JP6759030B2 - Recording sheet - Google Patents

Description

The present invention relates to a recording sheet.

The information recording method using inkjet ink is rapidly becoming widespread because it is possible to easily obtain a full-color high-quality image and to realize a high-quality image close to that of silver halide photography due to recent technological advances.
The inks include water-based inks containing various coloring materials in a solvent such as water or a mixed solvent of water and a hydrophilic organic solvent, and oil-based inks containing an oil-soluble coloring material in a hydrophobic organic solvent. Ink can be mentioned and used properly according to the purpose.

On the other hand, in a recording sheet for an inkjet, an ink receiving layer for absorbing ink to form an image is formed on a base material such as paper. The ink receiving layer is required to have good ink drying properties. Then, the ink receiving layer can be formed by applying and drying a composition containing components necessary for fixing ink and a dispersion medium for dispersing them.

It is desired that such a recording sheet have a suitable surface state according to the level of information to be recorded and the like. Then, there is smoothness as one index for judging the surface state of the recording sheet. For example, a recording sheet in which the smoothness of the surface of the ink receiving layer is within a specific range has a matte coat-like appearance and is highly useful.
On the other hand, a recording sheet that can be used in various printing methods and has improved ink acceptability and surface smoothness is disclosed (see Patent Document 1).

Japanese Unexamined Patent Publication No. 2000-71606

However, the recording sheet disclosed in Patent Document 1 has a problem that the smoothness of the surface is limited to 100 to 200 seconds, which is insufficient to obtain a matte coat tone.
Therefore, it is an object of the present invention to provide a recording sheet having good ink drying property and a matte coat-like surface even when color printing is performed with a high-speed inkjet printer.

The present invention is a recording sheet including a base material and an ink receiving layer formed on at least one surface of the base material, and the ink receiving layer contains a pigment, a binder and a cationic resin. the ink-receiving layer, as the pigment, the first aggregated precipitated calcium carbonate average secondary particle diameter of less than 1 [mu] m, an average secondary particle diameter and a second aggregation precipitated calcium carbonate is 2 to 5 [mu] m, containing the ink-receiving layer, as the binder, polymerization degree containing a polyvinyl alcohol 1250-2000, in the ink-receiving layer, the total content of the binder, the proportion of the content of the polyvinyl alcohol , 95% by mass or more, and in the ink receiving layer, the ratio of [content of the first aggregated light calcium carbonate (mass)]: [content of the second aggregated light calcium carbonate (mass)] is It is 10:90 to 40:60, and the smoothness of the surface of the ink receiving layer opposite to the substrate side is 400 to 1900 seconds measured in accordance with JIS P 8155: 2010. , Provide a recording sheet.

In the recording sheet of the present invention, the 75 ° mirror gloss measured in accordance with JIS P 8142: 2005 is 17 to 30% on the surface of the ink receiving layer opposite to the base material side. Is preferable.

According to the present invention, there is provided a recording sheet having good ink drying property and a matte coat-like surface even when color printing is performed with a high-speed inkjet printer.

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

<< Recording sheet >>
The recording sheet of the present invention is a recording sheet including a base material and an ink receiving layer formed on at least one surface of the base material, and the ink receiving layer is an average secondary pigment. The ink receiving layer contains polyvinyl alcohol as a binder, containing a first aggregated light calcium carbonate having a particle size of less than 1 μm and a second aggregated light calcium carbonate having an average secondary particle size of 2 to 5 μm. The smoothness of the surface of the ink receiving layer opposite to the base material side measured in accordance with JIS P 8155: 2010 is 400 to 1900 seconds.

The recording sheet of the present invention is high-speed because the ink receiving layer has the above-mentioned limited composition, and in particular, it contains the first aggregated light calcium carbonate and the second aggregated light calcium carbonate as pigments. Even when color printing is performed with an inkjet printer, the ink has high dryness. Further, by performing the smoothing treatment in the manufacturing method described later, the smoothness of the ink receiving layer becomes the above-mentioned specific range, and the surface of the recording sheet becomes a desirable matte coat tone.

The ink receiving layer can be formed by applying a composition for an ink receiving layer containing a component for constituting the ink receiving layer onto a base material and drying the composition.
The ratio of the contents of the components that do not vaporize at room temperature in the composition for the ink receiving layer is usually the same as the ratio of the contents of the components of the ink receiving layer. In addition, in this specification, "normal temperature" means a temperature which is not particularly cooled or heated, that is, a normal temperature, and examples thereof include a temperature of 15 to 25 ° C.

