JP2006248121A - Inkjet recording sheet - Google Patents

Abstract

Provided is an ink jet recording sheet that achieves both the preservability of a printing portion and the preservability of a blank paper portion and satisfies various required characteristics of an ink jet recording sheet.
An ink jet recording sheet provided with an ink receiving layer on at least one surface side of a support has an undercoat layer containing at least a pigment and an adhesive between the support and the ink receiving layer. The ink jet recording sheet, wherein the undercoat layer contains titanium dioxide as a pigment, and the ink receiving layer contains a hindered amine compound and / or a hindered phenol compound as a weather resistance improver.
[Selection figure] None

Description

  The present invention relates to an inkjet recording sheet.

  The ink jet recording system that ejects water-based ink from fine nozzles toward the surface of the recording body and forms an image on the surface of the recording body has low noise during recording, easy formation of full-color images, and high-speed recording The printer is widely used in printers, facsimiles, plotters, form printing, and the like because of the fact that it is possible and the recording cost is lower than other printing apparatuses.

This water-based ink is classified into a dye ink using a dye and a pigment ink using a pigment, and the dye ink is mainly used from the viewpoint of sharpness. In recent years, however, inkjet recording systems have also been used for large-sized posters for outdoor exhibitions. Therefore, dye inks are oxidized by ultraviolet rays, ozone, etc. when displayed for a long time, and the images fade and the appearance deteriorates. As a result, a drawback that sufficient storage stability of the printed portion cannot be obtained has been pointed out.
On the other hand, the pigment ink has the characteristics of excellent light resistance of the printed part, ozone resistance of the printed part, and water resistance of the printed part. Due to the large size, there is a problem that when a conventional ink jet recording sheet for dye ink is printed with pigment ink, a clear printed image cannot be obtained.
Therefore, ink jet recording sheets for dye inks and ink jet recording sheets for pigment inks have been developed. However, there is a strong demand for ink jet recording papers having good color developability for both dye inks and pigment inks. It was.
In addition to improving the storability of the print area, the storability of the white background (blank area), that is, the whiteness is maintained well over time and environmental conditions due to storage and use of inkjet recording paper and inkjet recordings. It has also become important to do. Since the recorded matter is composed of a print portion and a blank paper portion, in order to keep the print clearly identifiable, the whiteness of the blank paper portion and its preservability are excellent after satisfying the above-described color development. Because is required.

As a means for improving the storage stability (light resistance, ozone resistance) of the printed part when printing with dye ink, the ink receiving layer contains a hindered amine compound or the like (for example, see Patent Documents 1 to 16), Etc. have been proposed.
JP 7-314882 A JP-A-12-62310 JP-A-11-170686 JP-A-12-263918 JP-A-12-280601 JP-A-12-280611 Japanese Patent Laid-Open No. 13-88431 Japanese Patent Laid-Open No. 13-121807 Japanese Patent Laid-Open No. 13-270219 JP 2002-127596 A JP 2002-137535 A JP 2002-144699 A JP 2002-211110 A Japanese Patent Laid-Open No. 2002-240421 JP 2003-182205 A JP 2004-358825 A

  However, as in the inkjet recording papers described in Patent Documents 1 to 16, the method containing a hindered amine compound or the like has a certain effect on the storage stability (light resistance and ozone resistance) of the printed portion, but is blank. This is a situation where no improvement has been made to the shelf life of the department. In other words, the hindered amine compound contained in the inkjet recording sheet itself is deteriorated in the clear file or tape when it is put in a clear file or a tape is applied to preserve the inkjet recording sheet and its recorded material. Since the yellowing occurs due to an inhibitor (for example, a phenolic antioxidant), there is a problem that the sheet for ink jet recording and the recorded matter cannot be stored for a long period of time.

  The present invention has been made in view of the above circumstances, and achieves both storage stability (light resistance and ozone resistance) of a printing portion and storage stability (file yellowing resistance) of a blank paper portion, and various ink jets. The present invention provides an ink jet recording sheet that satisfies the required characteristics of a recording sheet.

As a result of intensive studies, the present inventors have provided an undercoat layer containing titanium dioxide between the support and the ink receiving layer containing a hindered amine compound and / or a hindered phenol compound, whereby The present inventors have found that the problems can be solved and have completed the present invention.
That is, the present invention
(1) In an ink jet recording sheet provided with an ink receiving layer on at least one surface side on a support, the substrate has an undercoat layer containing at least a pigment and an adhesive between the support and the ink receiving layer, The undercoat layer contains titanium dioxide as a pigment, and the ink receiving layer contains a hindered amine compound and / or a hindered phenol compound as a weather resistance improver.
(2) The ink jet recording sheet according to (1), wherein the weather resistance improver further contains an ultraviolet absorber.
(3) The inkjet recording sheet according to (1) or (2), wherein the ink receiving layer contains at least one water-soluble metal salt selected from zinc sulfate, zinc chloride, magnesium sulfate, and magnesium chloride. It is.

  The present invention has been made in view of the above circumstances, and achieves both storage stability (light resistance and ozone resistance) of a printing portion and storage stability (file yellowing resistance) of a blank paper portion, and various ink jets. An ink jet recording sheet satisfying the required characteristics of the recording sheet can be provided.

