JP4380626B2 - Glossy inkjet recording paper manufacturing method - Google Patents

Description

  The present invention relates to an ink jet recording paper, and more particularly to an ink jet recording paper having excellent suitability for printing by an ink jet printer and particularly excellent glossiness of a blank paper portion and a printing portion.

Inkjet printer printing has been used in many fields in recent years because it has low noise, enables high-speed printing, and can easily increase the number of colors.
As ink jet recording paper used for printing by such an ink jet printer, high-quality paper devised to be rich in ink absorbability, coated paper coated with a porous pigment on the surface, and the like are generally used. .
By the way, these papers mainly have a so-called matte tone with a low surface glossiness, but with the recent progress in printer technology, high-quality printing comparable to silver halide photography has become possible. Therefore, development of ink jet recording paper having high surface glossiness and excellent appearance that can cope with this printer technology is expected.

In general, for paper with a high surface glossiness, a plate-like pigment is applied to the surface of the paper substrate, and if necessary, the coated paper is made highly glossy by calendering, and the wet coating layer is mirror-finished. A so-called cast coated paper is known in which a heated drum surface is pressed and dried, and its mirror surface is transferred to a coating layer to make it highly glossy.
This cast coated paper has high surface gloss and superior surface smoothness compared to super calendered coated paper, and has excellent printing effects. It's being used.

Regarding such cast-coated paper, a coating layer comprising a pigment and an adhesive as main components on a base paper, a polymer obtained by polymerizing a monomer having an ethylenically unsaturated bond in the coating layer, and There is known a production method for obtaining cast coated paper by applying a rewetting liquid containing an average particle size of 5 to 100 nm colloidal silica and a release agent (Patent Document 1 and Patent Document 2).
In this manufacturing method, a film-forming substance such as an adhesive in the coating layer has a high gloss obtained by copying the mirror drum surface of the cast coater. The porosity of the ink is lost, and the ink absorption during ink jet printing is extremely reduced.

In order to solve this problem and improve the ink absorbability of recording paper, it is important to make the coating layer porous so that the ink can be easily absorbed, and it is therefore necessary to reduce the film formability. It becomes.
However, when the amount of the film-forming substance is reduced, another problem arises that the glossiness of the recording paper is lowered.
As described above, it has been extremely difficult to achieve both the surface gloss of cast coated paper and ink jet printing suitability.

  As a technique for solving this drawback, a copolymer having a glass transition point of 40 ° C. or higher obtained by polymerizing a monomer having an ethylenically unsaturated bond on a base paper provided with a recording layer mainly composed of a pigment and an adhesive. By forming a cast coating layer by applying a coating solution containing the coalescence as the main component, and pressing and drying to a heated mirror drum while the cast coating layer is in a wet state, it is excellent. It is known that cast coated paper for ink jet recording having both high gloss and ink absorbability can be obtained (Patent Document 3).

  However, in recent years, with the expansion of applications such as high-speed inkjet printing, high-definition printed images, and full color, there has been a demand for higher gloss, higher image quality, and higher print density. However, the cast coated paper does not satisfy such requirements sufficiently. On the other hand, dye-based inks have traditionally been the mainstream for printing with full-color inks, but pigment-based inks have recently been used. Therefore, a recording medium capable of giving a high-resolution recording image to both of these inks is desired.

As a technique for improving the recording quality, surface coating for ink jet recording paper comprising a polymer emulsion having an average particle diameter of 0.02 to 0.15 μm and colloidal silica having an average particle diameter of 0.01 to 0.15 μm. Agents are known (Patent Document 4).
Further, as a technique for further improving this point, a polymer emulsion having an average particle diameter of 0.02 to 0.15 μm and colloidal silica having an average particle diameter of 0.01 to 0.15 μm are coated on the surface layer and cast. By forming a coating layer for coating, and immediately pressing the coated layer for casting onto a heated mirror drum and drying and finishing, the gloss of the blank portion and the printed portion, print density, ink absorbency, A technique for obtaining a cast coated paper for ink jet recording excellent in recording image quality is known (Patent Document 5).
In these methods, although ink jet recording paper having gloss and recording image quality superior to those of the conventional methods can be obtained, further improvements in recording image quality and the like have been demanded with the technical progress of the ink jet printer described above. is there.

An ink jet recording paper having a layer containing an anionic colloidal silica treated with a coupling agent and a polymer as a binder is known as a paper answering this demand (Patent Document 6).
Although this paper is an ink jet recording paper excellent in ink jet recording suitability such as glossiness and print density of the white paper portion and the print portion, ink absorbability, there is a problem that drum stains occur when manufacturing this paper, It was not enough in terms of operability.

