JP2021030630A - Inkjet glossy paper and method for producing the same - Google Patents

Abstract

To provide inkjet glossy paper that has sufficient strength to be processed and used as a label, and a discoloration inhibitory effect, while maintaining inkjet suitability.SOLUTION: This inkjet glossy paper has, on at least one side of base paper, a glossy layer having a pigment and a binder as the main components. The glossy layer contains organic acid, inorganic metal salt, and calcium formate as a coagulant.SELECTED DRAWING: None

Description

The present invention relates to glossy paper for inkjet. In particular, the present invention relates to a glossy paper for an inkjet having a strength that can withstand a process in processing and use as a label application and an effect of suppressing discoloration while maintaining the suitability for an inkjet.

The inkjet recording method is a method in which dots are formed by ejecting ink droplets and adhering them on a recording paper to perform recording. In recent years, technological advances in inkjet printers, inks, and recording media have made it possible to record with high print quality. The so-called glossy paper for inkjet, which has a glossy surface on the recording medium, is a glossy paper having a paper and / or film as a support and a pigment coating layer containing a pigment and a binder as main components (hereinafter, "" "Void type glossy paper") or glossy paper having a pigment-free resin coating layer on the surface (hereinafter referred to as "swelling type glossy paper") is often used.

The technology of an inkjet printer has been used not only in personal printers used at home but also in fields such as commercial printing in which variable information is digitized and printed at high speed. That is, in recent years, the so-called on-demand printing method has been introduced in the field of commercial printing, and many inkjet printing machines adopting the on-demand printing method have appeared. This on-demand printing method is suitable for printing a small number of copies because it is possible to print information directly on a medium such as paper without making a plate.

In the field of commercial printing, inkjet paper is sometimes used as a base material for labels such as price display, bar code display, and advertising. In particular, when the inkjet paper is glossy paper, the photographic image can be printed more clearly, so that the advertising effect is large. For base materials used for labels, after the base material manufacturing process, a printing process or a process of applying adhesive processing to the opposite surface of the printed surface and pasting a release sheet to form a label (label processing process). There are many practical post-processes such as the process of attaching a label as a product and the process of transporting a labeled product, which may damage the printed surface. In glossy paper, when the surface strength of the glossy layer is weak, the surface of the glossy layer is easily scratched because it is processed by winding in the label processing step. Further, even when it is used as a label, the surface of the glossy layer is easily scratched and the appearance is often spoiled. Therefore, a glossy paper for inkjet that has enough strength to withstand the processing and use process of the label is required.

As a method for producing glossy paper, a glossy paper is widely produced by a cast coating method in which a coated surface of paper is pressure-bonded to a glossy cast drum to copy the gloss. A so-called gelling method in which a glossy layer containing a pigment and a binder as main components is provided, a coagulating liquid is applied while the glossy layer is in a wet state, and the solidifying liquid is pressed against a heated cast drum to give a strong gloss finish. Then, by solidifying the coating liquid for the glossy layer on the paper surface, the cast drum can be pressure-bonded without gaps to obtain a good glossy feeling, and the strength of the glossy layer is increased by the cross-linking effect of the coagulant. If a coagulant or a cross-linking agent is added to the coating liquid for a glossy layer in advance, the viscosity of the coating liquid increases, and not only defects are likely to occur on the glossy surface, but also excessive coagulation proceeds, so that the strength is rather weakened. If the strength is low, the surface of the glossy paper is likely to be scratched, and the glossiness of the surface may be lost, or a part of the printed characters or the image may be lost.

Discoloration of paper refers to the phenomenon of discoloration of paper. Discoloration of paper occurs when two factors, a paper factor and an environmental factor, are combined. The main cause of discoloration is that the coating layer and base paper use chemicals that easily discolor, and the environmental factors are light, heat, oxygen, ozone, NOx, SOx, other acid gases, and bases. It is thought to be in contact with acid gas. Inkjet glossy paper for labels may be exposed for a long period of time under conditions that are easily discolored due to environmental factors, depending on the transportation of labeled items and storage conditions at the customer, resulting in a yellow discoloration of the glossy surface. This may impair the original color of the glossy paper and the texture of the printed image.

