JP7304795B2 - Composition for ink-receiving layer, inkjet recording sheet, and method for producing inkjet recording sheet - Google Patents

Description

The present invention relates to an ink-receiving layer composition, an inkjet recording sheet, and a method for producing an inkjet recording sheet.

An inkjet recording sheet to be subjected to inkjet printing usually comprises a base material and an ink-receiving layer provided on the base material. The ink-receiving layer is a layer that absorbs ink to form prints and images. The ink-receiving layer can be formed by coating a substrate with a liquid composition containing components necessary for fixing ink and a solvent for dispersing or dissolving them, followed by drying. The method of applying the composition onto the substrate can be selected from known methods depending on the purpose. Then, if necessary, the components contained in the composition are adjusted so that the composition has properties suitable for application to this coating method.

For example, when the gravure offset printing method is applied as the coating method of the composition, the composition needs to have a high viscosity to some extent. If the viscosity of the composition is too low, the composition cannot be properly placed on a roll to transfer it. Furthermore, if the viscosity of the composition is too low, the composition tends to scatter during printing. , cannot be raised to this level. In order to avoid such problems, it is desirable, for example, to set the viscosity of the composition to 200 mPa·s or more.

In order to increase the viscosity of the composition, it is effective, for example, to incorporate a thickening agent into the composition. As such a composition, an image-forming processing liquid containing a thickener and applicable to various coating methods is disclosed (see Patent Document 1).

JP-A-2003-246135

However, simply adding a thickening agent to the composition sometimes does not allow the formed ink-receiving layer to exhibit its effect sufficiently. For example, thickeners can reduce the drying properties of ink absorbed in the ink-receiving layer. In that case, the speed of ink jet printing, which is usually desired to be 500 feet/min (152.4 m/min) or more, could not be increased to this level. If the printing speed during inkjet printing cannot be increased, the productivity of printed matter will decrease.

The present invention is a liquid composition for forming an ink-receiving layer in an inkjet recording sheet, which exhibits good printability during gravure offset printing without the need to lower the printing speed more than necessary, and furthermore. An object of the present invention is to provide an ink-receiving layer composition capable of forming an ink-receiving layer having good ink drying properties during inkjet printing, and an inkjet recording sheet obtained using the composition. .

A first aspect of the present invention is an ink-receiving layer composition for forming an ink-receiving layer of an inkjet recording sheet, wherein the ink-receiving layer composition comprises a cationic resin, a polysaccharide and It contains water, the cationic resin is one or more selected from the group consisting of polyamines and polycondensates of epichlorohydrin, and the polysaccharides are glucose, galactose, mannose and glucuronic acid. One or two or more condensates selected from the group consisting of: In the ink-receiving layer composition, the proportion of the content of the cationic resin with respect to the total mass of the ink-receiving layer composition is , 3 to 30% by mass, and in the ink-receiving layer composition, the content of the polysaccharide is 0.3 to 1.3% by mass with respect to the total mass of the ink-receiving layer composition. A composition for an ink-receiving layer.
In the first aspect of the present invention, the polysaccharide is preferably one or both of guar gum and xanthan gum.

A second aspect of the present invention is an inkjet recording sheet comprising a substrate and an ink-receiving layer formed on at least one surface of the substrate, wherein the ink-receiving layer comprises a cationic containing a resin and a polysaccharide, wherein the cationic resin is one or more selected from the group consisting of a polyamine and a polycondensate of epichlorohydrin, and the polysaccharide is glucose, galactose, mannose and glucuronic acid, and in the ink-receiving layer, the content ratio of the cationic resin with respect to the total weight of the ink-receiving layer is 70 to 99% by mass, and in the ink-receiving layer, the ratio of the content of the polysaccharide to the total mass of the ink-receiving layer is 1 to 30% by mass.
In the second aspect of the present invention, the polysaccharide is preferably either or both of guar gum and xanthan gum.
A third aspect of the present invention is a method for producing an ink-jet recording sheet according to the second aspect, wherein the composition for an ink-receiving layer according to the first aspect is applied to a thickness of 304.8 m/m by gravure offset printing. A method for producing an inkjet recording sheet, comprising a step of coating at least one surface of a substrate at a speed of min or more.

According to the present invention, a liquid composition for forming an ink-receiving layer in an inkjet recording sheet exhibits good printability during gravure offset printing without the need to lower the printing speed more than necessary. Also provided are an ink-receiving layer composition capable of forming an ink-receiving layer having good ink drying properties during inkjet printing, and an inkjet recording sheet obtained using the composition.

1 is a cross-sectional view schematically showing an example of an inkjet recording sheet according to an embodiment of the present invention; FIG. FIG. 4 is a cross-sectional view schematically showing another example of the inkjet recording sheet according to one embodiment of the present invention.

<<Composition for ink-receiving layer>>
An ink-receiving layer composition according to one embodiment of the present invention is an ink-receiving layer composition for forming an ink-receiving layer of an inkjet recording sheet, wherein the ink-receiving layer composition comprises: It contains a cationic resin, a polysaccharide and water, wherein the cationic resin is one or more selected from the group consisting of polyamines and polycondensates of epichlorohydrin, and the polysaccharide is glucose. , galactose, mannose and glucuronic acid, and in the ink-receiving layer composition, the cationic The content ratio of the resin is 3 to 30% by mass, and the content ratio of the polysaccharide in the composition for the ink-receiving layer is 0.3 with respect to the total mass of the composition for the ink-receiving layer. ~1.3% by mass.

The ink-receiving layer composition of the present embodiment contains the cationic resin and the polysaccharide, which are components in specific ranges, in specific ranges, so that during gravure offset printing, the printing speed is increased more than necessary. It is possible to form an ink-receiving layer that does not need to be lowered, exhibits good printability, and has good ink drying properties during inkjet printing. In this specification, the term "gravure offset printing" means that the ink-receiving layer composition "exhibits good printability without reducing the printing speed more than necessary during gravure offset printing." It is said that it has printability.

The ink-receiving layer composition of the present embodiment is an ink-receiving layer capable of suppressing, for example, ink bleeding and ink strike-through (a phenomenon in which ink permeates from the printed surface of a sheet to the opposite back surface). can also be used to form
Each component of the ink-receiving layer composition will be described below.

<Cationic resin>
The cationic resin is one or more selected from the group consisting of polyamines and polycondensates of epichlorohydrin (also known as 3-chloro-1,2-epoxypropane).
The cationic resin is a resin that exhibits cationic properties in the presence of water.
The cationic resin is an essential component for fixing the ink in the ink-receiving layer and for the ink-receiving layer to exhibit its basic functions. In addition, the cationic resin achieves good suitability for gravure offset printing in the ink-receiving layer composition.
In this specification, unless otherwise specified, the term "cationic resin" means the aforementioned "polyamine" or "polycondensate of epichlorohydrin".

[Polyamine]
Examples of the polyamine in the cationic resin include an amino group (—NH ₂ ), a substituted amino group in which one or two hydrogen atoms in the amino group are substituted with a group other than a hydrogen atom, an amino group or and a group in which the substituted amino group forms a salt.

When the polyamine has two or more substituted amino groups or groups forming the salt in one molecule, these substituted amino groups or groups forming the salt may be the same or different. good too.
In the present specification, not only the substituted amino group and the group forming the salt, but also the functional group for which there are a plurality of options, "the two or more functional groups may be the same or different from each other. "Good" means that all the functional groups may be the same, all the functional groups may be different, or only some of the functional groups may be the same.

