JP2005280308A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium which has image clarity comparable to that of photographic paper for silver halide photography, and which can obtain not only high opacity and ink absorbency but also excellent coating layer strength. <P>SOLUTION: This inkjet recording medium, wherein at least an ink absorbing layer and a gloss development layer provided by a cast method are sequentially provided on an air-permeable substrate, is characterized in that at least synthetic amorphous silica (A) and a urea-formaldehyde resin (B) are contained as pigments in the ink absorbing layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inkjet recording medium having image clarity comparable to silver salt photographic printing paper, high opacity and ink absorbency, and excellent coating layer strength.

  The ink jet recording method records images, characters, and the like by causing ink droplets to fly by various operating principles and adhere to a recording medium such as paper. The recording system has features such as high speed, low noise, easy multi-coloring, large flexibility in recording patterns, no need for development and fixing, and various recording devices such as various figures and color images including kanji. It is rapidly spreading in applications. Furthermore, the image formed by the multicolor ink jet method can obtain a recording that is inferior to the printing by the multicolor printing by the plate making method or the printing by the color photographic method by expanding the resolution and the color reproduction range. Applications that require a small number of copies are being used more widely in the field of full-color image recording because they are less expensive than with photographic technology.

  In addition, printers and plotters that use the inkjet method are designed to increase resolution and expand the color reproduction range in order to further improve image quality from the market. We are dealing with it. Therefore, an increase in ink receiving capacity commensurate with the discharge amount is an important technical issue for the recording medium, and it is indispensable to secure a high ink receiving capacity and to apply a coating layer with good color development. . In addition, the appearance of gloss, rigidity, hue, and the like is required to be similar to silver halide photographs and printing paper, and conventional high-quality paper and coated paper inkjet recording media cannot meet these demands. .

  In particular, when gloss is imparted in the prior art, there is an accompanying problem that ink absorbability, which is an important characteristic required for an ink jet recording medium, is lacking. In order to ensure the absorption, it is necessary to provide a coating layer with a large void amount, and the coating composition of the coating layer has a porous particle having a large particle diameter present as secondary particles or tertiary particles as a pigment. However, since the surface of the coating layer was rough due to the influence of the particles, only a so-called matte tone having a low gloss was obtained.

  In general, the gloss treatment is performed by using a calendar device such as a super calendar or a gloss calendar, and smoothing the surface of the coating layer by passing paper between rolls to which pressure or temperature is applied. However, when the calendar treatment is performed under high linear pressure for the purpose of imparting gloss to the ink jet recording sheet, the gloss is improved, but the voids in the coating layer are reduced, the ink absorption is slow, and the absorption capacity is reduced. There is a problem that the ink overflows due to the shortage. For this reason, in the calendar process, conditions must be selected within the range of the allowable ink absorption capacity, and in order to obtain ink absorption and gloss, it is difficult to cope with the current technology. .

  As an attempt to impart gloss to such a current situation, there is a method of providing a coating layer having extremely small voids such as CMC or gelatin on a substrate laminated with a film or resin, and a small amount of ink is flying. Although effective for a recording apparatus, it is difficult to ensure sufficient ink absorption due to ink bleeding or overflow in a recording apparatus with a large amount of ink or in a mixed color portion where each ink is mixed and the amount of ink increases. .

  For this reason, in order to achieve both ink absorbability and gloss, which are contradictory properties, a cast processing method capable of imparting strong gloss to the coating layer is known. There are the following three methods. That is, a direct method in which the coating liquid applied to the base material is not dried at all and pressed against a heated cast drum, or after the coating liquid applied to the base material is once dried or semi-dried , Rewetting method in which the wetted liquid is returned to a plastic state again and then pressed against the heated cast drum, and the coating liquid applied to the substrate is treated with the coagulating liquid, and the gel has no fluidity. In this state, it is a solidification method in which it is pressed against a heated cast drum. These casting methods are common in that a high gloss coating layer surface is obtained by copying a mirror-like drum surface. Examples of the ink jet recording medium using the above-described casting method include, for example, JP-A-7-117335, JP-A-8-118790 (Patent Document 1), JP-A-8-132730, and JP-A-8-300804. No. 1, JP-A-10-287038, and the like.