The recording sheet of the present invention is suitable as, for example, a recording sheet for an inkjet, and can also be used as a recording sheet for a liquid toner, and has high versatility.
Hereinafter, the recording sheet of the present invention will be described mainly by taking an inkjet recording sheet as an example.

<Composition for ink receiving layer>
The composition for an ink receiving layer (hereinafter, may be simply abbreviated as "composition") contains, for example, the pigment, a binder, and, if necessary, other components that do not fall under any of these. Things can be mentioned.
Hereinafter, each component will be described.

[Pigment]
The pigment is a component that retains the pigment in the ink in the ink receiving layer and affects the absorption and permeation of water.
The composition for the ink receiving layer and the ink receiving layer contain, as the pigment, a first aggregated light calcium carbonate having an average secondary particle size of less than 1 μm and a second aggregate having an average secondary particle size of 2 to 5 μm. Contains light calcium carbonate.

Calcium carbonate includes heavy calcium carbonate and light calcium carbonate.
Heavy calcium carbonate is a crushed classification of natural limestone.
Light calcium carbonate is chemically synthesized, and the shape and size of its particles can be chemically controlled. The shape of the particles of light calcium carbonate is usually cubic, spindle-shaped, pillar-shaped, or the like. Light calcium carbonate includes those in which primary particles exist as simple substances and those in which primary particles aggregate to form secondary particles.
Light calcium carbonate in which primary particles aggregate to form secondary particles is called aggregated light calcium carbonate. The average particle size of the primary particles (average primary particle size) can be obtained from, for example, observation results with a scanning electron microscope. The average particle size of the secondary particles is determined by, for example, measurement by a laser diffraction method.
In the present invention, as the pigment, first aggregated light calcium carbonate and second aggregated light calcium carbonate having at least average secondary particle diameters different from each other are used.

The average secondary particle size of the first aggregated light calcium carbonate is less than 1 μm, preferably 0.9 μm or less, and is, for example, 0.8 μm or less, 0.7 μm or less, or 0.6 μm or less. It can be done, but these are just examples.
On the other hand, the lower limit of the average secondary particle size of the first aggregated light calcium carbonate is not particularly limited, but can be, for example, 0.2 μm. Since the ink receiving layer contains the first aggregated light calcium carbonate, the effect of suppressing dot bleeding when the recording sheet is inkjet printed is enhanced.

The average secondary particle size of the second aggregated light calcium carbonate is 2 to 5 μm, preferably 2.3 to 4.7 μm, and can be, for example, 2.6 to 4.4 μm. Is an example.
Since the ink receiving layer contains the second aggregated light calcium carbonate, the dryness of the ink when inkjet printing is performed on the recording sheet is improved. Here, "highly dry ink" means "short time required for drying ink".

The ink receiving layer may contain, as the first aggregated light calcium carbonate and the second aggregated light calcium carbonate, any of the above-mentioned average secondary particle diameters in an appropriate combination.
As described above, since the ink receiving layer contains both the first aggregated light calcium carbonate and the second aggregated light calcium carbonate, the recording sheet can be printed by color printing with a high-speed inkjet printer. Good drying property.

In the composition for the ink receiving layer 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, and more preferably 10:90 to 80:20. In terms of improving the effect of suppressing dot bleeding, it is preferable that the content of the first aggregated light calcium carbonate is high, and in terms of improving the drying property of the ink, the content of the second aggregated light calcium carbonate is high. Is preferable. Then, the ratio of [content of first aggregated light calcium carbonate (mass)]: [content of second aggregated light calcium carbonate (mass)] is, for example, 10:90 to 40:60. In the recording sheet, both the improvement of the effect of suppressing dot bleeding and the improvement of the drying property can be further achieved in a well-balanced manner, and the recording sheet can dry the ink even when color printing is performed by a high-speed inkjet printer. The sex becomes better.

The composition for the 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. It may contain a pigment.
Examples of the other pigment include aggregated light calcium carbonate other than the first and second aggregated light calcium carbonate; non-aggregated light calcium carbonate (that is, the primary particles are not aggregated to form secondary particles). (Light calcium carbonate); Calcium carbonate other than the first and second aggregated light calcium carbonates such as the heavy calcium carbonate can be mentioned.
Examples of the aggregated light calcium carbonate other than the first and second aggregated light calcium carbonates include aggregated light calcium carbonate having an average secondary particle size of 1 μm or more and less than 2 μm, and aggregated light carbonic acid having an average secondary particle size of more than 5 μm. Calcium and the like can be mentioned.

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

In the composition for the ink receiving layer and the ink receiving layer, the ratio of the total content of the first and second aggregated light calcium carbonate to the total content of the pigment is preferably 92% by mass or more, preferably 94% by mass. The above is more preferable, 96% by mass or more is further preferable, 98% by mass or more is particularly preferable, and 100% by mass may be used.

