JP2009061649A - Recording medium for ink jet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recording medium having superior operability and glossy appearance even when a cast coat layer is formed by using a highly viscous coating liquid for a cast coat containing polyvinyl alcohol high in polymerization degree. <P>SOLUTION: The recording medium for an ink jet is obtained by coating the surface of a supporting body with a coating liquid for a cast coat at least comprising a pigment and polyvinyl alcohol having a saponification degree of ≥90% and a polymerization degree of ≥2,000 as a binder, so as to provide a coated layer, and, in a meanwhile where the surface of the coated layer lies in a wet state, pressure-welding and drying the coated layer, so as to be a heated mirror face. The coating liquid for a cast coat comprises an acetylene glycol compound, and also, the acetylene glycol compound is comprised by ≤1 pts.mass to 100 pts.mass of the pigment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inkjet recording medium having a cast coat layer for printing by an inkjet recording method.

  Recording media used in the ink jet recording method are roughly classified into a plain paper type having a texture similar to so-called high-quality paper and PPC paper, and a coated paper type clearly having an ink receiving layer. Further, coated paper type recording media are roughly classified into a gloss type having gloss in the ink receiving layer and a mat type having no gloss. Ink-jet recording media having a gloss comparable to that of conventional silver salt photographs have severe quality requirements due to remarkable progress in recent ink-jet printers and the remarkable spread of digital cameras, and technical development is actively being carried out.

  The quality characteristics required for such glossy inkjet recording media include high glossiness, fast ink drying speed, high print density, and no ink overflow or bleeding. Furthermore, an ink jet recording medium is often processed before or after ink jet recording, and is required to have less paper powder during cutting.

  Ink jet recording media use pigments having a large specific surface area such as silica and alumina in order to ensure ink absorbability. In the glossy inkjet recording medium, glossiness can be imparted by providing the outermost ink receiving layer by a cast coating method (hereinafter, the ink receiving layer provided by the cast coating method is referred to as a cast coating layer). Usually, the cast coat layer is composed of fine particle pigments such as colloidal silica, vapor phase method silica and vapor phase method alumina, and a binder (polyvinyl alcohol is widely used) for binding these fine particle pigments. The However, when the fine particle pigment is contained, when the coating liquid is applied and then dried, the strong capillary force acting between the voids of the fine particle pigment tends to cause the aggregation state to break, and the cast coat layer tends to crack. There was a major drawback. When cracks occur, not only the surface feel is inferior, but also when the image is printed with an ink jet printer, the image quality deteriorates, such as unevenness in the printed portion and a decrease in optical density. In order to solve the cracks, it is better to add a large amount of binder, but problems such as ink overflow and bleeding occur. In order to solve this, for example, the coating liquid described in Patent Document 1 is heated and applied, and then cooled and gelled to form a coating layer, or the coating liquid described in Patent Document 2 A method of containing polyvinyl alcohol having a high degree of polymerization has been proposed.

  In the cast coating method, high gloss can be obtained by copying the mirror drum surface of the cast coater. Patent Document 3 describes that a cast coat layer is uniformly released from a mirror drum and high gloss is obtained, and fatty acid salts, polyethylene wax, or lecithin is contained in the cast coat layer as a release agent. Yes.

Japanese Patent Laid-Open No. 2004-230761 JP 2007-152834 A Japanese Patent Laid-Open No. 2002-337446

However, in each of the techniques disclosed in Patent Documents 1 and 2 described above, it was possible to prevent cracking, but an ink jet recording medium excellent in operability and feel has not been obtained. The production method of Patent Document 1 requires temperature control of the coating liquid and is poor in productivity. In the method of Patent Document 2, since the coating liquid has a high viscosity, bubbles are generated and sufficient gloss (surface feel) is obtained. ) Could not get. Further, in Patent Document 3, even if the peelability from the mirror drum is improved, cracks occur in the cast coat layer, and sufficient gloss cannot be obtained.

  The present invention has been made to solve the above-mentioned problems, and even when a cast coat layer is formed using a coating liquid for cast coat that contains polyvinyl alcohol having a high polymerization degree and has a high viscosity, An object of the present invention is to provide an ink jet recording medium excellent in operability and surface feeling.

