JP2007069452A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an inkjet recording medium with less amount of coating and with both a high gloss and high ink absorbing properties. <P>SOLUTION: The inkjet recording medium is manufactured by coating a substrate with a sub-layer comprising a water-absorbing inorganic pigment, a latex and boric acid or its salt, and a top layer comprising a sub-micron pigment and polyvinyl alcohol, and performing a cast processing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording medium, and more particularly to an ink jet recording medium having high gloss and sufficient ink absorbency even when the coating amount is small.

  In recent years, the technology of inkjet printers has advanced rapidly, and it has become possible to obtain recorded matter having an image quality equivalent to or higher than that obtained by a general silver salt photography method. Along with this, there is a demand for ink jet recording media having the same texture as photographic paper used in silver salt photography.

  Conventionally, cast coated paper as proposed in Patent Documents 1 and 2 has been used as an inkjet recording medium having gloss. However, although the recording medium manufactured by these techniques has a certain level of gloss, it cannot be said that the recording medium has a texture equivalent to that of photographic paper used for silver salt photography.

  In patent document 3, in order to solve this subject, it is proposed to harden a coating layer with an electron beam. However, a curing apparatus using an electron beam is generally large and has a problem that its maintenance and adjustment are extremely complicated.

  As another technique for the same purpose, in Patent Document 4, a lower layer composed of a pigment and a binder is applied, then an intermediate layer containing boric acid is provided, and a submicron pigment and boric acid such as polyvinyl alcohol are formed thereon. An ink jet recording medium having an upper layer made of a binder to be crosslinked has been proposed.

However, when an inkjet recording medium is manufactured by the technique of Patent Document 4, it is necessary to provide a very thick coating layer in order to obtain sufficient gloss and ink absorbability. A coating layer of 35 g / m ^{2 in} total is provided for the upper layer. When a large amount of coating is provided on the substrate, not only is it difficult to obtain high productivity due to an increase in drying load in the coating process, but the strength of the recording medium is low, that is, the recording medium is bent. In such a case, there is a problem that the coating layer is easily detached from the base material, and the user is forced to handle with care as compared with the recorded material by the silver salt photography method.
JP-A-63-264391 Japanese Patent Laid-Open No. 2-27487 JP 2004-330725 A Japanese Patent Laid-Open No. 2003-231342

  An object of the present invention is to provide an inkjet recording medium that has been difficult to realize in the past, has a small coating amount, and has high gloss and sufficient ink absorbability.

  As a result of studying this problem, the ink jet recording medium of the present invention, that is, an air-permeable support, an undercoat coating composition containing a water-absorbing inorganic pigment, latex, boric acid or a salt thereof, and submicron Provided is an inkjet recording medium in which an upper layer coating composition containing a pigment and polyvinyl alcohol is sequentially applied and cast, and the coating amount is at least high gloss and sufficient ink absorbency. It became possible to do.

  Furthermore, by using wet synthetic silica as the water-absorbing inorganic pigment of the lower layer coating composition, it has become possible to obtain an ink jet recording medium having excellent ink absorbency even with a small coating amount.

  Furthermore, since the lower layer coating composition contains colloidal silica, it is possible to obtain an ink jet recording medium particularly excellent in ink absorbability.

  According to the present invention, an ink jet recording medium having a high gloss and sufficient ink absorptivity, which has not been obtained conventionally, is obtained.

  In the present invention, paper is usually used as the air-permeable support, but a support other than paper, such as a nonwoven fabric, can be used as necessary.

  In the present invention, the lower layer refers to a coating layer formed on the side closer to the support of the recording medium, and the lower layer coating composition refers to a liquid composition for drying to form a lower layer. In the present invention, the upper layer refers to a coating layer formed on the side closer to the surface of the recording medium, and the upper layer coating composition refers to a liquid composition for drying to form an upper layer. These coating compositions are usually used in the form of an aqueous liquid in which each material is dissolved or dispersed in water. In the present invention, the lower layer and the upper layer are usually adjacent to each other, but one or two or more intermediate layers may be provided between the lower layer and the upper layer, as long as the interaction between the lower layer and the upper layer is not strongly inhibited. One or two or more coating layers may be provided between the lower layer and the support and on the upper surface side.