The ratio of the pigment content (that is, the pigment content of the ink receiving layer) to the total content of the components other than the solvent described later in the composition for the ink receiving layer is preferably 70 to 95% by mass. It is more preferably 75 to 92% by mass, and particularly preferably 80 to 90% by mass. When the ratio is at least the lower limit value, the effect of using the pigment can be obtained more remarkably. Further, when the ratio is not more than the upper limit value, the strength of the ink receiving layer becomes higher.
In the present specification, the term "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. It means the content (ie, the total content of the pigment).

[binder]
The binder is a component for retaining the pigment (first and second aggregated light calcium carbonate, etc.) contained therein in the ink receiving layer.
The composition for the ink receiving layer and the ink receiving layer contain polyvinyl alcohol as the binder.
Polyvinyl alcohol is a component that affects the dryness and dot bleeding of ink in the ink receiving layer and the strength of the ink receiving layer.

Examples of polyvinyl alcohol include fully saponified polyvinyl alcohol and partially saponified polyvinyl alcohol.

The degree of saponification of polyvinyl alcohol is preferably 90 mol% or more, more preferably 93 mol% or more, and particularly preferably 96 mol% or more. When the degree of saponification of polyvinyl alcohol is at least the above lower limit value, the effect of suppressing dot bleeding in the ink receiving layer is further improved, and the strength of the ink receiving layer is further improved. The upper limit of the degree of saponification of polyvinyl alcohol is not particularly limited, and may be, for example, 99.5 mol% or 100 mol%.
The degree of saponification of polyvinyl alcohol is preferably within a range set by appropriately combining any of the above lower limit values and upper limit values.

The degree of polymerization of polyvinyl alcohol is preferably 500 to 2500, more preferably 750 to 2350, further preferably 1000 to 2200, and particularly preferably 1250 to 2000. When the degree of polymerization of polyvinyl alcohol is not more than the above upper limit value, the drying property of the ink is further improved. Further, when the degree of polymerization of polyvinyl alcohol is at least the above lower limit value, the strength of the ink receiving layer is further improved.

The composition for the ink receiving layer and the ink receiving layer may contain a binder other than the polyvinyl alcohol as long as the effect of the present invention is not impaired.
Examples of the other binder include water-soluble polymers other than the polyvinyl alcohol.

Examples of the water-soluble polymer include modified polyvinyl alcohols such as cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, and silanol-modified polyvinyl alcohol; oxidized starch; phosphoric acid esterified starch; locons; casein; carboxymethyl cellulose (CMC); ester. Examples thereof include polyurethanes such as polyurethanes and carbonate polyurethanes.
The polyurethane may be, for example, cationic, anionic or nonionic.

The polyvinyl alcohol and the other binders may be used alone or in combination of two or more, and when two or more of them are used in combination, the combination and ratio thereof are intended. It may be appropriately selected according to the above.

In the composition for the ink receiving layer and the ink receiving layer, the ratio of the content of the polyvinyl alcohol to the total content of the binder is preferably 60% by mass or more, more preferably 70% by mass or more. It is particularly preferably 80% by mass or more, and may be, for example, 85% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass.

In the composition for the ink receiving layer and the ink receiving layer, the ratio of the content of the binder to the content of the pigment is preferably 3 to 20% by mass, more preferably 4 to 15% by mass, and 5 It is particularly preferably ~ 13% by mass. When the ratio is not more than the lower limit value, the strength of the ink receiving layer becomes higher, and when the ratio is not more than the upper limit value, the drying property of the ink in the ink receiving layer becomes higher.
In addition, in this specification, "binder content" means the content of all binders used including not only polyvinyl alcohol but also other binders (that is, the total content of binders) unless otherwise specified. Content).

[Other ingredients]
Examples of the other components include a solvent, a cationic resin, a polyvalent metal salt, a pH adjuster, an antifoaming agent, a defoaming agent, a mold release agent, a foaming agent, an antioxidant, an antiseptic agent, a water resistant agent, and paper. Examples thereof include components usually used in the ink receiving layer of a recording sheet for inkjet, such as a force enhancer, a coloring dye, a coloring pigment, a dye fixing agent, a pigment dispersant, a fluorescent whitening agent, and an ultraviolet absorber.
As for the other components, one type may be used alone, two or more types may be used in combination, and when two or more types are used in combination, the combination and ratio thereof may be appropriately selected according to the purpose. Good.