JP-A-5-59688 Japanese Patent Laid-Open No. 5-78995 JP 7-89220 A JP 2000-238418 A JP 2000-238419 A Japanese Patent Laid-Open No. 2005-1377

The present invention has been made in view of the above circumstances, and as a result of intensive studies to solve the above problems, the present inventors have conducted anionic colloidal silica that has been subjected to a coupling treatment on a coating layer of a substrate. And cationic colloidal silica, it has recording quality comparable to photographic printing paper as inkjet recording paper, and is suitable for both dye-based inks and pigment-based inks. The present inventors have developed a method for producing glossy ink jet recording paper that does not cause contamination of drums and the like, and have reached the present invention.
The technical problem to be solved by the present invention is that it has excellent ink jet printing suitability in glossiness, printing density, ink absorptivity, recording image quality, printing rubbing property, etc. of a blank paper portion and a printing portion, and a dye-based ink and pigment It is an object of the present invention to provide a glossy ink jet recording paper having ink jet suitability with both of the system inks and having excellent operability during production.

The present invention relates to a glossy inkjet recording paper having a base material and at least two coating layers formed on the base material, and a cationic compound as an ink fixing agent is provided in at least the lower layer of the coating layers. And at least a surface layer of the coating layer contains, as a pigment, an anionic colloidal silica subjected to a coupling treatment and a cationic colloidal silica in a solid content weight ratio of 1/99 to 30/70 , and cast. A glossy inkjet recording paper manufacturing method, characterized in that the glossy treatment is performed by processing .

  According to the preferable structure aspect of this invention, the coupling agent used for the said coupling process is a silane coupling agent.

  According to another preferred embodiment of the present invention, the coating layer contains a polymer as a pigment binder.

The method for producing the glossy ink jet recording paper of the present invention has an inkjet printability excellent in gloss, print density, ink absorbency, recording image quality, print scratching, etc. of the blank paper portion and the print portion using the method , In addition, it is a method for producing glossy ink jet recording paper that has ink jet printing suitability for both dye-based inks and pigment-based inks, and is also excellent in operability at the time of production .

The manufacturing method of the glossy ink jet recording paper of the present invention will be described in more detail based on the following embodiments.
Ink-jet recording sheet of the present embodiment includes a substrate, and at least two layers coated layer of the formed on the substrate, at least the lower layer of the coating layer, Kachio in as an ink fixing agent And at least the surface layer of the coating layer contains, as a pigment, a coupled anionic colloidal silica and a cationic colloidal silica in a solid content weight ratio of 1/99 to 30/70. is doing.
Furthermore, the base material having the surface layer, into force the glossing process by the casting process, the surface layer is an excellent glossy surface.

<Surface>
The coupling treatment is performed by adding a coupling agent to anionic colloidal silica.
The anionic colloidal silica is a colloidal solution in which spherical silica is dispersed in water. The silanol group formed on the particle surface is negatively charged, and a base such as sodium hydroxide, sodium silicate, or organic amine is used. By adding, a stable anionic property is exhibited.
In the present embodiment, the cationic colloidal silica is not subjected to a coupling treatment, but the coupling treatment to the cationic colloidal silica is optional.

[Coupling treatment]
As such anionic colloidal silica, commercially available products can be used. For example, in terms of trade names, silica dol (manufactured by Nippon Chemical Industry Co., Ltd.), Adelite AT (Asahi Denka Kogyo Co., Ltd.) Product), Cataloid (manufactured by Catalyst Kasei Kogyo Co., Ltd.), Snowtex (manufactured by Nissan Chemical Industries, Ltd.), and the like.
Of these anionic colloidal silicas, a sol-like aqueous dispersion having a pH of 8 to 12 and a weight concentration of 20 to 50% is preferred from the viewpoint of compatibility with the copolymer emulsion of the binder.
The average particle diameter of the anionic colloidal silica is not particularly limited, but is preferably 0.01 to 0.15 μm, more preferably 0.02 to 0.12 μm.
If the average particle size is less than 0.01 μm, the ink absorbability may be lowered, and if it exceeds 0.15 μm, the sharpness of the recorded image may be lowered.

The coupling agent is not particularly limited, and various known coupling agents can be used. From the viewpoint of excellent reactivity with the anionic colloidal silica, a silane coupling agent. Is preferably used.
Examples of the silane coupling agent include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropylmethyldichlorosilane, γ-chloropropylmethyldimethoxysilane, γ- Chloropropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, γ -Mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysila For example.
These may be used alone or in combination of two or more.

In the present embodiment, the anionic colloidal silica treated with a coupling agent usually refers to a product obtained by adding a coupling agent to anionic colloidal silica.
As a specific coupling treatment method, for example,
(A) A method in which anionic colloidal silica is heated to 40 to 95 ° C., particularly about 70 ° C., and a coupling agent is continuously dropped onto the anionic colloidal silica,
(B) A method in which anionic colloidal silica and a coupling agent are charged at room temperature, mixed, and then reacted by heating to the above temperature;
(C) A method in which a coupling agent is dropped onto anionic colloidal silica under reduced pressure.
(2) A method in which a coupling agent and an alkali catalyst are dropped simultaneously on anionic colloidal silica,
(E) A method in which a coupling agent and an acid catalyst are simultaneously dropped onto anionic colloidal silica,
(F) A method of supplying this solution to a reaction system containing anionic colloidal silica in a state where the coupling agent is dissolved in a solvent,
(G) A method of supplying this solution to a reaction system containing anionic colloidal silica in a state where a coupling agent is emulsified with an emulsifier,
Among them, the methods (a) and (b) are preferable.

