JPH0752529A - Ink jet recording sheet - Google Patents

Abstract

PURPOSE:To provide an ink jet recording sheet of a finely coating type which has no coating unevenness of a surface of an ink reception layer and excellent absorption, clarity of ink. CONSTITUTION:An ink jet recording sheet comprises a base sheet by hot pressing wet sheet containing a moisture content of 50-70wt.%, and an ink reception layer composition containing nonspherical cationic colloidal silica as a main ingredient.

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 specifically, it has excellent coatability of the coating liquid for the ink receiving layer, has no uneven coating on the surface of the ink receiving layer, and has a high ink absorbability. And a fine coating type inkjet recording sheet excellent in sharpness.

The ink jet recording system is a system in which minute droplets of ink are ejected and adhered to a recording sheet such as paper by various operating principles to record images, characters, etc. It has features such as easy colorization, 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 Kanji and color images. Further, an image formed by a multicolor ink jet system can obtain a recording comparable to that of multicolor printing by a plate making system or printing by a color photographic system. Further, in applications requiring a small number of copies, it is being widely applied to the field of full-color image recording because it is cheaper than the photographic technique.

As a recording sheet used in this ink jet recording system, efforts have been made from the aspect of the apparatus and ink composition so as to use high-quality paper or coated paper used for ordinary printing and writing. However, as the performance of the inkjet recording apparatus has been improved and the applications have been expanded, such as speeding up, high definition, or full-color of the apparatus, more advanced characteristics have been required for the recording sheet. That is, as the recording sheet, the density of print dots is high, the color tone is bright and vivid, the ink does not run or bleed even when the print dots overlap and the print dots overlap. It is required that the diffusion in the direction is not unnecessarily large and that the periphery is smooth and not blurred.

As the form of the ink jet recording sheet, an ink receiving layer is provided on a support surface such as plain paper type represented by so-called high-quality paper / bonded paper, paper such as high-quality paper, synthetic paper, synthetic resin film and the like. It is roughly divided into coating type.

The coating type includes a low coating type of about 1 to 10 / m ^{2, a} medium coating type of about 10 to 20 g / m ² ,
There are high coating type inkjet recording sheets of 20 g / m ² or more. In particular, in recent years, even a low coating type, a lower coating amount of 0.5 to 5 g / m ² of a fine coating type is close to that of plain paper, which is preferable in terms of appearance and handling. The coating type has been desired. The light coating type ink jet recording sheet has a small coating amount of the ink receiving layer coated on the base paper, and various characteristics of the ink jet recording sheet largely depend on the base paper, so that a uniform ink receiving layer can be obtained. Is the most preferable means for increasing the uniformity and smoothness of the base paper. That is,
By increasing the uniformity and smoothness of the base paper, it becomes easy to apply the ink receiving layer coating liquid, and the applied ink receiving layer can be a uniform coating layer.

To improve the uniformity and smoothness of the base paper,
There are various known techniques in the past, for example, a method of adjusting the fiber length distribution of pulp used for base paper within a certain range, a method of adjusting papermaking conditions such as papermaking concentration, and the like.

[0007] Further, a method of pressing the wet paper having a predetermined water content rate tightly, a method of adhering one side of the wet paper to a heating mirror surface dryer to dry, or a method of performing various calendering treatments on the base paper, etc. Various attempts have been made to improve the sex.

[0008]

As described above, in the slightly coated type ink jet recording sheet, the base paper is used for the purpose of improving the uniformity and smoothness of the base paper and improving the coatability of the ink receiving layer coating liquid. Although various attempts have been made, any of these methods can be used as a base paper for an inkjet recording sheet, which has a desired uniformity and smoothness and is excellent in coatability of the ink receiving layer coating liquid. could not.

That is, an object of the present invention is to provide a fine coating type ink jet recording sheet even for an ink jet recording sheet, which has excellent coatability of the ink receiving layer coating liquid and has no uneven coating of the ink receiving layer, and The purpose of the present invention is to obtain an inkjet recording sheet having excellent ink absorbency and sharpness.

