JP2018171858A - Recording sheet for inkjet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording sheet for inkjet which has good dryness of ink, can suppress of blurring of the ink, and has an ink-receiving layer having water resistance.SOLUTION: A recording sheet 1 for inkjet has a base material 11 and an ink-receiving layer 12 formed on at least one surface 11a of the base material 11, where the ink-receiving layer 12 contains first and second aggregation type light calcium carbonates having different average secondary particle diameters as a pigment and a cationic styrenic resin as a binder, in the ink-receiving layer 12, a ratio of a content of the cationic styrenic resin with respect to the total content of the first and second aggregation type light calcium carbonates is 6.5 to 25 mass%, and a ratio of a content of the cationic styrenic resin with respect to the total content of a component other than the first and second aggregation type light calcium carbonates is 65 mass% or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ink jet recording sheet.

Information recording systems using ink-jet inks are widely used because full-color high-quality images can be easily obtained, and high-quality images close to those of silver halide photography can be realized by recent technological advances.
As inks, water and water-based inks containing various colorants in a solvent such as water and a mixed solvent of water and a hydrophilic organic solvent, and oil-based inks containing an oil-soluble colorant in a hydrophobic organic solvent Ink is used, and it is used properly according to the purpose.

  An ink jet recording sheet is configured by providing an ink receiving layer for absorbing ink and forming a print or image on a substrate such as paper. The ink receiving layer is required to have good ink drying properties and to suppress ink bleeding, which is particularly important when performing high-speed printing. The ink receiving layer can be formed by applying and drying a composition containing components necessary for fixing the ink and a dispersion medium for dispersing them.

  On the other hand, an ink jet recording sheet may be used in an environment wet with water due to expansion of applications. In this case, it is desired that the ink jet recording sheet sufficiently exhibit its function even in the presence of water. For example, an ink jet recording sheet may be used as a label for frozen home delivery. In this case, water may adhere to the inkjet recording sheet due to condensation, and it is considered that printing or images cannot be read due to rubbing between sheets in such a state. It is expected that the occurrence of such defects can be suppressed.

  As an ink jet recording sheet having improved water resistance, an ink receiving layer containing a pigment, an adhesive, a cationic sizing agent, and two or more cationic resins having a degree of cationization and a molecular weight within a specific range ( What is provided with the receiving layer) is disclosed (refer patent document 1).

Japanese Patent No. 4042970

  However, the ink jet recording sheet disclosed in Patent Document 1 has a high effect of suppressing bleeding due to adhesion of moisture for printing and images, but the water resistance of the ink receiving layer itself is insufficient and is wet with water. There is a problem that the ink receiving layer is easily broken or peeled off when used in an environment.

  The present invention has been made in view of the above circumstances, and provides an ink jet recording sheet provided with an ink receiving layer that has good ink drying properties, can suppress ink bleeding, and has water resistance. Let it be an issue.

  The present invention is an ink jet recording sheet comprising a base material and an ink receiving layer formed on at least one surface of the base material, wherein the ink receiving layer has an average secondary particle as a pigment. The first and second aggregated light calcium carbonates having different diameters are contained, the ink receiving layer contains a cationic styrene resin as a binder, and the first and second aggregated light carbonates are contained in the ink receiving layer. The ratio of the content of the cationic styrene resin to the total content of calcium is 6.5 to 25% by mass, and in the ink receiving layer, the components other than the first and second aggregated light calcium carbonates An ink jet recording sheet is provided in which the ratio of the content of the cationic styrene resin to the total content of is 65% by mass or more.

  In the inkjet recording sheet of the present invention, the average secondary particle diameter of the first aggregated light calcium carbonate is less than 1 μm, and the average secondary particle diameter of the second aggregated light calcium carbonate is 2 to 5 μm. In the ink receiving layer, the ratio of [content (mass) of first aggregated light calcium carbonate]: [content (mass) of second aggregated light calcium carbonate] is 22:78 to 78:22. Preferably there is.

  According to the present invention, there is provided an ink jet recording sheet provided with an ink receiving layer having good ink drying properties, suppressing ink bleeding, and having water resistance.

It is sectional drawing which shows typically one Embodiment of the recording sheet for inkjets of this invention. It is sectional drawing which shows typically other embodiment of the recording sheet for inkjet of this invention.

<< Inkjet recording sheet >>
The inkjet recording sheet of the present invention is an inkjet recording sheet comprising a base material and an ink receiving layer formed on at least one surface of the base material, wherein the ink receiving layer is used as a pigment. The first and second aggregated light calcium carbonates having different average secondary particle diameters are contained, and the ink receiving layer contains a cationic styrenic resin as a binder. In the ink receiving layer, the first and second aggregated light calcium carbonates are contained. The ratio of the content of the cationic styrenic resin to the total content of the aggregated light calcium carbonate of 2 is 6.5 to 25% by mass. In the ink receiving layer, the first and second aggregated light calcium carbonates are included. The ratio of the content of the cationic styrene resin to the total content of components other than calcium carbonate is 65% by mass or more.

  In the ink jet recording sheet of the present invention, since the ink receiving layer has the above-mentioned limited composition, the ink drying property is good, the ink bleeding can be suppressed, and the ink receiving layer has water resistance. In this way, it is possible to stably hold prints and images.

<Ink receiving layer>
The ink receiving layer can be formed using an ink receiving layer composition containing a component for constituting the ink receiving layer. More specifically, the ink receiving layer can be formed by applying the ink receiving layer composition onto a substrate and drying it.
In addition, as will be described later, the surface of the formed ink receiving layer may be further subjected to a calendar process (smoothing process).
The calendar process is a process of smoothing the surface of the sheet by pressurizing it, and the surface of the sheet may be heated at the same time.

  The ratio of the content of components that do not vaporize at room temperature in the ink receiving layer composition is usually the same as the content ratio of the components of the ink receiving layer. In the present specification, “normal temperature” means a temperature that is not particularly cooled or heated, that is, a normal temperature, and includes a temperature of 15 to 25 ° C., for example.