When anionic colloidal silica is treated with a silane coupling agent, the amount of the silane coupling agent used is, for example, the addition amount of the silane coupling agent with respect to the effective amount of SiO _{2 in} the colloidal silica. 0.01 to 20% by mass, preferably 0.02 to 10% by mass, and more preferably 0.05 to 5.0% by mass.
If the addition amount is less than 0.01% by mass, sufficient dispersion stability improvement effect cannot be obtained, and at the same time, the suitability of the pigment ink may be insufficient, and if it exceeds 20% by mass, the dispersion stability may decrease. There is.

The cationic colloidal silica contained in at least the surface layer of the ink jet recording paper of the present embodiment is preferably primary particles having an average particle diameter of 3 to 100 nm, and particularly preferably 10 to 80 nm from the viewpoint of easy glossiness. More preferred.
As for the shape, a spherical pigment is preferable in terms of ease of glossiness, but non-spherical colloidal silica is superior in ink absorptivity, and either one is used according to the purpose, or both are used. It can be used by mixing appropriately.

An anionic colloidal silica treated with a coupling agent in the production method of the present invention, the composition ratio of the cationic colloidal silica is 30/70 1/99 by solids weight ratio, more preferably, 1/99 In the range of 10/90.
When the amount of the anionic colloidal silica added is less than 1, the releasability from the cast drum is poor at the time of production, and when it exceeds 30, the coating solution is not stable, the viscosity increases, and aggregates are formed in the coating solution. Or the like, and the glossiness of the coating layer may be reduced.

(Polymer)
The polymer as a binder of the pigment contained in at least the surface layer of the ink jet recording paper of the present embodiment is not particularly limited, but various adhesives generally used in the coated paper field are used.
As these adhesives, for example,
A: As a water-soluble polymer,
(A) polyvinyl alcohols containing modified polyvinyl alcohols such as polyvinyl alcohol, cation-modified polyvinyl alcohol, silyl-modified polyvinyl alcohol,
(B) Casein, soybean protein, synthetic proteins, starch and modified products thereof, natural polymers such as gelatin and modified products thereof, or synthetic products and modified products thereof,
(C) Natural polymer resins such as pullulan, gum arabic, karaya gum, albumin or their derivatives,
(2) Cellulose derivatives B such as carboxymethylcellulose, methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose, hydroxyethylcellulose, etc .:
(Meth) acrylic acid ester polymers or copolymers, ethylene-vinyl acetate copolymers, styrene-butadiene copolymers, conjugated diene polymers such as methyl methacrylate-butadiene copolymers, ethylene-vinyl acetate Vinyl copolymers such as copolymers,
C: As other synthetic resins,
Water-based acrylic resin, water-based polyurethane resin, water-based polyester resin, SBR latex, NBR latex,
Etc.
These may be used alone or in combination of two or more.

In addition to the anionic colloidal silica treated with the coupling agent and the cationic colloidal silica, other pigments can be used in combination on the surface layer.
As such a pigment, amorphous silica other than the above-mentioned colloidal silica, aluminum oxide, zeolite, synthetic smectite, and the like are preferable from the viewpoint of enhancing glossiness, transparency, and ink absorbability.
The average particle diameter of these pigments is preferably from 0.01 to 5 μm, more preferably from 0.05 to 1 μm. If the average particle diameter is less than 0.01 μm, the ink absorbability may not always be sufficient, and if it exceeds 5 μm, the glossiness and the print density may be reduced.
In particular, when silica fine particles, which are amorphous silica and have an average primary particle diameter of 3 to 40 nm and an average secondary particle diameter of 10 to 300 nm, are used for glossiness and ink absorption. It will be extremely excellent.

  Furthermore, the coating liquid used to form the coating layer constituting the surface layer is used for general printing coating liquids and inkjet papers in order to adjust whiteness, viscosity, fluidity, and the like. Various auxiliary agents such as an antifoaming agent, a coloring agent, a fluorescent brightening agent, an antistatic agent, an antiseptic, a dispersing agent, and a thickening agent can be appropriately added.

[Casting]
In the formation of the surface layer, cast processing such as a cast method using a heated mirror drum, which will be described later, or a film transfer method is performed.
In such a casting process, a release agent can be used for the purpose of imparting releasability from a cast drum or film.
As the mold release agent, a mold release agent used in the production of ordinary printing coated paper or printing cast coated paper can be used.
Specific examples of such release agents include polyolefin waxes such as polyethylene wax and polypropylene wax, higher fatty acid alkali salts such as calcium stearate, zinc stearate, potassium oleate, and ammonium oleate, silicone oil, and silicone. Examples thereof include silicone compounds such as wax, fluorine compounds such as polytetrafluoroethylene, lecithin, and higher fatty acid amides. From the viewpoint of operational stability, it is desirable to use nonionic polyethylene wax.
This release agent is used by being added to the coating solution.

