JP2006289779A - Sheet for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet for inkjet recording for which the stability of a coating solution for forming an ink accepting layer is greatly improved and which is improved in cracking of the ink accepting layer and excels in glossiness and ink absorbency and particularly in the image quality of an image in a low gradation part. <P>SOLUTION: The sheet for inkjet recording has the ink accepting layer containing inorganic particulates, a cationic polymer and a binder on a substrate. In the layer, polyglycerin having an average molecular weight of 400-1,000 and a hydroxyl value of 800-1,100 is used. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording sheet having an ink receiving layer containing inorganic fine particles, a cationic polymer and a binder on a support.

  The ink jet recording method is a method of forming an image by absorbing and adhering ink droplets ejected from a nozzle to a receiver, and the ink directly contains an anionic dye such as a dye or an acid dye with water. Those dispersed in a solvent having a main component are used. In particular, in the solvent, isopropyl alcohol, glycerin, glycols and the like are used in combination for the purpose of preventing clogging of the nozzle. Therefore, the receiving layer is required to have a function of quickly absorbing these solvents in the ejected ink droplets and fixing the dye.

Conventionally, highly absorbing organic materials such as polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, and polyethylene oxide have been used as the main component of the receiving layer for these absorptions. In order to improve the ink absorbability, recording density, image quality, etc. of the recording medium, for example, a method has been proposed in which inorganic fine particles such as amorphous silica are provided on a support together with a binder as an ink receiving layer (patent) Reference 1).
In order to improve the gloss and image quality of the recording material, a method using synthetic silica fine particles in the ink receiving layer has been proposed (Patent Document 2).
Further, Japanese Patent Application Laid-Open No. 2004-230619 (Patent Document 3) discloses an ink jet recording material characterized in that an ink receiving layer contains a water-soluble solvent having a boiling point of 100 ° C. or higher and a water-soluble polyvalent metal compound. Although described, there were problems in terms of stability of the coating liquid, ink absorbability, cracks, and the like.
Furthermore, Japanese Patent Application Laid-Open No. 11-216947 (Patent Document 4) describes an ink-jet receiver characterized by containing a glycerin component in the ink receiving layer. There was a problem in that an inorganic pigment was not used and the quick drying property was poor.
JP 2000-2111235 A JP 10-119423 A Japanese Patent Laid-Open No. 2004-230619 JP-A-11-216947

However, for example, a full-color inkjet recording image formed using the inkjet recording sheet described in Patent Document 1 is insufficient in terms of image quality, gloss, and ink absorbability of the inkjet recording sheet.
Further, in any of the above-described ink jet recording sheets, cracks are likely to occur on the surface of the ink receiving layer, which causes problems such as a decrease in glossiness of the sheet and a deterioration in image quality of the formed image. . In addition, the coating liquid for forming the ink receiving layer (ink receiving layer coating liquid) may have poor stability, such as thickening over time or generation of aggregates. The above problems occur, the ink receiving layer cracks, and the glossiness is reduced.

  The present invention greatly improves the stability of the coating liquid for forming the ink receiving layer and the cracks of the ink receiving layer, and is particularly excellent in image quality, glossiness, and ink absorptivity of images in low gradation parts. The purpose is to provide a sheet for use.

The inventors have found that the use of inorganic fine particles having an average primary particle diameter of 30 nm or less as the inorganic fine particles to be contained in the ink receiving layer further improves glossiness, ink absorbability, image quality, and the like.
However, when such inorganic fine particles and a cationic polymer are used in combination, aggregation of the inorganic fine particles, thickening of the coating liquid, and the like occur. For this reason, there is a problem in that the print density is lowered and the crack of the ink receiving layer that has been observed conventionally is more prominent, resulting in a decrease in glossiness and image quality.

  As a result of further studies, the present inventors have found that these problems can be solved by using polyglycerin having an average molecular weight of 400 to 1000 and a hydroxyl value of 800 to 1100 in the ink receiving layer. Has been found to be solved, and the present invention has been completed.

The present invention includes the following embodiments.
[1]
In an ink jet recording sheet having an ink receiving layer containing inorganic fine particles, a cationic polymer, and a binder on a support, the ink receiving layer has an average molecular weight of 400 to 1000 and a hydroxyl value of 800 to 1100. An ink jet recording sheet comprising polyglycerin.
[2]
The inkjet recording sheet according to [1], wherein the inorganic fine particles have an average primary particle size of 30 nm or less.
[3]
The ink jet recording sheet according to any one of [1] to [2], wherein the inorganic fine particles are vapor-phase process silica.
[4]
The sheet for inkjet recording according to any one of [1] to [2], wherein the inorganic fine particles are wet-process fine silica produced by condensing activated silicic acid.
[5]
[4] The ink jet recording sheet according to [4], wherein the wet method fine silica has a specific surface area of 100 to 400 m ² / g by BET method and a pore volume of 0.5 to 2.0 ml / g.
[6]
The cationic polymer has the following general formula (1) and / or (2):

〔式中、Ｘは酸残基を表す。〕
で表される少なくとも１種の構成単位（ａ１）と、下記一般式（３）：

[Wherein, X represents an acid residue. ]
And at least one structural unit (a1) represented by the following general formula (3):

〔式中、R¹は炭素数１〜１８のアルキル基、炭素数１〜１８のアルコキシル基、炭素数６〜１２のアリール基、またはベンジル基のいずれかを表す。〕
で表される少なくとも１種の構成単位（ａ２）とを含むポリマー（Ａ）である〔１〕に記載のインクジェット記録用シート。
〔７〕
前記インク受容層がさらに架橋剤を含有する〔１〕〜〔６〕のいずれかに記載のインクジェット記録用シート。
〔８〕
前記架橋剤がホウ素化合物である〔７〕記載のインクジェット記録用シート。
〔９〕
前記インク受容層中の、前記ホウ素化合物と前記カチオンポリマーとの質量比が、１：１〜１：１０である〔８〕記載のインクジェット記録用シート。
〔１０〕
前記支持体が耐水性支持体である〔１〕〜〔９〕のいずれかに記載のインクジェット記録用シート。
〔１１〕
前記耐水性支持体が、紙の両面がポリオレフィン樹脂で被覆された支持体である〔１０〕に記載のインクジェット記録用シート。
〔１２〕
前記インク受容層がキャスト処理されている〔１〕〜〔１１〕のいずれかに記載のインクジェット記録用シート。
〔１３〕
前記インク受容層上に、さらに、キャスト処理された光沢層を有する〔１〕〜〔１２〕のいずれかに記載のインクジェット記録用シート。
〔１４〕
前記インク受容層が、無機微粒子およびバインダーを含有する少なくとも１層のインク受容層を形成した後、該インク受容層上に、カチオンポリマーを含有する水溶液を塗工して水塗り層を形成し、該水塗り層上に、少なくとも１層の他のインク受容層を形成してなる複数のインク受容層から構成されている〔１〕〜〔１３〕のいずれかに記載のインクジェット記録用シート。
〔１５〕
前記カチオンポリマーを含有する水溶液が、さらに架橋剤を含有する〔１４〕記載のインクジェット記録用シート。

