JP2005225046A - Inkjet recording sheet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording sheet, wherein particularly the absorbency of a water-color ink is excellent, the shape of an ink dot formed thereon is sharp, the color developing properties of ink are excellent, and a stable high-grade printing image is given, which has an ink receiving layer excellent in transparency, blocking resistance, water resistance, humidity resistance and transferability. <P>SOLUTION: The inkjet recording sheet has at least one ink receiving layer provided on at least one side of a base material sheet. The ink receiving layer is formed using the composition made of a hydrophilic polyurethane resin obtained by reacting an organic polyisocyanate, a hydrophilic polyol of a high molecular weight and/or a polyamine, a compound having at least one active hydrogen group and at least one tertially amino group in its molecule with a polysiloxane having at least one active hydrogen-containing group in its molecule, and of a fine particle silica. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet recording sheet (hereinafter simply referred to as “recording sheet”) and a method for producing the same, and more specifically, imparts excellent water resistance and moisture resistance to a printed image, and absorbs ink and develops ink. The present invention relates to a recording sheet that has an ink receiving layer that is excellent in transparency, can stably record high-quality printed images, has excellent transparency and blocking resistance, and has excellent transportability, and a method for producing the same.

  The ink jet recording method is based on various operating principles, for example, an electrostatic attraction method, a method of applying mechanical vibration or displacement to the ink using a piezoelectric element, a method of heating and foaming the ink, and utilizing the pressure. Is used to record images, characters, etc. by flying them on a recording sheet such as paper, enabling high-speed printing, generating less noise during printing, high-quality printing, and multicolor printing. As a recording method capable of printing, it is rapidly spreading in various applications.

  As a recording sheet used for such ink jet recording, the ink adhering to the recording sheet can be absorbed quickly so that the ink does not bleed or flow and impair the print quality. In order to form dots, a recording sheet is proposed in which an ink receiving layer mainly composed of various pigments and resins is provided on a support such as paper, or a porous pigment is embedded in the paper itself. ing.

  For example, Patent Document 1 describes that an inorganic pigment and an organic pigment are used in combination as a pigment, and an ink-receiving layer is provided using a water-soluble polymer as a binder. And providing an ink receiving layer using a polyvinyl alcohol copolymer having a silanol group.

However, as the performance of inkjet recording devices such as high-speed recording, high-definition or full-color is improved and applications are expanded, it is required that recording sheets have the following advanced characteristics. It was.
(1) fast ink absorption and large ink absorption capacity;
(2) High color developability of the ink,
(3) the surface strength of the ink receiving layer is high;
(4) The support has water resistance, and the ink does not cause irregularities or curls on the support,
(5) The image printed on the ink receiving layer has good image storability such as water resistance and ozone resistance,
(6) The ink receiving layer does not change with time.

  Conventionally, porous pigments and water-soluble polymers having excellent ink absorbency are used as components of the ink receiving layer provided on the recording sheet to satisfy these requirements, and latex is used to improve the water resistance of the ink receiving layer. In addition, it has been proposed and studied to use synthetic paper or plastic film having water resistance as the support itself.

  However, a recording sheet having an ink receiving layer formed using paper as a support or using only a water-soluble polymer has poor water resistance of the image formed thereon, and the printed portion is blurred, resulting in a clear image. Inferior to sex. Also, a recording sheet in which a porous pigment is dispersed in an ink receiving layer generally reduces the transparency of the ink receiving layer so that the porous pigment is usually used as a matting agent (matting agent). Even if the dispersion amount of the porous pigment is as small as 5% by mass or less, the transparency is remarkably lowered. On the other hand, for those using synthetic paper or plastic film for the support or using latex for the resin of the ink receiving layer, the adhesion between the ink receiving layer and the support, the ink absorption in the ink receiving layer and the ink absorption There is a problem with drying.

JP 57-82085 A Japanese Patent Laid-Open No. 62-268682

  The present invention is particularly excellent in water-based ink absorbability, the ink dot shape is sharp, the ink coloring property is excellent, and a stable and high-quality printed image is provided. Further, transparency, blocking resistance, water resistance and An object of the present invention is to provide a recording sheet having an ink receiving layer having excellent moisture resistance and excellent transportability.

  The above object is achieved by the present invention described below. That is, according to the present invention, in a recording sheet in which at least one ink receiving layer is provided on at least one side of a base sheet, the ink receiving layer is composed of an organic polyisocyanate, a high molecular weight hydrophilic polyol and / or a polyamine (hereinafter referred to as “polyamine”). A compound having at least one active hydrogen-containing group and at least one tertiary amino group in the same molecule, and at least one active hydrogen-containing group in the molecule. Provided is a recording sheet formed using a composition comprising a hydrophilic polyurethane resin obtained by reacting with polysiloxane and fine particle silica (hereinafter referred to as “the composition of the present invention”). .

  Further, the present invention provides a method for producing a recording sheet by providing at least one ink receiving layer on at least one side of a base sheet, and the ink receiving layer is coated with a paint containing the composition of the present invention. Provided is a method for producing a recording sheet, which is formed by applying and drying on at least one side.

  According to the present invention described above, by forming an ink receiving layer using the composition of the present invention, it is possible to record a high-quality printed image with excellent ink absorbability, drying property, and color developability. Furthermore, a recording sheet having an ink receiving layer excellent in transparency, blocking resistance and water resistance of a printed image is provided.

Next, the present invention will be described in more detail with reference to the best mode for carrying out the invention.
In the recording sheet of the present invention, the ink receiving layer is composed of a hydrophilic polyurethane resin and fine particle silica. The hydrophilic polyurethane resin used in the present invention comprises an organic polyisocyanate, a hydrophilic component, a compound having at least one active hydrogen-containing group and at least one tertiary amino group in the same molecule, It is a hydrophilic polyurethane resin obtained by reacting polysiloxane having at least one active hydrogen-containing group in the presence of a chain extender, if necessary.