Further, as the glossy paper for inkjet in recent years, void type glossy paper has become the mainstream. The void-type glossy paper has pores on the surface and inside of the glossy surface, and absorbs ink from the pores to obtain the suitability for inkjet. The term "invertical suitability" as used herein refers to general inkjet suitability such as density and uniformity of color material in a solid print area and image bleeding. It is considered that the void-type glossy paper is more likely to be discolored than other papers because the gaseous substance, which is an environmental factor that promotes discoloration, easily penetrates into the paper due to the pore structure.

As described above, it is an issue to develop a void-type glossy paper having excellent inkjet suitability, and further having strength and a discoloration suppressing effect that can withstand processing and use processes for label applications.

As such a glossy paper for inkjet, there is a proposal to improve the appropriateness of inkjet and the effect of suppressing discoloration by containing at least one kind of inorganic pigment and at least one kind of troponoid in the ink receiving layer (see Patent Document 1). .. Proposal to improve inkjet suitability and strength by containing only anionic monodisperse spherical colloidal silica as a pigment in the glossy layer and containing a resin emulsion having a glass transition temperature of 30 to 80 ° C. as a binder in the glossy layer. (See Patent Document 2).

However, although the glossy paper for inkjet described in Patent Document 1 has the appropriateness for inkjet and the effect of suppressing discoloration, the strength is insufficient and may not satisfy the strength required for glossy paper for labels. Although the glossy paper for inkjet described in Patent Document 2 has the effect of improving the suitability and strength of the inkjet, the effect of suppressing discoloration is insufficient, and the glossy surface may be discolored when actually used.

Japanese Unexamined Patent Publication No. 2003-251918 Japanese Unexamined Patent Publication No. 2014-46462

Therefore, an object of the present invention is to provide a glossy paper for an inkjet having a strength that can withstand a processing or a process of use as a label application and a discoloration suppressing effect while maintaining the suitability for an inkjet, and a method for producing the same.

The glossy paper for inkjet according to the present invention has a glossy layer containing a pigment and a binder as main components on at least one surface of the base paper, and the glossy layer serves as an organic acid, an inorganic metal salt, and a coagulant. It is characterized by containing calcium formate. As a result, it is possible to obtain a glossy paper for an inkjet that suppresses discoloration and has a strength that can withstand a processing or a process of use while maintaining the suitability for an inkjet.

In the glossy paper for inkjet according to the present invention, it is preferable that the organic acid is lactic acid. Especially excellent in suppressing discoloration.

In the glossy paper for inkjet according to the present invention, it is preferable that the glossy layer contains an ink fixing agent. Especially excellent in inkjet suitability.

In the glossy paper for inkjet according to the present invention, a glossy layer containing a pigment and a binder as main components is provided on at least one surface of the base paper, and a coagulating liquid is applied while the glossy layer is in a wet state. It is preferable that the glossy paper for inkjet is pressed against a heated cast drum to give a strong gloss finish, and the method for producing the glossy paper for inkjet is a step of preparing a base paper and the above-mentioned one surface of the base paper. The step of applying a coating liquid for a glossy layer containing a pigment and a binder as main components, and a coagulating liquid containing an organic acid, an inorganic metal salt, and calcium formate as a coagulant are described above. It is characterized by having a step of applying it while the glossy layer is in a wet state, coagulating it, and then pressing it against a heated cast drum to finish it with a strong gloss. It is possible to obtain an inkjet recording glossy paper having strength that can withstand processing and use processes while suppressing discoloration while maintaining inkjet suitability.

In the glossy paper for inkjet according to the present invention, the pH of the coagulating liquid is preferably 4.0 to 9.0. Especially excellent in the stability of the coagulant in operation.

The present invention can provide a glossy paper for recording, which has strength that can withstand processing and use processes while suppressing discoloration while maintaining the suitability for inkjet. In particular, it is suitable as glossy paper for labels that are used under air exposure conditions and require further strength.

Next, the present invention will be described in detail by showing embodiments, but the present invention is not construed as being limited to these descriptions. The embodiments may be modified in various ways as long as the effects of the present invention are exhibited.

The glossy paper for inkjet according to the present embodiment has a glossy layer containing a pigment and a binder as main components on at least one surface of the base paper, and the glossy layer serves as an organic acid, an inorganic metal salt, and a coagulant. It is characterized by containing calcium formate. As a result, it is possible to provide a glossy recording paper having strength and a discoloration suppressing effect that can withstand processing and use processes for label applications while maintaining inkjet suitability.