[Wherein, R ¹ represents an alkyl group having 1 to 18 carbon atoms, an alkoxyl group having 1 to 18 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a benzyl group. ]
The sheet for inkjet recording according to [1], which is a polymer (A) containing at least one structural unit (a2) represented by:
[7]
The ink jet recording sheet according to any one of [1] to [6], wherein the ink receiving layer further contains a crosslinking agent.
[8]
The sheet for inkjet recording according to [7], wherein the crosslinking agent is a boron compound.
[9]
The ink jet recording sheet according to [8], wherein a mass ratio of the boron compound and the cationic polymer in the ink receiving layer is 1: 1 to 1:10.
[10]
The sheet for inkjet recording according to any one of [1] to [9], wherein the support is a water-resistant support.
[11]
The sheet for inkjet recording according to [10], wherein the water-resistant support is a support having both sides of paper coated with a polyolefin resin.
[12]
The ink jet recording sheet according to any one of [1] to [11], wherein the ink receiving layer is cast.
[13]
The ink jet recording sheet according to any one of [1] to [12], further comprising a cast-treated gloss layer on the ink receiving layer.
[14]
After the ink receiving layer forms at least one ink receiving layer containing inorganic fine particles and a binder, an aqueous solution containing a cationic polymer is applied on the ink receiving layer to form a water-coating layer, The ink jet recording sheet according to any one of [1] to [13], comprising a plurality of ink receiving layers formed by forming at least one other ink receiving layer on the water-coating layer.
[15]
The sheet for inkjet recording according to [14], wherein the aqueous solution containing the cationic polymer further contains a crosslinking agent.

  According to the present invention, there is provided an ink jet recording sheet in which cracking of the ink receiving layer is improved, the image quality in the low gradation portion is improved, and glossiness, ink absorption and coating liquid stability are excellent.

Hereinafter, the present invention will be described in detail.
The ink jet recording sheet of the present invention has an ink receiving layer containing inorganic fine particles, a cationic polymer, a binder, and polyglycerin on a support.
≪Support body≫
As the support, a known ink jet recording paper can be appropriately used.
More specifically, as a support, for example, paper (acid paper, neutral paper, etc.), baryta paper, synthetic paper, plastic film, support (RC paper) coated with plastic on one or both sides of paper, paper And a non-woven fabric or a plastic film bonded to one or both sides with an adhesive.
Examples of the plastic film include polyolefin resins such as polyester and polypropylene, films such as nylon, and synthetic paper.

In order to obtain a clear image at a higher printing density, it is preferable to use a water-resistant support that does not allow ink to penetrate into the support.
As the water-resistant support, a support in which both sides of the paper are coated with a polyolefin resin is preferably used because a recorded image is close to photographic quality and a high-quality image can be obtained at low cost.
As will be described later, when the ink receiving layer is cast or when a cast gloss layer is provided on the ink receiving layer, paper (acidic paper, neutral paper, etc.), coated paper, baryta Absorbent supports such as paper can also be preferably used. In the case of an absorbent support, the water in the ink-receiving layer coating liquid escapes from the support during the casting process, which facilitates the casting process. In addition, ink absorbability and ink drying properties are good, and high-speed printability is excellent.

  Although there is no restriction | limiting in particular as thickness of a support body, For example, 100-400 micrometers is preferable.

≪Ink receiving layer≫
<Inorganic fine particles>
In the present invention, the ink receiving layer contains inorganic fine particles. In particular, by containing inorganic fine particles having an average primary particle size of 30 nm or less, an ink receiving layer having high transparency and excellent print density, gloss, ink absorbability and the like can be obtained. The average primary particle diameter of the inorganic fine particles is more preferably 3 to 15 nm.
In addition, the primary particle diameter as used in the field of this invention is a particle diameter (Martin diameter) observed with the electron microscope (SEM and TEM).

  Examples of the inorganic fine particle material to be contained in the ink receiving layer include zeolite, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium oxide, zinc oxide, zinc sulfide, and zinc carbonate. , Satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, silica, aluminum hydroxide, alumina, alumina hydrate, aluminosilicate, boehmite, pseudoboehmite, etc. In particular, silica, alumina, alumina hydrate and aluminosilicate are preferable, and silica is particularly preferable.

The inorganic fine particles preferably have a specific surface area of 100 m ² / g or more by the BET method. Although there is no upper limit to the specific surface area by the BET method, it is preferably about 1000 m ² / g or less. More preferably, it is 200-400 m < ² > / g.
The BET method referred to in the present invention is one of powder surface measurement methods by a gas phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from an adsorption isotherm.

  When the inorganic fine particles are aggregated particles (secondary particles) in which primary particles are aggregated, the average secondary particle diameter is not particularly limited, but is preferably 0.05 to 1.0 μm, more preferably 0.05 to 0.5 μm.

  The amount of inorganic fine particles used in the ink receiving layer is preferably about 20 to 90% by mass, more preferably about 30 to 80% by mass, based on the solid content of the ink receiving layer. In this range, there is no possibility that the coating strength of the ink receiving layer is lowered, the ink absorbability and the ink drying property are excellent, and a higher image quality is obtained.

In the present invention, as described above, silica is preferably used as the inorganic fine particles. Silica is roughly classified into natural silica obtained by pulverizing natural silica such as quartz and synthetic silica produced by synthesis. Synthetic silica is broadly classified into vapor-phase silica and wet silica. In the present invention, the wet method fine silica described later is preferably used among the vapor phase method silica and the wet method silica because high ink absorbability, transparency, and gloss can be obtained. Vapor phase silica is also called a dry method as opposed to a wet method, and is made by a flame hydrolysis method. Specifically, it is made by burning silicon tetrachloride with hydrogen and oxygen. In place of silicon tetrachloride, silanes such as methyltrichlorosilane and trichlorosilane may be used alone or mixed with silicon tetrachloride. Vapor phase method silica is commercially available as a powder having a very low bulk density.
When the aqueous dispersion of vapor phase silica is dried, it becomes porous silica gel, and the pore volume of the gel by the BET method is generally 1.2 to 1.6 ml / g. This pore volume is convenient for absorbing ink. However, cracks tend to occur during drying, and it is not easy to produce an ink receiving layer free of cracks.

