JP2007098705A - Inkjet recording sheet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording sheet which has a uniform and smooth ink absorbing layer hardly causing film cracking and which is superior in printability, and a method which enables the sheet to be manufactured with proper productivity at a high speed without causing the dimensional error and waviness of a base material. <P>SOLUTION: The inkjet recording sheet, in which the ink absorbing layer is formed on at least either of the front and back sides of the base material, is characterized as follows: the ink absorbing layer is formed by applying a coating slip by means of a curtain coater; at least a pigment and a viscosity reducing agent are mixed into the coating slip; and the pigment is at least two kinds of mixed pigments different in a mean particle diameter of 0.9-3.0 μm. The manufacturing method is used for manufacturing the inkjet recording sheet. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inkjet recording sheet and a method for producing the same. More specifically, an ink jet recording sheet having a uniform and smooth ink-receiving layer with extremely little film cracking, having no white spots, ink bleeding, or uneven printing density, and excellent printability. The present invention relates to a method capable of producing a sheet at high speed and with high productivity without causing a dimensional defect or undulation of a substrate.

  An ink jet recording apparatus is an apparatus for recording images, characters, various graphics, and the like by directly ejecting fine ink droplets onto a recording sheet according to various operating principles. Inkjet recording apparatuses have become widespread in recent years because they can perform fine recording and can perform color recording comparable to silver salt photography. As a sheet suitably used for this ink jet recording apparatus, a coating liquid containing a pigment, a binder, an ink fixing agent, and the like is applied to at least one of the front and back surfaces of a base material such as high-quality paper, synthetic paper, and synthetic resin film. A so-called coated paper type ink jet recording sheet provided with an ink receiving layer is known. In this type of inkjet recording sheet, the thickness of the ink receiving layer is uniform and smooth so that the ink is uniformly absorbed and image unevenness such as uneven print density does not occur, and there are uneven coating and coating defects. Not particularly important.

  On the other hand, a blade coating method, an air knife coating method, a curtain coating method, and the like are known as methods for applying a coating liquid to a substrate. Above all, the curtain coating method using a curtain coater is not affected by the texture of the base material (irregularities on the surface of the base material) and can obtain a coating layer with a uniform coating amount. It is frequently used for forming an ink receiving layer of a sheet. For example, for ink jet recording in which an ink receiving layer is formed by applying a coating liquid containing a nonionic surfactant, a cationic ink fixing agent, and a pigment to at least one of the front and back surfaces of a substrate with a curtain coater A sheet has been proposed (see Patent Document 1). In such an ink jet recording sheet, a surfactant is blended in the coating liquid constituting the ink receiving layer, so that a thin and uniform ink receiving layer is formed with less occurrence of film cracking.

However, when the inkjet recording sheet is produced, if the coating speed is increased in order to improve productivity, the fluidity of the coating liquid deteriorates, and film breakage occurs in the ink receiving layer. In this case, although the solid content concentration of the coating liquid can be lowered to improve the fluidity, conversely, since there is a lot of water, it takes time in the drying process, and as a result, productivity cannot be improved. Problems arise. Moreover, when the solid content concentration of the coating solution is lowered, there is a problem that moisture absorption to the base material increases, resulting in dimensional defects and waviness.
JP 2002-274209 A

  The present invention has been made in view of the above-described background art, and has an ink receiving layer having a uniform and smooth film with little film cracking, and an ink jet recording sheet excellent in printability, and such a sheet having a poor substrate size. It is an object of the present invention to provide a method that can be manufactured at high speed and with high productivity without generating undulations.

That is, the present invention
(1) An ink jet recording sheet in which an ink receiving layer is formed on at least one of the front and back surfaces of a substrate, wherein the ink receiving layer is formed by applying a coating liquid with a curtain coater. And at least a pigment and a viscosity reducing agent are blended in the coating liquid, and the pigment is at least two mixed pigments having different average particle sizes in the range of 0.9 to 3.0 μm. Inkjet recording sheet, and
(2) At least one of the front and back surfaces of the base material is coated with a coating liquid containing at least a pigment and a viscosity reducing agent with a curtain coater to form an ink receiving layer. The present invention relates to a method for producing an ink jet recording sheet, which is at least two kinds of mixed pigments having different diameters in a range of 0.9 to 3.0 μm.

  The ink jet recording sheet has a uniform and smooth ink receiving layer with extremely little film cracking, and does not cause white spots, ink bleeding, or uneven printing density, and has excellent printability. In addition, according to the above production method, an inkjet recording sheet can be produced at high speed and with high productivity without the occurrence of dimensional defects or undulations of the substrate.

  Furthermore, when the type of pigment and the type and blending amount of the thinning agent are appropriately adjusted, an ink jet recording sheet that is particularly excellent in the characteristics of the ink receiving layer and printability is generated. Thus, it is possible to manufacture at higher speed and with higher productivity without such a problem.

  The ink jet recording sheet of the present invention has a uniform and smooth ink-receiving layer with extremely little film cracking, and has excellent printability without white spots, ink bleeding, or uneven print density. In addition, according to the production method of the present invention, such a sheet can be produced at high speed and with high productivity without causing a dimensional defect or corrugation of the base material.