[0010]

Means for Solving the Problems As a result of intensive studies in view of the above, the present inventors have found that the coating property of the ink receiving layer coating liquid is excellent, there is no coating unevenness of the ink receiving layer, and the ink absorbency and The inventors have invented an inkjet recording sheet having excellent sharpness. That is, the inkjet recording sheet of the present invention is an inkjet recording sheet obtained by coating an ink receiving layer on a base paper, and the base paper is formed by hot pressing a wet paper having a moisture content of 50 to 70% by weight. The ink receiving layer composition is characterized by being a non-spherical cationic colloidal silica as a main component.

In the ink jet recording sheet of the present invention, the base paper is obtained by hot pressing a wet paper between a steam heating roll and an elastic roll.

The ink jet recording sheet of the present invention is characterized in that the non-spherical cationic colloidal silica is needle-like or fibrous.

The ink jet recording sheet of the present invention will be described in detail below. The ink jet recording sheet of the present invention is a slightly coated type ink jet recording sheet, and the ink receiving layer is coated on the base paper in an amount of 0.5 to 5 g.
It is a thin coating of / m ² and is slightly coated with the smoothness of the base paper surface being reflected as it is. The degree of fine coating is
The smoother the surface of the base paper itself is, the less uneven the coating can be. That is, the higher the uniformity and smoothness of the base paper, the better the coatability of the ink receiving layer coating liquid,
It is possible to apply the ink receiving layer uniformly.

In the ink jet recording sheet of the present invention, in coating using an aqueous coating liquid such as an ink receiving layer coating liquid, selection of raw material pulp, type and amount of beating condition additive chemicals,
It was expected that the pressing method would have a great influence on the base paper, in addition to the calender conditions, and the smoothness returned little.

Among various pressing methods, the water content is 50%.
By hot-pressing 70% by weight of wet paper, a base paper with high smoothness can be obtained with a linear pressure lower than that at the press at room temperature, there is little reversion after coating, and further between the steam heating roll and the elastic roll. These effects were particularly large when hot pressing was performed.

The effect of hot pressing is that the viscosity of water is reduced by heating to facilitate the movement of water, and smoothing is performed under the condition that the plasticity of the fiber network is also increased. It is considered that the layer is easily formed and is not easily affected by the rewetting sequence in the subsequent process. When a heating roll is used, it is considered that the heat transfer is efficient and that the vicinity of the surface is selectively heated, so that the heating roll is more easily smoothed.

The moisture content of the wet paper in the present invention means JIS.
Based on P8127, it is a value calculated by the following formula 1.

[0018]

[Equation 1] Moisture content of wet paper (%) = (mass of water in wet paper / mass of wet paper before drying) x 100

The moisture content of the wet paper which is hot pressed is 50 to 50.
It must be in the range of 70% by weight. here,
When the amount is less than 50% by weight, the water content is too small and the smoothness is apt to return during coating. When the amount is more than 70% by weight, the water content is too much and the smoothness improving effect is hardly exhibited. Therefore, it is effective that the hot press of the present invention is performed on the wet paper which has been squeezed by the first press or the subsequent press to adjust the water content.

Hot pressing in the present invention means 60 ° C.
Pressing the wet paper at a temperature of ~ 100 ° C. For an overview of this technology, see Tappi Journal, 1986.
This is a technique developed for the purpose of improving the water squeezing ability in a press described in April issue, p. 64, the same issue, August 1990, p. 99, etc. As a heating method, it is common to heat the wet paper surface immediately before the press nip with a steam box, an infrared heater, etc., but recently, steam is blown into the roll of the press to heat the press roll to the steam temperature. The method is also in practical use. Regarding the smoothness improving effect of the present invention, the method of hot pressing between the steam heating roll and the elastic roll as in the latter case is superior. It is also possible to implement such various hot presses by combining them in multiple stages.

