JP2005280307A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium which can obtain excellent ink absorbency by avoiding the strike-through of ink and a waving phenomenon (cockling) occurring on a surface of a printed part by printing. <P>SOLUTION: This inkjet recording medium, wherein an ink absorbing layer and an anchor layer containing a pigment and an adhesive are sequentially provided on base paper, is characterized as follows: pulp and synthetic amorphous silica (A) are included as main components in the base paper; the anchor layer contains latex and synthetic amorphous silica (B) wherein oil absorption based on JIS-K5101 is 220 mL/100 g or more; and the ink absorbing layer contains a polyvinyl alcohol and synthetic amorphous silica (C) with an oil absorption of 240 mL/100 g or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording medium, and more specifically, an ink jet that can prevent a phenomenon of ink cockling and a phenomenon called cockling in which a printing surface generated after ink jet recording undulates, and can provide excellent ink absorbability. The present invention relates to a recording medium.

  The ink jet recording method is a method for recording images, characters, etc. by ejecting micro droplets of ink by various operating principles and attaching them to recording paper such as paper. It has features such as easy recording pattern flexibility, no need for development and fixing, and is rapidly spreading in various applications as a recording apparatus for various figures and color images including Chinese characters. Further, an image formed by the multicolor ink jet method can obtain a recording that is inferior to that of multicolor printing by a plate making method or printing by a color photographic method. In applications where the number of copies to be produced is small, it is being applied widely to the field of full-color image recording because it is less expensive than that using photographic technology.

  In addition, the inkjet recording device can be easily obtained at a personal computer level because of its low price, sharp image and color reproducibility such as sharpness and color, etc. There has been a transition from special recording devices used to general-purpose recording devices. In particular, the recent progress in high-definition ink-jet recording devices and the appearance of ink-jet recording devices with high image quality at low prices The percentage of ownership in Japan has also increased significantly.

  Furthermore, with the diversification of uses, it is increasingly used for large-format posters, POP art, and drafting. In these applications, since the high sharpness of the inkjet is utilized and the color is excellent, a good image can be obtained and the advertising effect is great. Application to these is because it is possible to easily obtain an image excellent in image reproducibility and color reproducibility such as sharpness and color at the personal computer level, and this is also a reason for frequently using inkjet recording media. .

Due to the high performance and diversification of applications of these ink jet recording apparatuses, the characteristics and requirements required for ink jet recording media have become considerably high. In particular, in a recording apparatus with high image definition and a recording apparatus capable of large-format printing, the amount of ink used to form an image is considerably increased compared to the prior art, and an ink receiving layer for absorbing ink Improvement is progressing. However, as will be described later, it is difficult to obtain a satisfactory image quality for a recording apparatus with a large amount of ink only by handling an ink receiving layer, and a base paper that can be a layer that absorbs ink is selected. It is preferable. The fact that the base paper absorbs ink is accompanied by the occurrence of a phenomenon called cockling in which the base paper is stretched and contracted, the recording paper is distorted, and the surface of the printing section is undulated.

  Due to the increase in the amount of ink used for image formation accompanying higher performance of the ink jet recording apparatus, the ink cannot be absorbed by the ink receiving layer alone, but the ink is absorbed by the base paper. As a result, a phenomenon of ink breakthrough occurs. In this phenomenon, the printed ink reaches near the back surface of the recording paper, the printed image is visually recognized from the back surface, and in a severe case, the ink completely falls out to the back surface. This phenomenon is a serious problem because the appearance of the image quality is significantly impaired even when the image quality is high, and there is a demand for improving ink absorption, cockling, and ink back-through. .

  In addition, the cockling mentioned as an object of the present invention is a wave generated on the surface of the printing portion of an ink jet recording medium, and the reflected light is scattered on the glossy recording medium. Compared to this, cockling is conspicuous, and this avoidance is also an important issue. Ink breakthrough is a phenomenon that cannot be seen on printing paper and photographic paper, and is also a problem to be avoided in order to meet the demand for a similar appearance.