  In the present invention, the fine particle silica is contained in the generated hydrophilic polyurethane resin by synthesizing the hydrophilic polyurethane resin by adding the fine particle silica in advance to the hydrophilic component when the hydrophilic polyurethane resin is synthesized. (Dispersed) The fine particle silica is stably dispersed in the solution of the hydrophilic polyurethane resin, although no dispersant is used. The ink receiving layer of the recording sheet of the present invention is formed using the composition of the present invention. In the present invention, the polyurethane resin is a generic term for a polyurethane resin, a polyurea resin, and a polyurethane-polyurea resin.

  In the present invention, as the mixture of the hydrophilic component and the fine particle silica, a mixture obtained by mechanically mixing and dispersing the fine particle silica in the hydrophilic component can be used, but the dispersion of the silica sol from the mixture of the hydrophilic component and the silica sol can be used. It is preferable to use one obtained by removing the medium. When the hydrophilic component is used as a solution of the soluble organic solvent, the soluble organic solvent is also removed from the mixture together with the silica sol dispersion medium. The silica sol in the present invention is a dispersion in which fine particle silica is usually stably dispersed in water and / or alcohol as a dispersion medium. As the dispersion medium, ketones, esters, and other organic solvents are also used. The average particle diameter of the fine particle silica in the silica sol is usually 1 μm or less, and particularly preferably 1 to 300 mμm (nm).

  Conventionally, when an ink receiving layer of a recording sheet is formed, a method using a resin solution or a resin dispersion is generally used. Examples of the method for dispersing the fine particle silica in the polyurethane resin solution include the following methods. For example, a method in which fine particle silica is mixed and dispersed in a polyurethane resin using an ordinary dispersion mixer and dissolved in a solvent (1), and a method in which fine particle silica or silica sol is added and dispersed in a polyurethane resin solution (2) ) Is considered.

  However, the above method (1) is economically disadvantageous because a stable fine particle silica dispersion cannot be obtained even if a dispersant is used. Further, although the above method (2) is a general method, the fine particle silica cannot be stably dispersed even if this method or a dispersant is used. Even if silica sol is used as the fine particle silica in the method (2), the dispersion stability of the fine particle silica is low, and both the polyurethane resin solution and the fine particle silica are easily separated with time. This is because the compatibility (affinity) between the polyurethane resin and the silica sol, the stability of the both to changes in pH, or the properties of the polyurethane resin and the surface of the fine particle silica are different.

  As another method, a method in which silica sol is added to the synthesis system during the synthesis reaction of the polyurethane resin can be considered. Of course, silica sol cannot be used in the method, and even if other solvent-based silica sol is used, a polyurethane resin solution having excellent dispersion stability of fine-particle silica cannot be obtained.

  However, the hydrophilic component described later used in the present invention has extremely high compatibility (affinity) with the silica sol due to its hydrophilicity, and can be stably mixed with the silica sol at an arbitrary ratio. Then, the silica sol dispersion medium is removed from this mixture by an arbitrary method to obtain a hydrophilic component in which fine-particle silica is dispersed very stably (hereinafter referred to as “fine-particle silica-dispersed hydrophilic component”). Even if the dispersion amount of the fine particle silica in the functional component increases, the increase in the viscosity of the hydrophilic component is small, and the fine particle silica-dispersed hydrophilic component and another polyurethane raw material are reacted in a solvent, thereby Even if it is not used, a dispersion in which fine particle silica is stably dispersed in the hydrophilic polyurethane resin solution can be obtained. When the hydrophilic polyurethane resin is synthesized without a solvent, the obtained hydrophilic polyurethane resin is dissolved in the soluble organic solvent, so that the silica particles are synthesized in the same manner as when the hydrophilic polyurethane resin is synthesized in the solvent. A stably dispersed hydrophilic polyurethane resin dispersion is obtained. Any of these hydrophilic polyurethane resin dispersions in which fine particle silica is dispersed is extremely transparent, and a film (film) formed therefrom is also transparent.

  The removal of the silica sol dispersion medium and the organic solvent from the hydrophilic component or a mixture of the solution and the silica sol can generally be easily performed under reduced pressure. In this case, the dispersion medium is preferably distilled off under reduced pressure and at a low temperature, and the dispersion medium is particularly preferably distilled off at a temperature of 70 ° C. or lower. When the dispersion medium is distilled off at a higher temperature than this, the fine particle silica in the silica sol may be aggregated, the dispersion stability of the fine particle silica is lowered, and the low-transparency fine particle silica-dispersed hydrophilic component is generated. Sometimes. The mixing ratio of the hydrophilic component and the silica sol is preferably such that the fine particle silica accounts for 5 to 95% by mass in the composition consisting of the finally obtained hydrophilic polyurethane resin and fine particle silica, more preferably 10 to 90%. It is the amount occupying mass%.

  In the present invention, the hydrophilic polyurethane resin used as the resin constituting the ink receiving layer is composed of a hydrophilic segment having a hydrophilic component as a structural unit and a compound having at least one compound having a tertiary amino group as a structural unit. It has a tertiary amino group-containing segment and a polysiloxane segment containing polysiloxane as a structural unit. When a chain extender is not used during the synthesis of the hydrophilic polyurethane resin, these segments are bonded at random by urethane bonds, urea bonds, or urethane-urea bonds, respectively. When a chain extender is used during the synthesis of the hydrophilic polyurethane resin, a short chain that is a residue of the chain extender exists between these bonds, in addition to the above bonds.