As the base paper used in this embodiment, a paper base material such as high-quality paper, medium-quality paper, or white paperboard can be used. It is also possible to use acid paper and acid-free paper. The fillers used for the base paper include heavy calcium carbonate, light calcium carbonate, magnesium carbonate, titanium oxide, synthetic silica, alumina, talc, calcined kaolin clay, kaolin clay, bentonite, zeolite, aluminum hydroxide, and zinc oxide. It is possible to use known pigments such as. In addition to the above pulp and filler, various paper-making chemicals such as known paper strength agents, sulfate bands, yield improvers, sizing agents, dyes, and fluorescent dyes are appropriately used in the paper material. The method of preparing each paper material, the method of blending, and the method of adding each paper-making chemical are not particularly limited as long as they do not impair the effects of the present embodiment. Further, it is possible to make a paper by applying a known paper machine such as a circular net paper machine, a long net paper machine and a twin wire paper machine using the above paper material. Further, in order to suppress excessive penetration of the coating liquid, it is preferable to apply a known water-soluble polymer such as starch, polyvinyl alcohol, or polyacrylamide to the paper support by a size press or the like.

In the glossy paper for inkjet according to the present embodiment, it is preferable that the glossy layer is formed by drying by a cast coating method as a method for imparting high gloss to the surface of the glossy layer. As the cast coat method, a wet method, a gelation method, and a rewet method are known. The glossy paper for inkjet of the present invention is preferably produced by a gelling method or a rewetting method, and more preferably a gelling method. The gelling method is a method in which a coagulating liquid is applied and coagulated while the glossy layer is in a wet state, and the cast drum is pressed against a heated cast drum to be dried. Further, in the method for producing glossy paper for inkjet of the present invention, it is produced by a gelation method.

The glossy layer of the present invention contains calcium formate. In the coagulation treatment in the gelation method according to the present embodiment, it is important to select a coagulant that effectively coagulates the binder of the glossy layer, and calcium formate is used in the present invention. As a result, in the present invention, the glossy layer contains calcium formate. By limiting the coagulant to calcium formate, the strength of the glossy surface is increased by the strong coagulation force. The concentration of the coagulant in the coagulant is preferably in the range of 0.5 to 5% by mass. More preferably, it is 1 to 3% by mass. When the concentration of the coagulant in the coagulant is less than 0.5% by mass, the amount of calcium formate is small with respect to the area of the glossy layer and the coagulant power is not sufficient, so that the strength may be inferior. Further, there is a possibility that the glossiness of the cast drum may be impaired due to a small defect (hereinafter referred to as “pit”) in which the glossiness of the cast drum cannot be copied when the cast drum is pressed against the cast drum. If the concentration of the coagulant in the coagulant exceeds 5% by mass, the discoloration may be exacerbated for unknown reasons. Further, if the cohesive force is too strong, the coating liquid cannot be wetted and spread on the cast drum, which may cause a defect on the glossy surface. It is desirable that the concentration of calcium formate be kept to the minimum necessary amount that does not generate pits.

The glossy layer of the glossy paper for inkjet according to the present invention contains an organic acid. In the coagulation treatment in the gelation method according to the present embodiment, it is preferable to add an organic acid to the coagulation liquid. As a result, the glossy layer contains an organic acid. By blending an organic acid, the pH of the glossy surface can be lowered and discoloration can be suppressed. Examples of the organic acid include lactic acid, citric acid, malic acid, phosphoric acid, glycolic acid and the like, and these may be used alone or in combination of two or more. In particular, hydroxy acids are preferable, and lactic acid, citric acid, and malic acid are particularly preferable. More preferably, it is lactic acid. The coagulating liquid containing lactic acid is particularly excellent in stability, and agglomerates are less likely to be generated, so that it is possible to obtain glossy paper for inkjet with excellent surface quality. The concentration of the organic acid in the coagulation liquid is preferably a concentration in which the gram equivalent ratio of calcium formate: organic acid is 1: 0.5 to 1: 8. More preferably, it is 1: 1 to 1: 6. Within this ratio range, an excellent discoloration improving effect can be obtained. When the ratio of the organic acid to calcium formate in the coagulation liquid is less than 1: 0.5, that is, when the ratio of the organic acid is less than 0.5, a sufficient discoloration improving effect may not be obtained. When the ratio of organic acid to calcium formate in the coagulation liquid exceeds 1: 8, that is, when the ratio of organic acid exceeds 8, the discoloration improving effect is high, but the coagulation liquid becomes unstable and aggregates in the coagulation liquid. Etc. may occur and the surface quality of the glossy surface may deteriorate. Further, when the pH of the coagulating liquid is lowered by adding an organic acid and stable operation becomes difficult, the pH of the coagulating liquid may be adjusted with aqueous ammonia or the like. It is preferable to adjust the pH of the coagulant to 4.0-9.0. More preferably, it is 5.0 to 8.0, for example, 5.5 to 7.0.