  In the present invention, the cast treatment refers to pressing a coated layer in a wet state onto a heated mirror surface, transferring the mirror surface shape to the surface of the coating layer, and removing moisture from the coated layer to dry the recording medium. Say the process to give. The apparatus used for the casting process (casting apparatus) is usually an apparatus having a structure in which the coated paper is continuously crimped to the surface of the cylinder whose surface is chrome-plated using an elastic roll. A device having another structure having the same action may be used. The so-called rewetting method, in which the coating method used in producing the ink jet recording medium of the present invention is coated, dried once after coating, and then re-applied with water, and then pressure-bonded to the mirror surface of the casting apparatus, upper layer Examples of the method such as a so-called direct method in which the coating composition or the coating composition of the upper and lower layers is applied to the mirror surface of the casting apparatus without being dried can be exemplified, but are not limited thereto. is not.

  In the present invention, the water-absorbing inorganic pigment means that water is used in place of linseed oil, and when a test according to the test method for the amount of oil absorption defined in JIS K 5101 is performed, 100 mL or more of water per 100 g by the end point. Examples of inorganic pigments used include heavy calcium carbonate, light calcium carbonate, wet synthetic silica, diatomaceous earth, calcium silicate, talc, magnesium hydroxide, halloysite, activated clay, acid clay, hydrotalc. Site, alumina hydrate, aluminum hydroxide, bentonite clay, zeolite, kaolin, calcined kaolin, gypsum, titanium oxide, barium sulfate and the like. One of these pigments may be used alone, or two or more thereof may be used in combination.

  Among such water-absorbing inorganic pigments, wet synthetic silica is particularly preferably used because an inkjet recording medium having good ink absorbability can be obtained even with a small coating amount. In the present invention, wet synthetic silica refers to porous silicon dioxide obtained by mixing a silicate such as sodium silicate and an acid such as sulfuric acid, followed by steps such as washing, aging and pulverization. As the production method, a precipitation method and a gel method are known, and any of them can be preferably used for the lower layer coating composition of the present invention.

  The oil absorption amount of the wet synthetic silica used in the lower layer coating composition of the present invention is preferably higher from the viewpoint of ink absorbency. On the other hand, if the oil absorption amount is too high, the strength of the coating layer may decrease. Absent. Specifically, the oil absorption amount of the wet synthetic silica used in the lower layer coating composition of the present invention is preferably 1 to 5 mL / g, and more preferably 2 to 4 mL / g. Moreover, since the particle size of the wet synthetic silica used for the lower layer coating composition of the present invention is too small, the viscosity of the coating composition becomes high and the coating operation may be difficult. The gloss of the recording medium after the casting process is not preferable because it may be difficult to express. Specifically, the particle size of the wet synthetic silica used in the lower layer coating composition of the present invention measured by the Marvin method is preferably 2 to 20 μm, more preferably 3 to 15 μm.

The amount of boric acid or its salt added to the lower coating composition of the present invention depends on the pH of the coating composition, but if it is too small, cracks will occur in the upper layer after drying and the gloss will decrease. If the amount is too large, the strength of the coating layer may be reduced. Therefore, the water-absorbing inorganic pigment is converted to H ₃ BO _{3 based} on the boron atom, and the content is 0.2 to 10 mass%. It is more preferable, and it is more preferable to set it as 0.4-5 mass%.

In the present invention, it is preferable that the lower layer contains colloidal silica because an ink jet recording medium having excellent ink absorbability can be obtained. In the present invention, colloidal silica is a method in which an acid such as sulfuric acid is allowed to act on an aqueous silicate solution such as sodium silicate, or a metal ion is removed by a cation exchange resin and then a process such as aging is performed. It is an aqueous dispersion of a silicate polymer to be produced, and is usually composed of spherical silicate particles having a specific surface area of 15 to 700 m ² / g by BET method.

