JPH0752527A - 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 having a product of heat shrinkage factor RMD in a machine direction of the sheet and heat shrinkage factor RCD of a cross machine direction of 0.20 or less and a ratio RCD/RMD of the factor in the machine direction to that in the cross machine direction of 2.3 or less, 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 reflects the dimensional stability and smoothness of the base paper and is excellent in the coating property of the ink receiving layer coating liquid, The present invention relates to a fine coating type inkjet recording sheet which has no uneven coating on the layer surface and is excellent in ink absorbency and 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 dimensional stability and smoothness of the base paper. That is, by increasing the dimensional stability and smoothness of the base paper, the shrinkage of the ink receiving layer coating liquid during coating and drying is reduced, and the applied ink receiving layer can be a uniform coating layer.

There are various known techniques for improving the dimensional stability and smoothness of the base paper. For example, a method for controlling the fiber length distribution of pulp used for the base paper within a certain range, a papermaking concentration, etc. There are methods such as adjusting the papermaking conditions.

Various attempts have been made to improve dimensional stability, such as a method in which a wet paper having a predetermined water content is pressed tightly, a method in which one side of the wet paper is brought into close contact with a heating mirror dryer and dried. .

[0008]

As described above, in the slightly coated type inkjet recording sheet, the base paper is used for the purpose of improving the dimensional stability and smoothness of the base paper and improving the coatability of the ink receiving layer coating liquid. Although various attempts have been made to obtain a base paper for an ink jet recording sheet, the desired dimensional stability and smoothness can be achieved by any of these methods, and the coating property of the ink receiving layer coating liquid is excellent. I couldn't.

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 The inventors of the present invention have conducted extensive studies in view of the above, and as a result, the dimensional stability and smoothness of the base paper are reflected, and the coating property of the ink receiving layer coating liquid is excellent and the ink receiving layer is excellent. The present invention has led to the invention of an inkjet recording sheet that has no uneven coating on the layers and is excellent in ink absorbency and 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 product of the heat shrinkage ratio RMD in the machine direction and the heat shrinkage ratio RCD in the cross machine direction of the base paper is 0. 20 or less and the ratio R of the heat shrinkage ratio in the cross machine direction to the machine direction
The CD / RMD is 2.3 or less, and the composition of the ink receiving layer is a non-spherical cationic colloidal silica as a main component.

The ink jet recording sheet of the present invention is characterized in that the base paper is dried by a single tier dryer having no open draw.

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 more the surface of the base paper itself has dimensional stability and smoothness, the less uneven the coating can be. That is, the higher the dimensional stability and smoothness of the base paper, the better the coatability of the ink-receiving layer coating liquid, and the more uniform coating of the ink-receiving layer became possible.

In the ink jet recording sheet of the present invention, the heat shrinkage of the base paper is a temperature of 20 ° C. and a relative humidity of 65%.
It is a value calculated by the following formula from the amount of shrinkage when the sample whose humidity was controlled for 24 hours under the above condition was dried at 105 ° C. for 5 minutes.

Thermal shrinkage (R) = dL / L × 100 Here, dL is the difference in the length of the test piece before and after drying, and L is the length of the test piece before heating. In the present invention, the heat shrinkage ratio was measured in the machine direction and the cross machine direction of the base paper and expressed as RMD and RCD, respectively.

In order to obtain the base paper to be used in the ink jet recording sheet of the present invention, the heat shrinkage itself is suppressed and the heat shrinkage ratio product RMD × RCD of the base paper in the machine direction and the cross machine direction is set to 0.20 or less. 1. Reduce the shrinkage anisotropy to reduce the heat shrinkage ratio RCD / RMD.
It is necessary to satisfy both of 3 or less.

As a method of reducing the product of heat shrinkage,
Use of pulp with high α-cellulose content, beating to give priority to cutting over swelling of fibers, increase water squeeze in press to reduce drying load in dryer, tension of canvas in dryer The paper and paper technical association magazine, 45, No. 1, p. 78, or 8
A method of reducing shrinkage during drying of wet paper with a dryer, such as the use of a dryer without an open draw (single tier dryer) as described in pages 9 to 90 (1991), can be used.

