JP6689111B2 - Recording sheet - Google Patents

Description

  The present invention relates to a recording sheet.

Information recording methods using ink jet inks are rapidly becoming widespread because full-color, high-quality images can be easily obtained and, due to technological advances in recent years, high-quality images approaching silver halide photography can be realized.
As the ink, water, a water-based ink containing various coloring materials in a solvent such as a mixed solvent of water and a hydrophilic organic solvent, and an oil-based ink containing an oil-soluble coloring material in a hydrophobic organic solvent Ink and the like are used, and are used properly according to the purpose.
On the other hand, an ink jet recording sheet has an ink receiving layer for absorbing an ink to form an image on a base material such as paper. Then, the ink receiving layer can be formed by applying and drying a composition containing components necessary for fixing the ink and the like and a dispersion medium for dispersing these components.

  In such a recording sheet, an easily adhesive treatment layer containing a pigment and a resin and an ink receiving layer are sequentially laminated on at least one surface of a substrate, and the resin has a specific degree of polymerization or saponification. And at least one selected from the group consisting of polyvinyl alcohol, styrene-butadiene copolymer, acrylic ester copolymer, and polyurethane resin, and the blending ratio of the pigment is from the easy adhesion treatment layer to the ink receiving layer. (See Patent Document 1), a white pigment layer (ink receiving layer) is provided on one side of a support, and the white pigment layer contains a cationic urethane resin emulsion (see Patent Document 2). ) Is disclosed.

JP, 2003-266925, A JP, 11-180030, A

  However, although the recording sheet disclosed in Patent Document 1 has high strength such as water resistance of the ink receiving layer, suppression of dot bleeding and poor drying is considered when used for inkjet printing in a high-speed printer. It wasn't something. Further, the recording sheet disclosed in Patent Document 2 is said to have high strength such as water resistance of the ink receiving layer and can suppress dot bleeding and poor drying, but it can be applied to ink jet printing in a high speed printer. Was not. Here, the high-speed printer means, for example, a printer that prints at a speed of 500 f (152.4 m) / minute or more.

Therefore, it is an object of the present invention to provide an inkjet recording sheet that does not cause dot bleeding, has good drying properties, and has excellent water resistance of the ink receiving layer even when inkjet printing is performed with a high-speed printer. .
Further, some inkjet recording sheets can be used as recording sheets suitable for printing with liquid toner (liquid toner recording sheets). Another object of the present invention is to provide such a recording sheet for liquid toner.

The present invention is a recording sheet comprising a substrate and an ink receiving layer formed on at least one surface of the substrate, wherein the receiving layer contains a pigment and a binder, and the receiving layer is As the binder, polyvinyl alcohol and polyurethane are contained, the saponification degree of the polyvinyl alcohol is 90 mol% or more, and the content of the binder in the receiving layer is 100 parts by mass of the pigment. 5 parts by mass or more Ri 20 parts by less than der, the pigment is Ru der aggregation precipitated calcium carbonate, to provide a recording sheet.
The recording sheet of the present invention preferably has an air permeability of 600 seconds or less and a gloss of 75 ° of 15 to 50%.
In the recording sheet of the present invention, the agglomerated light calcium carbonate is preferably composed of a first agglomerated light calcium carbonate and a second agglomerated light calcium carbonate having different average secondary particle diameters.
In the recording sheet of the present invention, the first aggregated light calcium carbonate has an average secondary particle diameter of less than 1 μm, and the second aggregated light calcium carbonate has an average secondary particle diameter of 2 μm to 5 μm. preferable.
In the recording sheet of the present invention, it is preferable that the mixing ratio of the first agglomerated light calcium carbonate and the second agglomerated light calcium carbonate is 10:90 to 90:10 in mass ratio.

According to the present invention, there is provided an inkjet recording sheet that does not cause dot bleeding, has good drying properties, and has excellent water resistance of the ink receiving layer even when inkjet printing is performed with a high-speed printer.
Further, according to the present invention, a recording sheet for liquid toner is provided.

<< Recording sheet >>
The recording sheet of the present invention is a recording sheet including a substrate and an ink receiving layer (hereinafter, may be simply referred to as “receiving layer”) formed on at least one surface of the substrate. The receiving layer contains a pigment and a binder, the receiving layer contains polyvinyl alcohol and polyurethane as the binder, the polyvinyl alcohol has a saponification degree of 90 mol% or more, the receiving layer, The content of the binder is 5 parts by mass or more and less than 20 parts by mass with respect to 100 parts by mass of the pigment content.
The ink receiving layer is formed by applying a composition for an ink receiving layer on a substrate.