As the colloidal silica used in the present invention, if the specific surface area is too small, the gloss after casting may be difficult to express, and if the specific surface area is too large, the ink absorbency is reduced. Since the effect of improving may not be sufficient, those having a specific surface area by the BET method of 50 to 500 m ² / g are preferably used, and those having a specific surface area of 100 to 350 m ² / g are more preferably used. In addition, if the amount of colloidal silica added in the present invention is too small, the effect of improving ink absorbency may not be sufficient, and if it is too large, gloss after casting may be difficult to express. It is preferable to set it as 10-100 mass% with respect to the addition amount of, and it is more preferable to set it as 15-60 mass%.

  In the present invention, latex refers to a liquid material in which a substantially water-insoluble thermoplastic polymer compound is dispersed in water, and once dried, the latex is substantially insoluble in hot water. Is distinguished from the aqueous solution. Examples include vinyl acetate polymer, ethylene-vinyl acetate copolymer, (meth) acrylic ester polymer, styrene- (meth) acrylic ester copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene. Copolymers, isoprene copolymers, chloroprene copolymers, urethane-based polymers, copolymers in which two or more of the monomers constituting these polymers are combined in a random, graft or block manner, etc. And an aqueous dispersion of the synthetic polymer compound, natural rubber latex, and the like. One of these latexes may be used alone, or two or more thereof may be used in combination.

  In the present invention, the amount of latex added to the lower layer coating composition is too small, the resulting recording medium may not have sufficient mechanical strength, if too large, the ink absorbency may be insufficient, Since the gloss after the cast treatment may not be sufficiently obtained, the mass ratio of latex / (water-absorbing inorganic pigment + colloidal silica) is preferably 10/100 to 60/100, and 15/100 to 40 / More preferably, it is 100.

  A water-soluble polymer compound such as a vinylpyrrolidone polymer, a (meth) acrylic acid polymer, or a (meth) acrylamide polymer is added to the lower layer coating composition of the present invention to such an extent that the effects of the present invention are not impaired. You can also. However, it is preferable that the water-soluble polymer compound having high crystallinity such as polyvinyl alcohol is not substantially contained since the gloss of the ink jet recording medium obtained after the casting treatment is remarkably lowered.

  In the present invention, the submicron pigment means that when the dispersion is dispersed on a substrate and observed with a scanning electron microscope, 80% or more of the area occupied by the particles in the observation field is composed of particles having a long side of 1 μm or less. It refers to the occupied inorganic pigment. The type of submicron pigment used in the upper layer coating composition of the present invention is not particularly limited, but examples include gel method silica, precipitation method silica, colloidal silica, gas phase method silica, gas phase method alumina, and pseudoboehmite. it can. In particular, it is preferable to use an inorganic pigment in which particles having a long side of 400 nm or less occupy 80% or more of the area occupied by the particles in the observation field because particularly high surface gloss can be obtained. Further, when an inorganic pigment occupying 80% or more of the area occupied by the particles in the observation field and particles having a long side of 100 nm or more is used, the coating layer is torn even if the upper coating composition is dried at high speed after coating. It is preferable because defects such as

As the submicron pigment used in the upper layer coating composition of the present invention, a pigment having a specific surface area of a certain level or more is preferable because a high printing density can be obtained. On the other hand, if the specific surface area is too large, the ink absorptivity may be lowered, which is not preferable. Specifically, it is preferable to use one having a specific surface area of 60 to 600 m ² / g by the BET method, and more preferably 150 to 400 m ² / g. In addition, the pigment having such a specific surface area is usually a pigment formed by forming a higher order structure in which primary particles having a diameter of several tens of nm or less are combined and voids are formed inside the primary particles.

