JP2002067491A - Ink jet recording sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording sheet which shows the outstanding water and light resistance of a printed image and printing density and also high whiteness, and contrasting properties and sharpness of the printed image and further, the availability of a high quality level image. SOLUTION: In the ink jet recording sheet with an ink receiving layer composed mainly of a white pigment and a cationic ink fixing agent, formed on a sheetlike support, the ink receiving layer contains an organic coloring pigment and a fluorescent brightener selected from among a fluorescent-86, a fluorescent-90 or a 4,4'-bis[2-sodium sulfanyl-4-di(hydroxy ethyl)amino-1,3,5-triazinyl-(6)- amino]stilbene-2,2'-sodium disulfonate as a fluorescent brightener.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording sheet used for an ink jet recording system using an aqueous ink.
More specifically, the present invention relates to an ink jet recording sheet capable of obtaining excellent blank paper surface quality and a high-quality printed image.

[0002]

2. Description of the Related Art Ink jet recording is a method in which minute droplets of ink are caused to fly according to various operating principles and adhere to a recording sheet such as paper to record images and characters. It has features such as easy multi-coloring, great flexibility in recording patterns, and no need for development and fixing, and is rapidly spreading as a recording device for various graphic color images including Chinese characters. Further, the image formed by the multi-color ink jet recording method can obtain a recording comparable to the multi-color printing by the plate making method or the printing by the color photographic method,
In applications where the number of copies required is small, it is cheaper than photographic technology, and is being widely applied to the field of full-color image recording.

[0003] In this ink jet recording system, aqueous ink is usually used, and the recording sheet needs to be quickly absorbed by the attached ink. That is, in the case of a color ink jet process using a plurality of ink nozzles, if the previously ejected ink microdroplets are not absorbed by the sheet before the next ink microdroplet is jetted, the image or character will blur and become sharp. Therefore, an ink jet recording sheet having a high ink absorption is required.

In order to obtain a recording sheet having excellent ink absorbency and excellent print density, the dye in the ink is stopped on the sheet surface, and only a vehicle such as water or a solvent is allowed to penetrate into the sheet-like support. Is desired. From such a viewpoint, the density and air permeability of the sheet-like support (Japanese Patent Application Laid-Open No. 52-743)
No. 40) and size (Japanese Patent Application Laid-Open No. 1-280579) are used after adjustment. However, these adjustments alone are not sufficient, and the sharpness of the printed image is poor, so that the printed image is inferior. It has been proposed to provide an ink receiving layer containing a white pigment as a main component (JP-A-1-95092).
If water or the like adheres to the printing portion, these recording sheets in the proposal have a drawback that characters are blurred due to re-elution and misread, or the printed image is discolored by sunlight, fluorescent light or the like.

[0005]

Therefore, in order to improve the weather resistance of a printed image, a cationic ink fixing agent (Japanese Patent Application Laid-Open No.
No. 198186, JP-A-1-9776). Further, there is a strong demand from the market to obtain a high-quality image by further improving whiteness, contrast (contrast) and sharpness of an image, and use of a fluorescent whitening agent (Japanese Patent Application Laid-Open No. No. 68923) has been proposed, and the effect is recognized but insufficient. Further, when a small amount of organic coloring pigment is mixed in order to improve the contrast and sharpness of the image, the organic coloring pigment precipitates and appears as fine particles on the coated surface, which is a practical problem.

[0006] Accordingly, an object of the present invention is to provide a printed image having water resistance.
An object of the present invention is to provide an ink jet recording sheet that is excellent in light resistance and printing density, has high whiteness, is excellent in contrast and sharpness of a printed image, and can obtain a high-quality image.