The recording sheet of the present invention can be used as both an inkjet recording sheet and a liquid toner recording sheet, and has high versatility.
Hereinafter, the recording sheet of the present invention will be described mainly using an inkjet recording sheet as an example.

<Composition for ink receiving layer>
The composition for the ink receiving layer (hereinafter, sometimes simply abbreviated as “composition”) contains the pigment, the binder and, if necessary, other components.

(Pigment)
The pigment is a component that holds the pigment in the ink and affects the absorption and transmission of water.
The pigment is preferably calcium carbonate.
Heavy calcium carbonate and light calcium carbonate exist in calcium carbonate. Heavy calcium carbonate is obtained by crushing and classifying natural limestone, and light calcium carbonate is chemically synthesized. The shape and size of the particles of light calcium carbonate can be chemically controlled. The particles of light calcium carbonate have a cubic shape, a spindle shape, a pillar shape, or the like. Further, among the light calcium carbonates, there are those in which primary particles exist as simple particles and those in which primary particles are aggregated to form secondary particles.
Light calcium carbonate in which primary particles are aggregated to form secondary particles is referred to as aggregated light calcium carbonate. The average particle size of the primary particles (average primary particle size) can be obtained from, for example, the result of observation with a scanning electron microscope. The average particle diameter of the secondary particles can be determined by, for example, measuring by a laser diffraction method.
The pigments may be used alone or in combination of two or more, and in the case of using two or more in combination, the combination and ratio thereof may be appropriately selected according to the purpose.

The pigment is preferably agglomerated light calcium carbonate.
When agglomerated light calcium carbonate is used as the pigment, it is preferable to use first and second agglomerated light calcium carbonates having different average secondary particle diameters together.

  The average secondary particle diameter of the first aggregated light calcium carbonate is preferably less than 1 μm, and the average secondary particle diameter of the second aggregated light calcium carbonate is preferably 2 to 5 μm. The inclusion of agglomerated light calcium carbonate having an average secondary particle diameter of less than 1 μm tends to reduce dot bleeding when inkjet printing. In addition, the inclusion of agglomerated light calcium carbonate having an average secondary particle diameter of 2 to 5 μm tends to enhance the drying property of the ink when inkjet printing. Here, the high drying property of the ink means that the time required for drying the ink is short.

Of the blending amount of the first aggregated light calcium carbonate (for example, having an average secondary particle size of less than 1 μm) and the second aggregated light calcium carbonate (for example, having an average secondary particle size of 2 to 5 μm) The ratio is not particularly limited, but is preferably 10:90 to 90:10, and more preferably 10:90 to 80:20. From the viewpoint of reducing dot bleeding, it is preferable that the amount of agglomerated light calcium carbonate having an average secondary particle diameter of less than 1 μm is high, and from the viewpoint of improving the drying property of the ink, the average secondary particle diameter is 2 to 5 μm. It is preferable that the amount of the agglomerated light calcium carbonate is high. When the ratio of the blending amounts of the first aggregated light calcium carbonate and the second aggregated light calcium carbonate is, for example, 10:90 to 40:60, both suppression of dot bleeding and improvement of drying property are achieved. It can be achieved in a more balanced manner.
In the ink receiving layer, the content ratio of the components having neither volatility nor sublimability at room temperature is usually the same as the content ratio of these components in the ink receiving layer composition. Therefore, in the ink receiving layer, therefore, the ratio of the content of the first aggregated light calcium carbonate and the content of the second aggregated light calcium carbonate is preferably 10:90 to 90:10, and preferably 10:90 to. It is more preferably 80:20. Here, the "normal temperature" means a temperature at which it is not particularly cooled or heated, that is, a normal temperature, and a temperature of, for example, 15 to 25 ° C is preferable.

(binder)
The binder is a component that holds the pigment in the ink receiving layer.
In the present invention, polyvinyl alcohol and polyurethane are used as the binder. Thereby, the characteristics of the ink receiving layer can be adjusted. For example, by using polyvinyl alcohol and polyurethane in combination, the water resistance of the ink receiving layer is improved, the peeling of the ink receiving layer from the substrate in the presence of water is highly suppressed, and the amount of binder used can be reduced.