  In the present invention, when the rewetting method is used as a casting method, pseudoboehmite is preferably used as the submicron pigment of the upper coating composition because an ink jet recording medium having particularly high gloss can be obtained.

  As the polyvinyl alcohol used in the upper layer coating composition of the present invention, polyvinyl alcohol having various saponification degrees from 70 mol% to 100 mol% can be used, but when the rewetting method is used as the method of the casting process used in the present invention. It is preferable to use one having a saponification degree of 95 mol% or less because gloss is easily developed. Also, modified polyvinyl alcohol in which various functional groups such as silyl group, carboxyl group, amino group, and acetoacetyl group are introduced, and other monomers such as ethylene are introduced randomly, grafted, or in blocks are also used. Can do. If the amount of polyvinyl alcohol added in the present invention is too small, cracks may occur during drying, or the surface strength of the ink jet recording medium to be formed may be insufficient. On the other hand, if the amount of polyvinyl alcohol added is too large. This is not preferable because the ink absorbability may be lowered. Specifically, the addition amount of polyvinyl alcohol is preferably 2 to 40% by mass of the submicron pigment, and more preferably 5 to 25% by mass.

  Since the polyvinyl alcohol of the upper coating composition of the present invention has a higher viscosity of the aqueous solution, cracking is less likely to occur when the coated coating composition is dried even if the addition amount is relatively small. The amount added can be reduced, and as a result, the ink absorbability can be improved, which is preferable. However, if the viscosity of the aqueous solution is too high, the viscosity of the coating composition obtained according to the present invention becomes too high, which may make the coating operation difficult. Specifically, the viscosity of an aqueous solution having a solid content concentration of 4% by mass measured at 25 ° C. using an Ubbelohde viscometer based on JIS Z8803 is preferably 15 to 400 mPa · sec, and 30 to 200 mPa · sec. More preferably. One of these polyvinyl alcohols may be used alone, or two or more different in saponification degree, viscosity, modification, etc. may be used in combination.

  For each coating layer of the present invention, various additives such as a surfactant, an antifoaming agent, a thickening agent, a color adjusting agent, a fluorescent brightening agent, an antioxidant, and an ultraviolet absorber are added as necessary. It can also be added.

In the present invention, the method for coating the coating composition of each coating layer is not particularly limited, and is an air knife coater, blade coater, rod blade coater, bar coater, reverse roll coater, comma coater, gate roll coater, film transfer. Various coating methods such as a coater, a lip coater, a die coater, and a curtain coater can be used. Among these, the curtain coater has a high uniformity of the obtained coating layer, and furthermore, when the upper layer is applied, the coating composition hardly penetrates into the lower layer and gives a very good surface quality. It is preferably used for coating a work layer, particularly an upper layer coating composition. The amount of the coating composition of the present invention to be coated on the support is not particularly limited, but in order to achieve both ink absorbency and economy, each layer is usually 5 to 20 g / m ² as a solid content. It is preferable to apply 10 to 30 g / m ² in the total of both layers. However, particularly when it is required to absorb a large amount of ink, it may be preferable to apply a maximum of about 50 g / m ^{2 in} total for both layers.

  It is also possible to carry out the cast treatment after increasing the smoothness with a calender device such as a soft calender or a super calender after or after the lower layer coating composition or the upper layer coating composition is applied and dried. is there.

  In addition, a release agent such as an oily substance or an aqueous dispersion of an oily substance is added to the coating composition of the present invention for the purpose of improving the peelability from the mirror surface in the casting apparatus, or is applied prior to the casting treatment. When using the rewetting method as a casting method, it is preferable to add to the water used for the rewetting because stable production can be achieved over a long period of time. Examples of substances that can be used as a release agent in the present invention include higher alkylamines such as dimethyloctylamine and dimethyloctadecylamine or salts thereof, higher alkyl quaternary ammoniums such as trimethyloctylammonium chloride and trimethyloctadecylammonium chloride. Examples thereof include salts, higher carboxylic acids such as oleic acid, stearic acid and caprylic acid or salts thereof, higher alcohols such as octyl alcohol and octadecyl alcohol, liquid paraffin, polyethylene wax and silicone oil.