(solvent)
In the composition for the ink receiving layer, the pigment, the binder, or the other component other than the solvent was blended as a dispersion or a solution, and no solvent was used other than that used as the dispersion medium or the solvent at that time. In this case, the solvent means the dispersion medium used to prepare the dispersion or the solvent used to prepare the solution.
When a solvent is separately blended in addition to the dispersion medium used for preparing the dispersion or the solvent used for adjusting the solution, the solvent is the dispersion medium or solvent and the solvent. Means both solvent and. When all of the other components other than the pigment, the binder, and the solvent are blended as a solid substance, the solvent means a solvent blended separately from these.
Examples of the solvent include water, alcohol and the like.

As the solvent, one type may be used alone, two or more types may be used in combination, and when two or more types are used in combination, the combination and ratio thereof may be appropriately selected according to the purpose.

The content of the solvent in the composition for the ink receiving layer may be appropriately selected depending on the intended purpose, and is not particularly limited, but is preferably 20 to 90% by mass, for example.

(Cation resin)
The cationic resin is suitable as an ink fixing agent in the ink receiving layer, and preferably dissociates when dissolved in water to exhibit cationic properties.
Among them, the cationic resin is preferably a monomer, oligomer or polymer of a primary amine, a secondary amine, a tertiary amine or a quaternary ammonium salt, and more preferably the oligomer or polymer.

More preferred cationic resins are, for example, alkylamine-epichlorohydrin copolymers; acrylic polymers having a secondary amino group, a tertiary amino group or a quaternary ammonium group; polyvinylamine; polyvinylamidine; 5 members. Ring amidines; dicyan cation resins such as dicyandiamide-formalin copolymers; polyamine cation resins such as dicyandiamide-polyethyleneamine copolymers; polyalkylene polyamines such as polyethylene polyamines and polypropylene polyamines and derivatives thereof; diallyldimethylammonium- SO ₂ copolymer; diallylamine salt -SO ₂ copolymer; dimethyldiallylammonium chloride polymer; homopolymers or copolymers of vinyl benzyl triallyl ammonium salt; dialkyl aminoethyl (meth) acrylate polymer of allylamine salt A quaternary salt copolymer; an acrylamide-diallylamine salt copolymer; an aluminum salt such as polyaluminum chloride or polyaluminum acetate, and an alkylamine-epichlorohydrin polycondensate is particularly preferable, and a dimethylamine-epichlorohydrin polycondensate is particularly preferable. Most preferably, it is a thing.

Unless otherwise specified, the terms "derivative" and "class" in the present specification refer to a compound in which one or more hydrogen atoms of the original compound are replaced with a group (atom) other than a hydrogen atom. means.

As the cationic resin, one type may be used alone, two or more types may be used in combination, and when two or more types are used in combination, the combination and ratio thereof may be appropriately selected depending on the intended purpose.

In the composition for the ink receiving layer and the ink receiving layer, the ratio of the content of the cationic resin to the content of the pigment is preferably 1 to 40% by mass, more preferably 1 to 25% by mass. 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.

(Multivalent metal salt)
The polyvalent metal salt is a component that improves 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 as a constituent component.

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 ), and calcium sulfate (CaSO ₄ ). , Magnesium Sulfate (sulfonyl ₄ ), Calcium Nitrate (Ca (NO ₃ ) ₂ ), Magnesium Acetate ((CH ₃ COO) ₂ Mg), Calcium Acetate ((CH ₃ COO) ₂ Ca), Potassium Aluminum Sulfate (Karimyoban, AlK (SO ₄ ) ₂ ) and the like can be mentioned.
The polyvalent metal salt may be a hydrate or a non-hydrate.

Among them, the polyvalent metal salt can improve the drying property and color density of the ink in the ink receiving layer, and the water resistance and scratch resistance of the ink receiving layer in a well-balanced manner, and has high safety. In that respect, calcium chloride, magnesium chloride or potassium aluminum sulfate is preferable, and potassium aluminum sulfate is particularly preferable in that the drying property of the ink is further improved.

One type of polyvalent metal salt may be used alone, or two or more types may be used in combination. When two or more types are used in combination, the combination and ratio thereof may be appropriately selected according to the purpose. Good.

The composition for the ink receiving layer and the ink receiving layer preferably contain one or more selected from the group consisting of calcium chloride, magnesium chloride and potassium aluminum sulfate, more preferably those containing potassium aluminum sulfate, and sulfuric acid. When it contains potassium aluminum, it is more preferable to contain one or both of calcium chloride and magnesium chloride. When the ink receiving layer contains at least potassium aluminum sulfate, the drying property of the ink is further improved.