The polyamine may be linear, branched (herein, "linear" and "branched" are collectively referred to as "chain") and cyclic. As used herein, the term "cyclic polyamine" means a polyamine having a cyclic structure, and may have only a cyclic structure, or may have both a cyclic structure and a non-cyclic structure (i.e., a chain structure). may be

The positions of the amino group, the substituted amino group and the group forming the salt in the polyamine are not particularly limited.
For example, when the polyamine is chain-shaped, the amino group, the substituted amino group, and the group forming the salt may be present at the terminal portion of the main chain, or may be present at the non-terminal portion. may In the present specification, the term “main chain” means the chain structure having the largest number of atoms among the continuous chain structures present in the molecule.

Polyamines include, for example, monomers, oligomers or polymers of primary amines, secondary amines, tertiary amines or quaternary ammonium salts.
Polyamines, more specifically, for example, polyamine-epichlorohydrin polycondensate; secondary amino group, acrylic polymer having a tertiary amino group or quaternary ammonium group; polyvinylamine; polyvinylamidine; five-membered ring amidines; dicyandiamide-formalin copolymer and other dicyanic cationic resins; dicyandiamide-polyethyleneamine copolymers and other polyamine cationic resins; polyethylenepolyamine, polypropylenepolyamine and other polyalkylenepolyamines and derivatives thereof; diallyldimethylammonium _-SO2 copolymer; diallylamine salt _-SO2 copolymer; diallyldimethylammonium chloride polymer; allylamine salt polymer; vinylbenzyltriallyl ammonium salt homopolymer or copolymer; acrylate quaternary salt copolymers; acrylamide-diallylamine salt copolymers;
A polyamine-epichlorohydrin polycondensate is a polycondensate of epichlorohydrin, but in this specification, it is treated as a polyamine rather than a polycondensate of epichlorohydrin, which will be described later.

In addition, in this specification, "(meth)acrylate" is a concept that includes both "acrylate" and "methacrylate". The same applies to terms similar to "(meth)acrylate". For example, "(meth)acrylic acid" is a concept that includes both "acrylic acid" and "methacrylic acid", and "(meth) “Acryloyl group” is a concept that includes both “acryloyl group” and “methacryloyl group”.

Moreover, in this specification, a polycondensate is also contained in a polymer.
In this specification, unless otherwise specified, the terms "derivative" and "similar" mean that one or more hydrogen atoms of the original compound are substituted with a group other than a hydrogen atom. . Here, the term "group" includes not only an atomic group formed by bonding a plurality of atoms, but also a single atom.

[Polycondensate of epichlorohydrin]
The epichlorohydrin polycondensate (excluding polyamine-epichlorohydrin polycondensate) in the cationic resin may have structural units derived from epichlorohydrin.
The polycondensate of epichlorohydrin includes, for example, a polycondensate of epichlorohydrin and a monomer other than epichlorohydrin (in other words, a structural unit derived from epichlorohydrin and a structural unit derived from a monomer other than epichlorohydrin. resin).

Monomers other than epichlorohydrin are not particularly limited as long as they can be polycondensed with epichlorohydrin (except for polyamines). As the monomer, for example, an amino group (—NH ₂ ) or a substituted amino group in which one or two hydrogen atoms in the amino group are substituted with a group other than a hydrogen atom, one in one molecule amine compounds having

The molecular weight of the amine compound is not particularly limited. For example, the amine compound may be a low-molecular-weight compound with a molecular weight of less than 10,000, or a high-molecular-weight compound with a molecular weight of 10,000 or more. Moreover, the amine compound may be either a polymer or a non-polymer. Here, "polymer" includes "polycondensate".

The positions of the amino group and the substituted amino group in the amine compound are not particularly limited.

A monomer other than epichlorohydrin (in other words, a structural unit derived from a monomer other than epichlorohydrin in the polycondensate) that constitutes the polycondensate of epichlorohydrin may be only one kind, or two kinds. or more, and when there are two or more kinds, the combination and ratio thereof can be arbitrarily selected according to the purpose.

The monomer other than epichlorohydrin is preferably the amine compound described above, more preferably alkylamine (amine having an alkyl group), and particularly preferably dimethylamine.
That is, the epichlorohydrin polycondensate is preferably an amine compound-epichlorohydrin polycondensate, more preferably an alkylamine-epichlorohydrin polycondensate, and particularly preferably a dimethylamine-epichlorohydrin polycondensate. .

The cationic resin contained in the ink-receiving layer composition may be of only one type, or may be of two or more types. can be selected arbitrarily.
For example, the ink-receiving layer composition may contain only one or two or more polyamines as the cationic resin, or may contain only one or two or more polycondensates of epichlorohydrin. Alternatively, one or two or more polyamines and one or two or more polycondensates of epichlorohydrin may be contained together.

In the composition for the ink-receiving layer, the content of the cationic resin is 3 to 30% by mass, preferably 3.5 to 27% by mass, with respect to the total mass of the composition for the ink-receiving layer. 4 to 24% by mass is more preferable, and 4.5 to 22% by mass is particularly preferable. Moreover, the said ratio may be 7.5 mass % or more, for example. When the ratio is within such a range, the composition for the ink-receiving layer does not deteriorate in printing speed and printability during gravure offset printing, and can form an ink-receiving layer with better properties. and In particular, when the ratio is equal to or higher than the lower limit, the effect of suppressing ink bleeding in the ink-receiving layer is enhanced. In addition, when the ratio is equal to or less than the upper limit, the composition for the ink-receiving layer dries quickly and the ink-absorbing property of the ink-receiving layer increases.

<Polysaccharides>
The polysaccharides are one or more condensates selected from the group consisting of glucose, galactose, mannose and glucuronic acid. The polysaccharide is a component (that is, a thickener) for increasing the viscosity of the composition for the ink-receiving layer. It is possible to exert its effect on
In the present specification, unless otherwise specified, the term "polysaccharide" refers to the above-mentioned "one or more condensates selected from the group consisting of glucose, galactose, mannose and glucuronic acid". means.

The polysaccharide is selected from the group consisting of a structural unit derived from glucose, a structural unit derived from galactose, a structural unit derived from mannose, and a structural unit derived from glucuronic acid 1 It suffices if it has a species or two or more species.
The polysaccharides include, for example, condensates of only one or two or more selected from the group consisting of glucose, galactose, mannose and glucuronic acid (in other words, as structural units, structural units derived from glucose, Condensates containing only one or more selected from the group consisting of structural units derived from galactose, structural units derived from mannose, and structural units derived from glucuronic acid); glucose; Condensation of one or more selected from the group consisting of galactose, mannose and glucuronic acid with other monosaccharides (in this specification, sometimes abbreviated as "other monosaccharides") (In other words, as structural units, from the group consisting of a structural unit derived from glucose, a structural unit derived from galactose, a structural unit derived from mannose, and a structural unit derived from glucuronic acid Condensates having one or more selected species and structural units derived from the other monosaccharides).

Preferred polysaccharides include, for example, condensates of galactose and mannose only; condensates of glucose, mannose and glucuronic acid; condensates of galactose, mannose and other monosaccharides; glucose, mannose and glucuronic acid. and condensates of only the above-mentioned other monosaccharides, and the like.

When the polysaccharide is a condensation product of one or more selected from the group consisting of glucose, galactose, mannose and glucuronic acid and the other monosaccharide, one molecule of the polysaccharide, Ratio of the total number of structural units derived from glucose, structural units derived from galactose, structural units derived from mannose, and structural units derived from glucuronic acid to the total number of all structural units ([Total number of structural units derived from glucose, structural units derived from galactose, structural units derived from mannose, and structural units derived from glucuronic acid in one molecule of the polysaccharide ]/[Total number of all structural units in one molecule of the polysaccharide]×100) is not particularly limited, but is preferably 80% or more, more preferably 90% or more, and 95% or more. is particularly preferred.

The upper limit of the ratio is not particularly limited. For example, the ratio is preferably 99% or less from the viewpoint that the effect of using the other monosaccharide can be obtained more remarkably.