  By introducing a tertiary amino group and a polysiloxane segment in the molecule, the hydrophilic polyurethane resin in the present invention is provided with excellent adhesiveness to various materials, and the resin can form an ink receiving layer. When used, the formed ink-receiving layer is provided with excellent water absorption, antifogging properties, transparency, flexibility, water-based ink writing properties and water resistance, and further excellent blocking resistance and sliding properties. Sex is imparted.

  The reason why excellent water resistance is imparted to the ink receiving layer to be formed is not clear, but is considered as follows. Dyes, which are colorants for printing inks and inkjet inks, generally have anionic carboxyl groups or sulfonic acid groups in their molecules, and form the ink receiving layer of the recording sheet of the present invention. When the hydrophilic polyurethane resin and the above ink come into contact, an ionic bond is formed between the anionic group in the dye in the ink and the tertiary amino group in the resin, and It is considered that the fixing property of the dye and the water resistance of the recorded image are improved by the environmental responsiveness of the siloxane segment.

  However, in the presence of moisture, the ionic bonds as described above are easily dissociated, and it should not be expected to improve the water resistance of the image formed on the ink receiving layer. The water resistance of the formed image is significantly improved. The reason for this improvement in water resistance is not clear, but the polyurethane resin used in the present invention is hydrophilic, but there is also a hydrophobic part in the molecule, and the hydrophilic part (hydrophilic segment in the resin) ) And the tertiary amino group and the dye, the hydrophobic part of the polyurethane resin surrounds the hydrophilic part and the ionic bond part. Seems to improve.

  By the way, the introduction of a polysiloxane segment that is inherently hydrophobic (water repellent) into a polyurethane resin should not be expected to give good results in water absorption and hydrophilicity in an ink receiving layer containing the polyurethane resin. It is. However, the surface of the film formed from a polyurethane resin having a low polysiloxane segment content is completely covered with the polysiloxane segment in a dry state. However, when the film is immersed in water, the polysiloxane segment is in the resin film. It is known that there is a phenomenon of being buried in the surface, that is, environmental responsiveness (Polymer Journal, Vol. 48 [No. 4], p. 227 (1991), etc.).

  The present invention using a hydrophilic polyurethane resin having a hydrophilic segment and a polysiloxane segment utilizes the above phenomenon. That is, by appropriately controlling the polysiloxane segment content in the hydrophilic polyurethane resin, when printing with an aqueous ink or the like on the ink receiving layer containing the polyurethane resin, the surface is Shows hydrophilicity and good ink absorbency. On the other hand, the surface of the ink receiving layer at the time of drying or after drying is covered with a polysiloxane segment, and has excellent water resistance, blocking resistance, lubricity, etc. Expressed in the receptor layer. The present inventors have already clarified these effects in patent applications such as Japanese Patent Application No. 10-235545, Japanese Patent Application No. 10-240811, and Japanese Patent Application No. 10-170296.

  Next, the raw material of the hydrophilic polyurethane resin used in the present invention will be described. In the present invention, the compound used for introducing the tertiary amino group into the polyurethane resin is at least one active hydrogen-containing group (reactive group), for example, an amino group, an epoxy group, a hydroxyl group, a mercapto group, a carboxyl group. It is a compound having a group that can be converted into a hydroxyl group or a carboxyl group such as an alkoxy group, an acid halide group, a carboxy ester group, and an acid anhydride group, and having at least one tertiary amino group in the molecule. .

（式中の、Ｒ₁は炭素数２０以下のアルキル基、脂環族基、芳香族基（ハロゲン、アルキル基で置換されていてもよい）であり、Ｒ₂及びＲ₃は−Ｏ−、−ＣＯ−、−ＣＯＯ−、−ＮＨＣＯ−、−Ｓ−、−ＳＯ−、−ＳＯ₂−等で連結されていてもよい低級アルキレン基であり、Ｘ及びＹは−ＯＨ、−ＣＯＯＨ、−ＮＨ₂、−ＮＨＲ₁、−ＳＨ等の反応性基であり、Ｘ及びＹは同一でも異なってもよい。又、Ｘ及びＹは、上記の反応性基に誘導できるエポキシ基、アルコキシ基、酸ハライド基、酸無水物基、又はカルボキシルエステル基でもよい。） Preferable examples of the tertiary amino group-containing compound having a reactive group as described above include compounds represented by the following general formulas (1) to (3).

(In the formula, R ₁ is an alkyl group having 20 or less carbon atoms, an alicyclic group, or an aromatic group (which may be substituted with a halogen or an alkyl group), and R ₂ and R ₃ are —O—, A lower alkylene group which may be linked by —CO—, —COO—, —NHCO—, —S—, —SO—, —SO ₂ —, etc., and X and Y are —OH, —COOH, —NH ₂ , a reactive group such as —NHR ₁ , —SH, etc. X and Y may be the same or different, and X and Y are an epoxy group, an alkoxy group, an acid halide that can be derived from the reactive group described above. It may be a group, an acid anhydride group, or a carboxyl ester group.)

（式中の、Ｒ₁、Ｒ₂、Ｒ₃、Ｘ及びＹは前記と同じ定義であるが、但し二つのＲ₁同士は環状構造を形成するものであってもよい。Ｒ₄は−（ＣＨ₂）_n−（ｎは０〜２０の整数）である。）

(In the formula, R ₁ , R ₂ , R ₃ , X and Y are as defined above, but two R _{1 s} may form a cyclic structure. R ₄ is-( CH _{2) n} - (n is an integer of 0 to 20)).

