JP2006123316A - Anti-fading agent of image and medium to be recorded by jetting ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anti-fading agent of an image, which gives storage stability over a long period of time of the image, and a medium to be recorded by jetting ink, which reconciles the storage stability over a long period of time of the image and clear image characteristics. <P>SOLUTION: As the anti-fading agent of the image, a phosphate compound represented by either one between general formulae (1) and (2) is used, in general formula (1), R1-R3 are each independently a hydrogen atom, an aliphatic alkyl group, an aromatic alkyl group or a (meth)acryloyloxyalkyl group under the condition that all of R1-R3 are not hydrogen atoms and, in general formula (2), R4-R7 are each independently a hydrogen atom, an aliphatic alkyl group, an aromatic alkyl group or a (meth)acryloyloxyalkyl group under the condition that all of R4-R7 are not hydrogen atoms. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image fading preventing agent for imparting weather resistance to atmospheric gas and indoor / outdoor light used for an ink jet recording medium, and an ink jet recording medium suitable for recording using water-based ink. In particular, the present invention relates to an ink jet recording medium having long-term image storage stability and excellent image characteristics.

  The ink jet recording method is a method for recording images, characters, etc. by causing micro droplets of a recording liquid (recording liquid) such as ink to fly by various operating principles and adhere to a recording medium such as paper. It has features such as high speed, low noise, easy multi-coloring, large flexibility in recording patterns, and no development required. It can be used for printers, copiers, word processors, facsimiles, and plotters. Development to the output section of information equipment such as the above has been further performed and is rapidly spreading. In recent years, high-performance digital cameras, digital videos, scanners, and the like have been provided at low cost, and coupled with the widespread use of personal computers, printers that employ inkjet recording methods for the output of image information obtained from them are extremely suitable. It has come to be used. In such a background, it has been demanded that an image comparable to silver salt photography or plate-making multicolor printing is easily output by an ink jet recording method.

  In order to meet these requirements, improvements have been made to the structure and recording method of the printer itself, such as higher recording speed, higher definition, and full color, and improvements to the structure and characteristics of the recording medium have been actively studied. ing.

  Various types of recording media have been proposed for recording media used in ink jet recording and the like. For recording comparable to silver salt photography, image formation having excellent dye color development, high surface gloss, and high resolution as a recording medium is required. For example, alumina hydrate is used as a constituent material of an ink receiving layer of a recording medium capable of providing an image comparable to a silver salt photograph.

  Furthermore, recently, the storability of recorded images has been required. In order to improve light resistance and gas resistance, a method for improving the storage stability of the recorded image by blending an image fading inhibitor has been proposed.

For example, a recording sheet containing a special cation compound (Patent Document 2) as a method for improving the storage stability of an image to light or gas in the air, and a recording sheet containing a hindered amine compound as a light resistance improver (Patent Document 3) ~ 6) are known. Certainly, the recording medium containing such an image fading inhibitor exhibits a certain effect on gas resistance and light resistance, but in many cases, it is not yet at a satisfactory level for long-term image storage stability.
JP-A-7-232475 Japanese Patent Publication No. 6-30951 Japanese Patent Laid-Open No. 3-13376 Japanese Patent Publication No. 4-34512 JP-A-11-245504 JP 2001-121812 A

  In order to achieve both long-term image preservation and image clarity, it is necessary to solve the following problems.

  Conventionally, as an image fading inhibitor, there are generally hindered amine compounds, hindered phenol compounds, phosphite compounds, thiuram compounds, thioether compounds, thiourea compounds, benzophenone compounds, benzotriazole compounds, etc. Although some weatherability improvement can be achieved by these uses, it has been necessary to use a large amount and a plurality of them in order to improve image storage stability over a longer period. The use of a large amount of an image bleaching agent reduces the transparency of the ink receiving layer, making it difficult to form a clear image, or causing a decrease in ink absorbency in a halftone or secondary color portion. There was a problem such as.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image fading inhibitor that imparts long-term image storability, and an inkjet recording medium that achieves both long-term image storability and clear image characteristics.

  In order to solve the above-mentioned problems, the present inventors have studied, and an inkjet recording medium containing a specific phosphorus compound in the ink-receiving layer does not impair the printability, and the inkjet printed matter loses color tone over a long period of time. Finally, the present invention was completed.

  That is, the present invention is an image fading preventing agent used for an ink jet recording medium, comprising a pentavalent phosphate compound.

  The pentavalent phosphate compound used in the present invention is preferably one represented by the following general formula (1) or general formula (2).

式（１）中、Ｒ１〜Ｒ３はそれぞれ独立に水素原子、脂肪族アルキル基、芳香族アルキル基又は（メタ）アクリロイルオキシアルキル基である。但し、Ｒ１〜Ｒ３が同時にすべて水素原子ではない。

In formula (1), R1 to R3 are each independently a hydrogen atom, an aliphatic alkyl group, an aromatic alkyl group or a (meth) acryloyloxyalkyl group. However, R1 to R3 are not all hydrogen atoms at the same time.