  Even with these methods, it is difficult for ink jet printers and plotters with a large amount of ink discharge in recent years to achieve both ink absorbency and gloss, which are contradictory properties, and strong gloss can be obtained when designing with emphasis on ink absorbency. If emphasis is placed on gloss, it is difficult to ensure ink absorbability, and it is necessary to accept a decrease in one of the characteristics. In other words, with the conventional technology, it is difficult to achieve both ink absorbency and gloss, which are contradictory properties.

  In addition, since a high-quality inkjet recording apparatus called a photo type uses light color ink in addition to the four colors CMYK, a large amount of ink is ejected. For this reason, the ink cannot be completely absorbed by the coating layer alone, but the ink is absorbed by the base paper. As a result, the phenomenon of ink breakthrough occurs. In this phenomenon, the printed ink reaches near the back side of the recording paper, the printed image is visually recognized from the back side, and in a severe case, the ink completely escapes to the back side. This phenomenon is a big problem because the visual quality is remarkably impaired even when the image quality is high quality, and this is a big problem. Ink jet recording media are not good for improving the ink absorption of the ink receiving layer and preventing the ink from coming off. There is a demand for improved transparency.

  As a method for solving these problems, for example, Japanese Patent Application Laid-Open No. 2003-285543 (Patent Document 2) discloses a synthetic amorphous silica having an oil absorption amount of 200 ml / 100 g or more as a pigment of an ink receiving layer and a particle diameter of 2 μm or less. An ink jet recording medium has been proposed in which opacity is improved by containing heavy calcium carbonate containing 95% by weight or more of these particles. However, although a certain degree of opacity can be obtained, it is insufficient to prevent the ink from passing through, and has not reached a satisfactory level in ink absorptivity.

  Japanese Patent Application Laid-Open No. 7-149038 (Patent Document 3) proposes the use of a urea resin-based plastic pigment as a pigment for the ink receiving layer. Inkjet recording with high opacity and improved ink see-through, but insufficient ink absorption, yet excellent mapping, print quality, and high opacity that can prevent ink see-through No media has been obtained.

Although the surface gloss can be obtained as it is by the casting method, it is an index called image clarity as well as the surface gloss that determines the aesthetic element of the gloss. The image clarity is an index of how clear and undistorted the image is when an object is reflected on a glossy surface. Even with the same surface gloss, it can be said that a higher gloss level is perceived as there is no distortion, and the aesthetic element is higher. However, an evaluation that correlates with visual sensation cannot be made only by measuring the surface gloss level.
JP-A-8-118790 JP 2003-285543 A JP-A-7-149038

  An object of the present invention is to provide an ink jet recording medium having image clarity comparable to silver salt photographic printing paper, high opacity and ink absorbency, and excellent coating layer strength.

  As a result of intensive studies to solve this problem, the present inventors have reached the present invention. That is, the object of the present invention is to provide an ink jet recording medium having at least an ink receiving layer and a glossy layer sequentially provided by a casting method on a gas-permeable support, and the ink receiving layer is at least a synthetic amorphous material as a pigment. It has been achieved by an ink jet recording medium characterized by containing porous silica (A) and urea-formaldehyde resin (B).

  The oil absorption amount of the synthetic amorphous silica (A) is preferably 200 ml / 100 g or more.

  Further, the urea / formaldehyde resin (B) preferably has an average particle size of 1 to 10 μm.

  The mass ratio (A: B) of the synthetic amorphous silica (A) and the urea / formaldehyde resin (B) is preferably 30:70 to 80:20.

  Moreover, it is preferable that the said gloss expression layer is provided by the coagulation method.

  The glossy layer preferably contains pseudoboehmite alumina hydrate and cationized colloidal silica in a mass ratio of 95: 5 to 50:50.

  The ink jet recording medium of the present invention has high opacity and ink absorbability, and also has excellent coating layer strength, and has image clarity comparable to silver salt photographic printing paper.

The ink jet recording medium of the present invention will be described in detail below. The support used in the present invention is a gas-permeable support, and a known paper support can be appropriately selected and used. For example, wood pulp such as chemical pulp such as LBKP and NBKP, mechanical pulp such as GP, PGW, RMP, TMP, CTMP, CMP, and CGP, waste paper pulp such as DIP, and conventionally known pigments as a main component, binder and Various types of equipment such as long net paper machine, circular net paper machine, twin wire paper machine, etc. are mixed by using one or more kinds of various additives such as sizing agent, fixing agent, yield improving agent, cationizing agent and paper strength enhancing agent. And a base paper provided with a size press or an anchor coat layer of starch, polyvinyl alcohol or the like on the base paper. The basis weight of the support is usually 40 to 300 g / m ² , but is not particularly limited.

