JP4154321B2 - Method for producing inkjet recording sheet - Google Patents

Description

  The present invention relates to a method for producing an ink jet recording sheet. More specifically, the present invention provides a printed image with excellent water resistance and moisture resistance, excellent ink absorbability and ink color development, and a stable, high-quality printed image. In addition, the present invention relates to a method for producing an ink jet recording sheet having an ink receiving layer that is excellent in transparency, transportability, and blocking resistance.

  The ink jet recording method is based on various operating principles such as electrostatic attraction method, a method of applying mechanical vibration or transition to the ink using a piezoelectric element, a method of heating and foaming the ink and utilizing its pressure, etc. It is used to record images, characters, etc. by flying fine droplets and attaching them to a recording sheet such as paper. Various recording methods are available for high-quality printing and multi-color printing with little noise generation. It is rapidly spreading to applications.

  In such a recording medium used for ink-jet recording, the ink adhering to the recording medium is blotted and flowed, so that the ink is quickly absorbed and the clear ink is not lost. In order to form dots, there are paper sheets and other supports that are provided with an ink-receiving layer mainly composed of various pigments and resins, or recording sheets in which porous pigments are embedded in the paper itself. Proposed.

  For example, the ink-receiving layer is composed of a water-soluble polymer (Patent Document 1) using a combination of an inorganic pigment and an organic pigment as a pigment (Patent Document 1) or a polyvinyl alcohol copolymer having fine powder silica and a silanol group (Patent Document). 2) etc. are proposed.

However, as the performance of inkjet recording devices such as higher speed, higher definition, or full color is improved and applications are expanded, it is required that inkjet recording sheets also have the following advanced characteristics. Became.
(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, a porous pigment or a water-soluble polymer having excellent ink absorbability is used as a component of an ink receiving layer provided on an ink jet recording sheet to satisfy these requirements, or water resistance of the ink receiving layer is improved. It has been proposed and studied to use latex for the substrate, and further to use synthetic paper or plastic having water resistance for the support itself.

However, those using paper as a support or using only a water-soluble polymer as an ink-receiving layer have poor water resistance, bleeding of printed portions, and poor image clarity.
In addition, in the case where the porous pigment is dispersed in the ink receiving layer, the porous pigment generally decreases transparency so that it is usually used as a matting agent (matting agent). Even if the dispersion amount is small, the transparency is remarkably lowered.
On the other hand, when using synthetic paper or plastic film for the support or using latex for the resin of the ink receiving layer, there are problems with the adhesion between the ink receiving layer and the support, the ink absorbability and the drying property. .

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

  The present invention has been made in view of the above circumstances. The present invention is particularly excellent in water-based ink absorbability, sharp ink dot shape, excellent ink color development, and stable high-quality printing. An object of the present invention is to provide an ink jet recording sheet which gives an image and further has an ink receiving layer having excellent transportability, transparency, blocking resistance, water resistance and moisture resistance.

The above object is achieved by the present invention described below.
That is, the present invention relates to a method for producing an ink jet 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 comprising an organic polyisocyanate, a high molecular weight hydrophilic polyamine, A hydrophilic polyurea resin having a hydrophilic segment and a tertiary amino group is synthesized by reacting a compound having at least one active hydrogen-containing group and at least one tertiary amino group in the same molecule. when, as at least a part of the high molecular weight hydrophilic polyamine, will be formed by using a mixture obtained by using the silica dispersion hydrophilic polyurea resin composition of high molecular weight hydrophilic polyamine and silica sol, the mixture of high molecular weight It is obtained by removing the dispersion solvent of silica sol from the mixture of hydrophilic polyamine and silica sol. Is an inkjet recording sheet manufacturing method, characterized in that that.

Having an ink-receiving layer hydrophilic segment and composition comprising a hydrophilic polyurethane A resin and particulate silica having a tertiary amino group (Silica Dispersion hydrophilic polyurethane A resin composition) is configured as a resin component of the present invention The ink jet recording sheet is excellent in ink drying property and color developability, gives a stable and high-quality printed image, and is further excellent in transparency, blocking resistance and water resistance of the ink receiving layer and the printed image.

Next, the present invention will be described in more detail.
The inkjet recording sheet of the present invention, the ink receiving layer is composed of the hydrophilic polyurethane A resin and particulate silica of the resin component.