[0007]

As a result of extensive studies and experiments, the present inventor has found that an ink jet recording apparatus comprising a sheet-like support provided with an ink receiving layer containing a white pigment and a cationic ink fixing agent as main components. The present invention has been made based on the finding that the object can be achieved when the ink receiving layer contains an organic coloring pigment and a specific fluorescent whitening agent in the sheet. In the present invention, the organic color pigment is preferably a pigment blue pigment or a pigment violet pigment, and the ink receiving layer preferably contains an ethylene vinyl acetate copolymer.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As the sheet-like support used in the present invention, general acidic paper and neutral paper for coated paper are appropriately used. The sheet-shaped support is composed mainly of wood pulp and, if necessary, pigment. Wood pulp is a variety of chemical pulp, mechanical pulp, recycled pulp, etc., and these pulp are beaten with a beating machine to maintain suitability for ink-jet recording such as suitability for paper making, coating, ink absorption and printing surface quality. Adjust the degree (freeness). The degree of beating of the pulp varies depending on the type of pulp, and is not particularly limited, but generally 300 to 500 ml [Canadian Standard Freeness (hereinafter referred to as CSF): JISP-8121] is preferred.

[0009] A sizing agent, a paper strength enhancer, a retention enhancer, and the like are added as auxiliaries, and a water-soluble polymer such as starch is coated and impregnated in a size press process of a paper machine to obtain surface strength, sizing degree, etc. To adjust. If the surface strength is low, the adhesive strength with the coating layer is low, and the printer is stained by powder dropping, which causes trouble. The basis weight of the sheet-like support to be formed is 40 to 350 g / m ² , and the sizing degree varies depending on the basis weight, but the sizing degree is in the range of 1 to 250 seconds. Occasionally, there is a problem in operation due to paper breakage, wrinkles, etc., and if the size is high, the absorbency is poor and bleeding occurs.

As the white pigment for the ink receiving layer used in the present invention, for example, talc, kaolin, calcined kaolin, acid clay, activated clay, calcium carbonate, carbonate, etc. magnesium,
Calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, calcium silicate, magnesium silicate, aluminum hydroxide, synthetic amorphous silica, colloidal silica, colloidal alumina, water Inorganic white pigments such as aluminum oxide, alumina, lithopone, zeolite and hydrohaloysite; plastic pigments such as polyethylene, polystyrene and polyacrylate; organic white pigments such as urea resin and melamine resin; Although mixed and used as described above, synthetic amorphous silica is particularly preferred. The mixing ratio is 1 to 100 parts by weight of pulp.
-30 parts by weight. Preferably it is 5 to 20 parts by weight.

Examples of the dispersant for the white pigment include sodium pyrophosphate, sodium hexametaphosphate, sodium tripolyphosphate, sodium polyacrylate, sodium hydroxide, monoethanolamine and the like.
A mixture of more than one kind is used, and particularly preferred are sodium polyacrylate, sodium hydroxide and sodium silicate.

The cationic ink fixing agent used in the present invention includes, for example, organic acid salts of polyethyleneimine such as acetic acid, benzoic acid and p-trienesulfonic acid, copolymers of dimethyldiallylammonium chloride and acrylamide, and (meth) Polymer of quaternary ammonium compound of alkyl acrylate or alkyl (meth) acrylate or copolymer containing 50 mol% or more of quaternary ammonium compound, acrylamide / acrylonitrile / N-vinylacrylamidine hydrochloride / N-vinyl Acrylamide / vinylamine hydrochloride / N-vinylformaldehyde copolymer, dimethylamine / epichlorohydrin polycondensate, polyethylene polyamine / dimethylamine / epichlorohydrin polycondensate, acrylamide / diallylamine copolymer, etc. Acrylamide / acrylonitrile / N-vinylacrylamidine hydrochloride / N-vinylacrylamide / vinylamine hydrochloride / N-vinylformaldehyde copolymer; dimethylamine Epichlorohydrin polycondensate, polyethylene polyamine / dimethylamine / epichlorohydrin polycondensate, and acrylamide / diallylamine copolymer.

