JP4375328B2 - Glossy inkjet recording paper - Google Patents

Description

  The present invention relates to glossy inkjet recording paper.

  The inkjet recording method that forms an image by ejecting water-based ink from fine nozzles is easy to make full color, high-speed recording is possible, and printing cost is lower than other printing devices for printing a small number of copies. For some reason, it is widely used in terminal printers, facsimiles, plotters, and form printing.

In recent years, ink jet printers have been rapidly spread and have high definition and high speed, and accordingly, ink jet recording papers are required to have higher ink absorption speed and higher surface strength than ever before.
Furthermore, there is a strong demand for the realization of high image quality comparable to silver halide photography for recorded images taken with a digital camera.
Further, in order to bring the quality of a printed image closer to that of a silver salt photograph, further improvement in the color density and glossiness of the printed image is desired.

On the other hand, in order to realize image storability equivalent to that of silver salt photographs, improvement of the ink itself has been proposed.
Aqueous dye ink using a highly hydrophilic colorant that occupies the mainstream of conventional ink jet recording inks (hereinafter referred to as dye ink) and a hydrophobic color pigment having excellent water resistance and light resistance as a colorant Ink (hereinafter referred to as “pigment ink”) is also often used.
The colored pigment in the pigment ink tends to stay on the coated surface, and the high gloss inkjet recording paper for the dye ink that has been used so far is inferior in fixability and scratching property of the pigment ink.
For this reason, there is a strong demand for ink jet recording paper capable of printing with high image quality for both dye ink and pigment ink.

  In order to achieve this, technology to obtain higher ink absorption speed and gloss, such as suppressing cracks in the coating film and reproducing the roundness of dots, is essential. The receiving layer is formed to contain fine pigments, and the peak of the pore diameter distribution curve in the plurality of pores formed between the fine pigments can be controlled to be occupied by pores of approximately 0.1 μm or less. is necessary.

As a technique for obtaining a high ink absorption rate and gloss, for example, the ink recording layer contains inorganic pigment fine particles which are primary particles composed of simple particles and have an average particle diameter of 20 nm or less, and polyvinyl alcohol as a binder. Inkjet recording papers have been proposed.
This recording paper uses a cross-linking reaction between borax or boric acid and polyvinyl alcohol to gel the paint before the ink recording layer exhibits a reduced drying rate, thereby cracking the coating film. A high coating amount is imparted while suppressing, the roundness of dots is reproduced, and an excellent image quality can be obtained in a dye ink (Patent Document 1).
As a further improvement of the recording paper, an undercoat layer coated with boric acid or a boron compound with a limited coating amount is provided between the support and the ink recording layer, and the content is limited on the surface thereof. An ink recording layer including inorganic pigment fine particles and polyvinyl alcohol has also been proposed. This recording paper further improves cracks in the coating film (Patent Document 2).
However, in these recording papers, the surface gloss of the surface layer is insufficient, and the ink absorptivity when pigment ink is used is not yet sufficient.

In addition, after applying the first porous layer to a non-water-absorbing support and drying, or before the completion of drying, air bubbles are formed on the membrane surface produced by applying the second porous layer. Inkjet recording papers that do not generate ink have been proposed.
With this recording paper, an ink recording layer free from bubbles and cracks can be formed by the manufacturing method (Patent Document 3).
However, the gloss and ink absorption speed of the ink jet recording paper have not been sufficient yet.

Furthermore, an ink jet recording paper manufacturing method using a water-absorbing base paper as a support has been proposed.
In this recording paper, a borax or boric acid-treated layer and an ink receiving layer containing polyvinyl alcohol are sequentially provided on the glossy side of the glossy paper, and these are cross-linked to form a bond between the base paper and the ink receiving layer. The strength is increased, the image quality of the recorded image is improved, and the dimensional stability is excellent (Patent Document 4).
Further, an improved recording paper has been proposed in which a coating amount of borax or boric acid and a coating amount of an ink receiving layer are limited (Patent Document 5).
However, although these recording papers can control cracking to some extent due to the gelation effect of borax or the like, high gloss and print density are not obtained.

As a technique for imparting gloss, for example, a technique has been proposed in which a gloss-expressing layer containing colloidal particles and a polymer latex is provided on an ink recording layer mainly containing a micron order pigment. With this configuration, a certain level of gloss can be obtained (Patent Document 6).
However, in this technique, since the dye in the ink is fixed on the micron-order ink recording layer, the print density is low and the uniformity of the image is inferior. In addition, since the peak of the pore diameter distribution curve in the plurality of pores formed in the glossy layer is occupied by pores larger than 0.1 μm, the glossy layer is cracked, the visual gloss is low, and the pigment ink There was a problem that the print density of the ink was also inferior.

In order to further increase the gloss, a method has been proposed in which the glossy layer formed by the coating layer is subjected to a casting process in which the layer is pressed against a heated mirror drum in a wet state, and the mirror surface is copied. By this method, a certain level of gloss can be obtained (Patent Document 7).
However, since the glossy layer has cracks, the uniformity of the image is inferior, and the print density and the suitability of the pigment ink have not been solved.

Further, while the recording layer provided with two or more recording layers on the substrate and the coating layer containing the aggregate pigment having an average particle diameter of 1 μm or less on the surface layer is in a wet state. There has been proposed an attempt to solve problems such as gloss, print density, ink absorbency, etc. by performing a casting process for pressure bonding to a heated mirror drum (Patent Document 8).
However, since the peak of the pore diameter distribution curve in the plurality of pores formed on the outermost layer is not occupied only by pores of 0.1 μm or less, and cracks on the outermost layer are not controlled, The dots were not round, the print density was insufficient, and the image uniformity was low.