式（２）中、Ｒ４〜Ｒ５はそれぞれ独立に水素原子、脂肪族アルキル基、芳香族アルキル基、又は（メタ）アクリロイルオキシアルキル基である。但し、Ｒ４〜Ｒ７が同時にすべて水素原子ではない。

In formula (2), R4 to R5 are each independently a hydrogen atom, an aliphatic alkyl group, an aromatic alkyl group, or a (meth) acryloyloxyalkyl group. However, R4 to R7 are not all hydrogen atoms at the same time.

  The present invention also provides an ink jet recording medium comprising a substrate, an ink receiving layer containing a pigment and a binder for binding the pigment, wherein the ink receiving layer serves as a pentavalent phosphorus as an image fading preventing agent. An ink jet recording medium comprising an acid ester compound.

  The addition amount of the pentavalent phosphate compound is preferably 0.1 to 10.0% by mass with respect to the total mass of the ink receiving layer.

  Further, the ink receiving layer is a wet solution containing tetraborate, a coating liquid containing alumina hydrate as a pigment, polyvinyl alcohol as a binder, orthoboric acid as a crosslinking agent, and a pentavalent phosphate. It is preferably formed by coating on the surface of a substrate wetted with an agent.

  Moreover, it is preferable that it is the said General formula (1) or General formula (2) as a pentavalent phosphate ester.

  According to the present invention, it is possible to provide an image fading inhibitor that achieves long-term image storage stability, and an inkjet recording medium that achieves both long-term image storage stability and clear image recording characteristics.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

  The present invention relates to an image fading preventing agent that exhibits excellent weather resistance when blended in an ink receiving layer of an ink jet recording medium. The present invention also relates to a base material and an ink formed on the base material. The present invention relates to an ink jet recording medium comprising a pigment for retaining the colorant, a binder for binding the pigment, and an ink receiving layer containing an image fading preventing component of the present invention.

A: Image fading inhibitor As the image fading inhibitor used in the present invention, individual ot selected from pentavalent phosphate compounds having the structure described in the general formula (1) or the general formula (2) is preferable.

式（１）中、Ｒ１〜Ｒ３はそれぞれ独立に水素原子、脂肪族アルキル基、芳香族アルキル基又は（メタ）アクリロイルオキシアルキル基である。但し、Ｒ１〜Ｒ３が同時にすべて水素原子ではない。

In formula (1), R1 to R3 are each independently a hydrogen atom, an aliphatic alkyl group, an aromatic alkyl group or a (meth) acryloyloxyalkyl group. However, R1 to R3 are not all hydrogen atoms at the same time.

式（２）中、Ｒ４〜Ｒ５はそれぞれ独立に水素原子、脂肪族アルキル基、芳香族アルキル基、又は（メタ）アクリロイルオキシアルキル基である。但し、Ｒ４〜Ｒ７が同時にすべて水素原子ではない。

In formula (2), R4 to R5 are each independently a hydrogen atom, an aliphatic alkyl group, an aromatic alkyl group, or a (meth) acryloyloxyalkyl group. However, R4 to R7 are not all hydrogen atoms at the same time.

  In the present invention, the “image fading preventing agent” refers to a dye that protects the dye from factors that cause deterioration of the dye such as gas and light when it is present in the ink receiving layer together with the dye contained in the ink used for image formation. It is a compound that improves the weather resistance of the recording medium and suppresses the yellowing of the recording medium itself over time, the yellowing due to the file when stored in a file for a long time, and the like.

  The image fading inhibitor according to the present invention is characterized by comprising a pentavalent phosphate compound. If this phosphoric ester compound is contained in the ink receiving layer of an ink jet recording medium, the ink jet recording medium is excellent in weather resistance against, for example, a fluorescent lamp or ozone.

  However, the details of the weathering mechanism of the phosphate ester compound according to the present invention are unknown at this stage. Since phosphate esters do not have reducibility, it is likely that factors other than reducibility are effective. As evidence, trivalent phosphite compounds are useful as image fading inhibitors because of their reducibility even with the same phosphorus compounds, but pentavalent phosphate compounds in the present invention are 3 Compared with a monovalent phosphite, it exhibits sufficiently high weather resistance. In addition, known compounds conventionally known as image fading inhibitors, for example, hindered amine compounds, hindered phenol compounds, thiuram compounds, thiourea compounds, benzotriazole UV absorbers, triazine UV absorbers Even if compared with a chemical agent, a benzophenone ultraviolet absorber, a benzoate ultraviolet absorber, etc., the phosphate ester compound of the present invention exhibits sufficiently high weather resistance.

  In the present invention, as long as a pentavalent phosphate ester compound is contained as an image fading preventing agent, a known image fading preventing agent that has been conventionally used may be contained.

