JP2006095800A - Manufacturing method of inkjet recording cast-coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording cast-coated paper, which has high ink absorbency and high strength of the coating layer of an under layer. <P>SOLUTION: After the under layer including a pigment and a binding agent is provided on a support, the surface of the under layer is calendered with a rough surface roll under unheated state. Then, an ink accepting layer is provided on the under layer by a casting method under the condition that the center-line mean roughness (Ra) according to JIS B 0601 of the surface of the rough surface roll is preferably set to be 1-10 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing cast-coated paper suitable for inkjet recording.

  The ink jet recording method is a recording method in which fine droplets of ink are ejected by various methods to form images and characters on a recording material such as paper. Noise is low, and full color and high speed recording are easy. It has been widely used as various printers and plotters because of its low cost. In recent years, as a result of the drastic miniaturization of ink droplets and improvement of ink, the image quality has further improved, and until the level of images approaching that of a silver salt photograph is obtained, as represented by photo-type ink inkjet printers. Therefore, an increasing number of users print directly digital images taken with a digital camera or the like with an inkjet printer.

  The ink jet recording method ejects ink droplets from a nozzle toward a recording medium at a high speed, and in particular, in a high-quality ink jet printer called a photo type, a light color ink is used in addition to four colors of CMYK. Is discharged. For this reason, the recording medium is required to absorb a large amount of ink promptly. In consideration of ink absorption and ink bleeding, ink jet recording media are generally provided with an ink receiving layer composed of a porous pigment such as silica and a binder resin.

  In addition, with the spread of computers and digital cameras, images close to silver halide photographs have been demanded, and photographic glossiness has been demanded for inkjet recording paper. Examples of a method for imparting gloss to ink jet recording paper include a super calender method for smoothing the surface of an ink receiving layer to impart gloss, or a mirror-like shape in which an ink receiving layer in a wet or plastic state is heated. There is a cast coating method in which the surface of the recording paper is pressed onto the surface of the drum (cast drum) and the mirror surface is copied onto the surface of the recording paper as it is dried.

  As a typical cast coating method, there are the following three methods. That is, a direct method in which the coating liquid applied to the support is pressure-bonded to a heated cast drum in a state in which the coating liquid is not dried at all; Rewet cast coating method in which pressure is applied to a heated cast drum after returning to a plastic state again with a wet liquid, and the coating liquid applied to the support is treated with a coagulation liquid and has no fluidity It is a coagulation method in which a gel is heated and pressed on a cast drum. These cast coating methods are common in that a high gloss coating layer surface is obtained by copying a mirror-like drum surface.

  On the other hand, in order to impart sufficient ink absorbability to inkjet recording paper, it is common to increase the dry coating amount of the ink receiving layer. However, when the ink receiving layer is provided by the cast coating method, it is difficult to set the coating amount of the ink receiving layer large because the drying efficiency is poor. For this reason, it has been studied to make the ink receiving layer multi-layered, to provide at least the outermost layer by a cast coating method to give gloss, and to provide insufficient ink absorbability by providing an under layer.

For example, Patent Document 1 discloses an inkjet in which the pigment in the under layer contains synthetic amorphous silica (A) having an oil absorption of 200 ml / 100 g or more and heavy calcium carbonate (B) having a particle diameter of 2 μm or less in a specific weight ratio. Cast coated paper has been proposed.
Furthermore, in order to improve the surface glossiness of the ink jet recording medium, it is possible to perform thermal calendering on the under layer using a mirror or rough metal roll on the surface of the under layer according to the purpose. Japanese Patent Application Laid-Open No. H10-228688 discloses that a rough surface roll is used for the under layer in order to matte the surface of the recording medium and thermal calendaring is performed.

JP 2003-285543 A JP 2002-192829 A Japanese Patent Laid-Open No. 2002-200839

  However, in the case of Patent Document 1, since a pigment having a relatively small oil absorption amount such as calcium carbonate is used for the under layer, the coating layer strength of the under layer can be increased, but the ink absorbability is insufficient. It was. Moreover, when performing a calendar process using the metal roll heated at about 80 degreeC like the technique of patent document 2 or patent document 3, the space | gap in a coating layer at the time of a heat calendar by the thermoplastic resin contained in an under layer As a result, the ink absorbability is still insufficient.