As the press device of the present invention, various types of press such as a plain press, a suction press, a grooved roll press, a fabric press, a high eye press can be used, but the surface on which the ink receiving layer is coated has a smooth surface. And the Shore D hardness of the roll (ASTM standard, D-
It is preferable to arrange rolls having a 2240) of 85 degrees or more. When hot pressing between the steam heating roll and the elastic roll, the surface of the ink receiving layer coated surface is heated by heating the metal roll whose smoothness and releasability are improved by subjecting the surface to ceramic spraying treatment or the like. It is effective to improve the smoothness. The elastic roll used in this case had a Shore D hardness of 60 to 9 coated with a synthetic resin.
A 0 degree roll can be used.

The linear pressure of the hot press of the present invention varies depending on the type of pulp, beating degree, paper making speed, number of press nips, etc., but is usually in the range of 20 to 150 kN / m, and the base paper density is 0.65. It is adjusted to be about 0.90 g / cm ³ .

The ink jet recording sheet of the present invention is a base paper within the scope of the present invention as described above, to which an ink receiving layer is finely coated, and a smooth and uniform ink is reflected in the uniformity of the base paper. It can be the acceptance layer. When the ink-receiving layer is coated uniformly, when the ink is applied to the ink-receiving layer surface using an inkjet printer, the ink-receiving layer surface is coated evenly. It does not spread,
This is because it is possible to represent a recording dot that is close to a perfect circle, and surplus ink permeates from the ink receiving layer surface in the thickness direction of the base paper. On the other hand, in the base paper outside the scope of the present invention, coating unevenness is likely to occur on the ink receiving layer surface, the ratio of the ink spreading in the recording surface direction increases, and as a result, the recording dots have a shape deviated from a perfect circle. Further, the penetration into the base paper becomes irregular, and ink bleeding appears.

In the ink jet recording sheet of the present invention, the surface of the ink receiving layer can be a surface reflecting the smoothness of the raw paper surface by using a composition mainly containing non-spherical cationic colloidal silica. Regarding the particle size of the non-spherical cationic colloidal silica, when compared with the pulp fiber forming the base paper, the fiber width of the pulp fiber is several tens.
With respect to the order of μm, the maximum minor axis of the colloidal silica is 50 nm or less, preferably 30 nm or less.
The smaller the maximum shortest diameter is, the more uniform the coating on the raw paper surface is, which is preferable. The length of the colloidal silica is
It is 300 nm or less, preferably 100 nm or less. As these non-spherical cationic colloidal silica, those which are dispersed in water in a colloidal state while maintaining the primary particle diameter are used.

As the non-spherical cationic colloidal silica used in the present invention, the surface of the colloidal silica is coated with a metal oxide hydrate which is a cation modifier,
It is cation-modified. The term “non-spherical” as used in the present invention means that it is not substantially spherical and has various forms such as needle-like, columnar, bead-like, rod-like, plate-like, lump-like, fibrous and spindle-like, but especially needle-like or A fibrous material is preferably used.

The non-spherical cationic colloidal silica used in the ink jet recording sheet of the present invention is a cation composed of a metal oxide hydrate such as aluminum oxide hydrate, zirconium oxide hydrate and tin oxide hydrate. The colloidal silica coated with a modifier is preferably used, and particularly, the one that is cation-modified with aluminum oxide hydrate is preferably used. As the cation modification method, the method described in U.S. Pat. No. 3,007,878, JP-B-47-26959, etc. can be used.

In the non-spherical cationic colloidal silica used in the ink jet recording sheet of the present invention, the coating amount of the metal oxide hydrate which is a cation modifier is
1 in terms of metal oxide relative to silica (in terms of SiO ₂ )
A range of up to 30% by weight is useful. If the coating amount of the cation modifier is too small (1% by weight), the water resistance of the image recorded on the ink jet recording sheet will be remarkably deteriorated. On the contrary, if the coating amount is too large, the physical properties of the coating surface will be weak. It causes cracks and the exposed pulp fiber surface becomes noticeable. The coating amount is preferably 2.5 to 25% by weight,
More preferably, it is 5 to 20% by weight. The dispersion liquid of non-spherical cationic colloidal silica may contain an acid component such as acetic acid, citric acid, sulfuric acid, phosphoric acid for the purpose of a colloid stabilizer and the like.