In addition, with recent high-definition and high-speed printers, ink absorbency has been insufficient.
For this reason, when pigment ink is used, a large amount of the color pigment is absorbed in the cracked portion of the coating film, resulting in unevenness in the image and low print density, which is inappropriate.
In addition, these recording papers employ a recording layer with a reduced binder amount to increase the amount of ink absorbed as the amount of ink increases, so the surface strength, printer transportability, It was not satisfied with cockling (absorption wrinkles), but caused problems such as printing failure due to rubbing of the head.

On the other hand, a recording sheet resin composition comprising an oxyalkylene group-containing polyvinyl alcohol resin and a cationic group-containing polyvinyl alcohol resin has also been proposed.
This technology has a certain effect on the printability such as ink acceptability, bleeding prevention property, glossiness, and light resistance (Patent Document 9).
However, this recording sheet resin composition does not limit the layer in which the resin is used, and does not satisfy the printing density, the surface strength of the outermost layer of the recording sheet, and the ink scratching property.

Japanese Patent Laid-Open No. 11-115308 JP 2001-246832 A JP 2000-301828 A JP-A-5-104848 Japanese Patent Publication No. 7-37175 Japanese Patent Laid-Open No. 7-101142 Japanese Unexamined Patent Publication No. 7-117335 JP 2001-10220 A JP 2003-26885 A

  The present invention has been made in view of the above circumstances, and its technical problem is that it has good recording properties with respect to dye ink, and has a high ink absorption speed and gloss, and pigment ink. The ink absorptivity is good, the unevenness of ink agglomeration during printing is prevented, the scratch resistance and the print density are excellent, and dye ink and pigment ink can be shared. An object of the present invention is to provide a glossy ink jet recording paper in which the occurrence of (absorption wrinkles) is prevented, print defects due to head rubbing due to this are prevented, and the paper transportability of the printer is excellent.

The glossy ink jet recording paper of the present invention for solving the above problems contains amorphous silica, which is formed on a support and is a secondary particle having an average particle diameter of 90 to 700 nm as a pigment. An ink receiving layer containing a binder to hold, and an outermost layer formed on the ink receiving layer, containing colloidal particles as a pigment, and containing a polyoxylene group-containing polyvinyl alcohol as a binder for holding the pigment. The outermost layer is characterized by having a glossy surface by a glossing process that is a cast process .

According to a preferred configuration aspect of the present invention, the glossing treatment is a wet cast casting process .

According to another preferred embodiment of the present invention, the composition ratio between the colloidal particles contained in the outermost layer and the polyoxylene group-containing polyvinyl alcohol is such that the polyoxylene group-containing polyvinyl alcohol is 100 parts by mass of the colloidal particles. 1 to 30 parts by mass, and the colloidal particles are cationic colloidal silica. Furthermore, it is preferable that the colloidal particles are made of colloidal silica as a single particle dispersion and have an average particle diameter of 3 to 200 nm.
Moreover, it is preferable that the ink receiving layer is provided via an undercoat layer which is provided on a support and contains a pigment and an adhesive which is a binder thereof.

  The glossy ink jet recording paper of the present invention not only has good recording suitability for dye ink, but also has excellent ink absorptivity, print density, scratching and print gloss for pigment ink. Ink and pigment ink can be shared, and furthermore, the occurrence of cockling (absorption wrinkles) is prevented, print defects due to head rubbing due to this are prevented, and it is also suitable for the paper transportability of the printer.

The glossy inkjet recording paper according to the present invention will be described in detail based on the following embodiments.
The glossy ink jet recording paper of the present embodiment contains and retains an undercoat layer formed on a support and amorphous silica, which is a secondary particle having an average particle diameter of 90 to 700 nm as a pigment. An ink receiving layer containing a binder, and an outermost layer formed on the ink receiving layer, containing colloidal particles as a pigment, and containing a polyoxylene group-containing polyvinyl alcohol as a binder for holding the colloidal particles. However, this outermost layer becomes a glossy surface by a glossing process which is a cast process .

<Support>
The support for the glossy inkjet recording paper of the present embodiment is not particularly limited, but a gas-permeable support is preferable, and a paper base material and a gas-permeable resin film or sheet material are used. In particular, it is preferable to use a gas-permeable paper base material.
As the support made of the paper substrate, a known paper substrate that is usually used can be used as long as the effects of the present invention are not impaired. For example, fine paper, art paper, coated paper, cast coating Acid paper, neutral paper, and the like used for paper, kraft paper, baryta paper, paperboard, impregnated paper, vapor-deposited paper, and general coated paper are appropriately used.
The paper base material contains wood pulp as a main component, and fillers, various auxiliaries and the like are added as necessary.

The outline | summary of these paper base materials is demonstrated.
As the wood pulp, various chemical pulps, mechanical pulps, recycled pulps and the like can be used.
These pulps can be adjusted in beating degree (freeness), and the freeness is preferably 250 to 550 ml (CSF: JIS-P-8121), more preferably 300 to 500 ml.

As the filler added to the paper substrate, for example, calcium carbonate, calcined kaolin, silica, titanium oxide and the like are preferably used. Among these, calcium carbonate is preferable because a paper base material with high whiteness is obtained and glossiness of the ink jet recording paper is enhanced.
As for the content rate (ash content) of the filler in a paper base material, about 1-20 mass% is preferable, More preferably, it is 7-20 mass%.
Within this range, smoothness, air permeability, and paper strength are balanced, and it becomes easy to obtain a glossy inkjet recording paper excellent in glossiness and image sharpness.