  In the present invention, in the phosphate ester compound represented by the general formula (1), at least one of R1 to R3 is an aliphatic alkyl group, an aromatic alkyl group, or a (meth) acryloyloxyalkyl group. In the phosphate ester compound represented by the general formula (2), at least one of R4 to R7 is an aliphatic alkyl group, an aromatic alkyl group, or a (meth) acryloyloxyalkyl group. Examples of the aliphatic alkyl group include alkyl groups having 1 to 18 carbon atoms such as a methyl group, an ethyl group, and a propyl group, and examples of the aromatic alkyl group include a phenyl group, a phenylmethyl group, a toluyl group, and a naphthyl group. And a naphthylmethyl group. The (meth) acryloyloxyalkyl group is an alkyl group having an acryloyloxy group or a methacryloyloxy group.

Specifically, the phosphoric acid ester compound represented by the general formula (1) is as follows, but is not limited thereto.
_{· (C 2 H 5 0)} n P (O) (OH) 3-n n = 1~3
_{· (C 4 H 9 0)} n P (O) (OH) 3-n n = 1~3
_{· (C 4 H 9 OC 2} H 4 0) n P (O) (OH) 3-n n = 1~3
_{· (C 8 H 17 0)} n P (O) (OH) 3-n n = 1~3
_{· (C 12 H 25 0)} n P (O) (OH) 3-n n = 1~3
_{· (C 18 H 37 0)} n P (O) (OH) 3-n n = 1~3
_{· (C 24 H 49 0)} n P (O) (OH) 3-n n = 1~3
_{· (CH 2 = C (CH} 3) COOC 2 H 4 O) n P (O) (OH) 3-n n = 1~3

Specific examples of the phosphoric acid ester compound represented by the general formula (2) are as follows, but are not limited thereto.
・ (C ₄ H ₉ OP (O) (OH)) ₂ O

  Among the above-described phosphoric acid ester compounds that are preferable as an image fading inhibitor, one of R1 to R3 in the general formula (1) is a hydrogen atom, that is, one acidic phosphoric acid ester compound having a free OH. It is. The reason why one of R1 to R3 in the general formula (1) is preferably a hydrogen atom is not clear at this stage.

  The preferable content of the image fading inhibitor comprising a pentavalent phosphate compound in the ink receiving layer is 0.1 to 10.0% by mass with respect to the total solid content of the ink receiving layer. If the amount is less than 0.1% by mass, sufficient weather resistance may not be obtained. If the amount exceeds 10.0% by mass, the ink absorbency is lowered in a halftone, a secondary color portion, and the like. The characteristics may be disturbed. The items considered as the influence on the image recording characteristics by the addition of the image fading inhibitor here are granularity, image density, color vividness, fine line bleeding, and the like. Therefore, the content of the image fading inhibitor that imparts sufficient weather resistance and does not significantly affect the image recording characteristics is preferably 0.1 to 10.0% by mass. A more preferable content of the image fading inhibitor is 2.5 to 6.0% by mass. If the content of the image fading inhibitor in the ion-receiving layer is within this range, the balance between weather resistance and image recording characteristics is better, and the image obtained by adding the image fading inhibitor while providing sufficient weather resistance. Since the recording characteristics are hardly affected, it is very satisfactory.

  In the present invention, as a method for adding the image fading inhibitor to the ink receiving layer, an ink receiving layer is formed in advance using components other than the image fading preventing agent, and then a solution of the image fading preventing agent is added to the ink receiving layer. It is good to apply on the top. The solvent for dissolving the image fading inhibitor may be an organic solvent or water. Further, the concentration is suitably 0.5 to 30% by mass. Alternatively, the image fading preventing agent may be applied to the base material by being included in the raw material coating liquid for the ink receiving layer.

B. Inkjet Recording Medium FIG. 1 shows the layer structure of the inkjet recording medium of the present invention. That is, in the ink jet recording medium of the present invention, the ink receiving layer 1 containing the image fading inhibitor is formed on a base material 2 such as paper.

  The ink receiving layer 1 contains a pigment and a binder in addition to the image fading inhibitor.

  The pigment used here is preferably mainly composed of alumina hydrate in terms of dye fixing properties, transparency, printing density, color developability, and glossiness, but the following pigments may also be used. it can. Examples of inorganic pigments include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, and magnesium hydroxide. Examples of organic pigments include styrene plastic pigments, acrylic plastic pigments, polyethylene particles, microcapsule particles, urea resin particles, and melamine resin particles. One type is selected from these, or two or more types are used in combination as necessary.

As the above-mentioned pigment, it is preferable to use a fine particle pigment having an average particle diameter of 1 μm or less as a main component, and particularly preferable are fine particles such as silica and aluminum oxide. A preferable silica fine particle is a silica fine particle typified by colloidal silica available from the market. Particularly preferable examples of the silica fine particles include those disclosed in Japanese Patent Nos. 2803134 and 2881847. Preferable examples of the aluminum oxide fine particles include alumina hydrate fine particles. In addition, an alumina hydrate is represented by the following general formula (3), for example.
Al ₂ O _3-n (OH) _2n · mH ₂ O (3)
(In the above formula, n represents any of 0, 1, 2, or 3, and m represents a value in the range of 0 to 10, preferably 0 to 5. However, m and n are not 0 at the same time. MH ₂ O often represents a detachable aqueous phase that does not participate in the formation of the crystal lattice, so m can be an integer or non-integer value. M can reach a value of 0 when heated.)