  Examples of the present invention will be described below. In the examples, unless otherwise specified, parts are parts by mass, and% is mass%.

[Example 1]
[Preparation of lower layer coating composition 1]
6 parts of sodium tetraborate decahydrate (0.97 parts in terms of H ₃ BO ₃ ) was dissolved in 350 parts of water, and 100 parts of wet synthetic silica (Fine Seal X-37B manufactured by Tokuyama Corporation) was added thereto. It was fully dispersed using a disperser having a post-saw blade. Next, 83.3 parts of styrene-butadiene (SBR) latex having a solid content of 48% (0623N manufactured by JSR Corporation) (40 parts as a nonvolatile content) was added and mixed to obtain a lower coating composition 1. In addition, about the wet synthetic silica used here, water was used instead of linseed oil, and when a test according to the oil absorption test defined in JIS K 5101 was performed, 300 mL of water per 100 g was obtained by the end point. Used.

[Preparation of Alumina Hydrate Sol]
Mix 299 parts of water with 1 part of acetic acid, add 100 parts of alumina hydrate having a pseudo-boehmite structure (Dispersal HP14 manufactured by Sasol Co., Ltd.), stir for 2 hours as it is, and peptize to obtain an alumina with a solid content concentration of 25%. A hydrated sol was obtained. When this dispersion was diluted 100 times with water, dispersed on a glass substrate and observed with a scanning electron microscope, 80% or more of the area occupied by particles in the observation field was occupied by particles having a long side of 100 to 400 nm. It was.

[Preparation of upper layer coating composition 1]
To 100 parts (solid content 25 parts) of the alumina hydrate sol obtained above, a 10% aqueous solution of polyvinyl alcohol (PVA235 manufactured by Kuraray Co., Ltd.) having a saponification degree of 88 mol% and a 4% aqueous solution having a viscosity of 95 mPa · s at 25 ° C. 20 parts (2 parts of solid content) were added to prepare an upper layer coating composition 1.

[Preparation of inkjet recording medium]
The lower layer coating composition 1 is coated on a base paper having a basis weight of 157 g / m ² (Diafoam manufactured by Mitsubishi Paper Industries Co., Ltd.) using an air knife coater so that the coating amount after drying is 10 g / m ^2. Then, it was dried using a hot air dryer. Next, after the obtained coated paper was treated using a soft calender, the upper layer coating composition 1 was coated using an air knife coater so that the mass after drying was 10 g / m ^2, and was heated and dried. It was dried using a machine. Furthermore, the obtained coated paper was processed using a soft calendar. The coated surface of the coated paper is wetted by contact with water for 5 seconds, and then pressure-bonded to a mirror surface chrome plating cylinder of a casting apparatus heated to a temperature of 95 ° C. at a linear pressure of 20 kN / m and a speed of 5 m / min, and then dried. The ink jet recording medium of Example 1 was produced by peeling from the cylinder later.

[Examples 2 to 10]
[Preparation of lower layer coating composition 2]
6 parts of sodium tetraborate decahydrate (0.97 parts in terms of H ₃ BO ₃ ) are dissolved in 350 parts of water, and colloidal silica having a BET specific surface area of 230 m ² / g and a non-volatile content of 40% (Nissan Chemical Industries) 25 parts (10 parts as non-volatile content) of Snowtex 40 manufactured by the company were added. Further, after adding 100 parts of wet synthetic silica (Fine Seal X-37B manufactured by Tokuyama Corporation), the mixture was sufficiently dispersed using a disperser having a saw blade. Next, 83.3 parts of SBR latex having a solid content of 48% (0623N manufactured by JSR) (40 parts in terms of nonvolatile content) was added and mixed to obtain a lower coating composition 2.

