JPH1111006A - Ink jet recording sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the degree of surface waviness after recording an image by providing an ink receiving layer on a base sheet composed essentially of natural pulp having a sheet density above a specific value. SOLUTION: The ink jet recording sheet is formed of a paper composed essentially of natural pulp having a sheet density above 1.01 g/cm<3> as a base sheet and an ink receptive layer coated at least on one of the faces of the base sheet. The base sheet is of a sheet density of 1.01 g/cm<3> or more but is preferably of a sheet density above 1.03 g/cm<3> and further, is more preferably of a sheet density above 1.05 g/cm<3> . The ink receptive layer is made qualitatively uniform by providing the ink receptive layer on the base sheet, and the ink jet recording sheet is obtained which shows superior development properties and clarity and is almost free from the surface waviness of the sheet even after drying a recorded image. The reason is that when the base sheet is made so that its sheet density is 1.01 g/cm<3> or more, the difference in the locally generated unevennesses of the surface is extremely insignificant due to the almost non-presence of a gap between the pulps.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording sheet, and more particularly, to a method for forming a high quality image by an ink jet method using an aqueous ink provided with an ink receiving layer. The present invention relates to an ink jet recording sheet having excellent characteristics with little waving.

[0002]

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

As recording sheets used in the ink jet recording system, efforts have been made in terms of apparatuses and ink compositions in order to use high-quality paper and coated paper used for ordinary printing and writing. However, as the performance of the inkjet recording apparatus has been improved and the use thereof has been expanded, such as by increasing the speed and increasing the definition of the apparatus or by increasing the color, the recording sheet has been required to have higher properties. That is, the recording sheet has a high density of print dots, a bright and vivid color tone, quick absorption of ink, so that ink does not flow or bleed even when print dots overlap, That the diffusion in the direction is uniform and not excessively large, and that the periphery is smooth and not blurred, and that there is no change in image quality over time and the environment, for example, it is excellent in light resistance, water resistance, ozone resistance, etc. Required.

[0004] In response to such demands, several proposals have hitherto been made. In order to improve the ink absorption and prevent the diffusion of print dots, a method of providing an ink receiving layer on a support (JP-A-52-9074, JP-A-58-72495, etc.) Focusing on the fact that the distribution state of the dye component affects the color and sharpness, a method using a specific agent that adsorbs the dye component (JP-A-55-144)
No. 172). In order to improve light resistance, water resistance, and ozone resistance, a basic oligomer may be contained (Japanese Patent Application Laid-Open No. 60-11389), and polyvinylamine may be added to the coating layer in or on the substrate. The use of a polymer (JP-A-64-8085) is disclosed.

[0005] However, while the demands for these characteristics are gradually becoming higher and stricter, an ink jet recording apparatus is inexpensive and has excellent image reproducibility such as sharpness and color reproducibility and color reproducibility at a personal computer level. Because it can be easily obtained, the inkjet recording device has changed from a special recording device used for a specific person to a general-purpose recording device, and the image is comparable to printed matter and photograph Because of such quality, it is also being used as a postcard and a printer for digital photography. In this case, the texture and feel of postcards and photographic prints are required. Further, in such applications, the amount of ink to be ejected is large, and the ink solvent that reaches the base paper causes the printed sheet to undulate, resulting in a problem of poor appearance. Therefore, at present, securing these characteristics is a necessary condition of the inkjet recording apparatus and the inkjet recording sheet.

[0006] Further, with the diversification of uses, it is used for posters and POP arts, or provided with an adhesive layer on the back surface, and used for price display labels, product display (bar code) labels, quality display labels, For label applications such as weighing display labels and advertising labels (stickers), it adheres well to a wide range of adherends, and because it is easy to apply, heat-sensitive properties, magnetic properties, Since it becomes possible to add a composite function by laminating a sheet or the like having suitability for offset printing, the application to tickets, commuter passes, various cards, and the like is expanding.

[0007] Inks are classified into a solvent type and an aqueous type. However, there are many aqueous inks in terms of price, safety, ease of handling, and the like. Important issues include prevention of ink bleeding that occurs when water adheres, and improvement of sheet waving due to water reaching the base paper. However, at present it has not been sufficiently addressed to this problem, and in a recording sheet using a support mainly composed of wood pulp having a function as an ink absorber as a medium of an inkjet recording sheet,
It is a more important and early problem to be solved.