（式中の、Ｘ及びＹは前記の定義と同じであり、Ｗは窒素含有複素環、窒素と酸素含有複素環、又は窒素と硫黄含有複素環を表す。）

(In the formula, X and Y are as defined above, and W represents a nitrogen-containing heterocycle, nitrogen and oxygen-containing heterocycle, or nitrogen and sulfur-containing heterocycle.)

  Specific examples of the compound represented by the general formula (1), (2) or (3) include the following. For example, N, N-dihydroxyethyl-methylamine, N, N-dihydroxyethyl-ethylamine, N, N-dihydroxyethyl-isopropylamine, N, N-dihydroxyethyl-n-butylamine, N, N-dihydroxyethyl-t -Butylamine, methyliminobispropylamine, N, N-dihydroxyethylaniline, N, N-dihydroxyethyl-m-toluidine, N, N-dihydroxyethyl-p-toluidine, N, N-dihydroxyethyl-m-chloroaniline N, N-dihydroxyethylbenzylamine, N, N-dimethyl-N ′, N′-dihydroxyethyl-1,3-diaminopropane, N, N-diethyl-N ′, N′-dihydroxyethyl-1,3 -Diaminopropane, N-hydroxyethyl-piperazine, N N-dihydroxyethyl-piperazine, N-hydroxyethoxyethyl-piperazine, 1,4-bisaminopropyl-piperazine, N-aminopropyl-piperazine, dipicolinic acid, 2,3-diaminopyridine, 2,5-diaminopyridine, 2 , 6-diaminopyridine, 2,6-diamino-4-methylpyridine, 2,6-dihydroxypyridine, 2,6-pyridine-dimethanol, 2- (4-pyridyl) -4,6-dihydroxypyrimidine, 2, There are 6-diaminotriazine, 2,5-diaminotriazole, 2,5-diaminooxazole and the like.

（上記式中のｎは１〜６０の整数を、ｍは１〜６の整数を表す。） Also, ethylene oxide adducts and propylene oxide adducts of these tertiary amino compounds can be used in the present invention. Examples of the adduct include compounds represented by the following structural formula.

(In the above formula, n represents an integer of 1 to 60, and m represents an integer of 1 to 6.)

  In the present invention, the polysiloxane used for introducing the polysiloxane segment into the polyurethane resin is a reactive group (active hydrogen-containing group) containing one or more active hydrogens in the molecule, such as an amino group. , Polysiloxane having an epoxy group, a hydroxyl group, a mercapto group, a carboxyl group or the like. Preferable examples of the polysiloxane having an active hydrogen-containing group include the following compounds.

(1) Amino-modified polysiloxane

(2) Epoxy-modified polysiloxane (these are used by opening the epoxy group)

(3) Alcohol-modified polysiloxane

(4) Mercapto-modified polysiloxane

(5) Carboxyl-modified polysiloxane

  The polysiloxanes having active hydrogen-containing groups listed above are examples of preferred compounds used in the present invention, and the present invention is not limited to these exemplified compounds. Accordingly, not only these exemplified compounds but also any other compounds that are currently commercially available and can be easily obtained from the market can be used in the present invention.

  As the organic polyisocyanate used in the present invention, any of those conventionally used in the synthesis of polyurethane resins can be used, and is not particularly limited. Preferred examples include 4,4′-diphenylmethane diisocyanate (MDI), hydrogenated MDI, isophorone diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 2,4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, etc., or polyurethane obtained by reacting these organic polyisocyanates with low molecular weight polyols or polyamines to form terminal isocyanates A prepolymer or the like can also be used.

As the hydrophilic component used in the present invention, those having a hydroxyl group, amino group, carboxyl group or the like in the molecule and having a weight average molecular weight in the range of 400 to 8,000 are preferable.
Examples of the polyol having a terminal hydroxyl group and hydrophilicity include polyethylene glycol, polyethylene glycol / polytetramethylene glycol copolymer polyol, polyethylene glycol / polypropylene glycol copolymer polyol, polyethylene glycol adipate polyol, polyethylene glycol succinate polyol, polyethylene Examples include glycol / poly-ε-caprolactone copolymer polyol and polyethylene glycol / polyvalerolactone copolymer polyol. Particularly preferred is polyethylene glycol.

  Examples of the polyamine having a terminal amino group and hydrophilicity include polyethylene oxide diamine, polyethylene oxide propylene oxide diamine, polyethylene oxide triamine, and polyethylene oxide propylene oxide triamine. Other examples include ethylene oxide adducts having a carboxyl group or a vinyl group.

  In the present invention, in order to impart water resistance to the hydrophilic polyurethane resin, it is also possible to use other polyols, polyamines, polycarboxylic acids and the like not having a hydrophilic chain together with the above hydrophilic component.

  As the chain extender used as necessary in the present invention, for example, any conventionally known chain extender such as a low molecular weight diol or diamine can be used, and it is not particularly limited. For example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, ethylenediamine, hexamethylenediamine and the like can be mentioned.

  The composition used in the present invention is obtained by removing the dispersion medium of silica sol from the above-mentioned mixture of the hydrophilic component and silica sol, that is, the fine particle silica-dispersed hydrophilic component, the organic polyisocyanate, and at least A compound having one active hydrogen-containing group and at least one tertiary amino group in the same molecule, and a polysiloxane having at least one active hydrogen-containing group, if necessary in the presence of a chain extender Thus, it can be obtained by reacting according to a conventionally known method for producing a polyurethane resin. The reaction may be performed in an organic solvent or without a solvent. When performed in an organic solvent, the resulting composition of the present invention is in a state in which fine-particle silica is stably dispersed in an organic solvent solution of a hydrophilic polyurethane resin. When the reaction is performed in the absence of a solvent, the obtained composition of the present invention is in the form of a solid, and the solid composition is used as a soluble organic solvent for the hydrophilic polyurethane resin constituting the composition. Dissolve and use. The soluble organic solvent is not particularly limited, and preferred examples include dimethylformamide and methyl ethyl ketone. These solvents can also be used in the synthesis of hydrophilic polyurethane resins. The solutions of the composition of the present invention are all dispersions in which fine particle silica is stably dispersed in a hydrophilic polyurethane resin solution.