As the wet method silica, silica by a precipitation method and silica by a gel method are known.
For example, as disclosed in JP-A-55-116613, the precipitated silica is produced by adding a mineral acid stepwise to an alkali silicate aqueous solution and filtering the precipitated silica.
The gel method silica is obtained by mixing a mineral acid with an alkali silicate solution, gelling, washing, and pulverizing.
Precipitated silica and gel silica are formed by combining primary particles of silica to form secondary particles, and there are many voids between the primary particles and between the secondary particles. In addition to being large, the property of scattering light is small, so a high printing density can be obtained.

  Further, as a wet process silica by a slightly special production method, for example, active silicic acid is condensed as described in US Pat. No. 2,574,902, JP-A No. 2001-354408, JP-A No. 2002-145609. There is fine silica (hereinafter, referred to as wet method fine silica) produced. Here, the active silicic acid refers to an aqueous silicic acid solution having a pH of 4 or less obtained by ion exchange treatment of an aqueous alkali metal silicate solution with a hydrogen cation exchange resin, for example.

The wet method fine silica described in US Pat. No. 2,574,902 prepares an aqueous solution of active silicate by treating a diluted aqueous solution of sodium silicate with a cation exchange resin to remove sodium ions. Part of the solution is stabilized by adding alkali to polymerize to form a liquid in which silica seed particles are dispersed (seed liquid), and the remaining portion of the active silicic acid aqueous solution (feed liquid) is maintained while maintaining alkaline conditions. It is produced by gradually adding silica to polymerize silicic acid and growing colloidal silica particles.
This fine silica has a feature that it has a diameter of 3 nm to several hundreds nm, does not undergo secondary aggregation, and has a very narrow particle size distribution. Usually, a product of 7 nm to 100 nm, which is called colloidal silica, is commercially available as an aqueous dispersion, and when used for an ink receiving layer, a receiving layer having extremely high gloss and high transparency can be obtained.

On the other hand, JP-A wet process fine silica 2001-354408 JP, "a specific surface area of 300m ² / g~1000m ² / g by the BET method, a pore volume of 0.4ml / g~2.0ml / g is a liquid in which silica fine particles are dispersed in a colloidal form, and after adding alkali to the seed liquid, a feed liquid composed of at least one selected from an aqueous solution of active silicic acid and alkoxysilane is added to the seed liquid. was added in small portions and wherein the growing the silica fine particles, BET method by a specific surface area of 100m ² / g~400m ² / g, average secondary particle diameter of 20nm~300nm and pore volume, is 0.5ml / G to 2.0 ml / g of silica fine particle dispersion in which silica fine particles are colloidally dispersed. "
Or "specific surface area by BET method at 300m ² / g~1000m ² / g, and a liquid silica fine pore volume is 0.4ml / g~2.0ml / g are dispersed in colloidal seed solution, To the seed solution, a mixture of at least one feed solution selected from active silicic acid aqueous solution and alkoxysilane and alkali is added little by little, or the feed solution and alkali are added little by little to grow silica fine particles. characterized thereby, BET specific surface area is 100m ² / g~400m ² / g, average secondary particle diameter of 20 nm to 300 nm, and a pore volume of 0.5ml / g~2.0ml / g A method for producing a silica fine particle dispersion in which silica fine particles are colloidally dispersed. "
The silica fine particles obtained by

Further, the wet method fine silica described in JP-A No. 2002-145609 is “a suspension containing an aggregate composed of silica fine particles by heating an aqueous solution containing at least one selected from activated silicic acid and alkoxysilane. Next, at least one selected from an aqueous solution containing active silicic acid in the presence of alkali and alkoxysilane was added little by little to the suspension to grow silica fine particles in the suspension. Thereafter, the suspension is wet pulverized, and a method for producing a silica fine particle dispersion ”
The silica fine particles obtained by

  The wet method fine silica disclosed in Japanese Patent Application Laid-Open Nos. 2001-354408 and 2002-145609 is a silica having both the advantages of precipitation method silica and gel method silica and the advantages of colloidal silica. This silica is a secondary particle in which primary particles of silica (for example, the above-described colloidal silica) are bonded, and it is easy to adjust the secondary particle diameter to be equal to or smaller than the wavelength of light. It is most preferably used in the present invention because an ink-receiving layer having excellent resistance can be easily produced. Hereinafter, these wet process fine silicas are referred to as secondary fine silicas.

Among these, in particular, the secondary fine silica obtained by the condensation method disclosed in JP-A-2001-354408 is directly related to the average secondary particle diameter (20 nm to 300 nm) and fineness, without depending on mechanical means. Secondary fine silica having a pore volume (0.5 ml / g to 2.0 ml / g) can be produced, and the particle size distribution is narrow, so that the obtained ink receiving layer has good transparency and gloss, which is preferable in the present invention. Can be used.
In the condensation method disclosed in Japanese Patent Application Laid-Open No. 2001-354408, as the active silicic acid, for example, an aqueous silicic acid solution having a pH of 4 or less obtained by ion exchange treatment of an alkali metal silicate aqueous solution with a hydrogen cation exchange resin. (Activated silicic acid aqueous solution) is preferably used.
The active silicic acid aqueous solution is preferably 1 to 6% by mass as SiO ₂ concentration, more preferably 2 to 5% by mass, and preferably pH 2 to 4.
The alkali metal silicate may be a commercially available industrial product, and more preferably a sodium water glass having a SiO ₂ / M ₂ O (where M represents an alkali metal atom) molar ratio of about 2 to 4. It is preferable to use it.
As a method for condensing active silicic acid, the above-mentioned active silicic acid aqueous solution is dropped into hot water, or the active silicic acid aqueous solution is heated to produce seed particles, before the dispersion is precipitated or gelled. the seed particles are stabilized by adding an alkali, then the preferred in terms of SiO ₂ with respect to SiO ₂ 1 mole contained in the seed particles of the active silicic acid solution while maintaining the stable state 0.001 It is preferable to add seed particles at a rate of mol / min to grow primary particles of the seed particles.

Moreover, it is preferable that the wet method fine silica has a specific surface area by BET method of 100 to 400 m ² / g and a pore volume of 0.5 to 2.0 ml / g. Fine silica in this range has a very good balance of cracks in the ink receiving layer, ink absorbency, and gloss.

Further, the ink-receiving layer has a silica-cationic compound obtained by pulverizing silica-cationic compound aggregate particles obtained by mixing and aggregating amorphous silica and a cationic compound to an average particle size of 0.7 μm or less. Aggregate fine particles are preferably used.
By using the silica-cationic compound aggregate fine particles, the ink receiving layer can be made into a porous layer having good transparency, ink absorbability, ink color development, weather resistance and the like.