  The present invention is for ink jet recording that satisfies both the storage characteristics (light resistance and ozone resistance) of the printing section and the storage characteristics of the blank paper section (file yellowing resistance) and satisfies the required characteristics of various ink jet recording sheets. In order to achieve a sheet, an undercoat layer containing at least a pigment and an adhesive is provided between a support and an ink receiving layer, the undercoat layer contains titanium dioxide as a pigment, and the ink receiving layer has a weather resistance. An ink jet recording sheet comprising a hindered amine compound and / or a hindered phenol compound as a property improver.

  For example, as described in Japanese Patent Application Laid-Open No. 2003-182205 (Patent Document 15) and the like, it is known to use a hindered amine compound and a hindered phenol compound as a weather resistance improver for a printing portion. However, when an ink jet recording sheet containing these compounds is posted for a long time indoors or the like, it causes yellowing of the white paper portion. In particular, when an inkjet recording sheet is placed in a clear file or a tape is pasted and stored for a long time, the sheet easily becomes yellowed. That is, there is a problem that even if the storability of the printing part is improved by the hindered amine compound and / or the hindered phenol compound, it cannot withstand long-term storage and posting.

  The present invention contains titanium dioxide as a pigment in the undercoat layer, and contains a hindered amine compound and / or a hindered phenol compound in the ink receiving layer, whereby high whiteness is obtained in the white paper portion, and Excellent shelf life can be obtained. The reason why this effect can be obtained is considered as follows.

The cause of yellowing is considered to be due to oxidation of the hindered amine compound and the hindered phenol compound itself. In other words, in the case of indoor posting, the oxidation of the hindered amine compound and the hindered phenol compound itself is promoted by light and ozone, and if they are stored in a clear file or taped, the deterioration contained in these It is considered that an inhibitor (for example, a phenolic antioxidant) promotes oxidation / yellowing.
When an inkjet recording sheet or recorded material is stored in a clear file for a long period of time or pasted with a tape, the deterioration inhibitor volatilizes from the clear file or tape and adheres to the surface of the ink receiving layer. The oxidation yellowing of the hindered amine compound and / or the hindered phenol compound is promoted, and the phenolic antioxidant itself is also yellowed. As a result, the ink jet recording sheet or its recorded material turns yellow. .

In the present invention, by providing an undercoat layer containing titanium dioxide as a pigment between the support and the ink-receiving layer containing a hindered amine compound and / or a hindered phenol compound, phenolic antioxidant can be prevented from a clear file or the like. Even when the agent deterioration preventing agent adheres to the surface of the ink-receiving layer, the hindered amine compound and / or hindered phenol compound can be prevented from yellowing due to the light / water / gas shielding effect of titanium dioxide. it is conceivable that.
As a result, both the storability of the printing portion and the storability of the blank paper portion are improved, and storage and posting over a long period of time becomes possible.
In addition, by providing an undercoat layer containing titanium dioxide, it is possible to suppress the oxidation and yellowing of the phenolic antioxidant that volatilizes and adheres from clear files, etc., and is one of the causes of yellowing of inkjet recording sheets. It is also possible to suppress oxidation and yellowing of the cationic ink fixing agent.

  In order to prevent oxidation and yellowing of the hindered amine compound and the hindered phenol compound itself, the present invention is characterized by providing an undercoat layer containing titanium dioxide as a pigment. If a titanium dioxide is contained in the ink receiving layer without providing an undercoat layer, there is a certain effect in preventing yellowing of the blank paper portion, but the printing color developability and ink absorbability are very poor. Further, when the hindered amine compound and the hindered phenol compound are not contained in the ink receiving layer, and the hindered amine compound and the hindered phenol compound are contained in the undercoat layer, the effect of improving the weather resistance of the printed portion cannot be expected.

(Layer structure)
The present invention is an ink jet recording sheet in which an undercoat layer and an ink receiving layer are provided on at least one surface side of a support.
In the present invention, the same undercoat layer and ink receiving layer may be provided on the other side of the support. In this case, the effect of the present invention can be exhibited on both sides of the inkjet recording sheet.
Each of the undercoat layer and the ink receiving layer may be composed of a plurality of layers. At this time, the ink receiving layer is located on the outermost side with respect to the support and the undercoat layer.

(Support)
The support used in the present invention is not particularly limited as long as it can be used as a normal ink jet recording sheet. Fine paper, art paper, coated paper, cast coated paper, foil paper, craft Paper such as paper, baryta paper, impregnated paper, vapor-deposited paper, resin film, synthetic paper, non-woven fabric, etc., or resin film bonded to coated paper or fine paper with adhesive, or resin to paper A resin-coated paper such as a laminated one is used. In particular, the effect can be expected when applied to a paper base material mainly composed of pulp having poor storage stability.

  Since the ink jet recording sheet of the present invention has an undercoat layer containing a specific material, usually used recycled paper or mechanical pulp, which is refrained from use as a pulp of the ink jet recording sheet, may be blended with a paper base material. In addition, it is possible to obtain an ink jet recording sheet that is excellent in storage stability of a white paper portion and has a high whiteness.

Note that starch, polyvinyl alcohol, cationic resin, or the like can be coated and impregnated on the surface by a size press or the like to adjust surface smoothness, improve strength, printability, and writing ability. Furthermore, in order to improve the smoothness of the paper substrate, it is possible to perform a smoothing process by a calendar method or the like. The basis weight of the support is not particularly limited, but is about ²⁰ to 400 g / m ² .