(First embodiment)
The ink jet recording sheet of the present invention has an ink receiving layer formed on at least one of the front and back surfaces of the substrate, and the ink receiving layer was formed by applying a coating liquid with a curtain coater. In addition, the coating liquid contains at least a pigment and a viscosity reducing agent. Moreover, the pigments in the coating liquid are at least two mixed pigments having different average particle sizes in the range of 0.9 to 3.0 μm. Thus, one of the major features of the present invention is that a coating liquid having a specific composition is used as the coating liquid for forming the ink receiving layer, and a coating liquid having this specific composition and a curtain coater are combined. Thus, the excellent effects as described above are exhibited.

  First, the coating liquid used in the present invention will be described below.

  As a pigment mix | blended with a coating liquid, what is normally mix | blended with the coating liquid which comprises the ink receiving layer of the sheet | seat for inkjet recordings is illustrated suitably, for example.

  Examples of the pigment include clay, 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, silica. Calcium oxide, magnesium silicate, synthetic amorphous silica, colloidal silica, colloidal alumina, pseudoboehmite, aluminum hydroxide, alumina, lithopone, zeolite, hydrous halloysite, magnesium carbonate, magnesium hydroxide, porous synthetic amorphous silica, Examples include inorganic pigments such as porous magnesium carbonate and porous alumina; organic pigments such as styrene plastic pigments, acrylic plastic pigments, polyethylene, microcapsules, urea resins, and melamine resins. Can be used, or two or more thereof Germany. Among these, clay and calcium carbonate are preferably used because fine irregularities on the substrate can be sufficiently covered when the coating liquid is applied, and the handleability is excellent.

  In the present invention, in order to further improve the smoothness and uniformity of the ink receiving layer, at least two mixed pigments having different average particle diameters in the range of 0.9 to 3.0 μm are used as the pigment.

  As the at least two kinds of mixed pigments having different average particle diameters in the range of 0.9 to 3.0 μm, for example, the first pigment having an average particle diameter of 0.9 to 1.5 μm and the average particle diameter of 1.8. A mixed pigment obtained by mixing a second pigment of ˜3.0 μm at a ratio of 1/1 to 3/1 (first pigment / second pigment (mass ratio)) is preferably used.

  When the average particle size of the first pigment is too small, the air permeability of the ink receiving layer is lowered, the ink drying property is lowered, and the ink-jet ink pigment does not stay on the surface, but between the fibers of the base material. Since impregnation impairs the color density in the ink-receiving layer and printability may be reduced, it is preferably 0.9 μm or more, preferably 1.0 μm or more. On the other hand, if the average particle size is too large, the surface gloss of the ink receiving layer may be lowered, so that it is 1.5 μm or less, preferably 1.4 μm or less.

  Even when the average particle size of the second pigment is too small, the air permeability of the ink receiving layer is lowered, the ink drying property is lowered, and the pigment of the ink jet ink does not stay on the surface, even between the fibers of the base material. Since the impregnation impairs the color density in the ink receiving layer and printability may be reduced, it is desirable that the thickness be 1.8 μm or more, preferably 1.9 μm or more. On the other hand, if the average particle size is too large, the surface gloss of the ink receiving layer may be lowered. Therefore, it is desirably 3.0 μm or less, preferably 2.9 μm or less.

  The mixing ratio of the first pigment and the second pigment is such that if the first pigment is too much, the air permeability of the ink receiving layer is lowered, the second pigment protrudes on the surface of the ink receiving layer, and the printability is lowered. Therefore, it is desirable that the first pigment / second pigment (mass ratio) is 3/1 or less, preferably 2.8 / 1 or less. On the other hand, if the amount of the second pigment is too large, the surface gloss of the ink receiving layer may be lowered. Therefore, the first pigment / second pigment (mass ratio) is 1/1 or more, preferably 1.2 / It is desirable to be 1 or more.

  Although the reason is not clear by using two pigments having different particle diameters in this way, the characteristics of each pigment are exhibited as a synergistic effect, and it becomes possible to form an ink receiving layer having an appropriate gap. In addition, the strength of the ink receiving layer, coating and workability are improved, and printability can be improved.

  The viscosity reducing agent blended in the coating liquid together with the pigment is a component for reducing the viscosity of the coating liquid and adjusting it to a viscosity suitable for coating with a curtain coater.

  Examples of the thinning agent include polyester amide, which is a polycondensate of dicarboxylic anhydride and diisopropanolamine, dialkyl ester of sulfosuccinic acid, polycondensate of alkylnaphthalene sulfonic acid and formaldehyde, and the like. Or two or more can be used simultaneously.

  Examples of the polyester amide include anhydrides of linear saturated dicarboxylic acids such as oxalic acid, malonic acid, and succinic acid, anhydrides of linear unsaturated dicarboxylic acids such as maleic acid and fumaric acid, phthalic acid, and isophthalic acid. And polycondensates of dicarboxylic anhydrides and diisopropanolamine, such as aromatic dicarboxylic acid anhydrides.