Application of the ink-receiving layer composition onto the substrate may be performed once or may be performed in multiple steps. In the case where the coating is performed in a plurality of times, the ink receiving layer composition is further coated on the dried coating layer, and the ink receiving layer is further coated on the non-dried coating layer. Any of the methods for applying the layer composition may be used.
The coating amount of the ink receiving layer composition may be appropriately adjusted in consideration of the solid content concentration of the ink receiving layer composition, the thickness of the ink receiving layer, and the like.

  The method for applying the ink receiving layer composition is not particularly limited, and any method can be used as long as it can apply a liquid material. Specific coating methods include, for example, various types of coaters such as air knife coaters, curtain coaters, die coaters, blade coaters, roll coaters, gate roll coaters, bar coaters, rod coaters, gravure coaters, gravure offset coaters; wire bars A known method using an apparatus such as a coater may be mentioned.

  The coated ink receiving layer composition may be dried by a known method such as air drying or heating air drying. Conditions such as drying temperature and drying time may be appropriately set according to the drying method.

The amount of the ink receiving layer formed on the substrate is preferably 4 g / m ² or more, more preferably 4.5 g / m ² or more, and particularly preferably 5 g / m ² or more. When the amount of the ink receiving layer formed is equal to or more than the lower limit value, for example, the effect of suppressing ink bleeding is higher, particularly when at least the surface of the ink receiving layer is calendered using a calendar device. This effect is higher.
On the other hand, the upper limit of the formation amount of the ink receiving layer on the substrate is not particularly limited, and may be, for example, 30 g / m ² .
The formation amount of the ink receiving layer is preferably in a range set by appropriately combining any one of the above lower limit value and upper limit value.

  The amount of the ink receiving layer formed can be adjusted, for example, by adjusting the amount of the ink receiving layer composition applied onto the substrate or the amount of each compounding component of the ink receiving layer composition. .

The ink jet recording sheet of the present invention may be provided with an ink receiving layer on at least one surface of the substrate, and may be provided only on one side or on both sides.
When the ink jet recording sheet of the present invention includes ink receiving layers on both sides of the base material, these two ink receiving layers may be the same or different from each other.

<Ink-receiving layer composition>
Examples of the ink receiving layer composition include the pigment, a binder, and, if necessary, other components not corresponding to any of these.
Hereinafter, each component will be described.

[Pigment]
The pigment is a component that retains the pigment in the ink and affects the absorption and transmission of moisture in the ink receiving layer.
The ink receiving layer composition and the ink receiving layer contain, as the pigment, first aggregated light calcium carbonate and second aggregated light calcium carbonate having different average secondary particle diameters.

Calcium carbonate includes heavy calcium carbonate and light calcium carbonate.
Heavy calcium carbonate is obtained by pulverizing and classifying natural limestone.
Light calcium carbonate is chemically synthesized, and the shape and size of the particles can be chemically controlled. The shape of the light calcium carbonate particles is usually cubic, spindle or columnar. There are light calcium carbonates in which primary particles are present as simple particles and those in which primary particles are aggregated to form secondary particles.
Light calcium carbonate in which primary particles aggregate to form secondary particles is referred to as aggregated light calcium carbonate. The average particle diameter of the primary particles (average primary particle diameter) is obtained from the observation result with a scanning electron microscope, for example. The average particle diameter of the secondary particles can be obtained by measurement with a laser diffraction method, for example.
In the present invention, the first agglomerated light calcium carbonate and the second agglomerated light calcium carbonate having different average secondary particle diameters are used as the pigment.

The average secondary particle diameter of the first agglomerated light calcium carbonate is preferably less than 1 μm, more preferably 0.9 μm or less, for example, 0.8 μm or less, 0.7 μm or less, and 0.6 μm or less. Although these may be any of these, these are examples.
On the other hand, the lower limit value of the average secondary particle diameter of the first aggregated light calcium carbonate is not particularly limited, and may be 0.2 μm, for example.
When the ink receiving layer contains the first aggregated light calcium carbonate, the effect of suppressing ink bleeding when ink jet printing is performed on the ink jet recording sheet is further enhanced.

The average secondary particle diameter of the second agglomerated light calcium carbonate is preferably 2 to 5 μm, more preferably 2.3 to 4.7 μm, for example 2.6 to 4.4 μm. This is just an example.
When the ink receiving layer contains the second agglomerated light calcium carbonate, the drying property of the ink becomes higher when ink jet printing is performed on the ink jet recording sheet. Here, “the ink has a high drying property” means “the time required for drying the ink is short”.

The ink receiving layer preferably contains any one of the above-mentioned average secondary particle diameters as the first aggregated light calcium carbonate and the second aggregated light calcium carbonate in appropriate combination. For example, as a preferable combination of the first aggregated light calcium carbonate and the second aggregated light calcium carbonate in the ink receiving layer, the first secondary particle diameter is less than 1 μm (for example, 0.2 μm or more and less than 1 μm). A combination of the agglomerated light calcium carbonate and the second agglomerated light calcium carbonate having an average secondary particle diameter of 2 to 5 μm is mentioned, but this is an example.
As described above, since the ink receiving layer contains both the first aggregated light calcium carbonate and the second aggregated light calcium carbonate, the ink jet recording sheet can be used even when color printing is performed by a high speed ink jet printer. The drying property of the is improved.