In the composition for the ink receiving layer and the ink receiving layer, the ratio of the content of the polyvalent metal salt to the content of the pigment is preferably 3 to 55% by mass, more preferably 3 to 25% by mass. It is preferably 3 to 15% by mass, more preferably 3 to 10% by mass, and particularly preferably 3 to 10% by mass. When the ratio is at least the lower limit value, the effect of using the polyvalent metal salt can be obtained more remarkably. Further, when the ratio is not more than the upper limit value, excessive use of the polyvalent metal salt is suppressed.

(Defoamer)
The defoaming agent is not particularly limited and may be a known one.
As the defoaming agent, one type may be used alone, two or more types may be used in combination, and when two or more types are used in combination, the combination and ratio thereof may be appropriately selected according to the purpose. ..

The total content of the other components in the composition for the ink receiving layer may be appropriately adjusted according to the intended purpose.

<Manufacturing method of composition for ink receiving layer>
The composition for the ink receiving layer can be produced by blending the pigment, the binder, and other components if necessary, and sufficiently stirring these blending components. In the composition for the ink receiving layer, it is preferable that both the pigment and the binder are dispersed.

When a solvent, a polyvalent metal salt and a cationic resin are used as the other components, as an example of a method for blending each component, the polyvalent metal salt, the cationic resin, the binder and the pigment are added to the solvent in this order and mixed. The method of doing this can be mentioned. The order of addition of the pigments is not particularly limited, and for example, the second aggregated light calcium carbonate and then the first aggregated light calcium carbonate can be added in this order, but the first aggregated light calcium carbonate and then the second aggregated light calcium carbonate can be added. Light calcium carbonate may be added in this order. In this method, when two or more kinds of each component, particularly the other component, are used in combination, these two or more kinds of components may be added at the same time, may be added separately, or may be added separately. The order of addition and the timing of addition can be appropriately adjusted according to the type of the component. As described above, the solvent may be used by being mixed in advance with the pigment, the binder, or the other component other than the solvent, or may be used alone without being mixed in advance with these components. Good.

The temperature at the time of blending each component is not particularly limited and may be appropriately adjusted according to the type of the blended component and the like, but 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. The stirring time may be appropriately adjusted according to the total amount of the composition for the ink receiving layer to be produced, the stirring method, and the like, and is preferably 10 minutes to 24 hours, for example.

The recording sheet of the present invention can be produced by applying the composition for an ink receiving layer on a substrate and drying it to form an ink receiving layer, and further, after forming the ink receiving layer, at least ink receiving. It can be easily manufactured by smoothing the surface of the layer.
By such a manufacturing method, the surface of the ink receiving layer on the side opposite to the base material side has a smoothness measured according to JIS P 8155: 2010, which is easily 400 to 1900 seconds.

The smoothing process of the recording sheet (the surface of the ink receiving layer) is performed using a known calendar device such as a machine calendar, a TG calendar, a super calendar, a soft calendar, a gloss calendar, a compact calendar, a mat super calendar, or a mat calendar. It can be carried out.

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

The conditions for the smoothing treatment are appropriately selected according to the required quality, such as the temperature of the rigid roll, the calendar pressure, the number of nip, the roll speed, and the moisture content of the paper before the smoothing treatment.

Since the recording sheet whose surface is smoothed after the ink receiving layer is formed on the base material is compressed in the thickness direction, the base material and the ink receiving layer are more clogged and the air permeability is lowered. However (for example, the value of air permeability becomes large), and normally, the ink does not pass well and the dryness tends to decrease. However, in the recording sheet of the present invention, even if the surface is smoothed, the ink receiving layer has the above-mentioned limited composition, so that the decrease in the dryness of the ink is suppressed.
Further, in the recording sheet of the present invention, the smoothness of the ink receiving layer is within the above-mentioned specific range by the smoothing treatment, and the surface of the recording sheet has a desirable matte coat tone.
Next, each layer constituting the recording sheet of the present invention will be described in detail.

<Base material>
The material of the base material is not particularly limited, and it may be selected from those capable of forming a coating layer according to the purpose.
Specific examples of the material of the base material include papers such as high-quality paper, art paper, coated paper, cast-coated paper, resin-coated paper, and synthetic paper; polyethylene, polypropylene, polyvinyl chloride, polystyrene, and polyvinyl acetate. , Acrylic resin, AS resin, ABS resin, polyamide, polyacetal, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyphenylensulfide, polysulfone, polycarbonate, epoxy resin, melamine resin, phenol Examples thereof include resins, urea resins, synthetic resins such as polyurethane and polyethylene.