  Examples of the sulfosuccinic acid dialkyl ester include sulfosuccinic acid di-4-methylpentyl ester, sulfosuccinic acid di-3-methylhexyl ester, sulfosuccinic acid dioctyl ester, sulfosuccinic acid di-2-ethylhexyl ester, sulfosuccinic acid dinonyl ester, sulfosuccinic acid ester. Examples thereof include acid di-3,5,5-trimethylhexyl ester and sulfosuccinic acid ditrimethylheptyl ester.

  Among these thinning agents, polyester amide and sulfosuccinic acid dialkyl ester are preferred because they are excellent in the action of reducing the viscosity of the coating liquid and precisely adjusting to a desired range, and also excellent in compatibility with pigments. In particular, polyester amide is preferred.

  The blending amount of the viscosity reducing agent is to prevent the film from being cracked in the formed ink-receiving layer when the viscosity of the coating liquid is not sufficiently reduced and coating is performed at a particularly high speed with a curtain coater. Is preferably 0.01 parts by mass or more, preferably 0.02 parts by mass or more, particularly preferably 0.03 parts by mass or more with respect to 100 parts by mass of the mixed pigment. In addition, when the blending amount of the thickening agent is too large, the viscosity of the resulting coating liquid is excessively reduced, and the adhesive force of the ink receiving layer to the substrate is lowered, so that the ink receiving layer is sufficiently formed on the substrate. The ink is not sufficiently absorbed by the ink receiving layer during printing, and white spots may occur on the printed surface. Therefore, the amount is 4 parts by mass or less, preferably 2 parts per 100 parts by mass of the mixed pigment. It is desirable that the amount is not more than part by mass, particularly preferably not more than 0.08 part by mass.

  The coating liquid used in the present invention contains at least the pigment and the viscosity reducing agent. In addition to these, an additive usually used for forming the ink receiving layer of the ink jet recording sheet is necessary. Can be selected and blended as appropriate.

  Examples of other additives blended in the coating liquid include a binder, a surfactant, and an ink fixing agent.

  The binder has a function of fixing the solvent of the ink. For example, in view of the affinity with the solvent of the water-soluble ink, the water-soluble binder is particularly preferably used. Examples of the water-soluble binder include polyvinyl alcohol (hereinafter referred to as “PVA”), vinyl acetate, ethylene-vinyl acetate copolymer (hereinafter referred to as “EVA”), polyvinyl pyrrolidone, oxidized starch, esterified starch, and etherification. Examples thereof include cellulose derivatives such as starch, carboxymethylcellulose, and hydroxyethylcellulose, casein, gelatin, and soybean protein, and these can be used alone or in combination of two or more.

  The blending amount of the binder is 1 part by mass or more, and further 2 parts by mass with respect to 100 parts by mass of the mixed pigment so that the fixing effect of the solvent of the ink due to the blending of the binder is sufficiently expressed. The above is preferable. In consideration of the blending ratio with other components such as a thinning agent, surfactant, and ink fixing agent, the blending amount of the binder is 40 parts by mass or less, further 38 parts by mass or less with respect to 100 parts by mass of the mixed pigment. It is preferable that

  The surfactant has an action of adjusting the surface tension of the coating liquid. For example, among various nonionic surfactants, cationic surfactants, amphoteric surfactants, etc., a viscosity reducer or an ink described later. It can be appropriately selected and used depending on the type of fixing agent or the like.

  Nonionic surfactants include, for example, lauryl alcohol surfactants such as ET102 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), ET170 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), ET115 (commercial product). Name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), synthetic alcohol surfactants such as NL-30 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), preferably HLB is about 8-16, Polyoxyethylene alkyl ether type nonionic surfactant of about 9 to 14; perfluorooctane sulfonic acid diethanolamide type surfactant such as EFTOP EF-122A (trade name, manufactured by Tochem Products Co., Ltd.), EFTOP EF- N-propyl-N- (2-hydroxyethyl) perfluorooctane sulfone such as 121 (trade name, manufactured by Tochem Products Co., Ltd.) Fluorine nonionic surfactants such as amide surfactants can be mentioned, and these can be used alone or in combination of two or more.

Examples of the cationic surfactant include a formula:
RSO ₂ N (H) C ₃ H ₆ N ⁺ (CH ₃ ) ₃ I ⁻
(Wherein R represents a perfluoroalkyl group having 6 to 10 carbon atoms) EFTOP EF-132 (trade name, manufactured by Tochem Products), formula:
RSO ₂ N (H) C ₃ H ₆ N ⁺ (CH ₃ ) ₂ C ₂ H ₄ COO ⁻
(Wherein, R represents a perfluoroalkyl group having 6 to 10 carbon atoms) fluorinated cationic surfactants such as EFTOP EF-700 (trade name, manufactured by Tochem Products Co., Ltd.) These may be used alone or in combination of two or more.