  In the ink receiving layer composition and the ink receiving layer, the ratio of [content of first aggregated light calcium carbonate (mass)]: [content of second aggregated light calcium carbonate (mass)] is not particularly limited. Is preferably 10:90 to 90:10, more preferably 16:84 to 84:16, and particularly preferably 22:78 to 78:22. The content of the first agglomerated light calcium carbonate is preferably large in that the effect of suppressing ink bleeding is higher, and the content of the second agglomerated light calcium carbonate is preferred in that the drying property of the ink is higher. It is preferable that there are many. In addition, the ratio of [content (mass) of first agglomerated light calcium carbonate]: [content (mass) of second agglomerated light calcium carbonate] is in the above-described range, whereby the recording sheet for ink jet recording In addition, both the improvement of the ink bleeding suppression effect and the improvement of the drying property can be achieved in a well-balanced manner, and the ink jet recording sheet has a better ink drying property even when color printing is performed with a high-speed ink jet printer. It becomes good.

The composition for an ink receiving layer and the ink receiving layer do not fall under any of the first aggregated light calcium carbonate and the second aggregated light calcium carbonate, as long as the effects of the present invention are not impaired. A pigment may be contained.
Examples of the other pigment include, for example, non-aggregated light calcium carbonate (that is, light calcium carbonate in which primary particles are not aggregated to form secondary particles); Calcium carbonate other than the aggregated light calcium carbonate 2 is mentioned.

  Each of the first and second aggregated light calcium carbonates and the other pigments may be used alone, in combination of two or more, or in combination of two or more. The combination and ratio may be appropriately selected according to the purpose.

  In the ink receiving layer composition and the ink receiving layer, the ratio of the total content of the first and second aggregated light calcium carbonates to the total pigment content is preferably 92% by mass or more, and 94% by mass. More preferably, it is more preferably 96% by mass or more, particularly preferably 98% by mass or more, and may be 100% by mass.

In the ink receiving layer composition, the ratio of the pigment content to the total content of components other than the solvent described later (that is, the pigment content in the ink receiving layer) is preferably 70 to 95% by mass, More preferably, it is 75-95 mass%, and it is especially preferable that it is 80-95 mass%. When the ratio is equal to or higher than the lower limit value, the effect of using the pigment is more remarkably obtained. Further, when the ratio is equal to or less than the upper limit value, the strength of the ink receiving layer becomes higher.
In the present specification, the “pigment content” refers to all pigments used, including not only the first and second aggregated light calcium carbonates but also other pigments, unless otherwise specified. The content (that is, the total content of pigments) is meant.

[binder]
The binder is a component for holding the pigment (first and second aggregated light calcium carbonate and the like) contained in the ink receiving layer.
The ink receiving layer composition and the ink receiving layer contain a cationic styrene resin as the binder.
The cationic styrenic resin is a component that largely affects the water resistance of the ink receiving layer, and also affects the drying and bleeding of the ink in the ink receiving layer.

Cationic styrenic resins have structural units derived from styrene and exhibit cationic properties when dissolved or dispersed in water.
The cationic styrenic resin is not particularly limited as long as it is such, and may have, for example, only a structural unit derived from styrene or a derivative thereof, or a structure derived from styrene or a derivative thereof. You may have a unit and structural units other than these.
Further, the cationic styrene resin may be a copolymer of a resin having a structural unit derived from styrene or a derivative thereof and another resin other than this, and as such a copolymer, Examples thereof include a copolymer of a resin having a structural unit derived from styrene or a derivative thereof and an acrylic resin (a resin having a (meth) acryloyl group).

In the present specification, the term “derivative” or “class” means that one or more hydrogen atoms of the original compound are substituted with a group other than a hydrogen atom unless otherwise specified. Here, the “group” includes not only an atomic group formed by bonding a plurality of atoms but also one atom.
Further, the “(meth) acryloyl group” is a concept including both “acryloyl group” and “methacryloyl group”. The same applies to terms similar to the (meth) acryloyl group. For example, “(meth) acrylic acid” is a concept including both “acrylic acid” and “methacrylic acid”, and “(meth) acrylate” "Is a concept including both" acrylate "and" methacrylate ".

The weight average molecular weight of the cationic styrenic resin is preferably 5,000 to 110,000.
In the present specification, the weight average molecular weight is a polystyrene conversion value measured by a gel permeation chromatography (GPC) method unless otherwise specified.

The composition for ink-receiving layer and the ink-receiving layer may contain other binders other than the cationic styrenic resin as long as the effects of the present invention are not impaired.
Examples of the other binder include water-soluble polymers other than cationic styrene resins.

Examples of the water-soluble polymer include polyvinyl alcohol; modified polyvinyl alcohol such as cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, and silanol-modified polyvinyl alcohol; oxidized starch; phosphate esterified starch; ); Polyurethanes such as ester polyurethane and carbonate polyurethane.
The polyurethane may be, for example, cationic, anionic or nonionic.

  The cationic styrenic resin and the other binder may be used singly or in combination of two or more, and in the case of using two or more in combination and ratio thereof. May be appropriately selected according to the purpose.

  In the ink receiving layer composition and the ink receiving layer, the ratio of the content of the cationic styrene resin to the total content of the binder is preferably 80% by mass or more, and preferably 85% by mass or more. More preferably, it is particularly preferably 90% by mass or more, for example, either 95% by mass or more and 98% by mass or more, or 100% by mass.

  In the ink receiving layer composition and the ink receiving layer, the ratio of the content of the cationic styrene resin to the total content of the first and second aggregated light calcium carbonates is 6.5 to 25% by mass. Yes, it is preferably 7 to 23% by mass, and particularly preferably 7.3 to 21% by mass. When the ratio is equal to or higher than the lower limit value, the water resistance of the ink receiving layer becomes higher, and when the ratio is equal to or lower than the upper limit value, the drying property of the ink in the ink receiving layer becomes higher.