[0008] The form of the ink jet recording sheet is a so-called plain paper type typified by so-called high-quality paper or bond paper, and an ink-receiving layer provided on a support such as paper such as high-quality paper, synthetic paper, or synthetic resin film. Coating type. In the coating type ink jet recording sheet, since the various characteristics of the applied ink receiving layer directly affect the printing quality, regarding the absorption, the selection of the specific surface area and shape of the pigment, the color saturation and the color reproducibility, etc. Various studies have been made on the transparency and refractive index of pigments, on the image quality, on the coating layer structure and surface shape, and on the improvement of paper waving and the like, on the underwater elongation and on the coating method.

[0009]

SUMMARY OF THE INVENTION According to the present invention, in an ink-jet recording system using an aqueous ink, a high-quality ink-jet image excellent in color development and sharpness of an image can be obtained, and the sheet has little waving after image recording. It is an object of the present invention to provide a good-looking inkjet recording sheet.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to achieve the above-described printing quality which is good and the performance of reducing the waving of the recording sheet after image recording, and
The present invention was found to produce an ink jet recording sheet with improved conventional defects by producing a base paper having a higher density than ordinary coated base paper or high-quality paper and providing an ink receiving layer thereon. Was.

That is, the ink jet recording sheet of the present invention is 1.01 g / cm ³ in an ink jet recording sheet having a paper containing natural pulp as a main component and an ink receiving layer coated on at least one surface thereof. An ink receiving layer is provided on a base paper having the above sheet density.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an ink jet recording sheet of the present invention will be described in detail. The ink jet recording sheet of the present invention is formed by using a paper mainly composed of natural pulp having a sheet density of 1.01 g / cm ³ or more as a base paper, and coating an ink receiving layer on at least one surface thereof.

[0013] As base paper mainly composed of natural pulp used in the practice of the present invention are those having a 1.01 g / cm ³ or more sheets density, preferably one having 1.03 g / cm ³ or more , 1.05 g / cm ³ or more. The base paper having a sheet density of 1.01 g / cm ³ or more is preferably prepared by using the following methods (1) to (6), and preferably using the following methods (1) to (6). It has been clarified by the study of the present inventors that they can be obtained by using two or more in combination.

(1) As the natural pulp to be used, hardwood pulp which is short-fiber and easy to produce smoothness is often used. Specifically, hardwood pulp is not less than 60% by weight, preferably 7% by weight.
Use at least 5% by weight.

(2) The pulp is beaten by using a beater so that the long fiber content is reduced as much as possible, and the freeness is set to 200 to 330 CSF.

(3) A base paper is formed by using a fourdrinier paper machine by using an appropriate papermaking method for the stock slurry to which the internal chemicals have been added, and a multistage wet paper is used in the wet part. Pressing, preferably three or more wet presses, is performed, and a smoothing roll is provided at the last stage of the press part.

(4) A tension press is used during the drying of the wet paper.

(5) Various water-soluble polymers, hydrophilic colloids or polymer latexes are contained or coated in or on the base paper. Specifically, various water-soluble polymers or hydrophilic colloids or polymer latexes are coated on a base paper or on a base paper by a size press, a tab size press, a blade coating, an air knife coating or the like to obtain a solid coating amount of 1%. .0
g / m ² or more is preferably contained or applied.

(6) After the base paper is made, calendering is performed using a machine calender, a super calender, a heat calender, or the like.

The pulp constituting the base paper used in the practice of the present invention includes chlorine, hypochlorite, chlorine bleaching ordinary bleaching treatment, alkali extraction or alkali treatment and, if necessary, hydrogen peroxide, Wood pulp of softwood pulp, hardwood pulp, softwood mixed pulp subjected to oxidative bleaching treatment with oxygen and the like, and a combination thereof is used. Can be used.

The base paper used in the practice of the present invention may contain various additives during preparation of the stock slurry. As sizing agents, fatty acid metal salts, fatty acids, alkyl ketene dimer emulsions or epoxidized higher fatty acid amides, alkenyl or alkyl succinic anhydride emulsions described or exemplified in JP-B-62-7534,
As a dry paper strength enhancer such as rosin derivative, anionic,
Cationic or amphoteric polyacrylamide, polyvinyl alcohol, cationized starch, vegetable galactomannan, etc., as wet paper strength enhancer, polyamine polyamide epichlorohydrin resin, etc., as filler, clay, kaolin, calcium carbonate, titanium oxide, etc., fixing agent As
It is advantageous to include a water-soluble aluminum salt such as aluminum chloride and bansulfate, and a pH adjusting agent such as caustic soda, sodium carbonate, sulfuric acid, and the like, in combination with other coloring pigments, coloring dyes, fluorescent whitening agents and the like as appropriate. is there.