  Examples of amphoteric surfactants include lauryldimethylaminoacetic acid betaine amphoteric compounds such as Levon LD-36 (trade name, manufactured by Sanyo Chemical Industries, Ltd.) and Levon 101-H (trade name, manufactured by Sanyo Chemical Industries, Ltd.). Examples include surfactants, amidoamine type amphoteric surfactants, sulfobetaine type amphoteric surfactants, and alkylimidazoline type amphoteric surfactants such as imidazolinium betaine. These may be used alone or in combination of two or more. it can.

  The blending amount of the surfactant is 0.1 to 100 parts by mass of the mixed pigment so that the effect of adjusting the surface tension of the coating liquid by blending the surfactant is sufficiently expressed. It is preferable that it is at least part by mass, more preferably at least 0.2 part by mass. Moreover, when there is too much compounding quantity of this surfactant, since there exists a possibility that a coating liquid may foam, it is 20 mass parts or less with respect to 100 mass parts of mixed pigments, Furthermore, it is 18 mass parts or less. Is preferred.

  The ink fixing agent has a function of promoting the fixing property of the ink. For example, a monomer, oligomer or polymer of a primary to tertiary amine or a quaternary ammonium salt which dissociates and exhibits a cationic property when dissolved in water. And the like, and these can be used alone or in combination of two or more. Among these, the above oligomers and polymers are particularly preferable from the viewpoint of excellent fixing effect of ink.

  The blending amount of the ink fixing agent is 1 part by mass or more with respect to 100 parts by mass of the mixed pigment, in order that the effect of promoting the fixability of the ink by blending the ink fixing agent is sufficiently expressed. Is preferably 2 parts by mass or more. In consideration of the blending ratio with other components such as a thinning agent and a surfactant, the blending amount of the ink fixing agent is 30 parts by mass or less and further 28 parts by mass or less with respect to 100 parts by mass of the mixed pigment. It is preferable.

  In the present invention, among the pigments and the viscosity reducing agent, and other additives such as a binder, a surfactant, and an ink fixing agent as necessary, the types of the respective components are appropriately changed and combined, and the blending ratio is set. After the adjustment, these components can be mixed uniformly to prepare a coating solution.

The viscosity of the coating liquid is measured with a B-type viscometer so that a desired coating amount can be obtained at the time of forming the ink-receiving layer, and in order to eliminate the possibility of taking a long time for drying. It is preferably 30 × 10 ⁻³ Pa · s or more, more preferably 40 × 10 ⁻³ Pa · s or more. Further, in order to form an ink receiving layer on a substrate with a curtain coater easily and at high speed without unevenness, and to eliminate the possibility of white spots occurring during printing, the viscosity is 700 × 10 ⁻³ Pa · s at 25 ° C. Hereinafter, it is further preferably 600 × 10 ⁻³ Pa · s or less.

  The solid content concentration of the coating solution is 30% or more, or 32% or more, in order to eliminate the possibility of taking a long time for drying or increasing the amount of moisture absorbed into the base material and causing dimensional defects and undulations. It is preferable that Further, in order to eliminate the possibility that the fluidity of the coating solution deteriorates when the coating speed is increased and film breakage occurs in the ink receiving layer, the solid content concentration is 50% or less, and further 48% or less. Preferably there is.

The surface tension of the coating liquid is such that, for example, the binder in the ink receiving layer penetrates into the substrate more than necessary, and ink absorption in the ink receiving layer proceeds excessively during printing, or conversely to the substrate. In order to eliminate the possibility of printing density unevenness due to inhibition of ink absorption, 20 × 10 ⁻ at 25 ° C. measured by Kyowa Interface Science Co., Ltd., JET-2 type or FIBRO, FIBRO DAT1100. It is preferably ³ N / m or more, more preferably 25 × 10 ⁻³ N / m or more. Further, when the ink receiving layer is formed on the substrate with a curtain coater, the surface tension is 60 ° C. at 25 ° C. in order to eliminate the possibility that the coating liquid does not wet and the formation of the ink receiving layer becomes difficult. It is preferably × 10 ⁻³ N / m or less, more preferably 55 × 10 ⁻³ N / m or less.

  In the present invention, for example, when the type of pigment, the type and blending amount of the thinning agent, and the viscosity, solid content concentration and surface tension of the coating liquid are adjusted within the above ranges, film cracking occurs. An ink-receptive layer is formed that is extremely small and smooth, and does not cause white spots, ink bleeding, or uneven printing density. Thus, it is possible to manufacture at higher speed and with higher productivity without such a problem.

  Next, the base material on which the ink receiving layer is formed will be described below.

  As the base material used in the present invention, coating with a curtain coater is possible. For example, paper, thermoplastic resin film, synthetic paper, synthetic resin laminated paper such as photographic base material, wood fiber and synthetic fiber are mainly used. Various sheet materials such as non-woven fabrics can be suitably used.

  For example, in the case of paper, there are no particular limitations on the raw material pulp, other additive components, and the papermaking method, and those used for ordinary recording paper can be appropriately selected and employed.