  The pigment of the ink receiving layer in the present invention contains a synthetic amorphous silica pigment and a urea / formaldehyde resin, but other pigments may be used in combination. When other pigments are used in combination, the amount is 10% by mass or less based on the total amount of synthetic amorphous silica and urea / formaldehyde resin. 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 and melamine resins.

  The urea / formaldehyde resin used in the present invention is preferably one having an average particle diameter of 1 to 10 μm, and particularly preferably 1 to 8 μm because high glossiness and high ink absorbability can be obtained.

  Further, the synthetic amorphous silica of the ink receiving layer in the present invention preferably has an oil absorption amount of 200 ml / 100 g or more, more preferably 240 to 400 ml / 100 g in the measurement method defined by JIS-K5101. Ink absorbability is obtained, which is preferable.

  When the mass ratio (A: B) of the synthetic amorphous silica (A) and the urea-formaldehyde resin (B) in the ink receiving layer is 30:70 to 80:20, the coating layer strength and image clarity are high. Is preferable. More preferably, it is 40: 60-80: 20.

  The ink receiving layer preferably contains a binder. Examples of the binder include various derivatives such as polyvinyl alcohol or silanol-modified products thereof, carboxylated products, and cationized products, conjugated diene copolymer latexes such as styrene-butadiene copolymers and methyl methacrylate-butadiene copolymers, acrylic resins, and the like. Acrylic polymer latex such as acid ester and methacrylic acid ester polymers or copolymers, vinyl polymer latex such as ethylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, etc. Examples thereof include a functional group-modified polymer latex and a polyurethane resin latex using a functional group-containing monomer such as a carboxy group. Among these, silanol-modified polyvinyl alcohol, ethylene-vinyl acetate copolymer latex, and styrene-butadiene copolymer latex are preferred, and at least one of these can be selected and used.

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

  Furthermore, in the ink receiving layer, as an additive, a dye fixing agent (various cationic resins), a pigment dispersant, a thickener, a fluidity improver, an antifoaming agent, an antifoaming agent, a release agent, a sizing agent, A penetrating agent, a coloring dye, a coloring pigment, a fluorescent brightening agent, an ultraviolet absorber, an antioxidant, an antiseptic, a baitproofing agent, a wet strength enhancer, a dry strength enhancer, and the like can be appropriately blended.

  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 added, the color is improved because the dye is captured in the ink receiving layer. 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 of the ink receiving layer due to dripping or moisture absorption of water is suppressed.

The coating amount of the ink receiving ^{layer, 5g / m 2 ~20g / m} 2 is good ink absorption and image clarity can be obtained, preferably. Further, the ink receiving layer can be applied by dividing a certain coating amount into several times.

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

  The pigments used in the glossy layer in the present invention are light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina (gas Phase method alumina, δ-alumina, θ-alumina), alumina hydrate (boehmite, pseudoboehmite), inorganic pigments such as aluminum hydroxide, styrene plastic pigment, acrylic plastic pigment, polyethylene, microcapsule, urea resin, Examples thereof include organic pigments such as melamine resins. Ultrafine inorganic pigments such as colloidal silica, alumina, and alumina hydrate, which have an extremely small average particle size, are more preferable because transparency of the recording layer is improved and printing density is increased. In particular, colloidal silica or pseudoboehmite alumina hydrate is preferable because it provides high gloss.

  From the viewpoint of increasing the printing density, the colloidal silica is preferably cationized. This is because the particle surface charge is a cation, which is insoluble in sulfonic acid groups, carboxylic acid groups, amino groups, etc. in direct dyes and water-soluble acidic dyes which are dye components in ink due to electrical interaction. This is because a salt is formed to fix the dye component in the glossy layer.

  When the glossy layer contains pseudoboehmite alumina hydrate and cationized colloidal silica as a pigment in a mass ratio of 95: 5 to 50:50, high image clarity and print density can be obtained. preferable.