The glossy layer of the glossy paper for inkjet according to the present invention contains an inorganic metal salt. In the coagulation treatment according to the present embodiment, it is preferable to add an inorganic metal salt to the coagulation liquid. As a result, the glossy layer contains an inorganic metal salt. The inorganic metal salt may be either a monovalent metal salt or a divalent or higher metal salt. As the monovalent metal, an alkali metal salt is particularly preferable, and a potassium salt and a sodium salt are particularly preferable. Examples of the divalent or higher valent metal include calcium salt, magnesium salt, zinc salt, aluminum salt and the like. Among them, alkaline earth metal salt is preferable, and calcium salt and magnesium salt are particularly preferable. These may be used alone or in combination of two or more. For example, magnesium sulfate, magnesium chloride, calcium chloride and the like may be used. Excellent inkjet suitability can be obtained with dye inks and pigment inks. The concentration of the inorganic metal salt in the coagulation liquid is preferably in the range of 0.1 to 7% by mass. More preferably, it is 0.5 to 3% by mass. If the amount of the inorganic metal salt in the coagulating liquid is less than 0.1% by mass, sufficient inkjet suitability may not be obtained. In particular, image blurring worsens. If the amount of the inorganic metal salt in the coagulant exceeds 7 mass, it may affect the coagulant force of the coagulant and reduce the strength of the glossy surface, or may cause pits on the surface of the glossy surface to impair the glossiness. is there.

The glossy layer of the glossy paper for inkjet according to the present invention preferably contains an ink fixing agent. In the coagulation treatment according to the present embodiment, the coagulation liquid can contain a cationic polymer as an ink fixing agent. This makes it possible to improve the density of the color material of the inkjet ink. Cationic polymers include, for example, polyethyleneimine, epichlorohydrin-modified polyalkylamine, polyamine, polyamine polyamide epichlorohydrin, dimethylamine ammonia epichlorohydrin, polyvinylbenzyltrimethylammonium halide, polydiacrylicdimethylammonium halide, polydimethylaminoethyl methacrylate hydrochloride, polyvinylpyri. Diamhalide, cationic polyacrylamide, cationic polystyrene copolymer, diallyldimethylammonium chloride polymer, diallyldimethylammonium chloride sulfur dioxide copolymer, diallyldimethylammonium chlorideamide copolymer, dicyandiamideformalin polycondensate, dicyandiamidediethylenetriamine weight Condensates, polyallylamines, polydialylamines, polyallylamine hydrochlorides, polyacrylamide-based resins, polyamide epoxy resins, melamine resinic acid colloids, urea-based resins, cationically modified polyvinyl alcohols, amino acid-type amphoteric surfactants, betaine-type compounds, polyamidine-type compounds , Other quaternary ammonium salts, cationic polyurethane resin. These may be used alone or in combination of two or more. The concentration of the ink fixing agent in the coagulating liquid is preferably in the range of 1 to 15% by mass in the coagulating liquid. More preferably, it is 3 to 10% by mass, for example, 3 to 7% by mass.

Further, when the concentration of the coagulating liquid is high, the coagulating force becomes stronger and the strength is further improved, which is preferable. The solid content concentration of the coagulation liquid is preferably 5% by mass or more. More preferably, it is 8% by mass or more. The upper limit of the solid content concentration of the coagulation liquid is preferably 8 to 20% by mass, for example, 8 to 15% by mass from the viewpoint of workability and cost. Although the gelation method has been described so far, in the present embodiment, the ink gloss layer may be dried by the rewet method. The rewet method is a method in which a glossy layer is coated and dried, and then the coated layer is moistened with a rewetting liquid and pressed against a cast drum.