  The molecular weight of the hydrophilic polyurethane resin constituting the composition used in the present invention is not particularly limited, and the weight average molecular weight (measured by GPC, converted to standard polystyrene) is preferably in the range of 3,000 to 800,000. More preferably, it is the range of 5,000-500,000.

  In the composition used in the present invention, the content of fine-particle silica is preferably an amount occupying 5 to 95% by mass, more preferably 10 to 90% by mass in the composition. When the content of the fine particle silica is less than 5% by mass, the surface characteristics of the ink receiving layer, such as blocking resistance and slipperiness, which are the objects of the present invention, are insufficiently expressed. This is not preferable because the strength of the layer and the adhesion of the ink receiving layer to the base material sheet are deteriorated. Surprisingly, when the content of the fine particle silica is 75 to 95% by mass, a microporous having a size of several m μm (nm) is obtained by coating the base sheet with a coating solution using the composition of the present invention. A film (ink receiving layer) that is high in quality and excellent in transparency is formed.

  The content of the tertiary amino group in the hydrophilic polyurethane resin in the present invention is preferably in the range of 0.1 to 50 meq (equivalent) / g, more preferably 0.5 to 20 meq / g. When the content of the tertiary amino group is less than 0.1 meq / g, that is, less than 1 per 10,000 molecular weight, the proportion of the high molecular weight hydrophilic segment is relatively large, which is an intended object of the present invention. Insufficient surface properties of the ink-receiving layer such as water resistance and blocking resistance are insufficient, while when the content of tertiary amino groups exceeds 50 meq / g, that is, 500 molecules per 10,000 molecular weight. On the other hand, the high molecular weight hydrophilic segment in the resin is relatively reduced, and as a result, the water repellency becomes strong, and the water absorbing performance and antifogging property of the ink receiving layer become inferior.

  The polysiloxane segment in the hydrophilic polyurethane resin in the present invention may be contained in the main chain or side chain of the resin, or in both. The content of the polysiloxane segment in the hydrophilic polyurethane resin is preferably 0.1 to 10% by mass, more preferably 2 to 10% by mass. If the content of the polysiloxane segment is less than 0.1% by mass, the excellent surface characteristics of the ink receiving layer such as water resistance, blocking resistance and slipperiness will be insufficient. On the other hand, if the content exceeds 10% by mass, the polysiloxane will be insufficient. The water repellency due to the segment becomes stronger, the high-quality image is not formed on the ink receiving layer, the environmental responsiveness used by the present invention is poor, and the water absorbing property, antifogging property and transparency of the ink receiving layer are inferior. It is not preferable.

  Moreover, 30-80 mass% is preferable, and, as for content of the hydrophilic segment in the hydrophilic polyurethane resin in this invention, More preferably, it is 50-75 mass%. If the content of the hydrophilic segment is less than 30% by mass, the water-absorbing and anti-fogging properties of the ink receiving layer to be formed become inferior. And it becomes inferior to blocking resistance, which is not preferable.

  As the base sheet of the recording sheet of the present invention, for example, paper, plastic film, glass, cloth, wood, metal and the like are used, but are not particularly limited. Examples of the paper include high quality paper, medium quality paper, coated paper, cast coated paper, and the like. Examples of the plastic film include sheets having a thickness of 50 to 250 μm, such as polyester, cellulose triacetate, polycarbonate, polyvinyl chloride, polypropylene, polyamide, polystyrene, polyethylene, polymethyl methacrylate, and the like. In addition, the base sheet is provided with a primer layer for providing adhesion to the ink receiving layer as required, a recording sheet curl prevention layer on the back surface of the base sheet on the non-receptive layer side, and a slipping layer for improving the coefficient of friction. Can also be provided.

  In the present invention, the above-described composition of the present invention is used to form an ink receiving layer. The resin component constituting the ink receiving layer may be the hydrophilic polyurethane resin alone in the above composition, but depending on the composition of the ink for ink jet recording used for printing, the ink receiving layer has hydrophilicity and / or water absorption. Further, a known water-soluble polymer may be used in combination with the composition for further imparting or adjusting. Examples of these water-soluble polymers include polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, CMC, cellulose derivatives, polyvinyl pyrrolidone, polyacrylic acid, polyacrylic acid copolymer, starch, cationic starch, gelatin, and casein. Is mentioned.

  Further, in order to further impart water resistance and durability to the ink receiving layer and the printed image of the recording sheet of the present invention, a hydrophobic polymer may be used in combination with the hydrophilic polyurethane resin. Examples of these hydrophobic polymers include polyester resin, polyvinyl chloride resin, polystyrene resin, polymethyl methacrylate resin, polycarbonate resin, polyurethane resin, vinyl chloride-vinyl acetate copolymer resin, acrylonitrile-styrene copolymer resin, polyvinyl chloride. Examples thereof include synthetic resins generally used for forming the ink receiving layer, such as butyral resin, polyamide resin, epoxy resin, urea resin, and melamine resin.