  The glossy layer preferably contains a binder. Examples of such binders include natural polymers such as casein, gelatin, and soybean protein, starch derivatives such as etherified starch and phosphate esterified starch, and natural polymers such as cellulose derivatives such as carboxyl cellulose and hydroxyethyl cellulose and derivatives thereof. , And various saponification polyvinyl alcohols or various derivatives thereof such as silanol-modified products, carboxyl-modified products, and cation-modified products, water-soluble polymers such as polyethylene oxide, polyethylene glycol, polyacrylamide, and polyvinylpyrrolidone, melamine resins, urea resins, Various water-soluble synthetic polymers such as polyurea polyamide resin and derivatives thereof such as carboxyl-modified, amide-modified and cation-modified products, styrene-butadiene, acrylate and methacrylate, ethylene Vinyl acetate, synthetic polymer emulsion of polyurethane or the like, latex and its carboxyl, amides, and modified derivatives and cationic modified product by various amines groups.

  The binder content in the glossy layer is preferably from 1 to 30% by mass with respect to the pigment, since good coating layer strength and ink absorbability can be obtained. More preferably, it is 3-30 mass%.

  Further additives include cationic dye fixing agents, pigment dispersants, thickeners, fluidity improvers, viscosity stabilizers, pH adjusters, surfactants, antifoaming agents, foam suppressors, mold release agents, foaming agents. Agents, penetrants, colored dyes, colored pigments, white inorganic pigments, white organic pigments, fluorescent brighteners, UV absorbers, antioxidants, leveling agents, preservatives, antibacterial agents, water resistance agents, etc. It can also be added as appropriate as long as the purpose is not impaired.

  Various devices such as various blade coaters, roll coaters, bar coaters, rod blade coaters, comma coaters, lip coaters, curtain coaters, short dwell coaters, and size presses can be used for applying the glossy layer.

When the coating amount of the glossy layer is 5 to 30 g / m ² , high image clarity and ink absorbability are obtained, which is preferable. More preferably, it is 5-20 g / m < ² >.

  In the present invention, the gloss developing layer is cast. As described above, the cast treatment includes a direct method, a rewet method, a coagulation method, and the like. In the present invention, the coagulation method is preferably used, and the present invention can be achieved by coagulating the glossy layer. The objectives of the period are achieved at a higher level.

  The coagulation method is a processing method in which a recording layer coated on a support is treated with a coagulating liquid when it is in a fluid state and gelled. The gelated recording layer is heated and cast. Pressed against the drum and dried. The coagulation liquid contains a coagulant. Examples of the coagulant include salts with sodium, potassium, calcium, magnesium, barium, zinc, lead, cadmium, ammonium, etc. such as formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid, sulfuric acid, carbonic acid, and boric acid, Examples thereof include borax and various borates, and one or more can be selected and used. The concentration of the coagulant in the coagulation liquid is preferably in the range of 0.5 to 6% in terms of anhydride, more preferably 1 to 5%.

  In the coagulation liquid, as additives, for example, pigment dispersants, water retention agents, thickeners, antifoaming agents, antiseptics, colorants, water resistance agents, wetting agents, plasticizers, fluorescent dyes, ultraviolet absorbers, Known auxiliary agents such as antioxidants can be added as appropriate.

  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. Moreover, the particle diameter shown in an Example and a comparative example is an average particle diameter calculated | required by the dynamic light scattering method.

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 a pulp slurry. Add 6 parts of talc as a filler, 0.5 part of alkyl ketene dimer as a sizing agent, 1.0 part of polyacrylamide and 2.0 parts of cationized starch as a dry paper strength enhancer, and dilute with water to make a 1% slurry. It was. This slurry was made with a long paper machine so as to have a basis weight of 150 g / m ² to prepare a support. On one side of this support, coating liquid a as an ink receiving layer was applied and dried by an air knife coater so that the coating amount after drying was 10 g / m ^2, and on the ink receiving layer thus obtained. The coating liquid b of the gloss developing layer was applied using an air knife coater so that the coating amount after drying was 10 g / m ^2, and the coated surface had fluidity and was treated with a coagulation liquid. The ink-jet recording medium of the present invention was obtained by casting by a solidification method in which it was pressed against a cast drum heated to 100 ° C. and dried.