  Alumina hydrate is generally a method of hydrolyzing aluminum alkoxide or sodium aluminate (USP 4,242,271, 4,202,870), an aqueous solution of sodium aluminate containing aluminum sulfate, chloride. It can be produced by a known method such as a method of neutralizing by adding an aqueous solution of aluminum or the like (Japanese Examined Patent Publication No. 57-447605).

  Alumina hydrate suitable in the present invention shows a boehmite structure or an amorphous substance by analysis by X-ray diffraction method, and particularly, JP-A-7-232473, JP-A-8-132731, Alumina hydrates described in, for example, Kaihei 9-66664 and JP-A-9-76628 are preferred.

  In order to impart gloss to the surface of the ink jet recording medium of the present invention by the rewet cast method, the ink-receiving layer formed by drying is re-moistened and the casting process is performed. It is preferable to use a plate-like alumina hydrate having a small tendency and good water absorption. That is, since the plate-like alumina hydrate has good moisture absorption, the re-wetting liquid (moisture) easily penetrates, so that the ink receiving layer 1 is likely to swell and the alumina hydrate particles are easily rearranged. . Therefore, high glossiness can be obtained in the casting process. Moreover, since the rewetting liquid penetrates efficiently, the production efficiency in the casting process is also increased.

  In the present invention, as a binder, cellulose such as polyvinyl alcohol, modified polyvinyl alcohol, starch or modified product thereof, gelatin or modified product thereof, casein or modified product thereof, gum arabic, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, etc. Derivatives, SBR latex, NBR latex, conjugated diene copolymer latex such as methyl methacrylate-butadiene copolymer, functional group modified polymer latex, vinyl copolymer latex such as ethylene-vinyl acetate copolymer, polyvinylpyrrolidone A conventionally known binder such as maleic anhydride or a copolymer thereof, an acrylate ester copolymer or the like can be used. In the present invention, it is preferable to use polyvinyl alcohol as the binder, and it is also preferable to use a conventionally known binder in combination with polyvinyl alcohol. The blending amount of the binder is preferably 5 to 20% by mass with respect to the pigment.

The coating amount of the ink receiving layer 1 is 30 g / m ² or more in terms of dry solid content in order to improve the coating when the image fading inhibitor is included in the ink receiving layer 1 by post-coating. It is preferable that 30 to 60 g / m ² is most preferable.

Including at least one boric acid compound as a crosslinking agent in the raw material for forming the ink receiving layer formed as described above is extremely effective in forming the ink receiving layer 1. As the boric acid compound that can be used in this case, not only orthoboric acid (H ₃ BO ₃ ) but also metaboric acid or hypoboric acid can be used. Specifically, for example, sodium salt of boric acid (Na ₂ B ₄ O ₇ .10H ₂ O, NaBO ₂ .4H ₂ O, etc.), potassium salt (K ₂ B ₄ O ₇₎・ Alkali metal salts such as 5H ₂ O, KBO _2, etc., ammonium salts of boric acid (NH ₄ B ₄ O ₉ .3H ₂ O, NH ₄ BO ₂ etc.), alkalis such as magnesium salts and calcium salts of boric acid There may be mentioned earth metal salts. It is preferable to use orthoboric acid from the viewpoint of the temporal stability of the coating solution and the effect of suppressing the occurrence of cracks. The amount of the boric acid compound used is preferably in the range of 1.0 to 15.0 mass% as orthoboric acid with respect to the binder in the ink receiving layer 1. Even within this range, cracks may occur depending on manufacturing conditions and the like, and selection is required. On the other hand, exceeding the above range is not preferable because the temporal stability of the coating solution is lowered. That is, in the case of production, since the coating liquid is used for a long time, if the content of boric acid is large, the viscosity of the coating liquid increases during that time, and the generation of a gelled product occurs. It is necessary to frequently change the coating liquid and clean the coater head, and the productivity is significantly reduced. Furthermore, when the above range is exceeded, a point-like surface (cast surface) defect is likely to occur in the casting step, and a uniform and good glossy surface may not be obtained.

  The ink receiving layer 1 formed as described above preferably has the pore properties satisfying the following conditions in order to achieve the purpose and effect such as high ink absorbability and high fixability. .

First, the pore volume of the ink receiving layer is preferably in the range of 0.1 to 1.0 cm ³ / g. That is, when the pore volume is less than the above range, sufficient ink absorption performance cannot be obtained, resulting in an ink receiving layer with poor ink absorption, and in some cases, ink overflows and bleeding occurs in the image. There is a fear. On the other hand, when it exceeds the above range, the ink receiving layer 1 tends to be easily cracked or powdered off. The BET specific surface area of the ink receiving layer is preferably ^{20 to} 450 m ² / g. If it is not within the above range, sufficient gloss may not be obtained, and haze increases (because transparency decreases), so the image may appear to be “white haze”. There is. Furthermore, this case is not preferable because there is a possibility that the adsorptivity of the dye in the ink may be lowered. On the other hand, exceeding the above range is not preferable because cracks are likely to occur in the ink receiving layer 1. The values of the pore volume and the BET specific surface area are obtained by a nitrogen adsorption / desorption method.

