JP2006248154A - Inkjet recording paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording sheet which is excellent in curling aptitude and transportability, has high sheet passing accuracy, and can obtain a high-definition image free from banding.
In an inkjet recording paper having one or more ink-receiving layers containing at least a pigment and an adhesive provided on one side of a paper base on which pulp is made, a pigment is provided on the other side of the paper base. An ink jet recording paper comprising: a back surface layer containing alumina and / or alumina hydrate having an average secondary particle diameter of 1 μm or less and starch and / or starch-modified product as an adhesive.
[Selection figure] None

Description

  The present invention relates to an inkjet recording paper.

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.

  As the inkjet recording method has become more precise and faster, the application has been expanded and the environment in which it is used has also been expanded. Along with this, in addition to various basic characteristics such as ink absorbability, color development of the printed part and storage stability, ink jet recording paper also has excellent characteristics in handling properties such as curl suitability and transportability. It is becoming required.

  The occurrence of curling is caused by the difference in expansion and contraction between the front surface and the back surface of the ink jet recording sheet with respect to changes in temperature and humidity. In particular, when the base material of the inkjet recording sheet is a base material such as paper mainly composed of pulp, the hygroscopicity is higher than in the case of a base material such as a resin film or a resin-coated paper obtained by laminating a resin to paper. Since it is large, it is greatly affected by the change in humidity accompanying the change in temperature, and curling occurs.

  When the curl occurs, the print head and the inkjet recording sheet cannot be conveyed by the inkjet recording apparatus, which causes conveyance and printing failure. Therefore, as a means for preventing curling, a method of providing a coating layer containing an aluminosilicate on the opposite surface of the ink receiving layer (see, for example, Patent Document 1), an inorganic pigment and / or organic in the backing layer. A method of incorporating a pigment (for example, see Patent Document 2) has been proposed, but even if curling has a certain effect, it is not satisfactory in terms of improving the transportability.

  Passing the paper through the printer is the minimum necessary element for an inkjet recording sheet. However, with the recent progress of high-definition recording devices, even slight deviations in the conveyance can cause banding (horizontal stripes when printing). As a result, the printed image may be disturbed. In other words, the ink jet recording sheet is required not only to pass through the printer but also to be fed accurately.

  As means for improving printer transportability, a method of controlling the coefficient of friction between the ink receiving layer surface and the opposite surface thereof to a specific value (see, for example, Patent Documents 3 and 4), the average primary particle diameter on the opposite surface of the ink receiving layer A method of providing a back layer containing 5 to 50 nm of inorganic fine particles and a binder (see, for example, Patent Document 5), and a method of incorporating an inorganic pigment and / or an organic pigment in the backing layer (see, for example, Patent Document 2). ), A method in which colloidal silica is contained in the backing layer (for example, see Patent Document 6), a method in which talc having a particle size of 30 μm or less is contained in the back surface (for example, see Patent Document 7), and the other of the recording layer. A method of providing a back coating layer containing a fine pigment having an average particle diameter of 1 μm or less on the surface (see, for example, Patent Document 8) has been proposed.

However, these proposed transportability improving means have a certain effect on the continuous transportability of about several tens of sheets, but in order to cope with high-speed and large-scale printing recently required for the ink jet recording system, It is insufficient as an effect for continuous transportability of several hundred sheets. For example, the method of using colloidal silica on the back surface to make it easy to feed ink jet recording sheets with a paper feed roller is effective in the initial transportability, but if a large number of sheets are transported, the colloidal in the back surface layer Silica peels off and adheres to the paper feed roller, causing not only poor conveyance but also image disturbance due to poor paper feed. In order to prevent this, even if the adhesive in the back layer is increased, it becomes difficult to feed the paper by the paper feed roller (insufficient paper feed force), causing a conveyance failure.
Japanese Patent Laid-Open No. 2001-293952 Japanese Patent Laid-Open No. 2002-200838 JP 2003-159861 A JP-A-6-278357 Japanese Patent Laid-Open No. 2002-240417 JP 2003-251912 A JP 2004-338266 A JP 2000-6513 A

  In other words, the ink jet recording paper described in the above-mentioned patent document cannot be said to sufficiently satisfy the curl aptitude and the transportability, and does not easily curl even under various environments. Inkjet recording paper capable of obtaining a fine image has not been obtained.