The other monosaccharide is not particularly limited as long as it does not fall under any of glucose, galactose, mannose, and glucuronic acid, and can be arbitrarily selected according to the purpose.

The other monosaccharides constituting the polysaccharide (in other words, structural units derived from the other monosaccharides in the polysaccharide) may be of one type or two or more types. may be used, and when there are two or more types, the combination and ratio thereof can be arbitrarily selected according to the purpose.

Although the weight average molecular weight of the polysaccharide is not particularly limited, it is preferably from 100,000 to 8,000,000, more preferably from 150,000 to 6,000,000.
In this specification, unless otherwise specified, the weight average molecular weight is a polystyrene-equivalent value measured by a gel permeation chromatography (GPC) method.

The polysaccharides contained in the ink-receiving layer composition may be of one type or two or more types. can be selected arbitrarily.

Examples of preferred polysaccharides contained in the ink-receiving layer composition include guar gum and xanthan gum.
That is, the polysaccharide contained in the ink-receiving layer composition is preferably one or both of guar gum and xanthan gum.

In the ink-receiving layer composition, the content of the polysaccharide is 0.3 to 1.3% by mass, and 0.3 to 1.1% by mass, relative to the total mass of the ink-receiving layer composition. , more preferably 0.3 to 0.95% by mass, and particularly preferably 0.3 to 0.8% by mass. When the ratio is within such a range, the composition for the ink-receiving layer does not deteriorate in printing speed and printability during gravure offset printing, and can form an ink-receiving layer with better properties. and In particular, when the ratio is equal to or higher than the lower limit, the viscosity of the ink-receiving layer composition increases. Further, when the ratio is equal to or less than the upper limit, the drying property of the ink in the ink-receiving layer is enhanced.

<Water>
In the composition for the ink-receiving layer, water is a solvent or component for dispersing components other than water, and is removed from the ink-receiving layer.
In this specification, unless otherwise specified, the solvent and the dispersion medium are collectively referred to as "solvent".

In the composition for the ink-receiving layer, the content of water may be, for example, 68.7 to 96.7% by mass with respect to the total mass of the composition for the ink-receiving layer.

<Other ingredients>
The composition for the ink-receiving layer includes other components (which may be abbreviated as “other components” in this specification) that do not correspond to any of the cationic resin, the polysaccharide, and water. There is) may be contained.
The other components are not particularly limited and can be arbitrarily selected according to the purpose.
Examples of the other components include cationic resins other than the cationic resin (in this specification, may be referred to as "other cationic resins"), polysaccharides other than the polysaccharides (in this specification, may be referred to as "other polysaccharides"), solvents other than water, binders, ink fixing agents, polyvalent metal salts, pH adjusters, defoaming agents, foam inhibitors, release agents, foaming agents , Antioxidants, preservatives, water repellents, paper strength agents, dyes, pigments, dye fixatives, pigment dispersants, fluorescent brighteners, UV absorbers, etc. Ingredients that may be used include:

The other components contained in the ink-receiving layer composition may be of one kind or may be of two or more kinds. It can be selected arbitrarily.

In the composition for the ink-receiving layer, the content of the other components is usually preferably 20 parts by mass or less with respect to 100 parts by mass as the total content of the cationic resin and the polysaccharide, for example, 15 parts by mass. It may be any one of 0 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less. It doesn't have to be. When the content of the other component is equal to or less than the upper limit, the effect of using the cationic resin and the polysaccharide can be obtained more remarkably.
Furthermore, the content of the other component may be further adjusted within the above range depending on the type of the other component.

[Other cationic resins]
The other cationic resin is a cationic resin that does not correspond to any of the polyamines and epichlorohydrin polycondensates described above.
Other cationic resins are not particularly limited as long as they satisfy this condition.
Other cationic resins can be used as ink fixatives.

Examples of the other cationic resin include aluminum salts such as polyaluminum chloride and polyaluminum acetate.

The other cationic resin contained in the ink-receiving layer composition may be of only one type, or may be of two or more types. can be selected arbitrarily according to

In the composition for the ink-receiving layer, the content of the other cationic resin is preferably 10 parts by mass or less with respect to 100 parts by mass of the cationic resin content, for example, 5 parts by mass or less, 3 It may be either 1 part by mass or less, or 0 part by mass, that is, the ink-receiving layer composition may not contain other cationic resins. When the content of the other cationic resin is equal to or less than the upper limit, the effect of using the cationic resin can be obtained more remarkably.

[Other polysaccharides]
The other polysaccharides are polysaccharides that do not correspond to one or more condensates selected from the group consisting of glucose, galactose, mannose and glucuronic acid described above.
Other polysaccharides are not particularly limited as long as they satisfy this condition.
Other polysaccharides can be used, for example, as thickeners, binders, and the like.

Other polysaccharides include, for example, oxidized starch, phosphated starch, locons, and the like.

The other polysaccharides contained in the ink-receiving layer composition may be of one type or two or more types. It can be selected arbitrarily.

In the ink-receiving layer composition, the content of the other polysaccharide is preferably 10 parts by mass or less, for example, 5 parts by mass or less, or 3 parts by mass, with respect to 100 parts by mass of the polysaccharide. or 1 part by mass or less, or 0 part by mass, that is, the ink-receiving layer composition may not contain other polysaccharides. When the content of the other polysaccharide is equal to or less than the upper limit, the effect of using the polysaccharide can be obtained more remarkably.

[Solvents other than water]
The solvent other than water is not particularly limited as long as it is liquid at normal temperature and is a component other than water among the components normally used as a solvent or dispersion medium.
In this specification, the term "ordinary temperature" means a temperature at which no particular cooling or heating is applied, that is, a normal temperature.

In the present embodiment, when the cationic resin, the polysaccharide, or the other components other than the solvent are blended as a dispersion or a solution in order to produce the composition for the ink-receiving layer, the dispersion or If no solvent (excluding water) is blended in addition to the solvent (excluding water) used to prepare the solution, the solvent other than water is used to prepare the dispersion or solution. means the solvent (but excluding water) used for
On the other hand, when a separate solvent (excluding water) is blended in addition to the solvent (excluding water) used to prepare the dispersion or solution, the solvent other than water is the dispersion means both the solvent (excluding water) used to prepare the product or solution, and the separately formulated solvent (excluding water).
When the cationic resin, the polysaccharide, and the other components other than the solvent are all blended as solids, the solvent other than the water is the solvent blended separately from these (however, water is not included). excluding).

Examples of solvents other than water include alcohols.

The ink-receiving layer composition may contain only one solvent other than water, or two or more solvents. It can be selected arbitrarily.

[pH adjuster]
Examples of the pH adjuster include bases.
Since the composition for the ink receiving layer contains a cationic resin, it usually tends to be acidic. Therefore, during gravure offset printing, if the printing apparatus has iron components as its components, the iron components will corrode (rust) unless cleaned after printing. And, the printing performance of a printing device with corroded components can be significantly degraded.

Examples of the iron components include, but are not limited to, shafts and gears of gravure rollers.
The reason why the printing apparatus has iron components as its components is, for example, to maintain the mechanical strength of the printing apparatus.

In contrast, by using a base-containing, acidity-reduced or non-acidic ink-receiving layer composition, during gravure offset printing, a printing apparatus having iron components can be used for printing. Corrosion of these ferrous components can be suppressed without subsequent cleaning, thereby avoiding deterioration of the printing performance of the printing apparatus.

The base is preferably a strong base.
The base preferably has a solubility of 70 g/100 mL or more, more preferably 100 g/100 mL or more, in water. The base preferably has these solubility in water at 18 to 23°C.