Polyvinyl alcohol is a component that affects the stable maintenance of the ink receiving layer, the drying property of the ink, the bleeding of dots, and the water resistance of the ink receiving layer.
The polyvinyl alcohol is not particularly limited as long as the saponification degree is 90 mol% or more, and examples thereof include fully saponified polyvinyl alcohol and partially saponified polyvinyl alcohol.

  The degree of saponification of polyvinyl alcohol is preferably 93 mol% or more, and more preferably 96 mol% or more. When the saponification degree of polyvinyl alcohol is at least the above lower limit, dot bleeding is further suppressed and the water resistance of the ink receiving layer is further improved. The upper limit of the saponification degree of polyvinyl alcohol is not particularly limited and may be, for example, 99 mol% or 100 mol%.

The polymerization degree of polyvinyl alcohol is preferably 1800 or less, more preferably 1750 or less, further preferably 1700 or less, and may be 800 or less, for example. When the degree of polymerization of polyvinyl alcohol is not more than the upper limit value, the drying property of the ink is further improved.
On the other hand, the degree of polymerization of polyvinyl alcohol is preferably 250 or more, more preferably 350 or more, and particularly preferably 400 or more. When the degree of polymerization of polyvinyl alcohol is at least the above lower limit, the water resistance of the ink receiving layer is further improved.

Polyurethane is a component that affects the water resistance of the ink receiving layer and the stability of the composition for the ink receiving layer by itself.
The polyurethane may be cationic, anionic or nonionic, but is preferably nonionic from the viewpoint of further improving the water resistance of the ink receiving layer.

  Specific examples of the polyurethane include ester polyurethane and carbonate polyurethane.

  Each of the polyvinyl alcohol and the polyurethane may be used alone or in combination of two or more. When two or more are used in combination, their combination and ratio are appropriately selected according to the purpose. do it.

In the composition for the ink receiving layer, the mass ratio of the blending amount (content) of polyvinyl alcohol and polyurethane is preferably 90:10 to 20:80, expressed as polyvinyl alcohol: polyurethane, and 90:10 to 30. : 70 is more preferable, and 80: 20 to 30: 70 is further preferable. When the mass ratio is within such a range, the effect of the present invention can be more remarkably obtained.
That is, in the ink receiving layer, the mass ratio of the contents of polyvinyl alcohol and polyurethane, expressed by polyvinyl alcohol: polyurethane, is preferably 90:10 to 20:80, and 90:10 to 30:70. Is more preferable and 80:20 to 30:70 is even more preferable.

The blending amount (content) of the binder in the composition for the ink receiving layer is 5% by mass or more and less than 20% by mass, preferably 5 to 19% by mass, based on the blending amount (content) of the pigment. It is more preferably 5 to 18% by mass, further preferably 5 to 17% by mass, and particularly preferably 6 to 16% by mass. When the blending amount of the binder is equal to or more than the lower limit value, the ink receiving layer can be stably formed, and when the blending amount of the binder is equal to or less than the upper limit value, the drying property of the ink is adjusted to a good range. it can.
That is, in the ink receiving layer, the content of the binder is 5 parts by mass or more and less than 20 parts by mass, preferably 5 to 19 parts by mass, and more preferably 5 to 5 parts by mass based on 100 parts by mass of the content of the pigment. It is 18 parts by mass, more preferably 5 to 17 parts by mass, and particularly preferably 6 to 16 parts by mass.
In the present specification, the term “content of binder” means the content of all binders used, including not only polyvinyl alcohol and polyurethane but also other binders described below, unless otherwise specified. To do.

(Other ingredients)
In the composition for the ink receiving layer, other components may be blended in addition to the pigment and the binder as long as the effects of the present invention are not impaired.
As other components, other binders other than the polyvinyl alcohol and polyurethane, solvents, cationic resins, polyvalent metal salts, pH adjusters, defoamers, foam suppressors, release agents, foaming agents, antioxidants, Preservatives, water-proofing agents, paper strength enhancers, coloring dyes, coloring pigments, dye fixing agents, pigment dispersants, fluorescent whitening agents, ultraviolet absorbers, etc. It can be illustrated.
As the other components, one kind may be used alone, or two or more kinds may be used in combination. When two or more kinds are used in combination, their combination and ratio may be appropriately selected according to the purpose.

Examples of the other binder include water-soluble polymers, and more specifically, polyvinyl alcohol having a saponification degree of less than 90 mol%; cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, and the like. Examples thereof include modified polyvinyl alcohol; oxidized starch; phosphoric acid esterified starch; low cons; casein; carboxymethyl cellulose (CMC).
The other binders 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. .