Examples of the auxiliary agent added to the paper substrate include a sizing agent, a fixing agent, a paper strength enhancer, a cationizing agent, a yield improver, a dye, and a fluorescent brightening agent.
The Stechitto sizing degree (100 g / m ² paper) of the paper substrate is preferably about 1 to 200 seconds, and more preferably 4 to 120 seconds.
The basis weight of the paper substrate is not particularly limited, but is preferably about ²⁰ to 400 g / m ² .
The Oken type air permeability of the paper substrate is preferably 10 to 350 seconds. 10 to 200 seconds are more preferable, and 20 to 100 seconds are more preferable.
When the air permeability is less than 10 seconds, the coating solution for the undercoat layer excessively penetrates the support made of the paper base material, and when the air permeability exceeds 350 seconds, In addition, the operability is lowered, which is not preferable.

<Undercoat layer>
The undercoat layer provided in the glossy inkjet recording paper of the present embodiment is for improving the ink absorption capacity and the absorption speed, and is not limited to a single layer, and a plurality of layers may be provided. This undercoat layer contains a pigment as a main component and an adhesive as its binder.
As such an undercoat layer, an amorphous silica of secondary particles having an average particle diameter of 10 μm or less as a pigment, and an adhesive containing at least one selected from a water-soluble adhesive and a water-dispersible adhesive as a binder. It is preferable to contain.
By providing this undercoat layer on the support, the glossy ink jet recording paper has good ink absorptivity, and is excellent in printing density, printing bleeding, solid uniformity, and the like.

[Pigment]
As the pigment for the undercoat layer, amorphous silica having primary particles made up of simple particles aggregated and having an average particle diameter of 3 to 5 μm is preferably used.
The average particle diameter of the secondary particles in the amorphous silica is a particle diameter obtained by observing the silica particles in the silica aqueous dispersion with an electron microscope (SEM, TEM). It is a thing. (See "Particle Handbook", Asakura Shoten, p. 52, 1991).
When the average particle diameter of the amorphous silica is less than 3 μm, the ink absorption rate is lowered and the strength of the undercoat layer is also lowered. When the average particle diameter is more than 5 μm, the glossiness when the outermost surface is cast finished. And ink absorbency are not sufficient.

In the undercoat layer, not only the above-mentioned amorphous silica but also known pigments that are usually used can be used in combination as long as the effects of the present invention are not impaired.
Examples of these pigments include kaolin, clay, calcined clay, zinc oxide, aluminum oxide, titanium oxide, aluminum hydroxide, calcium carbonate, satin white, aluminum silicate, colloidal silica, zeolite, synthetic zeolite, sepiolite, smectite, synthetic Examples thereof include smectite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, hydrotalcite, urea resin plastic pigment, and benzoguanamine plastic pigment. The pigments used in combination selected from these may be used alone or in combination of two or more.

〔adhesive〕
In the undercoat layer, a commonly used known adhesive is used as a binder for the pigment.
Examples of the adhesive include caseins, proteins such as soybean protein and synthetic protein, various starches such as starch and oxidized starch, polyvinyl alcohol, cationic polyvinyl alcohol, and modified polyvinyl alcohol such as silyl-modified polyvinyl alcohol. Polyvinyl alcohols, cellulose derivatives such as carboxymethylcellulose and methylcellulose, and water-soluble adhesives such as aqueous polyurethane resins and aqueous polyester resins, conjugated diene polymer latexes of styrene-butadiene copolymers and methyl methacrylate-butadiene copolymers, Examples thereof include water-dispersible adhesives such as acrylic polymer latex and vinyl polymer latex such as ethylene-vinyl acetate copolymer.
The adhesive selected and used from these may be used alone or in combination of two or more.

  The adhesive for the undercoat layer is preferably 20 to 100 parts by mass with respect to 100 parts by mass of the amorphous silica. When the amount is less than 20 parts by mass, the generation of paper dust at the time of cutting cannot be sufficiently suppressed.

In addition to the above-mentioned components, various auxiliary agents such as ink fixing agents, dispersants, thickeners, antifoaming agents, antistatic agents, preservatives and the like, which are used in general recording paper production, are appropriately added to the undercoat layer. be able to.
In addition, fluorescent dyes, colorants and the like can be added.

[Ink fixing agent]
It is particularly preferable to add the ink fixing agent to the undercoat layer.
The ink fixing agent is for fixing the pigment of the dye ink, and as the ink fixing agent, a cationic compound is used in order to obtain good coloring property and storage property of the dye ink and ink absorbability. Is preferred.
Examples of the cationic compound include a cationic resin and a low molecular weight cationic compound (for example, a cationic surfactant). In order to improve the printing density, a cationic resin is preferable, and the water-soluble resin or emulsion can be used.
These cationic compounds also have the effect of improving the water resistance of printed images.
The cationic resin is insolubilized by means such as cross-linking, and can be made into a particulate form so that it can be used as a cationic organic pigment instead of the ink fixing agent. When the cationic organic resin is polymerized, the polyfunctional monomer is copolymerized to form a cross-linked resin, or has a reactive functional group (hydroxyl group, carboxyl group, amino group, acetoacetyl group, etc.). It is formed by any method of adding a crosslinking agent to the cationic resin as necessary and forming the crosslinked resin by means of heat, radiation or the like.
In addition, the cationic resin may serve as an adhesive.