As a result of investigations to solve the above problems, the inventors have found that the above problems can be solved by combining the coating liquid with an acetylene glycol-based material and polyvinyl alcohol having a low saponification degree.
That is, the present invention provides a coating layer on a support by applying a coating liquid for cast coating containing at least a pigment and polyvinyl alcohol having a saponification degree of 90% or more and a polymerization degree of 2000 or more as a binder. An ink jet recording medium comprising a cast coat layer formed by pressure-drying a heated mirror surface while the surface of the coat layer is in a wet state, wherein the cast coat coating solution is provided. Contains an acetylene glycol compound, and the acetylene glycol compound is contained in the cast coat coating solution in an amount of 1 part by mass or less based on 100 parts by mass of the pigment. The acetylene glycol compound contained in the coating liquid for cast coating is an ethylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and average addition of ethylene oxide. When the number of moles is 0 or 1, the effect is further great, which is preferable.

According to the present invention, it is possible to obtain a high-gloss ink-jet recording medium having excellent surface feel and no fine cracks.

Details of the present invention will be described below.
(Support)
As the support used in the present invention, any support can be used as long as it is in the form of a sheet, but a support having air permeability is preferable. For example, paper such as coated paper and uncoated paper can be suitably used for the support. The main components of paper are pulp and internal filler. As the pulp, any known pulp can be used. As raw material pulp of the paper, chemical pulp (coniferous bleached or unbleached kraft pulp, hardwood bleached or unbleached kraft pulp, etc.), mechanical pulp (ground pulp, thermomechanical pulp, chemisermomechanical pulp, etc.), deinked pulp Etc. can be used alone or in admixture at any ratio. It is preferable to use LBKP having high whiteness and excellent texture for the ink jet recording medium.

The pulp can be made highly white by bleaching. Pulp bleaching methods include chlorine bleaching using a combination of chemicals such as elemental chlorine, hypochlorite, chlorine dioxide, oxygen, hydrogen peroxide, caustic soda, bleaching method using chlorine dioxide (ECF), There is a method called bleaching (TCF) in which ozone / hydrogen peroxide is mainly used without using any chlorine compound. Of these, it is preferable that bleaching is performed by a method such as ECF or TCF since the load of an organic chlorine compound formed by a chlorine bleaching method may adversely affect the environment. Further, in ECF, chlorine dioxide reacts selectively with lignin, so that the whiteness of the pulp can be increased without damaging the cellulose, which is more preferable.
The internal filler is added (internal addition) for the purpose of improving the opacity and whiteness of paper. For example, clay, kaolin, talc, heavy calcium carbonate, light calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide Although white pigments such as magnesium hydroxide can be used, addition of calcium carbonate, particularly light calcium carbonate is preferred because high whiteness is easily obtained.
The above-described pulp is beaten by a beating machine such as a double disc refiner in order to improve papermaking suitability and various characteristics of paper 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 pH of the pulp may be acidic, neutral or alkaline.

The beaten pulp slurry can be made by a paper machine such as a long net paper machine, a twin wire paper machine, or a round net paper machine to obtain a support. In this case, the pulp slurry usually used for paper making is used. It is possible to add a dispersion aid, a dry paper strength enhancer, a wet paper strength enhancer, a sizing agent, a fixing agent, a pH adjuster, a dye, a colored pigment, a fluorescent whitening agent, and the like.
In addition, a liquid containing various additives such as a water-soluble polymer additive is applied to the support by an on-machine or off-machine using a tab size, size press, gate roll coater or film transfer coater. It is possible to work.

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, polyvinyl alcohol derivatives such as carboxy-modified polyvinyl alcohol, carboxymethyl cellulose, 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, etc. Water-soluble polymers such as maleic anhydride resins, water-based polymer adhesives such as thermosetting synthetic resins such as melamine resins and urea resins, etc. are used. In addition, petroleum resin emulsions and styrene are used 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.
The support prepared by the above method preferably has a Steecht sizing degree of 5 seconds or more from the viewpoint of coating properties in the subsequent steps, but if it is 50 seconds or more, the coating layer described later More preferably, it is possible to minimize the permeation of.

(Undercoat layer)
In the present invention, an undercoat layer formed by applying or impregnating an undercoat layer coating solution containing a cationic substance on a substrate can be used as the support. The undercoat layer contains at least a binder and a cationic substance, and agglomerates at the interface between the undercoat layer and the cast coat layer, thereby suppressing penetration of the coating liquid for the cast coat layer into the undercoat layer. The binder of the undercoat layer is preferably a water-soluble binder from the viewpoint of ink absorbability, for example, starches such as starch, oxidized starch and esterified starch, polyvinyl alcohol, silyl-modified polyvinyl alcohol, cation-modified polyvinyl alcohol and the like. Polyvinyl alcohols; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; casein; gelatin; proteins such as soy protein; water-soluble resins such as polyvinyl pyrrolidone can be used, and starches and polyvinyl alcohol are preferred from the viewpoint of strength and absorbability.