The silica-cationic compound aggregate fine particles are a silica colloid particle solution composed of secondary particles substantially formed by aggregation of primary particles. In the case of silica sol in which primary particles are monodispersed (for example: general commercially available colloidal silica), the porous layer obtained by applying to the base material becomes relatively dense, and it is easy to lose transparency. In order to provide ink absorbency, a high coating amount is inevitable. However, when the coating amount is high, the coating film tends to crack, and the coating process tends to be complicated. Of course, primary particles may be partially contained in the silica colloid particle solution.
In the present invention, when silica-cationic compound aggregate particles are blended in the ink receiving layer together with a binder (particularly polyvinyl alcohol is preferred), the transparency of the printed part can be obtained, and a gloss equivalent to that of a photograph can be obtained. is there. Further, since the entire ink receiving layer is transparent, it can be used as an OHP sheet or the like.

Silica-cationic compound aggregate fine particles are obtained by pulverizing silica-cationic compound aggregate particles obtained by mixing and aggregating amorphous silica and a cationic compound to an average particle size of 0.7 μm or less. Is.
Silica-cationic compound aggregated fine particles refer to a state in which fine particles having an average particle size of 0.7 μm or less and a maximum particle size of about 1000 nm or less are uniformly dispersed.
Silica-cationic compound aggregated fine particles can be obtained by applying a strong force by mechanical means to a mixture of amorphous silica such as general commercially available synthetic amorphous silica (several microns) and a cationic compound. . That is, it can be obtained by a breaking down method (a method of subdividing a bulk material). The silica-cationic compound aggregate fine particles may be a slurry. Examples of the mechanical means include ultrasonic, high-speed rotary mill, roller mill, container drive medium mill, medium agitation mill, jet mill, cracker, sand grinder and the like.
The average particle diameter referred to in the present invention is a particle diameter observed with an electron microscope (SEM and TEM) (taken an electron micrograph of 10,000 to 400,000 times, and measured and averaged the diameter of the particles in a 5 cm square. (It is described in "Particle Handbook", Asakura Shoten, p52, 1991, etc.).

  The average particle diameter of the silica-cationic compound aggregate fine particles (substantially secondary particles) is 0.7 μm or less, preferably 10 to 300 nm, more preferably 20 to 200 nm. When silica-cationic compound aggregate fine particles having an average particle diameter exceeding 0.7 μm are used, the transparency is remarkably lost, the print density is remarkably lowered, and an ink jet recording sheet having high gloss after printing cannot be obtained. There is a fear. On the other hand, if silica colloidal particles having an extremely small average particle diameter are used, there is a possibility that a sufficient ink absorption rate cannot be obtained.

  The amorphous silica constituting the silica-cationic compound aggregate fine particles preferably has an average primary particle diameter of 3 nm to 40 nm. If it is less than 3 nm, the gap between the primary particles becomes extremely small, and the ability to absorb the solvent and ink in the ink is remarkably lowered. On the other hand, if it exceeds 40 nm, the aggregated secondary particles become large, and the transparency of the ink receiving layer may be lowered.

  As the cationic compound used in the silica-cationic compound aggregate fine particles, various known cationic compounds generally used in ink jet paper can be used, for example, monoallylamine salt, vinylamine salt, N-vinylacrylamidine salt. A primary amine type cationic polymer having a primary amine salt such as dicyandiamide / formalin polycondensate or dicyandiamide / polyethyleneamine polycondensate as a structural unit, or a secondary amine salt such as diallylamine salt or ethyleneimine salt as a structural unit Secondary amine type cationic polymer, tertiary amine type cationic polymer having a tertiary amine salt such as diallylmethylamine salt as a structural unit, diallyldimethylammonium chloride, (meth) acryloyloxyethyltrimethylammonium chloride Aluminum such as quaternary ammonium type cationic polymer, basic polyaluminum chloride, basic polyfatty acid aluminum, etc. having quaternary ammonium salts such as lide, (meth) acrylamidopropyltrimethylammonium chloride, dimethylamine / epichlorohydrin polycondensate Examples thereof include zirconyl compounds such as compounds, zirconyl chloride, basic zirconyl chloride and fatty acid zirconyl. In addition, as addition amount of a cationic compound, it is adjusted in the range of 1-30 mass parts with respect to 100 mass parts of amorphous silica, More preferably, it is 5-20 mass parts.

  In the present invention, when silica-cationic compound aggregate fine particles are used as the inorganic fine particles, PVA is most effective as a binder from the viewpoint of dispersion suitability and coating solution stability. In particular, in order to obtain dispersibility and ink absorbability, PVA having a polymerization degree of 2000 or more is preferably used. The degree of polymerization of PVA is more preferably 2000 to 5000. In order to obtain water resistance, PVA having a saponification degree of 95% or more is effective.

  The solid mass ratio of the silica-cationic compound aggregate fine particles and the binder is not particularly limited, but is adjusted to a range of 10/1 to 10/10, preferably 10/2 to 10/6. If the amount of the binder added is large, the pores between the particles may be small, and a sufficient ink absorption rate may not be obtained, while if the binder is small, the coating layer will crack and become unusable. It may be.

<Polyglycerin>
The average molecular weight of the polyglycerol used in the present invention is preferably 400 to 1000, and the hydroxyl value is preferably 800 to 1100. When the average molecular weight is larger than 1000, the stability of the ink receiving layer coating liquid tends to deteriorate, and the ink absorbability and image quality tend to deteriorate. When the average molecular weight is less than 400, water resistance and gloss tend to deteriorate. Further, when the hydroxyl value is larger than 1100, there are many hydroxyl groups per unit mass, and the water resistance after printing tends to deteriorate. When the hydroxyl value is less than 800, the stability of the ink receiving layer coating liquid tends to deteriorate, and the ink absorbability and image quality may deteriorate.
The average molecular weight of polyglycerol indicates a weight average molecular weight measured by a viscosity method, a chromatography method (GPC method) or the like. The hydroxyl value is calculated from 56110 × (degree of polymerization + 2) / weight average molecular weight.

<Cationic polymer>
As the cationic polymer used in the present invention, a known cationic polymer can be appropriately used. Preferably, the following general formula (1) and / or (2):

〔式中、Ｘは酸残基を表す。〕
で表される少なくとも１種の構成単位（ａ１）と、下記一般式（３）：

[Wherein, X represents an acid residue. ]
And at least one structural unit (a1) represented by the following general formula (3):

〔式中、Ｒ¹は炭素数１〜１８のアルキル基、炭素数１〜１８のアルコキシル基、炭素数６〜１２のアリール基、またはベンジル基のいずれかを表す。〕
で表される少なくとも１種の構成単位（ａ２）とを含むポリマー（Ａ）であるカチオンポリマーである。

[Wherein, R ¹ represents an alkyl group having 1 to 18 carbon atoms, an alkoxyl group having 1 to 18 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a benzyl group. ]
A cationic polymer that is a polymer (A) containing at least one structural unit (a2) represented by the formula:

The content of the cationic polymer in the ink receiving layer is preferably 0.01 to 10 g / m ² , more preferably 0.05 to 5 g / m ² . When used in this range, the image quality, image storability and ink absorption are excellent.