Further, a composition comprising various water-soluble polymers or hydrophilic colloids or latex, an antistatic agent, additives and the like is placed in or on a base paper used in the practice of the present invention by a size press or tub size. It can be contained or coated by coating such as pressing, blade coating, or air knife coating. Water-soluble polymers or hydrophilic colloids include starch-based polymers, polyvinyl alcohol-based polymers, gelatin-based polymers, polyacrylamide-based polymers, cellulose-based polymers, etc. Emulsions and latexes include petroleum resin emulsions, ethylene and acrylic acid (or methacrylic acid) And styrene-butadiene, styrene-acryl, vinyl acetate-acryl,
Emulsion or latex of ethylene-vinyl acetate-based, butadiene-methyl methacrylate-based copolymers and their carboxy-modified copolymers, etc., as antistatic agents, alkali metal salts such as sodium chloride and potassium chloride, calcium chloride, barium chloride, etc. Alkaline earth metal salts, colloidal metal oxides such as colloidal silica, organic antistatic agents such as polystyrene sulfonate, as pigments, clay, kaolin, calcium carbonate, talc,
Barium sulfate, titanium oxide, etc., as a pH adjuster, hydrochloric acid, phosphoric acid, citric acid, caustic soda, etc., in addition to the above-mentioned coloring pigments, coloring dyes, additives such as fluorescent whitening agents, etc., are suitably combined and suitably contained. is there.

The thickness of the base paper used in the practice of the present invention is not particularly limited, but its basis weight is 40 to 300 g.
/ M ² are preferred.

The ink jet recording sheet of the present invention is a coating type ink jet recording sheet, and an ink receiving layer is provided on the base paper. The ink receiving layer referred to in the present invention is a layer mainly composed of a pigment and a binder that constitutes a void that penetrates and retains or absorbs the solvent in the ink, and a polymer material mainly dissolved or swelled in the solvent in the ink. And the like. These layers have no problem as the ink receiving layer of the present invention, whether they are a single layer, one or more layers each, or a combination of a pigment layer and a polymer layer.

When these ink receiving layers are provided on the base paper, a uniform ink receiving layer can be obtained. When an image is recorded on the surface of the ink receiving layer using an ink jet printer, the coloring property, It is possible to obtain a recording sheet which is excellent in clarity and free from waving on the sheet surface even after the recorded image is dried.

The reason why the waving is small is not clear, but the waving generally occurs when the paper penetrates, swelling and stress relaxation of the pulp constituting the paper, and occurs locally when the paper is dried again. This is considered to be due to the unevenness remaining. However, when the sheet density of the base paper is 1.01 g / cm ³ or more, there is almost no gap between the pulp, and the difference in locally generated unevenness is not extremely small. It is estimated that.

In one embodiment having an ink receiving layer mainly composed of a pigment and a binder, any conventionally known pigment can be used. For example, silica (colloidal silica, amorphous silica), alumina or alumina hydrate (alumina sol, colloidal alumina, cationic aluminum oxide or hydrate thereof, pseudoboehmite, etc.), aluminum silicate, magnesium silicate, magnesium carbonate , Light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, diatomaceous earth, calcium silicate, aluminum hydroxide, lithopone, zeolite, water Examples include halloysite, magnesium hydroxide, and organic pigments such as styrene-based plastic pigments, acrylic-based plastic pigments, polyethylene, microcapsules, urea resins, and melamine resins.

Among these inorganic pigments, porous inorganic pigments are preferable, and examples thereof include porous synthetic amorphous silica, porous magnesium carbonate, and porous alumina, and particularly, porous synthetic amorphous silica having a large pore volume. Alternatively, porous alumina hydrate can be preferably used. Even if the inorganic pigment is non-porous, it can be used as the pigment for the ink receiving layer of the present invention by agglomerating at the time of coating liquid preparation, or further aggregating at the time of coating and drying to form a porous coated surface, There is no problem in using these together.

As the binder, for example, polyvinyl alcohol, vinyl acetate, oxidized starch, etherified starch,
Cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, casein, gelatin, soy protein, silyl-modified polyvinyl alcohol, etc .; conjugated diene copolymers such as maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer Latex; acrylic polymer latex such as polymer or copolymer of acrylic acid ester and methacrylic acid ester, polymer or copolymer of acrylic acid and methacrylic acid; vinyl polymer latex such as ethylene vinyl acetate copolymer Or a functional group-modified polymer latex with a functional group-containing monomer such as a carboxyl group of these various polymers; an aqueous binder such as a thermosetting synthetic resin system such as a melamine resin or a urea resin; a polymethyl methacrylate, a polyurethane resin; Unfortunate Sum polyester resin, vinyl chloride -
Synthetic resin binders such as vinyl acetate copolymer, polyvinyl butyral, and alkyd resin can be mentioned, and at least one kind can be used. or,
A cationic resin to be added for fixing a conventionally known dye can also be used in combination.