Examples of the cationic resin include (a) polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine or derivatives thereof, (b) acrylic polymers having secondary or tertiary amino groups and quaternary ammonium groups, or These acrylamide copolymers, (c) polyvinylamine and polyvinylamidines, (d) dicyan-based cationic compounds represented by dicyandiamide-formalin copolymer, and (e) dicyandiamide-polyethyleneamine copolymer. Polyamine-based cationic compounds, (he) epichlorohydrin-dimethylamine copolymer, (to) diallyldimethylammonium-SO ₂ polycondensate, (thi) diallylamine salt-SO ₂ polycondensate, (li) diallyldimethylammonium chloride polymerization , (Nu) diallyldimethylammonium chloride-acrylamide copolymer, (le) allylamine salt copolymer, (e) dialkylaminoethyl (meth) acrylate quaternary salt copolymer, (wa) acrylamide-diallylamine copolymer And (f) dimethylaminopropylacrylamide polymer.
These fixing agents may be used alone or in combination of two or more.

The said cationic compound can be used in 1-100 mass parts with respect to 100 mass parts of pigments, More preferably, it is 5-50 mass parts.
When the blending amount is less than 1 part by mass, the effect of improving the printing density is small, and when it exceeds 100 parts by mass, the printing density may be lowered or image blurring may occur.

[Method for producing undercoat layer]
The dry coating amount of the undercoat layer is 5 to 20 g / m ² .
If the dry coating amount is less than 5 g / m ² , the ink absorbency is not sufficient, and even if it exceeds 20 g / m ² , the print gloss is not further improved.

The undercoat layer is produced by applying an undercoat layer coating solution comprising the above-described components onto the support and drying it. The solid content concentration of the undercoat layer coating solution is preferably 5 to 50% by mass.
As a coating method for the undercoat layer coating solution, various known methods such as a blade coater, an air knife coater, a roll coater, a brush coater, a Chanplex coater, a bar coater, a lip coater, a gravure coater, a curtain coater, a slot die coater, a slide coater, etc. A coating method using any of the coating apparatuses can be used.
Further, the coated undercoat layer may be subjected to a smoothing process such as super calendering or brushing as necessary.

<Ink receiving layer>
In the glossy ink jet recording paper of the present embodiment, an ink receiving layer is provided on the undercoat layer. This ink receiving layer is coated on the undercoat layer as an aqueous coating solution.
This ink receiving layer contains silica as a pigment, and contains an adhesive as a binder for holding the pigment. The pigment contains amorphous silica , and the adhesive is particularly polyvinyl alcohol. Preferably used.
The amorphous silica is a secondary particle having an average particle diameter of 90 to 700 nm, and the polyvinyl alcohol having a polymerization degree of 3500 or more is used.
Then, the ink receiving layer composed of these is coated so that an ink fixing agent is added as necessary, and a dry coating amount becomes a layer of 5 to ²⁰ g / m ² .
By providing this ink receiving layer, the glossy ink jet recording paper is less likely to generate paper dust during cutting, has a higher printing density than the dye ink, and has excellent water resistance. For pigment ink, the printing density is high and the glossiness is high.

[Pigment]
The amorphous silica as the pigment has insufficient ink absorbability when the average particle diameter is less than 90 nm, and when it exceeds 700 nm, the print density and surface glossiness are lowered.
As the amorphous silica, wet method silica, gas phase method silica and the like are preferably used.
The amorphous silica is obtained by, for example, pulverizing and dispersing commercially available primary particles of gas phase method silica to form secondary particles, and classifying them to prepare a silica dispersion having the above average particle diameter. It is preferable to add a cationic polymer compound having an amidine structure or the like, and further crush and disperse it to use, for example, a cationic polymer compound-silica composite particle dispersion containing secondary particles having an average particle size of 0.15 μm.
In the ink receiving layer, one or more other known pigments can be used in combination as long as the effects of the present invention are not impaired.
The pigments used in combination are the same as the pigments used in combination with the pigment of the undercoat layer described above.

〔adhesive〕
The polyvinyl alcohol used in the ink receiving layer preferably has a degree of polymerization of 3500 or more, particularly preferably 3500 to 5000. When the degree of polymerization is less than 3500, the strength of the ink receiving layer is weak and cracking is likely to occur, and a sufficient print density cannot be obtained particularly in a pigment printer. If the degree of polymerization exceeds 5000, sufficient ink absorbability cannot be obtained, and handling in preparing the coating liquid becomes difficult.

The ink receiving layer is not limited to the above-mentioned polyvinyl alcohol having a degree of polymerization of 3500 or more, and a known adhesive that is usually used is used as a binder for the pigment as long as the effects of the present invention are not impaired.
As this adhesive, the same adhesive as the above-mentioned adhesive used for the undercoat layer can be used. And the adhesive selected and used from these may be individual, or may be 2 or more types of combined use.
In addition, for this receiving layer, an ink fixing agent, a dispersing agent, a cross-linking agent, a thickener, an antifoaming agent, an antistatic agent, an antiseptic, an ultraviolet absorber, a preservability improving agent, and a fluorescent whitening agent as necessary. , And various additives such as a colorant can be appropriately added.

  The above-mentioned ink fixing agent is for fixing the dye of the dye ink in the ink receiving layer in the same manner as that provided in the undercoat layer, in order to obtain good dye ink color developability, storage stability and ink absorption. In addition, the same ink fixing agent as that used in the undercoat layer is used.

  Furthermore, it is preferable to add a surfactant derived from acetylene alcohol or acetylene glycol to the ink receiving layer. By using these surfactants, the antifoaming effect of the paint and the effect as a wetting agent can be expected to be high.

