JPH0761111A - Ink jet recording sheet - Google Patents

Abstract

PURPOSE:To provide a microcoating type ink jet recording sheet having no coating irregularity on the surface of its ink receiving layer, excellent in ink absorbability and sharpness and having rigidity. CONSTITUTION:Raw paper wherein needle leaf tree pulp N with water retention of 1.8-2.3 and broadleaf tree pulp with water retention of 1.1-1.3 are compounded in a wt. ratio N/L of 5/95-20/80 is used and an ink receiving layer is formed on the raw paper using compsn. based on non-spherical cationic colloidal silica to obtain an ink jet recording sheet.

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 is excellent in coatability of a coating liquid for an ink receiving layer due to the smoothness of a base paper and has uneven coating on the surface of the ink receiving layer. The present invention relates to a fine coating type ink jet recording sheet which has no rigidity, is excellent in ink absorption and sharpness, and has rigidity.

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 the multicolor ink jet system can obtain a recording comparable to that of the multicolor printing by the plate making system or the printing by the color photographic system. Furthermore, 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.

Particularly, in recent years, recording sheets printed by an ink jet recording system have been used for price display labels, product display (bar code) labels, quality display labels, and weighing display labels in accordance with diversifying needs. , Labels such as advertising labels (stickers), or CD / AT
It is being used for money-related applications such as M and automatic ticketing machines. In these applications, in addition to various properties of the inkjet recording sheet itself, sufficient rigidity is required.

As a recording sheet used in the ink jet recording system, efforts have been made from the viewpoint of equipment 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 a plain paper type represented by so-called high-quality paper / bonded paper and 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 smoothness of the base paper. That is, by increasing the 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 impart smoothness and rigidity to the base paper,
In a simple adjustment of the freeness level and smoothing by a calender, which are usually carried out, the thickness of the base paper decreases and the rigidity decreases with the smoothing. It was difficult to dramatically improve the smoothness. Alternatively, the improvement of smoothness by using a pulp having excellent flexibility such as sulfite pulp is accompanied by a decrease in strength,
It was inappropriate.

[0008]

As described above, in the slightly coated type ink jet recording sheet, various attempts have been made on the base paper for the purpose of improving the smoothness of the base paper and improving the coatability of the ink receiving layer coating liquid. However, by any of these methods, the desired smoothness, excellent coatability of the ink-receiving layer coating liquid, and to be a base paper for an inkjet recording sheet having sufficient rigidity 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 It is an object of the present invention to obtain an ink jet recording sheet having excellent ink absorbency and sharpness and having rigidity.

[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 ink jet recording sheet having excellent sharpness and rigidity. That is, the ink jet recording sheet of the present invention is an ink jet recording sheet obtained by coating an ink receiving layer on a base paper, and the base paper is a softwood pulp having a water retention of 1.8 to 2.3 and a water retention of 1.1 to. 1.3
The hardwood pulp N and the hardwood pulp L have a weight ratio N / L of 5/95 to 20/8.
The base paper is 0, and the ink receiving layer composition is characterized in that it is a non-spherical cationic colloidal silica as a main component.

In the ink jet recording sheet of the present invention, 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. In the inkjet recording sheet of the present invention, for low density and smooth base paper, selection of raw material pulp, beating degree, adjustment of fiber length, press, calendering conditions, etc., setting of beating state, especially hardwood pulp It was found that the optimization of beating degree and blending amount of softwood pulp is effective.

A series of base papers prepared by mixing a hardwood pulp L and a softwood pulp N having different beating degrees were prototyped, and an optimum combination was searched for the smoothness and rigidity of the base papers. Furthermore, as a result of applying an ink receiving layer to them and evaluating their coatability, ink absorbability as an inkjet recording sheet, sharpness and rigidity, it was revealed that the inkjet recording sheet of the present invention is excellent. became.

Conventionally, in the field of general paper, when a lightly beaten pulp is mixed with a small amount of heavily beaten pulp, the fibrils generated by the heavy beaten reinforce the bonds between the rigid lightly beaten fibers, so that at low density. It is known that paper with high rigidity can be obtained. However, in the case of a base paper for an ink jet recording sheet, smoothness is required in addition to rigidity, so it is necessary to design in consideration of fiber flexibility.