As a method of reducing the ratio of heat shrinkage in the machine direction to the cross machine direction, adjustment of the forming board position of the wire part, optimization of the jet / wire speed ratio, reduction of draw in the press or dryer, There is a use of a dryer without the above open draw.

The ink jet recording sheet of the present invention is a base paper within the scope of the present invention as described above, which is slightly coated with an ink receiving layer, and is smooth and uniform reflecting the dimensional stability of the base paper. It can be an ink receiving 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,
Recording dots close to a perfect circle can be expressed, 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 the 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 in combination 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 a coating or impregnation method, 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 thermal calender or a soft calender may be used for the purpose of controlling flattening.

Examples of coating and impregnating methods include 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 and the like. 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 of 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.

[0035]

The ink jet recording sheet of the present invention has a heat shrinkage ratio RMD in the machine direction and a heat shrinkage ratio RCD in the cross machine direction.
Is 0.20 or less, and the ratio RCD / RMD of the heat shrinkage ratio in the cross machine direction to the machine direction is 2.3.
By using the following base paper and applying an ink receiving layer composed of non-spherical cationic colloidal silica as a main component on the base paper, the coating property of the ink receiving layer coating liquid is excellent, and the ink receiving layer surface is coated. It is possible to obtain a fine coating type ink jet recording sheet which has no unevenness in processing and is excellent in ink absorbency and sharpness.

[0036]

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.

Example 1 [Preparation of base paper] Freeness 3 with a double disc refiner
00 ml, 400 ml with LBKP beaten to csf,
To 100 parts of mixed pulp having a 7: 3 weight ratio of NBKP beaten to csf, 1.0 part of cationic starch (Kate F, manufactured by Oji National Co., Ltd.) and alkyl ketene dimer sizing agent (Harcon 11-2, Dick-Hercules Co., Ltd.) was used to add 0.1 part of paper stock, and
A base paper having a basis weight of 85 g / m ² was produced on a fourdrinier paper machine of 00 m / min.

In this case, the jet / wire ratio was 1.03, the moisture content at the dryer inlet was 53%, the speed difference between the press and the dryer was 1.0 m / min, and there was no open draw for drying. I went with a single tier dryer. The dried paper was size-pressed and dried with an aqueous solution of oxidized starch having a concentration of 3%, and then smoothed with a machine calendar so that the Bekk smoothness was 50 seconds or more.

[Preparation of Inkjet Recording Sheet] Needle-like colloidal silica as an ink-receiving layer composition on the base paper prepared as described above was used in an amount of about 6.2 weight% in terms of Al ₂ O _{3 with} respect to silica (in terms of SiO ₂ ). % 10% aqueous dispersion of acicular cation-modified colloidal silica modified with aluminum oxide hydrate (particle size; width 10 to 20 nm x length 5)
0 to 200 nm) 1000 parts, polyvinyl alcohol 10% aqueous solution as an adhesive (PVA 117, manufactured by Kuraray Co., Ltd.) 300 parts, and cationic resin 60 as a dye fixing agent.
% Aqueous solution (Polyfix 601, cationic charge amount 6.
9 meq. / G, manufactured by Showa High Polymer Co., Ltd.) An aqueous dispersion containing 50 parts as a main component and having a solid content concentration of 10% is dried using a rod coater at a coating speed of 300 m / min to give a dry solid content of 1 g / m ^2. Was coated, dried and calendered to prepare an inkjet recording sheet.

Example 2 In Example 1, the jet ratio was 1.00, the drying was an ordinary multi-cylinder dryer, the draw between the press and the dryer was 0.5 m / min, and the tension of the dryer canvas was 1.
A base paper was prepared in the same manner as in Example 1 except that the composition was 7 kg / cm, and an ink jet recording sheet was prepared using the same ink receiving layer composition as in Example 1 on the base paper.