The compounding amount (content) of the other binder in the composition for the ink receiving layer is preferably 3 parts by mass or less with respect to 100 parts by mass of the total compounding amount (total content) of the polyvinyl alcohol and the polyurethane. It is more preferably 1 part by mass or less. The effect of the present invention can be more remarkably obtained when the content of the other binder is the upper limit or less.
That is, in the ink receiving layer, the content of the other binder is preferably 3 parts by mass or less, and more preferably 1 part by mass or less, based on 100 parts by mass of the total content of the polyvinyl alcohol and the polyurethane. More preferable.
The receiving layer preferably contains only the polyvinyl alcohol and polyurethane as the binder.

  The solvent refers to the dispersion medium when a pigment or a binder is blended as a dispersion and no solvent other than the one used as the dispersion medium is used. When a solvent is separately blended in addition to the one used as the dispersion medium, it means both the dispersion medium and the separately blended solvent. When the pigment and the binder are both mixed as a solid, it means a solvent added separately from these. Water, alcohol, etc. are mentioned as a solvent.

The cationic resin is suitable as a fixing agent for inkjet inks, and is preferably a resin that dissociates and exhibits a cationic property when dissolved in water.
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 an oligomer or polymer. .
More preferable examples of the cationic resin include an alkylamine-epichlorohydrin copolymer; an acrylic polymer having a secondary amino group, a tertiary amino group or a quaternary ammonium group; polyvinylamine; polyvinylamidine; a 5-membered ring. Amidines; dicyan-based cationic resins such as dicyandiamide-formalin copolymer; polyamine-based cationic resins such as dicyandiamide-polyethyleneamine copolymers; polyalkylenepolyamines such as polyethylenepolyamine and polypropylenepolyamine and their derivatives; diallyldimethylammonium-SO ₂ copolymer; diallylamine salt -SO ₂ copolymer; dimethyldiallylammonium chloride polymer; polymer of allylamine salt, homopolymers or copolymerization of vinylbenzyl triallyl ammonium salt Body; dialkylaminoethyl (meth) acrylate quaternary salt copolymer; acrylamide-diallylamine salt copolymer; aluminum salts such as polyaluminum chloride and polyaluminum acetate, and the like, and alkylamine-epichlorohydrin polycondensate Particularly preferred is a dimethylamine-epichlorohydrin polycondensate, and most preferred is a polycondensate of dimethylamine-epichlorohydrin.
In the present specification, the term “derivative” or “class” refers to one in which one or more hydrogen atoms of the original compound are substituted with a group (atom) other than hydrogen atom, unless otherwise specified. means.

  The cation resins may be used alone or in combination of two or more. When two or more kinds are used in combination, their combination and ratio may be appropriately selected according to the purpose.

The compounding amount (content, solid content) of the cationic resin in the composition for the ink receiving layer is preferably 1 to 40% by mass, and more preferably 1 to 25% by mass, based on the compounding amount (content) of the pigment. % By weight.
That is, the content of the cation resin in the ink receiving layer is preferably 1 to 40 parts by mass, and more preferably 1 to 25 parts by mass with respect to 100 parts by mass of the pigment content.

The polyvalent metal salt is a component that improves the drying property of the ink.
Examples of the polyvalent metal salt include calcium chloride, magnesium chloride, aluminum chloride, barium chloride, zinc chloride, calcium sulfate, magnesium sulfate, calcium nitrate, magnesium acetate, calcium acetate and the like. Among them, calcium chloride or magnesium chloride is preferable because it can improve the ink jet printing suitability such as ink drying property, color density, water resistance, and scratch resistance in a well-balanced manner and has high safety.

  The polyvalent metal salts may be used alone or in combination of two or more. When two or more kinds are used in combination, their combination and ratio may be appropriately selected according to the purpose.

The compounding amount (content, solid content) of the polyvalent metal salt in the composition for the ink receiving layer is preferably 3 to 55% by mass, more preferably 3% based on the compounding amount (content) of the pigment. ~ 25% by weight.
That is, the content of the polyvalent metal salt in the ink receiving layer is preferably 3 to 55 parts by mass, and more preferably 3 to 25 parts by mass with respect to 100 parts by mass of the pigment content.

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

(Method for producing composition for ink receiving layer)
The composition for the ink receiving layer can be produced by mixing the pigment, the binder, and other components as necessary, and thoroughly stirring the components. In the composition of the present invention, the pigment and the binder are preferably dispersed together.