The amount of the coagulant applied (absolute dry mass) is preferably ^{0.01 to 6 / m 2 per side.} More preferably 0.5 to 5 g / ^{m 2,} more preferably from 1 to 4 g / ^{m 2.} If it is less than 0.01 g / m ² , sufficient coagulation force cannot be obtained, so that strength and glossiness may not be obtained. If it exceeds 6 g / m ² , the coagulation force is too strong, which may cause defects on the glossy surface.

The structure of the glossy layer according to the present embodiment needs to contain a pigment and a binder as main components. The pigment used here is not particularly limited, and known pigments such as silica, alumina, clay, calcium carbonate, talc, and titanium oxide can be used. These can be used alone or in combination of two or more as long as the effects of the present invention are not impaired.

Examples of the binder contained in the glossy layer include polyvinyl alcohol, silanol-modified polyvinyl alcohol, polyvinyl acetal, starch, carboxymethyl cellulose, casein, gelatin, soybean protein, acrylic resin, urethane resin, and styrene-acrylic resin. Known binders such as polyester resins, styrene-butadiene copolymer latex, vinyl polymer latex such as ethylene-vinyl acetate copolymer, and acrylic-silicone resins can be used. These may be used alone or in combination of two or more. In particular, soy protein and casein are preferable. Since soy protein and casein are effectively coagulated by calcium formate, which is a coagulant, the strength of the glossy surface is enhanced by using these as a binder. The amount of the binder used may be determined in consideration of the printability of the glossy paper, the strength of the glossy layer, the surface glossiness, the coating liquid property, etc., but 1 to 100 parts by mass of the pigment in the glossy layer. It is preferably in the range of 100 parts by mass. It is more preferably 1 to 50 parts by mass, and even more preferably 2 to 40 parts by mass, for example, 4 to 15 parts by mass. If it is less than 1 part by mass, the strength of the coating layer may decrease. If it exceeds 100 parts by mass, the ink absorbability may decrease. For example, casein may be used in combination of 5 to 15 parts by mass as a binder with respect to 100 parts by mass of spherical colloidal silica as a pigment.

In addition to pigments and binders, the glossy layer includes mold release agents, dispersants, thickeners, preservatives, defoamers, coloring dyes, coloring pigments, fluorescent whitening agents, water resistant agents, antioxidants, and ultraviolet rays. Auxiliary agents such as absorbents can be appropriately selected and blended. For example, 1 to 3 parts by mass of a mold release agent can be blended with 100 parts by mass of the pigment.

As a coating method of the coating liquid for forming the glossy layer of the present embodiment, known coating methods such as an air knife coater, a roll coater, a reverse roll coater, a bar coater, a comma coater, a blade coater, and a simultaneous multi-layer coating machine are used. There is a machine, but any one may be used.

The coating amount (absolute dry mass) of the glossy layer is preferably ^{3 to 20 / m 2 before the treatment of the coagulating liquid.} More preferably 4 to 15 g / ^{m 2,} more preferably from 5 to 10 g / ^{m 2.} If it is less than 3 g / m ² , the ink absorbability may be inferior. If it exceeds 20 g / m ² , the strength of the glossy surface may be insufficient.

Further, as a method for imparting high gloss to the surface of the glossy layer, it is preferable that the glossy layer is formed by drying by a cast coating method. It is also possible to perform a calendar process such as a machine calendar, a soft calendar, or a super calendar after the glossy layer is dried to perform a smoothing process.

In the glossy paper for inkjet of the present embodiment, one or more ink receiving layers having a pigment and a binder can be provided between the glossy layer and the base paper. By providing the ink receiving layer, it is possible to obtain a glossy paper for an inkjet that has better ink absorbency. The ink receiving layer may contain a pigment and a binder as in the case of glossy paper for inkjet recording having a general pigment coating layer. The pigment used here is not particularly limited, and silica, for example, amorphous silica, colloidal silica, and known pigments such as alumina, clay, calcium carbonate, talc, and titanium oxide may be used. It is possible. These can be used alone or in combination of two or more as long as the effects of the present invention are not impaired.