The thickness of the base material is not particularly limited as long as the shape of the base material is in the form of a sheet or a film, but is preferably 20 to 1000 μm, more preferably 35 to 500 μm, and 50 to 200 μm. Is particularly preferable. When the thickness of the base material is at least the above lower limit value, the structure of the ink receiving layer can be held more stably, and when the thickness of the base material is at least the above upper limit value, the handleability as a recording sheet is improved. It will be better.

The base material may be composed of a single layer, may be composed of a plurality of layers of two or more layers, and when composed of a plurality of layers, the plurality of layers may be the same as 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. When the plurality of layers are different from each other, the combination of the plurality of layers is not particularly limited. Here, when a plurality of layers are different from each other, it means that at least one of the material and the thickness of each layer is different from each other.
When the base material is composed of a plurality of layers, the total thickness of each layer may be set to the above-mentioned preferable thickness of the base material.

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

<Ink receiving layer>
The ink receiving layer can be formed by using the composition for the ink receiving layer as described above.
The coating of the composition for the ink receiving layer on the substrate may be performed once or may be performed in a plurality of times. When the coating is performed in a plurality of times, the method of further coating the composition for the ink receiving layer on the dried coating layer and the method of further applying the ink receiving on the undried coating layer. It may be any method of coating the layer composition.
The coating amount of the composition for the ink receiving layer may be appropriately adjusted in consideration of the solid content concentration of the composition for the ink receiving layer, the thickness of the ink receiving layer, and the like.

The coated composition for the ink receiving layer may be dried by a known method such as blast drying and heating blast 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 ¹ to 30 g / m ² , and more preferably ² to ²⁰ g / m ² .

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

FIG. 1 is a cross-sectional view schematically showing an embodiment of a recording sheet of the present invention. Further, FIG. 2 is a cross-sectional view schematically showing another embodiment of the recording sheet of the present invention.
In addition, in FIG. 2, the same components as those shown in FIG. 1 are designated by the same reference numerals as in the case of FIG.
Further, in the drawings used in the following description, in order to make the features of the present invention easy to understand, the main parts may be enlarged for convenience, and the dimensional ratios and the like of each component are the same as the actual ones. Is not always the case.

The recording sheet 1 shown in FIG. 1 is provided with the ink receiving layer 12 only on one surface 11a of the base material 11.
Further, the recording sheet 2 shown in FIG. 2 is provided with an ink receiving layer 12 on one surface 11a and the other surface 11b of the base material 11. Regarding the two ink receiving layers 12 and 12 in the recording sheet 2, those provided on one surface 11a of the base material 11 are shown as the first ink receiving layer 121 as needed, and the base material 11 Those provided on the other surface 11b are shown as the second ink receiving layer 122 to distinguish them from each other.

In FIG. 1, reference numeral 12a indicates the surface of the ink receiving layer 12 opposite to the base material 11 side, and reference numeral 12b indicates the surface of the ink receiving layer 12 on the base material 11 side.
Further, in FIG. 2, reference numerals 12a, 121a, and 122a indicate the surfaces of the ink receiving layer 12, the first ink receiving layer 121, and the second ink receiving layer 122, respectively, opposite to the base material 11 side, and reference numeral 12b. , 121b and 122b indicate the surfaces of the ink receiving layer 12, the first ink receiving layer 121 and the second ink receiving layer 122 on the base material 11 side, respectively.

In FIGS. 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 those described above, respectively.

However, the recording sheets shown in FIGS. 1 and 2 are merely examples of the recording sheets of the present invention, and the recording sheets of the present invention are not limited thereto.

In the recording sheet of the present invention, the ink receiving layer may be provided on the entire surface of the surface to be formed on the base material, or may be provided only in a part of the region.
When the recording sheet of the present invention is viewed in a plan view from above the side where 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 base material, and this condition is satisfied. As long as it is satisfied, it is not particularly limited. The shapes of the ink receiving layer and the base material when viewed in a plane in this way can also be arbitrarily set according to the purpose and are not particularly limited.

The smoothness of the surface of the ink receiving layer opposite to the substrate side, measured in accordance with JIS P 8155: 2010, is 400 to 1900 seconds, preferably 450 to 1880 seconds, and is preferably 500. It is more preferably ~ 1860 seconds, and particularly preferably 550 to 1840 seconds. The smoothness can be easily adjusted, for example, by adjusting the above-mentioned smoothing treatment conditions.
Here, "the surface of the ink receiving layer opposite to the base material side" means "the surface 12a of the ink receiving layer 12" in the recording sheet 1 shown in FIG. 1, and is shown in FIG. In the recording sheet 2 shown, it means "the surface 12a of the ink receiving layer 12", "the surface 121a of the first ink receiving layer 121", and "the surface 122a of the second ink receiving layer 122".