Although it is conceivable to reduce the amount of binder in the under layer in order to increase ink absorbency, the coating layer strength is weakened, and not only paper dust is generated during cutting, but also coated paper coated with the under layer etc. When winding up, a part of the coating layer may be lost and may be caught during winding. In particular, in a highly smooth cast paper, there is a problem that a dent caused by a part of the coating layer missing on the surface of the coating layer occurs, which impairs the appearance.
In view of the above, development of ink-jet recording cast coated paper that can achieve both ink absorbability and coating layer strength is desired. Accordingly, an object of the present invention is to provide a cast coated paper for ink jet recording which has high ink absorbability and high undercoat layer strength.

  As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by performing a calender treatment on the surface of the under layer using a rough roll and then providing an ink receiving layer thereon by a cast coating method. .

  That is, the above-mentioned problem of the present invention is that after providing an under layer containing a pigment and a binder on a support, the under layer surface is calendered by a rough roll without heating, and then the under layer This was achieved by a method for producing a cast-coated paper for ink-jet recording, characterized in that an ink-receiving layer coating layer is provided on the layer using a cast method. Moreover, it is preferable that the rough surface roll surface has a centerline average roughness (Ra) based on JIS-B-0601 of 1 to 10 μm, and in the calendering, the surface temperature of the rough surface roll is 70 ° C. or less. Is preferably carried out. Furthermore, it is preferable that synthetic amorphous silica exceeds 80% by mass in the pigment contained in the ink receiving layer. Further, the 20 ° specular gloss on the surface of the ink receiving layer is preferably 15% or more.

According to the present invention, sufficient ink absorbability can be obtained even when a large amount of ink is ejected when printing on an inkjet recording medium, and ink bleeding is eliminated.
Moreover, the coating layer strength of an under layer improves and it can prevent that an under layer peels from a support body. Furthermore, since the air permeability of the sheet provided with the under layer on the support is improved, the productivity when the coating layer is provided by the cast coating method is improved.

The method for producing the ink jet cast coated paper of the present invention will be described in detail below.
The method for producing a cast coated paper for ink jet according to the present invention comprises: forming an under layer on a support; then applying a calender treatment using a rough surface roll; and providing an ink receiving layer thereon by a cast coating method. The calendar process is preferably performed without heating.

(Under layer pigment)
The under layer of the present invention contains a pigment and a binder. As the pigment referred to in the present invention, one or more known white pigments can be used. For example, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, light calcium carbonate, heavy calcium carbonate, magnesium 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, lithopone, zeolite, hydrous halloysite, magnesium hydroxide, white inorganic pigments, styrene plastic pigment, acrylic plastic pigment, polyethylene, Organic pigments such as microcapsules, urea resins, and melamine resins are listed. These pigments can be used alone or in combination as appropriate. From the viewpoint of ink absorbability, porous pigments such as synthetic amorphous silica are preferred.

(Under layer binder)
As the adhesive contained in the under layer, various resins having a binder function are used. For example, cellulose-based adhesives such as methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose, and hydroxyethylcellulose, starch and modified products thereof, gelatin and modified products thereof, natural polymeric resins such as casein, pullulan, gum arabic, and albumin Or derivatives thereof, polyvinyl alcohol and modified products thereof, styrene-butadiene copolymer, styrene-acrylic copolymer, methyl methacrylate-butadiene copolymer, latex such as ethylene-vinyl acetate copolymer, emulsions, polyacrylamide And vinyl polymers such as polyvinylpyrrolidone, polyethyleneimine, polypropylene glycol, polyethylene glycol, and maleic anhydride or copolymers thereof. Preferably, it is a copolymer emulsion.