Preferred examples of the base include sodium hydroxide, potassium hydroxide and the like.

The ink-receiving layer composition may contain only one kind of base, or two or more kinds of bases. can be selected to

Preferred base-containing compositions for the ink-receiving layer include, for example, those containing either one or both of sodium hydroxide and potassium hydroxide.

When a base is used, the content of the base in the composition for the ink-receiving layer is preferably 0.4 to 1.2% by mass with respect to the total mass of the composition for the ink-receiving layer. When the proportion is equal to or higher than the lower limit, the effect of using a base in the ink-receiving layer composition is enhanced. When the ratio is equal to or less than the upper limit, the effect of avoiding the inclusion of solids (insolubles) in the composition for the ink-receiving layer (increasing the solubility) is improved, and the composition for the ink-receiving layer is improved. The coating suitability of is improved.
The ratio may be further adjusted within the numerical range described above depending on, for example, the type of base used.

The extent of the corrosion-inhibiting effect of the composition for the ink-receiving layer can be determined, for example, by immersing iron in the composition for the ink-receiving layer and measuring the absorption spectrum of the composition for the ink-receiving layer before and after the immersion in a specific wavelength range. , L ^* a ^* b ^* , the values of L ^* , a ^* , and b ^* in the color system are calculated, and the color difference (ΔE) of the ink-receiving layer composition before and after immersion, which is obtained from these calculated values, can be evaluated.
This evaluation method utilizes the fact that when the corrosion inhibition effect of the composition for the ink-receiving layer on iron is low, the color of the composition for the ink-receiving layer changes greatly as the corrosion rate of iron increases. Then, the degree of corrosion inhibition effect of the composition for the ink receiving layer is evaluated from the degree of color change.
More specifically, it is as follows.

That is, for example, the ink-receiving layer composition and iron are mixed at a mass ratio of [ink-receiving layer composition (parts by mass)]:[iron (parts by mass)] = 85:15, and the iron is added to the ink. After being immersed in the receiving layer composition, the iron and the ink receiving layer composition were allowed to stand at a temperature of 28° C. for 72 hours. The absorption spectrum is measured in the wavelength region of 380 to 780 nm, the values of L ^{* ,} a ^* and b ^* in the L*a ^* b ^* color system are calculated, and from these calculated values, the ink receiving layer before and after immersion. The color difference (ΔE) of the composition for ink-receiving layer is calculated, and the corrosion inhibiting effect of the composition for ink-receiving layer can be evaluated based on the calculated value.

The color difference (ΔE) of the composition for the ink-receiving layer before and after immersion in iron is obtained by taking the values of L ^* , a ^*, and b ^* of the composition for the ink-receiving layer before immersion in iron as L ₀ ^* and a ₀ , respectively. ^* and b ₀ ^* , and the values of L ^* , a ^* , and b ^* of the ink-receiving layer composition after immersion in iron are L ₁ ^* , a ₁ ^* , and b ₁ ^* , respectively. :
ΔE = [(L ₁ ^* - L ₀ ^* ) ² + (a ₁ ^* - a ₀ ^* ) ² + (b ₁ ^* - b ₀ ^* ) ² ] ^1/2
It can be calculated by

The corrosion inhibitory effect of the composition for the ink-receiving layer can be evaluated by, for example, using a test composition for the ink-receiving layer which is the same as the target composition for the ink-receiving layer except that it does not contain a polysaccharide. may be evaluated. This is due to the fact that it may not be possible to calculate accurate values for L ^* , a ^* , and b ^* for an ink-receiving layer composition having a high viscosity, and on the other hand, the polysaccharides inhibit corrosion of the ink-receiving layer composition. This is because there is no or very slight influence on the effect.

The ΔE of the ink-receiving layer composition of the present embodiment is preferably 40 or less, more preferably 7 or less, and even more preferably 1 or less.
The corrosion-inhibiting effect of the ink-receiving layer composition having ΔE of 1 or less is extremely high, and the corrosion rate of iron is equivalent to that of stainless steel.
The corrosion-inhibiting effect of the composition for the ink-receiving layer in which the ΔE is greater than 1 and 7 or less is inferior to that in the case where ΔE is 1 or less, but the corrosion rate of iron is higher than that of antirust-treated iron. Equivalent to corrosion rate.
The corrosion-inhibiting effect of the ink-receiving layer composition in which the ΔE is greater than 7 and 40 or less is inferior to that in which ΔE is 1 or less. Corrosion begins after approximately 12 hours of contact with the do not.
Iron begins to corrode when in contact with the ink-receiving layer composition having ΔE exceeding 40 in an environment of 28° C. for 1 to 2 hours. ), the printing performance of printing devices with ferrous components may be degraded.

The absorption spectrum of the ink-receiving layer composition can be measured using a spectrophotometer, and the measured values are used to calculate the values of L ^*, a ^*, and b ^* in the L ^* a ^* b ^* color system. can.

The ink-receiving layer composition of the present embodiment has a high viscosity and is suitable for gravure offset printing.
The viscosity of the ink-receiving layer composition measured using a Brookfield viscometer in an environment of 23° C. is preferably 200 Pa·s or more, for example, 300 Pa·s or more, 400 Pa·s or more, It may be any one of 500 Pa·s or more, 600 Pa·s or more, or 700 Pa·s or more, or may be 1200 Pa·s or more. The ink-receiving layer composition has good suitability for gravure offset printing when its viscosity is 200 Pa·s or more.
The viscosity of the ink-receiving layer composition can be measured using a Brookfield viscometer, for example, according to JIS Z 8803:2011.

The viscosity of the composition for the ink-receiving layer is preferably 1600 Pa·s or less from the viewpoint of further improving suitability for gravure offset printing.

The ink-receiving layer composition has good solubility, little or no precipitation of solid matter, and precipitation of solid matter is suppressed. Suitable for application to coating methods.

<<Method for Producing Composition for Ink-Receiving Layer>>
The ink-receiving layer composition can be produced by blending the cationic resin, polysaccharide, water, and, if necessary, other components, and sufficiently stirring these components.

The order in which each component is added is not particularly limited.
When blending each component, these may be mixed after adding all components, may be mixed while sequentially adding some components, or may be mixed while sequentially adding all components. good.
Water and other solvents may be used by being premixed with the cationic resin, polysaccharide, or other components other than the solvent, as described above, or may be premixed with these components. It can be used alone without

The temperature at which each component is blended is not particularly limited, and may be appropriately adjusted according to the type of blended component, etc., but it is usually preferably 15 to 30°C.
The mixing method is not particularly limited, and includes a method of mixing by rotating a stirrer or a stirring blade; a method of mixing using a mixer, three rolls, a kneader, a bead mill, etc.; It may be appropriately selected from known methods.
The mixing time may be appropriately adjusted according to the total amount of the ink-receiving layer composition to be produced, the mixing method, and the like, and is preferably 10 minutes to 24 hours, for example.

<<Inkjet recording sheet, method for manufacturing inkjet recording sheet>>
An inkjet recording sheet according to one embodiment of the present invention is an inkjet recording sheet comprising a substrate and an ink-receiving layer formed on at least one surface of the substrate, wherein the ink-receiving The layer contains a cationic resin and a polysaccharide, the cationic resin is one or more selected from the group consisting of polyamines and polycondensates of epichlorohydrin, and the polysaccharide is One or two or more condensates selected from the group consisting of glucose, galactose, mannose and glucuronic acid, and in the ink-receiving layer, the content of the cationic resin with respect to the total weight of the ink-receiving layer The ratio is 70 to 99% by mass, and the content ratio of the polysaccharide in the ink receiving layer is 1 to 30% by mass with respect to the total mass of the ink receiving layer.