<Base material>
The base material of the inkjet recording paper of the present embodiment is not particularly limited, and paper base materials such as acid paper or neutral paper used for general coated paper, various synthetic resin films and sheets, and laminates Paper or the like is used as appropriate.
However, when adopting a cast method or a film transfer method, which will be described later, in the formation of the surface layer, it is particularly preferable to use a gas-permeable substrate, and a paper substrate or a gas-permeable resin film and sheets are used.

The paper base is composed mainly of wood pulp and filler blended as necessary.
As the wood pulp, various chemical pulps, mechanical pulps, regenerated pulps and the like can be used, and these pulps have a beating degree adjusted to adjust paper strength, papermaking suitability, and the like.
Here, the beating degree (freeness) of the pulp is not particularly limited, but is generally about 250 to 550 ml (CSF: JIS-P-8121).
Further, chlorine-free pulps such as so-called ECF pulp and TCF pulp can be preferably used.
The filler to be blended as necessary is blended for the purpose of imparting opacity or adjusting the ink absorbability, and uses, for example, calcium carbonate, calcined kaolin, silica, titanium oxide and the like. be able to.
In this case, about 1-20 mass% is preferable with respect to the whole paper base material. If the amount is too large, the paper strength may decrease.
In addition, a sizing agent, a fixing agent, a paper strength enhancer, a cationizing agent, a yield improving agent, a dye, a fluorescent brightening agent, and the like can be added as an auxiliary agent.

In the size press process of the paper machine, the paper base material can be coated and impregnated with starch, polyvinyl alcohol, cationic resin, etc., and the surface strength, sizing degree, etc. can be adjusted.
In this case, the sizing degree is preferably about 1 to 400 seconds. If the sizing degree is less than 1 second, wrinkles may occur at the time of coating, which may cause operational problems. On the other hand, if the sizing degree exceeds 400 seconds, the ink absorbability decreases and ink breakthrough may occur. As a result, curling and cockling (absorption wrinkles) after printing may become significant.
In addition, although the basic weight of a base material is not specifically limited, Usually, it is about 20-400 g / m < ² >.

<Undercoat layer>
In the ink jet recording sheet of the present embodiment, formed least two layers coated layer on a substrate made of paper substrate, an anionic colloidal silica treated with the coupling agent, a cationic colloidal silica The surface layer is a surface layer, and an undercoat layer is provided between the surface layer and the substrate .
The undercoat layer contains a pigment as a main component and a polymer as a binder for the pigment, and an adhesive is generally used as the polymer.
In addition, as long as it acts as a binder for the pigment, it is not limited to an adhesive, and other polymers may be used.
By providing such an undercoat layer, the ink absorption capacity and absorption speed can be increased.
In this case, the above-described surface layer and undercoat layer may each be formed in a plurality of layers.

[Pigment]
As the pigment contained in the undercoat layer, pigments generally used in the coated paper manufacturing field are used.
Examples of these pigments include kaolin, clay, calcined clay, amorphous silica (also referred to as amorphous silica), synthetic amorphous silica, colloidal silica, zinc oxide, aluminum hydroxide, calcium carbonate, satin white, and silicic acid. Aluminum, alumina, zeolite, synthetic zeolite, sepiolite, smectite, synthetic smectite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, hydrotalcite, urea resin plastic pigment, benzoguanamine plastic pigment, etc. .
These pigments can be used singly or in appropriate combination of two or more.
Among these, it is preferable to use amorphous silica, alumina, or zeolite having high ink absorbability as a main component.

〔adhesive〕
As the adhesive, an adhesive generally used in the coated paper manufacturing field is used.
Examples of these adhesives include (i) proteins such as casein, soy protein, and synthetic protein, (b) various starches such as starch and oxidized starch, (c) polyvinyl alcohol, cationic polyvinyl alcohol, and silyl-modified. Polyvinyl alcohols containing modified polyvinyl alcohol such as polyvinyl alcohol, (2) cellulose derivatives such as carboxymethyl cellulose and methyl cellulose, (e) conjugated diene polymer latex of styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, Examples thereof include vinyl polymer latexes such as acrylic polymer latex and ethylene-vinyl acetate copolymer.
These adhesives can be used individually by 1 type or in combination of 2 or more types as appropriate.

The blending ratio of the pigment and the adhesive of the undercoat layer is generally adjusted in the range of 1 to 100 parts by weight, preferably 2 to 50 parts by weight with respect to 100 parts by weight of the pigment, although it depends on the type. .
In addition, in the undercoat layer, in addition to the pigment and adhesive, various auxiliary agents such as a dispersant, a thickener, an antifoaming agent, an antistatic agent, and an antiseptic used in the production of general coated paper, Fluorescent dyes, colorants and the like can be added as appropriate.

