinds of images ("High-definition color digital standard image data ISO / JIS-SCID", p13, image name: fruit basket, p14, image name: candle, published by Japan Standards Association) The image quality was evaluated in the following five grades. 5 points: no overflow of ink, the boundary between colors is clear, and the solid portion is uniform. 4 points: There is no overflow of ink, but the color boundary is slightly blurred. 3 points: There is no ink overflow, but the solid portion is slightly uneven. 2 points: The ink is slightly overflowing. 1 point: The ink overflows and the image is broken.

[Ink Drying Property] An ink jet printer (manufactured by EPSON, PM-70)
0C) In the recommended print mode for super fine paper, solid colors of cyan, magenta, yellow, and black were printed. The PPC paper was pressed against the printed area by hand, and the presence or absence of ink transfer was visually inspected, the time until the transfer disappeared was measured, and the average value of each color was calculated. . 5 points: Immediately after printing, no transfer 4 points: Less than 1 minute 3 points: 3 minutes or more and less than 5 minutes 2 points: 5 minutes or more and less than 10 minutes 1 point: 10 minutes or more

[Method of Measuring Pore Volume of Ink Receiving Layer] The ink receiving layer was peeled off from the substrate with a cutter knife to obtain a sample. Using a gas adsorption method specific surface area / pore distribution measuring device (manufactured by Coulter, SA3100Plus type), this sample was measured after vacuum degassing at 200 ° C. for 2 hours as a pretreatment. The pore volume used was a value obtained by determining the total pore volume (Total Pore Volume) of pores having a pore diameter of 100 nm or less from an adsorption isotherm.

<Example 2> A paint having a solid content of 10.8% was prepared by mixing 100 parts of silica sol A with 23 parts of a 10% aqueous solution of cationically saponified polyvinyl alcohol (trade name: CM-318, manufactured by Kuraray Co., Ltd.). The ink jet recording medium of the present invention was manufactured and evaluated in the same manner as in Example 1 except that the above was used. Table 1 shows the ink receiving layer forming method, and Table 2 shows the evaluation results.

Example 3 A coating having a solid content of 10.0% was prepared by mixing 33 parts of a 7% aqueous solution of completely saponified polyvinyl alcohol (Kuraray Co., Ltd., trade name: PVA-140H) with 100 parts of silica sol A. An ink jet recording medium of the present invention was produced and evaluated in the same manner as in Example 1 except for the fact that the recording was performed. Table 1 shows the ink receiving layer forming method, and Table 2 shows the evaluation results.

<Example 4> Hydroxypropyl methylcellulose (Shin-Etsu Chemical Co., Ltd.) was added to 100 parts of silica sol A.
Manufacture and trade name: Metrolose 65SH-50, methoxyl group DS = 1.8, hydroxypropoxyl group MS = 0.1
Solid content concentration of 23 parts of 10% aqueous solution of 5).
An ink jet recording medium of the present invention was manufactured and evaluated in the same manner as in Example 1 except that 8% of the coating material was used. Table 1 shows the ink receiving layer forming method, and Table 2 shows the evaluation results.

<Example 5> Polyethylene oxide (manufactured by Sumitomo Seika Co., Ltd., trade name: PE) was added to 100 parts of silica sol A.
Solid content concentration 1 obtained by mixing 23 parts of a 10% aqueous solution of O-1)
An ink jet recording medium of the present invention was manufactured and evaluated in the same manner as in Example 1 except that 0.8% of the coating material was used.
Table 1 shows the ink receiving layer forming method, and Table 2 shows the evaluation results.

Example 6 Example 1 was repeated except that 100 parts of silica sol B was used instead of 100 parts of silica sol A.
Producing the ink jet recording body of the present invention in the same manner as
evaluated. Table 1 shows the ink receiving layer forming method, and Table 2 shows the evaluation results.

Example 7 An ink jet recording medium of the present invention was manufactured in the same manner as in Example 1 except that a polyethylene-based synthetic resin laminated paper was used as the base material. The ink jet recording medium was evaluated in the same manner as in Example 1 except that the haze was not measured. Table 1 shows the ink receiving layer forming method, and Table 2 shows the results.

<Example 8> 10% of the partially saponified polyvinyl alcohol used in Example 1 was added to 100 parts of silica sol A.
An ink jet recording medium of the present invention was manufactured and evaluated in the same manner as in Example 1 except that a coating material having a solid content of 10.7% mixed with 50 parts of an aqueous solution was used. Table 1 shows the ink receiving layer forming method, and Table 2 shows the evaluation results.