Hydrophilic polyurethane A resin used in the present invention, an organic polyisocyanate, a high molecular weight and a hydrophilic polyamine, a compound having at least one active hydrogen-containing group and at least one tertiary amino group in the same molecule And, if necessary, a hydrophilic segment obtained by reacting with a chain extender and a tertiary amino group.

On the other hand, the finely-divided silica is the time of synthesizing the hydrophilic polyurethane A resin, as at least part of the high molecular weight hydrophilic polyamine, by using a mixture of a high molecular weight hydrophilic polyamine and silica sol, resulting hydrophilic polyurethane A It is contained (dispersed) in the resin. This, in the present invention referred to as silica-dispersed hydrophilic polyurethane A resin composition. Finely-divided silica is less regardless of the amount, and despite not using a dispersing agent, are stably dispersed in a solution of hydrophilic polyurethane A resin. The silica dispersion hydrophilic polyurethane ink-receiving layer of the inkjet recording sheet of the present invention with reference to A resin composition is formed.

In the present invention, the mixture of the high molecular weight hydrophilic polyamine and the fine particle silica is not obtained by mechanically mixing and dispersing the fine particle silica in the high molecular weight hydrophilic polyamine, but the dispersion solvent of the silica sol from the mixture of the polyamine and the silica sol. Use the one obtained by removing. When the polyamine is used as a solution of these soluble solvents, this solvent is also removed.
The silica sol in the present invention is obtained by stably dispersing fine particle silica or a fine particle silica compound in water and / or alcohol as a dispersion solvent. In addition to the above, ketones, esters, and other organic solvents are also used as the dispersion solvent. 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).

When forming an ink receiving layer of ink jet recording paper, a method using a resin solution, a dispersion, or the like is common.
As a method for dispersing the fine particles of silica in a solution of polyurethane A resin, and the following methods. For example, fine particulate silica were dispersed using a conventional dispersing mixer to polyurethane A resin, a method to use it is dissolved in a solvent (1), a method of adding and dispersing fine particles of silica or silica sol polyurethane A resin solution ( 2) can be considered. However, method (1) is economically disadvantageous because a stable dispersion cannot be obtained even if a dispersant is used. Method (2) is a general method, but even if this method or a dispersant is used, fine particle silica cannot be stably dispersed. Even when silica sol is used, the dispersion stability is low, and both are easily separated with time. The reason for this is due to polyurethane A resin and compatibility with the finely-divided silica (affinity) and stability against pH changes both or polyurethane A resin and properties vary or the like on the surface of the finely-divided silica.
Alternatively, it is also considered a method of adding the synthetic silica sol during the synthesis reaction of polyurethane A resin dispersant silica sol of water or alcohol, since it reacts with isocyanate, can not use, of course, other of polyurethane a resin solution be used silica sol of the solvent system with dispersion stability can not be obtained.

However, the high molecular weight hydrophilic polyamine described later used in the present invention has extremely high compatibility (affinity) with silica due to its hydrophilicity, and can be stably mixed with silica sol at an arbitrary ratio. Then, by removing the dispersion medium of silica sol from this mixture by an arbitrary method, a high molecular weight hydrophilic polyamine in which fine particle silica is dispersed extremely stably is obtained, and the amount of fine particle silica dispersed in the high molecular weight hydrophilic polyamine is obtained. There is also increased, viscosity increase of the polyamine is small, and by reacting in a solvent a mixture with ingredients of other hydrophilic polyurethane a resin, hydrophilic polyurethane a resin without using a dispersing agent A dispersion in which fine particle silica is stably dispersed in the solution is obtained. When reacted without a solvent, the same stable dispersions and described above can be obtained by dissolving the hydrophilic polyurethane A resin in its soluble solvent. All of these dispersions are extremely transparent, and the film formed therefrom is also transparent.

The removal of the silica sol dispersion medium or the organic solvent from the high molecular weight hydrophilic polyamine or a mixture of the solution and the silica sol can generally be easily distilled off under reduced pressure or the like. In this case, the distillation is preferably carried out at a low temperature under reduced pressure, and particularly preferably distilled off at 70 ° C. or lower. When the temperature is higher than this, aggregation of fine-particle silica may occur, the dispersion stability of silica may be lowered, and a silica-dispersed high molecular weight hydrophilic polyamine having low transparency may be generated. The mixing ratio of the high molecular weight hydrophilic polyamine and silica sol, the silica dispersibility hydrophilic polyurethane A resin composition in which fine particles of silica are produced amount corresponding to 5 to 95 wt% in (solids) are preferred, more preferably 10 to The amount is 90% by mass.