  The present invention has been made in view of the above circumstances, and provides an ink jet recording sheet that is excellent in curling ability and transportability and that can obtain a high-definition image that does not cause banding or the like.

  As a result of intensive studies, the inventors of the present invention have provided an ink-jet recording paper in which one or more ink receiving layers containing at least a pigment and an adhesive are provided on one side of a base material. The back surface containing alumina and / or alumina hydrate having an average secondary particle diameter of 1 μm or less as a pigment and starch and / or starch modified material as an adhesive on the other surface (hereinafter also referred to as a back surface) of the material It has been found that the above problems can be solved by an ink jet recording paper having a layer, and the present invention has been completed.

That is, the present invention
(1) In an inkjet recording paper in which one or more ink-receiving layers containing at least a pigment and an adhesive are provided on one side of a paper base on which pulp is made, as a pigment on the other side of the paper base An ink jet recording paper comprising an alumina and / or alumina hydrate having an average secondary particle size of 1 μm or less, and a back layer containing starch and / or starch-modified product as an adhesive.
(2) The inkjet recording paper according to (1), wherein the ratio of the pigment and the adhesive is 10: 1 to 1: 1 in the back layer.
(3) The static friction coefficient (JIS P 8147) between the ink receiving layer surface and the back layer surface is 0.70 to 0.90, and the dynamic friction coefficient (JIS P 8147) between the ink receiving layer surface and the back layer surface is 0.60 to 0.85. The inkjet recording paper according to (1) or (2).

  According to the present invention, it is possible to provide an ink jet recording sheet that is excellent in curling ability and transportability and that can obtain a high-definition image that does not cause banding.

(Layer structure)
The present invention is an ink jet recording paper in which an ink receiving layer is provided on one side of a paper substrate, and a back layer is provided on the other side of the substrate. The ink receiving layer may be composed of a plurality of different layers.

(Paper substrate)
Examples of the pulp used as the main component of the paper base include chemical pulps such as LBKP and NLBKP, mechanical pulps such as GP and TMP, and recycled recycled paper. Two or more of these may be mixed and used. The beating degree is not particularly limited, but beating is preferably performed so that the freeness is about 200 to 500 ml (CSF: JIS-P-8121). If the freeness is small, cockling tends to deteriorate when printed, and if the freeness is large, smoothness tends not to be obtained.

In addition to the above pulp, a filler is blended in the paper base material. The filler is blended for the purpose of adjusting the air permeability of the paper substrate, imparting opacity, etc., or adjusting the ink absorbability. As the filler, for example, clay, kaolin, calcined kaolin, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, calcium hydroxide, silica, titanium oxide and the like can be used as appropriate. Among them, calcium carbonate is preferable because it becomes a paper base having high whiteness.
The filler is preferably 1 to 35 parts relative to 100 parts of the total pulp. If the amount of filler is small, not only will the whiteness decrease, but the ink absorbency will tend to decrease. If it is too large, paper stiffness (stiffness) will tend to decrease and paper strength will decrease. Mixing causes yellowing of the ink jet recording paper surface.

  Various types of anionic, nonionic, cationic or amphoteric steps that have been used in the past can be used in the paper stock containing the pulp and filler as long as the desired effects of the present invention are not impaired. Various internal additives for papermaking, such as a retention improver, a freeness improver, a paper strength enhancer, and an internal sizing agent, can be appropriately selected and used as necessary. Furthermore, internal additives for papermaking such as dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be added as necessary.

  As a papermaking method, it can be produced using a known papermaking machine such as a long net papermaking machine, a circular netting papermaking machine, or a twin wire type papermaking machine. Depending on the pH of the papermaking raw material, it can be divided into acidic paper and neutral paper. As the paper substrate used in the present invention, neutral paper is preferred in terms of long-term storage stability.

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 treatment with a calendar or the like. The basis weight of the paper substrate is not particularly limited, but is about ²⁰ to 400 g / m ² .