<Comparative Example 1> An attempt was made to produce a coating film in the same manner as in Example 1 except that drying was performed immediately after coating without irradiation with an electron beam. However, since the coating layer cracked during drying and the fragments spontaneously peeled off from the substrate, the evaluation could not be performed in the same manner as in Example 1 except that the state of the coating layer was visually evaluated. Table 1 shows the method for forming the ink receiving layer.
Table 2 shows the evaluation results.

<Comparative Example 2> An attempt was made to produce a coating film in the same manner as in Example 2 except that drying was performed immediately after coating without irradiation with an electron beam. However, since the coating layer cracked during drying and the fragments spontaneously peeled off from the substrate, the evaluation could not be performed in the same manner as in Example 1 except that the state of the coating layer was visually evaluated. Table 1 shows the method for forming the ink receiving layer.
Table 2 shows the evaluation results.

Comparative Example 3 An attempt was made to produce a coating film in the same manner as in Example 3 except that drying was performed immediately after coating without irradiation with electron beams. The coating layer cracked during drying,
Example 1 because the fragments did not peel from the substrate.
The evaluation was performed in the same manner as described above. Table 1 shows the ink receiving layer forming method, and Table 2 shows the evaluation results.

<Comparative Example 4> An attempt was made to produce a coating film in the same manner as in Example 4, except that drying was performed immediately after coating without irradiation with an electron beam. However, since the coating layer cracked during drying and the fragments spontaneously peeled off from the substrate, the evaluation could not be performed in the same manner as in Example 1 except that the state of the coating layer was visually evaluated. Table 1 shows the method for forming the ink receiving layer.
Table 2 shows the evaluation results.

Comparative Example 5 Preparation of a coating film was attempted in the same manner as in Example 5, except that drying was performed immediately after coating without irradiation with an electron beam. However, since the coating layer cracked during drying and the fragments spontaneously peeled off from the substrate, the evaluation could not be performed in the same manner as in Example 1 except that the state of the coating layer was visually evaluated. Table 1 shows the method for forming the ink receiving layer.
Table 2 shows the evaluation results.

<Comparative Example 6> An attempt was made to produce a coating film in the same manner as in Example 6, except that drying was performed immediately after coating without irradiation with an electron beam. However, since the coating layer cracked during drying and the fragments spontaneously peeled off from the substrate, the evaluation could not be performed in the same manner as in Example 1 except that the state of the coating layer was visually evaluated. Table 1 shows the method for forming the ink receiving layer.
Table 2 shows the evaluation results.

<Comparative Example 7> An attempt was made to produce a coating film in the same manner as in Example 7, except that drying was performed immediately after coating without irradiation with an electron beam. However, during the drying, the coating layer was cracked and debris peeled off from the base material, so that the evaluation could not be performed in the same manner as in Example 7 except that the state of the coating layer was visually evaluated. Table 1 shows the method for forming the ink receiving layer, and Table 2 shows the evaluation results.

<Comparative Example 8> An attempt was made to produce a coating film in the same manner as in Example 1 except that the coating was dried immediately after coating, and then irradiated with an electron beam having an acceleration voltage of 175 kV and an irradiation dose of 5 Mrad. However, the state where the coating layer cracked during drying and the splinters spontaneously separated from the substrate did not change even when irradiated with an electron beam. An evaluation could not be made in a similar manner. Table 1 shows the ink receiving layer forming method, and Table 2 shows the evaluation results.

<Comparative Example 9> 10% of the partially saponified polyvinyl alcohol used in Example 1 was added to 100 parts of silica sol A.
A coating film was produced and evaluated in the same manner as in Example 1 except that a coating material having a solid content of 10.3% mixed with 200 parts of an aqueous solution was used. Table 1 shows the ink receiving layer forming method, and Table 2 shows the evaluation results.

Comparative Example 10 100 parts of a 10% aqueous dispersion of colloidal silica (manufactured by Nissan Chemical Industries, trade name: Snowtex-O, particle size described in a catalog is 10 to 20 nm)
A coating film was produced and evaluated in the same manner as in Example 1, except that a coating material having a solid content of 10% was used in which 100 parts of a 10% aqueous solution of polyethylene oxide used in Example 5 was mixed. The average particle size measured by the dynamic light scattering method of the colloidal silica used in this comparative example was 54 nm, and the measured pore volume was 0.22 ml / g. Table 1 shows the ink receiving layer forming method, and Table 2 shows the evaluation results.