  In addition, other additives include cationic dye fixing agents, pigment dispersants, thickeners, fluidity improvers, viscosity stabilizers, pH adjusters, surfactants, antifoaming agents, antifoaming agents, and release agents. , Foaming agents, penetrating agents, colored dyes, colored pigments, white inorganic pigments, white organic pigments, fluorescent brighteners, UV absorbers, antioxidants, leveling agents, antiseptics, antibacterial agents, water resistant agents, wet paper A force enhancer, a dry paper strength enhancer, and the like can be appropriately added as long as the object of the present invention is not impaired.

  When providing this under layer, the method of coating is not specifically limited, A well-known coating method can be used. For example, supports by various devices such as air knife coater, curtain coater, slide lip coater, die coater, blade coater, gate roll coater, bar coater, rod coater, roll coater, bill blade coater, short dwell blade coater, size press, etc. Can be coated on top.

  As a means for drying after coating, a generally known method can be used and is not limited. For example, there are a method of conveying heated air generated by a heat source into a heated air heater, a method of passing the vicinity of a heat source such as a heater, and the like. The layer configuration of the under layer may be a single layer or a stacked configuration. In the case of a laminated structure, all the layers may be layers having the same composition, or may be a laminated structure with layers composed of other components.

  In the present invention, by applying a calender treatment using a rough surface roll after providing the under layer on the support, the coating layer strength of the under layer is reduced without reducing the ink absorbability and air permeability of the under layer. Can be raised. In the calendar process with the normal mirror roll, the calendar process is strongly performed on the entire under layer, whereas the calendar process with the rough roll at the same linear pressure is partially compared with the part where the calendar process is relatively strong. The part that is done weakly occurs. This relatively strongly calendered part is involved in improving the strength of the entire undercoat layer, and the relatively weakly calendered part is involved in preventing ink absorption and air permeability from being reduced. It is thought that a well-balanced under layer can be obtained.

  Further, if the roughness shape of the rough surface roll is too rough, the smoothness is extremely lowered, the glossiness of the ink receiving layer may be lowered, or the ink receiving layer may not be formed. The shape preferably has a 10-point average roughness (Rz) based on JIS-B-0601 of 1 to 10 μm. More preferably, it is the range of 1-6 micrometers.

  In the present invention, the “thermal calendar process” is not performed, which is performed while applying heat to the calendar roll like a soft calendar. Further, the calendar process in which the surface of the under layer is in contact with the mirror roll is not performed. When such a treatment is performed, pores existing in the under layer are crushed, and the ink absorbability and air permeability of the under layer are reduced. In the present invention, the calender roll is not heated during mat calendering, but heat may be generated due to friction between roll papers, and the surface temperature of the rough roll may be higher than room temperature. The surface temperature of the rough roll during the calendar treatment is preferably 70 ° C. or less, more preferably 60 ° C. or less.

  When calendering is performed using a rough roll, it is necessary to form a calender nip and pass a support provided with an under layer therebetween. In the present invention, the roll that forms the pair of the rough rolls is preferably an elastic roll, but the material of the coated elastic body is not particularly limited, and known materials such as cotton, asbestos, wool, plastic, and rubber can be used. If the coated elastic body is too soft, the effect of forming the surface of the coated paper becomes insufficient, and a problem arises in the durability of the elastic roll during operation. On the other hand, if it is too hard, the underlayer surface may have irregular smooth irregularities. Therefore, a preferable elastic roll hardness condition is a Shore D hardness of 80 ° or more, preferably in the range of 80 ° to 100 °.

The coating amount of the under layer is not particularly limited, but if it is too small, the effect of the under layer (ink absorbability) will not appear, and if it is too large, there will be many manufacturing difficulties and the effect will be saturated and the economy will be poor. . Therefore, a preferable range is 5 g / m ² or more and 30 g / m ² or less.

  In the ink-jet cast coated paper of the present invention, an ink receiving layer is formed on the under layer using a cast coating method. In the present invention, the ink receiving layer can be provided by a generally known cast coating method, but it is particularly preferable to provide it by a coagulation cast coating method. In the solidification method, since the coating layer is gelled and the degree of plasticization is high, it is possible to obtain a cast layer having an excellent surface feeling with less uneven gloss and uneven adhesion to the drum than the rewetting cast coating method. .