In addition to the above, the undercoat layer includes coating pigments such as calcium carbonate, silica, alumina, aluminum hydroxide, pseudoboehmite, kaolin, and titanium, thickeners, antifoaming agents, antifoaming agents, pigment dispersants, Release agent, foaming agent, pH adjuster, surface sizing agent, coloring dye, coloring pigment, fluorescent dye, ultraviolet absorber, antioxidant, light stabilizer, preservative, water resistance agent, surfactant, wet paper You may add a force enhancer, a water retention agent, etc. suitably in the range which does not impair the effect of this invention.
The coating method for the undercoat layer on the support is as follows: blade coater, air knife coater, roll coater, brush coater, kiss coater, squeeze coater, curtain coater, die coater, bar coater, gravure coater, gate roll coater In addition, a known coating machine such as a short dwell coater or a size press can be appropriately selected from coating methods using on-machine or off-machine. Moreover, although the drying method of a coating layer is not specified in particular, a steam heater, a gas heater, an infrared heater, an electric heater, a hot air heater, a microwave, a cylinder dryer, etc. can be used.
Moreover, you may provide the coating layer which has ink absorptivity, adhesiveness, and other various functions between a support body and an undercoat layer.

(Cast coat layer)
In the present invention, a cast coat layer having high gloss is applied and provided on the support.
As a method for providing a cast coat layer, a coating liquid comprising a pigment and a binder as main components is applied on a base paper to provide a coating layer, and the coating layer is pressure-bonded to a cast drum to give a gloss finish. The glossy coating layer mainly becomes a so-called ink receiving layer for forming an inkjet image, and becomes the cast coating layer.

(Structure of cast coat coating solution)
In the present invention, the coating liquid for cast coating contains acetylene glycol or an ethylene oxide adduct of acetylene glycol. By containing this, coating defects such as a roll pattern of the recording medium and surface feeling are greatly improved. Acetylene glycol is a tertiary alcohol having an acetylene bond in the molecule, such as Surfynol 104E (manufactured by Nissin Chemical Industry Co., Ltd.) represented by the following (formula 2). The ethylene oxide adduct of acetylene glycol is represented by, for example, the following (formula 1) and includes an ethylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol. The average addition mole number of the ethylene oxide adduct of acetylene glycol used in the present invention is represented by the sum of m and n (m and n are mutually independent integers) in the following (formula 1). It is preferably 1 or less. When the average added mole number is 1 or more, the roll pattern and the surface feeling tend to deteriorate. The reason for this is not clear, but can be considered as follows.

First, the reason why the roll pattern is improved is that the acetylene glycol or the ethylene oxide adduct of acetylene glycol has a function of improving the mechanical stability of the coating liquid. Acetylene glycol or ethylene oxide adduct of acetylene glycol has an oxygen atom bonded to the adjacent carbon atom of the acetylenic triple bond in the molecule, and has a structural feature that it is nonionic but has a very strong polarity . This structural feature has the property that the dynamic surface tension is low, so that the effect of breaking the generated bubbles is high, and as a result, the mechanical stability of the coating liquid is considered to be improved. When the average number of added moles exceeds 1, the dynamic surface tension becomes high, so that the action of breaking bubbles is weakened, and the mechanical stability tends to be inferior.
The reason why the surface feeling is improved is considered that acetylene glycol or an ethylene oxide adduct of acetylene glycol forms micelles, so that peeling from a cast drum for mirror finish becomes good. When the average added mole number exceeds 1, the structure of the micelle becomes large, and therefore the peelability tends to be inferior.