Comparative Example 11 100 parts of a 10% aqueous dispersion of fibrous alumina hydrate (catalyst AS-3, trade name: Cataroid AS-3, catalog size: 100 nm × 10 nm, manufactured by Katsushi Kasei Kogyo Co., Ltd.) was cured by electron beam. Pentaerythritol tetraacrylate (Shin Nakamura Chemical Co., Ltd., trade name NK)
Ester A-TMM-3) 1 part of solid content concentration 1
A coating film was produced and evaluated in the same manner as in Example 1 except that 0.9% of the coating material was used. The average particle size of the alumina hydrate used in this comparative example measured by the dynamic light scattering method was 788 n.
m, the measured pore volume was 0.57 ml / g. Table 1 shows the ink receiving layer forming method, and Table 2 shows the evaluation results. Comparative Example 12 A coating film was produced and evaluated in the same manner as in Example 1 except that the 10% aqueous solution of partially saponified polyvinyl alcohol used in Example 1 was used as a coating material. Table 1 shows the ink receiving layer forming method, and Table 2 shows the evaluation results. <Comparative Example 13> 100 parts of silica sol A was mixed with 1 part of polyethylene glycol diacrylate (trade name: NK Ester A-400: acryloyl equivalent: 254, manufactured by Shin-Nakamura Chemical Co., Ltd.) as an electron beam-curable compound.
An attempt was made to produce a coating film in the same manner as in Example 1 except that 9% of the coating material was used. However, since the coating layer cracked during drying and the fragments spontaneously peeled off from the substrate, the evaluation could not be performed in the same manner as in Example 1 except that the state of the coating layer was visually evaluated. Table 1 shows the method for forming the ink receiving layer.
Table 2 shows the evaluation results.

[0075]

[Table 1]

[0076]

[Table 2]

In Tables 1 and 2, transparent PET was used.
Is a transparent polyethylene terephthalate film, laminating paper is a polyethylene synthetic resin laminated paper, PVA is polyvinyl alcohol, HPMC is hydroxypropyl methylcellulose, PEO is polyethylene oxide, AT
MM-3 is pentaerythritol tetraacrylate,
A-400 represents polyethylene glycol diacrylate. In Table 1, the number of parts of the resin added is the solid content 1 of the pigment.
The number of solid content addition parts is shown with respect to 00 parts. The numerical value of water resistance is a rate of decrease in dry weight of the ink receiving layer. In the case of using a polyethylene-based synthetic resin-laminated paper as the substrate (Example 7, Comparative Example 7), haze was not evaluated because the substrate was opaque.

As is clear from Examples 1 to 8 in Table 2,
The ink jet recording medium of the present invention, even when a fine pigment which is apt to crack is used as a raw material, becomes a coating layer without cracks, has high water resistance due to a crosslinked structure, and has a very low dry weight reduction rate when immersed in water. Was small. Furthermore, the image quality and ink drying property when printing with an ink jet printer were also extremely high because of the characteristics of the fine pigment-based receiving layer. In particular, when a uniform fine pigment having a small secondary particle diameter and a uniform particle size was used as in Example 6, a coating layer having extremely high gloss and high transparency could be obtained. Further, even when polyethylene-based synthetic resin laminated paper is used as the base material as in Example 7, it is possible to obtain a fine pigment layer with a high coating amount by one-coating without performing a special surface smoothing treatment. done.