  As a means for avoiding these phenomena, a method of making the base paper sufficiently thick or a method of providing a back coat layer on the opposite side of the ink receiving layer through the base paper to suppress ink back-through and base paper expansion / contraction are generally performed. (Unexamined-Japanese-Patent No. 2000-263925, patent document 1). However, although these methods are effective for the back-through of ink, it is difficult to completely avoid cockling for a printing apparatus that has recently increased the amount of ink discharged. Also, in order to increase the thickness of the base paper and cope with the rigidity of the base paper, a considerable thickness is required. As a result, the rigidity of the base paper becomes high, the recording paper lacks flexibility, Inconveniences such as reduced transportability occur.

Furthermore, a recording sheet using silica as a filler for base paper is described in Japanese Patent Application Laid-Open No. 2001-63206 (Patent Document 2). However, cockling and ink see-through are insufficient, and a satisfactory ink jet recording medium has not yet been obtained.
JP 2000-263925 A JP 2001-63206 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording medium capable of avoiding the phenomenon of ink cockle and a phenomenon called cockling in which a printed surface generated after ink jet recording undulates, and obtaining excellent ink absorbability.

  As a result of intensive studies to solve this problem, the present inventors have reached the present invention. That is, the above-described problem of the present invention is that, in an inkjet recording medium in which an anchor layer containing a pigment and an adhesive and an ink receiving layer are sequentially provided on a base paper, pulp and synthetic amorphous silica (A ), The anchor layer contains a synthetic amorphous silica (B) having an oil absorption of 220 ml / 100 g or more represented by JIS-K5101 and latex, and the ink receiving layer has an oil absorption of 240 ml / 100 g or more. It was achieved by an ink jet recording medium characterized by containing synthetic amorphous silica (C) and polyvinyl alcohol.

  The synthetic amorphous silica (A) preferably has an oil absorption of 100 to 200 ml / 100 g.

  In the base paper, the content of the synthetic amorphous silica (A) is preferably 2 to 20% by mass with respect to the pulp.

  The latex is preferably an ethylene-vinyl acetate copolymer or a styrene-butadiene copolymer latex.

  Moreover, it is preferable that the relationship between the oil absorption amounts of the synthetic amorphous silica (B) and (C) is (B) <(C).

  The ink jet recording medium of the present invention has a phenomenon called cockling in which a printing surface generated after ink jet recording is rippled, ink back-through, and excellent ink absorbability.

  The ink jet recording medium of the present invention will be described in detail below. The base paper used in the present invention contains pulp and synthetic amorphous silica (A) as main components. Pulp is not particularly limited, and natural pulp, regenerated pulp, synthetic pulp or the like is used alone or in combination. As the natural pulp, pulp used for papermaking, that is, bleached chemical pulp such as softwood kraft pulp, hardwood kraft pulp, softwood sulfite pulp, hardwood sulfite pulp, etc. can be used. Moreover, mechanical pulp with high whiteness may be sufficient. Further, non-wood pulp made from grass fibers such as straw, esparto, bagasse and kenaf, bast fibers such as hemp, straw, scabbard and scabbard, cotton and the like may be used. Of these, bleached chemical pulp such as softwood kraft pulp, hardwood kraft pulp softwood sulfite pulp, hardwood sulfite pulp and the like, which are most commonly used industrially, is preferable.

  The pulp is preferably beaten by a beating machine such as a double disc refiner in order to improve paper characteristics, such as paper properties, such as strength, smoothness, and uniformity of formation. The degree of beating can be selected according to the purpose in the range of about 250 ml to 550 ml in Canadian Standard Freeness.

  The filler used for the base paper of the present invention mainly contains synthetic amorphous silica (A). Although other fillers can be used in combination, it is preferable to use synthetic amorphous silica alone in the present invention. When other fillers are used in combination, the content of the other fillers is preferably 10% by mass or less with respect to the synthetic amorphous silica. Other fillers include, for example, inorganic pigments such as talc, clay, kaolin, calcined kaolin, heavy calcium carbonate, light calcium carbonate, white carbon, diatomaceous earth, titanium oxide, zinc oxide, barium sulfate, styrene plastic pigments, polyethylene And organic pigments such as microcapsules, urea resins, and melamine resins.

  When the synthetic amorphous silica (A) contained in the base paper has an oil absorption expressed by JIS-K5101 of 100 to 200 ml / 100 g, good ink absorption and cockling can be obtained. More preferably, it is 120-200 ml / 100g.