(Undercoat layer)
[Pigment]
The undercoat layer in the present invention contains a pigment and an adhesive, and contains titanium dioxide as a pigment as described above.
Titanium dioxide is classified into a rutile type and an anatase type depending on the difference in structure. Generally, the rutile type is preferable because it can obtain higher whiteness, but both types are effective in the present invention. The secondary particle diameter of titanium dioxide is preferably 0.1 μm to 2 μm, and more preferably 0.3 μm to 1 μm. If the particle size is small, the strength tends to decrease, the ink absorbency decreases, and the color developability tends to decrease.If the particle size is large, the sharpness of the image tends to decrease, and a smooth and uniform surface is obtained. I can't.

  Furthermore, when titanium dioxide is used as a pigment for the undercoat layer, for example, even when used recycled paper pulp is used as a paper base material, there is an advantage that high whiteness can be obtained and a clear printed image can be obtained. .

  In the undercoat layer, as long as the effects of the present invention are not impaired, for example, silica, calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, Inorganic pigments such as calcium silicate, magnesium silicate, aluminum hydroxide, alumina, pseudoboehmite, lithopone, zeolite, hydrous halloysite, magnesium carbonate, magnesium hydroxide can be blended.

[adhesive]
The undercoat layer in the present invention contains an adhesive.
The adhesive is not particularly limited, and examples thereof include proteins such as casein, soybean protein, and synthetic protein, various starches such as starch and oxidized starch, polyvinyl alcohol and derivatives thereof, and cellulose such as carboxymethylcellulose and methylcellulose. Emulsion adhesion such as water-soluble resins such as derivatives, acrylic polymers, ethylene-vinyl acetate copolymers, vinyl acetate polymers, and conjugated diene resins of styrene-butadiene resins and methyl methacrylate-butadiene copolymers Conventionally known adhesives generally used for inkjet recording, such as an agent, can be used. Among these, it is preferable to use a combination of at least one emulsion adhesive selected from acrylic polymers, ethylene-vinyl acetate copolymers, and vinyl acetate polymers.

Examples of the acrylic polymer include polymers containing (meth) acrylic units such as acrylic acid, methacrylic acid, acrylic acid ester, and methacrylic acid ester. The acrylic polymer may be a homopolymer of (meth) acrylic units, a copolymer, or a copolymer containing other structural units. Examples of the acrylic polymer include polymethyl (meth) acrylate.
As the ethylene-vinyl acetate copolymer, ethylene and vinyl acetate are the main components, and as other monomers, for example, (meth) acrylic esters such as 2-ethylhexyl acrylate, vinyl acetate such as vinyl versatate Examples thereof include those obtained by copolymerizing a monomer containing a functional group such as acrylic acid vinyl, and acrylic acid.
The vinyl acetate polymer may be a polymer containing vinyl acetate units, and polyvinyl acetate is preferable.

  Note that conjugated diene resins such as styrene-butadiene resin and methyl methacrylate-butadiene copolymer as adhesives tend to have poor color developability, and tend to cause yellowing of the white paper portion over time. Also, when using a water-soluble adhesive such as starch or polyvinyl alcohol, when adjusting the coating liquid for the undercoat layer, it cannot be adjusted to a high-concentration coating liquid. It tends to be difficult to achieve whiteness, storage stability of the white paper portion, and print density. When these adhesives are used, it is preferable not to use them alone but to use them as subcomponents.

  The mixing ratio of the pigment and the adhesive is about 2 to 30 parts by mass, preferably about 5 to 20 parts by mass with respect to 100 parts by mass of the pigment. If the amount of the adhesive is small, the strength of the undercoat layer is lowered. On the other hand, if the amount of the adhesive is large, the ink absorption amount is lowered, the color developability of the printed portion is deteriorated and the whiteness tends to be lowered.

[Other ingredients]
Further, in the undercoat layer, a thickener, an antifoaming agent, a wetting agent, a coloring agent, a fluorescent whitening agent, a fluorescent pigment, a charging agent, which are used in general coated paper production, as long as the effects of the present invention are not impaired. Various assistants such as an inhibitor, a light resistance assistant, an ultraviolet absorber, an antioxidant and a preservative are appropriately added.
The undercoat layer can be formed by applying the undercoat layer coating solution containing the pigment, adhesive, and, if desired, an inorganic pigment to the surface of the paper substrate and drying it. The coating amount (solid content) of the undercoat layer is about 3 to ²⁰ g / m ² , preferably 5 to 15 g / m ² , more preferably 7 to 13 g / m ² . If the coating amount is too small, high whiteness cannot be obtained, and yellowing tends to occur. If the coating amount is excessive, the effect is saturated and the interlayer strength tends to be weakened.

  As the coating apparatus for forming the undercoat layer, various known coating apparatuses such as a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a rod blade coater, a lip coater, a curtain coater, and a die coater. Can be mentioned. After coating, it may be finished using a calendar such as a machine calendar, a TG calendar, a super calendar, or a soft calendar.

(Ink receiving layer)
The ink receiving layer has a pigment and an adhesive, and further contains a hindered amine compound and / or a hindered phenol compound as a weather resistance improver as described above.

[Weather resistance improver]
The hindered amine compound used in the ink receiving layer as a weather resistance improver is a compound having a site having a hindered amine structure in the molecule, and examples thereof include those described in JP-A No. 2003-182205. A typical compound is a derivative of 2,2,6,6-tetramethylpiperidine having a structure in which all hydrogens on the 2nd and 6th carbons of piperidine are substituted with methyl groups. Specifically, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 1- (3,5-di-tert-butyl-4-hydroxyphenylpropionyloxyethyl) -4- (3,5 -Di-tert-butyl-4-hydroxyphenylpropionyloxy) -2,2,6,6-tetramethylpiperidine and the like. These hindered amine compounds may be used alone or in combination of two or more.