The total amount of the binder can be appropriately adjusted according to the intended properties of the ink-jet recording sheet.
６０60% by weight. Further, as other additives, a pigment dispersant, a thickener, a fluidity improver, an antifoaming agent, a foam inhibitor, a release agent, a foaming agent, a penetrant, a coloring dye, a coloring pigment, a fluorescent brightening agent, An ultraviolet absorber, an antioxidant, an antiseptic, an antibacterial agent, a waterproofing agent, a wet paper strength enhancer, a dry paper strength enhancer, and the like can be appropriately blended.

In the embodiment having an ink receiving layer mainly composed of a polymer substance which dissolves or swells in the solvent in the ink, the polymer substance may be, for example, polyvinyl alcohol,
Examples include various ink-absorbing polymers such as vinyl acetate, oxidized starch, etherified starch, cellulose derivatives such as carboxymethylcellulose, and hydroxyethylcellulose, polyvinylpyrrolidone, polyethylene oxide, acrylic polymers, and polyvinyl acetal polymers. These mixtures and multiple layers can be used as the ink receiving layer of the present invention.

As a method of coating the ink receiving layer, various blade coaters, roll coaters, air knife coaters, bar coaters, rod coaters, gate roll coaters,
Various apparatuses such as a curtain coater, a short dwell coater, a gravure coater, a flexographic gravure coater, a size press, and a slide hopper system can be used on-machine or off-machine.

After the coating, finishing may be performed using a calender such as a machine calender, a heat calender, a super calender, and a soft calender.

[0034] There is no particular restriction on the thickness of the ink-receiving ^{layer, 0.5g / m 2 ~50g / m} 2 is preferred as the coating amount.

On the surface of the base paper of the present invention on the side opposite to the side on which the ink receiving layer is provided, various back coat layers are applied for antistatic properties, transport properties, curling prevention properties, writing properties, gluing properties, and the like. can do. An inorganic antistatic agent, an organic antistatic agent, a hydrophilic binder, a latex, a curing agent, a pigment, a lubricant, a matting agent, a surfactant and the like can be added to the back coat layer in an appropriate combination.

The ink referred to in the present invention includes the following colorants:
This is a recording liquid composed of a liquid medium and other additives. Examples of the colorant include water-soluble dyes such as direct dyes, acid dyes, basic dyes, reactive dyes, and food dyes, disperse dyes, color pigments, and carbon black.

As the solvent for the ink, water and various water-soluble organic solvents such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t
C1-C4 alkyl alcohols such as ert-butyl alcohol and isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones and ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane;
Polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol;
Alkylene glycols having 2 to 6 alkylene groups such as propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol; glycerin, ethylene glycol methyl ether, diethylene glycol Examples include lower alkyl ethers of polyhydric alcohols such as methyl (or ethyl) ether, triethylene glycol, and monomethyl ether. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether are preferable. Other additives include, for example, P
Examples include an H regulator, a metal sequestering agent, a fungicide, a viscosity modifier, a surface tension modifier, a wetting agent, a surfactant, and a rust inhibitor.

The ink jet recording sheet of the present invention can be used not only as an ink jet recording sheet for water-based ink, but also as any recording sheet using a liquid ink at the time of recording. For example, a heat-fusible substance, a heat-fusible ink containing a dye or pigment as a main component, a resin film, a high-density paper, an ink sheet coated on a thin support such as synthetic paper, and heated from the back surface,
An image receiving sheet for thermal transfer recording that transfers by melting ink;
Ink jet recording sheet that heats and melts heat-meltable ink to form fine droplets, and performs flight recording, ink jet recording sheet using ink in which oil-soluble dye is dissolved in solvent, ink jet using ink in which color pigment is dispersed in organic solvent Examples include a recording sheet, an image-receiving sheet corresponding to a photosensitive pressure-sensitive donor sheet using microcapsules containing a photopolymerizable monomer and a colorless or colored dye or pigment.