The 75 ° mirror gloss measured according to JIS P 8142: 2005 for the surface of the ink receiving layer opposite to the substrate side is preferably 17 to 30%, preferably 18 to 28%. More preferably. The smoothness can be easily adjusted, for example, by adjusting the conditions of the above-mentioned smoothing treatment, or by adjusting the type or content of the components contained in the ink receiving layer.

As described above, the recording sheet of the present invention is suitable as a recording sheet for an inkjet, but is also suitable as a recording sheet for liquid toner. When the recording sheet of the present invention is used as a recording sheet for liquid toner, the ink receiving layer functions as a receiving layer for liquid toner.
Since the ink receiving layer of the recording sheet of the present invention is made of a material in a specific range as described above, it can be used for both inkjet and liquid toner in this way, and is excellent in versatility.

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

<Raw materials used>
In Examples and Comparative Examples shown below, a composition for an ink receiving layer was applied to a base material to produce a recording sheet for an inkjet.

In the production of the composition for the ink receiving layer, agglomerated light calcium carbonate (synthetic calcium carbonate which is agglomerated particles) having physical properties shown in Table 1 was used as a pigment. In Table 1, the average primary particle size was calculated as an average value by observing the pigment with a scanning electron microscope at a magnification of 30,000 and measuring the particle size of 20 primary particles. In Table 1, the average secondary particle size was measured by a laser diffraction method using MICROTRAC MT3000 (trade name, manufactured by Nikkiso Co., Ltd.). The measurement results were converted to the number standard.

As the binder, polyvinyl alcohol (“PVA117” manufactured by Kuraray Co., Ltd., saponification degree 98.0-99.0 mol%, polymerization degree 1700) was used.
As the cationic resin, an alkylamine-epichlorohydrin polycondensate (“Jetfix 260” manufactured by Satoda Kako Co., Ltd.) was used.
As the multivalent metal salt, calcium chloride and potassium aluminum sulfate (potassium alum) were used.
As the defoaming agent, SN Deformer 777 and SN Deformer 450 (both manufactured by San Nopco) were used.

<Manufacturing of recording sheet>
[Example 1]
4.290 parts by mass of calcium chloride and 2.778 parts by mass of a cationic resin (“Jetfix 260”) were added to water in this order, and the mixture was stirred at room temperature to obtain a dispersion liquid in which these components were dispersed.
On the other hand, 8.30 parts by mass (solid content) of polyvinyl alcohol (“PVA117”) was added to water, the temperature was raised to 95 ° C. with stirring, and 0.005 parts by mass of an antifoaming agent (“SN deformer 777”) was added. Then, the mixture was stirred at 95 ° C. for 60 minutes to obtain an aqueous polyvinyl alcohol solution.
Next, the polyvinyl alcohol aqueous solution obtained above was added to the dispersion obtained above, and the mixture was stirred at room temperature for 5 minutes, and then the pigment (B) (average secondary particle size 3.) was added to the obtained mixed solution. 75 parts by mass of 39 μm aggregated light calcium carbonate and 25 parts by mass of pigment (A) (aggregated light calcium carbonate having an average secondary particle size of 0.49 μm) were added in this order, and the mixture was stirred at room temperature for 60 minutes.
Next, a dispersion liquid in which 2.140 parts by mass of potassium aluminum sulfate was dispersed in water was added to the stirring liquid obtained above, and 0.100 parts by mass of an antifoaming agent (“SN deformer 450”) was further added. Dispersion was carried out by stirring sufficiently to produce a composition for an ink receiving layer.

Roll-shaped base material (foam paper, Nippon Paper Industries "NPi Foam <70>", thickness 102 ± 6 μm, width 1655 mm, basis weight 81.4 g / m ² ) is fed out, and an air knife coater is placed on both sides thereof. Using, the composition for an ink receiving layer obtained above was applied and dried at 150 ° C. to form an ink receiving layer having a thickness of 10 μm. At this time, the ink receiving layer is dried so that the water content of the ink receiving layer is 8% by mass or less by moving a drying furnace for heating and blowing on the base material to which the composition for the ink receiving layer has been applied. It was.

Next, a smoothing (calendar) treatment of the base material on which the ink receiving layer was formed was performed under the conditions of a roll temperature of 50 ° C. and a calendar pressure of 5 MPa using an actual super calendar device.
From the above, a recording sheet for an inkjet was manufactured.

[Examples 2 to 4, Comparative Examples 1 to 2]
A recording sheet for an inkjet in the same manner as in Example 1 except that one or both of the smoothing treatment conditions and the surface on which the composition for the receiving layer is applied to the roll are as shown in Table 2. Manufactured.