  The method for incorporating the cationic polymer used in the present invention into the ink receiving layer is not particularly limited, but it is added to the ink receiving layer coating solution, and the aqueous solution is applied before coating the ink receiving layer. Or a method of applying an aqueous solution after applying the ink receiving layer.

  When the cationic polymer is added to the ink receiving layer coating liquid, it can be used after forming silica-cationic compound aggregate fine particles together with silica as described above.

  When the ink receiving layer is formed of a plurality of layers, after forming at least one ink receiving layer (inner ink receiving layer), an aqueous solution containing the polymer (A) is formed on the inner ink receiving layer. It is preferable to apply at least one other ink receiving layer (outer ink receiving layer) by coating the coating liquid for ink receiving layer thereon. This method is effective for improving the heat and humidity resistance of the image, and has a high effect of suppressing cracking.

It is more preferable to use a crosslinking agent in the aqueous solution containing the polymer (A) from the viewpoint of suppressing cracks.
Specific examples of the crosslinking agent include, for example, boron compounds such as boric acid, borax, and borate, glyoxal, melamine / formaldehyde, glutaraldehyde, methylol urea, polyisocyanate compound, epoxy compound, aziridine compound, carbodiimide compound, dihydrazide A compound, an aluminum compound, a zirconium compound, etc. are mentioned. Of these, boron compounds are preferable, and borax is particularly preferable.
By applying a mixed liquid of borax and polymer (A), the heat and humidity resistance of the image is particularly high and the cracking suppressing effect is high.
Furthermore, since the pH of the mixed solution is adjusted to 7.0 to 10.0, preferably 7.5 to 9.0 with an alkali such as sodium hydroxide, it is more effective for cracking. ,preferable.

At this time, the coating amount of the crosslinking agent, preferably ^{0.01~2.0g / m 2, 0.05~1.0g / m} 2 is more preferable. If it is less than 0.01 g / m ² , the effect of preventing cracking will be low, and if it exceeds 2.0 g / m ² , cracking will occur due to strong shrinkage during drying of the ink receiving layer, or ink absorbability will be reduced. There is a fear.
Moreover, as mass ratio of a crosslinking agent and a polymer (A), 1: 1-1: 20 are preferable and 1: 1-1: 10 are more preferable. By setting the mass ratio within this range, an inkjet recording sheet excellent in cracking, aging resistance and ink absorbability can be obtained.

  In the present invention, it is possible to add various other known cationic polymers other than the cationic polymer within a range not inhibiting the present invention.

<Binder>
Examples of binders incorporated in the ink receiving layer include starch derivatives such as oxidized starch and etherified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, proteins such as casein, gelatin and soybean protein, and complete (partial) saponification. Polyvinyl alcohol, silicon-modified polyvinyl alcohol, polyvinyl alcohols such as acetoacetyl group-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, salts of styrene-maleic anhydride copolymer, styrene-butadiene latex, acrylic latex, polyester polyurethane latex , Water-based adhesives such as vinyl acetate latex, or polymethyl methacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer Polyvinyl butyral, and an organic solvent-soluble resins such as alkyd resin. These binders may be used alone or in combination.

  Among these binders, polyvinyl alcohols are preferable because they have high transparency, high water resistance, are nonionic, can be mixed with various materials, and have a relatively low swelling property near room temperature. In addition, there is an advantage that the ink does not swell at the initial permeation of the ink and does not block the gap.

  Among the polyvinyl alcohols, completely (partially) saponified polyvinyl alcohol, cation-modified polyvinyl alcohol or silicon-modified polyvinyl alcohol is particularly preferably used.

As the complete (partially) saponified polyvinyl alcohol, a partially saponified polyvinyl alcohol or a completely saponified polyvinyl alcohol having a saponification degree of 80% or more, particularly 95% or more is preferable. 000 is preferable, and 500 to 5,000 is more preferable.
The reason why a portion having a saponification degree of 80% or more or completely saponified polyvinyl alcohol is preferable is that it has excellent water resistance. The reason why the average degree of polymerization is preferably from 200 to 5,000 is that when a polymer having a degree of polymerization within this range is used, the viscosity is excellent in water resistance and easy to handle.

  The cation-modified polyvinyl alcohol is preferably polyvinyl alcohol having a primary, secondary, or tertiary amino group or a quaternary ammonium base in the main chain or side chain of the polyvinyl alcohol.

  The binder is used in an amount of preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by mass with respect to 100 parts by mass of the inorganic fine particles.

<Other ingredients>
In the present invention, it is preferable to use a crosslinking agent as described above together with the binder. Thereby, generation | occurrence | production of a crack can further be reduced and ink absorptivity, glossiness, an image quality, etc. improve further.
The cross-linking agent may be blended in the coating liquid for forming the ink receiving layer, or the cross-linking agent solution may be applied before the ink receiving layer is applied or after the ink receiving layer is applied.
The coating amount of the crosslinking agent, preferably ^{0.01~1.0g / m 2, 0.05~0.5g / m} 2 is more preferable. If it is less than 0.01 g / m ² , the effect of preventing cracking will be reduced, and if it exceeds 1.0 g / m ² , cracking may occur due to strong shrinkage during drying of the ink receiving layer, or ink absorbability will be reduced. There is a fear.

Furthermore, in the present invention, it is also possible to use a phosphorus oxoacid salt as a coating solution stabilizer. Specific examples thereof include alkali metal salts such as phosphoric acid, phosphorous acid, hypophosphorous acid, metaphosphoric acid, metaphosphorous acid, pyrophosphoric acid, pyrophosphorous acid, and polyphosphoric acid, alkaline earth metal salts, and ammonium salts. And zinc salts.
Of these, hypophosphite is preferably used because it has a particularly high effect on coating solution stability. Specific examples of hypophosphites include, for example, sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, magnesium hypophosphite, barium hypophosphite, ammonium hypophosphite, hypophosphorous acid. Zinc acid etc. are mentioned. Of these, sodium hypophosphite is particularly preferred because it has the highest effect on coating solution stability.

  In the ink receiving layer, various known pigment dispersants, thickeners, fluidity modifiers, antifoaming agents, antifoaming agents, mold release agents, foaming agents, penetrating agents, coloring dyes, coloring pigments, fluorescence Brightening agents, preservatives, antifungal agents and the like can be added as appropriate.

The ink receiving layer is formed by applying and drying the ink receiving layer coating liquid containing the various components described above on at least one surface of the support.
The coating amount of the ink receiving layer coating liquid is preferably ² to 50 g / m ² in terms of dry mass when the ink receiving layer is not the inner ink receiving layer and the outer ink receiving layer as described above, and 3 to 30 g. / M ² is more preferable. When the coating amount is within this range, the recording image quality and the coating film strength are excellent.
The ink receiving layer coating liquid can be applied by a coating method such as a bar coater, a blade coater, an air knife coater, a gravure coater, a die coater, or a curtain coater.