[Method for producing ink receiving layer]
The ink receiving layer is produced by applying an ink receiving layer coating liquid comprising the above-described components onto the undercoat layer.
The dry coating amount of the ink receiving layer is preferably 5 to ²⁰ g / m ² .
If the dry coating amount is less than 5 g / m ² , the gloss and ink absorbency are not sufficient, and if it exceeds 20 g / m ² , cracks in the coating layer tend to occur and good dot trueness is obtained. Circularity is difficult to obtain, and the printing density of pigment ink and dye ink is insufficient.
The solid content concentration of the ink receiving layer coating liquid is preferably 5 to 50% by mass, and more preferably 5 to 20% by mass.
When the solid content concentration is less than 5% by mass, the drying efficiency of the ink receiving layer is low, and when it exceeds 50% by mass, the coating layer is liable to crack.
As a coating method of the ink receiving layer coating liquid, there is a coating method in which coating is performed using any of various known and publicly known coating apparatuses such as sprays in addition to the above-described coating apparatus used for the undercoat layer. Can be mentioned.

In order to prevent cracking of the ink-receiving layer, a cross-linking agent that cross-links the adhesive of the undercoat layer and the adhesive of the ink-receiving layer, or a gelling agent that cross-links and gels the adhesive. It is preferred to use to crosslink the adhesive.
Are these cross-linking agents (including gelling agents) added to the ink receiving layer coating liquid, or are they preliminarily applied to the surface of the undercoat layer before applying the ink receiving layer as an aqueous coating liquid? Alternatively, the ink receiving layer is used after being coated on the surface thereof.
Examples of the cross-linking agent include aldehyde-based cross-linking agents such as glyoxal which is a compound having a cross-linking property to polyvinyl alcohol, epoxy-based cross-linking agents such as ethylene glycol diglycidyl ether, and vinyl-based cross-linking agents such as bisvinylsulfonylmethyl ether. Examples of the gelling agent that crosslinks polyvinyl alcohol and gels include boron-containing compounds such as boric acid and borax, zirconium compounds, aluminum compounds, and chromium compounds.
In the present embodiment, among these, a boron-containing compound that is a gelling agent is particularly preferably used because thickening or gelation occurs quickly.

Here, the boron-containing compound is an oxygen acid having a boron atom as a central atom and a salt thereof. Specific examples include orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid, and Their sodium, potassium and ammonium salts are mentioned.
Of these, orthoboric acid and disodium tetraborate are preferably used because they have an effect of increasing the viscosity of the coating solution to an appropriate degree.
The compounding amount of the boron-containing compound depends on the kind of the boron-containing compound and the degree of polymerization of polyvinyl alcohol, and is 0.01 to 2.0 g / m ² as a dry coating amount on either the undercoat layer or the ink receiving layer. It is preferably contained.
When the coating amount of this boron-containing compound is less than 0.01 g / m ² , the crosslinking property with the hydrophilic adhesive and the gelation of the coating solution are not sufficient, and cracks occur in the coating layer. End up. Even if the blending amount exceeds 2.0 g / m ² , the high crosslinking density with the adhesive is saturated, and the crack preventing effect of the coating layer is not further improved, which is not effective.

<Outermost layer>
In the glossy ink jet recording paper of the present embodiment, the outermost layer containing the above-described colloidal particles as the pigment and the polyoxylene group-containing polyvinyl alcohol resin as the binder is formed on the surface of the ink receiving layer. Yes.
This outermost layer is formed by preparing a coating liquid containing the above components and coating it on the surface of the ink receiving layer. While the coating liquid is in a wet state or in a dry state, The glossy surface is formed by various glossing processes.
In consideration of providing high gloss and excellent ink jet recording suitability, the glossing process employs a cast method and film transfer method (hereinafter referred to as “cast processing”) that uses a mirror drum, which will be described later. It is preferable to do.

[Colloidal particles]
As the colloidal particles as pigments contained in the outermost layer, for example, colloidal particles of fine pigments exemplified in the ink receiving layer can be used, and specifically, gas phase method silica, mesoporous silica, and activated silica are used. At least one selected from colloidal silica, alumina, and alumina hydrate of wet-process silica produced by condensing an acid is selected. Of these, colloidal silica, particularly colloidal silica composed of vapor-phase process silica, and alumina are preferable because excellent gloss can be obtained.

The form of the colloidal particles may be a single particle dispersion or an aggregated particle dispersion. However, in order to obtain a high printing density and high gloss on the outermost layer, the colloidal particles are mainly single particle dispersion or aggregated. Among the particle dispersions, those having a small particle diameter are preferably used. For example, when colloidal silica is used as the single particle dispersion, the average particle diameter is 3 nm to 200 nm, preferably 5 nm to 90 nm. When the average particle diameter is less than 3 nm, the ink absorptivity decreases, and when the average particle diameter exceeds 200 nm, the glossiness and the print density decrease.
The colloidal silica is preferably cationic.
When a single particle dispersion is used, a true spherical pigment is preferable.

[Polyoxylene group-containing polyvinyl alcohol]
The polyoxylene group-containing polyvinyl alcohol as a binder can be obtained by saponifying a copolymer of an unsaturated monomer containing an oxyalkylene group and a vinyl ester compound. Examples of unsaturated monomers having an oxyalkylene group include those of the (meth) acrylic acid ester type, but the present invention is not limited to these.
The oxyalkylene group-containing polyvinyl alcohol used in the present embodiment preferably contains 0.2 to 30 mol% of oxyalkylene groups.
If the amount is less than 0.2 mol%, the ink acceptability tends to decrease or the ink tends to bleed.
Conversely, when it exceeds 30 mol%, the weather resistance and water resistance tend to decrease.
Further, the saponification degree of the oxyalkylene group-containing polyvinyl alcohol is not particularly limited, but is preferably 50 mol% or more. If it is less than 50 mol%, the ink acceptability and the weather resistance tend to decrease, which is not preferable.
The average degree of polymerization is not particularly limited, but is preferably 50 to 3000, and particularly preferably 1000 to 2500. If the average degree of polymerization is less than 50, the film-forming property is poor, and stickiness or the like remains on the surface of the coated recording sheet. However, if it exceeds 3000, the viscosity of the coating liquid at the time of coating is improved and there is a problem in operability.