[Ink fixing agent]
Furthermore, a cationic compound as an ink fixing agent is blended in the undercoat layer for the purpose of fixing the dye component in the ink for ink jet recording .
Examples of such cationic compounds include cationic resins and low molecular weight cationic compounds (for example, cationic surfactants). From the viewpoint of the effect of improving the printing density, it is preferable to use a cationic resin. .
The cationic compound is preferably used as a solution or an emulsion.
The cationic resin is insolubilized by means such as cross-linking, and can be used as a cationic organic pigment instead of the ink fixing agent by making it into a particulate form. The pigment is a cation having a reactive functional group (hydroxyl group, carboxyl group, amino group, acetoacetyl group, etc.) by copolymerizing a polyfunctional monomer to form a crosslinked resin when polymerizing the cationic resin. If necessary, a crosslinking agent is added to the functional resin to form a crosslinked resin by means of heat, radiation or the like.
In addition, the cationic resin may play a role as an adhesive.

Examples of the cationic compound include:
(A) Polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine or derivatives thereof,
(B) an acrylic resin having a secondary amine group, a tertiary amine group or a quaternary ammonium group;
(C) Polyvinylamine, polyvinylamidines,
(D) Dicyan-based cationic resin represented by dicyandiamide-formalin polycondensate,
(E) a polyamine cationic resin represented by dicyandiamide-diethylenetriamine polycondensate,
(F) Epichlorohydrin-dimethylamine addition polymer,
(G) Dimethyl diallylammonium chloride-SO ₂ copolymer,
(H) diallylamine salt-SO ₂ copolymer,
(Li) dimethyldiallylammonium chloride polymer,
(Nu) Allylamine salt polymer,
(L) dialkylaminoethyl (meth) acrylate quaternary salt polymer,
(E) Acrylamide-diallylamine salt copolymer,
Etc.
These cationic compounds also have the effect of improving the water resistance of printed images.

1-100 mass parts is preferable with respect to 100 mass parts of pigments contained in an undercoat layer, and, as for the compounding quantity of the said cationic compound, More preferably, it is 5-50 mass parts.
If the blending amount is less than 1 part by mass, the effect of improving the printing density and printing water resistance may not be sufficiently obtained. If the blending amount exceeds 100 parts by mass, conversely, the printing density is lowered or image blurring occurs. There is a fear.

[Method for producing undercoat layer]
The undercoat layer coating liquid comprising the above-described components is generally adjusted to a solid content concentration of 5 to 50% by mass, and ² to 100 g / m ² in dry mass on the substrate, preferably 5 to 5% by mass. It coats so that it may become 50 g / m < ² >, More preferably, 5-20 g / m < ² >.
In this case, if the coating amount of the coating liquid for the undercoat layer is less than 2 g / m ² , the ink absorbability improving effect is not sufficiently exhibited, and bleeding of the recorded image and improvement of the gloss of the surface layer on the undercoat layer are not achieved. When using a paper base as a base material, there is a risk of reducing the effect. As a result, the amount of ink absorbed by the paper base increases, so that the paper after recording causes rippling (cockling) or a spur of the printer ( There is a possibility that problems such as conspicuous press marks (spur marks) by the paper pressing rolls and gears after recording may occur.
On the other hand, if the coating amount exceeds 100 g / m ² , the printing density may be lowered and the strength of the coating layer (undercoat layer) may be lowered, and the powder may easily fall off or be easily damaged. There is a risk of problems.

  The coating method of the undercoat layer is not particularly limited, and various known public coatings 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 die coater, a gravure coater, and a curtain coater. It is coated and dried using any of the devices.

<Ink receiving layer>
In the ink jet recording paper of the present embodiment, an ink receiving layer may be provided between the undercoat layer and the surface layer.
The ink receiving layer is a layer having a secondary particle of amorphous silica having an average particle diameter of 90 to 700 nm and polyvinyl alcohol having a polymerization degree of 3500 or more and a dry coating amount of 5 to 20 g / m ² .
By providing this ink receiving layer, the ink jet recording paper has a high printing density with respect to the dye ink and excellent water resistance of the ink, and has a high printing density with respect to the pigment ink, and High glossiness.

In addition to the above-mentioned amorphous silica, commonly used known pigments such as alumina and colloidal silica can be used in combination with the ink-receiving layer as long as the effects of the present invention are not impaired.
These pigments may be used alone or in combination of two or more.

In the ink receiving layer, it is preferable to use polyvinyl alcohol as an adhesive as the binder. The degree of polymerization of the polyvinyl alcohol is preferably 3500 or more, and particularly preferably 3500 to 5000.
If the degree of polymerization is less than 3500, the strength of the ink receiving layer is weak and cracks are likely to occur, and a sufficient print density cannot be obtained particularly for pigment ink. If the degree of polymerization exceeds 5000, sufficient ink absorbability cannot be obtained, and handling in preparing the coating liquid is not good.