  In addition to the image fading preventing agent of the present invention, other additives may be added to the ink receiving layer 1 as necessary. Other additives include dispersants, thickeners, pH adjusters, lubricants, fluidity modifiers, surfactants, antifoaming agents, mold release agents, fluorescent whitening agents, UV absorbers, antioxidants, etc. Can be mentioned.

  Further, when forming the ink receiving layer 1, it is preferable to use a substrate whose surface has been wetted with tetraborate in advance because the bond between the substrate and the ink receiving layer becomes strong. The degree of freedom increases.

Considering high ink absorbability, the dry coating amount is preferably 30 g / m ² or more, and the upper limit is more preferably 60 g / m ² . When it is less than 30 g / m ^2, in particular, cyan, magenta, and three color inks of yellow, other black ink, when used in a printer such as a plurality of light ink are added, sufficient ink absorption In other words, ink overflow may occur and bleeding may occur, or ink dye may diffuse to the substrate 2 and print density may decrease. On the other hand, when it exceeds 60 g / m ² , there is a possibility that the generation of cracks cannot be suppressed. Furthermore, if it is 30 g / m ² or more, an ink receiving layer 1 that exhibits sufficient ink absorbency even in a high-temperature and high-humidity environment can be obtained, and if the dry coating amount is 60 g / m ² or less, the ink Coating unevenness of the receiving layer 1 is further less likely to occur, and the ink receiving layer 1 having a stable thickness can be produced.

  As the base material 2 used to form the ink receiving layer 1, chemical pulp such as LBKP and NBKP, mechanical pulp such as GP, PGW, RMP, TMP, CTMP, CMP, and CGP, and waste paper pulp such as DIP Various additives commonly used in papermaking, such as wood pulp and synthetic fiber pulp such as polyethylene fiber, and pigments, sizing agents, fixing agents, yield improvers, paper strength enhancers, etc. Processed by mixing more than seeds, base paper manufactured by various devices such as long paper machine, circular paper machine, twin wire paper machine, etc., and further providing base paper with size press or anchor coat layer with starch, polyvinyl alcohol, etc. Also included are papers and coated papers such as art papers, coated papers and cast coated papers provided with a coating layer thereon. In addition, an ink receiving layer may be provided as it is on such paper, or in order to improve the smoothness of the substrate surface in order to obtain good recording characteristics and glossiness as inkjet recording paper, a machine calendar, A calendar device such as a TG calendar or a soft calendar may be used before the ink receiving layer coating.

  Further, the base material 2 may be one in which a polyolefin resin layer is provided on the above paper, and a synthetic resin such as polyethylene, polypropylene, polyester, nylon, rayon, polyurethane, etc., a film material of a mixture thereof, or the above synthetic resin. Sheets formed by forming into fibers can also be used.

  In the present invention, as a method of adding the image fading inhibitor of the present invention to the ink receiving layer 1, an image fading preventing agent solution in which the image fading inhibiting agent is dissolved in an organic solvent or the like is previously added with components other than the image fading preventing agent. A method of coating on the formed ink receiving layer 1 is simple. By doing so, it is possible to include a large amount of the image retirement preventive agent of the present invention on the surface side of the ink receiving layer 1. It is desirable that the image fading inhibitor concentration in the image fading inhibitor solution used at this time is 0.5 to 30% by mass because coating is easy. Note that the coating method of the image fading inhibitor is preferably a non-contact coating method with respect to the ink receiving layer surface by a die coater, an air knife coater, a spray, etc. from the appearance of the inkjet recording medium after finishing, Contact-type coating methods such as roll coaters, bar coaters, and gravure coaters can also be used.

  The organic solvent that can be used to produce the image fading inhibitor solution in the present invention is not particularly limited, and examples thereof include esters such as ethyl acetate and butyl acetate, ketones such as methyl isobutyl ketone, methyl ethyl ketone, and acetone. And ethers such as diethyl ether and ethyl methyl ether, and alcohols such as isopropanol, methanol and ethanol are preferred. When the image fading inhibitor is water-soluble, water, preferably deionized water, may be used as a solvent.

  Further, an image fading preventing agent may be added to the raw material coating liquid for the ink receiving layer and coated as a coating liquid containing all components.

  After forming the ink receiving layer 1 as described above, a glossy surface can be formed on the surface of the ink receiving layer 1 by a casting method.

  In the casting method, the ink receiving layer 1 in a wet state or a plastic state is pressure-bonded to a heated mirror-like drum (cast drum) surface, dried in the pressure-bonded state, and the mirror surface is removed. This is a method of copying on the surface of the ink receiving layer, and there are three typical methods, ie, a direct method, a rewet method (indirect method), and a coagulation method.

  Any of these casting methods can be used, but in the present invention, it is preferable to use alumina hydrate for the ink receiving layer 1 of the recording medium for ink jet recording. It is more preferable because an inkjet recording medium having a high gloss surface can be obtained.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited to these examples.