In the ink jet recording sheet of the present invention, water retention is taken as an index of fiber flexibility and beating degree. From the viewpoint of ease of measurement, freeness is preferable, but since freeness is also easily affected by the fiber morphology and chemical composition of pulp, as a method of defining the flexibility of the fiber, which is the central concept of the present invention, I thought it was inappropriate.

The water retention capacity of the present invention is TAPPI standard method UM
It is the value measured according to 256, and after centrifuging the wet pulp pad under the conditions of a temperature of 21 ± 3 ° C. and 900 g (g = gravitational acceleration) for 30 minutes, a pulp having a weight W of water retained in the pulp. Expressed as the ratio W / P to the dry weight P.

In the base paper of the ink jet recording sheet of the present invention, the pulp water retention is 1.8 to 2.3 for the softwood pulp N and 1.1 to 1.3 for the hardwood pulp L having a low content in the base paper. Is. Here, if the water retention of the softwood pulp is less than 1.8, good smoothness and rigidity of the base paper cannot be obtained because the reinforcing effect of the interfiber bond is insufficient, and it is greater than 2.3. In this case, since the shrinkage during drying becomes large, the smoothness of the base paper is deteriorated, and coating unevenness (coating property) is likely to occur. Further, when the water retention of the hardwood pulp L is less than 1.1, the coating unevenness (coating property) and the rigidity are low due to lack of flexibility of the fiber. However, the rigidity is lowered, which is not preferable.

In the base paper of the ink jet recording sheet of the present invention, as a means for controlling the water retention of pulp, equipment usually used for beating pulp, that is, beater, conical refiner, disc refiner and the like can be used. . For the softwood pulp N, it is preferable to select a device or blade type capable of viscous beating.

Examples of the pulp used for the base paper of the ink jet recording sheet of the present invention include kraft pulp, sulfite pulp, chemithermo mechanical pulp and the like. Weight ratio N / L of softwood pulp N and hardwood pulp L
Is preferably in the range of 5/95 to 20/80. Where 5 /
If it is less than 95 or more than 20/80, sufficient effect of improving coatability and rigidity cannot be obtained.

The base paper for the ink jet recording sheet of the present invention contains, if necessary, dyes, fillers, sizing agents, fixing agents, dry paper strengthening agents and the like which are usually used in papermaking. Further, the surface of the raw paper can be coated with starch, polyvinyl alcohol, etc. by a size press or the like.

The ink jet recording sheet of the present invention is a slightly coated type ink jet recording sheet, in which the ink receiving layer is thinly coated on the base paper with a coating amount of 0.5 to 5 g / m ^2, and The fine coating is applied in a state in which the smoothness of No. 1 is reflected as it is, and it has rigidity. The degree of fine coating can be such that the more even the surface of the base paper itself is, the less uneven the coating is. That is, the higher the 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. Further, it becomes possible to make an ink jet recording sheet having rigidity.

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 which 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, hydroxyethyl cellulose and the like. , 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 generally, 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.

In the ink jet recording sheet of the present invention, the above-mentioned base paper may be provided with an ink receiving 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. Thus, an ink receiving layer may be provided.

As a method for coating the ink receiving layer, various blade coaters, roll coaters, air knife coaters, bar coaters, rod coaters, gate roll coaters,
Various devices such as a curtain coater, a short dwell coater, a gravure coater, a flexo gravure coater, and a size press 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, 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 composed of 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 of 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.

[0038]

The ink jet recording sheet of the present invention comprises a softwood pulp N having a water retention of 1.8 to 2.3 and a water retention of 1.1 to 1.
The hardwood pulp L of No. 3 was blended so that the weight ratio N / L of the softwood pulp N and the hardwood pulp L was 5/95 to 20/80, and a non-spherical cation as a main component on the raw paper. By applying an ink-receiving layer made of colloidal silica, the coating properties of the ink-receiving layer coating liquid are excellent, there is no coating unevenness on the ink-receiving layer surface, and the ink absorbency and sharpness are excellent, and the rigidity is high. It is possible to make a fine coating type ink jet recording sheet having.

[0039]

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] A softwood pulp NBKP beaten to a water retention of 1.8 with a double disk refiner and a hardwood pulp LBKP beaten to a water retention of 1.2 were used in a weight ratio N /.
A mixed pulp was prepared by mixing so that L was 10/90.