  The hindered phenol compound used in the ink receiving layer as a weather resistance improver is preferably one having at least three phenolic hydroxyl groups in one molecule, but is not limited to this, and is not limited to this. Examples of the compound include triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert- Butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine, pentaeryth Lithyl tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,2- O-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1, 3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-tert-butyl-4-hydroxybenzyl)- Examples include isocyanurate and octylated diphenylamine. These hindered phenol compounds may be used alone or in combination of two or more.

  Usually, these hindered amine compounds and hindered phenol compounds are available as water-insoluble liquids or solids (powder), and water dispersions. When liquid or powder is used for an ink jet recording sheet, a suspension or emulsified water is used as a solvent. Generally, a hindered amine compound is more preferably used because it is easily suspended and emulsified using water as a solvent.

  In the present invention, it is preferable to further use an ultraviolet absorber typified by a benzophenone compound or a benzotriazole compound as a weather resistance improver because the light resistance and ozone resistance of the printed portion are further improved.

  As a compounding quantity of a weather resistance improver, a weather resistance improver is about 1-20 mass parts with respect to 100 mass parts of pigments, Preferably it is about 2-10 mass parts. If the amount of the weather resistance improver is small, sufficient weather resistance improvement effect cannot be obtained. Various adverse effects such as deterioration of color developability of the printed portion may occur.

[Pigment]
Pigments contained in the ink receiving layer are silica (dry, wet, colloidal silica), aluminum oxide, pseudoboehmite alumina silicate, kaolin, clay, calcined clay, zinc oxide, tin oxide, magnesium sulfate, aluminum hydroxide, calcium carbonate, Satin white, aluminum silicate, smectite, zeolite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, urea resin plastic pigment, etc. Use a mixture of more than one species.

  The kind of the pigment is not particularly limited, but among the pigments, silica, alumina, and pseudoboehmite are preferably selected from the viewpoint of color developability and ink absorbability, and wet silica is the best.

[adhesive]
The adhesive is not particularly limited, and is a water-soluble adhesive such as starch or polyvinyl alcohol, an acrylic polymer, an ethylene-vinyl acetate copolymer, a vinyl acetate polymer, a urethane polymer, or styrene. -Conventionally known adhesives generally used for inkjet recording, such as butadiene copolymers or emulsion type adhesives thereof. These may use only 1 type and may use 2 or more types of adhesives together.
Of these, an emulsion adhesive of acrylic polymer is preferable. Examples of the acrylic polymer include polymers containing (meth) acrylic units such as acrylic acid, methacrylic acid, acrylic acid ester, and methacrylic acid ester. The acrylic polymer may be a homopolymer of (meth) acrylic units, a copolymer, or a copolymer containing other structural units. Examples of the acrylic polymer include polymethyl (meth) acrylate.

In addition, it is preferable to use polyvinyl alcohol together with an acrylic polymer emulsion-type adhesive because of good adhesion to the pigment.
As the polyvinyl alcohol, polyvinyl alcohol derivatives such as silanol-modified polyvinyl alcohol and cationized polyvinyl alcohol can also be used as appropriate.
In addition, when using together an acrylic polymer and polyvinyl alcohol or its derivative (s), it is preferable to use together by the ratio of 1: 10-2: 1, and it is more preferable to use together by the ratio of 1: 5 to 1: 1.
The content of the adhesive is preferably 1 to 50 parts by mass and more preferably 5 to 40 parts by mass with respect to 100 parts by mass of silica.

In general, many adhesives such as emulsion type adhesives and water-soluble adhesives are known as adhesives. However, as a result of intensive studies, when acrylic polymer emulsion type adhesives are used, printing can be performed using either dye ink or pigment ink. However, it is preferable because a clear image can be obtained and the storability of the blank paper portion is excellent.
By the way, ethylene-vinyl acetate copolymer, vinyl acetate polymer, urethane polymer, styrene-butadiene copolymer, etc., which are typical emulsion type adhesives used for inkjet recording sheets, Are also inferior to acrylic polymers in terms of printing color, and urethane polymers and styrene-butadiene copolymers have a problem in that the white paper portion is easily yellowed and inferior in storage stability. .
In addition, when only water-soluble adhesives such as starch and polyvinyl alcohol are used, sufficient coating strength cannot be obtained, and when preparing a coating solution for the ink receiving layer, it can be prepared to a high concentration coating solution. However, there is a problem that when the coating is performed, the coating amount is small and a clear image cannot be obtained.

[Cationic ink fixing agent]
In the present invention, it is preferable that a cationic ink fixing agent is contained in the ink receiving layer in order to obtain a clearer image.
The cationic ink fixing agent is not particularly limited,
1) Polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine or derivatives thereof,
2) Acrylic polymer having secondary amino group, tertiary amino group or quaternary ammonium group, 3) polyvinylamine, polyvinylamidine, 5-membered ring amidines,
4) Dicyan cationic resin represented by dicyandiamide-formalin copolymer,
5) Polyamine cationic resin represented by dicyandiamide-polyethyleneamine copolymer,
6) Dimethylamine-epichlorohydrin copolymer,
7) Diallyldimethylammonium-SO ₂ copolymer,
8) diallylamine salt-SO ₂ copolymer,
9) Dimethyl diallylammonium chloride polymer,
10) Polymer of allylamine salt,
11) Dialkylaminoethyl (meth) acrylate quaternary salt copolymer,
12) Acrylamide-diallylamine salt copolymer,
13) Commonly commercially available products such as aluminum salts such as polyaluminum chloride and polyaluminum acetate can be used, and they can be used alone or in combination of two or more.