  Examples of raw material pulp include waste paper pulp, chemical pulp such as hardwood bleached kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP), non-wood fibers such as kenaf and bagasse, and raw pulp such as synthetic fibers. Can be used alone or in admixture of two or more. Among these, waste paper pulp is preferably used as a raw material pulp from the viewpoint that an inkjet recording sheet can be produced at low cost and can contribute to environmental protection. Waste paper pulp is higher in opacity than other pulps of the same weight, and if it is used as a base material, a paper for inkjet recording with high opacity can be obtained.

  Among the used paper pulp, for example, used paper pulp containing 30% by mass or more, more preferably 80% by mass or more of magazine used paper pulp derived from magazine used paper is preferable, and used paper pulp made only of magazine used paper pulp is particularly preferable. In the case of using a magazine waste paper pulp derived from magazine waste paper, one having a Hunter whiteness of 80% or more is desirable from the viewpoint of good recording in ink jet recording.

  The decrease in paper strength of paper containing waste paper pulp as a raw material can be prevented by classifying the waste paper pulp to remove short fibers and using waste paper pulp consisting only of long fibers. The average fiber length of the short fibers to be removed can be changed as appropriate in consideration of the paper making method and the characteristics of the product after paper making. For example, classification can be performed so that the freeness (CSF) is 300 mL or more. preferable. Further, the difference between the average fiber length for the remaining long fibers and the average fiber length for the short fibers to be removed is preferably at least 10%. The classification of used paper pulp may be performed using a normal classifier, a classification technique, etc., for example, it can be classified by hydraulic classification with a classifier such as Johnson Frankionator, Atomizing Hall, X-cron, Classification can also be performed by mechanical sieving such as a multifractor, a CH-F screen, and a fiber crafter. Among these classifiers, a multifractor (manufactured by Voith Paper) or a CH-F screen (manufactured by Aikawa Tekko Co., Ltd.) is preferably used.

  Further, the waste paper pulp is preferably bleached with, for example, thiourea dioxide based on a conventional bleaching method. By bleaching waste paper pulp with thiourea dioxide, the fixability of the ink-jet ink is further improved and the ink bleeding is further prevented.

  In addition, the base material used in the present invention usually includes an internal sizing agent, a neutral sizing agent, a polymer sizing agent, an acidic sizing agent, a sizing agent, a filler, a size press, and the like that are contained in the base material of the inkjet recording sheet. A white pigment or the like may be contained. Examples of the white pigment include light calcium carbonate, heavy calcium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, Inorganic pigments such as calcium silicate, magnesium silicate, synthetic silica, aluminum hydroxide, alumina, lithopone, zeolite, magnesium carbonate, magnesium hydroxide; styrene plastic pigment, acrylic plastic pigment, polyethylene, microcapsule, urea resin, Examples thereof include organic pigments such as melamine resins, and these can be used alone or in combination of two or more.

  In addition to the above, as other additives, for example, flocculants, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, foam suppressors, mold release agents, foaming agents, penetrants, coloring dyes, coloring Pigments, fluorescent brighteners, UV absorbers, antioxidants, antiseptics, antibacterial agents, water resistance agents, wet paper strength enhancers, dry paper strength enhancers, inkjet dye fixing agents, etc., as appropriate It can also be contained in the substrate.

Although there is no limitation in the basic weight of a base material, Usually, it is preferable that it is about 60-120 g / m < ² >.

  The ink jet recording sheet of the present invention is obtained by applying an application liquid on at least one of the front and back surfaces of the base material with a curtain coater to form an ink receiving layer.

  The curtain coater used in the present invention is not particularly limited, and those usually used for forming an ink receiving layer of an ink jet recording sheet can be suitably used. There are no particular limitations on the operating conditions of the curtain coater. For example, if the conditions such as the discharge amount, coating speed, and coater width are appropriately adjusted according to the properties of the target inkjet recording sheet such as the coating amount, etc. Good. The normal discharge amount is preferably about 5 to 15 L / min, and the coater width is preferably about 800 to 1500 mm. The coating speed is usually about 180 to 200 m / min. However, in the present invention, since a coating fluid having a specific fluidity as described above is used, the productivity is high, for example, about 300 to 350 m / min. It can be applied well and no film cracking occurs in the ink receiving layer.

  Next, based on the drawings showing an example of the curtain coater, a method for producing the ink jet recording sheet of the present invention will be described.

  FIG. 1 is a schematic view showing an example of a curtain coater used in the present invention. In FIG. 1, 1 is a curtain coater, 2 is a coater head, 3 is a coater lip, 4 is an edge guide, 5 is a liquid receiving tank, 6 is a wind shield, and 7 is a roll.

  In the curtain coater 1, the coating liquid i prepared in advance is sent from the coating liquid storage tank to the coater head 2 by a feed pump or the like. The interior of the coater head 2 is composed of a manifold 2a and a slit 2b, each of which is finished with high precision. The supplied coating liquid i is filled in the manifold 2a, and in the narrow gap that passes when it is sent to the slit 2b, the influence of the dynamic pressure due to the liquid feed pump feeding is reduced, and the pressure distribution in the width direction Is made uniform and flows out of the coater lip 3 to form the vertical curtain film M.