Next, to 100 parts of each pulp, 7 parts of light calcium carbonate (TP121, manufactured by Okutama Kogyo Co., Ltd.), 0.1 part of alkyl ketene dimer sizing agent (Hacon 11-2, manufactured by Dick Hercules Co., Ltd.),
A base paper having a basis weight of 85 g / m ² was produced with a Fourdrinier paper machine using a stock containing 0.7 parts of amphoteric starch (Kate 3210, manufactured by Oji National Co., Ltd.). The paper after drying with a multi-cylinder dryer is size-pressed with a 3% aqueous solution of oxidized starch, and after drying, the thickness is adjusted with a machine calendar so that the density becomes 0.85 g / cm ³ , and an inkjet recording sheet. The base paper for

[Preparation of Inkjet Recording Sheet] The base paper for inkjet recording sheet prepared as described above is
As an ink receiving layer composition, needle-like colloidal silica is about 6 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 2% by weight of aluminum oxide hydrate (particle size; width 10 to 20 nm x length 50 to 200 nm) 100
0 part, 300 parts of 10% aqueous solution of polyvinyl alcohol (PVA 117, Kuraray Co., Ltd.) as an adhesive, 60% aqueous solution of cationic resin as a dye fixing agent (Polyfix 601, cation charge amount 6.9 meq./g, Showa High) (Molecular Co., Ltd.) An aqueous dispersion containing 50 parts as a main component and having a solid content concentration of 10% is coated and dried using a rod coater at a coating speed of 300 m / min to a solid content of 1 g / m ^2. Then, it was calendered to prepare an inkjet recording sheet.

Example 2 The water retention of the NBKP used in Example 1 was 2.0.
Except for the above, a base paper was manufactured in the same manner as in Example 1 to manufacture an inkjet recording sheet.

Example 3 The water retention of the NBKP used in Example 1 was 2.3.
Except for the above, a base paper was manufactured in the same manner as in Example 1 to manufacture an inkjet recording sheet.

Comparative Example 1 The water retention of the NBKP used in Example 1 was 1.7.
Except for the above, a base paper was manufactured in the same manner as in Example 1 to manufacture an inkjet recording sheet.

Comparative Example 2 The water retention of the NBKP used in Example 1 was 2.4.
Except for the above, a base paper was manufactured in the same manner as in Example 1 to manufacture an inkjet recording sheet.

The ink jet recording sheets prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were evaluated by the following evaluation methods, and the results are summarized in Table 1.

[Smoothness] Smoothness is the British Standard Method 6563.
The smoothness is measured by a Parker Print Surf (manufactured by Lorenzen Co., Ltd.) under the conditions of a measuring pressure of 10 kg / cm ² and a hard material used as a pressure plate, and the smaller value (μm) is smoother.

[Rigidity] The rigidity is defined by JIS P8143.
Clark was measured according to the stiffness of the value (cm ^3/00)
In it, in order to obtain a good running property in an inkjet printer, when a base paper basis weight of the ink jet recording sheet of 85 g / m ^2, in the longitudinal direction 105 cm ^3/100 or more, more preferably requires 115cm ^3/100 or more is there.

[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 Absorption and Sharpness] The ink absorption and the sharpness of the image are determined by the boundaries 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.

[0052]

[Table 1]

Example 4 In Example 1, the water retention of NBKP was set to 2.0 and LBKP was used.
An ink jet recording sheet was prepared by producing a base paper in the same manner as in Example 1 except that the water retention of was set to 1.1.

Example 5 In Example 1, the water retention of NBKP was set to 2.0 and LBKP
An ink jet recording sheet was prepared by producing a base paper in the same manner as in Example 1 except that the water retention of was set to 1.3.

Comparative Example 3 An ink jet recording sheet was prepared by producing a base paper in the same manner as in Example 4, except that the water retention of LBKP was changed to 1.0.

Comparative Example 4 An ink jet recording sheet was prepared by producing a base paper in the same manner as in Example 4 except that the water retention of LBKP was changed to 1.4.

The ink jet recording sheets prepared in Examples 4 to 5 and Comparative Examples 3 to 4 were evaluated by the above evaluation method, and the results are shown in Table 2.

[0058]

[Table 2]

Example 6 [Preparation of base paper] NBKP of Example 1 having a water retention of 2.0
And LBKP with water retention of 1.2, NBKP and L
A base paper for an inkjet recording sheet was produced in the same manner as in Example 1 except that the weight ratio N / L of BKP was changed to 5/95.