In addition, after the application of the ink receiving layer coating liquid, by performing a casting process while the coating layer is in a wet state, by directly casting the ink receiving layer, an ink jet recording sheet having a higher surface glossiness You can also
As a method for the casting treatment, there are a wet method, a gelation method, and a rewet method. In the wet method, while the coated layer is in a wet state, the coated layer is pressed against the heated mirror drum surface to perform a high gloss finish. In the gelation method, the coating layer is brought into contact with the gelling agent bath while the coating layer is in a wet state, and the coating layer in the gelled state is pressed against the surface of the heated drum to perform a high gloss finish. It is. In the rewetting method, a wet coating layer is once dried and then brought into contact with a wetting liquid again, and then pressed against the surface of a heated drum to perform a high gloss finish.
When the ink receiving layer is cast, it is preferable that a release agent is blended in the ink receiving layer. As the release agent, various publicly known release agents generally used in the coated paper field can be used.

  Furthermore, for the purpose of imparting high gloss after the ink receiving layer is formed, it is also possible to impart surface smoothness through the roll nip under pressure with, for example, a super calender, gloss calender, or soft calender.

≪Other composition≫
<Glossy layer>
In the present invention, a cast-treated gloss layer may be further provided on the above-described ink receiving layer. Thereby, it can be set as the inkjet recording sheet with higher surface glossiness.
The gloss layer is configured to contain a pigment and / or a resin.
The gloss layer is preferably porous or liquid-permeable so long as it does not impair the gloss so that the ink can pass or absorb quickly.

Examples of the pigment used in the gloss layer include those similar to the inorganic fine particles used in the ink receiving layer, but colloidal silica, amorphous silica, alumina, aluminosilicate in terms of gloss, transparency, and ink absorption. Zeolite, synthetic smectite and the like are preferable.
These pigments are desirably contained in the gloss layer in an amount of 10 to 90% by mass.
The average particle diameter of the pigment (in the case of aggregated particles, the diameter of the aggregated particles) is preferably 0.001 to 1 μm, and more preferably 0.005 to 0.5 μm. When the particle diameter is in this range, excellent ink absorbability, gloss and print density can be obtained.

  Examples of resins used for the gloss layer include water-soluble binders (for example, polyvinyl alcohols such as polyvinyl alcohol, cation-modified polyvinyl alcohol, silyl-modified polyvinyl alcohol, casein, soy protein, synthetic proteins, starch, cellulose such as carboxymethyl cellulose and methyl cellulose). Derivatives), styrene-butadiene copolymers, conjugated diene polymer latexes such as methyl methacrylate-butadiene copolymers, and water-dispersible resins such as vinyl copolymer latexes such as styrene-vinyl acetate copolymers, aqueous acrylics Various resins (adhesives) commonly used in the field of coated paper, such as resins, water-based polyurethane resins and water-based polyester resins, can be used alone or in combination.

When the gloss layer is formed mainly of a resin, the resin may be a polymer or copolymer obtained by polymerizing a monomer having an ethylenically unsaturated bond (hereinafter referred to as an ethylenic monomer). It is preferable that the main component is a combination. Furthermore, substituted derivatives of these polymers may be used.
In addition, the above ethylenic monomer is polymerized in the presence of colloidal silica to form a composite by Si—O—R (R: polymer component) bond, or colloidal silica such as SiOH group is added to the polymer. A functional group capable of reacting may be introduced and used in the form of a composite by reacting with colloidal silica. When such a composite is used, it tends to be excellent in gloss and ink absorbability.

  It is preferable that a release agent is further blended in the glossy layer. As the release agent, various publicly known release agents generally used in the coated paper field can be used.

  In addition, it is possible to add a cationic compound to the glossy layer to increase the print density, to improve water resistance, and to add various auxiliary agents to improve light resistance and gas resistance. is there.

The gloss layer is formed by coating the gloss layer coating liquid containing the above-mentioned various components on the ink receiving layer to form a coating layer, casting the coating layer, and drying the coating layer. The
The coating amount of the glossy layer coating liquid is preferably 0.1 to 30 g / ^{m 2} by dry weight, 0.2 to 10 g / ^{m 2} is more preferable. When the coating amount is within this range, the gloss, ink drying property and recording density are excellent.
The coating of the gloss layer coating liquid and the casting treatment can be performed in the same manner as described for the ink receiving layer.
The drying temperature of the gloss layer is also important. If the drying temperature is too high, film formation proceeds too much, resulting in a decrease in surface porosity, resulting in a decrease in ink absorption rate. Conversely, if the drying temperature is too low, gloss tends to be poor and productivity is also lowered. The drying temperature is preferably 50 to 150 ° C, more preferably 70 to 120 ° C.

  In the present invention, an intermediate layer is provided between the support and the ink receiving layer, a protective layer is provided on the back surface (the surface on which the ink receiving layer is not formed) of the support, and the back surface is further adhered to the back surface. It can be processed, and various known techniques in the field of inkjet recording sheet production can be added.

The liquid ink for forming a recorded image on the ink jet recording sheet of the present invention is a recording liquid composed of a colorant, a liquid medium, and other optional additives, and any commercially available liquid ink for ink jet recording is used. Can be used.
Examples of the colorant include various water-soluble dyes such as direct dyes, acid dyes, and reactive dyes, carbon black finely divided around 100 nm, and surface-treated with a resin, a surfactant, and the like, organic pigments, and the like.
The liquid medium includes water alone or a combination of water and a water-soluble organic solvent. Examples of water-soluble organic solvents include monohydric alcohols such as ethyl alcohol and isopropyl alcohol, 1,2-hexanediol, polyhydric alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol, and glycerin, triethylene glycol monomethyl ether, and triethylene glycol. And lower alkyl ethers of polyhydric alcohols such as monoethyl ether.
Among them, the pigment ink contains 1,2-hexanediol and glycerin as water-soluble organic solvents in the pigment ink, and the total of both is 80% or more of the water-soluble solvent, and the inkjet recording sheet of the present invention. This combination is suitable from the standpoint of suitability for pigment ink, particularly scratch resistance.
Examples of the additive include a pH adjuster, a metal sequestering agent, an antifungal agent, a viscosity adjuster, a surface tension adjuster, a surfactant, and a rust preventive agent.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. In the examples, “parts” and “%” respectively indicate parts by mass and mass% unless otherwise specified.