  In addition, for the purpose of improving the ink absorbability, fixability, color developability, and blocking resistance and water resistance of the ink receiving layer of the recording sheet of the present invention, the composition of the present invention contains inorganic and organic pigments, Resin particles and the like can be contained. Examples of pigments and resin particles used include kaolin, delaminated kaolin, aluminum hydroxide, silica, diatomaceous earth, calcium carbonate, talc, titanium oxide, calcium sulfate, barium sulfate, zinc oxide, alumina, calcium silicate, magnesium silicate, Mineral pigments such as colloidal silica, zeolite, bennite, sericite, lithopone, porous pigments, polystyrene resin, urea resin, acrylic resin, melamine resin, benzoguanamine resin, polyurethane resin, other fine particles such as organic pigment, porous fine particles and Among known pigments such as hollow particles and resin particles, one or more kinds are appropriately used according to the quality design of the ink receiving layer. In this case, the amount of these pigments and resin particles used is in the range of 0 to 95% by mass, preferably 10 to 90% by mass, based on the total solid content of the composition of the present invention used for forming the ink receiving layer.

  Further, if necessary, the composition of the present invention may be used in addition to the above thickeners, mold release agents, penetrants, wetting agents, thermal gelling agents, sizing agents, antifoaming agents, foam suppressors, foaming agents, and coloring agents. Agent, fluorescent brightening agent, ultraviolet absorber, antioxidant, quencher agent, preservative, antistatic agent, crosslinking agent, dispersant, lubricant, plasticizer, pH adjuster, fluidity improver, solidification accelerator, Various auxiliaries such as water-resistant agents can be appropriately blended.

  As the composition of the present invention used for forming the ink receiving layer of the recording sheet of the present invention, it is preferable to use the solution of the composition of the present invention synthesized in a solvent as it is, without using any solvent. When the composition is produced, the composition can be used by dissolving in a suitable solvent. If necessary, a solvent-soluble or insoluble additive may be added to these solutions. The solution is usually prepared as a paint having a solid content of about 5 to 15% by mass.

  The ink-receiving layer is formed by applying and drying the paint on at least one side of the substrate sheet by gravure coating, direct or reverse roll coating, wire bar coating, air knife coating, curtain coating, blade coating, rod coating, die coating, etc. . Furthermore, the ink receiving layer after drying is subjected to surface finishing using a calendar such as a machine calendar, a super calendar, or a soft calendar, whereby the recording sheet of the present invention is obtained.

The thickness of the ink receiving layer formed, the thickness to be 5 to 100 g / m ² approximately on a dry coated amount of the coating material is preferred, more preferably 10 to 50 g / m ² approximately. When the thickness of the ink receiving layer is less than 5 g / m ² , the ink absorption by the ink receiving layer becomes insufficient, and when the thickness exceeds 100 g / m ² , the obtained effect becomes saturated and uneconomical. Generation of cracks or curling of the recording sheet is likely to occur.

  Next, the present invention will be described in more detail with reference examples, examples and comparative examples. In the text, “part” or “%” is based on mass unless otherwise specified.

Reference example 1
700 parts of polyethylene glycol (molecular weight 1,000) and 1,500 parts of silica water sol (silica average particle size 10 to 20 nm, solid content 20%) were mixed thoroughly, and the resulting mixture was stirred at 70 ° C. Under reduced pressure. After the theoretical amount of water was distilled off, the temperature was raised to 120 ° C. and water was further removed under reduced pressure of 133.3 Pa or less to obtain a white solid polyol (A) having a silica content of 30%. This polyol (A) had a hydroxyl value of 76 mgKOH / g, a water content of 0.15%, and became a transparent liquid at 80 ° C. The viscosity of the liquid at that time was 450 dPa · s.

Reference example 2
100 parts of polyethylene glycol (molecular weight 590) and 500 parts of silica water sol (silica average particle size 200-230 nm, solid content 30%) are thoroughly mixed, and the resulting mixture is stirred under reduced pressure at 70 ° C. with stirring. went. After the theoretical amount of water was distilled off, the temperature was raised to 120 ° C. and water was further removed under reduced pressure of 133.3 Pa or less to obtain a white solid polyol (B) having a silica content of 50%. This polyol (B) was softened at a hydroxyl value of 95 mgKOH / g, a moisture content of 0.12%, and 110 ° C.

Reference example 3
100 parts of polyethylene oxide diamine (Jefamine ED manufactured by Texaco Chemical Co., Ltd .; molecular weight 600) and 2,250 parts of silica methanol sol (silica average particle size 20-30 nm, solid content 40%) were sufficiently mixed, and the resulting mixture was obtained. Under reduced pressure, methanol was removed under reduced pressure at 70 ° C. After the theoretical amount of methanol was distilled off, the temperature was raised to 120 ° C. and the methanol content was further removed under a reduced pressure of 133.3 Pa or less to obtain a white solid polyamine (C) having a silica content of 90%. This polyamine (C) was softened at an amine equivalent of 30 g / mol, a methanol fraction of 0.20%, and 130 ° C.

上記構造のポリジメチルシロキサンポリオール（分子量３，２００）５部と、参考例１のポリオール（Ａ）１４５部と、Ｎ−メチルジエタノールアミン２０部とジエチレングリコール３部とを、２００部のメチルエチルケトンと２００部のジメチルホルムアミドとの混合溶剤中に溶解し、６０℃でよく撹拌しながら、７７部の水添ＭＤＩを１００部のメチルエチルケトンに溶解した溶液を徐々に滴下した。滴下終了後、８０℃で８時間反応させた後、ジメチルホルムアミド５００部を加えて本発明で用いる組成物（塗料）を得た。 Reference example 4
(Production of composition used in the present invention)

5 parts of polydimethylsiloxane polyol (molecular weight 3,200) having the above structure, 145 parts of polyol (A) of Reference Example 1, 20 parts of N-methyldiethanolamine and 3 parts of diethylene glycol, 200 parts of methyl ethyl ketone and 200 parts of While dissolving in a mixed solvent with dimethylformamide and stirring well at 60 ° C., a solution in which 77 parts of hydrogenated MDI was dissolved in 100 parts of methyl ethyl ketone was gradually added dropwise. After completion of dropping, the mixture was reacted at 80 ° C. for 8 hours, and then 500 parts of dimethylformamide was added to obtain a composition (paint) used in the present invention.