  The vertical curtain film M having a uniform profile in the width direction comes into contact with the continuously running substrate S and is applied to the substrate S. Here, the edge guides 4 and 4 are provided so as not to exceed the width of the coater head 2 and further to exceed the width of the substrate S, and the vertical curtain film M is formed to exceed the width of the substrate S. The reason why the vertical curtain film M is formed beyond the width of the substrate S is to prevent thick coating of the coating layer at both ends of the vertical curtain film M. The coating liquid i flowing down beyond the width of the substrate S is collected in the liquid receiving tank 5, returned to the coating liquid storage tank, and then coated again. Even when the substrate S is cut and the coating is interrupted, the coating liquid i is collected in the liquid receiving tank 5.

  At the contact portion (hereinafter referred to as “coating portion”) between the base material S and the vertical curtain film M that is continuously running, the air flow accompanying the base material S is shielded, and the vertical curtain is circulated by surrounding air circulation. A wind shield 6 is provided so that the film M reaches the substrate S without being disturbed. Moreover, the conveyance direction of the base material S is comprised so that the influence on the coating part of the air which accompanies the base material S may be minimized by changing direction with the roll 7 just before a coating part.

  In order to apply the formed vertical curtain film M in a stable state, a certain amount of height from the base material S to the outflow portion below the coater head 2 is required. The height is usually about 60 to 300 mm, preferably about 100 to 250 mm.

  Thus, a coating liquid is applied to the substrate by a curtain coater to form an ink receiving layer to obtain an ink jet recording sheet. The ink receiving layer is formed on either the front surface or the back surface of the substrate. Alternatively, it may be formed on the front and back surfaces. In consideration of convenience during use of the resulting inkjet recording sheet, the ink receiving layer is preferably formed on the front and back surfaces of the substrate.

  There is no particular limitation on the drying temperature and drying time when the coating liquid is applied. For example, the coating liquid temperature is about 30 to 50 ° C. and the drying temperature is 110 so that the ink receiving layer is sufficiently formed. What is necessary is just to make about -150 degreeC and drying time about 3 to 8 minutes. In addition, when a relatively high solid concentration of, for example, about 30 to 50% is used as the coating liquid, the drying time can be further shortened, but the organic polymer constituent material of the coating liquid is deformed or altered. It is best to dry it mildly so as not to come.

Further, the coating amount of the coating liquid is not particularly limited, but in order to give sufficient surface strength to the ink jet recording sheet, it is adjusted to be 1 g / m ² or more, further 2 g / m ² or more. In order to prevent the viscosity of the surface from becoming too high, it is preferably adjusted to 20 g / m ² or less, more preferably 18 g / m ² or less.

  The thickness of the ink receiving layer thus formed is usually determined from the relationship with the amount of ink absorbed, but considering that the solvent in the ink is temporarily held by the ink receiving layer, the dry film thickness is 20 It is preferably about ˜60 μm.

  When the inkjet recording sheet of the present invention is mounted on a recording apparatus for printing, there is no particular limitation on the ink to be used. For example, an anionic water-based ink is preferably used.

  Examples of the anionic water-based ink include a recording ink in which a colorant, a solvent, other additives, and the like are appropriately selected and mixed in a desired amount.

  Examples of the colorant include water-soluble dyes such as direct dyes, acid dyes, basic dyes, reactive dyes, and food colorings.

  Examples of the solvent include water and water-soluble organic solvents that are usually used in water-based inks. Examples of the water-soluble organic solvent include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, and isobutyl. C1-C4 alkyl alcohols such as alcohol, sec-butyl alcohol and tert-butyl alcohol; Amides such as dimethylformamide and dimethylacetamide; Ketones or ketone alcohols such as acetone and diacetone alcohol; Tetrahydrofuran and dioxane Ethers of polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, Alkylene glycols having 2 to 6 alkylene groups such as reethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol; glycerin, ethylene glycol methyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, triethylene And lower alkyl ethers of polyhydric alcohols such as glycol monomethyl ether and triethylene glycol monoethyl ether.

  The other additives are not particularly limited, and examples thereof include a pH adjuster, a metal sequestering agent, a fungicide, a viscosity modifier, a wetting agent, a surfactant, and a rust inhibitor.

  The ink jet recording sheet of the present invention is of course suitable for use in an ink jet recording apparatus, but is not limited to use in such an ink jet recording apparatus. For example, the anionic water-based ink is used. It can be suitably used in all recording methods.

  Next, the ink jet recording sheet of the present invention and the production method thereof will be described in more detail based on the following examples, but the present invention is not limited to such examples.

(Preparation Examples 1-12 and Comparative Preparation Examples 1-3)
In the composition shown in Table 1, a viscosity reducing agent, a binder, a surfactant, and an ink fixing agent were blended into the dispersion of the mixed pigment, and mixed to obtain a uniform composition to obtain a coating solution. Each component shown in Table 1 is as follows.