Hydrophilic polyurethane A resin used as the resin constituting the ink-receiving layer in the present invention have at least one tertiary amino group and the hydrophilic segment and the structural unit of high molecular weight hydrophilic polyamine in the same molecule And a tertiary amino group-containing segment containing the compound as a structural unit. When no chain extender is used, these segments are bonded at random by urethane bonds, urea bonds, or urethane-urea bonds. When a chain extender is used, there is a bond in which a short chain that is a residue of the chain extender exists between these bonds together with these bonds.

By tertiary amino groups in the molecule are introduced, the hydrophilic polyurethane A resin in the present invention have excellent adhesion to various materials, and excellent water absorption, anti-fogging resistance, transparency, flexibility In addition, the writing property of water-based ink and excellent water resistance, blocking resistance, and lubricity are imparted.

The reason why water resistance is imparted is not clear, but is considered as follows. Dye or pigment molecules printing ink or inkjet ink is generally have anionic carboxyl group or sulfonic acid group in the molecule, the hydrophilic polyurethane A resin and the introduced tertiary amino group When the dye / pigment is mixed or contacted, an ionic bond is formed between the dye / pigment and the tertiary amino group in the resin, thereby fixing the dye / pigment and water resistance of the recorded image. Is thought to improve.

However, in view of the fact that the above ionic bonds are easily dissociated in the presence of moisture, the reason for the improvement in water resistance is not clear. Perhaps polyurethane A resin in the present invention is a hydrophilic, hydrophobic moieties in the molecule are also present, between the hydrophilic portion and a tertiary amino group and dye-pigments in the resin After the ionic bond is formed, the hydrophobic part seems to surround the ionic bond part, so that the water resistance is considered to be improved.

Compound used to introduce a tertiary amino group in the molecular chain constituting the hydrophilic polyurethane A resin in the present invention, at least one active hydrogen-containing group (as reactive groups), for example, an amino group, It is a compound having an epoxy group, a hydroxyl group, a mercapto group, a carboxyl group, an alkoxy group, an acid halide group, a carboxyester group, an acid anhydride group, etc., and having at least one tertiary amino group in the molecular chain. .

（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、これらの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 the following compounds.
The compound represented by General formula (1).

(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 an epoxy group, an alkoxy group, an acid halide group, an acid anhydride group that can be derived from these groups. Or a carboxyester 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。） A compound represented by the general formula (2).

(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わす。） A compound represented by the general formula (3).

(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.
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,
2,6-diaminotriazine,
2,5-diaminotriazole,
There are 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. As the adduct, for example,

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

The organic polyisocyanates used in the present invention, can be used either those which are conventionally used in the synthesis of polyurethane A resin 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, Polyurethane obtained by reacting 6-tolylene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, etc., or these organic polyisocyanates with low molecular weight polyols or polyamines to be terminal isocyanates A prepolymer or the like can also be used.

  As the high molecular weight hydrophilic polyamine used in the present invention, those having a weight average molecular weight of 400 to 8,000 having an amino group in the molecule are preferable.

Examples of the high molecular weight hydrophilic polyamine having a terminal amino group and hydrophilicity include:
Polyethylene oxide diamine,
Polyethylene oxide, propylene oxide diamine,
Polyethylene oxide triamine,
Polyethylene oxide propylene oxide triamine, etc.
Is mentioned.

In the present invention, in order to impart water resistance to hydrophilic polyurethane A resin together with the hydrophilic polyamine, other polyol having no hydrophilic chain, polyamine, also possible to appropriately copolymerizing polycarboxylic acid It is.

  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.