The following were used as image fading inhibitors.
・ Image fading inhibitor A: Dibutyl phosphate
(C ₄ H ₉ O) ₂ P (O) OH
-Image fading inhibitor B: bis (2-ethylhexyl) phosphate
{(C ₄ H ₉ ) (C ₂ H ₅ ) CHCH ₂ O} ₂ P (O) OH
-Image fading inhibitor C: Mono n-butyl phosphate
(C ₄ H ₉ O) P (O) (OH) ₂
Hindered amine compound D: tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate (the following formula (4))

Phosphite compound E: Tris (2,4-di-t-butylphenyl) phosphite (the following formula (5))

Comparative Example 1
(Manufacture of base materials)
0.60 parts by mass of cationized starch in a pulp slurry comprising 80 parts by mass of hardwood bleached kraft pulp (LBPK) having a freeness of 450 ml CSF (Canadian Standard Freeness) and 20 parts by mass of softwood bleached kraft pulp (NBPK) having a freeness of 480 ml CSF , 10 parts by weight of heavy calcium carbonate, 15 parts by weight of light calcium carbonate, 0.10 parts by weight of alkyl ketene dimer, 0.03 parts by weight of cationic polyacrylamide and 0.40 parts by weight of sulfuric acid band were added to adjust the stock. After that, the paper was made with a long paper machine, subjected to a three-stage wet press, and dried with a multi-cylinder dryer. Thereafter, a size press apparatus, the aqueous solution of oxidized starch was impregnated so that 1.0 g / m ² in solid content was dried, and then machine calendered, basis weight 155 g / m ^2, a Stockigt sizing degree 100 seconds, A base material having an air permeability of 50 seconds, a Beck smoothness of 30 seconds, and a Gurley stiffness of 11.0 mN was produced.

(Formation of undercoat layer)
As a coating solution used for forming the undercoat layer, 100 parts by mass of a filler consisting of kaolin (trade name: Ultra White 90, manufactured by Engelhard) / zinc oxide / aluminum hydroxide (weight ratio 65/10/25), 7 parts by mass of a commercially available styrene-butadiene latex is added to a slurry having a solid content of 70% by mass consisting of 0.1 parts by mass of a commercially available polyacrylic acid-based dispersant, and then pure water is added to obtain a solids concentration. A composition was prepared by adjusting to 60% by mass. Next, this composition was applied on both sides of the base material prepared above with a blade coater so that the dry coating amount was 15 g / m ² per side and dried. After that, machine calender finishing (linear pressure 150 kgf / cm), basis weight 185 g / m ² , Steecht size degree 300 seconds, air permeability 3,000 seconds, Beck smoothness 200 seconds, Gurley stiffness 11.5 mN undercoat A layered substrate was obtained. The whiteness of the base material with the undercoat layer was measured for each of the five A4 size samples cut and obtained as an average value. As a result, it was L: 95, a ^* : 0, b ^* :-2 (determined as the hue of JIS Z8729).

(Formation of ink receiving layer (containing no image fading inhibitor))
First, an aqueous tetraborate solution (prepared to a solid content concentration of 5.0% by mass by dissolving borax in pure water) on one side of a base material having an undercoat layer on both sides prepared as described above was used. was coated so as to .5g / m ^2, as soon as the coating liquid is impregnated in the undercoating layer, thereon, dry coating amount 35g by a die coater with an ink receiving layer coating solution was prepared in the following The coating was performed at 30 m / min so as to be / m ² . Thereafter, the recording medium 1 on which an ink receiving layer was formed by drying at 170 ° C. was produced.

  After adding sodium aluminate (solid) in a 4% by mass aluminum chloride aqueous solution and adjusting the pH to 4, the temperature was raised to 90 ° C. while stirring as it was, stirring was performed for a while, sodium aluminate was added again, The pH was adjusted to 10, and the aging reaction was carried out for 40 hours while maintaining the temperature. Then, it returned to room temperature and adjusted pH to 7-8. The dispersion was desalted and then acetic acid was added to peptize to obtain a colloidal sol of alumina hydrate. The colloidal sol of alumina hydrate was concentrated to obtain a colloidal solution having a solid content concentration of 17% by mass. This solution and polyvinyl alcohol (trade name: PVA117, manufactured by Kuraray Co., Ltd.) are dissolved in pure water to make a 9% by weight solution. The alumina hydrate solid content and the polyvinyl alcohol solid content are 10: 1 by weight. The ink receiving layer coating solution was obtained by mixing and stirring as described above.

  The recording medium 1 had an average pore radius of 8.5 nm and a pore volume of 0.65 ml / g according to BET measurement.

Example 1
On the ink receiving layer of the recording medium 1 obtained in Comparative Example 1, a 5 mass% MIBK (methyl isobutyl ketone) solution of the image fading inhibitor A is applied with a roll coater, and then the excess is scraped off with a Mayer bar. The coating was performed at 60 m / min so that the coating amount was 0.56 g / m ² as a solid content (that is, 0.1% by mass with respect to the total solid content of the ink receiving layer). And it dried at 110 degreeC within 5 second after coating. Thereafter, a rewet cast coater was used on the surface of the ink receiving layer, and a rewet cast process using hot water was performed to obtain a target inkjet recording medium 2.