Example 3 The same as Example 2 except that the pressurization of the press was increased to reduce the moisture content at the dryer inlet to 51% and the tension of the dryer canvas was set to 1.5 kg / cm. Then, a base paper was prepared. On this base paper, as an ink receiving layer composition, 10 parts of a columnar cationic colloidal silica was prepared.
% Aqueous dispersion (particle size; width 40 nm x length 100 to 300 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 High Polymer Co., Ltd.) An aqueous dispersion containing 50 parts as a main component and having a solid content concentration of 15% is applied by an air knife coater to a dry solid content of 3 g / m ² , dried, and calendered. An ink jet recording sheet was prepared by finishing.

Comparative Example 1 A base paper was prepared in the same manner as in Example 1 except that the drying was carried out by a multi-cylinder dryer. Subsequently, the ink-receiving layer composition of Example 4 was applied to the prepared base paper so that the dry solid content was 3 g / m ² , dried, and calendered to prepare an inkjet recording sheet.

Comparative Example 2 The same as Example 2 except that the freeness of LBKP was 250 ml by viscous beating with a deluxe finer to csf and the tension of the dryer canvas was 1.4 kg / cm. To produce a base paper. Then, a 40% aqueous dispersion of spherical colloidal silica (primary particle diameter 300 ± 30 nm) was added to the prepared base paper as an ink receiving layer composition.
250 parts, 300 parts of an aqueous solution of polyvinyl alcohol (PVA 117, manufactured by Kuraray Co., Ltd.) as an adhesive, and 60% aqueous solution of a cationic resin as a dye fixing agent (Polyfix 6).
01, cation charge amount 6.9 meq. / G, manufactured by Showa Highpolymer 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 300 m.
The coating composition was dried so that the dry solid content would be ² g / m ² at 1 / min, dried, and calendered to prepare an inkjet recording sheet.

The ink jet recording sheets prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were evaluated according to the following method, and the results are shown in Table 1.

[Heat Shrinkage Product and Heat Shrinkage Ratio] The heat shrinkage product and the heat shrinkage ratio are values calculated from the measurement results in the machine direction and the cross machine direction of the base paper.

[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 practically no problem occurs
C was regarded as a problem in practical use.

[Ink Absorption and Sharpness] The ink absorption 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.

[0048]

[Table 1]

From the results of Table 1, comparing Examples 1 to 3 and Comparative Examples 1 and 2, the heat shrinkage ratio RMD of the base paper in the machine direction is RMD.
And the heat shrinkage ratio RCD in the cross machine direction is 0.20 or less, and the ratio RCD / RMD of the heat shrinkage ratios is in the range of 2.3 or less. The sheet had good coatability, and coating unevenness did not occur. In addition, Examples 1 to 3 were all good in terms of ink absorbency and sharpness, which are the characteristics of the inkjet recording sheet. On the other hand, Comparative Example 2 was not preferable because spherical spherical colloidal silica other than the present invention was used.

[0050]

The ink jet recording sheet of the present invention is
The product of the heat shrinkage ratio RMD in the machine direction of the base paper and the heat shrinkage ratio RCD in the cross machine direction is 0.20 or less, and the ratio of the heat shrinkage ratio in the cross machine direction to the machine direction RCD / RMD
Is 2.3 or less and the non-spherical cationic colloidal silica is used in the ink receiving layer composition, whereby the coating property of the ink receiving layer coating liquid is excellent and the coating unevenness on the ink receiving layer surface is excellent. It is a finely coated ink jet recording sheet that does not have and has excellent ink absorption and sharpness.

Claims (3)

[Claims] 1. An ink jet recording sheet comprising an ink receiving layer coated on a base paper, wherein the product of the heat shrinkage ratio RMD in the machine direction and the heat shrinkage ratio RCD in the cross machine direction of the base paper is 0.20 or less. And the ratio RCD / RMD of the heat shrinkage ratio in the cross machine direction to the machine direction is 2.3 or less, and the ink receiving layer composition is a non-spherical cationic colloidal silica as a main component. Inkjet recording sheet. 2. The ink jet recording sheet according to claim 1, wherein a base paper dried with a single tier dryer without open draw is used. 3. The non-spherical cationic colloidal silica comprises:
A needle-shaped or fiber-shaped material.
Or the inkjet recording sheet according to 2.