  5-60 mass parts is preferable with respect to 100 mass parts of silica, and, as for the compounding quantity of a cationic ink fixing agent, More preferably, it adjusts in 20-50 mass parts. When the cationic ink fixing agent is less than 5 parts by mass, the color developability of the image and the storage stability of the printing part are liable to occur. When the cationic ink fixing agent exceeds 60 parts by mass, the ink absorbency decreases, printing unevenness, Decrease in image sharpness is likely to occur.

[Water-soluble metal salt]
In the present invention, when the ink receiving layer contains at least one water-soluble metal salt selected from zinc sulfate, zinc chloride, magnesium sulfate, and magnesium chloride, the color development of the printed portion is further improved, and the white paper portion This is preferable in order to prevent yellowing. Although these reasons are not clear, the water-soluble metal salt captures the ink more on the surface layer, so the color development of the printed portion is improved, and the water-soluble metal salt captures free radicals in the ink receiving layer and causes oxidation. I guess that the amount of material is reduced.

  The blending amount of the water-soluble metal salt is preferably about 1 to 30 parts by mass, more preferably about 2 to 15 parts by mass with respect to 100 parts by mass of the pigment. If the amount of the water-soluble metal salt is small, sufficient effects (improved printing portion color development and white paper yellowing prevention) cannot be obtained. On the other hand, if the amount of the water-soluble metal salt is large, the coating strength decreases and the printing portion Water resistance is likely to deteriorate.

[Other ingredients]
For the ink-receiving layer, thickeners, antifoaming agents, wetting agents, surfactants, colorants, antistatic agents, light fastness aids, UV absorbers, antioxidants used in general coated paper production Various auxiliary agents such as preservatives and preservatives are appropriately added.
In the ink jet recording sheet of the present invention, high whiteness can be realized without substantially including a fluorescent brightening agent in the ink receiving layer. Therefore, good storage stability of the white paper portion can be obtained.

Such an ink receptive layer is formed by applying an ink receptive layer coating solution containing the above-mentioned pigment, adhesive, weather resistance improver, and optionally a water-soluble metal salt, a cationic ink fixing agent, and an auxiliary agent on a support. It can be applied to the surface of the formed undercoat layer and dried.
Although the coating amount of the ink receiving layer is not particularly limited, it may preferably be 2 to 30 g / ^{m 2,} and more preferably, 5 to 20 g / ^{m 2.}
If the coating amount is less than the above lower limit, ink absorbency, image sharpness, and print storage stability tend to be lowered, and if the coating amount is larger than the above upper limit, the coating strength and image sharpness tend to be lowered.
The ink receiving layer may be composed of a plurality of layers as described above, and in this case, the ink receiving layer composition may be different between the layers.

  The ink receiving layer can be formed by various known coating apparatuses such as a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a rod blade coater, a lip coater, a curtain coater, and a die coater. After coating, finishing may be performed using a calendar such as a machine calendar, a super calendar, or a soft calendar. Furthermore, the glossiness can be increased by employing a so-called cast coating method in which the ink-receiving layer coating liquid is applied and then dried by being pressed against a mirror drum while in a wet state.

  In addition, the back surface (the surface on which the ink receiving layer is not formed) is provided with a synthetic resin layer, a coating layer composed of a pigment and an adhesive, an antistatic layer, etc. to prevent curling, impart printability, and / or feed / discharge. It is also possible to impart aptitude and the like. In addition, various other known processes such as adhesive processing, lamination of magnetic materials, and post-processing that imparts flame retardancy, heat resistance, water resistance, oil resistance, anti-slip properties, etc. are added to the back surface to add application suitability. Of course it is also possible.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an example are solid content except water, and show a mass part and mass%, respectively. Hereinafter, “secondary particle diameter” means an average secondary particle diameter.

Example 1
[Paper Base A]
Add 20 parts of light calcium carbonate to a slurry of 100 parts of hardwood bleached kraft pulp (freeness 400 ml CSF), add 1 part of cationic starch, 0.2 part of alkenyl succinic anhydride neutral sizing agent, Mix and use as a papermaking raw material, dry up to 10% water using a long mesh multi-cylinder paper machine, apply a 7% solution of oxidized starch at 4 g / m ² on both sides with a size press, dry, and up to 7% water A paper base A having a weight of 200 g / m ² was produced by drying.

[Undercoat layer coating liquid A]
Titanium dioxide as a pigment (manufactured by Sakai Chemical Co., Ltd., trade name: R-21, secondary particle size 0.5 μm, rutile type) 100 parts, acrylic polymer (made by Rohm and Haas, trade name: Primal P as an adhesive) -376, 10 parts of emulsion type adhesive) and 5 parts of oxidized starch (trade name: Ace A, water-soluble adhesive, manufactured by Oji Cornstarch Co., Ltd.) were dispersed in water to obtain an undercoat layer coating liquid A.