The mixing ratio of the cationic ink fixing agent used in the present invention to the ink-receiving layer is from 5 to 60 parts by weight, preferably from 15 to 35 parts by weight, based on 100 parts by weight of the white pigment. is there. If the amount is less than 5 parts by weight, the ink fixing effect is small, and the water resistance and light resistance of the printed image are inferior. If the amount exceeds 60 parts by weight, the print density is reduced. The order of addition of the cationic ink fixing agent used in the present invention when preparing the coating liquid for the ink receiving layer is not particularly limited, but is preferably added to the white pigment dispersion. The viscosity immediately after the addition is very high, and aggregation is liable to occur. However, if added quickly, the increase in viscosity can be relatively suppressed.

The organic coloring pigment used in the present invention includes:
For example, there may be mentioned pigment yellow pigments, pigment orange pigments, pigment green pigments, pigment blue pigments, pigment violet pigments, pigment brown pigments, pigment black pigments, pigment red pigments, and one or two kinds. These are used as a mixture, but pigment blue pigments and pigment violet pigments are preferred. Pigment Blue pigments, specifically, Pigment Blue-1, -2,-
15, -16, -17, -18, -19, -22, -2
4, -25, -29, -57, -60, -61, -63
And the like, and as the pigment violet pigment, pigment violet-1, -2, -3, -5, -1
9, -23, -27, -28, -29, -31, -3
2, -33, -34, -36, -37, -38, -39
And so on.

The mixing ratio of the organic color pigment used in the present invention to the ink receiving layer is not particularly limited, but it is effective even in a very small amount. 1 part by weight, preferably 0.01 part by weight.
０．０５0.05 parts by weight. If the amount is less than 0.001 part by weight or exceeds 0.1 part by weight, the contrast and sharpness of the printed image are poor.

The fluorescent whitening agent used in the present invention includes fluorescent-86 or fluorescent-90,
Alternatively, 4,4′-bis [2-sodium sulfanyl-4
-Di (hydroxyethyl) amino-1,3,5-triazinyl- (6) -amino] stilbene-2,2'-disulfonate is preferable, and the mixing ratio to the ink receiving layer is based on 100 parts by weight of the white pigment. On the other hand, in weight solids,
It is 0.01 to 10 parts by weight, preferably 0.5 to 5 parts by weight. If the amount is less than 0.01 part by weight, the effect of improving the whiteness is small, and if it exceeds 10 parts by weight, the print density decreases.

Examples of the adhesive used in the present invention include natural or semi-synthetic water-soluble polymers such as starch, casein, soybean protein, gelatin, carboxymethylcellulose and hydroxyethylcellulose; polyvinyl alcohol,
Water-soluble polymers such as silanol-modified polyvinyl alcohol and derivatives thereof; conjugated diene-based polymer latex such as styrene-butadiene copolymer and methyl methacrylate butadiene copolymer; and vinyl-based polymer latex such as ethylene-vinyl acetate copolymer. And one kind or a mixture of two or more kinds is used. Preferably, polyvinyl alcohol and silanol-modified polyvinyl alcohol are used. However, when a large amount of polyvinyl alcohol is used, the viscosity of the coating liquid increases, so that it is preferable to mix latex. The latex used in the present invention is particularly preferably an ethylene-vinyl acetate copolymer latex which has a low viscosity even when mixed, has an adhesive force, has a small decrease in print density in terms of quality, and is excellent in image clarity.

The mixing ratio of the polyvinyl alcohol to the ink receiving layer used in the present invention depends on the degree of polymerization and the degree of saponification of the polyvinyl alcohol, but is not particularly limited. In 5
It is 50 parts by weight, preferably 20 to 40 parts by weight. If the amount is less than 5 parts by weight, the adhesive strength is inferior, and if it exceeds 50 parts by weight, the viscosity of the coating liquid increases and the print image density decreases. The mixing ratio of the ethylene-vinyl acetate copolymer latex to the ink receiving layer used in the present invention is not particularly limited depending on the amount of polyvinyl alcohol added, but is 5 to 30 parts by weight in terms of solid weight per 100 parts by weight of white pigment. And preferably 10 to 20 parts by weight.