The common feature of these recording sheets is that the ink is in a liquid state at the time of recording. The liquid ink permeates or spreads in the depth direction or the horizontal direction of the ink receiving layer of the recording sheet until it hardens, solidifies or fixes. The above-mentioned various recording sheets require absorptivity according to each system, and there is no limitation even if the inkjet recording sheet of the present invention is used as the above-mentioned various recording sheets. Furthermore, the ink jet recording sheet of the present invention can be used as a recording sheet for heating and fixing an electrophotographic recording toner widely used in a copying machine, a printer, and the like.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
Further, “parts” and “%” shown in Examples are parts by weight and% by weight unless otherwise specified.

[0041]

【Example】

Examples 1 to 5 A mixed pulp composed of 85% by weight of hardwood bleached kraft pulp and 15% by weight of softwood bleached sulphite pulp was beaten to the beating degree shown in Table 1, and then pulp 10
0 parts by weight, 3 parts by weight of cationized starch, 0.2 parts by weight of anionized polyacrylamide, 0.4 parts by weight of an alkyl ketene dimer emulsion (as ketene dimer), and 0.4 parts by weight of a polyamide epichlorohydrin resin. It was added to prepare a stock slurry. Thereafter, the stock slurry is formed into a web by a fourdrinier paper machine, and then subjected to a three-stage wet press in a wet part, then processed with a smoothing roll, and then subjected to a two-stage tension press in a subsequent drying part. And dried. Thereafter, during the drying, 20 g of a 5% by weight carboxy-modified polyvinyl alcohol size press solution was used.
/ M ² size press, dried so that the finally obtained base paper moisture becomes 8% by weight with absolute dry moisture, machine calendered with the combinations shown in Table 1, and weighed 150 g / m ²
A base paper for an ink jet recording sheet having a density shown in Table 1 was produced.

Comparative Examples 1-3 Mixed pulp consisting of 85% by weight of hardwood bleached kraft pulp and 15% by weight of softwood bleached kraft pulp was beaten to the degree of beating shown in Table 1, and amphoteric to 100 parts by weight of pulp. Starch (Kate 3210, manufactured by Oji National)
, And 0.1 part of an alkyl ketene dimer sizing agent (Size Pine K903, manufactured by Arakawa Chemical Industry Co., Ltd.), and form a web with a fourdrinier paper machine. However, drying was performed without performing a smoothing roll treatment and without performing a gentle press in a subsequent drying part. Thereafter, during the drying, a size press liquid of 5% by weight of carboxy-modified polyvinyl alcohol was added to 20 parts.
g / m ² size press, dried so that the finally obtained base paper moisture becomes 8% by weight with absolute dry moisture, machine calendered with the combinations shown in Table 1, and weighed 150 g / m
The base papers of Comparative Examples 1 to 3 having the densities shown in Table 1 of Table ² were produced.

[Preparation of Ink-Jet Recording Sheet] 5 parts (solid content) of alumina sol AS-3 (manufactured by Catalyst Kasei Co., Ltd.) as an ink receiving layer composition was prepared on the base paper prepared above.
A coating liquid of 1 part (solid content) of polyvinyl alcohol MA-26 (manufactured by Shin-Etsu Chemical Co., Ltd.) and water having a solid content of about 10% is prepared, and coated with a bar coater to a dry coating amount of 15 g / m ^2. Then, the resultant was dried to produce an ink jet recording sheet.

The ink jet recording sheets prepared in Examples and Comparative Examples were evaluated by the following evaluation methods, and the results are shown in Table 1.

[Rippling after Image Recording] Rippling after image recording is performed by drawing a high-definition photographic image with a wide range of hue and lightness, leaving it for one day, and visually checking the ripple on the recording surface after drying. The evaluation was made on a scale of 1 to 5. ◎: Very good undulation after image recording か な り: Very good undulation after image recording ◇: Good undulation after image recording △: Slightly poor undulation after image recording ×: Poor undulation after image recording

[0047]

[Table 1]

As shown in Table 1, the density of the base paper was 1.01 g / c.
In the embodiment using m ³ or more of it can be seen that the waviness after image recording drying is obtained favorable.

[0049]

As described above, the ink jet recording sheet of the present invention using the base paper for an ink jet recording sheet, that is, the base paper having a honeyness of 1.01 g / cm ³ and having an ink receiving layer coated on the base paper, is obtained. Thus, a coating type ink jet recording sheet having excellent waving after image recording and drying can be obtained.

Claims (1)

[Claims] 1. An ink jet recording sheet comprising a paper mainly composed of natural pulp as a base paper and an ink receiving layer coated on at least one side thereof, wherein the base paper is 1.0
An ink jet recording sheet having a sheet density of 1 g / cm ³ or more.