[Preparation of lower layer coating compositions 3 to 10]
Lower layer coating compositions 3 to 10 were prepared in the same manner as the lower layer coating composition 2 except that the blending ratio of each material was changed to that shown in Table 1.

[Preparation of inkjet recording medium]
Ink jet recording media of Examples 2 to 10 were produced in the same manner as the ink jet recording medium 1 except that the lower layer coating compositions 2 to 10 were used in place of the lower layer coating composition 1, respectively.

[Example 11]
An inkjet recording medium of Example 11 was produced in the same manner as Example 5 except that the coating amount after drying of the upper layer was 5 g / m ² .

[Example 12]
An inkjet recording medium of Example 12 was produced in the same manner as Example 5 except that the coating amount after drying of the upper layer was 20 g / m ² .

[Example 13]
As colloidal silica, instead of colloidal silica having a BET specific surface area of 230 m ² / g and nonvolatile content of 40%, colloidal silica having a BET specific surface area of 540 m ² / g and nonvolatile content of 20% (Snowtex XS manufactured by Nissan Chemical Industries, Ltd.) An ink jet recording medium of Example 13 was produced in the same manner as in Example 7 except that the solid content was the same.

[Example 14]
As colloidal silica, instead of colloidal silica having a BET specific surface area of 230 m ² / g and nonvolatile content of 40%, colloidal silica having a BET specific surface area of 290 m ² / g and nonvolatile content of 30% (Snowtex S manufactured by Nissan Chemical Industries, Ltd.) An inkjet recording medium of Example 14 was produced in the same manner as Example 7 except that the solid content was the same.

[Example 15]
As colloidal silica, instead of colloidal silica having a BET specific surface area of 230 m ² / g and nonvolatile content of 40%, colloidal silica having a BET specific surface area of 110 m ² / g and nonvolatile content of 48% (Snowtex 50 manufactured by Nissan Chemical Industries, Ltd.) An inkjet recording medium of Example 15 was produced in the same manner as Example 10 except that the solid content was the same.

[Examples 16 to 25]
[Preparation of vapor phase silica dispersion]
While stirring 392 parts of water, 8 parts of a 50% aqueous solution of a dimethyldiallylammonium chloride polymer having a viscosity of 400 mPa · s (solid content 4 parts), gas phase method silica (specific surface area 90 m ² / g by BET method) 100 Part was added and predispersed using a blade type disperser. The obtained preliminary dispersion was treated with a colloid mill to obtain a vapor phase silica dispersion having a solid concentration of 20.8%. When this dispersion was diluted 100 times with water, dispersed on a glass substrate and observed with a scanning electron microscope, 80% or more of the area occupied by the particles in the observation field was occupied by particles having a long side of 100 to 400 nm. It was.

[Preparation of upper layer coating composition 2]
To 100 parts of the vapor phase silica dispersion obtained above (20.8 parts solids), a saponification degree of 88%, a 4% aqueous solution of polyvinyl alcohol having a viscosity of 95 mPa · s at 25 ° C. (PVA235 manufactured by Kuraray Co., Ltd.) An upper layer coating composition was prepared by adding 30 parts of a 10% aqueous solution (3 parts solids).

[Preparation of inkjet recording medium]
On the base paper, the lower layer coating compositions 1 to 10 were each coated so that the mass after drying was 10 g / m ^2, and dried using a hot air drier. Subsequently, after processing the obtained coated paper using a soft calender, the upper layer coating composition 2 is coated so that the coating amount after drying is 8 g / m ^2, and before moisture is volatilized. The ink jet recording media of Examples 16 to 25 were produced by pressure-bonding to a mirror-chrome plating cylinder heated to 90 ° C. of a casting apparatus at a linear pressure of 20 kN / m and a speed of 5 m / min, and peeling from the cylinder after drying.