(1) Mixed pigment first pigment clay (trade name: HF90, manufactured by Huba, average particle size: 1.1 μm)
Second pigment Light calcium carbonate (trade name: TP-CPC, manufactured by Okutama Kogyo Co., Ltd., average particle size: 2.6 μm)

(2) Thickener PEA Polyester amine which is a polycondensation product of succinic anhydride and diisopropanolamine (trade name: TopBlane S1, manufactured by DSM)
PSS sulfosuccinic acid di-4-methylpentyl ester

(3) Binder PVA (trade name: PVA205, manufactured by Kuraray Co., Ltd., degree of saponification: 89 mol%)
EVA (Aqueous polymer dispersant of ethylene vinyl acetate)

(4) Surfactant SA1 Polyoxyethylene alkyl ether-based nonionic surfactant (trade name: ET102, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., HLB: 10.8)
SA2 Polyoxyethylene alkyl ether nonionic surfactant (trade name: ET115, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., HLB: 12.1)

(5) Ink fixing agent OG1 Quaternary ammonium salt oligomer (polydimethyldiallylammonium chloride)
OG2 Secondary amine oligomer (dimethylamine)

  Table 2 shows the viscosity (measured with a B-type viscometer), solid content concentration and surface tension (measured with Kyowa Interface Science Co., Ltd., JET-2 type) for the obtained coating liquid (25 ° C.). Show.

(Examples 1-12 and Comparative Examples 1-3)
Using the coating liquids obtained in Preparation Examples 1 to 12 and Comparative Preparation Examples 1 to 3, respectively, inkjet recording sheets were produced in the following steps.

First, the base material was manufactured as follows. Multifractor (manufactured by Voith Paper Co., Ltd.) so that waste paper pulp slurry (hunter whiteness: 80% or more) made of magazine waste paper pulp is bleached with thiourea dioxide and freeness (CSF) is 300 mL or more Classification processing was carried out. To 100 parts by mass of this classified pulp slurry, 3 parts by mass of aluminum sulfate (flocculant), 10 parts by mass of internal sizing agent, and 10 parts by mass of talc (white pigment) are added, and paper is made with a long net type paper machine. Paper (basis weight: about 64 g / m ² ) was produced.

Next, using the curtain coater shown in the schematic diagram of FIG. 1, the height of the vertical curtain film M is set to about 100 mm, the discharge rate is 10 L / min, the coating speed is 300 m / min, and the coater width is 1000 mm. A coating solution was applied to the front and back surfaces of the printing paper, and dried at 110 ° C. for 5 minutes to form an ink receiving layer, thereby producing an ink jet recording sheet. The total operation time of the curtain coater was 8 hours, and the coating amount of the coating liquid was 10 g / m ² for all.

  The obtained ink jet recording sheet was subjected to the following test, and its characteristics were examined. These results are shown in Table 3 together with the dry film thickness of the ink-receiving layer (average value of 5 locations (4 corners and center) when A4 size is used).

(Test Example 1) Film cracking of ink receiving layer In the operation time of the curtain coater at the time of coating, the formed ink receiving layer was visually observed to count the number of film cracking, and based on the following evaluation criteria And evaluated.
[Evaluation criteria]
A: There is no film cracking.
B: Film breakage is 1 to 2 times.
C: Film cracking is 3 to 4 times.
D: The film is broken 5-6 times.
E: Film cracking is 7 times or more.

Test Example 2 Uniformity and Smoothness of Ink Receiving Layer For the A4 size ink jet recording sheet, the dry film thickness at five locations (four corners and the center) of the formed ink receiving layer was measured, and the maximum value The difference from the minimum value was obtained and evaluated based on the following evaluation criteria.
[Evaluation criteria]
A: The difference is less than 1 μm.
B: The difference is 1 μm or more and less than 3 μm.
C: The difference is 3 μm or more and less than 5 μm.
D: The difference is 5 μm or more and less than 10 μm.
E: The difference is 10 μm or more.

(Test Example 3) Substrate Dimension Failure About the A4 size inkjet recording sheet, whether or not a dimensional defect (paper elongation) occurred was measured and evaluated based on the following evaluation criteria.
[Evaluation criteria]
A: The maximum elongation is less than 1 mm.
B: The maximum elongation is 1 mm or more and less than 3 mm.
C: The maximum elongation is 3 mm or more and less than 5 mm.
D: The maximum elongation is 5 mm or more and less than 7 mm.
E: The maximum elongation is 7 mm or more.

(Test Example 4) Corrugation of Substrate The A4 size ink jet recording sheet was visually observed whether or not the corrugation (cockling) occurred, and evaluated based on the following evaluation criteria.
[Evaluation criteria]
A: There is no wave.
B: Waves are 1 to 2 places.
C: There are 3 to 4 undulations.
D: There are 5 to 6 undulations.
E: There are 7 or more undulations.