In the ink receiving layer composition, the ratio of the content of the cationic styrene resin to the total content of components other than the solvent described later and the first and second aggregated light calcium carbonates is 65% by mass or more. It is preferably 65 to 100% by mass, more preferably 70 to 100% by mass, and particularly preferably 75 to 100% by mass.
In other words, in the ink receiving layer, the ratio of the content of the cationic styrenic resin to the total content of components other than the first and second aggregated light calcium carbonates is 65% by mass or more, and 65 to 65%. It is preferably 100% by mass, more preferably 70 to 100% by mass, and particularly preferably 75 to 100% by mass.
When the ratio is equal to or higher than the lower limit, the water resistance of the ink receiving layer is increased. In particular, when a re-releasable sheet is formed by providing a pressure-sensitive adhesive layer having re-removability as described later on the ink receiving layer, the re-releasable sheet after sealing is in a wet state. Even if peeling is performed, the occurrence of abnormality such as breakage or peeling of the ink receiving layer is suppressed. On the other hand, when the ratio is equal to or less than the upper limit value, the effect of suppressing ink bleeding in the ink receiving layer is further increased.

[Other ingredients]
Examples of the other components include solvents, cationic resins other than cationic styrene resins, polyvalent metal salts, pH adjusters, antifoaming agents, foam suppressors, mold release agents, foaming agents, antioxidants, Components commonly used in ink-receiving layers of inkjet recording sheets, such as preservatives, water-resistant agents, paper strength enhancers, colored dyes, colored pigments, dye fixing agents, pigment dispersants, fluorescent brighteners, ultraviolet absorbers, etc. Is mentioned.
As the other components, one kind may be used alone, two or more kinds may be used in combination, and when two or more kinds are used in combination, the combination and ratio thereof may be appropriately selected according to the purpose. Good.

(solvent)
In the ink-receiving layer composition, the other components other than the pigment, binder, or solvent were blended as a dispersion or solution, and no solvent was used other than the dispersion medium or solvent used at that time. In some cases, the solvent means the dispersion medium used for preparing the dispersion or the solvent used for preparing the solution.
In addition to the dispersion medium used for the preparation of the dispersion or the solvent used for the preparation of the solution, when a solvent is separately added, the solvent is the dispersion medium or the solvent, and this is separately added. By both solvents. And when all the said components other than the said pigment, a binder, and a solvent are mix | blended as a solid substance, the said solvent means the solvent mix | blended separately from these.
Examples of the solvent include water, alcohol and the like.

  A solvent may be used individually by 1 type, may use 2 or more types together, and when using 2 or more types together, those combinations and ratios may be suitably selected according to the objective.

  The content of the solvent in the composition for ink receiving layer may be appropriately selected according to the purpose and is not particularly limited, but is preferably 35 to 90% by mass, for example.

(Cationic resins other than cationic styrene resins)
A cationic resin other than the cationic styrenic resin (sometimes referred to herein as a “cationic resin fixing agent”) is suitable as an ink fixing agent in the ink-receiving layer, It exhibits a cationic property when dissolved or dispersed in it.
Among them, the cationic resin fixing agent is preferably a monomer, oligomer or polymer of a primary amine, secondary amine, tertiary amine or quaternary ammonium salt, and may be the oligomer or polymer. More preferred.

More preferable examples of the cationic resin fixing agent include, for example, an alkylamine-epichlorohydrin copolymer; an acrylic polymer having a secondary amino group, a tertiary amino group, or a quaternary ammonium group; polyvinylamine; polyvinylamidine. Dicyandiamide-formalin copolymer and other dicyan cationic resins; dicyandiamide-polyethyleneamine copolymer and other polyamine cationic resins; polyalkylenepolyamines such as polyethylene polyamine and polypropylene polyamine and derivatives thereof; ; diallyldimethylammonium -SO ₂ copolymer; diallylamine salt -SO ₂ copolymer; dimethyldiallylammonium chloride polymer; polymer of allylamine salt; single vinylbenzyl triallyl ammonium salt Polymer or copolymer; Dialkylaminoethyl (meth) acrylate quaternary salt copolymer; Acrylamide-diallylamine salt copolymer; Aluminum salt such as polyaluminum chloride and polyaluminum acetate, and alkylamine-epichlorohydrin copolymer Particularly preferred is a dimethylamine-epichlorohydrin copolymer.

  In the present specification, the polymer includes a polycondensate.

  The cationic resin fixing agent may be used alone or in combination of two or more, and when two or more are used in combination, the combination and ratio thereof may be appropriately selected according to the purpose. That's fine.

  In the ink receiving layer composition and the ink receiving layer, the ratio of the content of the cationic resin fixing agent to the content of the pigment is preferably 1 to 40% by mass, and preferably 1 to 25% by mass. More preferably, for example, it may be any one of 1 to 15% by mass, 1 to 10% by mass, 1 to 6% by mass, and 1 to 4% by mass, but these are examples.

(Polyvalent metal salt)
The polyvalent metal salt is a component for improving the drying property of the ink in the ink receiving layer, and is not particularly limited as long as it contains a metal cation having a valence of 2 or more.

Examples of the polyvalent metal salt include calcium chloride (CaCl ₂ ), magnesium chloride (MgCl ₂ ), aluminum chloride (AlCl ₃ ), barium chloride (BaCl ₂ ), zinc chloride (ZnCl ₂ ), calcium sulfate (CaSO ₄ ). , Magnesium sulfate (MgSO ₄ ), calcium nitrate (Ca (NO ₃ ) ₂ ), magnesium acetate ((CH ₃ COO) ₂ Mg), calcium acetate ((CH ₃ COO) ₂ Ca), potassium aluminum sulfate (potash alum, AlK (SO ₄ ) ₂ ) and the like.
The polyvalent metal salt may be hydrated or non-hydrated.

  Among them, the polyvalent metal salt can improve the ink-jet printing suitability such as the ink drying property and color density in the ink receiving layer, and the water resistance and scratch resistance of the ink receiving layer in a balanced manner, and also has high safety. In this respect, calcium chloride, magnesium chloride, or potassium aluminum sulfate is preferable, and potassium aluminum sulfate is particularly preferable in terms of higher ink drying properties.