  Each component may be blended at once, may be blended sequentially for each component, or only some of the components may be blended together. The mixing order of each component is not particularly limited.

The temperature at the time of compounding is not particularly limited and may be appropriately adjusted depending on the type of compounding ingredients and the like, but is preferably 15 to 30 ° C.
The 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 depending on the total amount of the composition to be produced, the stirring method, and the like.

  The inkjet recording sheet of the present invention can be produced by applying the above composition for an ink receiving layer onto a substrate and drying the composition to form an ink receiving layer.

  The material of the base material is not particularly limited and may be selected according to the purpose as long as it can form a coating layer. Specifically, 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 resin, phenol resin, urea resin, polyurethane, polyimide Examples thereof include synthetic resins. Further, the substrate may be a laminate of two or more kinds of materials.

  The thickness of the base material is not particularly limited as long as the shape of the base material is a sheet shape or a film shape, but is preferably 20 to 1000 μm, and more preferably 50 to 200 μm. When the thickness of the base material is at least the 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 most the upper limit value, the handleability as a recording sheet is improved. It will be better.

  The method for applying the composition for the ink receiving layer is not particularly limited and may be any method as long as it can apply a liquid material. Specifically, various coaters such as air knife coater, curtain coater, die coater, blade coater, roll coater, gate roll coater, bar coater, rod coater, gravure coater, and gravure offset coater; equipment such as wire bar coater is used. Known methods can be exemplified.

The coating of the composition for the ink receiving layer may be performed once, or may be performed in multiple times. When the coating is carried out in plural times, a method of further coating the composition for the ink receiving layer on the dried coating layer, and a method of further coating the ink on the non-dried coating layer. Any method of applying the layer composition may be used.
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, the desired thickness of the ink receiving layer, and the like.

  The coated ink-receiving layer composition may be dried by a known method such as blast drying or heated blast drying. The conditions such as the drying temperature and the drying time may be appropriately set according to the drying method.

  The thickness of the ink receiving layer is preferably 1 to 30 μm, more preferably 2 to 20 μm. When the thickness is within such a range, the structure of the ink receiving layer can be held more stably, and the effect of the present invention provides an excellent recording sheet.

  The recording sheet of the present invention may be provided with the ink receiving layer on at least one surface of the substrate, and may be provided on only one surface or on both surfaces.

  The surface of the recording sheet of the present invention is smoothed by using an apparatus such as a machine calender, a TG calender, a super calender, a soft calender, a gloss calender, a compact calender, a mat super calender and a mat calender after forming the ink receiving layer. It may have been done.

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

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

  The recording sheet whose surface is smoothed after the ink receiving layer is formed on the base material is compressed in the thickness direction, so the base material and ink receiving layer are more clogged and the air permeability is reduced. However, the value of the air permeability described later becomes large, and normally, the ink does not pass easily and the drying property tends to decrease. However, in the present invention, a decrease in the drying property of the ink can be suppressed by adjusting the components contained in the ink receiving layer such that polyvinyl alcohol and polyurethane are used together as the binder and the amount of the binder used is reduced.

  The glossiness of the surface of the smoothed recording sheet is high. For example, the recording sheet of the present invention may have a glossiness of 75 ° measured according to JIS-P8142: 2005 of preferably 15 to 50%, more preferably 20 to 50%.

The recording sheet of the present invention has an air permeability of 600 seconds or less regardless of the presence or absence of the smoothing treatment and whether the ink receiving layer is provided only on one side or both sides of the substrate. Preferably, it is 500 seconds or less, more preferably 400 seconds or less, and even more preferably, the air permeability is such that the ink drying property of the recording sheet becomes higher. The recording sheet of the present invention has, for example, higher air permeability when the ink receiving layer is provided on both sides of the substrate than when the ink receiving layer is provided on only one side of the substrate. Especially, the air permeability in the above range is likely to occur. On the other hand, the recording sheet of the present invention has a lower air permeability when the ink receiving layer is provided only on one side of the substrate than when the ink receiving layer is provided on both sides of the substrate. For example, the air permeability is preferably 280 seconds or less.
On the other hand, the lower limit of the air permeability of the recording sheet of the present invention is not particularly limited, and for example, regardless of the presence or absence of the smoothing treatment, the ink receiving layer is provided on either one side or both sides of the substrate. It is preferably 90 seconds, regardless of whether it is provided.
Here, the "air permeability" is a value (Gurley type air permeability) measured according to JIS P 8117: 2009.