The ink jet recording sheet of the present invention comprises
In addition to the non-spherical cationic colloidal silica, an ultrafine particle inorganic pigment can be used in combination. The following can be illustrated as the ultrafine particle inorganic pigment. For example,
Silica (colloidal silica), alumina or alumina hydrate (alumina sol, colloidal alumina, cationic aluminum oxide or its hydrate, pseudo-boehmite, etc.), surface-treated cationic colloidal silica, aluminum silicate, magnesium silicate, magnesium carbonate Etc., and it is more preferable if the primary particles are porous,
Even if it is non-porous, it is preferred that it aggregates during preparation of the coating liquid or further aggregates during coating drying, forming a porous surface-coated surface on the pulp fiber surface. Particularly, in the present invention, each pulp fiber on the surface of the base paper has a fiber width of several 10
It is preferable to coat the pulp fiber itself with non-spherical cationic colloidal silica having an average particle size of ⅕ or less.

Further, as the inorganic pigment that can be used together with the ultrafine particle inorganic pigment, any conventionally known inorganic pigment can be used. For example, light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth,
Examples thereof include calcium silicate, synthetic amorphous silica, aluminum hydroxide, lithopone, zeolite, hydrohaloysite, magnesium hydroxide and the like. Among these inorganic pigments, porous inorganic pigments are preferable, and porous synthetic amorphous silica, porous magnesium carbonate, porous alumina and the like can be mentioned, and particularly porous synthetic amorphous silica having a large pore volume is preferable. . Further, organic pigments such as styrene-based plastic pigments, acrylic-based plastic pigments, polyethylene, microcapsules, urea resins and melamine resins can be used together with the above ultrafine inorganic pigments.

As a binder used together with the non-spherical cationic colloidal silica in coating the ink receiving layer, for example, polyvinyl alcohol, vinyl acetate, oxidized starch, etherified starch, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose. , Casein, gelatin, soybean protein, silyl modified polyvinyl alcohol, etc .; maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, etc. conjugated diene copolymer latex; acrylic acid ester and methacrylic acid ester Polymers or copolymers of Acrylic acid, Methacrylic acid polymers or copolymers, Acrylic polymer latices; Ethylene vinyl acetate copolymers or other vinylic polymer latices; Functional group-modified polymer latex according to the functional group-containing monomers such as Bokishiru group; melamine resins,
Aqueous binder such as thermosetting synthetic resin such as urea resin; polymethylmethacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer,
Examples thereof include synthetic resin-based binders such as polyvinyl butyral and alkyd resin, and at least one kind can be used. Also, a cationic resin added for the purpose of fixing a conventionally known dye can be used together.

The total amount of the binder can be appropriately adjusted according to the characteristics of the intended ink jet recording sheet, but in general, it is 5 per 100% by weight of the pigment.
-60% by weight. Furthermore, as other additives, a pigment dispersant, a thickener, a fluidity improver, a defoaming agent, a foam suppressor, a release agent, a foaming agent, a penetrant, a coloring dye, a coloring pigment, a fluorescent whitening agent, An ultraviolet absorber, an antioxidant, an antiseptic agent, an antifungal agent, a water resistance agent, a wet paper strength enhancer, a dry paper strength enhancer and the like can be appropriately blended.

In the present invention, the method of coating the ink receiving layer may be coating or impregnation, but the coating amount on the surface of the ink receiving layer is not particularly limited. Normally, 0.5-5 g /
m ² is preferable, but more may be applied.