  As the polyvalent metal salt, one kind may be used alone, two or more kinds may be used in combination, and when two or more kinds are used in combination, their combination and ratio may be appropriately selected according to the purpose. Good.

  When the ink receiving layer composition and the ink receiving layer contain a polyvalent metal salt, the ink receiving layer preferably contains at least one selected from the group consisting of calcium chloride, magnesium chloride and aluminum potassium sulfate. More preferably, one containing either or both of calcium chloride and magnesium chloride is more preferred. When the ink receiving layer contains at least aluminum potassium sulfate, the drying property of the ink becomes higher.

  When the ink receiving layer composition and the ink receiving layer contain a polyvalent metal salt, the ratio of the content of the polyvalent metal salt to the pigment content in the ink receiving layer composition and the ink receiving layer is as follows: It is preferably 3 to 55% by mass, more preferably 3 to 25% by mass, further preferably 3 to 15% by mass, and particularly preferably 3 to 10% by mass. When the ratio is equal to or higher than the lower limit value, the effect of using the polyvalent metal salt is more remarkably obtained. Moreover, the excessive use of a polyvalent metal salt is suppressed because the said ratio is below the said upper limit.

(Defoamer)
The antifoaming agent is not particularly limited and may be a known one.
An antifoamer may be used individually by 1 type, may use 2 or more types together, and when using 2 or more types together, what is necessary is just to select those combinations and ratios suitably according to the objective. .

  What is necessary is just to adjust suitably the total content of the said other component in the composition for ink receiving layers according to the objective.

  Examples of particularly preferable ink receiving layer compositions and ink receiving layers include a first agglomerated light calcium carbonate having an average secondary particle diameter of less than 1 μm and a second secondary particle diameter of 2 to 5 μm. The ratio of [the content (mass) of the first aggregated light calcium carbonate]: [the content (mass) of the second aggregated light calcium carbonate] is 22:78 to 78:22.

<Method for producing composition for ink receiving layer>
The ink receiving layer composition can be produced by blending the pigment, the binder, and other components as required, and sufficiently stirring these blended components. In the ink receiving layer composition, the pigment is preferably dispersed, and the binder is preferably dissolved or dispersed.

The blending order of each component is not particularly limited.
In addition, when blending each component, all of the components may be added and then mixed, or some components may be mixed while being sequentially added, and all components may be mixed while being sequentially added. May be.
As described above, the solvent may be used in combination with a pigment, a binder, an ink fixing agent, or other components other than the solvent in advance, or may be used alone without being previously mixed with these components. May be used.

The temperature at the time of blending each component is not particularly limited, and may be adjusted as appropriate according to the type of the blend component, but it is usually preferably 15 to 30 ° C.
Stirring may be performed by a known method for preparing a dispersion, such as a method using a mixer. What is necessary is just to adjust stirring time suitably according to the total amount of the composition for ink receiving layers to manufacture, a stirring method, etc., for example, it is preferable that it is 10 minutes-24 hours.

<Base material>
The material of the substrate is not particularly limited and may be selected according to the purpose from those 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 base material include a base material having a residual rate of either 10% or more in the longitudinal direction and the lateral direction in a wet tensile strength test based on JIS P8135: 1998.

  Specific examples of the material of the base material include, for example, water-resistant paper, high-quality paper, art paper, coated paper, cast-coated paper, resin-coated paper, synthetic paper, and the like; polyethylene, polypropylene, polyvinyl chloride, 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, melamine Examples thereof include synthetic resins such as resin, phenol resin, urea resin, polyurethane, and polyimide.

  The thickness of the substrate is not particularly limited as long as the shape of the substrate is a sheet or film, but is preferably 20 to 1000 μm, more preferably 35 to 500 μm, and 50 to 200 μm. It is particularly preferred. When the thickness of the substrate is equal to or more than the lower limit, the structure of the ink receiving layer can be more stably maintained, and when the thickness of the substrate is equal to or less than the upper limit, the handleability as a recording sheet is improved. Better.

The substrate may be composed of a single layer, or may be composed of two or more layers. When the substrate is composed of a plurality of layers, these layers may be the same as or different from each other. That is, all the layers may be the same, all the layers may be different, or only some of the layers may be different. And when several layers differ from each other, the combination of these several layers is not specifically limited. Here, the plurality of layers being different from each other means that at least one of the material and the thickness of each layer is different from each other.
In addition, when a base material consists of multiple layers, it is good to make it the total thickness of each layer be the thickness of said preferable base material.

  As a base material, a commercial item may be used and what was manufactured by the well-known method may be used.

<< Method for producing inkjet recording sheet >>
The ink jet recording sheet of the present invention can be produced by forming an ink receiving layer on at least one surface of a substrate.
The method for forming the ink receiving layer is as described above.

  When the ink jet recording sheet of the present invention is calendered (smoothed), the calendering may be performed on at least the surface of the ink receiving layer after the ink receiving layer is formed.

  For example, machine calendar, TG calendar, super calendar, soft calendar, gloss calendar, compact calendar, mat super calendar, mat calendar are known as the calendar process (smoothing process) for the ink jet recording sheet (the surface of the ink receiving layer). This can be done using a calendar device.

The calendar device may be any of an off type separated from the coater and an on type integrated with the coater.
Among the calendar devices, the roll includes, for example, a rigid roll and an elastic roll.
Examples of the rigid roll include a metal roll and a roll whose metal surface is mirror-finished with hard chrome plating or the like.
Examples of the elastic roll include a roll made of resin such as polyurethane, epoxy resin, polyamide, phenol resin, or polyacrylate; a roll formed of cotton, nylon, asbestos, aramid fiber, or the like.

  The conditions for calendering are appropriately selected according to the required quality depending on the temperature of the rigid roll, calendering pressure, number of nips, roll speed, paper moisture before calendering, and the like.

  Although the processing temperature at the time of a calendar process is not specifically limited, For example, it can be 10-25 degreeC.