  Among them, the recording sheet of the present invention preferably has an air permeability of 600 seconds or less and a gloss of 75 ° of 15 to 50% from the viewpoint that the effect of the present invention can be more remarkably obtained.

The recording sheet of the present invention is suitable as an inkjet recording sheet as described above, but is also suitable as a liquid toner recording sheet. When the recording sheet of the present invention is used as a recording sheet for liquid toner, the ink receiving layer functions as a liquid toner receiving layer.
Since the ink-receiving layer of the recording sheet of the present invention is composed of the material in the above-mentioned specific range, it can be used for both inkjet and liquid toner, 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 described below.
In addition, in the table shown below, the blank column of the blending component means that the component is not blended. In addition, the blank evaluation result column means that the item has not been evaluated.

<Material used>
In the following examples and comparative examples, the composition for ink receiving layer was applied to a substrate to manufacture an inkjet recording sheet.

  In the production of the composition for the ink receiving layer, aggregated light calcium carbonate having the physical properties shown in Table 1 (synthetic calcium carbonate which is aggregated particles) was used as the pigment. In Table 1, the average primary particle diameter 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 diameters of 20 primary particles. In Table 1, the average secondary particle diameter or the average particle diameter was measured by the laser diffraction method using MICROTRAC MT3000 (trade name, manufactured by Nikkiso Co., Ltd.). The measurement results were converted to the number basis.

  As the binder, polyvinyl alcohol (“PVA105”, “PVA205”, “PVA117” manufactured by Kuraray Co., Ltd.) having characteristics shown in Table 2 and polyurethane (“Superflex E-2000” manufactured by Dai-ichi Kogyo Co., Ltd. (nonionic ester) Type polyurethane emulsion), "Superflex 6200" (cationic ester type polyurethane emulsion), and hereinafter may be abbreviated as "SFE2000" and "SF620", respectively).

As the cationic resin, an alkylamine-epichlorohydrin polycondensate (“Jetfix 260” manufactured by Satoda Kako Co., Ltd.) was used.
Calcium chloride was used as the polyvalent metal salt.

  Table 3 shows the components and amounts of the ink receiving layer composition. (A) to (B) in Table 3 correspond to the pigments (A) to (B) whose physical properties are shown in Table 1, respectively. The unit of the numbers in Table 3 is parts by mass, which are all solid contents.

[Example 1]
To 40 parts by mass of pigment (A) (aggregated light calcium carbonate having an average secondary particle diameter of 0.49 μm) and 60 parts by mass of pigment (B) (aggregated light calcium carbonate having an average secondary particle diameter of 3.39 μm), polyvinyl alcohol ( 5 parts by mass (solid content) of (PVA105)), 2.5 parts by mass (solid content) of polyurethane ("SFE2000"), 10 parts by mass of cationic resin ("Jetfix260"), and 8.5 parts by mass of calcium chloride. In addition, water was added so that the solid content concentration was 40%, and the mixture was sufficiently dispersed by stirring using a stirrer to manufacture an ink receiving layer composition.
Using the wire bar coater, apply the manufactured ink receiving layer composition onto one side of a substrate (foam paper, “NPi foam <90>” manufactured by Nippon Paper Industries Co., Ltd., thickness 128 ± 8 μm, A4 size) Then, it was heated and dried at 105 ° C. for 60 seconds by using an oven to form an ink receiving layer having a thickness of 10 μm. Next, the base material on which the ink receiving layer was formed was subjected to a smoothing treatment with a calendar by the following method to produce an inkjet recording sheet.

<Smoothing>
Using an actual super calender device with a roll temperature set to 40 to 50 ° C., smoothing treatment was performed so that the glossiness was 10 to 50.

[Examples 2 to 20, Comparative Examples 1 to 14]
InkJet of Examples 2 to 20 and Comparative Examples 1 to 14 in the same manner as Example 1 except that at least one of the compounding components and the compounding amounts of the composition for the ink receiving layer is as shown in Table 3 or 4. A recording sheet was manufactured. Examples 6 and 7 were different from Example 5 in the scale of calendering, and the calender roller diameter of the apparatus used was about 3 times that of Example 5 in Examples 6 and 7. Otherwise, the same method as in Example 5 was used, and the same method was repeated twice. All the Examples and Comparative Examples other than Examples 5 to 7 were performed on the same scale as Example 5.