In addition to the pigment and the adhesive, various additives can be appropriately added to the ink receiving layer as long as the effects of the present invention are not impaired.
Examples of such additives include a cationic compound blended in the undercoat layer, other commonly used known adhesives, ink fixing agents, dispersants, crosslinking agents, thickeners, antifoaming agents, charging agents. Examples include inhibitors, preservatives, ultraviolet absorbers, preservability improvers, fluorescent brighteners, and colorants.

  The ink fixing agent is used to fix the dye of the dye ink in the ink receiving layer, as in the case of being provided in the undercoat layer, in order to obtain good dye ink coloring and storage properties and ink absorbability. In addition, the same ink fixing agent as used for 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, a high defoaming effect and a wetting effect in the coating liquid can be expected.

[Method for producing ink receiving 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 ink receiving layer is produced by applying an ink receiving layer coating liquid comprising the above-described components onto the undercoat layer.
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.
As a coating method of the ink receiving layer coating liquid, in addition to the coating apparatus used for the undercoat layer described above, any one of various known and publicly used coating apparatuses such as a slot die coater, a slide coater, and a spray is used. The coating method to apply is mentioned.

[Crosslinking agent]
In order to prevent cracking of the ink receiving layer, an adhesive for the undercoat layer and a crosslinking agent for crosslinking the adhesive for the ink receiving layer, or a gelling agent for crosslinking and gelling these adhesives is used. It is preferable to crosslink the adhesive.
Are these cross-linking agents (including gelling agents) added to the ink receiving layer coating solution, or pre-coated as an aqueous coating solution on the undercoat layer before coating the ink receiving layer? Alternatively, the ink receiving layer is used after being applied on the ink receiving layer.
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. Can be mentioned.
Examples of the gelling agent that cross-links and gels polyvinyl alcohol 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 the boron-containing compound is less than 0.01 g / m ^2, a fear that the crosslinking of the hydrophilic adhesive, and gelation of the coating liquid is not sufficient, the cracking in the coating layer occurs There is. Even if the blending amount exceeds 2.0 g / m ² , the high crosslinking density with the adhesive is saturated, and the effect of preventing cracking of the coating layer is not further improved.

<Glossing treatment of surface layer>
In the ink jet recording paper of the present embodiment, the surface layer described above is formed on the surface of the ink receiving layer.
The surface layer is formed by applying a coating liquid containing the above ingredients on the surface of the ink-receiving layer is formed on the glossy surface by glossing.
In this surface layer, the ink-jet recording sheet, when having a coating layer of 2-layer between the surface layer and the undercoat layer is formed by coating on the subbing layer.

Glossing process to the surface layer, in consideration of applying the ink jet recording suitability and excellent high gloss, cast processing such as casting method or a film transfer method using a mirror drum used.

In general, the casting method means that the coating layer is cast on a smooth cast drum (drum made of mirror-finished metal, plastic, glass, etc.), mirror-finished metal plate, plastic sheet, plastic film, or glass plate. It is a method of obtaining a smooth and glossy coating layer surface by drying and copying these smooth surfaces onto the coating layer.
In the present embodiment, the method of providing the surface layer by a casting method using a heated mirror drum is a method for receiving ink directly on the base material, on the undercoat layer provided on the base material, or on the undercoat layer. On the layer, the surface layer coating solution is applied to form a coating layer. (1) A method in which the coating layer is pressed against a heated mirror drum while it is wet and dried to finish (wet (Cast method), (2) The above coating layer is once dried and then re-wet, pressed onto a heated mirror drum and dried to finish (rewet casting method), (3) The coating layer is gelled For example, a gelled cast method in which a heated mirror drum is pressed and dried to finish.
(4) The surface coating liquid is directly applied to the heated mirror drum and dried, and then provided directly on the base material, on the undercoat layer provided on the base material, or on the undercoat layer. Alternatively, a method (precast method) may be employed in which the mirror drum is pressed onto the ink receiving layer and the surface layer is transferred to finish.
The temperature of the mirror drum heated in each of the above methods is, for example, 50 to 150 ° C, preferably 70 to 120 ° C.

As the film transfer method, (1) the surface layer coating solution is applied to the surface of the base material or the surface of the undercoat layer provided on the base material, and the coating layer is smooth while it is wet. A method of layering and drying a smooth film or sheet, and then peeling off and finishing the smooth film or sheet. (2) A coating layer is provided on the smooth film or sheet by applying the above surface layer coating solution. While the coating layer is in a wet state, directly on the substrate to be bonded in a dry state, on the undercoat layer provided on the substrate, or on the ink receiving layer provided on the undercoat layer In addition, after this coating layer is pressed and dried, a smooth film or sheet is peeled off and finished, or the surface coating layer is dried and directly applied onto a substrate that is somewhat wet. Or on an undercoat layer on a substrate or undercoat The ink-receiving layer provided on the above, pressed against the coating layer, after drying, a method of finishing by peeling off a smooth film or sheet.
In this case, the smooth film or sheet preferably has a surface roughness (JIS-B-0601) of Ra = 0.5 μm or less, and more preferably Ra = 0.05 μm or less.
Among the above cast methods, when the cast method using a heated mirror surface tends to be superior in surface smoothness compared to the film transfer method, it is more advantageous in terms of productivity and cost. Many are preferable.