  Although the pressure at the time of a calendar process is not specifically limited, For example, it can be set as 50-400 kN / m.

  The pressure at the time of calendar processing is adjusted, for example, by adjusting the pressure when pressing a pair of rolls in the calendar device against the inkjet recording sheet to be processed and the distance between the roll surfaces of the pair of rolls. it can. The method of adjusting the pressure during calendar processing by adjusting the distance between roll surfaces is suitable for calendar processing on a small scale. For example, the pressure during the calendar process can be easily adjusted by setting the distance between the roll surfaces to preferably 10 to 400 μm according to the thickness of the inkjet recording sheet to be processed.

Next, the overall configuration of the inkjet recording sheet of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing an embodiment of an inkjet recording sheet of the present invention. FIG. 2 is a cross-sectional view schematically showing another embodiment of the ink jet recording sheet of the present invention.
In FIG. 2, the same components as those shown in FIG. 1 are denoted by 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, for the sake of convenience, a part that is a main part may be shown in an enlarged manner, and the dimensional ratios and the like of each component are the same as in practice. Not necessarily.

The ink jet recording sheet 1 shown in FIG. 1 includes an ink receiving layer 12 only on one surface 11a (which may be referred to as “first surface” in this specification) of a base material 11.
Also, the inkjet recording sheet 2 shown in FIG. 2 is on the first surface 11a of the substrate 11 and on the other surface (sometimes referred to as “second surface” in this specification) 11b (that is, on both surfaces). In addition, both are provided with an ink receiving layer 12. As for the two ink receiving layers 12 and 12 in the inkjet recording sheet 2, those provided on the first surface 11 a of the base material 11 are shown as the first ink receiving layer 121 as necessary. 11 provided on the second surface 11b are shown as the second ink receiving layer 122 to distinguish from each other.

In FIG. 1, reference numeral 12a indicates the surface of the ink receiving layer 12 opposite to the substrate 11 side (in this specification, it may be referred to as “first surface”), and reference numeral 12b indicates the ink. The surface of the receiving layer 12 on the substrate 11 side (in the present specification, sometimes referred to as “second surface”) is shown.
In FIG. 2, reference numerals 12a, 121a, and 122a denote surfaces of the ink receiving layer 12, the first ink receiving layer 121, and the second ink receiving layer 122 on the side opposite to the substrate 11 side (first surface). Reference numerals 12b, 121b, and 122b denote surfaces (second surfaces) on the substrate 11 side of the ink receiving layer 12, the first ink receiving layer 121, and the second ink receiving layer 122, respectively.

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

  However, the ink jet recording sheet shown in FIGS. 1 and 2 is only an example of the present invention, and the ink jet recording sheet of the present invention is not limited thereto.

In the ink jet recording sheet of the present invention, the ink receiving layer may be provided on the entire surface to be formed on the substrate, or may be provided only in a part of the region.
When the ink jet recording sheet of the present invention is viewed from above on the side where the ink receiving layer is provided and viewed in plan, the surface area of the ink receiving layer may be equal to or less than the surface area of the substrate. As long as the conditions are satisfied, there is no particular limitation. In addition, the shapes of the ink receiving layer and the base material when viewed in plan in this way can be arbitrarily set according to the purpose, and are not particularly limited.

The ink jet recording sheet of the present invention may be provided with a layer other than the ink receiving layer on the substrate, depending on the purpose.
As said other layer, an adhesive layer, an adhesive bond layer, a peeling film etc. are mentioned, for example.

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

As the adhesive layer, for example, after the overlapping surfaces of the sheets are bonded to each other, by peeling them off, it is possible to make the state peeled again without damaging the overlapping surfaces of the sheets, so-called There may also be mentioned a pressure sensitive adhesive layer for releasably bonding sheets together.
The pressure sensitive adhesive layer may be provided on the ink receiving layer.

  The inkjet recording sheet provided with the pressure-sensitive adhesive layer may be in a state where the sheet to be bonded is removably bonded to the pressure-sensitive adhesive layer, or the sheet to be bonded is bonded. It may not be necessary, and one ink jet recording sheet may be folded and removably adhered by the pressure sensitive adhesive layer.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the following examples.

<Base material>
In the following examples and comparative examples, the following materials were used as substrates.

<Raw material>
In the following examples and comparative examples, the following pigments and binders were used.

In the following examples and comparative examples, the following materials were used as raw materials other than the pigment and binder.
[Cationic resin fixing agent]
(C) -1: Alkylamine-epichlorohydrin polycondensate ("Jetfix 260" manufactured by Satoda Chemical Industries)
[Multivalent metal salt]
(D) -1: Calcium chloride (d) -2: Potassium aluminum sulfate (potash alum)

<< Manufacture of inkjet recording sheet >>
[Example 1]
The binder (b) -1 (7.5 parts by mass (solid content)) is added to the pigment (a) -1 (25 parts by mass) and the pigment (a) -2 (75 parts by mass), which is sufficient at room temperature. The components were dispersed by stirring to obtain an ink-receiving layer composition as a dispersion.
Next, using the wire bar coater, the composition for the ink receiving layer obtained above was coated on the substrate (z) -1 at a coating amount such that the amount of the ink receiving layer formed was 5 g / m ^2. Then, it was dried at 105 ° C. to form an ink receiving layer having a thickness of about 10 μm to obtain an ink jet recording sheet.
Further, the inkjet recording sheet was calendered at room temperature to obtain the intended inkjet recording sheet. During the calendar process, the distance between the roll surfaces of the pair of metal rolls was set to 25 μm, and the ink jet recording sheet was pressed between the roll surfaces by passing the ink jet recording sheet therebetween.

[Examples 2-7, Comparative Examples 1-10]
The same as Example 1 except that any one or more of the types of base materials, the types and blending amounts of the components of the ink receiving layer composition, and the ink receiving layer formation amount are as shown in Table 4. An ink jet recording sheet was produced by this method.
In addition, description of "-" in the column of the compounding component in Table 4 means that the component is not compounded.