The ink-receiving layer in the inkjet recording sheet of the present embodiment is formed using the ink-receiving layer composition described above. Therefore, the inkjet recording sheet of the present embodiment has good ink drying properties during inkjet printing, and the printing speed during inkjet printing can be set to, for example, 152.4 m/min (500 feet/min) or more. possible and suitable for high-speed printing.
The structure of the ink jet recording sheet and the manufacturing method thereof will be described below.

<Base material>
The constituent material of the base material is not particularly limited, and may be selected according to the purpose from materials capable of forming a coating layer. For example, the substrate may be a water-resistant substrate or a non-water-resistant substrate.
Examples of the water-resistant substrate include substrates having a retention rate of 10% or more in either the vertical grain or the horizontal grain in a wet tensile strength test according to JIS P8135:1998.

Constituent materials for the base material include, specifically, papers such as waterproof paper, coated paper, fine paper, art paper, cast-coated paper, resin-coated paper, and synthetic paper; polyethylene, polypropylene, polyvinyl chloride, and polystyrene. , polyvinyl acetate, acrylic resin, AS resin, ABS resin, polyamide, polyacetal, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyphenylene sulfide, polysulfone, polycarbonate, epoxy resin, Synthetic resins such as melamine resins, phenol resins, urea resins, polyurethanes, and polyimides are included.

The substrate may consist of a single layer, or may consist of a plurality of layers of two or more layers, and in the case of a plurality of layers, these layers may be the same or different from each other. . That is, all layers may be the same, all layers may be different, or only some layers may be different. And when multiple layers differ from each other, the combination of these multiple layers is not specifically limited.
In this specification, not only in the case of the base material, but "multiple layers differ from each other" means that at least one of the constituent material and thickness of each layer differs from each other.

The thickness of the substrate is not particularly limited as long as the shape of the substrate is sheet-like or film-like. is particularly preferred. When the thickness of the substrate is equal to or greater than the lower limit, the structure of the ink receiving layer can be more stably maintained. When the thickness of the substrate is equal to or less than the above upper limit, the handleability as an inkjet recording sheet is improved.
When the substrate is composed of multiple layers, the total thickness of each layer is preferably the thickness of the substrate described above.

As the base material, a commercially available product may be used, or one manufactured by a known method may be used.

<Ink receiving layer>
The ink-receiving layer can be formed by applying the ink-receiving layer composition onto a substrate and drying the composition.
The coating of the composition for the ink-receiving layer on the substrate may be carried out in one step or in multiple steps. When the coating is performed in multiple steps, a method of further coating the ink-receiving layer composition on the dried coating layer, and a method of further coating the ink-receiving layer composition on the undried coating layer. or a method of applying the layer composition.
The amount of the ink-receiving layer composition to be applied may be appropriately adjusted in consideration of the content of the cationic resin and polysaccharide in the ink-receiving layer composition, the thickness of the ink-receiving layer, and the like.

The method for applying the composition for the ink-receiving layer is not particularly limited, and any method may be used as long as it is capable of applying a liquid material, but gravure offset printing is preferred.
Unlike conventional compositions, the ink-receiving layer composition has a high viscosity. Therefore, when the gravure offset printing method is applied, the ink-receiving layer composition can be normally placed on a roll for transferring the ink-receiving layer composition. can be done. Furthermore, the ink-receiving layer composition is less likely to scatter during printing even when gravure offset printing is performed at high speed. As described above, the ink-receiving layer composition has suitability for gravure offset printing, and the effect of the present invention is most exhibited when the ink-receiving layer is formed by applying the gravure offset printing method.

In this embodiment, by using the ink-receiving layer composition having a high viscosity, the printing speed in the gravure offset printing method can be set to, for example, 304.8 m/min (1000 feet/min) or more. and high-speed printing is possible.

The applied ink-receiving layer composition may be dried by a known method such as blow drying, hot blow drying, or the like. Conditions such as drying temperature and drying time may be appropriately set according to the drying method. For example, when hot air drying is performed, the heating temperature is preferably 80 to 120°C, and the heating time is preferably 30 seconds to 3 hours. However, this drying condition is an example.

The ink-receiving layer contains cationic resin and polysaccharide.
The cationic resin contained in the ink-receiving layer is the same as the cationic resin contained in the ink-receiving layer composition, and is one or two selected from the group consisting of polyamines and epichlorohydrin polycondensates. That's it. The polysaccharide contained in the ink-receiving layer is the same as the polysaccharide contained in the ink-receiving layer composition, and is one or more selected from the group consisting of glucose, galactose, mannose and glucuronic acid. It is a condensate.

The cationic resin contained in the ink-receiving layer may be of only one type, or may be of two or more types. You can choose.
For example, the ink-receiving layer may contain only one or two or more polyamines or one or more polycondensates of epichlorohydrin as cationic resins. Alternatively, one or more polyamines and one or more epichlorohydrin polycondensates may be contained together.

The polysaccharide contained in the ink-receiving layer may be of one type or two or more types. You can choose.

Preferred examples of polysaccharides contained in the ink-receiving layer include guar gum and xanthan gum.
That is, the polysaccharide contained in the ink-receiving layer is preferably one or both of guar gum and xanthan gum.

The content ratio of the components that do not vaporize at room temperature in the composition for the ink-receiving layer is usually the same as the content ratio of the components in the ink-receiving layer.

Therefore, in the ink-receiving layer, the content of the cationic resin is 70 to 99% by mass, preferably 80 to 98.6% by mass, with respect to the total mass of the ink-receiving layer. It is more preferably up to 98.3% by mass, and particularly preferably 90 to 98% by mass.

In addition, in the ink-receiving layer, the content ratio of the polysaccharide to the total mass of the ink-receiving layer is 1 to 30% by mass, preferably 1.3 to 20% by mass. It is more preferably 6 to 15% by mass, particularly preferably 2 to 10% by mass. When the ratio is equal to or less than the upper limit, the drying property of the ink in the ink-receiving layer is further enhanced.

The ink-receiving layer contains other components (in this specification, sometimes abbreviated as "other components") that are neither the cationic resin nor the polysaccharide. may
The other components contained in the ink-receiving layer are the same as the other components contained in the ink-receiving layer composition, excluding solvents other than water.

The other components contained in the ink-receiving layer may be of one kind or may be of two or more kinds. can be selected to

In the ink-receiving layer, the content of the other components is usually preferably 20 parts by mass or less, for example, 15 parts by mass or less, with respect to 100 parts by mass of the total content of the cationic resin and polysaccharide. , 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less. When the content of the other component is equal to or less than the upper limit, the effect of using the cationic resin and the polysaccharide can be obtained more remarkably.

Furthermore, the content of the other component may be further adjusted within the above range depending on the type of the other component.
For example, in the ink-receiving layer, the content of the other cationic resin is preferably 10 parts by mass or less with respect to 100 parts by mass of the cationic resin, for example, 5 parts by mass or less, or 3 parts by mass. 1 part by mass or less, and 0 part by mass, that is, the ink-receiving layer may not contain other cationic resins. When the content of the other cationic resin is equal to or less than the upper limit, the effect of using the cationic resin can be obtained more remarkably.
For example, in the ink-receiving layer, the content of the other polysaccharide is preferably 10 parts by mass or less, for example, 5 parts by mass or less, or 3 parts by mass or less, with respect to 100 parts by mass of the polysaccharide. and 1 part by mass or less, or 0 part by mass, that is, the ink-receiving layer may not contain other polysaccharides. When the content of the other polysaccharide is equal to or less than the upper limit, the effect of using the polysaccharide can be obtained more remarkably.