  The following items were evaluated with respect to the inkjet recording sheet obtained above.

[Dryability evaluation]
A water-based black pigment ink having a size of 2 cm × 2 cm was solidly printed (single color printing) on the ink receiving layer of the inkjet recording sheet of each of the above Examples and Comparative Examples using a desktop inkjet printer. Subsequently, the time (seconds) from immediately after the paper was discharged until the ink was dried was visually determined, and the dryness of the ink was evaluated according to the following evaluation criteria. It should be noted that if the time required for drying the ink is 3.6 seconds or less, good drying properties are exhibited even when printed with a high-speed inkjet printer (printing speed 500 f (152.4 m) / min). I checked in advance. Further, even when the time required for drying the ink is more than 3.6 seconds and 5.1 seconds or less, printing with a high-speed inkjet printer (printing speed 500 f (152.4 m) / minute) may be possible. The results are shown in Table 5 or 6. The time (seconds) required for drying is shown in parentheses.
Time required for ink drying is 3.6 seconds or less: ○
Time required for ink drying is more than 3.6 seconds and less than 5.1 seconds: △
Time required for ink drying exceeds 5.1 seconds: ×

[Evaluation of dot blur]
The dot blurring was evaluated by the dot shape factor. An evaluation sample was prepared by using a desktop inkjet printer, and a water-based black pigment ink having a size of 2 cm × 2 cm was formed on the ink receiving layer of the inkjet recording sheet of each of the above-mentioned Examples and Comparative Examples so that the density was 10 It was created by printing in% (single color printing). Subsequently, a microscope image of the surface of the inkjet recording sheet was taken and analyzed with a dot analyzer (DA6000, manufactured by Oji Scientific Instruments). Specifically, the perimeter and area of each dot were measured, and the dot shape coefficient was calculated according to the following formula.
Dot shape factor = (perimeter) ² / (4π x area)

  The dot shape coefficient becomes 1 when the dot is a perfect circle, and becomes larger as the shape of the dot is farther from the perfect circle, that is, as the dot is blurred. The dot shape factor measured with a desktop inkjet printer (printing speed 0.43f (0.13m) / min) is sufficient as the dot shape factor measured with a high-speed inkjet printer (printing speed 500f (152.4m) / min). It was confirmed in advance that there was a strong correlation.

With respect to each of the inkjet recording sheets of the above Examples and Comparative Examples, the dot shape coefficient of about 30 dots was calculated and the average value was obtained, and the dot bleeding was evaluated according to the following evaluation criteria. The results are shown in Table 5 or 6. The average value of the dot shape factor is shown in parentheses.
1.8 or less: ○
More than 1.8 and less than 2.0: △
Over 2.0: ×

[Evaluation of water resistance]
To the ink receiving layer formed on the base material, 10 μL of tap water was dropped, and a polyethylene terephthalate film having a thickness of 50 μm was placed thereon, and a metal roller having a weight of 2 kg was reciprocated twice on this film. After that, the film was peeled off, and the state of the ink receiving layer on the substrate was visually evaluated based on the degree of breakage and peeling based on the following criteria. The results are shown in Table 5 or 6.
A: The ink receiving layer is not broken or peeled off.
B: Some peeling of the ink receiving layer is recognized, but there is no problem in actual use.
C: Clear peeling of the ink receiving layer is recognized.
D: The ink receiving layer is broken and peeled off.

[Evaluation of glossiness of 75 °]
According to JIS-P8142: 2005 "Paper and board-Method for measuring 75-degree specular gloss", a gloss meter ("Glossmeter GM26D" manufactured by Murakami Color Research Laboratory) is used to measure the gloss of the paper surface at 75 ° (% ) Was measured. The results are shown in Table 5 or 6.

[Evaluation of air permeability]
It was measured according to JIS P 8117: 2009. The results are shown in Table 5 or 6.

[Example 21]
An ink jet recording sheet was produced and evaluated in the same manner as in Example 17, except that the composition for the ink receiving layer was applied to both sides of the substrate instead of one side, and heating and blowing were performed. That is, the ink jet recording sheet of this example is provided with the ink receiving layer on both surfaces of the base material. The results are shown in Table 5.