[Preparation of Inkjet Recording Sheet] The base paper for 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.

Example 7 In Example 6, NBKP having a water retention of 2.0 and water retention of 1.
Weight ratio N of NBKP and LBKP for 2 LBKP
A base paper for an ink jet recording sheet was produced in the same manner as in Example 6 except that / L was changed to 20/80 to produce an ink jet recording sheet.

Comparative Example 5 In Example 6, NBKP having a water retention of 2.0 and water retention of 1.
Weight ratio N of NBKP and LBKP for 2 LBKP
A base paper for an inkjet recording sheet was produced in the same manner as in Example 6 except that / L was changed to 3/97 to produce an inkjet recording sheet.

Comparative Example 6 In Example 6, NBKP having a water retention of 2.0 and water retention of 1.
Weight ratio N of NBKP and LBKP for 2 LBKP
A base paper for an inkjet recording sheet was manufactured in the same manner as in Example 6 except that / L was changed to 30/70, and an inkjet recording sheet was manufactured.

Comparative Example 7 Using the base paper for an ink jet recording sheet prepared in Example 7, a 40% aqueous dispersion of spherical colloidal silica (primary particle diameter 300 ± 30 n) was used as an ink receiving layer composition.
m) 250 parts, 300 parts of an aqueous solution of polyvinyl alcohol (PVA 117, manufactured by Kuraray Co., Ltd.) as an adhesive, 60% aqueous solution of a cationic resin as a dye fixing agent (Polyfix 601, cation charge amount 6.9 meq./g, Showa High) (Molecular Co., Ltd.) 50 parts of an aqueous dispersion having a solid content of 10% as a main component is applied at a coating speed of 30 using a gate roll coater.
An ink jet recording sheet was prepared by coating and drying so as to give a dry solid content of 2 g / m ² at 0 m / min and calendering.

The ink jet recording sheets prepared in Examples 6 to 7 and Comparative Examples 5 to 6 were evaluated by the above evaluation method, and the results are shown in Table 3.

[0066]

[Table 3]

From the results shown in Table 1, when the water retention of the softwood pulp is 1.8 to 2.3, an ink jet recording sheet having good coatability and rigidity, ink absorbability and sharpness can be obtained. It was However, when the water retention is less than 1.8 or more than 2.3 and large, coating unevenness occurs and the rigidity is poor.

From the results of Example 2 and Table 2, when the water retention of the hardwood pulp is less than 1.1, coating unevenness occurs and the rigidity is insufficient, and when it exceeds 1.3, the base paper density is high. Since it increased, the rigidity decreased, which was not preferable. Therefore, when the water retention of the hardwood pulp is 1.1 to 1.3,
It is clear that an ink jet recording sheet having good coatability and rigidity, ink absorbability and sharpness can be obtained.

From the results of Example 2 and Table 3, by comparing Examples 2 and 6 and 7 with Comparative Example 5 and Comparative Example 6, the weight ratio N / of the softwood pulp and the hardwood pulp was N /
When L was in the range of 5/95 to 20/80, it was possible to obtain an inkjet recording sheet excellent in coatability and rigidity, ink absorbability and sharpness.

Comparative Example 7 is an example in which the composition other than the present invention was used in place of the ink receiving layer composition used in Example 7, but other characteristics were excellent but the sharpness was poor. It was

[0071]

As described above, in the ink jet recording sheet of the present invention, a softwood pulp N having a water retention of 1.8 to 2.3 and a hardwood pulp L having a water retention of 1.1 to 1.3 are prepared from each pulp. By using the base paper containing the weight ratio N / L in the range of 5/95 to 20/80, there is no coating unevenness on the surface of the ink receiving layer, the ink absorbability and the sharpness are excellent, and the fine coating is rigid. An engineering type ink jet recording sheet was obtained.

Claims (2)

[Claims] 1. An ink jet recording sheet comprising a base paper coated with an ink receiving layer, the base paper comprising softwood pulp having a water retention of 1.8 to 2.3 and water retention of 1.1 to 1.3.
The hardwood pulp N and the hardwood pulp L have a weight ratio N / L of 5/95 to 20/8.
An ink jet recording sheet, wherein the base paper is 0 and the ink receiving layer composition is a non-spherical cationic colloidal silica as a main component. 2. The non-spherical cationic colloidal silica comprises:
A needle-shaped or fiber-shaped material.
The inkjet recording sheet described.