<Ink-receiving layer coating solution a>
As synthetic amorphous silica (A), 50 parts of synthetic amorphous silica (thyloid ED5; oil absorption 300 ml / 100 g, manufactured by Grace), urea / formaldehyde resin (PERGOPAK M3; oil absorption as urea / formaldehyde resin (B)) Amount 310 ml / 100 g, average particle size 7 μm, 50 parts by MARTINSWERK, silanol-modified polyvinyl alcohol (R-1130, Kuraray) 20 parts, styrene-butadiene copolymer latex (Luckster DS226, Dainippon Ink & Chemicals, Inc.) 10 parts by weight in a solid content and 10 parts by weight in a cationic dye fixing agent (Smilease Resin 1001, manufactured by Sumitomo Chemical Co., Ltd.) in water and uniformly dispersed to obtain an ink having a solid content concentration of 18%. A receiving layer coating solution a was prepared.

<Glossy layer coating liquid b>
50 parts of cationized colloidal silica (Snowtex ST-AK, manufactured by Nissan Chemical Industries), 50 parts of alumina hydrate with a pseudoboehmite structure and an average particle size of 50 nm, cationic acrylic resin emulsion (glass transition temperature 60 ° C.) 10 parts, 10 parts of polyvinyl alcohol (PVA117, manufactured by Kuraray Co., Ltd.) and 3 parts of a release agent (nonionic oleic acid emulsion) are mixed and uniformly dispersed to give a glossy layer coating liquid b having a solid content concentration of 20%. Prepared.

<Adjustment of coagulation liquid>
A coagulation solution of 4% calcium formate (anhydrous equivalent) was prepared.

  Ink receiving layer coating solution a was similarly prepared except that synthetic amorphous silica (A) was changed to 70 parts and urea / formaldehyde resin (B) was changed to 30 parts. Otherwise, the ink jet recording medium of the present invention was obtained in the same manner as in Example 1.

  In the ink-receiving layer coating solution a, the urea-formaldehyde copolymer (B) was changed to urea-formaldehyde resin (PERGOPAK M5; oil absorption 310 ml / 100 g, average particle size 4 μm, manufactured by MARTINSKERK). An ink receiving layer coating solution was prepared in the same manner as in Example 1 except that an ink jet recording medium of the present invention was obtained.

  The ink receiving layer was similarly used except that the synthetic amorphous silica (A) in the ink receiving layer coating liquid a was changed to synthetic amorphous silica (thyroid 74X6500; oil absorption 200 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.

(Comparative Example 1)
In the ink receiving layer coating liquid a, the urea-formaldehyde resin (B) is replaced with urea-formaldehyde resin (PERGOPAK M; oil absorption 300 ml / 100 g, average particle diameter 9 μm, MARTINSWERK, without containing the synthetic amorphous silica (A). The ink-receiving layer coating solution was prepared in the same manner except that the amount was changed to 100 parts, and the ink jet recording medium of Comparative Example was obtained in the same manner as in Example 1 except that.

(Comparative Example 2)
In the ink-receiving layer coating liquid a, the synthetic amorphous silica (A) is added to the synthetic amorphous silica (thyroid 74X6500; oil absorption 200 ml / 100 g, manufactured by Grace) without the urea / formaldehyde resin (B). An ink-receiving layer coating solution was prepared in the same manner except that the amount was changed to 100 parts, and an ink jet recording medium of a comparative example was obtained in the same manner as in Example 1 except that.

(Comparative Example 3)
The ink receiving layer coating solution was similarly used except that the urea-formaldehyde resin (B) in the ink receiving layer coating solution a was changed to calcium carbonate (Tamapearl 222H; oil absorption 47 ml / 100 g, manufactured by Okutama Kogyo Co., Ltd.). Otherwise, the ink jet recording medium of Comparative Example was obtained in the same manner as in Example 1.

(Comparative Example 4)
Ink receiving layer coating was similarly performed except that the synthetic amorphous silica (A) was changed to calcium carbonate (Tamapearl 222H; oil absorption 47 ml / 100 g, manufactured by Okutama Kogyo Co., Ltd.) in the ink receiving layer coating liquid a. A liquid was prepared, and the ink jet recording medium of the comparative example was obtained in the same manner as in Example 1 except that.

(Comparative Example 5)
Ink-receiving layer coating was similarly performed except that the urea / formaldehyde resin (B) in the ink-receiving layer coating solution a was changed to an acrylic resin (Viniblanc 2647, average particle size 70 nm, manufactured by Nissin Chemical Industry Co., Ltd.). A liquid was prepared, and the ink jet recording medium of the 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.