Silica Dispersion hydrophilic polyurethane A resin composition for use in the present invention, as a part or all of the above high molecular weight hydrophilic polyamine, such as by removing the dispersion solvent such silica sols from a mixture of these, respectively silica sol Using the high molecular weight hydrophilic polyamine in which the resulting fine particle silica is dispersed, either or both of them and the organic polyisocyanate, and at least one active hydrogen-containing group and at least one tertiary amino group are the same molecule. compounds having in the a chain extender as required, can be obtained by reacting in accordance with the production method of the previously known polyurethane a resin. The reaction may be solventless or a reaction in an aqueous solution or an organic solvent. In the case of solvent-free, silica-dispersed hydrophilic polyurethane A resin composition obtained is used by dissolving the soluble solvent of the hydrophilic polyurethane A resin. The soluble solvent is not particularly limited, and preferred examples include dimethylformamide and methyl ethyl ketone. The solvent used in the synthesis of the hydrophilic polyurethane A resin versa. Silica Dispersion hydrophilic polyurethane A resin composition obtained is finely-divided silica in a hydrophilic polyurethane A resin solution is a dispersion are stably dispersed. If the hydrophilic polyurethane A resin was synthesized in a solventless also when it is dissolved in a soluble solvent of the resin, dispersion particles of silica are dispersed stably in a solution of the resin is obtained.

The molecular weight of the hydrophilic polyurethane A resin having a hydrophilic segment and a tertiary amino group-containing segment for use in the present invention in the molecular chain is not particularly limited, the weight-average molecular weight (measured by GPC, and standard polystyrene) of 3 The range is preferably from 5,000 to 800,000, more preferably from 5,000 to 500,000.

In silica dispersion hydrophilic polyurethane A resin composition for use in the present invention, the content of the finely-divided silica is preferably 5 to 95 mass% in the composition, more preferably from 10 to 90 wt%. If the content of the fine-particle silica is less than 5% by mass, the surface properties such as blocking resistance and lubricity, which are the objects of the present invention, will be insufficient. On the other hand, if it exceeds 95% by mass, the strength of the film and the adhesion to the substrate It is not preferable because it becomes inferior. Surprisingly, when the content of the finely-divided silica is 75 to 95% by mass, by coating the substrate with the coating liquid using silica dispersion hydrophilic polyurethane A resin composition of the present invention, the number Emumyuemu ( nm) size microporous film with excellent transparency is formed.

The content of the tertiary amino groups of the hydrophilic polyurethane A in the resin in the present invention is preferably in the range 0.1~50eq of (eq) / kg, more preferably from 0.3~20eq / kg. When the content of the tertiary amino group is less than 0.1 eq / kg, that is, 1 or less per 10,000 molecular weight, the properties such as water resistance and blocking resistance, which are the intended purposes of the present invention, are insufficient. On the other hand, when the content of the tertiary amino group exceeds 50 eq / kg, that is, more than 500 per 10,000 molecular weight, the water repellency increases due to the decrease in the hydrophilic portion in the resin, and the water absorption performance and the water resistance are reduced. Since it becomes inferior in cloudiness, it is not preferable.

The content of the hydrophilic segments in the hydrophilic polyurethane A resin in the present invention is preferably in the range of 30 to 80 wt%, still more preferably from 50 to 75 wt%. If the content of the hydrophilic segment is less than 30% by mass, the water absorption and antifogging properties are inferior. On the other hand, if it exceeds 80% by mass, the water resistance and blocking resistance are inferior.

As the base material sheet of the ink jet 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 and a slipping layer for improving the friction coefficient on the back surface of the base sheet on the non-receptive layer side as necessary. You can also

The silica dispersion hydrophilic polyurethane A resin composition is used to form an ink-receiving layer in the present invention.
As the resin component constituting the ink-receiving layer, said or hydrophilic polyurethane A resin alone, the composition of the inkjet recording ink, in order to adjust or hydrophilic and / or water-absorbing further imparting the hydrophilic polyurethane a resin in combination a water-soluble polymer may be used.
Examples of the water-soluble polymer include polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, CMC, cellulose derivatives, polyvinyl pyrrolidone, polyacrylic acid, polyacrylic acid polymer, starch, cationic starch, gelatin, and casein. .

In order to further impart water resistance and durability to the ink-receiving layer and printed images may be used in combination of hydrophobic polymer to said hydrophilic polyurethane A resin. Examples of the hydrophobic polymer 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 butyral resin. And synthetic resins generally used for forming the ink receiving layer, such as polyamide resin, epoxy resin, urea resin, melamine resin and the like.