  The blending amount of the synthetic amorphous silica (A) in the base paper is preferably 2 to 20% by mass with respect to the pulp, so that a good printing density can be obtained. More preferably, it is 3 to 15% by mass.

  The beaten pulp is made by a paper machine such as a long net paper machine, a twin wire paper machine, or a round net paper machine.In this case, in the present invention, a pulp dispersion aid usually used for paper making, Various additives such as a dry paper strength enhancer, a wet paper strength enhancer, a filler, a sizing agent, and a fixing agent can be added as necessary. Furthermore, if necessary, pH adjusting agents, dyes, colored pigments, fluorescent brighteners, and the like can be added.

  Further, the base paper preferably used in the present invention is a liquid containing various additives such as a water-soluble polymer additive, which is applied with a tab size, a size press, a gate roll coater, a film transfer coater or the like. Is also possible.

  Examples of the water-soluble polymer additive include starch derivatives such as starch, cationized starch, oxidized starch, etherified starch and phosphate esterified starch, polyvinyl alcohol and polyvinyl alcohol derivatives such as carboxy-modified polyvinyl alcohol, and carboxymethylcellulose. , Cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, cellulose sulfate, water-soluble natural polymers such as gelatin, casein, soybean protein, sodium polyacrylate, sodium styrene-maleic anhydride copolymer, sodium polystyrene sulfonate Water-soluble polymers such as maleic anhydride resins, water-based polymer adhesives such as thermosetting synthetic resins such as melamine resins and urea resins, and the like. - ammonium salt of maleic anhydride copolymer alkyl ester, an alkyl ketene dimer emulsion, styrene - butadiene copolymer, ethylene - vinyl acetate copolymer, polyethylene, dispersion of polyvinylidene chloride. Other additives include antistatic agents such as sodium chloride, calcium chloride and bow glass as inorganic electrolytes, glycerin and polyethylene glycol as hygroscopic substances, hydrochloric acid, caustic soda and sodium carbonate as pH regulators. It is also possible to use other additives such as dyes, fluorescent brighteners, antioxidants and ultraviolet absorbers in combination.

The base paper preferably used in the present invention may use a calendar device such as a machine calendar, a TG calendar, or a soft calendar for the purpose of controlling flattening during or after papermaking. Further, a base paper made of multi-layered paper such as paper making may be used. The basis weight of the base paper is ^{40g / m 2 ~150g / m 2} .

  The anchor layer in the present invention contains at least a synthetic amorphous silica (B) having an oil absorption of 220 ml / 100 g or more represented by JIS-K5101 and latex.

  The anchor layer and the ink receiving layer contain synthetic amorphous silica as a pigment. Other pigments can be used in combination, but preferably, synthetic amorphous silica is used alone. When other pigments are used in combination, the content is preferably 10% by mass or less with respect to the synthetic amorphous silica. Other pigments include, for example, light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, Magnesium silicate, colloidal silica, colloidal alumina, pseudoboehmite, aluminum hydroxide, alumina, lithopone, zeolite, hydrous halloysite, magnesium carbonate, magnesium hydroxide, white inorganic pigments, styrene plastic pigment, acrylic plastic pigment, polyethylene, micro Examples thereof include organic pigments such as capsules, urea resins, and melamine resins.

  The synthetic amorphous silica (B) used for the anchor layer has high ink absorbability when the oil absorption is 220 ml / 100 g or more. Preferably, it is 220-320 ml / 100g.

  The anchor layer contains latex as a binder. In addition to the latex, it is preferable to use a water-soluble resin in combination. When the latex and the water-soluble resin have a mass ratio of 2:98 to 60:40, high ink absorbability can be obtained. More preferably, it is 5: 95-50: 50. Examples of the latex include conjugated diene copolymer latexes such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer, and acrylic polymers such as acrylic acid ester and methacrylic acid ester polymers or copolymers. Latex, vinyl polymer latex such as ethylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, etc., or functional group-modified polymer latex with functional group-containing monomers such as carboxy groups of these various polymers And polyurethane resin latex. Among these, an ethylene-vinyl acetate copolymer or a styrene-butadiene copolymer latex is preferable, and a styrene-butadiene copolymer latex that can provide high coating layer strength is more preferable. Examples of the water-soluble resin include cellulose binders such as methyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, and hydroxyethyl cellulose, starch and modified products thereof, gelatin and modified products thereof, casein, pullulan, gum arabic, and Examples include natural polymer resins such as albumin or derivatives thereof, and various derivatives such as polyvinyl alcohol or silanol-modified products thereof, carboxylated products, and cationized products.