(Back layer)
The back layer in the present invention is an alumina and / or alumina hydrate having an average secondary particle size (average particle size of secondary particles; hereinafter, sometimes simply referred to as “average particle size”) of 1 μm or less as a pigment, It contains starch and / or starch-modified product as an adhesive.

[Pigment]
In the present invention, alumina and / or alumina hydrate having an average particle size of 1 μm or less is used as the pigment.
As the alumina, known alumina can be used, but γ-alumina which is a γ-type crystal of aluminum oxide is preferable. γ-alumina can make primary particles as small as about 10 nm, but in the case of the present invention, secondary particle crystals of several thousand to several tens of thousands nm can be obtained by ultrasonic waves, high-pressure homogenizers, opposed collision type jet crushers, etc. , And those pulverized to about 50 nm to 1 μm are preferable, and a more preferable particle size is 100 nm to 700 nm. When the average particle size is small, there is a possibility that it becomes difficult to feed the paper with a paper feed roller, and it is difficult to pass the paper accurately. Even if the average particle size is too large, there is a risk that it will be difficult to be fed by the paper feed roller, it will be difficult to pass the paper accurately, and the pigment tends to be peeled off from the back layer.

Alumina hydrate is represented by a constitutive formula of Al ₂ O ₃ .nH ₂ O (n = 1 to 3). The case where n is 1 represents an alumina hydrate having a boehmite structure, and the case where n is greater than 1 and less than 3 represents an alumina hydrate having a pseudo boehmite structure. It can be obtained by a known production method such as hydrolysis of an aluminum alkoxide such as aluminum isopropoxide, neutralization of an aluminum salt with an alkali, or hydrolysis of an aluminate. A suitable average particle diameter is the same as that of the above-mentioned alumina.

  In the present invention, by using alumina and / or alumina hydrate having an average particle diameter of 1 μm or less, preferably 50 nm to 1 μm, for the back layer, it is easy to be fed by a feed roller, and the sheet can be accurately fed even during printing. High-definition images can be obtained by printing at accurate positions. Further, it is preferable that the average particle diameter is uniform (that is, the particle size distribution is sharp). Furthermore, by using alumina and / or alumina hydrate, even if a large number of sheets are continuously fed, the paper can be stably fed.

  Incidentally, when synthetic silica such as wet silica or vapor phase method silica is used as the pigment of the back layer, even if the average particle diameter is 1 μm or less, a large number of sheets cannot be fed. Perhaps alumina and hydrated alumina have higher self-adhesion ability than silica, so the amount of adhesive added to the back layer can be reduced, the pigment performance can be fully demonstrated, and accurate paper feeding is possible. It becomes. In silica having a low self-adhesive ability, if the amount of the adhesive is small, the silica peels off from the back surface layer, and adheres to the paper feed roller, causing a conveyance failure. This is particularly noticeable when feeding many sheets. On the contrary, if the amount of the adhesive is increased, it is considered that it is difficult to feed the paper to the paper feed roller because the back surface layer has a large amount of adhesive, and the paper cannot be passed accurately.

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

[adhesive]
In the present invention, starch and / or starch-modified products are used as the adhesive. Although the role of the adhesive has the original role of retaining the pigment, the use of starch and / or starch-modified products has the effect of suppressing curl change with respect to environmental changes (improvement of environmental curl performance). When using starch and / or starch-modified products, the detailed reason is unknown, but curl fluctuation when the humidity environment changes can be reduced, preventing the adhesive itself from being damaged due to stress during coating, at low cost, The increase in viscosity can be suppressed and the coating accuracy can be increased.

As modified starch,
1) oxidized starch obtained by oxidation with an oxidizing agent such as sodium hypochlorite,
2) Acid-treated starch treated with hydrochloric acid or sulfuric acid,
3) Enzyme-treated starch,
4) Dialdehyde starch reacted with periodic acid,
5) Esterified starch such as acetylated starch, urea phosphorylated starch, phosphorylated starch,
6) Etherified starch such as hydroxyalkylated starch and carboxyalkylated starch,
7) Cationized starch,
8) Cross-linked starch such as formaldehyde cross-linked starch, epichlorohydrin cross-linked starch, phosphate cross-linked starch,
9) Graft-polymerized starch obtained by polymerizing starch with active sites formed with vinyl monomers such as acrylic acid, acrylonitrile, acrylamide, methacrylic acid ester, vinyl acetate and cyclic monomers such as epoxide, episulfide, imine, lactam,
Such as those commercially available, such as starch, may be used alone or in combination of two or more.