[Ink-receiving layer coating solution A]
10 parts of a hindered amine compound (Asahi Denka Kogyo Co., Ltd., trade name: ADK STAB LX-335) as a weather resistance improver, and wet silica (trade name: Fine Seal X-60, produced by Tokuyama Co., Ltd.) as a pigment; 2 parts) 100 parts, 20 parts silyl-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd.) and 20 parts acrylic polymer (trade name: Primal P-376, manufactured by Rohm and Haas Co.) as an adhesive, cation 30 parts of polydiallyldimethylammonium chloride (trade name: Unisense CP101, manufactured by Senka Co., Ltd.) as a water-soluble ink fixing agent, and an aqueous zinc sulfate solution (manufactured by Wako Pure Chemical Industries, Ltd., zinc sulfate heptahydrate) as water-soluble metal salt 10 parts of a molecular weight of 287.56) was dispersed in water to obtain an ink-receiving layer coating liquid A.

[Preparation of inkjet recording sheet]
After coating and drying the undercoat layer coating solution A on the paper substrate A so that the coating amount is 10 g / m ² , the ink receiving layer coating solution A is applied with a coating amount of 10 g / m ² . Coating and drying were carried out to prepare an ink jet recording sheet.

(Example 2)
[Paper Base B]
20 parts of light calcium carbonate is added to a mixed slurry of 70 parts of hardwood bleached kraft pulp (freeness 400 ml CSF) and 30 parts of deinked pulp (new freeness 250 ml CSF), 1 part of cationic starch, anhydrous Add 0.2 part of alkenyl succinic acid neutral sizing agent, mix well to make papermaking raw material, dry the water to 10% using a long mesh multi-cylinder paper machine, % Solution was applied to both sides at 4 g / m ² , dried, and dried to a moisture content of 7% to produce a paper base B having a weight of 200 g / m ² .

[Preparation of inkjet recording sheet]
An ink jet recording sheet was prepared in the same manner as in Example 1 except that the paper substrate A in Example 1 was changed to the paper substrate B.

(Example 3)
[Ink-receiving layer coating solution B]
10 parts of a hindered amine compound (Asahi Denka Kogyo Co., Ltd., trade name: ADK STAB LX-335) as a weather resistance improver, and wet silica (trade name: Fine Seal X-60, produced by Tokuyama Co., Ltd.) as a pigment; 2 parts) 100 parts, 20 parts silyl-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd.) and 20 parts acrylic polymer (trade name: Primal P-376, manufactured by Rohm and Haas Co.) as an adhesive, cation 30 parts of polydiallyldimethylammonium chloride (manufactured by Senka Co., Ltd., trade name: Unisense CP101) was dispersed in water as a conductive ink fixing agent to obtain an ink-receiving layer coating solution B.

[Preparation of inkjet recording sheet]
An ink jet recording sheet was prepared in the same manner as in Example 2 except that the ink receiving layer coating liquid A in Example 2 was changed to the ink receiving layer coating liquid B.

Example 4
[Ink-receiving layer coating solution C]
10 parts of hindered phenolic compound (Asahi Denka Kogyo Co., Ltd., trade name: ADK STAB LX-802) as a weather resistance improver, wet silica (trade name: Fine Seal X-60, produced by Tokuyama Co., Ltd.) as a pigment, secondary particle size 6.2 parts) 100 parts, 20 parts silyl-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd.) and 20 parts acrylic polymer (trade name: Primal P-376, manufactured by Rohm and Haas) , 30 parts of polydiallyldimethylammonium chloride (Senka, trade name: Unisense CP101) as a cationic ink fixing agent, zinc sulfate aqueous solution (made by Wako Pure Chemical Industries, Ltd., zinc sulfate heptahydrate as water soluble metal salt) 10 parts of a molecular weight of 287.56) were dispersed in water to obtain an ink-receiving layer coating solution C.

[Preparation of inkjet recording sheet]
An ink jet recording sheet was prepared in the same manner as in Example 2 except that the ink receiving layer coating liquid A in Example 2 was changed to the ink receiving layer coating liquid C.

(Example 5)
[Ink-receiving layer coating solution D]
As a weather resistance improver, 5 parts of a hindered phenol compound (Asahi Denka Kogyo Co., Ltd., trade name: ADK STAB LX-802) and a benzotriazole UV absorber (Asahi Denka Kogyo Co., Ltd., trade name: ADK STAB LX-301) 5 Part, wet silica (trade name: Fine Seal X-60, secondary particle diameter 6.2 μm) 100 parts as pigment, silyl modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd.) as adhesive 20 parts and 20 parts of an acrylic polymer (Rohm and Haas, trade name: Primal P-376), 30 parts of polydiallyldimethylammonium chloride (Senka, trade name: Unisense CP101) as a cationic ink fixing agent, Zinc sulfate aqueous solution (made by Wako Pure Chemical Industries, Ltd., zinc sulfate heptahydrate dissolved in water as a water-soluble metal salt. And used as a 5%, molecular weight 287.56) were dispersed 10 parts of water to obtain an ink-receiving layer coating solution D.

[Preparation of inkjet recording sheet]
An ink jet recording sheet was prepared in the same manner as in Example 2 except that the ink receiving layer coating liquid A in Example 2 was changed to the ink receiving layer coating liquid D.

(Comparative Example 1)
[Preparation of inkjet recording sheet]
On the paper base material B, the ink receiving layer coating liquid A was applied and dried so that the coating amount was 10 g / m ² , thereby preparing an ink jet recording sheet having no undercoat layer.