Example 2
In Example 1, the surplus in the Mayer bar so that the coating amount of the image fading inhibitor is 5.6 g / m ² as a solid content (that is, 1.0 mass% with respect to the total solid content of the ink receiving layer). An inkjet recording medium 3 was obtained in the same manner as in Example 1 except that the portion was scraped off.

Example 3
In Example 1, the surplus in the Meyer bar so as the coating amount of the image fading preventing agent is 14.0 g / m ² (i.e. 2.5 wt% with respect to the total solid content of the ink receiving layer) as a solid content An inkjet recording medium 4 was obtained in the same manner as in Example 1 except that the portion was scraped off.

Example 4
In Example 1, the excess in the Mayer bar so that the coating amount of the image fading inhibitor is 33.6 g / m ² as a solid content (that is, 6.0 mass% with respect to the total solid content of the ink receiving layer). An inkjet recording medium 5 was obtained in the same manner as in Example 1 except that the portion was scraped off.

Example 5
In Example 1, the excess of the Mayer bar is scraped off so that the coating amount of the image fading inhibitor is 56 g / m ² as a solid content (that is, 10 mass% with respect to the total solid content of the ink receiving layer). Except for the above, an inkjet recording medium 6 was obtained in the same manner as in Example 1.

Example 6
In Example 1, the image fading prevention agent A is the image fading prevention agent B, and the coating amount of the image fading prevention agent is 22.4 g / m ² as a solid content (that is, 4.4 based on the total solid content of the ink receiving layer). An ink jet recording medium 7 was obtained in the same manner as in Example 1 except that the excess of the Mayer bar was scraped off so as to be 0% by mass).

Example 7
In Example 1, the image fading inhibitor A is the image fading inhibitor C, and the coating amount of the image fading inhibitor is 22.4 g / m ² as a solid content (that is, 4.4 based on the total solid content of the ink receiving layer). An ink jet recording medium 8 was obtained in the same manner as in Example 1 except that the excess of the Mayer bar was scraped off so as to be 0% by mass).

Comparative Example 2
In Example 1, the image fading inhibitor A is a hindered amine compound D, and the coating amount of the hindered amine compound is 22.4 g / m ² as a solid content (that is, 4.0% by mass with respect to the total solid content of the ink receiving layer). The ink-jet recording medium 9 was obtained in the same manner as in Example 1 except that the excess of the Mayer bar was scraped off.

Comparative Example 3
In Example 1, the image fading inhibitor A is a phosphite compound E, and the coating amount of the phosphite compound is 22.4 g / m ² as a solid content (that is, based on the total solid content of the ink receiving layer). Inkjet recording medium 10 was obtained in the same manner as in Example 1 except that the excess at the Mayer bar was scraped off to 4.0 mass%.

  Using ink-jet non-recording media 1 to 10 produced in Examples 1 to 7 and Comparative Examples 1 to 3, A) Image storability of recorded matter (light resistance, gas resistance and file yellowing), B) ink Absorbability and C) image characteristics (overall evaluation from sharpness in actual images) were evaluated by the following evaluation methods. The evaluation results obtained are summarized in Table 1.

A) Image storability of recorded matter <Preparation of recorded matter>
Using a photo printer (trade name: PIXUS 950i, ink: BCI-6, manufactured by Canon) using an inkjet method, black is printed on the recording surfaces of the inkjet recording media 1 to 10 created in the above-described Examples and Comparative Examples. , Cyan, magenta, and yellow single color patches were printed so that the print density (OD) was approximately 1.0, thereby producing a recorded matter.

<Light resistance test>
The recorded matter was subjected to a fluorescent light exposure test using a fluorescent light tester (trade name: FT-1, manufactured by Suga Test Instruments Co., Ltd.).
・ Test conditions Fluorescent lamp intensity: 80000 Lux
Test time: 520 hours Temperature and humidity conditions in test tank: 40 ° C, 60% RH
-Light resistance evaluation method;
Measure the image density of the recorded matter before and after the test using a spectrophotometer (trade name: Spectrino, manufactured by Gretag Macbeth Co., Ltd.), obtain the density residual rate from the following formula, and based on the criteria described below. Judged.
Density remaining rate (%) = (image density after test / image density before test) × 100
[Criteria]
◎ Residual rate of magenta concentration is 85% or more.
○ Residual rate of magenta concentration is 80% or more and less than 85%.
△ Magenta concentration remaining rate is 70% or more and less than 80%.
X Magenta concentration remaining rate is less than 70%.