[Production method of outermost layer]
The coating liquid is prepared by adding colloidal particles and a polyoxylene group-containing polyvinyl alcohol resin in an aqueous solvent.
The blending amount of the colloidal particles and the polyoxylene group-containing polyvinyl alcohol resin is 1 to 30 parts by mass, preferably 1 to 10 parts by mass of the polyoxylene group-containing polyvinyl alcohol resin with respect to 100 parts by mass of the colloidal particles. Adjusted within range.
When the blending amount is less than 1 part by mass, the scratch resistance of the pigment ink is lowered, and when it exceeds 30 parts by mass, the voids in the ink receiving layer are closed and the ink absorbability is deteriorated.

In the outermost layer, if necessary, another adhesive as a binder may be used in combination.
The adhesive used together is added to the outermost layer coating solution and applied.
As the adhesive used in combination, a known adhesive used for inkjet recording paper, that is, the same adhesive as the above-described adhesive used for the undercoat layer is used.
And the adhesive agent selected and used together from these may be individual, or may be 2 or more types.
In addition, when an ink fixing agent is blended in the outermost layer coating solution, the adhesive is particularly preferably cationically modified.

  In addition, the outermost layer is provided with an ink fixing agent, a dispersant, a crosslinking agent, a thickener, an antifoaming agent, an antistatic agent, an antiseptic, an ultraviolet absorber, a storage stability improving agent, and a fluorescent whitening agent as necessary. , And various additives such as a colorant can be appropriately added.

  As the ink fixing agent, the same ink fixing agent as that used for the undercoat layer is used.

  Thickeners and flow modifiers include synthetic resin latex such as styrene-butadiene copolymer latex and methyl methacrylate-butadiene copolymer latex, proteins such as casein, soy protein, synthetic protein, starch and oxidized starch. Various starches, polyvinyl alcohol, cellulose derivatives such as carboxymethyl cellulose and methyl cellulose, polycarboxylic acid, polyacrylic acid, acrylic emulsion, polyamide, polyester, alkali thickening type and nonionic surfactant are suitably used.

  Examples of water-proofing agents and printing suitability improvers include sodium chloride, ammonium chloride, zinc chloride, magnesium chloride, sodium sulfate, potassium sulfate, ammonium sulfate, zinc sulfate, magnesium sulfate, ferrous sulfate, sodium nitrate, ammonium nitrate, first Sodium phosphate, ammonium phosphate, calcium phosphate, sodium polyphosphate, sodium hexametaphosphate, sodium formate, ammonium formate, sodium acetate, potassium acetate, sodium monochloroacetate, sodium malonate, sodium tartrate, potassium tartrate, potassium citrate, Ammonium and metal salts of inorganic and organic acids such as sodium lactate, sodium gluconate, sodium adipate, sodium dioctylsulfosuccinate and sodium aluminate, Amines such as amine, diethanolamine, diethylenetriamine, diisopropylamine, triethanolamine, ethanolamine, ethanolamine, phosphate ester, polyoxyethylene alkylphenol ether phosphate ester salt, polyoxyethylene ether phosphate ester salt, alkylphenol ether phosphate Phosphate esters such as ester salts, polyoxyethylene, alkyl ether, polyoxyethylene and ammonia water, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether and diglycidyl adipate Polyfunctional epoxy compounds such as esters, urea-formaldehyde, polyamide-epoxy Rohidorin system, glyoxal and the like are used as appropriate.

The various additives are added to the outermost layer coating solution in the range of 0.05 to 10% by mass, preferably 0.1 to 5% by mass as the solid content concentration.
Furthermore, various auxiliary agents such as a dispersant, an antifoaming agent, a colorant, a fluorescent dye, an antistatic agent, and a preservative can be appropriately added to the outermost layer coating solution.
In addition, pigments such as alumina, colloidal silica, fine silica, clay, and calcium carbonate can be added as other auxiliary agents.
In addition, when performing the rewetting process mentioned later, you may add these adjuvants to the wetting liquid used for a rewetting process except a pigment.

[Glossing treatment]
The outermost layer is formed on the glossy surface by a glossing process which is a cast process .
Glossing process, in order to impart the ink jet recording suitability and excellent high gloss, performed by a cast method or a film transfer method using a mirror surface drum.

In general, cast processing means that a coating layer is dried on a smooth cast drum (mirror finish metal, plastic, glass, etc.), mirror finish metal plate, plastic sheet or film, glass plate, By copying these smooth surfaces onto the coating layer, a smooth and glossy coating layer surface is obtained.
The method of obtaining a glossy surface by casting using a mirror drum heated in this,
(A) Apply the above-mentioned coating layer coating solution on a support or undercoat layer, press it against a heated mirror drum while the coating layer is in a wet state, and dry to finish. Method (wet cast method),
(B) Once the coating layer has been dried, the coating layer is rewet and pressed onto a heated mirror drum and dried to finish (rewet casting method),
(C) A method in which a gel-like coating layer obtained by gelling a coating layer is pressed against a heated mirror drum and dried to finish (gel-casting method),
(D) A method in which an upper layer coating solution is directly applied to a heated mirror drum without forming a coating layer on the support, and then pressed and dried on the support or the undercoat layer (precast Law).
In these casting processes, the temperature of the heated mirror drum is, for example, 50 to 150 ° C, preferably 70 to 120 ° C.