  The ink receiving layer contains a pigment and a binder. Known pigments constituting the ink receiving layer include synthetic amorphous silica, colloidal silica, alumina, calcium carbonate, magnesium carbonate, aluminum hydroxide, kaolin, calcined kaolin, talc, titanium dioxide, zinc oxide, and various plastic pigments. These pigments can be used, and one type or a plurality of types can be selected and used. Among these, porous pigments such as synthetic amorphous silica and alumina form a porous layer with excellent ink absorbability compared to other pigments, become relatively transparent in the coating layer, and are cast for inkjet recording. It is preferably used because ink color development is improved when recording on coated paper.

  As the binder constituting the ink receiving layer, starches such as oxidized starch and esterified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, proteins such as gelatin, casein and soybean protein, polyvinyl alcohol, polyvinylpyrrolidone, Examples of known binders include acrylic resins, styrene-acrylic resins, vinyl acetate resins, vinyl chloride resins, urea resins, urethane resins, alkyd resins, polyester resins, polycarbonate resins, styrene-butadiene latex, and derivatives thereof. One type or a plurality of types can be selected and used.

  In addition, the ink receiving layer may include a pigment dispersant, a water retention agent, a thickening agent, an antifoaming agent, a preservative, a colorant, a water resistant agent, a wetting agent, a plasticizer, a fluorescent dye, an ultraviolet absorber, Known auxiliaries such as antioxidants, release agents, pH adjusters, and cationic polymer electrolytes can be appropriately added.

  In particular, in the cast coated paper for inkjet recording of the present invention, it is preferable to provide an ink receiving layer containing polyvinyl alcohol in the ink receiving layer. By providing this ink receiving layer on the under layer, the strength of the ink receiving layer can be further increased compared to the case where this ink receiving layer is directly provided on the base paper, and powder omission can be improved. Although this reason is not certain, it is considered that the ink receiving layer and the under layer are firmly adhered. When blending polyvinyl alcohol in the binder, the polyvinyl alcohol in the binder component is preferably 30% by mass or more, and more preferably 50% by mass or more.

  The blending ratio of the pigment constituting the ink receiving layer and the binder can be changed according to the properties, formulation and support, and can be set as appropriate as long as the required quality such as ink absorbency is not impaired. The amount is preferably 5 to 30 parts by weight, more preferably 20 parts by weight or less, based on 100 parts by weight of the pigment. If the blending amount of the binder is small, the strength of the recording layer tends to decrease, and if the blending amount is large, the ink absorbability tends to decrease.

The method for applying the ink receiving layer coating liquid in the invention is not particularly limited, and a known coating method can be used. For example, support by various devices such as air knife coater, curtain coater, slide lip coater, die coater, blade coater, gate roll coater, bar coater, rod coater, roll coater, bill blade coater, short dwell blade coater, size press, etc. Can be coated on top.
In the present invention, the coating amount of the ink receiving layer needs to be 5 g / m ² or more in terms of solid content, and preferably 10 g / m ² or more and 30 g / m ² or less in order to recognize further effects of the present invention. preferable.

  When the ink receiving layer is provided by the coagulation cast coating method, a compound capable of coagulating or cross-linking the binder in the ink receiving layer can be used as the coagulant used in the coagulating liquid. For example, polyvinyl as the binder When alcohol is contained, borax, various borates, etc. are used as a coagulant. In particular, a treatment liquid containing boric acid and borate is preferable. By mixing and using boric acid and borate, it is easy to obtain a solidified state with an appropriate hardness, and an ink jet recording medium having a good gloss feeling can be obtained. If it contains casein, salt with formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid, sulfuric acid, carbonic acid, etc. and calcium, zinc, magnesium, sodium, potassium, barium, lead, cadmium, ammonium, etc. Can be used.