(Test Example 5) White spots on printed surface An anionic water-based ink (color: black, manufactured by Canon Inc., ink tack value by RI tester: 26) was prepared, and this ink and an A4 size inkjet recording sheet were prepared. The ink jet printer (model number: PIXUS860i, manufactured by Canon Inc.) was attached. Using this ink jet printer, printing was performed at a temperature of 23 ° C. and a relative humidity of 50% with an ink amount of 0.5 ml and a resolution of 2880 dpi. After printing twice (two rotations), the printing surface of the inkjet recording sheet was visually observed to count the white spots and evaluated based on the following evaluation criteria.
[Evaluation criteria]
A: There are no white spots.
B: There are 1 to 2 white spots.
C: There are 3 to 5 white spots.
D: There are 6 to 9 white spots.
E: There are 10 or more white spots.

Test Example 6 Printing Surface Density Unevenness In the same manner as in Test Example 5, printing was performed with an ink amount of 0.5 ml and a resolution of 2880 dpi. After printing twice (twice rotations), the printed surface of the inkjet recording sheet was visually observed to count the density unevenness points, and evaluated based on the following evaluation criteria.
[Evaluation criteria]
A: There is no density unevenness.
B: Density unevenness is 1 to 2 places.
C: The density unevenness is 3 to 5 places.
D: Density unevenness is 6 to 9 places.
E: The density unevenness is 10 or more.

(Test Example 7) Bleeding of printing surface (1) Inkjet printer 1
Anionic water-based ink (color: cyan, magenta and yellow, manufactured by Canon Inc.) was prepared, and this ink and an A4 size inkjet recording sheet were mounted on an inkjet printer (model number: PIXUS860i, manufactured by Canon Inc.). . Using this ink jet printer, red, green, and purple colors composed of overlapping colors of cyan, magenta, and yellow inks at a temperature of 23 ° C. and a relative humidity of 50% with an ink amount of 0.5 ml and a resolution of 2880 dpi Each was printed five times (size: 3 cm × 3 cm). After 30 minutes from the start of printing, the presence or absence of bleeding on the printed surface was visually observed and evaluated based on the following evaluation criteria.
[Evaluation criteria]
A: There is no bleeding.
B: Bleeding is 1 to 2 places.
C: There are 3 to 5 spots.
D: There are 6 to 9 spots.
E: There are 10 or more spots.

(2) Inkjet printer 2
Anionic water-based ink (color: cyan, magenta and yellow, manufactured by Seiko Epson Corporation) was used as the ink, and an ink jet printer (model number: PM-G800, manufactured by Seiko Epson Corporation) was used as the printer, In the same manner as the inkjet printer 1, the presence or absence of bleeding on the printing surface was visually observed and evaluated based on the same evaluation criteria as the inkjet printer 1.

  From the results shown in Table 3, the ink jet recording sheets obtained in Examples 1 to 12 were all coated with a high speed of 300 m / min. In addition, an ink receiving layer excellent in smoothness is formed, and the substrate has little or no dimensional defects and undulations. In addition, when printing is performed with an ink jet printer using these ink jet recording sheets, white spots, density unevenness, and bleeding do not occur at all on the printing surface, and any of the ink jet recording sheets of Examples 1 to 12 can be obtained. It can also be seen that the printability is excellent.

  On the other hand, the ink jet recording sheet of Comparative Example 1 using a coating liquid that does not contain a thinning agent is in a poor state in any of the ink receiving layer, the base material, and the printing surface, and is used for an ink jet recording apparatus. Is difficult. In addition, in the case of the ink jet recording sheets of Comparative Examples 2 and 3 in which only one kind of pigment is used, an ink receiving layer having an appropriate gap is not formed, and the state of the printing surface may be deteriorated particularly in terms of bleeding. Recognize.

  The ink jet recording sheet of the present invention can be suitably used in various ink jet recording apparatuses, and fine recording is possible based on the excellent characteristics of the ink jet recording sheet.

It is the schematic which shows an example of the curtain coater used for the sheet | seat for inkjet recording of this invention, and its manufacturing method.

Explanation of symbols

1 Curtain coater 2 Coater head 3 Coater lip 4 Edge guide 5 Receiving tank 6 Wind shield 7 Roll

Claims (3)

An ink jet recording sheet having an ink receiving layer formed on at least one of the front and back surfaces of a substrate,
The ink receiving layer is formed by coating a coating liquid with a curtain coater, and at least a pigment and a viscosity reducing agent are blended in the coating liquid, and the pigment has an average particle size of 0. An ink jet recording sheet, which is at least two kinds of mixed pigments different in a range of 9 to 3.0 μm. The pigment comprises a first pigment having an average particle diameter of 0.9 to 1.5 μm and a second pigment having an average particle diameter of 1.8 to 3.0 μm of 1/1 to 3/1 (first pigment / second Pigment (mass ratio)) mixed pigment,
The blending amount of the thinning agent is 0.01 to 4 parts by mass with respect to 100 parts by mass of the mixed pigment,
The ink jet recording sheet according to claim 1, wherein the thinning agent is polyester amide. At least one side of the front and back surfaces of the base material is coated with a coating liquid containing at least a pigment and a viscosity reducing agent with a curtain coater to form an ink receiving layer,
A method for producing an ink jet recording sheet, wherein the pigment is at least two mixed pigments having an average particle diameter of 0.9 to 3.0 μm.

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