<Evaluation of recording sheet>
The following items were evaluated for the above-mentioned recording sheet for inkjet. The results are shown in Table 2.

[Smoothness]
The smoothness of the surface of the receiving layer opposite to the substrate side was measured according to JIS P 8155: 2010.

[Ink drying property]
Using an inkjet printer, printing was performed on the receiving layer of the recording sheet for inkjet with four color inks of cyan, magenta, yellow, and black. More specifically, the printing was performed by changing the printing density for each color from 100% to 400% in units of 10%.
Then, immediately after the completion of printing, a transparent polyethylene terephthalate film (thickness 100 μm) was superposed on the printed surface of the recording sheet for an inkjet and pressed firmly against each other to bring them into close contact with each other.
Next, while the film is in close contact with the printing surface, the maximum print density of the ink not transferred from the printing surface to the contact surface is confirmed by visually observing from the side opposite to the contact surface with the printing surface. Then, the dryness of the ink was evaluated according to the following evaluation criteria. The numerical value in parentheses in the column of "ink dryness" in Table 2 is the maximum print 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 printed surface.
(Evaluation criteria)
⊚: The maximum print density of the ink is 300% or more, the drying property is excellent, and the ink has high-speed printing suitability.
◯: 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 printing suitability.
X: The maximum print density of the ink is less than 190%, the drying property is inferior, and the ink does not have high-speed printing suitability.

[75 ° mirror gloss]
According to JIS P 8142: 2005, using a gloss meter (“Gloss Meter GM26D” manufactured by Murakami Color Technology Laboratory), the surface of the recording sheet for inkjet, that is, the surface of the ink receiving layer opposite to the substrate side. The 75 ° mirror surface gloss was measured.

[appearance]
The appearance of the recording sheet for an inkjet was evaluated from the viewpoint of whether or not the surface of the receiving layer had a desirable matte coat tone. More specifically, when the surface of the receiving layer had a desirable matte coat tone, it was evaluated as ◯, and when it was not, it was evaluated as ×.

As is clear from the above results, in the recording sheets for inkjet of Examples 1 to 4, the smoothness of the receiving layer was 590 to 1800 seconds, and the surface of the receiving layer had a desirable matte coat tone. In addition, the maximum print density of the non-transferred ink was 200 to 250%, and the ink had dryness suitable for color printing with a high-speed inkjet printer.

On the other hand, in the recording sheet for inkjet of Comparative Example 1, the smoothness of the receiving layer was low, the surface of the receiving layer was not a desirable matte coat tone, and the appearance was poor.
In addition, the inkjet recording sheet of Comparative Example 2 had a low maximum print density of the non-transferred ink, and did not have the dryness of the ink suitable for color printing with a high-speed inkjet printer.

The present invention can be used for an inkjet recording sheet applied to color printing with a high-speed inkjet printer. The present invention can also be used for a recording sheet for liquid toner.

1, 2, ... Recording sheet, 11 ... Base material, 11a ... One surface of the base material, 11b ... The other surface of the base material, 12 ... Ink receiving layer, 12a ... The surface of the ink receiving layer opposite to the base material side, 12b ... the surface of the ink receiving layer on the base material side, 121 ... the first ink receiving layer, 121a ... the base material of the first ink receiving layer. The surface opposite to the side, 121b ... the surface of the first ink receiving layer on the substrate side, 122 ... the second ink receiving layer, 122a ... opposite to the substrate side of the second ink receiving layer. Side surface, 122b ... Surface of the second ink receiving layer on the substrate side

Claims (2)

A 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 pigment, a binder and a cationic resin, and contains
The ink-receiving layer, as the pigment, the first aggregated precipitated calcium carbonate average secondary particle diameter of less than 1 [mu] m, and the second aggregated precipitated calcium carbonate average secondary particle diameter of 2 to 5 [mu] m, the Contains,
The ink-receiving layer, as the binder, polymerization degree containing a polyvinyl alcohol 1250-2000,
In the ink receiving layer, the ratio of the content of the polyvinyl alcohol to the total content of the binder is 95% by mass or more.
In the ink receiving layer, the ratio of [content (mass) of the first aggregated light calcium carbonate]: [content (mass) of the second aggregated light calcium carbonate] is 10:90 to 40:60. And
A recording sheet having a smoothness of 400 to 1900 seconds measured according to JIS P 8155: 2010 on the surface of the ink receiving layer opposite to the substrate side. For the surface opposite to the substrate side of the ink receiving layer, JIS P 8142: 75 ° specular gloss was measured according to 2005, is 17 to 30%, the recording of claim 1 Sheet.

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