The base paper according to the present invention means LBKP, NBK
Chemical pulp such as P, GP, PGWRMP, TMP, CT
Mechanical pulp such as MP, CMP and CGP, wood pulp such as waste paper pulp such as DIP, and conventionally known pigments as main components, and binder and sizing agent, fixing agent, yield improving agent, cationizing agent, paper strengthening agent A mixture of at least one kind of various additives such as, for example, a base paper manufactured by various devices such as a Fourdrinier paper machine, a cylinder paper machine, and a twin wire paper machine, and further, a base paper with starch, polyvinyl alcohol, etc. Includes size-pressed base paper. Such a base paper may be provided with a surface coating layer as it is, or a calender device such as a machine calender, a TG calender or a soft calender may be used for the purpose of controlling the flatness.

As a method of coating or impregnating, various blade coaters, roll coaters, air knife coaters, bar coaters, rod coaters, gate roll coaters, curtain coaters, short dwell coaters, gravure coaters, flexo gravure coaters, size presses, etc. Various devices can be used on-machine or off-machine. However, in the present invention, a size press, a rod coater, a gate roll coater and an air knife coater are particularly preferable. Also, after coating or impregnation, machine calendar, TG
It may be finished using a calendar such as a calendar, super calendar, or soft calendar.

The aqueous ink referred to in the present invention is a recording liquid containing the following colorant, 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.

As the solvent for the aqueous 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, tert-butyl alcohol, C1-C4 alkyl alcohols such as isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyethylene glycol, polypropylene glycol Polyalkylene glycols such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hex Alkylene glycols having 2 to 6 alkylene groups such as len glycol and diethylene glycol; lower alkyl ethers of polyhydric alcohols such as glycerin, ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol and monomethyl ether Is mentioned. 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, a pH adjusting agent, a sequestering agent, an antifungal agent, a viscosity adjusting agent,
Surface tension adjusting agents, wetting agents, surfactants, rust preventives and the like can be mentioned.

The ink jet recording sheet according to the present invention is not limited to use as an ink jet recording sheet, but can be used as any recording sheet using a liquid ink during recording. For example, an ink sheet obtained by applying a heat-melting ink containing a heat-melting substance, a dye or pigment, etc., as a main component on a thin support such as a resin film, high-density paper, or synthetic paper is heated from the back surface to remove the ink. An image-receiving sheet for thermal transfer recording that is melted and transferred, an inkjet recording sheet that heat-melts a heat-meltable ink to form fine droplets and performs flight recording, an inkjet recording sheet that uses an ink in which an oil-soluble dye is dissolved in a solvent, photopolymerization Examples thereof include an image receiving sheet corresponding to a light and pressure sensitive donor sheet using microcapsules encapsulating a type monomer and a colorless or colored dye or pigment.

The common point of these recording sheets is that the ink is in a liquid state at the time of recording. The liquid ink penetrates or spreads in the depth direction or the horizontal direction of the ink receiving layer of the recording sheet before being cured, solidified, or fixed. The various recording sheets described above require absorptivity according to their respective methods, and the inkjet recording sheet of the present invention may be used as the various recording sheets described above without any limitation. Further, the ink jet recording sheet of the present invention can be used as a recording sheet for heating and fixing toner of an electrophotographic recording system which is widely used in copying machines, printers and the like.

[0040]

The ink jet recording sheet of the present invention uses a base paper obtained by hot-pressing a wet paper having a moisture content of 50 to 70% by weight, and an ink receiving layer comprising a non-spherical cationic colloidal silica as a main component on the base paper. By applying
It is possible to obtain an ink jet recording sheet of a fine coating type which has excellent coatability of the coating liquid for the ink receiving layer, has no coating unevenness on the surface of the ink receiving layer, and has excellent ink absorbency and sharpness.

[0041]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.
Further, “parts” and “%” shown in the examples represent parts by weight and% by weight, unless otherwise specified.

Examples 1 to 3 [Preparation of base paper] LBK beaten to a freeness of 300 ml
Pulp 100 in which P and NBKP were mixed in a weight ratio of 7: 3
Light calcium carbonate (trade name: TP121,
Okutama Industry Co., Ltd.) 7 parts, alkyl ketene dimer size agent (trade name: Hacon 11-2, Dick Hercules Co. Ltd.) 0.1 part, amphoteric starch (trade name: Kate 321)
0, manufactured by Oji National Co., Ltd.) was used to produce a base paper having a basis weight of 85 g / m ² by a Fourdrinier paper machine having a paper making speed of 450 m / min under the following press conditions.