  The latex content in the anchor layer is preferably from 2 to 70% by mass with respect to the pigment because good coating layer strength and ink absorbability can be obtained. More preferably, it is 5-60 mass%.

  The ink receiving layer in the invention contains at least synthetic amorphous silica (C) having an oil absorption of 240 ml / 100 g or more and polyvinyl alcohol.

  Further, when the synthetic amorphous silica (C) used in the ink receiving layer has an oil absorption of 240 ml / 100 g or more, high ink absorbability can be obtained. Preferably, it is 240-360 ml / 100g.

  Furthermore, in the synthetic amorphous silicas (B) and (C), when the relationship between the oil absorption amounts is (B) <(C), the ink absorbability is fast and more ink can be contained in the ink receiving layer. This is preferable because it can be fastened.

  The ink receiving layer contains polyvinyl alcohol as a binder. In addition to the polyvinyl alcohol, cellulose binders such as methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose, and hydroxyethylcellulose, starch and modified products thereof, gelatin and modified products thereof, and casein are used to the extent that the effects of the present invention are not impaired. , Pullulan, gum arabic, and natural polymer resins such as albumin or derivatives thereof, conjugated diene copolymer latex such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, acrylic acid ester and methacrylic acid ester Acrylic polymer latex such as a polymer or copolymer of the above, a vinyl polymer latex such as ethylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, or a carbopolymer of these various polymers. Functional group-modified polymer latex according to the functional group-containing monomers such as shea groups include polyurethane-based latex, it may be used to select at least one of these more.

  The polyvinyl alcohol content in the ink receiving layer is preferably from 5 to 70% by mass with respect to the pigment, since good coating layer strength and ink absorbability can be obtained. More preferably, it is 10-60 mass%.

  Further, in the anchor layer and the ink receiving layer, as additives, dye fixing agents (various cationic resins), pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, release agents Sizing agent, penetrating agent, coloring dye, coloring pigment, fluorescent brightening agent, ultraviolet absorber, antioxidant, preservative, antibacterial agent, wet strength enhancer, dry strength enhancer, etc. .

  In particular, from secondary amines, tertiary amines, and quaternary ammonium salts that form insoluble salts with sulfonic acid groups, carboxyl groups, amino groups, etc. in water-soluble direct dyes and water-soluble acid dyes, which are the dye components of water-based inks. When the cationic dye fixing agent is blended, since the dye is captured in the anchor layer and the ink receiving layer, the color property is improved. In addition, formation of an insoluble salt is preferable because destruction of a recorded image due to the dye or pigment in the ink flowing out from the anchor layer and the ink receiving layer due to dripping or moisture absorption is suppressed.

The coating amount of the anchor layer and the ink receiving ^{layer, 3g / m 2 ~20g / m} 2 is good ink absorption properties and print density can be obtained, preferably. More preferably ^{5g / m 2 ~15g / m 2} .

  Various methods such as various blade coaters, roll coaters, air knife coaters, comma coaters, bar coaters, rod blade coaters, curtain coaters, short dwell coaters, size presses, etc. Can be used off-machine. Coating by a curtain coater is particularly preferred because a coating layer having a uniform thickness with no coating unevenness can be obtained.

  After application of the ink receiving layer, the back surface may be sprayed with humidified air or humidified steam to correct the curl, and further, a calendar process using a machine calendar, a TG calendar, a super calendar, a soft calendar, or the like may be performed. .

  Examples of the present invention will be described below, but the present invention is not limited to these examples. In the examples and comparative examples, “parts” and “%” indicate parts by mass and mass% unless otherwise specified. In addition, the number of parts shown in the blend is the number of substantial components.