The binder contained in the ink receiving layer is not particularly limited, and is, for example, polyvinyl alcohol, silanol-modified polyvinyl alcohol, polyvinyl acetal, starch, carboxymethyl cellulose, casein, gelatin, soybean protein, acrylic resin, urethane-based. Known binders such as resins, styrene-acrylic resins, polyester resins, styrene-butadiene copolymer latex, vinyl polymer latex such as ethylene-vinyl acetate copolymer, acrylic-silicone resin, etc. It is possible to use. These may be used alone or in combination of two or more. The amount of the binder used may be determined in consideration of the printability of glossy paper, the strength of the ink receiving layer, the surface glossiness, the coating liquid property, etc., with respect to 100 parts by mass of the pigment in the ink receiving layer. It is preferably in the range of 3 to 100 parts by mass. It is more preferably 5 to 80 parts by mass, and even more preferably 40 to 70 parts by mass, for example, 50 to 65 parts by mass. If it is less than 3 parts by mass, the strength of the coating layer may decrease. If it exceeds 100 parts by mass, the ink absorbability may decrease. For example, 5 to 10 parts by mass of polyvinyl alcohol and 40 to 60 parts by mass of ethylene-vinyl acetate copolymer may be used with respect to 100 parts by mass of amorphous silica as a pigment.

As a coating method of the coating liquid for forming the ink receiving layer, there are known coating machines such as an air knife, a roll coater, a bar coater, a comma coater, a blade coater, and a simultaneous multi-layer coating machine. May be used. The coating amount (absolute dry mass) of the ink receiving layer is not particularly limited, but if the coating amount is too small, the ink absorbability may be inferior. Therefore, the solid content equivalent is 3 g / m ² or more per side. Is preferable. Further, if the amount of coating is too large, the binder migration may occur when the glossy layer is coated on the ink receiving layer, the binder may move unevenly, and the strength of the glossy layer may decrease. It is preferably 10 g / m ² or less. The coating amount of the ink receiving layer is more preferably 3 to 8 g / m ² , and even more preferably 4 to 7 g / m ² . The ink receiving layer and / or the intermediate layer can be smoothed by a known calendar device such as a super calendar, a machine calendar, or a soft calendar in order to obtain a certain smoothness after coating.

The total coating amount (absolute dry mass) of all the coating layers on the support is preferably 6 to ^{30 g / m 2 per side.} More preferably, it is 7 to 25 g / m ² . If the total coating amount ^{exceeds 30 g / m 2} , the productivity will be inferior. If the total coating amount is ^{less than 6 g / m 2} , the ink absorbency may be inferior.

The inkjet glossy paper according to the present invention is preferably used as a label inkjet glossy paper. By providing an adhesive layer on the other surface of the paper base material, it can be used as a glossy paper for an inkjet for a label. The adhesive layer can be provided by a commonly used method, for example, a method of crimping with a press roll or the like. As the pressure-sensitive adhesive used for the adhesive layer, a rubber-based or acrylic resin-based pressure-sensitive adhesive can be used. The main raw material for rubber is natural rubber or styrene-butadiene rubber, and in natural rubber, a rosin resin, a plasticizer, or the like is added. When styrene-butadiene rubber is used as the main raw material, it is melted and coated. In the acrylic resin system, it is made by polymerizing an acrylic monomer such as 2-ethylhexyl acrylate, butyl acrylate, ethyl acrylate, acrylic acid, and β-hydroxyethyl acrylate. Depending on the method of polymerization, an organic solvent may be used, or an emulsion type that is polymerized while being emulsified in water using a surfactant can be used.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Further, "parts" and "%" in the example indicate "parts by mass" and "% by mass", respectively, unless otherwise specified. The number of copies added is a value in terms of solid content.

(Example 1)
(Formation of ink receiving layer)
Amorphous silica (Nipgel BY-200: manufactured by Toso Silica Co., Ltd.) 100 parts by mass as a pigment, polyvinyl alcohol (Kuraray Poval 60-98: manufactured by Kuraray Co., Ltd.) 7 parts by mass as a binder, ethylene vinyl acetate (Polysol EVA AD) -13: (manufactured by Showa High Polymer Co., Ltd.) 50 parts by mass was added to water and sufficiently stirred to obtain a coating liquid for an ink receiving layer having a solid content concentration of 15%. ^{On one side of high-quality paper with a basis weight of 80 g / m 2} surface-treated with oxide starch with a size press, apply the coating liquid for the ink receiving layer to an absolute dry coating amount of 6 g / m ² with an air knife coater. It was coated and dried to form an ink receiving layer.