The amount of acetylene glycol or ethylene oxide adduct of acetylene glycol is preferably 1 part by mass or less per 100 parts by mass of the pigment. When the ethylene oxide adduct of acetylene glycol exceeds 1 part by mass, the peelability with respect to the cast drum is deteriorated, resulting in a problem that the surface feeling is deteriorated.
Although the water-soluble binder can be used for the binder of the cast coat layer of the present invention, it is preferable to use polyvinyl alcohol which is advantageous for the crosslinking reaction of the coagulation method described later. Polyvinyl alcohol preferably has a saponification degree of 90% or less and a polymerization degree of 2000 or more. When the saponification degree is 90% or more, since the coating film is brittle, when the cast coat coating solution is applied and dried, minute cracks are likely to occur on the surface of the coating layer. Cracks are not preferable because they cause a decrease in print quality and a decrease in surface strength. Further, the lower the degree of saponification of polyvinyl alcohol, the more the ink absorbability tends to be improved. This is presumably because the lower the degree of saponification, the higher the hydrophilicity of polyvinyl alcohol and the better the ink absorbability. Moreover, it exists in the tendency for color development to improve, so that the saponification degree of polyvinyl alcohol is low. The reason for this is considered to be that the lower the degree of saponification, the higher the transparency, so that the transparency of the coating layer is increased and the printing density is improved.
When the degree of polymerization of polyvinyl alcohol increases, the coating liquid tends to foam, and the mechanical stability of the coating liquid tends to be inferior. However, the above-mentioned acetylene glycol or ethylene oxide adduct of acetylene glycol is added to the coating liquid. Can be improved.

In the present invention, the following pigments can be used alone or in combination in the cast coat layer. Specifically, silicas such as silica, colloidal silica, and vapor phase method silica, coating pigments such as kaolin, talc, calcium carbonate, titanium dioxide, clay, and zinc oxide. Among the above pigments, it is preferable to contain silicas such as silica, colloidal silica, and vapor phase method silica from the viewpoint of ink absorption. Moreover, in order to improve glossiness, it is preferable to contain the fine pigment whose average primary particle diameter is 100 nm or less.

In the coagulation method, a nonionic or anionic polymer compound capable of forming a film can be used in combination with the polyvinyl alcohol as a binder for a cast coat layer as long as the color developability, ink absorbability, and glossiness are not impaired. . Examples of such binders include starches such as starch, oxidized starch, and esterified starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; polyvinyl alcohol; polyvinyl pyrrolidone; casein; gelatin; soy protein; Derivatives thereof; styrene-butadiene resin, acrylic resin, vinyl acetate resin, vinyl chloride resin, urethane resin, urea resin, alkyd resin, and derivatives thereof can be used. In the cast coat layer, the total blending amount of polyvinyl alcohol and other binders is preferably 5 to 30 parts by mass with respect to 100 parts by mass of the pigment, but is particularly limited as long as the required coating layer strength is obtained. Is not to be done. When the blending amount of the binder increases, the ink absorbability tends to decrease.
In the rewet method, the above binder is not restricted. Therefore, polyvinyl alcohol and other binders can be used alone or in combination as long as the amount is within the above range.
In addition to the above, the cast coat layer includes, for example, a thickener, an antifoaming agent, an antifoaming agent, a pigment dispersant, a release agent, a foaming agent, a pH adjusting agent, a surface sizing agent, a coloring dye, a coloring pigment, Fluorescent dyes, ultraviolet absorbers, antioxidants, light stabilizers, preservatives, water resistance agents, surfactants, wet paper strength enhancers, water retention agents, etc. are added as appropriate within the range that does not impair the effects of the present invention. can do.

(Formation of cast coat layer)
The cast coating method includes (1) a wet casting method (direct method) in which a coating layer is pressure-bonded to a mirror-finished heating drum while the coating layer is wet, and (2) a wet coating method. Re-wetting method in which the work layer is once dried or semi-dried and then swelled and plasticized with a rewetting liquid, and the coating layer is pressure-bonded to a mirror-finished heating drum and dried. (3) The wet coating layer is solidified with a coagulation liquid. There are three types: gelling cast method (coagulation method), in which the coating layer is pressure-bonded to a heated drum that has been processed, gelled, and mirror finished. The principle of each method is the same in that the wet coating layer is pressed against the mirror-finished surface to give gloss to the coating layer surface.
These coating methods are performed as follows, for example. First, the coating liquid to be the cast coat layer is applied to the support, and then the treatment liquid is applied. Then, the cast layer is formed by pressure-bonding the coated layer to a heated mirror-finished surface and drying, Gloss is given to the surface. The coating layer at the time of applying the treatment liquid may be in a wet state or a dry state, but in particular when it is in a wet state, it is easy to copy the mirror-finished surface, and the coating layer surface has a minute amount. Since the unevenness can be reduced, it is easy to give the obtained ink-receiving layer glossiness equivalent to that of a silver salt photograph.
As a method of applying the coating liquid for the cast coat layer on the support, there are blade coater, air knife coater, roll coater, brush coater, kiss coater, squeeze coater, curtain coater, die coater, bar coater, gravure coater, gate roll coater. In addition, a known coating machine such as a short dwell coater can be appropriately selected from on-machine or off-machine coating methods. Examples of the method for applying the treatment liquid include, but are not limited to, a roll, a spray, and a curtain method.
The coating amount of the cast coat layer can be arbitrarily adjusted within the range where the surface of the support is covered and sufficient ink absorbability is obtained, but from the viewpoint of achieving both color developability and ink absorbency, It is preferably 5 to 30 g / m ² in terms of solid content.