On the other hand, immediately after the aqueous paint used in Examples 1, 2, 4 to 7 was applied to the substrate, drying was immediately performed. When the coating layer was dried, the coating layer cracked during drying, and debris spontaneously separated from the substrate. As a result, a coating film usable as an ink jet recording medium was not obtained (Comparative Examples 1, 2, 4 to 7). Irradiation of the coating film with an electron beam did not change the appearance of the coating film, and a coating layer without cracks was not obtained (Comparative Example 8). When the aqueous paint used in Example 3 was dried immediately after being applied to the substrate, the fragments were not spontaneously peeled off during drying, probably because the completely saponified polyvinyl alcohol used had a very high molecular weight. However, cracks easily observed visually occurred on the entire surface of the coating layer, which not only resulted in an unsuitable appearance as an ink jet recording medium, but also spread ink along the cracks when printing. The printed image was greatly broken. Furthermore, when the coating film was immersed in water, a part of the coating layer was peeled off and dispersed in water (Comparative Example 3).
When the amount of the binder resin was larger than that of the pigment, no problem occurred in the appearance of the coating film, but the pores of the pigment were filled with the resin and the porous ink receiving layer was not formed, so that the capillary was not used. No ink was absorbed due to the phenomenon, and the image quality and ink drying property were significantly reduced (Comparative Example 9). Even when commercially available colloidal silica was used as the pigment and the binder resin was added in an amount of 100 parts per 100 parts of the colloidal silica, the porous ink receiving layer was not formed, and the image quality and ink drying property were significantly reduced (Comparative Example 10). . When alumina hydrate is used as the pigment and pentaerythritol tetraacrylate, which is an electron beam-curable compound, is added to the alumina hydrate in place of the binder resin, the phase of the pigment and the electron beam-curable compound is reduced. Due to poor solubility, the entire coating layer could not be gelled even when irradiated with an electron beam, and even after drying, some of the coating layer cracked or peeled off, resulting in an unsuitable appearance as an inkjet recording medium. became. Furthermore, because the curing of the electron beam curable compound was insufficient, when printing with an inkjet printer,
There was also a portion where the image blurred (Comparative Example 11). When a resin-based receiving layer was used without using fine pigments, the appearance of the receiving layer was good, but no pores were formed inside the receiving layer. And the ink drying property was significantly reduced (Comparative Example 12). Comparative Example 1
When an electron beam-curable compound having a high hydrophilicity such as 3 was used, there was no problem with the compatibility with the pigment, but the strength of the gel obtained by electron beam irradiation was very weak.
The coating layer cracked during drying.

[0080]

According to the present invention, a good ink receiving layer free of cracks can be formed even when a fine pigment having a large pore volume, which easily causes cracks during coating, is used. In particular, a fine pigment having a pore volume of 1.0 ml / g or more is used, and the amount of the hydrophilic resin is minimized.
Even if 0 g / m ² or more is applied by one coating, an ink receiving layer without cracks can be formed. The ink jet recording medium provided with the ink receiving layer on the base material has excellent gloss, transparency and water resistance, and also has good image quality and ink drying property.

Claims (7)

[Claims] 1. An ink jet recording medium having one or more coating layers on a substrate, wherein at least one layer comprises (a)
The average particle size is 1 μm or less and the pore volume is 0.4 to 2.5 ml
/ G of a fine pigment and (b) a hydrophilic resin having no radically polymerizable unsaturated bond and forming a hydrogel by irradiating an aqueous solution with an electron beam.
A water-based paint containing the above-mentioned (b) in an amount of 1 to 100 parts by weight with respect to 0 parts by weight is applied, and then the applied layer is hydrogelled by irradiating with an electron beam and then dried to form a porous layer. Ink-jet recording material which is a high quality ink receiving layer. 2. An ink jet recording medium having one or more coating layers on a substrate, wherein at least one of the ink jet recording bodies comprises (c)
A fine pigment having an average particle size of 1 μm or less and (d) a hydrophilic resin having no radically polymerizable unsaturated bond and forming a hydrogel by irradiating an aqueous solution with an electron beam,
(D) 1 to 10 with respect to 100 parts by weight of (c).
A water-based paint containing 0 parts by weight is applied, and then the applied layer is hydrogelled by irradiating an electron beam, and then dried to form a pore volume of 0.2 to 2.0 ml / g. An ink-jet recording material which is a porous ink-receiving layer. 3. The ink jet recording medium according to claim 1, wherein a reduction rate of the dry weight of the ink receiving layer after immersion in water for 1 hour is 10% or less. 4. It does not have a radical polymerizable unsaturated bond,
A hydrophilic resin that forms a hydrogel by irradiating an aqueous solution with an electron beam includes polyvinyl alcohol, polyethylene oxide, polyalkylene oxide, polyvinylpyrrolidone, water-soluble polyvinyl acetal, poly-N-vinylacetamide, polyacrylamide, and polyacryloyl. At least one selected from the group consisting of morpholine, polyhydroxyalkyl acrylate, polyacrylic acid, hydroxyethylcellulose, methylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, gelatin, casein, their water-soluble derivatives, and their copolymers The inkjet recording material according to any one of claims 1 to 3, wherein 5. It does not have a radical polymerizable unsaturated bond,
The inkjet recording material according to claim 4, wherein the hydrophilic resin that forms a hydrogel by irradiating the aqueous solution with an electron beam is a cationic derivative. 6. The ink-jet recording medium according to claim 1, wherein the fine pigment is at least one selected from the group consisting of silica, aluminum hydroxide, boehmite, pseudo-boehmite, and alumina. 7. The ink jet recording material according to claim 1, wherein the fine pigment is a secondary particle having an average particle size of 8 to 800 nm formed by agglomeration of primary particles having an average particle size of 3 to 40 nm.