Further, the absorption of the ink of an ink-receiving layer, fixing property, coloring property, even for the purpose of improving the blocking resistance and water resistance, the silica dispersion hydrophilic polyurethane A resin composition, inorganic and organic pigments and resin particles Etc. 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, calcium silicate, magnesium silicate, and colloidal silica. Mineral pigments such as zeolite, bennite, sericite, lithopone, porous pigments, polystyrene resins, urea resins, acrylic resins, melamine resins, benzoguanamine resins, polyurethane resins, other organic pigments, porous fine particles and hollow particles Among the known pigments and resin particles such as the above, one or more kinds are appropriately used according to the quality design of the recording sheet for inkjet. In this case, the amount of these pigments and resin particles, 0 to 95% by weight of total solids of the silica dispersion hydrophilic polyurethane A resin composition used in the ink-receiving layer formed, preferably in the range of 10 to 90 wt% is there.

Further, if necessary, a thickener in addition to the silica dispersion hydrophilic polyurethane A resin composition, release agents, penetrating agents, wetting agents, thermal gelling agents, sizing agents, antifoaming agents, Foaming agent, colorant, fluorescent whitening agent, ultraviolet absorber, antioxidant, quencher agent, preservative, antistatic agent, crosslinking agent, dispersant, lubricant, plasticizer, pH adjuster, fluidity improver, Various auxiliary agents such as a solidification accelerator and a water-proofing agent can be appropriately blended.

Silica Dispersion hydrophilic polyurethane A resin composition used to form the ink-receiving layer in the present invention, it is preferred to use a solution of the hydrophilic polyurethane A resin synthesized in the solvent, were synthesized in a solventless used to dissolve the hydrophilic polyurethane a resin in a solvent in the case. If component added is solvent-soluble as required, it may be dissolved directly added to a solution of the above hydrophilic polyurethane A resin composition, or may be added in advance dissolved in a solvent. Further adding an additive component insoluble, a solution of silica dispersion hydrophilic polyurethane A resin composition usually solids is prepared in the coating solution of about 5 to 15 wt%.

  The prepared coating solution is applied to 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 and the like. Further, after application, the sheet is finished by using a calendar such as a machine calendar, a super calendar, or a soft calendar to obtain an ink jet recording sheet.

The thickness of the ink receiving layer formed, the thickness to be 5 to 100 g / m ² approximately by dry weight of the coating solution is preferably, more preferably 10 to 50 g / m ² approximately. If the thickness of the ink receiving layer is less than 5 g / m ² , the ink absorption by the ink receiving layer is insufficient, and if the thickness exceeds 100 g / m ² , the obtained effect becomes saturated and uneconomical, and the ink receiving Layer breakage, curling, etc. are likely to occur.

  Next, the present invention will be described in more detail with reference examples, examples and comparative examples. In addition, the part or% in a sentence is a mass reference | standard.

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 reduced in pressure at 70 ° C. while stirring. Dehydration was performed.
After the theoretical amount of water was distilled off, the temperature was raised to 120 ° C. and water was 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 had a hydroxyl value of 76 mgKOH / g, a moisture content of 0.15%, was transparent at 80 ° C., and had a viscosity of 450 dPa · s.

Reference example 2
100 parts of polyethylene glycol (molecular weight 590) and silica water sol (silica average particle size 200-230 nm, solid content 30%) 333 parts were sufficiently mixed, and the resulting mixture was dehydrated under reduced pressure at 70 ° C. while stirring. .
After the theoretical amount of water was distilled off, the temperature was raised to 120 ° C. and water was 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 had a hydroxyl value of 95 mgKOH / g, a moisture content of 0.12%, and softened at 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 to 30 nm, solid content 40%) are sufficiently mixed, and the resulting mixture is obtained. While stirring, dehydration was performed 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 removed under reduced pressure of 133.3 Pa or less to obtain a white solid polyamine (C) having a silica content of 90%. This polyamine was softened at an amine equivalent of 30 g / mol, a moisture content of 0.20%, and 130 ° C.

Reference example 4
(Production of silica-dispersed polyurethane resin composition)
50 parts of polyethylene glycol (molecular weight 2,040), 100 parts of polyol (A) of Reference Example 1, 20 parts of N-methyldiethanolamine and 5 parts of diethylene glycol are mixed in a mixed solvent of 200 parts of methyl ethyl ketone and 200 parts of dimethylformamide. The solution which melt | dissolved and melt | dissolved 80 parts hydrogenated MDI in 200 parts methyl ethyl ketone was dripped gradually, stirring well at 60 degreeC. After completion of the dropwise addition, the mixture was reacted at 80 ° C. for 8 hours, and then 420 parts of dimethylformamide was added to obtain a silica-dispersed polyurethane resin composition solution.