  In many cases, polyvinyl alcohol (hereinafter abbreviated as “PVA”) is used as an adhesive for the back surface layer, but PVA is sufficient as a role for adhesion, but the coating film containing PVA The curl tended to change easily with respect to the change. Probably, in a high humidity environment, the PVA absorbs moisture and swells, so it is considered that curling occurs.

In the case of cellulose derivatives and casein, the back layer paint tends to thicken, and since the back layer coating amount is usually 1 g / m ² or less and the coating amount is relatively low, the back layer paint is thickened. If it does, it will become difficult to adjust the coating amount, and curl control will become very difficult. In addition, the thickening of the paint also contributes to a decrease in workability such as difficulty in cleaning the coating head.

  In the case of water-dispersible resins such as conjugated diene resins such as acrylic polymers, ethylene-vinyl acetate copolymers, vinyl acetate polymers ethylene, styrene-butadiene resins, methyl methacrylate-butadiene copolymers, It is more expensive than PVA or starch or modified starch used in the present invention, and when coated with a roll coater or the like, the dispersion state of the water-dispersed resin is destroyed by the shearing force of the roll, and the water-dispersible resin is not effective. There is a problem of becoming stable.

  The present invention is within the range not inhibiting the effect of starch or starch modified product, for example, proteins such as casein, soybean protein, synthetic protein, PVA and its derivatives, cellulose derivatives such as carboxymethylcellulose and methylcellulose, styrene-butadiene Conventionally known adhesives generally used for inkjet recording, such as resins and conjugated diene resins of methyl methacrylate-butadiene copolymer, can be used in combination.

  In the back layer, the mixing ratio of the pigment and the adhesive is about 10 to 100 parts by mass, preferably about 20 to 50 parts by mass of the adhesive with respect to 100 parts by mass of the pigment. If the amount of the adhesive is small, the pigment is easily peeled off and causes a conveyance failure. On the other hand, if the amount of the adhesive is large, a conveyance failure is caused due to insufficient paper feeding force.

  Further, the back layer is provided with a thickener, an antifoaming agent, a wetting agent, a coloring agent, a fluorescent whitening agent, a fluorescent pigment, a charging agent, and the like, which are used in general coated paper production, as long as the effects of the present invention are not impaired. Various auxiliary agents such as an inhibitor, a light resistance auxiliary agent, an ultraviolet absorber, an antioxidant, an antiseptic agent, and an ink fixing agent are appropriately added.

The coating amount (solid content) of the back layer is about 0.2 to 1.0 g / m ² . If the coating amount is too small, the sheet feeding force will be insufficient. If the coating amount is excessive, the effect will be saturated, and the coating will be easily peeled off, which will cause conveyance failure. The amount of coating on the back layer necessary for curl control (the amount of coating) varies depending on the composition and coating amount of the ink receiving layer, the composition and thickness of the base material, etc. A back layer may be provided. The back layer is preferably formed after the ink receiving layer is formed because curling can be suppressed.

  As a coating apparatus for forming the back 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 contains at least a pigment and an adhesive.
[Pigment]
The pigment is not particularly limited, and silica (dry, wet, colloidal silica), aluminum oxide, pseudoboehmite alumina silicate, titanium dioxide, kaolin, clay, calcined clay, zinc oxide, tin oxide, magnesium sulfate, hydroxylated Various publicly known pigments in the general coated paper field such as aluminum, calcium carbonate, satin white, aluminum silicate, smectite, zeolite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, urea resin plastic pigment, etc. Are used alone or in admixture of two or more. Of these, silica, alumina, and pseudoboehmite are preferably selected from the viewpoints of color developability and ink absorbability, and wet silica is the best.