In this paper machine, three presses are installed in front of the dryer. Steam was blown into the top roll (XG roll, manufactured by Yamauchi Co., Ltd.) of No. 3 press to bring the surface temperature to 7
Hot pressing was performed under the condition that the linear pressure was controlled to 0 ° C. and the linear pressure was 50 kN / m. At this time, by adjusting the conditions of No. 1 and No. 2 presses, the moisture content of the wet paper at the inlet of the hot press was changed to three levels of 50, 60 and 70%. The base paper after drying with a multi-cylinder dryer was size-pressed with a 3% aqueous solution of oxidized starch, and after drying, the thickness was adjusted with a machine calender so that the density was 0.80 g / cm ³ , and each of Example 1 was used. It was used as the base paper for the ink jet recording sheets 3 to 3.

[Preparation of Inkjet Recording Sheet] Needle-like colloidal silica was used as an ink receiving layer composition on the base paper for each inkjet recording sheet prepared as described above, and Al ₂ O ₃ was added to silica (SiO ₂ conversion). A 10% aqueous dispersion of acicular cation-modified colloidal silica modified with about 6.2% by weight of aluminum oxide hydrate (particle size; width 10 to 20 nm x length 50 to 200 n).
m) 1000 parts, 300 parts of a 10% aqueous solution of polyvinyl alcohol (PVA 117, manufactured by Kuraray Co., Ltd.) as an adhesive,
A 60% aqueous solution of a cationic resin as a dye fixing agent (Polyfix 601, cationic charge amount 6.9 meq./
g, manufactured by Showa Polymer Co., Ltd.) An aqueous dispersion containing 50 parts as a main component and having a solid content concentration of 10% is dried with a rod coater at a coating speed of 300 m / min to give a dry solid content of 1 g / m ^2. An inkjet recording sheet was prepared by coating, drying and calendering.

Example 4 [Preparation of base paper] In Example 1, a top roll of No. 3 press was not heated with steam, but a wet paper having a water content of 60% was steamed immediately before No. 3 press with a surface temperature of 70%. A base paper for an ink jet recording sheet was prepared in the same manner as in Example 1 except that pressing was performed after heating to ° C.

[Preparation of Inkjet Recording Sheet] The base paper for the inkjet recording sheet prepared as described above is
A 10% aqueous dispersion of columnar cationic colloidal silica (particle size; width 40 nm × length 1) was used as the ink receiving layer composition.
100 parts (00-300 nm), 300 parts of a 10% aqueous solution of polyvinyl alcohol (PVA 117, manufactured by Kuraray Co., Ltd.) as an adhesive, and 60 parts of a cationic resin as a dye fixing agent.
% Aqueous solution (Polyfix 601, cationic charge amount 6.
9 meq. / G, manufactured by Showa High Polymer Co., Ltd.) Aqueous dispersion containing 50 parts as a main component and having a solid content concentration of 15% is dried and solidified at a coating speed of 300 m / min using an air knife coater to give a solid content of 3 g / m.
^An inkjet recording sheet was prepared by coating so as to be ² , dried and calendered.

Comparative Examples 1 and 2 In Example 1, the wet paper moisture content at the hot press inlet is 4
A base paper for an inkjet recording sheet was prepared in the same manner as in Example 1 except that the content was changed to 8 and 75%, and the inkjet recording sheets of Comparative Examples 1 and 2 were prepared using the ink receiving layer coating liquid of Example 1. It was made.

Comparative Example 3 An inkjet recording sheet was prepared in the same manner as in Example 4 except that the base paper for inkjet recording sheet was prepared without hot pressing by steam heating.