This solution has a solid content of 20%, a viscosity of 332 dPa · s (25 ° C.), and measured by GPC of a polyurethane resin. The weight average molecular weight in terms of standard polystyrene (the same applies to the following examples) is 53,000. The tertiary amino group content in the resin was 0.52 eq / kg, and the silica content was 11.7%.
The film formed from this resin composition solution was transparent, the breaking strength was 25.7 MPa, the breaking elongation was 50%, and the softening point was 165 ° C.

Reference Example 5
(Production of silica-dispersed polyurethane-polyurea resin composition)
30 parts of polyethylene oxide diamine (Jefamine ED; molecular weight 2,000), 120 parts of polyol (B) of Reference Example 2, and N, N-dimethyl-N ′, N′-dihydroxyethyl-1,3-diaminopropane 25 A solution of 65 parts of hydrogenated MDI dissolved in 100 parts of methyl ethyl ketone was gradually added dropwise to 100 parts of methyl ethyl ketone and 200 parts of dimethylformamide mixed solvent. After completion of the dropwise addition, the mixture was reacted at 80 ° C. for 8 hours, and then 560 parts of dimethylformamide was added to obtain a silica-dispersed polyurethane-polyurea resin composition solution.

This solution had a solid content of 20% and a viscosity of 35 dPa · s (25 ° C.). The weight average molecular weight of the polyurethane-polyurea resin was 48,000, the tertiary amino group content in the resin was 1.08 eq / kg, and the silica content was 24%.
The film formed from this resin composition solution was transparent, had a breaking strength of 21.5 MPa, a breaking elongation of 20%, and a softening point of 185 ° C.

Reference Example 6
(Preparation of silica-dispersed polyurethane A resin composition)
Polyethylene oxide diamine (Jephamine ED; molecular weight 2,000) 5 parts, polyamine (C) 145 parts of Reference Example 3 and 3 parts of methyliminobispropylamine are dissolved in 250 parts of dimethylformamide, and the internal temperature is adjusted to 0- A solution prepared by dissolving 7 parts of hydrogenated MDI in 100 parts of dimethylformamide was gradually added dropwise and reacted while stirring at 5 ° C. After completion of the dropwise addition, to raise the internal temperature gradually to obtain After further 5 hours at reaching 50 ° C., was added a dimethylformamide 310 parts of the silica dispersion polyurethane A resin composition of the present invention solution.

The solution is 20% solids, a viscosity of 60dPa · s (25 ℃), weight average molecular weight of polyurethane A resin was 35,000, the content of the tertiary amino groups in the resin is 0. The content of silica was 45 eq / kg and 79%.
The film formed from this resin composition solution was slightly translucent and porous, had a breaking strength of 3.2 MPa, a breaking elongation of 3%, and a softening point of 220 ° C.

Reference Example 7
A polyurethane resin solution was obtained by the same material and formulation as in Reference Example 4 except that N-methyldiethanolamine was not used and a polyol excluding silica of polyol (A) was used.
This solution had a solid content of 20%, a viscosity of 50 dPa · s (25 ° C.), and the weight-average molecular weight of the polyurethane resin was 68,000.
The film formed from this resin solution had a breaking strength of 35.0 MPa, a breaking elongation of 450%, and a softening point of 103 ° C.

Reference Example 8
N, N-dimethyl-N ′, N′-dihydroxyethyl-1,3-diaminopropane is the same material and formulation as in Reference Example 5 except that the polyol (B) except for the silica is used. Thus, a polyurethane-polyurea resin solution was obtained.
This solution had a solid content of 20%, a viscosity of 40 dPa · s (25 ° C.), and the weight-average molecular weight of the polyurethane-polyurea resin was 55,000.
The film formed from this resin solution had a breaking strength of 25.3 MPa, a breaking elongation of 400%, and a softening point of 95 ° C.