The re-wetting liquid used in the coagulation liquid and rewet cast coating method includes a pigment dispersant, a water retention agent, a thickener, an antifoaming agent, a preservative, a colorant, a water resistance agent, a wetting agent, a fluorescent dye, An ultraviolet absorber, a cationic polymer electrolyte, etc. can be added suitably. Examples of the method for applying the coagulating liquid and the rewetting liquid include a roll, a spray, and a curtain system, but are not particularly limited.
In the present invention, the 20 ° specular gloss on the surface of the ink receiving layer is preferably 15% or more. If it is in this range, it can be said that it has the same glossiness as a silver salt photograph. In order to improve the glossiness of the ink receiving layer surface, the under layer is preferably smooth. In addition, it is preferable to provide the ink receiving layer by a solidification cast coating method in terms of easy transfer of the shape of a mirror surface such as a cast drum.

(Support)
The support used in the present invention is not particularly limited as long as it is a support to which the under layer and the ink receiving layer can be applied, but preferably a paper support can be used. As the pulp constituting the paper preferably used, natural pulp, regenerated pulp, synthetic pulp or the like is used alone or in combination. As the natural pulp, pulps usually used for papermaking, that is, bleached chemical pulps such as softwood kraft pulp, hardwood kraft pulp, softwood sulfite pulp, hardwood sulfite pulp, and the like 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, cocoon, husk and trilobium, 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 particularly preferable.

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

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

  Examples of the dispersion aid include polyethylene oxide, polyacrylamide, and strawberry starch, and examples of the paper strength enhancer include anionic strength enhancers such as vegetable gum, starch, and carboxy-modified polyvinyl alcohol, cationized starch, and cationic poly. Cationic paper strength enhancers such as acrylamide and polyamide polyamine epichlorohydrin resin, and fillers include, for example, clay, kaolin, talc, heavy calcium carbonate, light calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, magnesium hydroxide, etc. Examples of the sizing agent include higher fatty acid salts, rosin derivatives such as rosin and maleated rosin, dialkyl ketene dimers, alkenyl or alkyl succinates, epoxidized fatty acid amides, polysaccharide esters, and the like. Miniumu, polyvalent metal salts such as aluminum chloride, cationic starch, cationic polymers such as polyamide polyamine epichlorohydrin resin as the pH adjusting agent hydrochloride, sodium hydroxide, sodium carbonate or the like is used.

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

  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 such as polyvinyl alcohol and 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, as well as petroleum resin emulsions and styrene as sizing agents. - 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, and clay, kaolin, talc, barium sulfate, and oxidation as pigments. Titanium or the like uses hydrochloric acid, caustic soda, sodium carbonate or the like as a pH regulator, and other additives such as dyes, fluorescent brighteners, antioxidants, and ultraviolet absorbers can be used in combination.

Hereinafter, the present invention will be described with reference to examples. In addition, this invention is not limited to an Example. Unless otherwise specified, all parts and% in the following mean parts by mass and% by mass.
<Production of support>
A pulp consisting of 100 parts of hardwood bleached kraft pulp (L-BKP) having a freeness of 300 ml c · s · f, 10 parts of talc, and 0.4 parts of cationic starch (Kate 304L: product name of Nippon SC Co., Ltd.) Paper making from a pulp slurry to which 1.0 part of aluminum sulfate, 0.1 part of a synthetic sizing agent, and 0.02 part of a yield improver were added using a paper machine, and a dry coating amount per side by a size press device Was impregnated on both sides so as to give a support of 1.5 g / m ² . The basis weight of the support was 170 g / m ² .

[Example 1]
(Formation of under layer)
On one surface of this support, 100 parts of synthetic amorphous silica (X-37B: manufactured by Tokuyama), 30 parts of polyvinyl alcohol (PVA117: manufactured by Kuraray), ethylene vinyl acetate emulsion (BE7000: manufactured by Chuo Rika Kogyo Co., Ltd.) ) 5 parts, 5 parts of a cationic resin (polyamine ammonia epichlorohydrin, molecular weight 100,000), 2 parts of a cationic sizing agent (SS335: manufactured by Nippon PMC), 0.5 parts of an antifoaming agent ( (Solid content: 23%) was applied with a blade coater such that the dry coating amount was 10 g / m ^2, and the surface was calendered with a rough surface roll (center line average roughness Ra: 4.5 μm) ( Mat calendar processing). (Line pressure: 120 kg / cm, roll temperature: 40 ° C., line speed: 120 m / min, facing roll: resin roll with Shore D hardness of 90 °)