Example 1
(Preparation of coating liquid A for ink receiving layer)
Gas phase method silica (trade name: Aerosil 300, manufactured by Nippon Aerosil Co., Ltd.) 100 parts, 30% aqueous solution of N-vinylacrylamidine hydrochloride / acrylamide copolymer (molar ratio 2: 1, molecular weight about 20,000) 30 And 870 parts of ion-exchanged water were added and dispersed with a stirrer, and then treated with a wet ultrafine atomizer Nanomizer. Next, 25 parts of 20% aqueous solution of polyglycerin (trade name: polyglycerin # 500, manufactured by Sakamoto Pharmaceutical Co., Ltd., average molecular weight 500, hydroxyl value 950-990), polyvinyl alcohol (trade name: PVA-145, ( Co., Ltd., Kuraray Co., Ltd., 99% saponification degree, average polymerization degree 4,500) 5% aqueous solution and a small amount of antifoaming agent, dispersing agent and water were added, and the coating solution for ink receiving layer having a solid content concentration of 8%. A was obtained.

(Preparation of coating liquid B for ink receiving layer)
Wet process synthetic amorphous silica 20% dispersion (trade name: Silojet 703A, manufactured by Grace Devison) 500 parts, polyvinyl alcohol (trade name: PVA-145, manufactured by Kuraray Co., Ltd.) 400% 5% aqueous solution and A small amount of an antifoaming agent, a dispersing agent and water were added to obtain a coating liquid B for ink receiving layer having a solid content concentration of 15%.

(Creation of inkjet recording sheet)
On a paper support (thickness 240 μm, polyethylene resin containing 15% by mass of anatase-type titanium dioxide) on both sides of a 180 g / m ² base paper, the ink receiving layer coating liquid B is 10 g / in solids. After applying and drying with a wire bar so as to be m ² , an ink receiving layer B is provided, and after applying a 3% borax aqueous solution at 20 g / m ² , the ink receiving layer coating liquid A is 15 g / m ^{2 in} solid content. Then, an ink receiving layer was provided by applying and drying with a wire bar, and an ink jet recording sheet was prepared.

Example 2
In Example 1, instead of polyglycerin (trade name: polyglycerin # 500, manufactured by Sakamoto Pharmaceutical Co., Ltd., average molecular weight 500, hydroxyl value 950 to 990), polyglycerin (trade name: polyglycerin # 750, Sakamoto) An inkjet recording sheet was prepared in the same manner as in Example 1 except that Yakuhin Kogyo Co., Ltd., average molecular weight 750, hydroxyl value 870-910) was used.

Example 3
In Example 1, 20 mol% methoxycarbonyl-modified polyallylamine hydrochloride (molecular weight of about 15,000) was used instead of N-vinylacrylamidine hydrochloride / acrylamide copolymer (molar ratio 2: 1, molecular weight of about 200,000). ) Was used in the same manner as in Example 1 to prepare an ink jet recording sheet.

Example 4
In Example 3, instead of polyglycerin (trade name: polyglycerin # 500, manufactured by Sakamoto Pharmaceutical Co., Ltd., average molecular weight 500, hydroxyl value 950 to 990), polyglycerin (trade name: polyglycerin # 750, Sakamoto) An inkjet recording sheet was prepared in the same manner as in Example 1 except that Yakuhin Kogyo Co., Ltd., average molecular weight 750, hydroxyl value 870-910) was used.

Example 5
In Example 1, diallyldimethylammonium hydrochloride / acrylamide copolymer (trade name: PAS-J) was used instead of N-vinylacrylamidine hydrochloride / acrylamide copolymer (molar ratio 2: 1, molecular weight about 20,000). -81, molar ratio 8: 1, molecular weight of about 200,000, Nittobo Co., Ltd.) was used in the same manner as in Example 1 to prepare an ink jet recording sheet.
Example 6
In Example 1, instead of N-vinylacrylamidine hydrochloride / acrylamide copolymer (molar ratio 2: 1, molecular weight about 20,000), diallylamine hydrochloride / acrylamide copolymer (molar ratio 1: 2, molecular weight about An ink jet recording sheet was prepared in the same manner as in Example 1 except that 60,000) was used.

Example 7
(Preparation of silica fine particle dispersion)
Distilled water was added to a sodium silicate solution having a SiO ₂ concentration of 30% by mass and SiO ₂ / Na ₂ O (molar ratio) of 3.1 (manufactured by Tokuyama Corp., No. 3 sodium silicate) to obtain a SiO ₂ concentration of 4.0. After preparing a mass% dilute sodium silicate aqueous solution, an active silicic acid aqueous solution was prepared through a column filled with hydrogen-type cation exchange resin (manufactured by Mitsubishi Chemical Corporation, Diaion SK-1BH). A 5 liter glass reaction vessel equipped with a reflux, stirrer, and thermometer was charged with 500 g of distilled water, heated to 100 ° C., and kept at 100 ° C., the active silicic acid aqueous solution prepared earlier was 1.5 g / min. 450 g was added at a rate of 1 to prepare a seed solution. The average secondary particle diameter of the seed particle aggregate in the seed solution was 184 nm.
Subsequently, after stabilizing by adding 0.9 g of 28% ammonia aqueous solution, 550 g of active silicic acid aqueous solution was further added at 100 ° C. at a rate of 1.5 g / min. After completion of the addition, the mixture was heated to reflux at 100 ° C. for 9 hours and then concentrated to obtain a 10% by mass silica fine particle dispersion. The silica fine particles had an average primary particle diameter of 11 nm, an average secondary particle diameter of 130 nm, a specific surface area of 257 m ² / g, and a pore volume of 1.01 ml / g.

(Preparation of coating liquid C for ink receiving layer)
To 1000 parts of the 10% by weight silica fine particle dispersion obtained above, 30 parts of a 30% aqueous solution of N-vinylacrylamidine hydrochloride / acrylamide copolymer (molar ratio 2: 1, molecular weight about 20,000) was added, After being dispersed by a stirrer, it was processed using a wet ultrafine atomizer Nanomizer. Next, 25 parts of a 20% aqueous solution of polyglycerin (trade name: polyglycerin # 500, manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., average molecular weight 500, hydroxyl value 950-990), then polyvinyl alcohol (trade name: PVA-145). 360 parts of 5% aqueous solution of Kuraray Co., Ltd., saponification degree 99%, average polymerization degree 4,500) and a small amount of antifoaming agent, dispersing agent and water were added, for an ink receiving layer having a solid content concentration of 8% A coating liquid C was obtained.

(Creation of inkjet recording sheet)
On a paper support (thickness 240 μm, polyethylene resin containing 15% by mass of anatase-type titanium dioxide) on both sides of a 180 g / m ² base paper, the ink-receiving layer coating solution B in a solid content of 20 g / After applying and drying with a wire bar so as to be m ² , an ink receiving layer B is provided, and after applying 1.0% borax water coating solution 20 g / m 2, the ink receiving layer coating solution C is solid content. The ink receiving layer C was provided by applying and drying with a wire bar so as to be 7 g / m ² to prepare an ink jet recording sheet.