The amount of the ink-receiving layer formed on the substrate is preferably 0.4 g/m ² or more, more preferably 0.6 g/m ² or more, and 0.8 g/m ² or more. is particularly preferred. When the amount of the ink-receiving layer formed is equal to or greater than the lower limit, the effect of providing the ink-receiving layer can be obtained more remarkably.
On the other hand, the upper limit of the amount of the ink-receiving layer formed on the substrate is not particularly limited. For example, the amount of the ink-receiving layer formed on the base material is preferably 10 g/m ² or less so as not to form an excessive amount of the ink-receiving layer.

The amount of the ink-receiving layer formed can be adjusted, for example, by adjusting the coating amount of the composition for the ink-receiving layer on the substrate, or the amount of each component of the composition for the ink-receiving layer. .

In the inkjet recording sheet of the present embodiment, the amount (g/m ² ) of the ink-receiving layer formed on the base material is the value of the thickness (μm) of the formed ink-receiving layer will be exactly the same.

The inkjet recording sheet of the present embodiment may comprise a substrate and an ink-receiving layer formed on at least one surface of the substrate. It may be provided, or may be provided on both sides.
When the inkjet recording sheet has ink-receiving layers on both sides of the substrate, these two ink-receiving layers may be the same or different.

That is, the inkjet recording sheet of the present embodiment can be produced by a production method including a step of coating at least one side (one side or both sides) of a base material with the ink-receiving layer composition described above. A preferred manufacturing method is to apply the ink-receiving layer composition described above onto at least one side (one side or both sides) of a substrate at a speed of 304.8 m/min or more by gravure offset printing. It is a manufacturing method having a step of machining.

Next, the overall structure of the inkjet recording sheet of this embodiment will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing an example of the inkjet recording sheet of this embodiment. FIG. 2 is a cross-sectional view schematically showing another example of the inkjet recording sheet of this embodiment.
2, the same components as those shown in FIG. 1 are given the same reference numerals as in FIG.
In addition, in the drawings used in the following description, in order to make the features of the present invention easier to understand, there are cases where the main parts are enlarged for convenience, and the dimensional ratio of each component is the same as the actual one. not necessarily.

The ink-jet recording sheet 1 shown in FIG. 1 comprises an ink-receiving layer 12 only on one surface 11a of a substrate 11 (which may be referred to as the "first surface" in this specification). ing.
The ink jet recording sheet 2 shown in FIG. Both sides) are provided with an ink-receiving layer 12 . As for the two ink-receiving layers 12, 12 in the inkjet recording sheet 2, the one provided on the first surface 11a of the base material 11 is shown as a first ink-receiving layer 121, if necessary. 11 is shown as a second ink-receiving layer 122 to distinguish from each other.

In FIG. 1, reference numeral 12a denotes the surface of the ink-receiving layer 12 opposite to the side of the substrate 11 (in this specification, it may be referred to as "first surface"), and reference numeral 12b denotes the ink-receiving layer. 12 shows the surface of the substrate 11 side (in this specification, it may be referred to as the "second surface").
In FIG. 2, reference numerals 12a, 121a, and 122a indicate the surfaces (first surfaces) of the ink-receiving layer 12, the first ink-receiving layer 121, and the second ink-receiving layer 122, which are opposite to the substrate 11 side. , reference numerals 12b, 121b and 122b indicate the substrate 11 side surface (second surface) of the ink receiving layer 12, the first ink receiving layer 121 and the second ink receiving layer 122, respectively.

1 and 2, the substrate 11 and the ink-receiving layer 12 (the first ink-receiving layer 121 and the second ink-receiving layer 122) are the same as described above.

However, the inkjet recording sheets shown in FIGS. 1 and 2 are merely examples of the inkjet recording sheet of the present embodiment, and the inkjet recording sheet of the present embodiment is not limited to these.

In the inkjet recording sheet of this embodiment, the ink-receiving layer may be provided on the entire formation target surface of the base material, or may be provided only on a part of the area.
When the ink-jet recording sheet of the present embodiment is viewed from above the side on which the ink-receiving layer is provided, the surface area of the ink-receiving layer may be equal to or less than the surface area of the substrate. As long as this condition is satisfied, it is not particularly limited. The shapes of the ink-receiving layer and the base material when viewed in plan can also be arbitrarily set according to the purpose, and are not particularly limited. For example, the shapes of the ink-receiving layer and the substrate when viewed from above may be similar or non-similar to each other.

Depending on the purpose, the inkjet recording sheet of the present embodiment may have a layer other than the ink-receiving layer on the substrate.
Examples of the other layer include a pressure-sensitive adhesive layer, an adhesive layer, a release film, and the like.

Examples of the pressure-sensitive adhesive layer and the adhesive layer include those for attaching and fixing an inkjet recording sheet to a target object. When the inkjet recording sheet is provided with such a pressure-sensitive adhesive layer or adhesive layer, it is preferable that the pressure-sensitive adhesive layer or adhesive layer is not exposed by further providing a release film on these layers.

As the adhesive layer, for example, the overlapping surfaces of the objects to be adhered, which are initially separated from each other, are adhered to each other via the adhesive layer, and then the objects to be adhered are separated by peeling off the objects to be adhered. A pseudo-adhesive layer for adhering objects to be adhered in a so-called repeelable manner, which enables the object to be peeled off again without damaging the overlapping surfaces of the objects, is also included. In this specification, the adhesion of objects to be adhered by a pseudo-adhesive layer is referred to as "pseudo-adhesion", and the state in which the objects to be adhered that are pseudo-adhered are separated again is referred to as "re-peeling". .
A pseudo-adhesive layer may be provided on the ink-receiving layer.

The inkjet recording sheet provided with the pseudo-adhesive layer may be in a state in which the object to be adhered is removably adhered to the pseudo-adhesive layer, or the object to be adhered may not be adhered to the pseudo-adhesive layer. Further, the inkjet recording sheet provided with the pseudo-adhesive layer may be in a state in which one inkjet recording sheet is folded and re-separably adhered by the pseudo-adhesive layer.

The present invention will be described in more detail below with reference to specific examples. However, the present invention is by no means limited to the examples shown below.

<Base material>
In the following examples, comparative examples and reference examples, the substrates shown below were used.

<raw materials>
In the following examples, comparative examples and reference examples, the following cationic resins, polysaccharides and bases were used.

[Example 1]
<<Production of composition for ink-receiving layer>>
At room temperature, polysaccharide (b)-1 (0.55 g) was added to water (90.35 g) and stirred for 1 hour at a stirring speed of about 500 rpm using a stirrer to obtain polysaccharide (b). -1 was completely dissolved to obtain an aqueous solution.
Then, at room temperature, the cationic resin (a)-1 (9.1 g, 5.0 g as alkylamine-epichlorohydrin polycondensate, 4.1 g as water) was added to the aqueous solution obtained, and stirred using a stirrer. By stirring at a stirring speed of about 500 rpm for 10 minutes, a liquid ink-receiving layer composition was obtained.

<<Production of inkjet recording sheets>>
Using a bar coater, the ink-receiving layer composition obtained above was coated on one side of the substrate (z)-1, and the coated substrate (z)-1 was coated with The ink-receiving layer was formed by placing in a hot air oven at 105° C. and drying for 1 minute to obtain an ink-jet recording sheet. In this inkjet recording sheet, the amount of the ink-receiving layer formed on the substrate (z)-1 was 2 g/m ² .

<<Evaluation of composition for ink-receiving layer>>
The following items were evaluated for the ink-receiving layer composition obtained above. The results are shown in Tables 7 and 8.

<Evaluation of solubility>
The ink-receiving layer composition was visually observed, and the solubility of this ink-receiving layer composition was evaluated according to the following criteria.
(Evaluation criteria)
A: No solid matter was observed in the composition, and no turbidity was observed.
B: Slight thickening or slight clouding of the composition over time is observed, but no solid matter is observed.
C: Slight thickening or slight clouding of the composition over time is observed, and solid matter is observed.