The ink jet recording sheets of Examples 1 to 21 showed little dot bleeding, good drying property, and high water resistance (water resistance) of the ink receiving layer even when subjected to the smoothing treatment. This is because polyvinyl alcohol and polyurethane are used together as a binder, polyvinyl alcohol having a saponification degree in a specific range is used, and the content of the binder in the receiving layer is in a specific range.
As described above, even when the ink-jet recording sheet of the present invention is subjected to the smoothing treatment by the calendar after the formation of the ink receiving layer, the dot bleeding is small and the drying property is good even when the ink jet printing is performed by the high speed printer. It was confirmed that the water resistance was excellent.

  On the other hand, the ink jet recording sheets of Comparative Examples 1 to 4, 6 and 9 using only polyvinyl alcohol as the binder had low water resistance (water resistance) of the ink receiving layer. Further, the inkjet recording sheets of Comparative Examples 11 to 12 were inferior in drying property and the dot bleeding was remarkable, and the inkjet recording sheet of Comparative Example 13 was inferior in drying property. Further, Comparative Example 5 using only polyvinyl alcohol having a low saponification degree as a binder, Comparative Example 10 using polyvinyl alcohol having a low saponification degree, and using only polyvinyl alcohol as a binder, the content of the binder in the receiving layer is high. In each of the inkjet recording sheets of Comparative Example 7, the water resistance (water resistance) of the ink receiving layer was low. The inkjet recording sheet of Comparative Example 4 was also inferior in drying property. Further, the inkjet recording sheet of Comparative Example 8 in which polyvinyl alcohol was not used was inferior in drying property. The inkjet recording sheet of Comparative Example 14 using only polyvinyl alcohol as a binder was not evaluated because the ink receiving layer peeled off from the base material, so-called “powder drop” occurred.

The inkjet recording sheet of Example 1 was further evaluated for the fixability of liquid toner by the method described below.
(Fixability of liquid toner)
After printing on an ink jet recording sheet using a liquid toner type electrophotographic printer (HP Indigo series), cellophane tape (registered trademark) is applied to the printing surface (solid surface) of the sheet by the liquid toner. Was pasted. At this time, the length of the attached portion of the tape was about 50 mm.
Then, a weight having a weight of 2 kg was placed on the tape, and in this state, the weight was reciprocated once on the tape to apply pressure, whereby the tape was completely attached to the printed surface.
Then, 30 seconds after the tape is completely attached in this manner, one end of the tape is pinched with a finger, and the tape is moved in a direction horizontal to the printing surface and toward the other end of the tape. I peeled off the tape. The peeling time at this time was 0.5 to 1.0 second, and the tape was peeled off reliably.
Then, the state of the liquid toner printing surface of the inkjet recording sheet after the tape was peeled off was visually observed, and the peeling resistance of the ink receiving layer (liquid toner fixing property) was evaluated according to the following criteria.
A: No peeling of the ink receiving layer was observed on the surface printed with the liquid toner, and the peeling resistance of the ink receiving layer was high.
B: Some peeling of the ink receiving layer is recognized on the liquid toner printed surface.
C: Clear peeling of the ink receiving layer is recognized on the surface printed with the liquid toner.
D: The surface on which the liquid toner is printed is peeled up.

  As a result, the evaluation result of the ink jet recording sheet of Example 1 was A, and it was confirmed that this ink jet recording sheet can be sufficiently used as a liquid toner recording sheet.

  INDUSTRIAL APPLICABILITY The present invention can be used for an inkjet recording sheet applied to inkjet printing in a high speed printer. Further, the present invention can be applied to a recording sheet for liquid toner.

Claims (5)

A recording sheet comprising a substrate and an ink receiving layer formed on at least one surface of the substrate,
The receiving layer contains a pigment and a binder,
The receiving layer contains polyvinyl alcohol and polyurethane as the binder,
The polyvinyl alcohol has a saponification degree of 90 mol% or more,
The receiving layer, the content of the binder is, Ri less than 20 parts by mass der 5 parts by mass or more relative to the content 100 parts by mass of the pigment,
The pigment, Ru der aggregation precipitated calcium carbonate, the recording sheet.   The recording sheet according to claim 1, which has an air permeability of 600 seconds or less and a glossiness of 75 ° of 15 to 50%. The recording sheet according to claim 1, wherein the aggregated light calcium carbonate comprises a first aggregated light calcium carbonate and a second aggregated light calcium carbonate having different average secondary particle diameters. The recording sheet according to claim 3, wherein 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 μm to 5 μm. . The recording sheet according to claim 3 or 4, wherein the mixing ratio of the first agglomerated light calcium carbonate and the second agglomerated light calcium carbonate is 10:90 to 90:10 in mass ratio.