The coating amount of the surface layer coating solution is preferably 0.1 to 30 g / m ² in terms of dry solid content.
Here, when the density is less than 0.1 g / m ² , the print density and gloss may not be sufficiently obtained. When the density exceeds 30 g / m ² , the effect is saturated, and drying may be burdened to reduce the operability. is there.
In addition, after providing a coating layer by cast finishing, a smoothing process can also be performed by a super calender etc.

  The coating method of the surface layer coating solution formed prior to each casting is, for example, a blade coater, an air knife coater, a roll coater, a brush coater, a champlex coater, a bar coater, a lip coater, a die coater, a gravure coater, etc. Coating is performed using any of publicly known coating apparatuses.

Method for producing a glossy ink jet recording sheet described above, but that provides excellent recording body gloss, in particular, 75 ° gloss of the surface of the recording surfaces (JIS-Z-8741) is 30% or more Is preferable, more preferably 40% or more, still more preferably 65% or more. This glossiness can be 95% in the above method.
According to the production method of the present invention, a high-quality recorded image with excellent image quality and photographic tone can be obtained by using such an inkjet recording paper having excellent gloss.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the following Example.
In the following description, “mass%” and “part by mass” are abbreviated as “%” and “part”, respectively, unless otherwise specified.

Example 1
[Preparation of paper substrate]
100 parts of wood pulp (LBKP; freeness 500 ml CSF), 9 parts of calcined kaolin (trade name: Ansilex, Engelhard & Mineral Co., Ltd.), 0.1 part of commercial sizing agent (trade name: PM356, Arakawa Chemical ( Manufactured by Co., Ltd.), 1.5 parts of sulfuric acid band, 0.7 parts of wet paper strength agent (trade name: WS570, manufactured by Nippon PMC Co., Ltd.), and 0.75 parts of starch. A paper base material as a base material having a basis weight of 120 g / m ² was produced by a machine. This paper substrate had a Steecht sizing degree of 60 seconds.
In the following examples and comparative examples, this paper substrate was used.

[Production of anionic colloidal silica treated with a coupling agent]
In an apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel, anionic colloidal silica having an average particle size of 50 nm and a solid content of 40% as a pigment (trade name: Cataloid SI-45P, manufactured by Catalyst Kasei Kogyo Co., Ltd.) ) 985 parts were charged and heated to 75 ° C. Next, 15 parts of γ-glycidoxypropylmethyldimethoxysilane as a coupling agent was added dropwise over 15 minutes while maintaining at 75 ° C. with stirring, and the reaction was completed by incubating at the same temperature for 30 minutes. This was cooled to obtain an anionic colloidal silica (S-1) treated with a coupling agent.

[Formation of undercoat layer]
100 parts of secondary particle amorphous silica (trade name; Fine Seal X-45, manufactured by Tokuyama Corporation, specific surface area 340 m ² / g, average particle size 4.5 μm) as pigment, silyl-modified polyvinyl as adhesive 25 parts of alcohol (trade name: R1130, manufactured by Kuraray Co., Ltd.), 5 parts of dicyandiamide resin (trade name: Neofix E-117, manufactured by Nikka Chemical Co., Ltd.) as a cationic compound, and cationic acrylamide Diallylamine salt copolymer (trade name: Sumirez Resin SR1001, manufactured by Sumitomo Chemical Co., Ltd.) 15 parts, fluorescent dye (trade name: Whitetex BPSH, manufactured by Sumitomo Chemical Co., Ltd.) 2 parts, sodium polyphosphate as a dispersant 0.5 part was added and the coating liquid for undercoat layers of solid content concentration 18% was prepared.
Then, this undercoat layer coating solution was coated on the paper substrate with an air knife coater so that the dry weight was 8 g / m ² and dried to form an undercoat layer.

[Formation of ink receiving layer]
Commercially available gas phase method silica (trade name: Leoseal QS-30, manufactured by Tokuyama Corporation, average primary particle size 9 nm, specific surface area 300 m ² / g) as a pigment is pulverized and dispersed with a high-speed collision type homogenizer. Was repeated to obtain secondary particles, and after classification, a 10% silica dispersion having an average particle diameter of 200 nm was prepared. To 100 parts of the dispersion (in solid content), 15 parts of polyvinyl alcohol (trade name: PVA145, manufactured by Kuraray Co., Ltd., polymerization degree 4500) was mixed to prepare a coating liquid for forming an ink receiving layer.
Thereafter, a 3% by mass borax aqueous solution was applied onto the undercoat layer so that the dry coating amount was 1.5 g / m ² , and the above-mentioned dry mass was 17 g / m ² without drying. The ink receiving layer forming coating solution was applied by a die coater. Then, the ink receiving layer was formed by drying with hot air at 150 ° C. so that the equilibrium moisture content was 8%.