Comparative Example 4 In Example 4, the base paper after drying to a moisture content of 10% without hot pressing by steam heating was subjected to a soft calendar between a hard chrome-plated surface and an elastic roll having a Shore D hardness of 78 degrees. A base paper for an inkjet recording sheet was produced in the same manner as in Example 4 except that the treatment was performed. Subsequently, as an ink receiving layer composition, a 40% aqueous dispersion of spherical colloidal silica (primary particle size 300 ± 30
nm) 250 parts, an aqueous solution of polyvinyl alcohol (PVA 117, manufactured by Kuraray Co., Ltd.) as an adhesive, a 60% aqueous solution of a cationic resin as a dye fixing agent (Polyfix 601, cationic charge amount 6.9 meq./g, Showa High) (Molecular Co., Ltd.) 50 parts by weight of an aqueous dispersion having a solid content concentration of 10% using a gate roll coater and a coating speed of 3
Coating so that the dry solid content is 2 g / m ² at 00 m / min,
An ink jet recording sheet was prepared by drying and calendering.

The ink jet recording sheets prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated according to the following method, and the results are shown in Table 1.

[Smoothness] The smoothness is a tester (Microtopograph, manufactured by Toyo Seiki Co., Ltd.) that evaluates the smoothness from the contact rate when the sample is pressed against the surface of the prism at a constant pressure (10 kg / cm ² ). Is the smoothness after coating the ink receiving layer on each base paper. The smoothness after coating was evaluated based on this smoothness.

[Coatability] The coatability was evaluated on an ink jet recording sheet coated with the ink receiving layer composition at a coating speed of 300 m / min on a base paper using various coaters. In addition, as an evaluation criterion, the coating unevenness is shown in order from the smallest, A is good in characteristics, B is good in a range where there is no practical problem,
C was regarded as a problem in practical use.

[Ink absorbency and sharpness] The ink absorbency and the sharpness of the image are determined by the boundary between the solid color solid print portions, for example, red print (magenta + yellow) and green print (cyan + cyan).
The degree of ink bleeding at the boundary portion of (yellow) was visually determined. When the red printed portion and the green printed portion did not overlap and were separated, the characteristics were good, and when the overlapping was large and a black line was formed, the characteristics were bad. A substance having poor ink absorbability remarkably impairs image quality (image sharpness), so that it does not make any sense even if other properties such as image density are good. In addition, as an evaluation criterion, A indicates a good characteristic, B indicates a good practically acceptable range, C indicates a practical problem, and D indicates a poor characteristic.

[0054]

[Table 1]

From the results of Table 1, Examples 1 to 3 and Comparative Example 1
When comparing ~ 2, the moisture content of the wet paper before hot pressing is 5
By adjusting the content to 0% or more and 70% or less, good coatability, ink absorbency, and clearness are obtained, and the excellent smoothness after coating the ink receiving layer is also involved. I understand. In addition, comparing Examples 1 to 3 and Comparative Examples 3 to 4, it can be seen that the hot press has excellent coatability as compared with the case of using a normal press or a soft calender. In the case of a soft calendar, the coatability after coating is inferior although the base paper has good smoothness.

[0056]

The ink jet recording sheet of the present invention is
By using a base paper obtained by hot pressing a wet paper having a specific moisture content, and by using non-spherical cationic colloidal silica in the ink receiving layer composition, the coating property of the ink receiving layer coating liquid is excellent. The inkjet recording sheet is a slightly coated type ink jet recording sheet which has no coating unevenness on the ink receiving layer surface and can obtain excellent ink absorption and sharpness.

Claims (3)

[Claims] 1. An ink jet recording sheet comprising a base paper coated with an ink receiving layer, wherein the base paper has a moisture content of 5
An ink jet recording sheet, comprising a wet paper of 0 to 70% by weight, hot-pressed, wherein the ink receiving layer composition is a non-spherical cationic colloidal silica as a main component. 2. The ink jet recording sheet according to claim 1, wherein the base paper is obtained by hot pressing a wet paper web between a steam heating roll and an elastic roll. 3. The non-spherical cationic colloidal silica comprises:
A needle-shaped or fiber-shaped material.
Or the inkjet recording sheet according to 2.