<Gas resistance test>
An ozone exposure test was performed using an ozone test apparatus (trade name: ozone weatherometer, manufactured by Suga Test Instruments Co., Ltd.).
・ Test conditions Exposure gas composition: Ozone 3ppm
Test time: 2 hours Temperature and humidity conditions in test tank: 45 ° C, 55% RH
-Gas resistance evaluation method;
The L value, a ^* value, and b ^* value before and after the test of the above recorded matter were measured using a spectrophotometer (trade name: Spectrino, manufactured by Gretag Macbeth Co., Ltd.), and ΔE was obtained from the following formula. Judgment was made based on the criteria described.
ΔE = {(front L−back L) ² + (front a ^* −back a ^* ) ² + (front b ^{* −back} b ^* ) ² } ^1/2
In this equation, “front L” represents the L value before the test, and “rear L” represents the after the test. The same applies to the a ^* value and the b ^* value.
[Criteria]
○ Among black, cyan, magenta, and yellow single color patches, those having the largest color difference ΔE from the initial image are less than 5.
Δ Among black, cyan, magenta, and yellow single color patches, the one having the largest color difference ΔE from the initial image is 5 or more and 10 or less.
X Among black, cyan, magenta, and yellow single color patches, the one having the largest color difference ΔE from the initial image has a value of 10 or more.

<File yellowing test>
Insert the above recorded material into a file (trade name: NAME CARD HOLDER 60, manufactured by KOKUYO) and store it for 72 hours in an environment of 50 ° C. and dry for 72 hours before and after printing on the recording surface of the recorded material (white character) For the part), the same measurement as in the gas resistance test was performed, ΔE was obtained in the same manner as described above, and the degree of yellowing of the recording surface was determined based on the following criteria.
[Criteria]
A ΔE is less than 1.5 B ΔE is 1.5 or more and less than 3.0 C ΔE is 3.0 or more and less than 4.5 D ΔE is 4.5 or more and less than 6.0 E ΔE is 6.0 or more

B) Ink absorbability On the recording surfaces of the inkjet recording media 1 to 10 created in the above Examples and Comparative Examples, using a photo printer (trade name: PIXUS 950i, ink: BCI-6, manufactured by Canon), A recorded matter was produced by printing 8 gradations of intermediate colors from cyan to magenta in a patch shape. For each patch of the obtained recorded matter, the image quality was comprehensively determined by visual observation according to the following criteria.
[Criteria]
A The uniformity of shading in the patch is particularly excellent.
B There is almost no shading in the patch, and the uniformity is excellent.
C There is a little shading in the patch.
D Level where there is lightness and darkness in the patch, but there is no particular problem in actual use E Level that causes problems in actual use.

C) Image recording characteristics (Comprehensive evaluation based on sharpness in actual images)
Using a photo printer (trade name: PIXUS 950i, ink: BCI-6, manufactured by Canon) on the recording surfaces of the inkjet recording media 1 to 10 prepared in the above Examples and Comparative Examples, portraits (ISO / JIS-SCID N1) Images were printed to produce recorded matter. For the obtained recorded matter, four items of a) granular feeling, b) image density, c) vividness of color, and d) bleeding of fine lines were evaluated. Judged.
[Criteria]
A All the evaluation items are excellent without any problems.
B Although some problems are seen in any of the evaluation items, it is excellent.
C There are some problems in any of the evaluation items, but there is no problem in use.
D Some of the evaluation items have some problems, and there are some problems in use.
E All of the evaluation items have some problems, and there are problems in their use.

  As shown in Table 1, the image fading preventing agent of the present invention can impart long-term image storage stability and clear image recording characteristics to the ink receiving layer of the inkjet recording medium, and this is the image fading. By adding the inhibitor to the ink receiving layer, an ink jet recording medium having both long-term image storability and clear image recording characteristics is provided.

It is a figure which shows the layer structure of the recording medium for inkjet of this invention.

Explanation of symbols

1 Ink receiving layer 2 Base material

Claims (6)

  An image fading inhibitor used for an ink jet recording medium, comprising a pentavalent phosphate compound. The image fading inhibitor according to claim 1, wherein the pentavalent phosphate compound is represented by the following general formula (1) or general formula (2).

In formula (1), R1 to R3 are each independently a hydrogen atom, an aliphatic alkyl group, an aromatic alkyl group, or a (meth) acryloyloxyalkyl group. However, R1 to R3 are not all hydrogen atoms at the same time.

In formula (2), R4 to R7 are each independently a hydrogen atom, an aliphatic alkyl group, an aromatic alkyl group, or a (meth) acryloyloxyalkyl group. However, R4 to R7 are not all hydrogen atoms at the same time.   An inkjet recording medium comprising a base material, an ink receiving layer containing a pigment and a binder for binding the pigment, wherein the ink receiving layer is used as an image fading preventing agent. And a pentavalent phosphate ester compound represented by formula (1).   The inkjet recording medium according to claim 3, wherein the addition amount of the pentavalent phosphate compound is 0.1 to 10.0% by mass with respect to the total mass of the ink receiving layer.   An ink-receiving layer is a coating liquid containing alumina hydrate as a pigment, polyvinyl alcohol as a binder, orthoboric acid as a cross-linking agent, and pentavalent phosphate ester with a wetting agent containing tetraborate. The inkjet recording medium according to claim 3, wherein the inkjet recording medium is formed by coating on a wet substrate surface.   The inkjet recording medium according to claim 3, wherein the pentavalent phosphate compound is represented by the general formula (1) or the general formula (2).

Images