JP2003285541A - Recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recording sheet for full color record which is excellent in ink absorbency, has a high printing density and a moderate gloss, and is also excellent in color and image reproducibility in respect to both dye ink and pigment ink, in printing by an ink jet recorder. <P>SOLUTION: In the ink jet recording sheet provided with an ink receiving layer on the surface of a substrate, a gloss developing layer mainly composed of an inorganic fine particle is provided as the uppermost layer of the recording sheet, and also the ink receiving layer composed of at least two layers of synthetic amorphous silica are formed beneath the gloss developing layer. The synthetic amorphous silica is disposed so as to reduce its average particle size sequentially from the lower layer of the ink receiving layers toward the upper layer thereof. <P>COPYRIGHT: (C)2004,JPO

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 a method for producing the same, and more specifically, the image density recorded on the ink jet recording sheet is high regardless of whether dye ink or pigment ink is used. The present invention relates to an inkjet recording sheet having an appropriate gloss.

[0002]

2. Description of the Related Art The ink jet recording system is one in which minute droplets of ink are ejected according to various operating principles and adhered to a recording sheet such as paper to record images, characters, etc., but at high speed and low noise. It has features of easy multicoloring, great flexibility of recording patterns, no need for development and fixing, and as a recording device for various figures and color images including Chinese characters.
It is rapidly spreading in various applications. Furthermore, images formed by the multi-color inkjet system can obtain records that are comparable to multi-color printing by the plate-making system and printing by the color photographic system. Since it is cheaper than the technology, it is being widely applied to the field of full-color image recording.

A recording sheet used in this ink jet recording system has a high density of print dots, a bright and vivid color tone, and ink flows quickly and bleeds even when the print dots overlap each other. It is required that the horizontal diffusion of print dots is not unnecessarily large and that the periphery is smooth and does not blur.

Several proposals have been made to date to solve these problems. For example, JP-A-52-530
Japanese Unexamined Patent Publication No. 12 discloses an inkjet recording paper obtained by wetting a low-sized base paper with a paint for surface processing. Further, JP-A-55-5830 discloses an ink jet recording sheet having an ink-absorbent coating layer on the surface of a support, and JP-A-55-51583 and JP-A-56-157. In Japanese Patent Laid-Open No. 55-11829, there is disclosed an example of a smear paper using a two-layer structure having different ink absorption speeds. ing.

In general, an ink jet recording sheet is provided with an ink receiving layer having an ink absorbing property to which a porous pigment is applied to control the color and sharpness which determine the image quality, and to improve the color reproducibility and the image reproducibility. We are trying to improve. The ink receiving layer having ink absorbability needs to have many voids in the ink receiving layer in order to absorb and retain the ink. However, in the ink receiving layer with many voids, the incident light to the ink receiving layer is scattered and the transmission is obstructed, making it opaque, and it becomes difficult for light to reach the ink that has penetrated into the voids, and the image becomes whitish. , Color reproducibility and color density are reduced. Further, since the ink receiving layer having many voids has a porous surface, it is difficult to obtain high gloss.

As an ink jet recording sheet having high gloss, for example, in JP-A-61-197285, a porous ink receiving layer is formed on a transparent support, and an image formed on the ink receiving layer is described. A method of observing from the support side has been proposed. JP-A No. 3-215081 discloses that a dye adsorption layer made of porous alumina hydrate and a solvent absorption layer made of porous fine powder silica are sequentially laminated on a transparent support, and an image formed on the dye adsorption layer. There has been proposed a method of observing the above from the support side. However, in these methods, when printing an image, it is necessary to perform image processing so that it becomes a mirror image,
Furthermore, the support used is limited to one having transparency.

Proposals have been made to develop gloss in an ink jet recording sheet by using colloidal silica. Japanese Patent Application Laid-Open No. 2-274587 discloses a method of using colloidal silica for the purpose of improving gloss, treating with an aqueous solution containing a cationic polymer electrolyte, and then casting.
However, when the cationic polymer electrolyte is used, the surface of the printed portion is likely to be roughened because the cationic polymer electrolyte existing on the surface at the time of printing redissolves the ink.

Colloidal silica is generally an anionic colloidal dispersion in which ultrafine particles of silicic acid anhydride (silica) are stably dispersed in water. The most common method for producing colloidal silica is a method using an ion exchange resin, in which a sodium silicate aqueous solution is passed through a cation exchange resin to form a sol having SiO ₂ / Na ₂ O of 60 to 130, which is 60 ° C. Heat aging to grow to independent dispersed particles,
This is a method in which a sol that has passed through the ion-exchange resin layer is newly added to polymerize and deposit the sol to grow it to an average particle diameter of 3 to 200 nm to form a stable sol. Silica sols have a cyclosan structure and usually give each particle of silica a sufficient negative charge (anionic character) so that they repel each other.

Further, a proposal using colloidal silica treated with an inorganic cation has been made. The inorganic cation-treated colloidal silica is generally obtained by reacting silica with a compound of a polyvalent metal ion such as aluminum ion, and at least the surface of silica particles is cationically charged.

Japanese Unexamined Patent Publication No. 7-101142 proposes a method of coating cationic colloidal particles and synthetic polymer latex on an ink receiving layer. The cationic colloidal particles used here are those treated with an inorganic cation. In the case where the colloidal particles treated with the inorganic cation and the synthetic polymer latex are used in combination, a glossy feeling is obtained, and the color developability of the dye ink is good, but the color developability of the pigment ink is poor. I will end up.