<< Evaluation of inkjet recording sheet >>
The following items were evaluated for the inkjet recording sheet obtained above. The results are shown in Table 5.

[Dot bleeding]
Dot bleeding was evaluated by the dot shape factor. The evaluation sample was printed on the ink-receiving layer of the inkjet recording sheet using a desktop inkjet printer (water color black pigment ink having a size of 2 cm × 2 cm at a concentration of 10% so that the dots do not overlap (single color printing). Produced. Next, a microscopic image of the surface of the inkjet recording sheet was taken and analyzed using a dot analyzer ("DA6000" manufactured by Oji Scientific Instruments). Specifically, the perimeter and area of the dots were measured, and the dot shape factor was calculated using the following formula.
Dot shape factor = (perimeter length) ² / (4π × area)

  The dot shape factor is 1 when the dot is a perfect circle, and increases as the dot shape moves away from the perfect circle, that is, the dot is blurred. It should be noted that the dot shape factor measured with a desktop ink jet printer (printing speed 250f (76.2m) / min) is sufficiently correlated with the dot shape factor measured with a high speed ink jet printer (printing speed 500f (152.4m) / min). Confirmed in advance that there is.

By using the above method, the dot shape coefficient was calculated for about 30 dots to obtain an average value, and dot bleeding was evaluated according to the following evaluation criteria. The results are shown in Table 5. The numerical value in parentheses in the “dot bleeding” column in Table 5 is the average value of the dot shape coefficients.
(Evaluation criteria)
A: The average value of the dot shape factor is 1.8 or less, and dot bleeding is completely or highly suppressed.
B: The average value of the dot shape factor is more than 1.8 and 2.0 or less, and dot bleeding is suppressed.
C: The average value of the dot shape factor exceeds 2.0, and dot bleeding is not suppressed.

[Ink dryness]
Using an ink jet printer, printing was performed with four colors of ink of cyan, magenta, yellow and black on the ink receiving layer of the ink jet recording sheet. More specifically, the printing was performed by changing the printing density for each color from 100% to 400% in units of 10%.
Next, immediately after the printing was completed, a transparent polyethylene terephthalate film (thickness: 100 μm) was superimposed on the printing surface of the inkjet recording sheet and firmly pressed to adhere.
Next, with this film kept in close contact with the print surface, the maximum print density of ink not transferred from the print surface to the close contact surface is confirmed by visual observation from the side opposite to the close contact surface to the print surface. Then, the drying property of the ink was evaluated according to the following evaluation criteria. The results are shown in Table 5. In Table 5, the numerical value in parentheses in the “ink drying property” column is the maximum printing density. In this evaluation method, it was confirmed in advance that the evaluation results would not vary as long as the film was in close contact with the printing surface.
(Evaluation criteria)
A: The maximum printing density of the ink is 300% or more, the drying property is excellent, and the high-speed printing suitability is achieved.
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 high-speed printability.
C: The maximum printing density of the ink is less than 190%, the drying property is inferior, and the high-speed printability is not achieved.

[Water resistance of ink receiving layer]
Using the same desktop inkjet printer as that used in the above-described dot bleeding evaluation, printing was performed on the entire surface of the ink receiving layer of the inkjet recording sheet with a black ink at a density of 100% (solid printing). The ink after printing was completely dried.
Next, the ink jet recording sheet after printing was immersed in a sufficient amount of tap water for 1 minute, and the ink receiving layer was rubbed with a finger strongly in tap water. Next, the state of the ink receiving layer was visually observed, and the water resistance of the ink receiving layer was evaluated according to the following evaluation criteria from the viewpoint of whether the ink receiving layer was broken or peeled, and if there was breakage or peeling. The results are shown in Table 5. In addition, as described above, the reason for printing with the black ink on the ink jet recording sheet is to make it clearly visible whether the ink receiving layer is broken or peeled off.
In this specification, in order to distinguish “water resistance of the ink receiving layer” in this item from “water resistance of the ink receiving layer at the time of wet opening” described later, “ink at the time of non-wetting opening” is used. It may be referred to as “water resistance of the receiving layer”.
(Evaluation criteria)
A: The ink receiving layer is not broken or peeled off, and the ink receiving layer is excellent in water resistance.
B: Although the ink receiving layer is slightly broken or peeled off, there is no problem in practical use, and the ink receiving layer has good water resistance.
C: Breakage or peeling of the ink receiving layer is clearly recognized, causing a problem in practical use, and the ink receiving layer is inferior in water resistance.

[Water resistance of ink receiving layer when wet opened]
Of the surface of the ink receiving layer of the ink jet recording sheet, the same desktop ink jet printer as that used in the above-described dot bleeding evaluation is formed on one surface that becomes a superimposed surface when the ink jet recording sheet is folded. Was used to print with a black ink at a density of 100% (solid printing). The ink after printing was completely dried.
Next, of the surface of the ink receiving layer in the inkjet recording sheet after printing, the overlapping surfaces can be bonded to the region that becomes the overlapping surface when the inkjet recording sheet is folded. An aqueous pseudo-pressure-sensitive adhesive for forming a pressure-sensitive adhesive layer was applied. This water-based pseudo-pressure-sensitive adhesive contains natural rubber / acrylic copolymer, acrylic copolymer, silica and starch as the main components. The application amount of the water-based pseudo pressure-sensitive adhesive was such that the amount of the pressure-sensitive adhesive layer formed was 3 to 5 g / m ² . One hour after coating, the ink jet recording sheet was folded and pressure-bonded under the condition that the peel strength after pressure bonding was 2N / 6 inch (15.24 cm), and the pressure-bonding treatment was performed on the coated surface. The ink jet recording sheet immediately after press bonding was immersed in a sufficient amount of tap water for 2 hours, then pulled up from the tap water, removed excessive moisture using a dry towel, and immediately opened (re-peeled). Next, the state of the ink receiving layer of the ink jet recording sheet after opening is visually observed. From the viewpoint of whether or not the ink receiving layer is broken and peeled, and if there is breakage or peeling, the following evaluation criteria are used. The water resistance of the ink receiving layer during wet opening was evaluated. At the time of this evaluation, since the overlapping surface of the ink receiving layer is bonded via the pressure-sensitive adhesive layer, if the ink receiving layer breaks or peels off on the re-peeled overlapping surface, the overlapping surface The transfer of the ink receiving layer from one surface of the ink to the other surface may be observed. The results are shown in Table 5. In addition, as described above, the reason for printing with the black ink on the ink jet recording sheet is to make it clearly visible whether the ink receiving layer is broken or peeled off.
(Evaluation criteria)
A: The ink receiving layer is not broken or peeled off, and the ink receiving layer is excellent in water resistance.
B: Although the ink receiving layer is slightly broken or peeled off, there is no problem in practical use, and the ink receiving layer has good water resistance.
C: Breakage or peeling of the ink receiving layer is clearly recognized, causing a problem in practical use, and the ink receiving layer is inferior in water resistance.