[adhesive]
The adhesive is not particularly limited, and proteins such as casein, soy protein, synthetic protein, PVA and derivatives thereof, starch and derivatives thereof, cellulose derivatives such as carboxymethylcellulose and methylcellulose, acrylic polymers, ethylene- Conventionally known adhesives generally used for inkjet recording, such as vinyl acetate copolymers, vinyl acetate polymers, urethane polymers, styrene-butadiene resins, conjugated diene resins of methyl methacrylate-butadiene copolymers, etc. An agent can be used in combination.

[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) an acrylic polymer having a secondary amino group, a tertiary amino group or a quaternary ammonium group,
3) polyvinylamine, polyvinylamidine, five-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) Aluminum salts such as polyaluminum chloride and polyaluminum acetate,
14) water-soluble metal salts,
And the like which are commercially available, such as, are 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.

  For the ink receiving layer, thickeners, antifoaming agents, wetting agents, surfactants, colorants, antistatic agents, fluorescent whitening agents, light fastness aids, UV rays used in general coated paper production Various auxiliary agents such as an absorbent, an antioxidant, and a preservative are appropriately added.

Such an ink receptive layer is formed by applying an ink receptive layer coating solution containing the above-mentioned pigment, adhesive, and, if desired, a cationic ink fixing agent and an auxiliary agent on a paper substrate and drying it. be able to.
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. While the surface of the ink receiving layer is in a wet state, the surface may be glossy treated by a casting method in which it is pressed against a mirror drum and dried.

  In the ink jet recording paper of the present invention, the coefficient of static friction between the ink receiving layer surface and the back layer surface (JIS P 8147) is 0.70 to 0.90, and the coefficient of dynamic friction between the ink receiving layer surface and the back layer surface (JIS P 8147). Is preferably 0.60 to 0.85.

  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.

(Comparative 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 150 g / m ² was produced by drying.

[Ink receiving layer liquid A]
Amorphous silica as a pigment (trade name: Fine Seal X-60, secondary particle diameter 6.2 μm, manufactured by Tokuyama Co., Ltd.) 100 parts, silyl-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd.) as an adhesive 20 parts 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 Dispersed in water, an ink receiving layer coating solution A having a concentration of 20% was obtained.

[Preparation of inkjet recording paper]
On the paper substrate A, an ink-receiving layer coating solution A was applied with an air knife coater so that the coating amount was 10 g / m ² and dried to prepare an ink jet recording paper. This ink-receiving layer-coated paper A was sampled by 1 m ² and conditioned for 24 hours in an environment of 23 ° C. and 50% RH (humidity). At this time, the water content of the ink jet recording paper was 7.2%.

Example 1
[Back layer coating liquid A]
100 parts of alumina (trade name: Slip Nine K-33, secondary particle diameter 0.7 μm) as pigment and 30 parts of oxidized starch (Oji Cornstarch, trade name: Ace A) as an adhesive in water To obtain a back surface layer coating solution A having a concentration of 4%.

[Preparation of inkjet recording paper]
In the inkjet recording paper of Comparative Example 1, the back layer coating solution A was applied to the surface on which the ink receiving layer was not applied with a roll coater so that the coating amount was 0.5 g / m ² . It dried and produced the inkjet recording paper. This ink jet recording paper was sampled 1 m ² and conditioned for 24 hours in an environment of 23 ° C. and 50% RH (humidity). The water content of the ink jet recording paper at this time was 7.4%.

(Example 2)
[Back layer coating liquid B]
100 parts of alumina (trade name: Slip Nine K-33, secondary particle diameter 0.7 μm) as pigment and 30 parts of oxidized starch (Oji Cornstarch, trade name: Ace A) as an adhesive in water To obtain a back surface layer coating solution B having a concentration of 1%.

[Preparation of inkjet recording paper]
In the inkjet recording paper of Comparative Example 1, the back layer coating solution B was applied to the surface on which the ink receiving layer was not applied with a roll coater so that the coating amount was 2 g / m ² and dried. Inkjet recording paper was prepared. This ink jet recording paper was sampled 1 m ² and conditioned for 24 hours in an environment of 23 ° C. and 50% RH (humidity). At this time, the moisture content of the ink jet recording paper was 7.3%.