Reference Example 9
Without the use of methyl iminobispropylamine, also addition to using a polyamine other than silica polyamine (C) is to obtain a solution of polyurethane A resin according to the formulation the same material as in Reference Example 6.
The solution is 20% solids, a viscosity of 25dPa · s (25 ℃), weight average molecular weight of polyurethane A resin was 32,000.
The film formed from this resin solution had a breaking strength of 22.7 MPa, a breaking elongation of 350%, and a softening point of 115 ° C.

Reference Examples 10-12
Although each silica water sol or silica methanol sol of Reference Examples 1 to 3 was added to each of the resin solutions of Reference Examples 7 to 9 with stirring, particles were precipitated and the solution became opaque.

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

Example 1
The solution to the fine paper having a basis weight of 35 g / m ² of silica dispersion hydrophilic polyurethane A resin composition obtained in Reference Example 6, an air knife coater, was coated so that the thickness after drying became 25 [mu] m, the ink A receiving layer was formed to provide an ink jet recording sheet of the present invention.

Comparative Examples 1-7
The resin solutions obtained in Reference Examples 7 to 13 were coated on 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, and an ink receiving layer was formed. It was set as the inkjet recording sheet of the comparative example.

[Evaluation of inkjet recording sheet]
For the eight types of ink jet recording sheets obtained as described above, four colors of yellow, magenta, cyan, and black are used in an ink jet printer (PM-800C manufactured by Seiko Epson Corporation) that records and records with a water-soluble dye ink. The following items were evaluated.
(1) Blocking property An untreated PET film was stacked on the resin-coated surface, and the blocking property was evaluated after standing for one day at a load of 0.29 MPa and a temperature of 40 ° C. The results are displayed as follows:
The results are displayed as follows.
○: No blocking property Δ: Some blocking property ×: Blocking property (2) Transparency The cloudiness of the resin coating surface was visually determined. The results are displayed as follows:
○: Completely transparent △: Slightly cloudy ×: Completely opaque

(3) Colored sharpness After color printing with an inkjet printer, the color sharpness of the obtained color image was visually observed. The results are displayed as follows:
○: Clear and clear △: Slightly blurred and slightly unclear (4) Ink drying characteristics After color printing with an inkjet printer, press the filter paper for 5 seconds at a load of 50 g / m ² until the ink does not transfer to the filter paper. Time was measured.
(5) Water resistance of printed image After color printing with an ink jet printer, the recording sheet is immersed in water (20 ° C, 1 hour), and then visually observed for bleeding and color change of the recorded image when dried at room temperature. did. The results are displayed as follows:
○: No change Δ: Change is observed in ink and film ×: Ink can be removed considerably or the entire film can be taken Table 1 shows the above evaluation results.

Having an ink-receiving layer hydrophilic segment and composition comprising a hydrophilic polyurethane A resin and particulate silica having a tertiary amino group (Silica Dispersion hydrophilic polyurethane A resin composition) is configured as a resin component of the present invention The ink jet recording sheet is excellent in ink drying property and color developability, gives a stable and high-quality printed image, and is further excellent in transparency, blocking resistance and water resistance of the ink receiving layer and the printed image.

Claims (4)

In a method for producing an ink jet 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 polyamine, and at least one active hydrogen. When synthesizing a hydrophilic polyurea resin having a hydrophilic segment and a tertiary amino group by reacting a containing group with a compound having at least one tertiary amino group in the same molecule, high molecular weight hydrophilicity Formed using a silica-dispersed hydrophilic polyurea resin composition using a mixture of a high molecular weight hydrophilic polyamine and a silica sol as at least a part of the hydrophilic polyamine, and the mixture comprises a high molecular weight hydrophilic polyamine and a silica sol. and wherein the mixture of is obtained by removing the dispersion solvent silica sol Method for manufacturing an ink jet recording sheet that.   2. The method for producing an ink jet recording sheet according to claim 1, wherein the content of silica in the mixture is 5 to 95% by mass in the produced silica-dispersed hydrophilic polyurea resin composition.   The method for producing an ink jet recording sheet according to claim 1, wherein the fine particle silica has an average particle diameter of 1 to 300 nm.   2. The recording sheet for ink jet recording according to claim 1, wherein the content of the hydrophilic segment and the tertiary amino group in the hydrophilic polyurea resin is 30 to 80 mass% and 0.1 to 50 eq / kg, respectively. Method.