[Formation of surface layer]
As the pigment, the anionic colloidal silica (S-1) treated with the coupling agent and the cationic colloidal silica (trade name: Snowtex AK-L, manufactured by Nissan Chemical Industries, Ltd.), and their solid content The mixture was mixed so that the ratio was 5/95, and a composition having a solid content concentration of 30% comprising 2 parts of polyethylene wax (nonionic) as a release agent was prepared to prepare a surface layer coating solution.
Thereafter, the surface layer coating liquid was applied on the ink receiving layer, and then the surface was pressed against a cast drum having a surface temperature of 100 ° C. at a linear pressure of 200 kg / cm to perform wet casting.

(Example 2)
Example 1 except that the coating solution for surface layer was prepared by changing the solid content ratio of the anionic colloidal silica (S-1) treated with the coupling agent to the cationic colloidal silica to 30/70 and using it. In the same manner, an inkjet recording paper was obtained.

(Example 3)
Inkjet recording paper was obtained in the same manner as in Example 1 except that 10 parts of polyvinyl alcohol (trade name PVA117, manufactured by Kuraray Co., Ltd.) was added to the surface layer coating solution.

(Comparative Example 1)
Except for changing the colloidal silica that has undergone coupling treatment in the surface layer coating solution to commercially available anionic colloidal silica that has not been subjected to coupling treatment (trade name: Snowtex OL, manufactured by Nissan Chemical Industries, Ltd.) Inkjet recording paper was obtained in the same manner as Example 1.

(Comparative Example 2)
An ink jet recording paper was obtained in the same manner as in Example 1 except that all the colloidal silica in the surface layer coating solution was changed to cationic colloidal silica.

(Evaluation method and evaluation criteria)
About the inkjet recording paper obtained by the said Example and the comparative example, the printability and glossiness in inkjet recording were evaluated with the following method.
[Evaluation of printability in inkjet recording]
Evaluation of printability was performed using both dye ink and pigment ink type printers, with print density, ink absorbency, glossiness of printed parts, glossiness, surface strength, printer transportability, scratch resistance, and operation. I went about sex.

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), printing is performed with black, cyan, magenta, yellow, red, green, and blue solid colors arranged in a grid pattern so as to touch each other. The ink bleeding was evaluated visually 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.

(Glossy impression on 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 symbol: N1, image name: glass and female) 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]
The surface of the blank inkjet recording paper was visually observed from an oblique direction, and glossiness was evaluated according to the following criteria.
◎: Very high glossiness ○: High glossiness ×: Inferior glossiness

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

[Abrasion resistance]
After 2 minutes from printing, the printed surface was lightly rubbed 3 times with tissue paper, and how much the recorded image was held was visually evaluated according to the following criteria.
◎: The recorded image is almost completely retained. ○: The recorded image is slightly retained, and the original image can be read sufficiently. △: The recorded image has lost its clarity. It is difficult to identify what is ×: Most of the pigment-based ink on the surface has disappeared

[Operability]
The wrinkles corresponding to the edge portion of the substrate adhering to the cast drum when the wet cast treatment was performed and the fogging generated on the cast drum were judged visually to evaluate the continuous operability.
○: Excellent in continuous operability △: Operation is sometimes interrupted and cleaning is required ×: Operation is often interrupted and cleaning is required

  The evaluation results are shown in Table 1.

As is apparent from the results shown in Table 1, Examples 1 to 3 according to the present invention are excellent in all the evaluation items described above, and particularly excellent in ink absorbability.
In addition, Example 3 is extremely excellent in the glossiness of the printed portion, glossiness, and aggregation unevenness.
On the other hand, Comparative Example 1 is not practical in cohesive unevenness, and is slightly inferior in scratch resistance and operability. Comparative Example 2 does not satisfy practicality in operability, and glossiness of the printed portion. , Glossiness, and aggregation unevenness are slightly inferior, and none of them is satisfactory as an ink jet recording paper.

Claims (3)

In a method for producing a glossy inkjet recording paper having a base material and at least two coating layers formed on the base material,
At least the lower layer of the coating layer contains a cationic compound as an ink fixing agent,
At least the surface layer of the coating layer, as a pigment, and an anionic colloidal silica coupling process, the cationic colloidal silica contained in the solid content weight ratio of 1/99 to 30/70, the gloss by casting process A method for producing a glossy ink jet recording paper , characterized by being processed . The method for producing a glossy ink jet recording paper according to claim 1, wherein the coupling agent used in the coupling treatment is a silane coupling agent. 2. The coating layer according to claim 1, further comprising a polymer as a pigment binder. 2 is a method for producing the glossy ink jet recording paper described in 2.