Furthermore, as another casting process, a film transfer method can also be adopted.
As a film transfer system,
(A) The above coating layer coating solution is applied onto a support or an undercoat layer, and a smooth film or sheet is stacked while the coating layer is in a wet state, dried and then smooth. How to peel and finish films and sheets,
(B) Applying the coating solution onto a smooth film or sheet, while the coating layer (recording layer) or the surface of the support or undercoat layer to be bonded is in a certain wet state, After pressing and drying, a method to peel off and finish a smooth film or sheet,
There is.

Compared with the film transfer method, the cast method using a heated mirror drum tends to be superior in surface smoothness, and is often advantageous in terms of productivity and cost.
In the above-described casting process, in the casting process using a heated mirror drum, the wet casting method can easily form a uniform coating layer, can increase the printing density, and can obtain an upper layer with excellent gloss. This is particularly preferable because it can be performed.

In the cast processing, the coating amount of the outermost layer coating solution is preferably 0.1 to 30 g / m ² in terms of dry solid content.
If it is less than 0.1 g / m ² , the print density and gloss may not be sufficient, and if it exceeds 30 g / m ² , the effect is almost saturated. There is a risk of lowering.

  As the coating method of the outermost layer coating liquid in each of the above-described casting processes, for example, using any of various known coating apparatuses such as a blade coater, a brush coater, a champex coater, a bar coater, and a gravure coater. The coating method to apply can be used.

In performing the casting treatment, it is preferable to use a release agent in order to smoothly peel off the outermost layer from the cast drum or the like.
The mold release agent can be used by any one of a method of adding to the outermost layer coating solution, a method of applying to the surface of a cast drum, and a method of adding to the wetting solution.
Examples of the release agent include higher fatty acid amides such as stearic acid amide and oleic acid amide, polyolefin waxes such as polyethylene wax, polyethylene oxide wax, and polypropylene wax, calcium stearate, zinc stearate, potassium oleate, and oleic acid. Examples include higher fatty acid alkali salts such as ammonium, silicone compounds such as lecithin, silicone oil, and silicone wax, and fluorine compounds such as polytetrafluoroethylene. Among these, a cationic release agent is particularly preferably used.

Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.
Further, “parts” and “%” are solid contents excluding water unless otherwise specified, and indicate mass parts and mass%, respectively.

Example 1
<Preparation of paper support>
100 parts of wood pulp (LBKP: freeness of 440 ml CSF), 15 parts of filler (ratio of calcium carbonate 3: talc 1), 0.05 part of commercial sizing agent (trade name: Fibran 81K, manufactured by NSC Japan), sulfuric acid Using a papermaking material consisting of 0.45 parts of band, 0.45 parts of starch, 0.4 parts of polyamide / epichlorohydrin resin (paper strength enhancer) and a little yield improver, basis weight 188g / After obtaining a paper substrate of m ^2, a supercalender treatment was performed at a linear pressure of 150 kg / cm to produce a paper support as a support. The obtained paper support had a thickness of 210 μm and an air permeability of 30 seconds.

<Preparation of undercoat layer>
(Preparation of coating solution for undercoat layer)
Synthetic amorphous silica as a pigment (trade name: Fine Seal X-45, manufactured by Tokuyama, secondary particles having an average particle size of 4.5 μm), silyl-modified polyvinyl alcohol as a binder (trade name: R1130, manufactured by Kuraray Co., Ltd.) ) 80 parts, fluorescent dye (trade name: Whitetex BPS (H), manufactured by Sumitomo Chemical Co., Ltd.), diallyldimethylammonium chloride polymer (trade name: Unisense CP-102, manufactured by Senka Co., Ltd., cationic) Compound) 5 parts were mixed to prepare an undercoat layer coating solution having a solid content of 15%.

[Preparation of ink receiving layer coating solution]
Using commercially available gas phase method silica (trade name: Leorosil QS-30, manufactured by Tokuyama Corporation, primary particle average particle size 9 nm, specific surface area 300 m ² / g) as a pigment, repeated crushing and dispersion with a high-speed flow collision type homogenizer Secondary particles were classified, and a 10% silica dispersion having an average particle diameter of 200 nm after classification was prepared.
To this silica dispersion, 10 parts of a cationic polymer compound having a five-membered ring amidine structure (trade name: SC-700M, manufactured by Hymo Co., Ltd., molecular weight 30,000) is added, and further dispersed with a high-speed collision type homogenizer. A 10% cationic polymer compound-silica composite particle dispersion having an average particle size of 0.15 μm and secondary particles was prepared.
15 parts of polyvinyl alcohol (trade name: PVA145, manufactured by Kuraray Co., Ltd., degree of polymerization 4500) as a binder was mixed with 100 parts of the dispersion (in solid content) to prepare an ink receiving layer coating solution.

[Adjustment of outermost layer coating solution]
Cationic colloidal silica (trade name: Snowtex AK-L, Nissan Chemical Industries, Ltd. 100 parts (colloidal particles)) having an average particle size of 0.03 μm as a pigment, and polyoxylene group-containing polyvinyl alcohol (trade name: Ecomati WO320R) as a binder ) 2.5 parts and 1 part of polyethylene wax (nonionic) as a release agent were mixed to prepare a coating solution for the outermost layer having a solid content concentration of 15%.

[Preparation of inkjet recording paper]
The prepared undercoat coating liquid was applied onto the paper support thus prepared to prepare an undercoat layer.
After that, apply an aqueous borax solution and a separately prepared coating solution for the ink receiving layer on the undercoat layer in order, dry, apply the outermost layer coating solution, and perform a wet cast finish to obtain a glossy inkjet recording paper. It was.

(Example 2)
A glossy inkjet recording paper was obtained in the same manner as in Example 1 except that 2.5 parts of polyvinyl alcohol (trade name: PVA245, manufactured by Kuraray Co., Ltd.) was added as a binder to the outermost layer coating solution of Example 1.