Further, in the present invention, if necessary, a reinforced rosin sizing agent, a petroleum resin sizing agent, an emulsion sizing agent, a reactive sizing agent such as alkenyl succinic anhydride, a self-fixing cationic resin sizing agent, a wax emulsion, silicone Dot controlling agents such as fatty acid soap, sodium dialkylsulfosuccinate, sodium dodecylbenzenesulfonate, polyoxyethylene alkyl ether; wetting agents; preservatives such as methyl benzimidazolylcarbamate and allylmethanol mono (poly) hemifomal; Add to form a coating liquid for the ink receiving layer,
With a coating method such as a blade coater, an air knife coater, a curtain coater, a bar coater, a gravure coater, and a roll coater, the coating amount on the sheet-like support is 3 to 3
An ink receiving layer is provided by coating and drying so as to be 0 g / m ² (dry weight solid content) to obtain an ink jet recording sheet. Although the ink receiving layer of the present invention has a highly smooth surface quality, it is preferable that the ink receiving layer is processed with a smoothing device such as a super calender or a soft calender in order to obtain a higher quality image.

The ink-receiving layer coating liquid of the present invention is applied on both sides of a sheet-like support to provide an ink-receiving layer, thereby obtaining a double-sided ink jet recording sheet capable of printing on both sides. Further, an intermediate layer is formed on the sheet-like support, and an ink receiving layer is formed on the intermediate layer by laminating to obtain a laminated ink jet recording sheet. Alternatively, the ink receiving layer can be mirror-finished to obtain an ink jet recording sheet having a mirror surface.

The support of the ink jet recording sheet of the present invention is preferably paper, but is not limited thereto.
In addition to paper, a synthetic resin-coated paper in which both surfaces of a sheet-like support are coated with a polyolefin resin, or a sheet-like support such as a film may be used. Further, a pressure-sensitive adhesive layer or a label adhesive layer can be provided on the back surface of the ink jet recording sheet of the present invention.

[0022]

The preferred embodiments of the present invention and the excellent effects thereof will be specifically described below with reference to the most typical examples. In the following, all parts are parts by weight, and all percentages are by weight.
It is.

[Preparation of Support] LBKP (CSF 350 ml) 90 parts NBKP (CSF 350 ml) 10 parts Talc 15 parts Rosin size emulsion 2 parts Sulfuric acid band 5 parts Amphoteric starch 1.5 parts

A 1% slurry of the above composition was formed into a paper by a TAPPI standard machine, and the obtained wet paper was dried at 5 kg / cm.
² and then dried at 90 ° C. for 2 minutes. This was subjected to size press with a 6% oxidized starch aqueous solution (manufactured by Nippon Shokuhin Kako Co., Ltd .: MS3800) so as to have a weight of 1.5 g / m ² (dry weight solids) on both sides, and a support having a basis weight of 80 g / m ² was obtained. Obtained.

[Preparation of Inkjet Recording Sheet] Example 1 2.8 parts of 25% aqueous sodium silicate solution Amorphous synthetic silica powder (Mizukasil P78A manufactured by Mizusawa Chemical Industries) 100 parts Silica dispersed water 397 parts 5% Pigment Blue- 15 aqueous dispersion 0.24 parts 5% Pigment Violet-23 aqueous dispersion 0.4 parts 20% fluorescein-86 aqueous solution 10 parts acrylamide / acrylonitrile / N-vinylacrylamidine hydrochloride / N-vinylacrylamide / vinylamine hydrochloride 80 parts of a 30% aqueous solution of a salt / N-vinylformaldehyde copolymer 80 parts of a 10% aqueous polyvinyl alcohol solution (manufactured by Kuraray: PVA-117, degree of polymerization 1700, degree of saponification 98.5 mol%) 300 parts

The above composition was used as a coating liquid for an ink receiving layer.
Next, the coating liquid was applied to the support having a basis weight of 80 g / m ² obtained above using an air knife coater so that the coating amount was 8 g / m ² (dry weight solid content), and then dried. A calendar treatment was performed to obtain an ink jet recording sheet.