(Example 3)
[Back layer coating liquid C]
100 parts of alumina (trade name: Slip Nine K-33, secondary particle size 0.7 μm) as a pigment and 10 parts of oxidized starch (manufactured by Oji Cornstarch, trade name: Ace A) as an adhesive in water To obtain a back layer coating solution C having a concentration of 4%.

[Preparation of inkjet recording paper]
In the inkjet recording paper of Comparative Example 1, on the surface on which the ink receiving layer was not coated, the back layer coating solution C was applied with a roll coater so that the coating amount was 0.5 g / m ² . It dried and produced the inkjet recording paper. This ink jet recording paper was sampled 1 m ² and conditioned for 24 hours in an environment of 23 ° C. and 50% RH (humidity). At this time, the moisture content of the ink jet recording paper was 7.3%.

Example 4
[Back layer coating liquid D]
100 parts of alumina (manufactured by Yamato Chemical Co., Ltd., trade name: Slip Nine K-33, secondary particle diameter 0.7 μm) as a pigment and 100 parts of oxidized starch (manufactured by Oji Cornstarch Co., Ltd., trade name: Ace A) as an adhesive in water The back layer coating solution D having a concentration of 4% was obtained.

[Preparation of inkjet recording paper]
In the inkjet recording paper of Comparative Example 1, on the surface on which the ink receiving layer was not coated, the back layer coating solution D was applied with a roll coater so that the coating amount was 0.5 g / m ² . It dried and produced the inkjet recording paper. This ink jet recording paper was sampled 1 m ² and conditioned for 24 hours in an environment of 23 ° C. and 50% RH (humidity). The water content of the ink jet recording paper at this time was 7.6%.

(Example 5)
[Back layer coating fluid E]
100 parts of alumina hydrate (trade name: Cataloid AS-3, secondary particle size 0.5 μm) as pigment, 30 parts of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch) as an adhesive Was dispersed in water to obtain a back layer coating solution E having a concentration of 4%.

[Preparation of inkjet recording paper]
In the inkjet recording paper of Comparative Example 1, on the surface on which the ink receiving layer was not coated, the back layer coating liquid E was applied with a roll coater so that the coating amount was 0.5 g / m ² . It dried and produced the inkjet recording paper. This ink jet recording paper was sampled 1 m ² and conditioned for 24 hours in an environment of 23 ° C. and 50% RH (humidity). At this time, the water content of the ink jet recording paper was 7.1%.

(Example 6)
[Back layer coating solution F]
100 parts of alumina (manufactured by Yamato Chemical Co., Ltd., trade name: slip nine K-33, secondary particle diameter 0.7 μm) as a pigment and 30 parts of cationized starch (manufactured by Oji Cornstarch Co., Ltd., trade name: Ace K) as an adhesive Dispersed in water, a back surface layer coating solution F having a concentration of 4% was obtained.

[Preparation of inkjet recording paper]
In the inkjet recording paper of Comparative Example 1, the back layer coating solution F was applied to the surface on which the ink receiving layer was not applied with a roll coater so that the coating amount was 0.5 g / m ² . It dried and produced the inkjet recording paper. This ink jet recording paper was sampled 1 m ² and conditioned for 24 hours in an environment of 23 ° C. and 50% RH (humidity). At this time, the water content of the ink jet recording paper was 7.1%.

(Comparative Example 2)
[Back layer coating solution G]
Disperse 100 parts of alumina (manufactured by Yamato Chemical Co., Ltd., trade name: Slip Nine K-33, secondary particle diameter 0.7 μm) as a pigment and 30 parts of PVA (made by Kuraray Co., Ltd., trade name: PVA117) in water. A back surface coating solution G having a concentration of 4% was obtained.

[Preparation of inkjet recording paper]
In the ink jet recording paper of Comparative Example 1, the back layer coating solution G was applied to the surface on which the ink receiving layer was not applied with a roll coater so that the coating amount was 0.5 g / m ² . It dried and produced the inkjet recording paper. This ink jet recording paper was sampled 1 m ² and conditioned for 24 hours in an environment of 23 ° C. and 50% RH (humidity). At this time, the water content of the ink jet recording paper was 7.2%.