A mixture of 50 parts of hardwood bleached kraft pulp (LBKP, whiteness 90%) and 50 parts of softwood bleached sulfite pulp (NBSP, whiteness 90%) was beaten to 350 ml with Canadian Standard Freeness to prepare pulp. As a synthetic amorphous silica (A) as a filler, 8 parts of a synthetic amorphous silica (thyloid 74X6500: oil absorption 200 ml / 100 g, manufactured by Grace), 0.5 part of an alkyl ketene dimer as a sizing agent, dry paper strength As an enhancer, 1.0 part of polyacrylamide and 2.0 parts of cationized starch were added and diluted with water to give a 1% slurry. This slurry was made with a long paper machine to a basis weight of 100 g / m ² to prepare a base paper. On one side of this base paper, coating liquid a as an anchor layer was applied and dried by a curtain coater so that the coating amount after drying was 8 g / m ^{2. On} the anchor layer thus obtained, ink was applied. The receiving layer coating solution b is coated using a curtain coater so that the coating amount after drying is 7 g / m ² , dried, and subjected to supercalendering, and the inkjet recording of the present invention. A medium was obtained.

<Anchor layer coating solution a>
As synthetic amorphous silica (B), 100 parts of synthetic amorphous silica (Mizukasil P78D; oil absorption 240 ml / 100 g, manufactured by Mizusawa Chemical Co., Ltd.), 20 parts of silanol-modified polyvinyl alcohol (R-1130, manufactured by Kuraray Co., Ltd.), 10 parts of styrene-butadiene copolymer latex (Luckster DS226, manufactured by Dainippon Ink & Chemicals, Inc.) and 10 parts of cationic dye fixing agent (Smiles Resin 1001, manufactured by Sumitomo Chemical Co., Ltd.) are blended in water. An anchor layer coating solution a having a solid content concentration of 18% was prepared by uniformly dispersing.

<Ink-receiving layer coating solution b>
As synthetic amorphous silica (C), 100 parts of synthetic amorphous silica (thyroid ED5; oil absorption 300 ml / 100 g, manufactured by Grace), 20 parts of polyvinyl alcohol (PVA117, manufactured by Kuraray), cationic dye fixing agent ( 20 parts of Sumire's Resin 1001 (manufactured by Sumitomo Chemical Co., Ltd.) were blended in water and uniformly dispersed to prepare an ink receiving layer coating solution b having a solid content concentration of 19%.

  In the anchor layer coating solution a, the synthetic amorphous silica (B) is changed to synthetic amorphous silica (thyroid ED5; oil absorption 300 ml / 100 g, manufactured by Grace), and the ink receiving layer coating solution b In the above, the anchor layer coating liquid and the ink receiving layer were similarly changed except that the synthetic amorphous silica (C) was changed to synthetic amorphous silica (Silojet P407; oil absorption 320 ml / 100 g, manufactured by Grace). A coating liquid was prepared, and the ink jet recording medium of the present invention was obtained in the same manner as in Example 1 except that.

  Ink-receptive printing was similarly performed except that the synthetic amorphous silica (C) was changed to synthetic amorphous silica (Silojet P407; oil absorption 320 ml / 100 g, manufactured by Grace) in the ink-receiving layer coating liquid b. A layer coating solution was prepared, and the ink jet recording medium of the present invention was obtained in the same manner as in Example 1 except that.

  In the ink receiving layer coating liquid b, the anchor layer coating was similarly performed except that the synthetic amorphous silica (B) was replaced with synthetic amorphous silica (Fine Seal X37B; oil absorption 270 ml / 100 g, manufactured by Tokuyama Corporation). A working fluid was prepared, and the ink jet recording medium of the present invention was obtained in the same manner as in Example 1 except for that.

  In anchor layer coating solution a, styrene-butadiene copolymer latex (Rackstar DS226, manufactured by Dainippon Ink & Chemicals, Inc.) is changed to ethylene-vinyl acetate copolymer latex (Panflex OM-5500, manufactured by Kuraray Co., Ltd.). An anchor layer coating solution was prepared in the same manner except that the change was made, and the ink jet recording medium of the present invention was obtained in the same manner as in Example 1 except that.

  A base paper was prepared in the same manner except that the synthetic amorphous silica (A) was changed to synthetic amorphous silica (Mizukasil P554A; oil absorption 100 ml / 100 g, manufactured by Mizusawa Chemical Co., Ltd.) Other than that was carried out similarly to Example 1, and obtained the inkjet recording medium of this invention.