  The above composition has a solid content of 20%, a viscosity of 50 dPa · s (25 ° C.), and is measured by GPC of the hydrophilic polyurethane resin constituting the composition, and has a weight average molecular weight in terms of standard polystyrene ( The same applies to the following examples) is 62,000, the tertiary amino group content in the resin is 0.80 meq / g, the hydrophilic segment content is 49.1%, and the polysiloxane segment content is The amount was 2.3%, and the content of silica in the composition (solid content) was 17.3%.

上記構造のエチレンオキシド付加型ポリジメチルシロキサンポリオール（分子量４，５００）５部と、参考例２のポリオール（Ｂ）１２０部と、ポリエチレンオキサイドジアミン（分子量２，０００）２５部と、Ｎ，Ｎ−ジメチル−Ｎ′，Ｎ′−ジヒドロキシエチル−１，３−ジアミノプロパン２５部とを２００部のメチルエチルケトンと２００部のジメチルホルムアミド混合溶剤中に溶解し、６０℃でよく撹拌しながら、６４部の水添ＭＤＩを１００部のメチルエチルケトンに溶解した溶液を徐々に滴下した。滴下終了後、８０℃で８時間反応させた後、ジメチルホルムアミド４５５部を加えて本発明で用いる組成物（塗料）を得た。 Reference Example 5
(Production of composition used in the present invention)

5 parts of ethylene oxide addition type polydimethylsiloxane polyol (molecular weight 4,500) of the above structure, 120 parts of polyol (B) of Reference Example 2, 25 parts of polyethylene oxide diamine (molecular weight 2,000), N, N-dimethyl -N ', N'-dihydroxyethyl-1,3-diaminopropane (25 parts) is dissolved in 200 parts of methyl ethyl ketone and 200 parts of dimethylformamide mixed solvent, and 64 parts of hydrogenation is stirred well at 60 ° C. A solution prepared by dissolving MDI in 100 parts of methyl ethyl ketone was gradually added dropwise. After completion of the dropwise addition, the mixture was reacted at 80 ° C. for 8 hours, and 455 parts of dimethylformamide was added to obtain a composition (paint) used in the present invention.

  The composition had a solid content of 20% and a viscosity of 40 dPa · s (25 ° C.). The hydrophilic polyurethane-polyurea resin constituting the composition has a weight average molecular weight of 41,000, the tertiary amino group content in the resin is 0.72 meq / g, and the polysiloxane segment content. 2.3%, the content of the hydrophilic segment was 47.5%, and the content of silica in the composition (solid content) was 25.0%.

上記構造のポリジメチルシロキサンジアミン（分子量３，８８０）２部と、参考例３のポリアミン（Ｃ）１４８部と、メチルイミノビスプロピルアミン３部とをジメチルホルムアミド２５０部に溶解し、内温を０〜−５℃に保持して十分に撹拌しながら１２部の水添ＭＤＩを１００部のジメチルホルムアミドに溶解した溶液を徐々に滴下して反応させた。滴下終了後、次第に内温を上昇させ、５０℃に達した時点で更に５時間反応させた後、ジメチルホルムアミド３１０部を加えて本発明で用いる組成物（塗料）を得た。 Reference Example 6
(Production of composition used in the present invention)

2 parts of polydimethylsiloxane diamine (molecular weight 3,880) having the above structure, 148 parts of polyamine (C) of Reference Example 3 and 3 parts of methyliminobispropylamine are dissolved in 250 parts of dimethylformamide, and the internal temperature is reduced to 0. A solution prepared by dissolving 12 parts of hydrogenated MDI in 100 parts of dimethylformamide was gradually dropped and reacted while maintaining at -5 ° C and stirring sufficiently. After completion of the dropwise addition, the internal temperature was gradually raised, and when the temperature reached 50 ° C., the mixture was further reacted for 5 hours, and then 310 parts of dimethylformamide was added to obtain a composition (paint) used in the present invention.

  The above composition has a solid content of 20% and a viscosity of 110 dPa · s (25 ° C.), and the hydrophilic polyurea resin constituting the composition has a weight average molecular weight of 38,000. In the composition (solid content), the content of the tertiary amino group is 0.60 meq / g, the content of the polysiloxane segment is 6.2%, and the content of the hydrophilic segment is 46.5%. The silica content was 80.7%.

Reference Example 7
A polyurethane resin solution (coating material) was prepared using the same material and formulation as in Reference Example 4 except that polydimethylsiloxane polyol and N-methyldiethanolamine were not used, and the polyol (A) of Reference Example 1 except for the silica was used. ) This solution had a solid content of 20%, a viscosity of 80 dPa · s (25 ° C.), and the polyurethane resin had a weight average molecular weight of 69,000.

Reference Example 8
Polydimethylsiloxane polyol and N, N-dimethyl-N ′, N′-dihydroxyethyl-1,3-diaminopropane are not used, and the polyol (B) of Example 2 excluding silica is used. Otherwise, a polyurethane-polyurea resin solution (paint) was obtained using the same materials and formulation as in Reference Example 5. This resin solution had a solid content of 20% and a viscosity of 52 dPa · s (25 ° C.), and the weight-average molecular weight of the polyurethane-polyurea resin was 58,000.