(Example 3)
A glossy ink jet recording paper was obtained in the same manner as in Example 1 except that the undercoat layer of Example 1 was not applied.

(Comparative Example 1)
Cationic colloidal silica (trade name: Snowtex AK-L, manufactured by Nissan Chemical Industries, Ltd. (colloidal particles)) having an average particle size of 0.03 μm as a pigment, and polyvinyl alcohol (trade name: PVA245, manufactured by Kuraray Co., Ltd.) as a binder. ) Glossy inkjet recording paper as in Example 1 except that 2.5 parts and 1 part of polyethylene wax (nonionic) as a release agent were mixed and the outermost layer coating solution having a solid content of 15% was prepared. Got.

(Comparative Example 2)
The prepared undercoat coating solution is applied onto the prepared paper support, and then the outermost layer coating solution described in Example 1 prepared separately is applied to perform wet casting, and gloss inkjet recording. Got the paper.

(Evaluation method and evaluation criteria)
With respect to the glossy inkjet recording paper obtained in the above Examples and Comparative Examples, the printability and glossiness in inkjet recording were evaluated by the following methods.

[Printability in inkjet recording]
Evaluation of printing suitability is performed using both dye ink and pigment ink type printers, printing density, ink absorptivity, glossiness of printed parts, glossiness, surface strength, printer transportability, ink aggregation unevenness, and Evaluation was performed according to each item of head rubbing.

Evaluation printer Printer A: Commercially available dye ink type ink jet printer (trade name: PM-G800, manufactured by Seiko Epson Corporation)
Printer B: Commercially available pigment ink type ink jet printer (trade name: PM-G900, manufactured by Seiko Epson Corporation)

Printing density Black solid printing was performed using printer A (dye ink type) and printer B (pigment ink type), and the printing density was measured with an X-light reflection densitometer (938 spectrodensitometer).

・ Ink absorbability Using printer A (dye ink type), black, cyan, magenta, yellow, red, green, and blue solid colors are printed in a grid pattern so as to touch each other. The ink bleeding at the boundary between them was visually evaluated according to the following criteria.
(Double-circle): The blur of printing is not recognized at all and it is an excellent level.
○: Slight bleeding is observed, but there is no practical problem.
Δ: Slightly blurring of printing and slightly problematic in practical use.
X: The level at which printing blur is remarkable and becomes a serious problem in practical use.

・ Glossiness of printed part Using a printer A (dye ink type), a photographic image (JIS X 9204 compliant “high-definition color digital standard image (XYZ / SCID) data”), image identification code: N1, image name: Glass and female) were printed, and the uniformity of the printed part was visually evaluated according to the following criteria.
A: Excellent level with no unevenness in printed gloss on the entire image.
○: The print glossiness is slightly lower at the dark print color development, but it does not cause a problem overall.
×: Level at which printing gloss partially disappears and becomes a serious problem in practical use.

[Glossiness]
Glossiness was evaluated by visually observing glossiness and smoothness from the lateral direction with respect to the surface of the blank recording paper according to the following criteria.
A: Extremely high gloss.
○: Glossy.
X: The glossiness is inferior.

[Surface strength]
The friction tester (Gakuken type) described in JIS-L-0849 sets the mass of the friction element to 400 g, and attaches the test piece to the tip of the friction element and the test piece table with the ink receiving layer facing each other. The space was rubbed back and forth 10 times, and was evaluated from the presence or absence of the outermost surface drop and the degree of paper dust generation.
(Evaluation criteria)
○: Good △: Slightly inferior ×: Impractical

[Transportability]
Using printer A, solid printing was performed continuously to evaluate the conveyance status.
○: Good △: Slightly inferior ×: Impractical

[Ink aggregation unevenness]
Using printer B, solid printing was performed, and the degree of uneven printing was visually evaluated.
○: Good △: Slightly inferior ×: Impractical

[Head rubbing]
Using printer A, solid printing was performed, and the degree of printing failure due to head rubbing was visually evaluated.
○: Good △: Slightly inferior ×: Impractical

  The results are shown in Table 1.

As is clear from the results shown in Table 1, in Examples 1 to 3 according to the present invention, all of the above evaluation items are good, and particularly excellent in ink absorbency, glossiness of printed portions, and glossiness. ing.
On the other hand, Comparative Example 1 is slightly inferior in surface strength and transportability, and Comparative Example 2 is not practical in terms of gloss and is not satisfactory in almost all evaluation items.

Claims (6)

An ink receiving layer containing amorphous silica, which is a secondary particle having an average particle diameter of 90 to 700 nm , formed on a support and containing a binder that holds the silica, and a pigment on the ink receiving layer are formed on, containing colloidal particles as a pigment, and has a top surface layer containing a polyoxyalkylene group-containing polyvinyl alcohol as a binder to hold it, gloss the outermost layer, the glossing process is cast machining A glossy ink jet recording paper characterized by having a surface. The composition ratio between the colloidal particles contained in the outermost layer and the polyoxylene group-containing polyvinyl alcohol is 1 to 30 parts by mass of the polyoxylene group-containing polyvinyl alcohol with respect to 100 parts by mass of the colloidal particles. The glossy ink jet recording paper according to claim 1. The colloidal particles are cationic colloidal silica;
The glossy ink jet recording paper according to claim 2. 4. The glossy ink jet recording paper according to claim 1, wherein the colloidal particles are made of colloidal silica of a single particle dispersion and have an average particle diameter of 3 to 200 nm. 2. The glossy ink jet recording paper according to claim 1, wherein the casting is a wet casting method. The glossy ink jet recording paper according to any one of claims 1 to 5, wherein the ink receiving layer is provided via an undercoat layer containing a pigment and an adhesive provided on the support.