  A base paper was prepared in the same manner as in the base paper, except that the blending amount of the synthetic amorphous silica (A) was 15 parts. Otherwise, the ink jet recording medium of the present invention was prepared in the same manner as in Example 1. Obtained.

  A base paper was prepared in the same manner as in the base paper, except that the amount of the synthetic amorphous silica (A) was 25 parts. Otherwise, the ink jet recording medium of the present invention was prepared in the same manner as in Example 1. Obtained.

  A base paper was prepared in the same manner except that the synthetic amorphous silica (A) was changed to a synthetic amorphous silica (Siloid ED5; oil absorption 300 ml / 100 g, manufactured by Grace) in the base paper filler. Obtained an inkjet recording medium of the present invention in the same manner as in Example 1.

(Comparative Example 1)
A base paper was prepared in the same manner except that the synthetic amorphous silica (A) was changed to calcium carbonate (Tama Pearl 222H; oil absorption 47 ml / 100 g, manufactured by Okutama Kogyo Co., Ltd.) in the base paper filler. In the same manner as in Example 1, a comparative inkjet recording medium was obtained.

(Comparative Example 2)
In the anchor layer coating solution a, the anchor layer was similarly changed except that the synthetic amorphous silica (B) was changed to synthetic amorphous silica (Mizukasil P603: oil absorption 110 ml / 100 g, manufactured by Mizusawa Chemical Co., Ltd.). A coating liquid was prepared, and otherwise, an ink jet recording medium of a comparative example was obtained in the same manner as in Example 1.

(Comparative Example 3)
Ink was similarly used except that the synthetic amorphous silica (C) was changed to synthetic amorphous silica (Mizukasil P603: oil absorption 110 ml / 100 g, manufactured by Mizusawa Chemical Co., Ltd.) in the ink receiving layer coating liquid b. A receiving layer coating solution was prepared, and other than that was obtained in the same manner as in Example 1 to obtain a comparative ink jet recording medium.

(Comparative Example 4)
An ink jet recording medium of a comparative example was obtained in the same manner as in Example 1 except that the anchor layer coating solution a was not provided and the coating amount of the ink receiving layer coating solution b was changed to 15 g / m ² .

(Comparative Example 5)
An ink jet recording medium of a comparative example was obtained in the same manner as in Example 1 except that the coating amount of the anchor layer coating solution a was changed to 15 g / m ² without providing the ink receiving layer coating solution b.

(Comparative Example 6)
In the anchor layer coating solution a, styrene-butadiene copolymer latex (Rackstar DS226, manufactured by Dainippon Ink & Chemicals, Inc.) is not blended, and silanol-modified polyvinyl alcohol (R-1130, manufactured by Kuraray Co., Ltd.) is added to 30 parts. An anchor layer coating solution was prepared in the same manner except that the change was made, and an ink jet recording medium of a comparative example was obtained in the same manner as in Example 1 except that.

  As described above, the inkjet recording media prepared in Examples and Comparative Examples were evaluated by the following evaluation methods, and the results are shown in Table 1.

<Cock ring>
Using a commercially available ink jet recording apparatus (MJ830C: manufactured by Epson Corporation), solid printing was performed with black ink at a size of 15 cm square on the center of the sample cut to A4 size, and then the degree of undulation on the printed surface and the back surface was measured. Visual evaluation was made, and the following criteria were used. Below Δ, the occurrence of cockling causes visual degradation of image quality, which causes a problem.
A: There is no cockling.
◯: Slightly cockling is visually recognized at the boundary between the solid print portion and the non-print portion.
(Triangle | delta): Cock ring is visually recognized by the whole printing part.
X: Visible in a state where the cock ring is greatly swollen over the entire printing portion.