[Comparative Example 1]
[Preparation of lower layer coating composition 11]
2 parts of sodium hydroxide was dissolved in 350 parts of water, 100 parts of wet synthetic silica (Fukuseal X-37B manufactured by Tokuyama Co., Ltd.) was added thereto, and then sufficiently dispersed using a disperser having a saw blade. Next, 200 parts of a 12% aqueous solution of silyl-modified polyvinyl alcohol (R polymer 1130 manufactured by Kuraray Co., Ltd.) having a viscosity of 25 mPa · s and a saponification degree of 98.5% and a 4% aqueous solution was added and mixed to form a lower layer coating. A work composition 11 was obtained.

[Preparation of Intermediate Layer Coating Composition 1]
4 parts of sodium tetraborate decahydrate was added to 96 parts of water, and dissolved by stirring to prepare an intermediate layer coating composition 1.

[Preparation of inkjet recording medium]
^On the base paper (Diafoam made by Mitsubishi Paper Industries) having a basis weight of 157 g / m ² , the lower layer coating composition 11 is applied using an air knife coater so that the coating amount after drying becomes 10 g / m ^2. Then, it was dried using a hot air dryer. Next, after the obtained coated paper was processed using a soft calender, the intermediate layer coating composition 1 or 2 was applied such that the coating amount after drying was 0.2 g / m ² , respectively. It dried using the hot air type dryer. Furthermore, the upper layer coating composition 1 was applied using an air knife coater so that the mass after drying was 10 g / m ^2, and dried using a hot air dryer. Furthermore, the obtained coated paper was processed using a soft calendar. The coated surface of this coated paper was wetted by contact with water for 5 seconds, and then pressure-bonded to a mirror chrome plating cylinder heated to 90 ° C. at a linear pressure of 20 kN / m at a speed of 5 m / min. The ink jet recording medium of Comparative Example 1 was produced by peeling from the cylinder.

[Comparative Example 2]
[Preparation of Intermediate Layer Coating Composition 2]
2 parts of boric acid was added to 98 parts of water, and dissolved by stirring to prepare an intermediate layer coating composition 2.

[Preparation of inkjet recording medium]
In addition to coating the intermediate layer coating composition 2 instead of the intermediate layer coating composition 1 as the intermediate layer coating composition so that the coating amount after drying is 0.1 g / m ² , In the same manner as in Comparative Example 1, an inkjet recording medium of Comparative Example 2 was produced.

[Comparative Example 3]
An inkjet recording medium of Comparative Example 3 was produced in the same manner as Comparative Example 1 except that the coating amount after drying of the upper layer was 15 g / m ² .

[Comparative Example 4]
An inkjet recording medium of Comparative Example 4 was produced in the same manner as Comparative Example 1, except that the coating amount after drying of the upper layer was 20 g / m ² .

[Comparative Example 5]
An inkjet recording medium of Comparative Example 5 was produced in the same manner as Comparative Example 1, except that the coating amount after drying of the upper layer was 25 g / m ² .

[Comparative Example 6]
The inkjet recording medium of Comparative Example 6 was the same as Comparative Example 1 except that the coating amount after drying of the lower layer was 20 g / m ² and the coating amount after drying of the upper layer was 15 g / m ^2. Was made.

[Comparative Example 7]
An inkjet recording medium of Comparative Example 7 was produced in the same manner as Comparative Example 1, except that the coating amount after drying of the lower layer was 25 g / m ² .

[Comparative Example 8]
^On the base paper (Diafoam made by Mitsubishi Paper Industries) having a basis weight of 157 g / m ² , the lower layer coating composition 11 is applied using an air knife coater so that the coating amount after drying becomes 10 g / m ^2. Then, it was dried using a hot air dryer. Next, after the obtained coated paper was processed using a soft calender, the intermediate layer coating composition 1 was coated so that the coating amount after drying was 0.2 g / m ^2, and then dried with hot air. It was dried using a machine. Here, the upper layer coating composition 2 is applied so that the coating amount after drying is 8 g / m ^2, and before the moisture volatilizes, the mirror surface chrome plating cylinder heated to 90 ° C. of the casting apparatus is used. The ink jet recording medium of Comparative Example 8 was produced by pressure bonding at a linear pressure of 20 kN / m and a speed of 5 m / min, and peeling from the cylinder after drying.