(Coagulation method)
Next, the case where the coagulation method is used will be described. In this method, in the cast coating method, after applying the coating layer, the undried coating layer is gelled with a coagulating liquid, and then pressed and dried on a heated mirror-finished surface. If the coating layer is in a dry state when applying the coagulation liquid, it is difficult to copy the mirror drum surface, and the resulting ink-receiving layer surface has many minute irregularities, making it difficult to obtain a glossiness similar to that of a silver salt photograph. . As the coagulation liquid, those having an action of coagulating the aqueous binder in the wet coating layer, for example, calcium such as formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid, sulfuric acid, zinc, magnesium, etc. Various salt solutions are used. In particular, when polyvinyl alcohol is used as the aqueous binder, it is preferable to use a liquid containing boric acid and borate as the coagulating liquid. By mixing and using boric acid and borate, it becomes easy to make the coating layer hardness appropriate at the time of solidification, and a good gloss can be imparted to the cast coat layer. The method for applying the coagulating liquid is not particularly limited as long as it can be applied to the coating layer, and can be appropriately selected from known methods (for example, roll method, spray method, curtain method, etc.).

Moreover, a mold release agent can be added to the coating liquid and / or the coagulating liquid as necessary. The melting point of the release agent is preferably 90 to 150 ° C, and particularly preferably 95 to 120 ° C. In the above temperature range, the melting point of the release agent is almost equal to the temperature of the mirror finish surface, so that the ability as a release agent is maximized. The release agent is not particularly limited as long as it has the above-mentioned properties, but fatty acids such as stearic acid and oleic acid or salts thereof, polyethylene wax, lecithin and the like are preferable, and polyethylene wax is more preferable. .
In addition to the release agent described above, the coagulating liquid includes a cationic polymer electrolyte, a thickener, an antifoaming agent, a foam suppressor, a pigment dispersant, a foaming agent, a pH adjusting agent, a surface sizing agent, a coloring dye, Color pigments, fluorescent dyes, ultraviolet absorbers, antioxidants, light stabilizers, preservatives, water resistance agents, dye fixing agents, surfactants, wet paper strength enhancers, water retention agents, etc. It can add suitably in the range which does not impair. The ionicity of the coagulation liquid is not particularly limited.

(Rewetting method)
In the rewetting method, the above-mentioned cast coat layer coating is dried with a dryer used for forming the undercoat layer, and then the mirror-finished surface is obtained by heating the coating layer rewet with a rewetting liquid (rewetting liquid). A cast coat layer is formed by press-bonding and drying to give gloss to the surface. The rewetting liquid is composed of an aqueous liquid mainly composed of the above releasing agent. The main effect of the rewetting liquid is to wet plasticize the upper layer portion of the dry coating layer with water occupying most of the liquid. In addition to the release agent and the cationic substance, a fluorescent dye, a dye, a colloidal pigment, a surfactant, and the like may be added to the rewetting liquid as long as the effects of the present invention are not impaired. If necessary, pigment dispersants, water retention agents, thickeners, antifoaming agents, preservatives, colorants, water resistance agents, wetting agents, ultraviolet absorbers, and the like can be added as appropriate. Note that the ionicity of the rewetting liquid is not particularly limited.

In the present invention, when the required coating amount of the cast coat layer is large, the cast coat can be formed in multiple layers. Further, a backcoat layer having ink absorbability, writing property, printer printability, and other various functions may be further provided on the support surface opposite to the surface on which the ink receiving layer is provided.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in full detail, this invention is not limited by this. Unless otherwise specified, “part” and “%” described below represent “part by mass” and “% by mass”, respectively.