Example 2 A 20% aqueous solution of Fluorescent-86 of Example 1 was
An ink jet recording sheet was obtained in the same manner except that the same amount was replaced with an aqueous solution of Fluorescent-90.

Example 3 The 20% aqueous fluorescein-86 solution of Example 1 was
Equivalent amount to aqueous sodium 4,4'-bis [2-sodiumsulfanyl-4-di (hydroxyethyl) amino-1,3,5-triazinyl- (6) -amino] stilbene-2,2'-disulfonate An ink jet recording sheet was obtained in the same manner as above except for replacing.

Example 4 [Preparation of Ink-Jet Recording Sheet] 2.8 parts of 25% aqueous sodium silicate solution Amorphous synthetic silica powder (Mizukasil P78A manufactured by Mizusawa Chemical Industries) 100 parts Silica dispersed water 397 parts 5% Pigment Blue- 15 aqueous dispersion 0.24 part 5% Pigment Violet-23 aqueous dispersion 0.4 part 20% fluorescein-86 aqueous solution 10 parts 50% aqueous solution of polyethylene polyamine / dimethylamine / epichlorohydrin polycondensate 40 parts 10% silanol-modified polyvinyl alcohol aqueous solution (Kuraray: R-1130, degree of polymerization: 1700, degree of saponification: 98.5 mol%) 200 parts 55% ethylene vinyl acetate copolymer latex (Sumitomo Chemical: Sumikaflex S-577) ) 18.2 parts Added water 125 parts

The above composition was used as a coating liquid for an ink receiving layer.
Next, the coating liquid is applied to a support having a basis weight of 80 g / m ² by an air knife coater so that the coating amount becomes 8 g / m ² (dry weight solid content), and then subjected to a super calender treatment. Thus, an ink jet recording sheet was obtained.

EXAMPLE 5 20% aqueous solution of Fluorescent-86 of Example 4 was
An ink jet recording sheet was obtained in the same manner except that the same amount was replaced with an aqueous solution of Fluorescent-90.

Example 6 The 20% aqueous fluorescein-86 solution of Example 4 was
Equivalent amount to aqueous sodium 4,4'-bis [2-sodiumsulfanyl-4-di (hydroxyethyl) amino-1,3,5-triazinyl- (6) -amino] stilbene-2,2'-disulfonate An ink jet recording sheet was obtained in the same manner as above except for replacing.

Example 7 A 55% ethylene-vinyl acetate copolymer latex (Sumikaflex S-478) was replaced with a 55% ethylene-vinyl acetate copolymer latex (Sumikaflex S-400, manufactured by Sumitomo Chemical Co., Ltd.). An ink jet recording sheet was obtained in the same manner except that the same amount was replaced.

Comparative Example 1 A 20% aqueous solution of Fluorescent-86 of Example 1 was added to 20%
An ink jet recording sheet was obtained in the same manner except that the same amount was replaced with an aqueous solution of Fluorescent-85.

Comparative Example 2 The 20% aqueous solution of fluorescen-86 of Example 1 was
4,4'-bis [2-methoxyethylamino-1,3,3
5-triazinyl- (6) -amino] stilbene-2,
An ink jet recording sheet was obtained in the same manner except that the same amount of 2'-disulfonic acid aqueous solution was used.

Comparative Example 3 A 20% aqueous solution of fluorescein-86 of Example 1 was added to 20%
4,4'-bis [2-methoxy-4- (2-hydroxypropyl) amino-1,3,5-triazinyl- (6)
[Amino] stilbene-2,2'-disulfonic acid aqueous solution was replaced by the same amount to obtain an ink jet recording sheet.