(Comparative Example 3)
[Back layer coating liquid H]
100 parts of amorphous silica (produced by Grace Devison, trade name: Silojet 703A, secondary particle size 0.3 μm) as a pigment, and 30 parts of oxidized starch (produced by Oji Cornstarch, trade name: Ace A) as an adhesive Dispersed in water to obtain a back layer coating solution H having a concentration of 4%.

[Preparation of inkjet recording paper]
In the inkjet recording paper of Comparative Example 1, on the surface on which the ink receiving layer was not applied, the back layer coating solution H was applied with a roll coater so that the coating amount was 0.5 g / m ² . It dried and produced the inkjet recording paper. This ink jet recording paper was sampled 1 m ² and conditioned for 24 hours in an environment of 23 ° C. and 50% RH (humidity). At this time, the water content of the ink jet recording paper was 7.2%.

(Comparative Example 4)
[Back layer coating liquid I]
100 parts of colloidal silica (manufactured by Nissan Chemical Co., Ltd., trade name: Snowtex ST-ZL, primary particle size 0.1 μm) as a pigment, and 30 parts of oxidized starch (produced by Oji Cornstarch Co., Ltd., trade name: Ace A) as water To obtain a back surface layer coating solution I having a concentration of 4%.

[Preparation of inkjet recording paper]
In the inkjet recording paper of Comparative Example 1, on the surface on which the ink receiving layer was not coated, the back layer coating liquid I was applied with a roll coater so that the coating amount was 0.5 g / m ² . It dried and produced the inkjet recording paper. This ink jet recording paper was sampled 1 m ² and conditioned for 24 hours in an environment of 23 ° C. and 50% RH (humidity). The water content of the ink jet recording paper at this time was 7.6%.

(Comparative Example 5)
[Back layer coating liquid J]
100 parts of amorphous silica (trade name: Fine Seal X-60, secondary particle size 6.2 μm) as pigment and 30 parts of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch) as adhesive Was dispersed in water to obtain a back surface layer coating solution J having a concentration of 4%.

[Preparation of inkjet recording paper]
In the inkjet recording paper of Comparative Example 1, on the surface on which the ink receiving layer was not coated, the back layer coating solution J was applied with a roll coater so that the coating amount was 0.5 g / m ² . It dried and produced the inkjet recording paper. This ink jet recording paper was sampled 1 m ² and conditioned for 24 hours in an environment of 23 ° C. and 50% RH (humidity). The water content of the ink jet recording paper at this time was 7.6%.

[Evaluation]
The printer transportability, printer sheet passing accuracy, banding (horizontal stripes of the printing unit), static friction coefficient, dynamic friction coefficient, and environmental curl of the inkjet recording paper obtained in each example and comparative example were evaluated by the following methods.
In the evaluation, printing on the inkjet recording paper is carried out by using a commercially available inkjet printer A (trademark: PIXUS iP3100, manufactured by Canon Inc., paper type: matte photo paper, paper feeding type: cassette [front feeding / front discharging]. ], Print quality: standard).
In addition, assuming that the ink jet recording paper was actually used, 500 recording papers cut to A4 size were stacked and evaluated after humidity adjustment for 24 hours in a 23 ° C. and 50% RH (humidity) environment.

[Printer transportability]
50 sheets of recording paper were set in the printer A and conveyed while printing the nozzle check pattern, and the number of troubles was counted. The same operation was repeated 10 times, and a total of 500 sheets were conveyed per sample.
Printer transportability was evaluated according to the following criteria.
◎: Conveyance failure occurrence rate of less than 1% ○: Conveyance failure occurrence rate of 1% or more and less than 10% △: Conveyance failure occurrence rate of 10% or more and less than 30% ×: Conveyance failure occurrence rate of 30% or more