<Example 1>
10 parts of talc, 1.0 part of aluminum sulfate, 0.1 part of synthetic sizing agent, and 0.02 part of yield improver were added to a pulp slurry consisting of 100 parts of hardwood bleached kraft pulp (L-BKP) with a beating degree of 285 ml. When paper was made on the support with a paper machine, starch was coated on both sides so that the solid content per side was 2.5 g / m 2 to obtain a base paper having a basis weight of 170 g / m 2. The base paper was coated with coating liquid A with a blade coater so that the coating amount was 8 g / m @ 2 on one side, and dried by blowing at 140.degree. Next, 20 g / m 2 of coating liquid B is applied onto the surface coated with coating liquid A with a roll coater, and solidified using coagulating liquid C while the coating layer is in a wet state, and then press roll The mirror surface was pressed onto a mirror-finished surface heated through a film, and an ink-jet recording medium of 198 g / m 2 was obtained.
Coating liquid A: As a pigment, 100 parts of synthetic silica (Fine seal X-37: manufactured by Tokuyama Corporation), 5 parts of latex (LX438C: manufactured by Sumitomo Chemical Co., Ltd.) and polyvinyl alcohol (PVA117: manufactured by Kuraray Co., Ltd.) ) 24 parts and 5 parts of a sizing agent (Polymaron 360: manufactured by Arakawa Chemical Co., Ltd.) were mixed to prepare an aqueous coating solution having a concentration of 20%.
Coating liquid B: As a pigment, 50 parts of colloidal silica (Quatron PL-1: manufactured by Fuso Chemical Industry Co., Ltd.) and 50 parts of gas phase method silica (Aerosil 130: manufactured by Nippon Aerosil Co., Ltd.) are blended, and the degree of saponification as a binder 10% of polyvinyl alcohol (PVA224: manufactured by Kuraray Co., Ltd.) having a polymerization degree of 2400, 88%, and 0.01 part of acetylene glycol (Surfinol 104E: manufactured by Nissin Chemical Industry Co., Ltd.) are blended to a concentration of 20% The working fluid was adjusted.
Coagulation liquid C: The compounding ratio expressed by (borax / boric acid) is 2, the concentration when borate is converted to Na ₂ B ₄ O ₇ and boric acid is converted to H ₃ BO ₃ is 6%. And 0.25% release agent (Maycatex HP50: manufactured by Meisei Chemical Co., Ltd.), 0.5% penetrant (Pionine D-3120-W: trade name manufactured by Takemoto Yushi Co., Ltd.), and pH adjuster A coagulation solution was prepared by blending 0.25% citric acid.

<Example 2>
An ink jet recording medium was prepared in the same manner as in Example 1 except that the blending number of acetylene glycol contained in the coating liquid B was 0.2 parts.

<Example 3>
An ink jet recording medium was prepared in the same manner as in Example 1 except that the blending number of acetylene glycol contained in the coating liquid B was 0.5 part.

<Example 4>
In place of acetylene glycol contained in coating liquid B, 0.2 part of ethylene oxide adduct of acetylene glycol having an average addition mole number of ethylene oxide (Surfinol 420: manufactured by Nissin Chemical Industry Co., Ltd.) An ink jet recording medium was prepared in the same manner as in Example 1 except that.

<Example 5>
Except for using polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 3500 (PVA235: manufactured by Kuraray Co., Ltd.) instead of polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 2400 contained in the coating liquid B in Example 2. An ink jet recording medium was prepared in the same manner as in Example 2.

<Example 6>
Implemented except that polyvinyl alcohol having a saponification degree of 80% and a polymerization degree of 2000 (PVA420: manufactured by Kuraray Co., Ltd.) was used instead of polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 2400 contained in the coating liquid B in Example 2. An ink jet recording medium was prepared in the same manner as in Example 2.

<Example 7>
Instead of the acetylene glycol contained in the coating liquid B, an ethylene oxide adduct of acetylene glycol having an average addition mole number of ethylene oxide of 3.5 (Surfinol 440: manufactured by Nissin Chemical Industry Co., Ltd.) is 0.2. An ink jet recording medium was prepared in the same manner as in Example 1 except that the components were mixed.

<Comparative Example 1>
An inkjet recording medium was prepared in the same manner as in Example 5 except that the acetylene glycol contained in the coating liquid B was not included.