(Formation of glossy layer)
Next, 100 parts of spherical colloidal silica (Snowtex ST-XL, manufactured by Nissan Chemical Industries, Ltd.) as a pigment, 10 parts by mass (solid content equivalent) of casein solution (casein: manufactured by Millennis) as a binder, and a mold release agent. As a result, 2 parts by mass of polyethylene wax (SN coat 243, manufactured by San Nopco Co., Ltd.) was added to water and sufficiently stirred to obtain a coating liquid for a glossy layer having a solid content concentration of 20% by mass. Subsequently, the coating liquid for the glossy layer is applied to the surface of the support on which the ink receiving layer is formed so as to have an absolute dry coating amount of 6 g / m ^{2 using an air knife coater.} did. In water, 1.0% calcium formate as a coagulant, 2.0% lactic acid as an organic acid, 5.0% polyamidine-based fixing material (HIMAX SC-700, manufactured by Hymo) as an ink fixing agent, and magnesium nitrate. 1.0% of magnesium was added, and aqueous ammonia was added to adjust the pH to 6.0 to obtain a coagulated solution. The coagulation liquid (solid content concentration of the coagulation liquid is 9.0%) is further applied to the coated surface of the glossy layer coating liquid so that the liquid coating amount is 30 g / m ^2, and then the coagulation treatment is performed. While the surface of the coated coating layer was in a wet state, it was pressure-bonded to a cast drum having a surface temperature of 105 ° C. to prepare a glossy paper for inkjet having a glossy surface.

(Example 2)
In Example 1, a glossy paper for inkjet was produced under the conditions described in Example 1 except that the blending amount of lactic acid in the coagulation liquid was changed from 2.0% to 1.5%.

(Example 3)
In Example 1, a glossy paper for inkjet was produced under the conditions described in Example 1 except that the blending amount of lactic acid in the coagulation liquid was changed from 2.0% to 4.0%.

(Example 4)
In Example 1, a glossy paper for inkjet was produced under the conditions described in Example 1 except that the blending amount of calcium formate in the coagulation liquid was changed from 1.0% to 0.5%.

(Example 5)
In Example 1, a glossy paper for inkjet was produced under the conditions described in Example 1 except that the blending amount of calcium formate in the coagulation liquid was changed from 1.0% to 3.0%.

(Example 6)
In Example 1, a glossy paper for inkjet was produced under the conditions described in Example 1 except that the blending amount of magnesium nitrate in the coagulation liquid was changed from 1.0% to 3.0%.

(Example 7)
In Example 1, a glossy paper for an inkjet was prepared under the conditions described in Example 1 except that magnesium nitrate in the coagulation liquid was changed to magnesium chloride.

(Example 8)
In Example 1, a glossy paper for an inkjet was prepared under the conditions described in Example 1 except that magnesium nitrate in the coagulation liquid was changed to calcium chloride.

(Example 9)
In Example 1, a glossy paper for an inkjet was prepared under the conditions described in Example 1 except that the lactic acid in the coagulation liquid was changed to malic acid.

(Example 10)
In Example 1, a glossy paper for an inkjet was prepared under the conditions described in Example 1 except that the lactic acid in the coagulation liquid was changed to citric acid.

(Comparative Example 1)
In Example 1, a glossy paper for an inkjet was prepared under the conditions described in Example 1 except that 2.0% of lactic acid in the coagulation liquid was changed to 0%.

(Comparative Example 2)
In Example 1, a glossy paper for inkjet was produced under the conditions described in Example 1 except that 1.0% of magnesium nitrate in the coagulation liquid was changed to 0%.

(Comparative Example 3)
In Example 1, a glossy paper for inkjet was produced under the conditions described in Example 1 except that 1.0% of calcium formate in the coagulation liquid was changed to 0%.

The following tests were carried out on the obtained glossy paper for inkjet, and the results are shown in Tables 1 and 2.