[Water resistance of substrate when wet opened]
At the same time as the evaluation of the “water resistance of the ink receiving layer at the time of wet-opening”, at the same time, the state of the base material at the time of wet-opening is visually observed to determine whether the base material is torn or not. From the viewpoint, the water resistance of the base material during wet opening was evaluated according to the following evaluation criteria. The results are shown in Table 5.
(Evaluation criteria)
A: The base material is not torn and the base material is excellent in water resistance.
B: Some tearing of the substrate is observed, but there is no problem in actual use, and the substrate has good water resistance.
C: Breaking of the substrate is clearly recognized, causing problems in practical use, and the substrate is inferior in water resistance.

As is apparent from the above results, the ink jet recording sheets of Examples 1 to 7 have good dot bleeding suppression effects and good ink drying properties, and have good characteristics as ink jet recording sheets. All of these ink jet recording sheets had good water resistance of the ink receiving layer at the time of non-wetting opening and at the time of wetting opening.
The ink jet recording sheet of Example 7 had insufficient water resistance of the base material at the time of wet opening, and the base material was torn, and the water resistance of the ink receiving layer at the time of wet opening could not be evaluated. Since the water resistance of the ink receiving layer at the time of non-wetting opening is good, it is considered that the water resistance of the ink receiving layer at the time of wet opening is good if a similar evaluation is performed using a water-resistant substrate. .

On the other hand, the recording sheet for ink jet of Comparative Example 1 has too little blending amount of the cationic styrene resin as the binder, and the cation with respect to the total content of components other than the first and second aggregated light calcium carbonates. The proportion of the content of the reactive styrenic resin was too small, and the water resistance of the ink receiving layer at the time of non-wet opening and at the time of wet opening was insufficient.
In the inkjet recording sheet of Comparative Example 2, dot bleeding was not suppressed because the amount of the cationic styrene resin as the binder was too large.
The ink jet recording sheet of Comparative Example 3 was insufficient in water resistance of the ink receiving layer at the time of non-wetting opening because an anionic styrene / acrylic resin was used as a binder.
The ink-jet recording sheet of Comparative Example 4 had insufficient ink drying properties due to the use of an anionic styrene / acrylic resin containing latex as a binder.

In the ink jet recording sheet of Comparative Example 5, due to the use of polyvinyl alcohol as the binder, the water resistance of the ink receiving layer at the time of non-wetting opening and at the time of wetting opening was insufficient. Furthermore, the water resistance of the base material at the time of wet opening was insufficient due to the use of the non-water resistant base material.
The inkjet recording sheet of Comparative Example 6 was obtained by using polyvinyl alcohol as a binder, and by using a cationic resin fixing agent and a polyvalent metal salt, components other than the first and second aggregated light calcium carbonates. Since the ratio of the content of the cationic styrene resin to the total content was too low, the water resistance of the ink receiving layer at the time of non-wet opening and wet opening was insufficient.
The ink jet recording sheet of Comparative Example 7 was insufficient in water resistance of the ink receiving layer at the time of wetting and opening due to the use of a cationic acrylic resin as a binder.
Unlike the case of Comparative Example 7, the ink jet recording sheet of Comparative Example 8 used a cationic acrylic resin as a binder and increased its blending amount (content). Although the ink property was improved, the drying property of the ink was insufficient.

  Inkjet recording sheets of Comparative Examples 9 and 10 use polyvinyl alcohol as a binder and use a cationic resin fixing agent, so that the total content of components other than the first and second aggregated light calcium carbonates The ratio of the content of the cationic styrene resin relative to the ink was too low, so that the water resistance of the ink receiving layer at the time of wet opening was insufficient.

  The present invention can be used as an inkjet recording sheet excellent in inkjet printability.

  1, 2 ... Inkjet recording sheet, 11 ... substrate, 11a ... first surface of substrate, 11b ... second surface of substrate, 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 (2)

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, as a pigment, first and second aggregated light calcium carbonates having different average secondary particle sizes,
The ink receiving layer contains a cationic styrene resin as a binder,
In the ink receiving layer, the ratio of the content of the cationic styrene resin to the total content of the first and second aggregated light calcium carbonates is 6.5 to 25% by mass,
In the ink receiving layer, the ratio of the content of the cationic styrenic resin to the total content of components other than the first and second aggregated light calcium carbonates is 65% by mass or more. . The average secondary particle diameter of the first aggregated light calcium carbonate is less than 1 μm, and the average secondary particle diameter of the second aggregated light calcium carbonate is 2 to 5 μm,
In the ink receiving layer, a ratio of [content (mass) of first aggregated light calcium carbonate]: [content (mass) of second aggregated light calcium carbonate] is 22:78 to 78:22. The inkjet recording sheet according to claim 1.

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