<Measurement of viscosity>
Using a Brookfield viscometer (manufactured by Toki Sangyo Co., Ltd.), the viscosity of the ink-receiving layer composition was measured under an environment of 23° C. and a rotor rotation speed of 30 rpm. Then, based on the measured values, the gravure offset printability of this ink-receiving layer composition was evaluated according to the following criteria.
(Evaluation criteria)
A: The viscosity is 300 mPa·s or more, and the suitability for gravure offset printing is high.
B: The viscosity is 200 mPa·s or more and less than 300 mPa·s, and the gravure offset printability is inferior to that of "A", but it has the gravure offset printability.
C: Viscosity of less than 200 mPa·s and no suitability for gravure offset printing.

<Evaluation of Corrosion Suppression Effect>
A test ink-receiving layer composition (solution) was prepared which was the same as the ink-receiving layer composition obtained above except that it contained no polysaccharide.
The obtained composition for test ink-receiving layer and the iron member (iron washer) were mixed at a ratio of [test ink-receiving layer composition (parts by mass)]:[iron member (parts by mass)] = 85:15. It was enclosed in a glass bottle at a mass ratio, and the iron member was immersed in the test ink-receiving layer composition and sealed. In this state, the iron member and the test composition for ink-receiving layer were allowed to stand at a temperature of 28° C. for 72 hours. As the iron members, those having polished surfaces and having no corroded portions were used.

Using an ultraviolet-visible spectrophotometer ("V-770" manufactured by JASCO Corporation), the test ink-receiving layer composition before being sealed in a glass bottle (before coexisting with an iron member) was measured at a wavelength of 380 to 780 nm. The absorption spectrum was measured in the region, and the values of L ^* , a ^* and b ^* (L ₀ ^* , a ₀ ^* and b ₀ ^* ) were calculated in advance. Further, the values of L ^* , a ^* and b ^* ( _L1 ^* , _a1 ^* and _b1 ^* ) of the test ink-receiving layer composition after being immersed for 72 hours under the above conditions were calculated in the same manner. bottom. When calculating these L ^* , a ^* and b ^* , the conditions of illuminant D65 and 2° field of view were adopted. Then, from these calculated values, the color difference (ΔE) of the test ink-receiving layer composition before and after immersion was calculated. Then, from this ΔE, the corrosion inhibiting effect of the composition for the ink-receiving layer on iron members was evaluated according to the following criteria. The values in parentheses in the column of "corrosion inhibitory effect" in Tables 7 and 8 are ΔE.
(Evaluation criteria)
A: ΔE≦1.
B: 1<ΔE≦7.
C: 7<ΔE≦40.
D: 40<ΔE.

<<Evaluation of inkjet recording sheet>>
The following items were evaluated for the ink jet recording sheet obtained above. The results are shown in Tables 7 and 8.

<Evaluation of dryness of ink>
Using an inkjet printer, printing was performed on the ink-receiving layer of the inkjet recording sheet with four color inks of cyan, magenta, yellow and black. More specifically, the printing was performed by changing the printing density from 100% to 400% in units of 10% for each color.
Next, immediately after printing, a transparent polyethylene terephthalate film (thickness: 100 μm) was superimposed on the printed surface of the inkjet recording sheet and pressed firmly to adhere.
Next, while the film is kept in close contact with the printing surface, the film is visually observed from the side opposite to the surface in close contact with the printing surface to confirm the maximum print density of the ink that has not been transferred from the printing surface to the close contact surface. Then, the drying property of the ink was evaluated according to the following criteria. The values in parentheses in the "Ink dryness" columns in Tables 7 and 8 are the maximum print densities. In this evaluation method, it was previously confirmed that the evaluation results would not vary as long as the film was in close contact with the printed surface.
(Evaluation criteria)
A: The ink has a maximum print density of 300% or more, is excellent in drying properties, and has suitability for high-speed printing.
B: The maximum print density of the ink is 190% or more and less than 300%, the drying property is good, and the ink has suitability for high-speed printing.
C: The ink has a maximum print density of less than 190%, is poor in drying properties, and does not have suitability for high-speed printing.

<Evaluation of Effect of Suppressing Dot Bleeding>
The effect of suppressing dot bleeding was evaluated by the dot shape factor. More specifically, it is as follows.
That is, using a desktop inkjet printer, the printing speed is set to 76.2 m/min (250 feet/min), and a water-based black pigment ink having a size of 2 cm x 2 cm does not overlap on the ink-receiving layer of the inkjet recording sheet. An evaluation sample was prepared by printing (single-color printing) at a density of 10%.
Next, a microscopic image of the surface of the inkjet recording sheet was taken, and the image was analyzed using a dot analyzer (“DA6000” manufactured by Oji Scientific Instruments). Specifically, the peripheral length and area of the dots were measured, and the dot shape factor was calculated by the following formula.
Dot shape factor = (perimeter) ² / (4π x area)

The dot shape coefficient is 1 when the dot is a perfect circle, and increases as the dot shape is farther from the perfect circle, that is, as the dot blurs. Prior to this evaluation, the dot shape factor measured using a desktop inkjet printer at a printing speed of 76.2 m / min (250 feet / min) was 152.4 m / min using a high-speed inkjet printer. It was previously confirmed that there is a sufficient correlation with the dot shape factor measured as (500 feet/min).

By the above method, the dot shape factor was calculated for about 30 dots, the average value was obtained, and the effect of suppressing dot bleeding was evaluated according to the following criteria. The values in parentheses in the "dot bleeding" column in Tables 7 and 8 are the average values of the dot shape coefficients.
(Evaluation criteria)
A: The average value of the dot shape factor is 1.3 or less, the dots are extremely circular, and the bleeding of the dots is most highly suppressed.
B: The average value of the dot shape factor is more than 1.3 and 1.5 or less, and although the dots are inferior to those of "A", they are fairly close to perfect circles, and the bleeding of the dots is highly suppressed. there is
C: The average value of the dot shape factor is more than 1.5 and 1.8 or less, and although the dots are inferior to those of "B", they are close to perfect circles and the bleeding of the dots is suppressed.
D: The average value of the dot shape factor exceeds 1.8 and is 2.0 or less, and the bleeding of the dots is not suppressed to some extent.
E: The average value of the dot shape coefficients exceeds 2.0, and the bleeding of dots is further suppressed than in the case of "D".

<<Production and Evaluation of Composition for Ink-Receiving Layer, Production and Evaluation of Inkjet Recording Sheet>>
[Examples 2 to 35]
Any one of the type of substrate, the type of ingredients in the composition for the ink-receiving layer, the amount of the ingredients in the composition for the ink-receiving layer, and the amount of the ink-receiving layer formed on the substrate. , and an ink-receiving layer composition and an inkjet recording sheet were produced and evaluated in the same manner as in Example 1, except that they were as shown in Tables 5 and 6. The results are shown in Tables 7 and 8.
In Tables 5 and 6, the description of "-" in the column of the compounding component means that the component is not compounded.

<<Production and Evaluation of Inkjet Recording Sheet>>
[Comparative Example 1]
An inkjet recording sheet was produced and evaluated in the same manner as in Example 1, except that the composition for ink-receiving layer was not used. Table 8 shows the results.

In this comparative example, since no ink-receiving layer composition was used, all components for obtaining this were not blended.

[Comparative Example 2]
An ink-jet recording sheet was produced and evaluated in the same manner as in Example 2, except that the ink-receiving layer composition was not used. Table 8 shows the results.
In this comparative example as well, no ink-receiving layer composition was used, and therefore, all components for obtaining this composition were not blended.