Comparative Example 1
Inkjet recording was carried out in the same manner as in Example 5 except that polyglycerin (trade name: polyglycerin # 500, manufactured by Sakamoto Pharmaceutical Co., Ltd., average molecular weight 500, hydroxyl value 950 to 990) was not used in Example 5. A sheet was created.
Comparative Example 2
In Example 5, instead of polyglycerin (trade name: polyglycerin # 500, manufactured by Sakamoto Pharmaceutical Co., Ltd., average molecular weight 500, hydroxyl value 950-990), glycerin (trade name: purified glycerin, Sakamoto Pharmaceutical Co., Ltd. ( An ink jet recording sheet was prepared in the same manner as in Example 5 except that 25 parts of a 20% aqueous solution having an average molecular weight of 92 and a hydroxyl value of 1830) were used.

Comparative Example 3
In Example 5, instead of polyglycerin (trade name: polyglycerin # 500, manufactured by Sakamoto Pharmaceutical Co., Ltd., average molecular weight 500, hydroxyl value 950-990), polyglycerin (trade name: polyglycerin # 310, Sakamoto) An ink jet recording sheet was prepared in the same manner as in Example 5 except that 25 parts of a 20% aqueous solution having an average molecular weight of 310 and a hydroxyl value of 1050 to 1090 manufactured by Yakuhin Kogyo Co., Ltd. was used.

(Evaluation methods)
For the ink jet recording sheets obtained in Examples 1 to 7 and Comparative Examples 1 to 3, a Canon ink jet printer PIXUS 9900i (dye ink system) was used, and an ISO-400 image (“high-definition color digital standard image data ISO / JIS— SCID ", p13, image name: portrait, issued by the Japanese Standards Association). The obtained inkjet recording sheet and its image were evaluated as follows, and the results are shown in Table 1.

[Glossiness]
The glossiness of the coated surface of the inkjet recording sheet in the unprinted part was evaluated by visual observation.
(Evaluation criteria)
◎: Very high gloss and good ○: High gloss and good ×: Inferior gloss

〔crack〕
The cracked state of the inkjet recording sheet coated surface of the unprinted part was evaluated by visual observation.
(Evaluation criteria)
◎: No cracks are observed. ○: Some cracks are observed but there is no problem. ×: Cracks are observed and there are practical problems.

[Ink absorbency]
The obtained ISO-400 image was visually observed to evaluate ink absorbency.
(Evaluation criteria)
◎: Image collapse due to ink overflow is not observed at all ○: Image collapse due to ink overflow is slightly observed, but there is no practical problem ×: Image collapse due to ink overflow is observed, and there is a practical problem

〔image quality〕
The image quality in the low gradation part of the obtained ISO-400 image was evaluated by visual observation.
(Evaluation criteria)
◎: Image quality is very good ○: Image quality is good and practically no problem ×: Image quality is inferior and practically problematic

[Coating liquid stability]
The state of the ink receiving layer coating solution was evaluated by workability.
(Evaluation criteria)
A: Cohesion is not observed in the coating liquid and there is no problem at the time of coating. O: The coating liquid is slightly difficult to aggregate, but there is no problem at the time of the coating operation. X: The coating liquid is difficult to aggregate. There is a hindrance during construction work

As is apparent from Table 1, the ink jet recording sheets of Examples 1 to 7 (invention) are excellent in the stability of the coating liquid, excellent in cracking and glossiness of the ink receiving layer, and further have ink absorbability and low floor. Excellent image quality in the toning part.
By using a polyglycerin having an average molecular weight of 400 to 1000 and a hydroxyl value of 800 to 1100 together with a cationic polymer, the ink is maintained while maintaining excellent water resistance obtained by using the cationic polymer. It is possible to improve the performance of the receiving layer coating solution and improve the gloss, cracking, ink absorbability, and image quality of the resulting inkjet recording sheet.

The present invention can be used for an ink jet recording sheet having an ink receiving layer containing inorganic fine particles, a cationic polymer and a binder on a support. In particular, it is possible to provide an ink jet recording sheet suitable for a dye-based or pigment-based ink jet printer that aims at photographic image quality and that ejects ink quickly.

Claims (15)

  In an ink jet recording sheet having an ink receiving layer containing inorganic fine particles, a cationic polymer, and a binder on a support, the ink receiving layer has an average molecular weight of 400 to 1000 and a hydroxyl value of 800 to 1100. An ink jet recording sheet comprising polyglycerin.   The ink jet recording sheet according to claim 1, wherein the inorganic fine particles have an average primary particle diameter of 30 nm or less.   The inkjet recording sheet according to claim 1, wherein the inorganic fine particles are vapor-phase process silica.   The inkjet recording sheet according to claim 1, wherein the inorganic fine particles are wet-process fine silica produced by condensing activated silicic acid. The inkjet recording sheet according to claim 4, wherein the wet method fine silica has a specific surface area of 100 to 400 m ² / g by BET method and a pore volume of 0.5 to 2.0 ml / g. The cationic polymer is represented by the following general formula (1) and / or (2):

[Wherein, X represents an acid residue. ]
And at least one structural unit (a1) represented by the following general formula (3):

[Wherein, R ¹ represents an alkyl group having 1 to 18 carbon atoms, an alkoxyl group having 1 to 18 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a benzyl group. ]
The inkjet recording sheet according to claim 1, which is a polymer (A) containing at least one structural unit (a2) represented by:   The ink jet recording sheet according to claim 1, wherein the ink receiving layer further contains a crosslinking agent.   The inkjet recording sheet according to claim 7, wherein the crosslinking agent is a boron compound.   The ink jet recording sheet according to claim 8, wherein a mass ratio of the boron compound and the cationic polymer in the ink receiving layer is 1: 1 to 1:10.   The inkjet recording sheet according to claim 1, wherein the support is a water-resistant support.   The inkjet recording sheet according to claim 10, wherein the water-resistant support is a support in which both surfaces of paper are coated with a polyolefin resin.   The ink jet recording sheet according to claim 1, wherein the ink receiving layer is cast-treated.   The inkjet recording sheet according to any one of claims 1 to 12, further comprising a cast-treated gloss layer on the ink receiving layer.   After the ink receiving layer forms at least one ink receiving layer containing inorganic fine particles and a binder, an aqueous solution containing a cationic polymer is applied on the ink receiving layer to form a water-coating layer, The inkjet recording sheet according to any one of claims 1 to 13, comprising a plurality of ink receiving layers formed by forming at least one other ink receiving layer on the water-coating layer. The inkjet recording sheet according to claim 14, wherein the aqueous solution containing the cationic polymer further contains a crosslinking agent.