(Comparative Example 2)
[Ink-receiving layer coating solution E]
Wet silica (trade name: Fine Seal X-60, secondary particle size 6.2 μm) 100 parts as pigment, 20 parts silyl-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd.) as adhesive And 20 parts of an acrylic polymer (Rohm and Haas, trade name: Primal P-376) and 30 parts of polydiallyldimethylammonium chloride (Senka, trade name: Unisense CP101) as a cationic ink fixing agent in water. Dispersion was performed to obtain an ink-receiving layer coating solution E.

[Preparation of inkjet recording sheet]
An ink jet recording sheet was prepared in the same manner as in Example 2 except that the ink receiving layer coating liquid A of Example 2 was changed to the ink receiving layer coating liquid E.

(Comparative Example 3)
[Preparation of inkjet recording sheet]
On the paper base material B, the ink receiving layer coating liquid E was applied and dried so that the coating amount was 10 g / m ² , thereby preparing an ink jet recording sheet having no undercoat layer.

(Comparative Example 4)
[Undercoat layer coating solution B]
Wet silica (trade name: Fine Seal X-60, secondary particle size 6.2 μm) 100 parts as pigment, acrylic polymer (Rohm and Haas, trade name: Primal P-376) as adhesive 10 parts of emulsion type adhesive) and 5 parts of oxidized starch (manufactured by Oji Cornstarch Co., Ltd., trade name: Ace A, water-soluble adhesive) were dispersed in water to obtain an undercoat layer coating liquid B.

[Preparation of inkjet recording sheet]
An ink jet recording sheet was prepared in the same manner as in Example 2 except that the undercoat layer coating solution A was changed to the undercoat layer coating solution B.

(Comparative Example 5)
[Ink-receiving layer coating solution F]
10 parts of a hindered amine compound (Asahi Denka Kogyo Co., Ltd., trade name: ADK STAB LX-335) as a weather resistance improver, and wet silica (trade name: Fine Seal X-60, produced by Tokuyama Co., Ltd.) as a pigment; 2 parts) and 50 parts of titanium dioxide (manufactured by Sakai Chemical Co., Ltd., trade name: R-21, secondary particle size 0.5 μm, rutile type), silyl-modified polyvinyl alcohol (made by Kuraray, trade name: R) as an adhesive -1130) 20 parts and acrylic polymer (Rohm and Haas, trade name: Primal P-376), 20 parts of polydiallyldimethylammonium chloride (Senka, trade name: Unisense CP101) as a cationic ink fixing agent 30 parts were dispersed in water to obtain an ink receiving layer coating solution F.

[Preparation of inkjet recording sheet]
An ink jet recording sheet was prepared in the same manner as in Comparative Example 4 except that the ink receiving layer coating liquid A in Comparative Example 4 was changed to the ink receiving layer coating liquid F.

(Comparative Example 6)
[Undercoat layer coating solution C]
10 parts of a hindered amine compound (Asahi Denka Kogyo Co., Ltd., trade name: ADK STAB LX-335) as a weather resistance improver, and titanium dioxide (a trade name: R-21, Sakai Chemical Co., Ltd., trade name: 0.5 μm) as a pigment , Rutile type) 100 parts, acrylic polymer (made by Rohm and Haas, trade name: Primal P-376, emulsion type adhesive) 10 parts and oxidized starch (made by Oji Cornstarch, trade name: Ace A) as an adhesive , 5 parts of a water-soluble adhesive) was dispersed in water to obtain an undercoat layer coating solution C.

[Preparation of inkjet recording sheet]
An inkjet recording sheet was prepared in the same manner as in Comparative Example 2 except that the undercoat layer coating solution A was changed to the undercoat layer coating solution C.

(Comparative Example 7)
[Preparation of inkjet recording sheet]
On the paper base material B, the ink receiving layer coating liquid F was applied and dried so that the coating amount was 10 g / m ² , thereby preparing an ink jet recording sheet having no undercoat layer.

[Evaluation]
The whiteness of the ink jet recording sheet obtained in each Example and Comparative Example, storage stability of the white paper portion (file yellowing prevention, tape yellowing prevention), printing density, printing portion storage stability (light resistance, ozone resistance) ) Was evaluated by the following method.
In the evaluation, printing on the inkjet recording sheet is
Printer A: Commercially available dye ink jet printer (trademark: PIXUS iP8600, manufactured by Canon Inc., print mode: matte photo paper / clean),
Printer B: Commercially available pigment inkjet printer (manufactured by Epson, trademark: PX-G920, print mode: photomat paper / high definition),
Printer C: Commercially available pigment inkjet plotter (manufactured by Hewlett-Packard Company, trademark: DesignJet 5500PS, ink: pigment ink used, print mode: highest quality),
I went with three models.

[Whiteness]
The whiteness of the white paper portion on the ink receiving layer side of the ink jet recording sheet was measured according to the method defined in JIS-P8123.