<<Production and evaluation of composition for ink-receiving layer>>
[Comparative Examples 3-6, Reference Examples 1-2]
The ink-receiving layer composition was prepared in the same manner as in Example 1, except that both the types and amounts of the ingredients in the composition for the ink-receiving layer were as shown in Table 5 or Table 6. Compositions were prepared and evaluated. The results are shown in Tables 7 and 8.

In Comparative Examples 3 to 6 and Reference Examples 1 and 2, as will be described later, inkjet recording sheets were not produced and evaluated. In Tables 5 and 6, "-" in the column of base material means that no base material was used, and "-" in the column of ink-receiving layer formation amount (g/m ² ) means that no ink-receiving layer was formed. The description of "-" in the column of evaluation results in Tables 7 and 8 means that the item has not been evaluated.

As is clear from the above results, the ink-receiving layer compositions of Examples 1 to 35 did not contain solid matter, had high solubility, and had coatability. In addition, the ink-receiving layer compositions of Examples 1 to 35 had a viscosity of 229 mPa·s or more (229 to 1469 mPa·s), and were highly viscous and suitable for gravure offset printing. In particular, the ink-receiving layer compositions of Examples 1 to 7, 10, 11, 13 to 22, 25 to 32, and 35 had a viscosity of 312 mPa·s or more (312 to 1469 mPa·s). Therefore, it was highly suitable for gravure offset printing. Furthermore, the ink-receiving layer compositions of Examples 1 to 7, 10, 11, and 13 to 20 had viscosities of 436 mPa·s or more (436 to 1469 mPa·s). The printability was particularly high.

The ink-receiving layer compositions of Examples 1 to 35 contained an alkylamine-epichlorohydrin polycondensate or polyamine as a cationic resin, and the content of the cationic resin relative to the total mass of the ink-receiving layer composition was The proportion was between 5 and 20% by weight.
In addition, the ink-receiving layer compositions of Examples 1 to 35 contained, as polysaccharides, either one or both of condensates of mannose and galactose and condensates of glucose, mannose and glucuronic acid. The ratio of the polysaccharide content to the total mass of the receiving layer composition was 0.3 to 0.75% by mass.

The inkjet recording sheets of Examples 1 to 35 had good ink drying properties and high-speed printability due to the use of the ink-receiving layer composition described above. In particular, the ink jet recording sheet of Example 1 had a high ink drying property.

As described above, the ink-receiving layer compositions of Examples 1 to 35 do not need to reduce the printing speed more than necessary during gravure offset printing, and have good printability. An ink-receiving layer with good ink drying properties could be formed.

Furthermore, the inkjet recording sheets of Examples 2 to 35 had the effect of suppressing dot bleeding. The inkjet recording sheet of Example 1 did not have the effect of suppressing dot bleeding, but dot bleeding can be improved by adjusting the ingredients of the composition for the ink-receiving layer and selecting the type of substrate. It is considered to be

On the other hand, the ink-receiving layer compositions of Examples 21 to 26, 29, 30, 33 to 35 had an effect of inhibiting corrosion of iron members. The ink-receiving layer compositions of these Examples contained a base, and the content of the base was 0.5 to 1% by mass with respect to the total mass of the ink-receiving layer composition.

On the other hand, the ink-jet recording sheets of Comparative Examples 1 and 2 did not use the ink-receiving layer composition and did not form an ink-receiving layer, and therefore did not have the effect of the ink-receiving layer. Furthermore, the inkjet recording sheet of Comparative Example 2 was inferior in ink drying property and did not have suitability for high-speed printing.

The ink-receiving layer compositions of Comparative Examples 3, 5 and 6, and Reference Examples 1 and 2 contained solid matter, had low solubility, had no coatability, and were not spread on the substrate. Normal coating was impossible. Therefore, in these comparative examples and reference examples, inkjet recording sheets were not manufactured and evaluated. Further, the viscosities of the ink-receiving layer compositions of these comparative examples and reference examples were not measured because it was impossible to accurately measure the viscosities due to the influence of solid matter.

The ink-receiving layer compositions of Comparative Examples 3, 5 and 6 contained other polymers (polyvinyl alcohol, sodium carboxymethyl cellulose or cellulose nanofibers) instead of the polysaccharide.
The ink-receiving layer compositions of Reference Examples 1 and 2 contained an alkylamine-epichlorohydrin polycondensate as a cationic resin, and the proportion of the content of the cationic resin relative to the total mass of the ink-receiving layer composition was , 15% by mass, and further contains a condensate of mannose and galactose as a polysaccharide, and the ratio of the content of the polysaccharide to the total mass of the composition for the ink-receiving layer is 0.5% by mass. However, the composition containing sodium carbonate (Reference Example 1) or sodium hydroxide as a base, and the ratio of the content of the base to the total weight of the composition for the ink-receiving layer was 1.5% by mass. It was (Reference Example 2).

The ink-receiving layer composition of Comparative Example 4 had too low a viscosity and did not have suitability for gravure offset printing. Therefore, in Comparative Example 4, an inkjet recording sheet was not manufactured and was not evaluated.
The composition for the ink-receiving layer of Comparative Example 4 contained another polymer (the same polyvinyl alcohol as in Comparative Example 3) instead of the polysaccharide, and the content thereof was higher than that of Comparative Example 3. It was less.

INDUSTRIAL APPLICABILITY The present invention can be used as an inkjet recording sheet, particularly as an inkjet recording sheet suitable for high-speed printing.

Reference Signs List 1, 2... Ink jet recording sheet 11... Base material 11a... First side of base material 11b... Second side of base material 12... Ink receiving layer 12a. First surface of ink-receiving layer 12b Second surface of ink-receiving layer 121 First ink-receiving layer 121a First surface of first ink-receiving layer 121b Second surface of first ink-receiving layer 122 Second ink-receiving layer 122a First surface of second ink-receiving layer 122b Second surface of second ink-receiving layer

Claims (5)

An ink-receiving layer composition for forming an ink-receiving layer included in an inkjet recording sheet,
The ink-receiving layer composition contains a cationic resin, a polysaccharide and water,
The cationic resin is one or more selected from the group consisting of polyamines and polycondensates of epichlorohydrin,
The polysaccharide is one or more condensates selected from the group consisting of glucose, galactose, mannose and glucuronic acid,
In the ink-receiving layer composition, the content of the cationic resin is 3 to 30% by mass with respect to the total mass of the ink-receiving layer composition,
The ink-receiving layer composition, wherein the content of the polysaccharide is 0.3 to 1.3% by mass with respect to the total mass of the ink-receiving layer composition. 2. The composition for an ink-receiving layer according to claim 1, wherein said polysaccharide is one or both of guar gum and xanthan gum. An inkjet recording sheet comprising a substrate and an ink-receiving layer formed on at least one surface of the substrate,
The ink-receiving layer contains a cationic resin and a polysaccharide,
The cationic resin is one or more selected from the group consisting of polyamines and polycondensates of epichlorohydrin,
The polysaccharide is one or more condensates selected from the group consisting of glucose, galactose, mannose and glucuronic acid,
In the ink-receiving layer, the content of the cationic resin is 70 to 99% by mass with respect to the total mass of the ink-receiving layer,
The inkjet recording sheet, wherein the content of the polysaccharide in the ink-receiving layer is 1 to 30% by mass with respect to the total mass of the ink-receiving layer. 4. The inkjet recording sheet of claim 3, wherein the polysaccharide is one or both of guar gum and xanthan gum. 5. A method for producing an inkjet recording sheet according to claim 3 or 4,
3. An inkjet ink-receiving layer composition comprising the step of applying the composition for an ink-receiving layer according to claim 1 or 2 onto at least one surface of a substrate at a speed of 304.8 m/min or more by a gravure offset printing method. A method of manufacturing a recording sheet.

Images