(Formation of ink receiving layer)
Next, a coating solution of 10 g / m ^{2 is} applied on the coating surface of the under layer with a roll coater, and the coating layer is solidified using a coagulation solution while the coating layer is in a wet state, and then cast coater (cast drum) And an ink jet recording medium having a basis weight of 190 g / m ² was obtained.
Coating liquid: 100 parts of synthetic silica (Fine Seal X-37: manufactured by Tokuyama Corporation) as a pigment, 5 parts of latex (LX438C: manufactured by Sumitomo Chemical Co., Ltd.) as a binder and polyvinyl alcohol (PVA117: manufactured by Kuraray Co., Ltd.) 24 Part and a sizing agent (Polymarlon 360: manufactured by Arakawa Chemical Industries) were mixed to prepare an aqueous coating solution having a concentration of 20%.
Coagulating liquid: 2% borax, 2% boric acid (mass ratio of borax / boric acid = 1/1, calculated in terms of Na ₂ B ₄ O ₇ and H ₃ BO ₃ ), release agent (FL-48C: Toho Chemical) Coagulation liquid was prepared by blending 0.2% (manufactured by Kogyo).
[Example 2]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the calendering conditions for the underlayer coated paper of Example 1 were changed to a linear pressure of 60 kg / m.
[Example 3]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the calendering condition for the under-layer coated paper of Example 1 was 60 ° C.

[Comparative Example 1]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the calendar treatment was not performed on the underlayer coated paper of Example 1.
[Comparative Example 2]
The calendar process for the under-layer coated paper of Example 1 was performed except that the calendar process (soft calendar process) was performed using a mirror roll having a center line average roughness Ra of 0.5 μm instead of the rough roll. An ink jet recording medium was obtained in the same manner as in Example 1. The mirror roll was calendered so as to contact the surface of the under layer.
[Comparative Example 3]
The calendar process (soft calender process) was performed using a mirror roll with a center line average roughness Ra of 0.5 μm instead of the rough roll, instead of the calendar process on the underlayer coated paper of Example 2. An ink jet recording medium was obtained in the same manner as in Example 2.
[Comparative Example 4]
The pigment used for forming the under layer of Comparative Example 1 is a cationic dispersant comprising synthetic amorphous silica having an oil absorption of 200 ml / 100 g or more and heavy calcium carbonate containing 95% by weight or more of particles having a particle diameter of 2 μm or less. In the same manner as in Comparative Example 1, except that the pigment dispersion was replaced with synthetic amorphous silica: heavy calcium carbonate = 50: 50 (FMT-IJ511: manufactured by Pimatech) in the presence of A medium was obtained.

(Evaluation)
The ink jet recording media obtained in Examples and Comparative Examples were evaluated by the following methods. In each item, an evaluation of ◯ or more can be put into practical use.
(1) Recording suitability In the recording test, a predetermined pattern was recorded using an ink jet printer (PM-950C: trade name, manufactured by Epson Corporation) using a dye ink, and evaluated according to the following criteria.
a, Ink absorption (bleeding)
A solid image of red and green was prepared with spreadsheet software “Excel”, and bleeding was visually evaluated at the boundary between the printed red and green mixed colors.
A: The color boundary portion is clearly separated ○: The color boundary portion is slightly blurred among those with slight bleeding Δ: The color boundary portion is slightly blurred with a degree of bleeding Relatively large x: Color boundary portion with very large bleeding b, ink absorbency (unevenness)
The unevenness generated in the recorded image portion was visually evaluated.
A: The image is a vivid image with no color unevenness. O: The image has a slight degree of unevenness. Δ: The image has a slight unevenness. Is very big

(2) Coating layer strength A transparent adhesive tape having a width of 18 mm was applied to the sample, and the force required to peel it off was measured using a digital force gauge.
A: The measured value is 1000 gf or more, and there is no paper peeling.
○: The measured value is 700 gf or more, and there is no paper peeling.
(Triangle | delta): A measured value is 500 gf or more and less than 700 gf. Or more than that, there is paper peeling.
X: The measured value is less than 500 gf.