(1) Appropriate inkjet:
ISO standard image (ISO / JIS-SCID high-definition color digital standard image data, image name: portrait, image identification number: N1) is used with a dye ink dedicated inkjet printer (EP-803A: manufactured by Epson) and pigment ink. Printing was performed on the obtained glossy paper for inkjet using a dedicated inkjet printer (PX-G930: manufactured by Epson Corporation). The suitability of the inkjet was evaluated by visually observing the density and uniformity of the color material in the solid print portion of the printed image and the blurring of the image.
⊚: Both the dye and pigment ink dedicated inkjet printers have excellent inkjet suitability and can be put into practical use.
◯: Ink suitable for either or both of dye and pigment ink dedicated inkjet printers is slightly inferior, but it can be put into practical use.
Δ: Ink suitable for either or both of the dye and pigment ink dedicated inkjet printers is slightly inferior, but it can be put into practical use.
X: Ink suitable for either or both of dye and pigment ink dedicated inkjet printers is inferior and cannot be put into practical use.

(2) Discoloration:
The obtained glossy inkjet paper was stored in an air-exposed state at 23 ° C. and 50% RH for 2 months, and the degree of discoloration of the blank portion on the surface of the glossy inkjet paper was visually evaluated.
⊚: There is no discoloration on the surface of glossy paper for inkjet, and it can be put into practical use.
◯: There is almost no discoloration on the surface of glossy paper for inkjet, and it can be put into practical use.
Δ: The surface of the glossy paper for inkjet is slightly discolored, but it is not noticeable and can be put into practical use.
X: The surface of glossy paper for inkjet is discolored and cannot be put into practical use.

(3) Strength:
Using a Gakushin type fastness tester (manufactured by Tester Sangyo Co., Ltd.), the glossy surface of the glossy inkjet paper obtained under the condition of a load of 400 g was rubbed 20 times, and the degree of surface strength (scratch) was visually evaluated. ..
⊚: Can be put into practical use without any scratches or powder falling off.
◯: Practical use with almost no scratches or powder falling off.
Δ: There are slight scratches and powder falling, but they are not noticeable and can be put into practical use.
×: Scratches and powder fall are conspicuous and cannot be put into practical use.

(4) Blank page feeling:
The blank surface feeling of the glossy layer was visually confirmed and evaluated according to the following criteria.
⊚: There are no foreign substances or stains, and the white surface feels very good, so it can be put into practical use.
〇: Although a small amount of foreign matter and dirt are generated, it has an excellent blank surface feeling and can be put into practical use.
Δ: Foreign matter and dirt are generated, but it has an excellent blank surface feeling and can be put into practical use.
X: Defects due to foreign matter and dirt occur, and the feeling of blank paper is inferior, making it impractical.

As is clear from Tables 1 and 2, in Examples 1 to 10, the glossy layer contains an organic acid, an inorganic metal salt, and calcium formate as a coagulant, and is more suitable for inkjet than Comparative Examples 1 to 3. It was excellent in discoloration, strength and surface feeling.

On the other hand, the glossy paper for inkjet obtained in Comparative Example 1 could not be put into practical use in terms of discoloration. This is thought to be due to the fact that no organic acid was added.

The glossy paper for inkjet obtained in Comparative Example 2 could not be put into practical use in terms of proper inkjet. It is considered that this is because the inorganic metal salt was not mixed.

The glossy paper for inkjet obtained in Comparative Example 3 could not be put into practical use in terms of proper inkjet, strength, and surface quality. This is thought to be due to the fact that calcium formate was not added.

Claims (5)

In an inkjet glossy paper having a glossy layer containing a pigment and a binder as main components on at least one surface of the base paper, the glossy layer contains an organic acid, an inorganic metal salt, and calcium formate as a coagulant. A glossy paper for inkjet that is characterized by this. The glossy paper for an inkjet according to claim 1, wherein the organic acid is lactic acid. The glossy paper for an inkjet according to claim 1 or 2, wherein the glossy layer contains an ink fixing agent. A method for producing a glossy paper for inkjet, which has a glossy layer containing a pigment and a binder as main components on one surface of the base paper.
A step of preparing a base paper, a step of applying a coating liquid for a glossy layer containing the pigment and a binder as main components on at least one surface of the base paper, an organic acid, an inorganic metal salt, and A coagulation liquid containing calcium formate as a coagulant is applied while the glossy layer is in a wet state to perform a coagulation treatment, and then is pressed against a heated cast drum to give a strong gloss finish. A characteristic method for producing glossy paper for inkjet. The method for producing glossy paper for an inkjet according to claim 4, wherein the pH of the coagulating liquid is 4.0 to 9.0.