<Comparative example 2>
Inkjet recording medium as in Example 1 except that 0.2 parts of organopolysiloxane-based white mineral oil (Surfinol DF58: manufactured by Nissin Chemical Industry Co., Ltd.) is blended in place of acetylene glycol contained in coating liquid B It was created.

<Comparative Example 3>
An ink jet recording medium was prepared in the same manner as in Example 1 except that 0.2 part of polyoxyalkylene ether (Pionin K-17: manufactured by Takemoto Yushi Co., Ltd.) was blended in place of acetylene glycol contained in coating liquid B. .

<Comparative example 4>
An ink jet recording medium was prepared in the same manner as in Example 5 except that 1.2 parts of acetylene glycol contained in the coating liquid B was blended.

<Comparative Example 5>
Implemented except that polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 1700 (PVA217: manufactured by Kuraray Co., Ltd.) was used instead of the polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 2400 contained in the coating liquid B in Example 2. An ink jet recording medium was prepared in the same manner as in Example 2.

<Comparative Example 6>
Implemented except that polyvinyl alcohol having a saponification degree of 99% and a polymerization degree of 2400 (PVA124: manufactured by Kuraray Co., Ltd.) was used instead of the polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 2400 contained in the coating liquid B in Example 2. An ink jet recording medium was prepared in the same manner as in Example 2.

<Evaluation method>
The cast coating solution and recording medium of each Example and Comparative Example were used as materials and evaluated by the following methods.
1) Feeling (roll pattern)
The surface of the ink jet recording medium was visually observed, and coating unevenness on the horizontal stripes was visually evaluated. If it is more than Δ, there is no practical problem.
○: Almost no roll pattern is observed Δ: The roll pattern is slightly seen ×: The roll pattern is clearly seen

2) Peelability The surface of the mirror drum was visually observed during the production of the ink jet recording medium, and the degree of drum contamination derived from the coating layer of the recording medium was visually evaluated. If it is more than Δ, there is no practical problem.
○: Drum dirt is hardly seen. Δ: Drum dirt is slightly seen. ×: Drum dirt is often seen.

3) Experience (repellency)
The surface of the inkjet recording medium was visually observed, and gloss unevenness of about several cm was visually evaluated. If it is more than Δ, there is no practical problem.
○: Gloss unevenness of about several centimeters is hardly seen Δ: Gloss unevenness of about several centimeters is slightly seen ×: Gloss unevenness of about several centimeters is clearly seen

4) Feeling (crack)
The surface of the inkjet recording medium was observed with a digital optical microscope (Digital Microscope VH-7000, manufactured by Keyence Corporation), and the number of cracks was visually evaluated. If it is more than Δ, there is no practical problem.
○: Almost no cracks are observed Δ: Cracks are observed on a part of the recording medium surface ×: Cracks are observed on almost the entire surface of the recording medium

The obtained results are shown in Tables 1 and 2.

  As is clear from Table 1, in each of the examples, the peelability and the surface feeling (roll pattern, repellency) were all good. On the other hand, as can be seen from Comparative Example 1 in Table 2, the roll pattern and the peelability were inferior when acetylene glycol or an acetylene glycol adylene oxide adduct was not contained. In addition, as can be seen from Comparative Examples 2 and 3, the antifoaming agent composed of other substances did not show the effect of improving the roll pattern or peelability. Furthermore, from Comparative Example 4, when the number of acetylene glycol parts was large, gloss unevenness of the recording medium due to the repelling of the coating liquid occurred. In Comparative Example 5, cracks occurred because the degree of polymerization of polyvinyl alcohol was low, and in Comparative Example 6, the degree of saponification was high.

Claims (2)

A coating layer for coating a cast coat containing at least a pigment and a polyvinyl alcohol having a saponification degree of 90% or more and a polymerization degree of 2000 or more as a binder is provided on the support to provide a coating layer, and the coating layer An ink jet recording medium comprising a cast coating layer formed by pressure-drying the coating layer on a heated mirror surface while the surface of the coating layer is wet, wherein the coating liquid for cast coating contains an acetylene glycol compound. And an acetylene glycol compound is contained in the cast coat coating liquid in an amount of 1 part by mass or less based on 100 parts by mass of the pigment. The acetylene glycol compound is an ethylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol represented by the formula 1, and is represented by the sum of m and n in the following formula 1. The inkjet recording medium according to claim 1, wherein the average added mole number of ethylene oxide is 0 or 1.

(In the formula 1, m and n are integers independent of each other.)