<Image clarity>
The image definition (C) defined by JIS H8686 was used. Using an image clarity measuring device (ICM-1DP manufactured by Suga Test Instruments Co., Ltd.), using an optical comb having a width of 2.0 mm, reading the maximum waveform (M) and the minimum waveform (m) at a reflection angle of 60 degrees, C = The image definition was determined as (M−m) / (M + m) × 100. When the image clarity of image clarity is 70% or more, the glossiness of appearance is high, indicating that it is excellent in aesthetic elements that look like printing paper.

<Opacity>
The value measured with a Hunter whiteness meter is read, and the opacity is determined as opacity (%) = (reflectance when using a black plate) / (reflectance when using a white plate) × 100. A larger value indicates higher opacity, and 100% opacity indicates complete opacity.

<Ink absorbability>
Using a commercially available ink jet recording apparatus (BJC420J, 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. Visual evaluation was made according to the following criteria.
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>
Using the ink jet recording apparatus, a solid pattern was printed with black ink, and the optical reflection density of the printed portion was measured with a Macbeth RD-918 model.

<Ink breakthrough>
Using the above-described ink jet recording apparatus, blue (cyan + magenta) heavy-color printing was performed on a central portion of a sample cut to A4 size in a size of 10 cm square, and then the optical reflection density was measured by Macbeth RD-918 type. Was measured, the non-printed portion / printed portion density ratio was calculated, and ink loss on the back surface was determined according to the following criteria. 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

<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.
Δ: The recording layer is slightly scraped off with a ballpoint pen, and there is a slight problem in reading the characters.
X: The recording layer is scraped off with a ballpoint pen, and the character cannot be read.

  From Table 1, in the ink jet recording medium sequentially having at least an ink receiving layer and a glossy expression layer provided by a casting method on the air-permeable support of Examples 1 to 4, the ink receiving layer is at least a synthetic non-coated pigment. The inkjet recording medium characterized by containing crystalline silica (A) and urea / formaldehyde resin (B) has image clarity comparable to silver salt photographic printing paper, and has high opacity and ink absorption. In addition to being obtained, excellent coating layer strength is obtained, which is favorable.

  On the other hand, when the urea / formaldehyde resin (B) is changed to calcium carbonate as in Comparative Example 3, the ink absorptivity and the print density are lowered, and the ink show-through is insufficient. In addition, as in Comparative Example 4, when the synthetic amorphous silica (A) is changed to calcium carbonate, the ink absorbability and the print density are lowered, and the ink show-through is insufficient. Further, when only synthetic amorphous silica is used as in Comparative Example 2, the ink absorptivity is good, but the image clarity is lowered, and the ink see-through is greatly deteriorated. Further, when only urea / formaldehyde resin is used as in Comparative Example 1, the printing density, image clarity, and coating layer strength are lowered. Also, as in Comparative Example 5, when the urea / formaldehyde resin (B) is changed to an acrylic resin, the ink absorbability is lowered, and even higher opacity cannot be obtained, making it difficult to see through the ink. In either case, satisfactory print quality could not be obtained.

Claims (6)

  In an inkjet recording medium having at least an ink receiving layer and a glossy layer provided by a casting method on a gas-permeable support in order, the ink receiving layer is at least a synthetic amorphous silica (A) and urea / formaldehyde as pigments An ink jet recording medium comprising a resin (B).   2. The ink jet recording medium according to claim 1, wherein an oil absorption amount of the synthetic amorphous silica (A) is 200 ml / 100 g or more in a measuring method defined in JIS-K5101.   The inkjet recording medium according to claim 1, wherein the urea-formaldehyde resin (B) has an average particle diameter of 1 to 10 μm.   The inkjet recording medium according to claim 1, 2 or 3, wherein a mass ratio (A: B) of the synthetic amorphous silica (A) and the urea-formaldehyde resin (B) is 30:70 to 80:20.   The inkjet recording medium according to claim 1, wherein the glossy expression layer is provided by a solidification method.   The inkjet recording medium according to claim 1 or 5, wherein the glossy layer contains pseudoboehmite alumina hydrate and cationized colloidal silica in a mass ratio of 95: 5 to 50:50.