[Preservation of blank pages (file yellowing prevention)]
The inkjet recording sheet was placed in a clear file (product number: 132CH manufactured by King Jim Co., Ltd.) and allowed to stand for 1 week in an environment of 40 ° C. and 80% RH (humidity). The hue b * value of the white paper portion on the ink receiving layer side of the sheet before and after standing was measured. For the measurement, a spectral whiteness colorimeter SC-10WN manufactured by Suga Test Instruments Co., Ltd. was used. Next, Δb * value was calculated according to the following equation.
Δb * value = | b * value after standing |-| b * value before standing |
The storability of the blank paper portion (file yellowing prevention) was evaluated according to the following criteria.
A: Δb * value is less than 3 and no yellowing occurs.
A: Δb * value is 3 or more and less than 6, and hardly yellowed.
Δ: Δb * value is 6 or more and less than 10, and yellowing occurs.
X: Δb * value is 10 or more, and very yellow.

[Preservation of blank paper part (tape yellowing prevention)]
A cellophane tape (manufactured by Nichiban Co., Ltd., product number: 4051P-24) is pasted on an ink jet recording sheet, and left to stand in an environment of 40 ° C. and 80% RH (humidity) for 1 week. The hue b * value of the white paper portion on the ink receiving layer side of the sheet after taking the tape, before and after standing, and after taking the tape was measured. For the measurement, a spectral whiteness colorimeter SC-10WN manufactured by Suga Test Instruments Co., Ltd. was used. Next, Δb * value was calculated according to the following equation.
Δb * value = | b * value after standing |-| b * value before standing |
The storage stability (tape yellowing) of the blank paper portion was evaluated according to the following criteria.
A: Δb * value is less than 3 and no yellowing occurs.
A: Δb * value is 3 or more and less than 6, and hardly yellowed.
Δ: Δb * value is 6 or more and less than 10, and yellowing occurs.
X: Δb * value is 10 or more, and very yellow.

[Print density]
Print the image ("High-definition color digital standard image XYZ / JIS-SCID", identification symbol: S6, image name: color chart) issued by the Japanese Standards Association with the above three models, The print density was measured with RD-914 manufactured by GretagMacbeth.

[Preservation of printed part (light resistance)]
Using a printer A, a commercially available image processing software with a magenta discharge rate adjusted to 80% and printed matter is irradiated with a xenon lamp with an illuminance of 100 Klux for 72 hours in an environment of 65 ° C and 40% RH (humidity). Then, the print density was measured.
The storage stability (light resistance) of the printed part was evaluated according to the following criteria.
○: Change in concentration is less than 20% △: Change in concentration is 20% or more and less than 30% ×: Change in concentration is 30% or more

[Preservation of printed part (ozone resistance)]
Using the printer A, the recorded matter printed by adjusting the magenta discharge amount to 80% with commercially available image processing software is left in an atmosphere of ozone at 2.5 ppm at 24 ° C. and 60% RH for 24 hours. The print density was measured.
The storage stability (ozone resistance) of the printed part was evaluated according to the following criteria.
○: Concentration change is less than 20% Δ: Concentration change is 20% or more and less than 30% ×: Concentration change is 30% or more

From the results of Table 1 above, Examples 1 to 5 in which the undercoat layer according to the present invention contains titanium dioxide as a pigment, and the ink receiving layer contains a hindered amine compound and / or a hindered phenol compound as a weather resistance improver. It has been found that the storability of the blank paper portion and the storability of the printing portion are compatible, and can be posted and stored for a long period of time, and is excellent in the required characteristics of the ink jet recording sheet.
Further, from Example 2 in which pulp obtained by deinking newspaper waste paper was mixed with the support and Example 1 in which pulp was not blended, the performance of the ink jet recording sheet can be maintained even when waste paper recycled pulp is used. found.
In particular, Example 2 containing a water-soluble metal salt improves the storability of the blank paper part, the storability of the printing part, and the print density, and improves the performance of the inkjet recording sheet, compared to Example 3 not containing the water-soluble metal salt. However, it turned out to be better.
Furthermore, it was found that Example 5 in which an ultraviolet absorber was used in combination as a weather resistance improver was superior to Example 2 in which no ultraviolet absorber was used in combination, in which the storability of the printed portion was superior.
On the other hand, in Comparative Example 1 having no undercoat layer, it was found that the storage stability of the blank paper portion was very poor and the whiteness of the blank paper portion was also poor.
The comparative example 2 which does not contain a hindered amine compound and / or a hindered phenol compound is inferior in storage stability of the printed part, does not have an undercoat layer, and does not contain a hindered amine compound and / or a hindered phenol compound. No. 3 was found to be inferior in the storage stability of the printed portion and the whiteness of the blank paper portion.
In Comparative Example 4 containing silica as a pigment for the undercoat layer, the storage stability of the blank paper portion is inferior, and in Comparative Examples 5 and 7 containing titanium dioxide in the ink receiving layer, the ink absorption may be very inferior. found.
It was proved that Comparative Example 6 in which the weather resistance improver was contained in the undercoat layer and was not contained in the ink receiving layer was inferior in the storability of the printed portion.

Claims (3)

An ink jet recording sheet provided with an ink receiving layer on at least one surface side of a support, and having an undercoat layer containing at least a pigment and an adhesive between the support and the ink receiving layer, the undercoat layer An ink jet recording sheet comprising titanium dioxide as a pigment and a hindered amine compound and / or a hindered phenol compound as a weather resistance improver in the ink receiving layer. 2. The ink jet recording sheet according to claim 1, wherein the ink receiving layer further contains an ultraviolet absorber. 3. The ink jet recording sheet according to claim 1, wherein the ink receiving layer contains at least one water-soluble metal salt selected from zinc sulfate, zinc chloride, magnesium sulfate, and magnesium chloride.