[Comparative Example 9]
As the intermediate layer coating composition, the intermediate layer coating composition ² was applied in place of the intermediate layer coating composition 1 so that the coating amount after drying was 0.1 g / m ^2. In the same manner as in Comparative Example 8, an inkjet recording medium of Comparative Example 9 was produced.

[Comparative Example 10]
An inkjet recording medium of Comparative Example 10 was produced in the same manner as Comparative Example 8, except that the coating amount after drying of the upper layer was 25 g / m ² .

[Comparative Example 11]
The inkjet recording medium of Comparative Example 11 was the same as Comparative Example 8, except that the coating amount after drying of the lower layer was 20 g / m ² and the coating amount after drying of the upper layer was 15 g / m ^2. Was made.

[Comparative Example 12]
An inkjet recording medium of Comparative Example 12 was produced in the same manner as Comparative Example 8, except that the coating amount after drying of the lower layer was 25 g / m ² .

[Gloss evaluation]
The gloss was evaluated by measuring the image clarity having a good correlation with visual gloss. In addition, the measurement was performed using a Suga Test Instruments Co., Ltd. image clarity measuring device at a measurement angle of 45 ° and an optical comb width of 2.0 mm. In the measurement by this method, in general, a recording medium giving 60 or more image clarity has a high gloss feeling, and a recording medium giving 65 or more image clarity has a very high gloss feeling.

[Evaluation of ink absorbency]
Predetermined evaluation images were printed by a Seiko Epson PM-G800 inkjet printer, and the ink absorbability of each recording medium was classified into the following five stages based on the legibility of image details. A (very good), B (good), C (normal), D (acceptable), E (unacceptable)

[Evaluation of strength]
The state of the folded portion when the recording medium was bent once so that the coated surface was inward and expanded again, in particular, the broken state of the coated layer was classified into the following five stages. A (very good), B (good), C (normal), D (acceptable), E (unacceptable)

  Table 2 shows the image clarity, ink absorbability, and strength of the recording media obtained in each Example and each Comparative Example.

  By comparing each example and each comparative example, especially Examples 1 to 10 and Comparative Examples 1 and 2, Example 12 and Comparative Example 4, Examples 16 to 25 and Comparative Example 8, It can be seen that an ink jet recording medium having high gloss and sufficient ink absorbency can be obtained with a small coating amount. Although the conventional techniques, for example, Comparative Examples 5 and 10, were able to obtain the same level of gloss and ink absorbency as those obtained by this technique, when producing an inkjet recording medium using these techniques, Compared with the case of technology, a very large amount of coating is required, so that the productivity of such an ink jet recording medium is low and sufficient strength cannot be obtained.

  In addition, by comparing Example 1 and Examples 2 to 10, and Example 16 and Examples 17 to 25, the colloidal silica was included in the lower layer coating composition of the present invention, so that the ink absorbability was particularly excellent. It can be seen that an ink jet recording medium is obtained.

Claims (3)

  In an ink jet recording medium manufactured by providing at least a lower layer and an upper layer on a gas-permeable support and performing a cast treatment, the lower layer is formed from a coating composition containing a water-absorbing inorganic pigment, latex, boric acid or a salt thereof. An ink jet recording medium, wherein the ink jet recording medium is formed from a coating composition containing a submicron pigment and polyvinyl alcohol.   2. The ink jet recording medium according to claim 1, wherein the water-absorbing inorganic pigment of the lower layer coating composition is wet synthetic silica.   The ink jet recording medium according to claim 1 or 2, wherein the lower layer coating composition contains colloidal silica.