[Printer feeding accuracy]
In the evaluation of the printer transportability, an ink jet recording paper on which a nozzle check pattern was printed was used, and the printing position deviation was calculated according to the following equation.
Initial printing position: average printing position of the first to tenth sheets from the start of conveyance evaluation The printing position was measured in units of 0.1 mm using a ruler with a magnifying glass.
Final printing position: Average printing position of the 491st to 500th sheets in the conveyance evaluation start. When printing was not performed due to a conveyance failure, the average of the 10 sheets printed most recently was used as the final printing position.
Print position deviation = | Initial print position |-| Final print position |
The printer paper feeding accuracy was evaluated according to the following criteria.
A: Print position deviation is less than 0.5 mm B: Print position deviation is 0.5 mm or more and less than 1.0 mm Δ: Print position deviation is 1.0 mm or more and less than 2.0 mm ×: Print position deviation is 2. 0mm or more

[Banding]
Using printer A, commercially available image processing software was used to adjust the black discharge amount to 30%, and printing was performed on the entire surface of the inkjet recording paper.
Banding was evaluated according to the following criteria:
◎: Almost no horizontal stripes ○: Levels where some horizontal stripes are observed but practically no problem △: Horizontal stripes are conspicuous ×: Horizontal stripes are very conspicuous

[Coefficient of friction]
The static friction coefficient and the dynamic friction coefficient between the ink receiving layer surface and the back surface of the recording paper were measured using the measuring method defined in the horizontal method of JIS P 8147, and the average value of 5 times was shown.

[Environmental curl]
Humidity adjustment for 20 hours at 20 ° C, 20% RH (humidity) and 30 ° C, 80% RH (humidity), A4 size recording paper on a flat desk, 10 sheets each with the ink receiving layer facing upward Thereafter, the height from the horizontal plane at the four corners of the recording paper was averaged and measured. In addition, the curl on the ink receiving layer surface side is defined as + (plus) curl, and the curl on the back surface side is defined as-(minus) curl. The difference between the maximum and minimum curl values in the two environments was calculated as the curl fluctuation range.
Environmental curl was evaluated according to the following criteria.
A: Curl fluctuation width is less than 5 mm B: Curl fluctuation width is 5 mm or more and less than 10 mm Δ: Curl fluctuation width is 10 mm or more and less than 20 mm ×: Curl change width is 20 mm or more

From the results of Table 1 above, examples in which the back layer according to the present invention contains alumina and / or alumina hydrate having an average secondary particle diameter of 1 μm or less as a pigment and starch and / or starch-modified product as an adhesive. Nos. 1 to 6 were found to be ink-jet recording papers that are excellent in curlability and transportability, have high sheet passing accuracy, and can obtain high-definition images that do not cause banding or the like.
On the other hand, it was found that in Comparative Example 1 having no back layer, the environmental curl was very poor, and the transportability and paper passing accuracy were also very poor because the friction coefficient was low.
Comparative Example 2 containing PVA as the adhesive for the back layer was found to have poor paper passing accuracy and banding due to large environmental curl.
Comparative Example 3 containing silica having an average secondary particle diameter of 1 μm or less as a pigment for the back layer has good environmental curl, but has low adhesive strength. Turned out to be.
It was found that Comparative Example 4 containing colloidal silica as a pigment for the back layer was particularly inferior in paper passing accuracy.
Comparative Example 5 containing silica having an average secondary particle diameter of 1 μm or more as a pigment for the back layer was found to have a low friction coefficient and very poor transportability, paper passing accuracy, and banding.

Claims (3)

In an inkjet recording paper in which one or more ink receiving layers containing at least a pigment and an adhesive are provided on one side of a paper base on which pulp is made, an average secondary as a pigment is provided on the other side of the paper base. An ink jet recording paper comprising an alumina having a particle diameter of 1 μm or less and / or an alumina hydrate, and a back layer containing starch and / or starch-modified product as an adhesive. The inkjet recording paper according to claim 1, wherein the ratio of the pigment to the adhesive is 10: 1 to 1: 1 in the back layer. The static friction coefficient (JIS P 8147) between the ink receiving layer surface and the back surface layer surface is 0.70 to 0.90, and the dynamic friction coefficient (JIS P 8147) between the ink receiving layer surface and the back surface layer surface is 0.60 to 0.85. The inkjet recording paper according to claim 1 or 2.