The ink receiving layer coating liquids and ink jet recording sheets obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were measured and evaluated by the following methods.

Evaluation Method << Confirmation of Organic Colored Pigment Agglomerate on the Surface of Coating Liquid for Ink-Receiving Layer >> One day after the coating liquid was weakly stirred, the surface of the coating liquid was observed and the organic colored pigment was agglomerated. The presence of suspended matter was confirmed. << White paper surface quality >> The coated surface was visually observed to determine the presence or absence of organic color pigment fine aggregates. ：: There is no aggregate. X: There is a flocculated substance. << White paper hue >> L is measured on white paper with a colorimeter (Nippon Denshoku)
The a and b values were measured. The larger the value of the L value is, the higher the whiteness is. The + of the a value is reddish, the-is greenish, the + of the b value is yellowish,-
Indicates bluish. When the blue and violet organic pigments used in the present invention agglomerate, the positive value of the a value decreases and the negative value of the b value decreases, and the contrast and sharpness of the image decrease. << Print Density >> Inkjet Printer PM700C
(Seiko Epson), and after standing for 48 hours, the optical density of the black solid image portion was measured using a Macbeth densitometer RD9.
Measured at 18. The larger the value, the higher the concentration and the better.

<< Image Water Resistance >> An ink jet printer MJ5000C (manufactured by Seiko Epson) uses a single color of black, cyan, magenta, yellow, cyan + magenta,
A cyan + yellow heavy color was printed, and after standing for 48 hours, the printed portion was immersed for 10 minutes and air-dried, and the degree of print bleeding was visually determined. ：: Excellent without discoloration or bleeding. Δ: Slightly blurred. << Image lightfastness >> Inkjet printer MJ5000
C, after printing for 48 hours, irradiating a solid magenta image area which is easily faded with a 5000 Lx fluorescent lamp for 120 hours, and then measuring the optical density of the solid image area with a Macbeth densitometer RD9
The light resistance (%) was determined by the following equation. The numerical value indicates that the larger the value, the better. Lightfastness (%) = optical density after irradiation / optical density before irradiation << Contrast / Clarity of Image >> Printed with an inkjet printer MJ800C (manufactured by Seiko Epson), left for 48 hours, and then left black, cyan, The contrast and sharpness of the white characters in each of the monochromatic colors of magenta and yellow, cyan + magenta and cyan + yellow were visually determined. A: Particularly excellent. ：: Excellent. X: Poor.

The above evaluation results are summarized in Tables 1 and 2.

[0041]

[Table 1]

[0042]

[Table 2] The overall evaluation is ○: excellent, ×: poor.

[0043]

As is clear from the above examples, in an ink jet recording sheet having a sheet-like support provided with an ink receiving layer containing a white pigment and a cationic ink fixing agent as main components, the ink receiving layer is organically colored. By containing a pigment and a specific fluorescent whitening agent, printed images have excellent water resistance, light resistance and printing density, high whiteness, excellent contrast and sharpness of printed images, and high quality images can be obtained. Ink jet recording sheet can be provided.

Claims (3)

[Claims] 1. An ink jet recording sheet comprising a sheet-like support provided with an ink receiving layer containing a white pigment and a cationic ink fixing agent as main components, wherein the ink receiving layer comprises an organic coloring pigment, Fluorescent-86, Fluorescent Rescent-90 or 4,4′-bis [2-sodiumsulfanyl-4-di (hydroxyethyl) amino-1,
3,5-Triazinyl- (6) -amino] stilbene-
An ink jet recording sheet comprising at least one fluorescent whitening agent selected from sodium 2,2'-disulfonate. 2. The ink jet recording sheet according to claim 1, wherein the organic coloring pigment is a pigment blue pigment or a pigment violet pigment. 3. The ink jet recording sheet according to claim 1, wherein the ink receiving layer contains an ethylene vinyl acetate copolymer.