<Ink breakthrough>
Using a commercially available photo inkjet recording apparatus (BJC-420J: manufactured by Canon Inc.), after performing blue (cyan + magenta) heavy-color printing in a size of 10 cm square on the center of the sample cut into A4 size, A commercially available reflection densitometer (Macbeth RD918 type: manufactured by Macbeth) measures the image density of the back side of the printed part and the back side of the non-printed part, calculates the non-printed part / printed part density ratio, Judged by the criteria of. Below are the levels that are problematic in practice.
A: Non-printed area / printed area density ratio of 1 to 0.9
◯: Non-printed area / printed area density ratio of 0.89 to 0.75
Δ: Non-printed portion / printed portion density ratio of 0.74 to 0.5
X: Non-printing part / printing part density ratio is less than 0.5

<Ink absorbability>
Using a commercially available photo ink jet recording apparatus (BJC-420J: manufactured by Canon Inc.), a white line (non-printing portion) lattice pattern is created in a mixed color solid pattern composed of cyan ink and magenta ink, and ink bleeds into the lattice. About taking out, it evaluated visually according to the following reference | standard.
A: The lattice is completely clear.
○: Ink oozing is observed on only a part of the lattice.
(Triangle | delta): A grating | lattice becomes narrow and the bleeding of an ink is seen generally.
X: Lattice is absent due to ink bleeding.

<Print density>
A solid pattern was printed with a commercially available photo ink jet recording apparatus (BJC-420J: manufactured by Canon Inc.) and black ink, and the optical reflection density was measured with a Macbeth RD-918 model.

<Coating layer strength>
The writing property when writing characters with a ballpoint pen on the recording layer was visually evaluated.
A: The recording layer is never scraped off with a ballpoint pen, and the writing property is very good.
○: The recording layer is hardly scraped off with a ballpoint pen, and the writing property is good.
(Triangle | delta): A recording layer may be scraped off with a ball-point pen for a while, and it becomes a little problem in the interpretation of a character.
X: The recording layer is scraped off with a ballpoint pen, and the character cannot be read.

  From Table 1, in an inkjet recording medium in which an anchor layer containing a pigment and an adhesive and an ink receiving layer were sequentially provided on the base papers of Examples 1 to 9, pulp and synthetic amorphous silica ( A), the anchor layer contains a synthetic amorphous silica (B) having an oil absorption of 220 ml / 100 g or more represented by JIS-K5101 and latex, and the ink receiving layer has an oil absorption of 240 ml / 100 g or more. An ink jet recording medium characterized by containing synthetic amorphous silica (C) and polyvinyl alcohol is an excellent ink that avoids undulation phenomenon (cockling) that occurs on the surface of the printing portion due to printing and ink back-through. Absorbability is obtained and good.

  On the other hand, when the synthetic amorphous silica (A) is changed to calcium carbonate as the filler in the base paper as in Comparative Example 1, it is difficult to avoid cockling and ink penetration, and the print density also decreases. As in Comparative Examples 2 and 3, when the oil absorption amount of the synthetic amorphous silica (B) in the anchor layer or the synthetic amorphous silica (C) in the ink receiving layer is reduced, the ink absorbability decreases, Furthermore, it is impossible to avoid cockling and ink breakthrough. Further, as in Comparative Examples 4 and 5, when the anchor layer or the ink receiving layer is not provided, the print density and the ink absorbability are greatly reduced, and it is difficult to avoid cockling and ink back-through. Further, as in Comparative Example 6, when latex is not blended in the anchor layer, the print density is lowered, and it is impossible to avoid cockling and ink breakthrough. In either case, satisfactory quality could not be obtained.

Claims (5)

  In an inkjet recording medium in which an anchor layer containing a pigment and an adhesive and an ink receiving layer are sequentially provided on a base paper, the base paper contains pulp and synthetic amorphous silica (A) as main components, and the anchor layer is JIS A synthetic amorphous silica (B) having an oil absorption of 220 ml / 100 g or more represented by -K5101 and latex, and a synthetic amorphous silica (C) having an oil absorption of 240 ml / 100 g or more of the ink receiving layer; An inkjet recording medium comprising polyvinyl alcohol.   The inkjet recording medium according to claim 1, wherein the synthetic amorphous silica (A) has an oil absorption of 100 to 200 ml / 100 g.   The inkjet recording medium according to claim 1 or 2, wherein the content of the synthetic amorphous silica (A) in the base paper is 2 to 20% by mass with respect to the pulp.   The inkjet recording medium according to claim 1, wherein the latex is an ethylene-vinyl acetate copolymer or a styrene-butadiene copolymer latex.   2. The ink jet recording medium according to claim 1, wherein a relationship between oil absorption amounts of the synthetic amorphous silica (B) and (C) is (B) <(C).