(3) Casting operability When the ink receiving layer is provided by a casting method, the dirt on the cast drum surface was visually evaluated. ○: No dirt on the surface.
Δ: The surface is slightly cloudy.
X: A part of the coating layer (ink receiving layer) adheres to the surface.

(4) Air permeability About the sheet before forming the ink receiving layer (sheet having only the under layer formed on one side of the support), the Japan Paper Pulp Technology Association (J.TAPPI) NO. The air permeability was measured according to 5.

A: The measured value is less than 200 seconds.
○: The measured value is 200 seconds or more and less than 400 seconds.
Δ: The measured value is 400 seconds or more and less than 600 seconds.
X: The measured value is 600 seconds or more.

(5) Blank paper glossiness Measured according to the method of JIS K7105, and the 20 ° specular glossiness of the blank paper portion was defined as the blank paper glossiness. When the glossiness of the blank paper is 15% or more, the glossiness is equivalent to that of a silver salt photograph.

○: The measured value is 15% or more, and the white paper has a transparent feeling.
Δ: The measured value is 15% or more, and the white paper has a cloudy appearance.
X: The measured value is less than 15%.

As is clear from Table 1, in the case of Example 1, the air permeability was excellent despite the calendar treatment, and the cast coating property was also excellent. In addition, Example 1 had a sufficiently high coating layer strength, and was excellent in terms of bleeding and unevenness during ink jet recording and white paper gloss.
In the case of Example 2 in which the linear pressure was lowered, an ink jet recording medium excellent in ink absorbability and air permeability such as bleeding and unevenness was obtained. In Example 3 where the roll temperature was increased, the coating layer strength and white paper gloss were improved, but a slight tendency was observed in terms of ink absorption and air permeability.

On the other hand, in the case of Comparative Example 1 in which the calendar process was not performed, the glossiness of the blank paper after the cast coating was reduced as the under layer strength was reduced. This is probably because the calendar process was not performed, and thus the effect of improving the strength by the calendar process was not obtained. Moreover, since the smoothness of the under layer was insufficient, the glossiness of blank paper was also inferior.
Moreover, in the case of the comparative example 2 which performed the calendar process with the mirror surface roll by the same linear pressure as Example 1, although underlayer intensity | strength was enough, since air permeability was inferior, cast coating property deteriorated. Also, the ink absorbency was inferior. Furthermore, in the case of Comparative Example 3 in which the calender treatment was performed with a mirror roll under the condition where the linear pressure was lowered, the under layer strength, the ink absorbability, the cast coating property, and the white paper gloss were insufficient, and the balance was good. Inkjet recording media could not be obtained. From this result, it was found that the mirror roll calender cannot improve all of the under layer strength, ink absorbability and cast coatability in a well-balanced manner.
Further, in Comparative Example 4 in which calcium carbonate was blended as a pigment component in the under layer paint, the coating layer strength was sufficient, but the ink absorbability was inferior. Further, since the calendar process was not performed, the smoothness of the under layer was low and the glossiness of the white paper was inferior.

Claims (5)

After providing an under layer containing a pigment and a binder on the support, the under layer surface is calendered with a rough roll without heating, and then cast on the under layer. A method for producing a cast-coated paper for ink-jet recording, comprising providing an ink receiving layer. 2. The method for producing cast-coated paper for ink jet recording according to claim 1, wherein the rough roll surface has a center line average roughness (Ra) of 1 to 10 μm based on JIS-B-0601. The method for producing an inkjet recording medium according to claim 1, wherein the calendering is performed at a surface temperature of a rough roll of 70 ° C. or less. The method for producing cast-coated paper for ink-jet recording according to any one of claims 1 to 3, wherein the pigment contains synthetic amorphous silica in an amount exceeding 80 mass%. The method for producing a cast-coated paper for ink-jet recording according to any one of claims 1 to 4, wherein the surface of the ink receiving layer has a 20 ° specular gloss of 15% or more.