Reference Example 9
A polyurea resin solution (by the same material and formulation as in Reference Example 6) except that polydimethylsiloxane diamine and methyliminobispropylamine were not used, and the polyamine (C) of Reference Example 3 except for the silica was used. Paint). This resin solution had a solid content of 20% and a viscosity of 38 dPa · s (25 ° C.), and the polyurea resin had a weight average molecular weight of 42,000.

Reference Examples 10-12
The silica water sol or silica methanol sol used in Reference Examples 1 to 3 was added to the resin solutions of Reference Examples 7 to 9 with stirring, but the fine particle silica was precipitated, and these solutions (paints) were opaque. became.

Reference Example 13
A 5% aqueous solution (paint) of polyvinyl alcohol (polymerization degree 550) having a saponification degree of 98.5 mol% was prepared.

Examples 1-3
Each of the compositions (paints) of the present invention obtained in Reference Examples 4 to 6 was applied to a high-quality paper having a basis weight of 35 g / m ² and dried with an air knife coater so that the thickness after drying was 25 μm. Thus, an ink receiving layer was formed to obtain a recording sheet of the present invention.

Comparative Examples 1-7
Each of the resin solutions (paints) obtained in Reference Examples 7 to 13 was applied and dried on a high-quality paper having a basis weight of 35 g / m ² with an air knife coater so that the thickness after drying was 25 μm. A receiving layer was formed to obtain a recording sheet of a comparative example.

[Evaluation of recording sheet]
The 10 types of recording sheets obtained as described above are printed using four colors of yellow, magenta, cyan, and black with an ink jet printer (PM-800C manufactured by Seiko Epson Corporation) that records and records with water-soluble dye ink. Records were made and the following items were evaluated.

(1) Blocking resistance An untreated PET film was stacked on the surface of the ink receiving layer, and the blocking resistance after standing for one day at a load of 0.29 MPa and a temperature of 40 ° C. was evaluated. The results are displayed as follows:
○: No blocking property Δ: Some blocking property ×: Blocking property

(2) Transparency The haze on the surface of the ink receiving layer was visually determined. The results are displayed as follows:
○: Completely transparent △: Slightly cloudy ×: Completely opaque

(3) Color clarity The color clarity of the obtained color image was visually observed after color printing on the ink receiving layer with an inkjet printer. The results are displayed as follows:
○: Clear with no blurring △: Slightly blurring and slightly blurry

(4) Dryability of ink After color printing on the ink receiving layer with an ink jet printer, the filter paper was pressed against the print surface for 5 seconds under a load of 50 g / m ² , and the time until the ink was not transferred to the filter paper was measured.

(5) Water resistance of the printed image After color printing on the ink receiving layer with an ink jet printer, the recording sheet is immersed in water (20 ° C, 1 hour), and then dried at room temperature. Was observed visually. The results are displayed as follows:
○: No blurring or color change in the image Δ: Change is observed in the image and the film ×: The image can be considerably taken or the entire film can be taken Table 1 shows the above evaluation results.

According to the present invention, an ink excellent in ink absorbability, drying property, and color developability, capable of stably recording a high-quality printed image, and further having excellent transparency, blocking resistance, and water resistance of the printed image. A recording sheet having a receiving layer can be provided.

Claims (10)

  In an inkjet recording sheet in which at least one ink receiving layer is provided on at least one side of a substrate sheet, the ink receiving layer comprises an organic polyisocyanate, a high molecular weight hydrophilic polyol and / or a polyamine, and at least one Hydrophilic polyurethane resin obtained by reacting a compound having an active hydrogen-containing group and at least one tertiary amino group in the same molecule with a polysiloxane having at least one active hydrogen-containing group in the molecule And an ink jet recording sheet, characterized in that the ink jet recording sheet is formed using a composition comprising fine particle silica.   The inkjet recording sheet according to claim 1, wherein the content of the fine-particle silica is an amount occupying 5 to 95 mass% in the composition.   The inkjet recording sheet according to claim 1, wherein the fine particle silica is added to the high molecular weight hydrophilic polyol and / or polyamine when the hydrophilic polyurethane resin is synthesized.   The inkjet recording sheet according to claim 1, wherein the fine particle silica is fine particle silica having an average particle diameter of 1 to 300 nm.   The hydrophilic segment, tertiary amino group, and polysiloxane segment content in the hydrophilic polyurethane resin is 30 to 80% by mass, 0.1 to 50 meq / g, and 0.1 to 10% by mass, respectively. 2. An ink jet recording sheet according to 1.   In a method for producing an inkjet recording sheet by providing at least one ink receiving layer on at least one side of a substrate sheet, the ink receiving layer comprises an organic polyisocyanate, a high molecular weight hydrophilic polyol and / or a polyamine, and at least Hydrophilic property obtained by reacting a compound having one active hydrogen-containing group and at least one tertiary amino group in the same molecule with a polysiloxane having at least one active hydrogen-containing group in the molecule A method for producing an inkjet recording sheet, comprising: forming a coating material comprising a composition comprising a conductive polyurethane resin and fine-particle silica by applying and drying on at least one side of a substrate sheet.   The method for producing an ink jet recording sheet according to claim 6, wherein the fine particle silica is added to the high molecular weight hydrophilic polyol and / or polyamine when the hydrophilic polyurethane resin is synthesized.   The method for producing an ink jet recording sheet according to claim 6, wherein the content of the fine particle silica is an amount occupying 5 to 95% by mass in the composition.   The method for producing an ink jet recording sheet according to claim 6, wherein the fine particle silica is fine particle silica having an average particle diameter of 1 to 300 nm. The hydrophilic segment, tertiary amino group, and polysiloxane segment content in the hydrophilic polyurethane resin is 30 to 80% by mass, 0.1 to 50 meq / g, and 0.1 to 10% by mass, respectively. 6. A method for producing an inkjet recording sheet according to 6.