There are recording papers, films, etc. coated with a resin that absorbs ink by dissolving and swelling for the purpose of imparting gloss, but those that try to absorb ink by dissolving and swelling such resin are: Although gloss is obtained, the absorption and drying of ink are slow, and the problem of stains and bleeding due to ink transfer becomes a problem.

In the ink for ink jet recording, a dye which is a coloring agent is soluble in water which is a medium, and a dye ink which is present in the ink medium in a molecular state and pigment particles which are a coloring material are medium. There are two types of pigment inks that exist in the state of being dispersed in certain water. Although dye ink has high color development,
Although the pigment ink is inferior in light resistance and the coloring property is lower than that of the dye ink, the light resistance tends to be improved.

In the dye ink, the coloring material penetrates the recording medium, whereas in the pigment ink, a large amount of pigment particles, which are the coloring material, remain on the surface of the recording medium. In the conventional ink jet recording sheet, both the dye ink and the pigment ink having different characteristics as described above have excellent ink absorbency, it is difficult to obtain a high print density, and it is not possible to obtain a satisfactory quality.

[0014]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to print in an ink jet recording apparatus, have excellent ink absorbency, have a high printing density and an appropriate gloss, and further reproduce color with both dye ink and pigment ink. An object of the present invention is to provide an inkjet recording sheet for full-color recording, which has excellent properties and image reproducibility.

[0015]

Means for Solving the Problems As a result of intensive investigations by the present inventors regarding an ink jet recording sheet,
The inventors have invented an ink jet recording sheet that solves the above problems. That is, the present invention is an ink jet recording sheet comprising an ink-receiving layer on the support surface, a glossy layer mainly comprising the inorganic fine particles in the uppermost layer of the recording sheet is provided, and under the glossy layer At least 2
A sheet for ink jet recording, characterized in that a synthetic amorphous silica-containing ink receiving layer consisting of layers is formed, and the average particle size of the synthetic amorphous silica is gradually reduced from the lower layer to the upper layer of each ink receiving layer. .

In one embodiment of the present invention, the average particle size of synthetic amorphous silica in the lowermost layer of the ink receiving layer is 10 or less.
The average particle diameter in the uppermost layer of the ink receiving layer is 1 to 10 μm. Another embodiment is that the inorganic fine particles are colloidal silica or alumina sol or alumina-doped silica, and the average particle diameter of the inorganic fine particles is 5 to 500 nm. Furthermore, in another embodiment, the gloss-developing layer mainly composed of inorganic fine particles has an absolute dry coating amount of 5 to 25 g / m ² , and the ink-receiving layer has an absolute dry coating amount of 5 to 25 g / m ^2. Is included. Another embodiment is JI.
The specular gloss of 75 degrees specified in S P8142 is 20 to
It includes 90%. An inkjet recording sheet in which the inorganic fine particles are organic cation-treated colloidal silica and the average particle diameter of the inorganic fine particles is 5 to 500 nm is also an embodiment of the present invention.

The synthetic amorphous silica used in the present invention is
From the viewpoint of ink absorbency and glossiness, it is preferable that the average particle size of the plural ink receiving layers to be laminated be successively decreased from the lower layer to the upper layer. When the average particle size of the synthetic amorphous silica is increased from the lower layer to the upper layer of the ink receiving layer in order, the ink absorbing property is good, but the gloss developing layer is roughened and a sufficient gloss cannot be obtained. When the synthetic amorphous silica has the same average particle size in the lower layer and the upper layer of the ink receiving layer, the size of the average particle size of the synthetic amorphous silica is limited, and ink absorbency and glossiness cannot be achieved at the same time. For example, if the ink receiving layers are provided in the lower layer and the upper layer by using only the synthetic amorphous silica having the same average particle size, the glossiness is good but the ink absorbability is poor. Further, when only the synthetic amorphous silica having the same relatively large average particle diameter is used and the ink receiving layers are provided in the lower layer and the upper layer, the ink absorbability is good, but the glossiness is poor.

In the ink jet recording sheet of the present invention,
A gloss expressing layer mainly composed of inorganic fine particles is provided on the uppermost layer, and an ink receiving layer consisting of at least two layers is formed under the gloss expressing layer, and an average of synthetic amorphous silica is formed from the lower layer to the upper layer of the ink receiving layer. By laminating the particles so that the particle diameters become smaller in sequence, the contradictory properties of improving glossiness and ensuring ink absorption can be balanced. Thus, while improving the ink absorbability from the lowermost layer to the uppermost layer of the ink receiving layer, the uppermost layer of the ink receiving layer maintains its surface smoothness and complements the improved glossiness of the gloss expressing layer. It has an effect.

The average particle size of the synthetic amorphous silica in the lowermost layer of the ink receiving layer is preferably 10 to 20 μm, more preferably 12 to 16 μm. Average particle size is 1
If it is less than 0 μm, the ink absorbency is inferior, and if it is more than 20 μm, the surface becomes rough and there is a feeling of roughness, which is not preferable in terms of image sharpness. The average particle size of the synthetic amorphous silica in the uppermost layer of the ink receiving layer is preferably 1 to 10 μm, more preferably 4 to 8 μm. If the average particle size is smaller than 1 μm, the ink absorbency is poor and the average particle size is 10 μm.
If it is larger than m, there is a problem that the glossiness is inferior. That is, an ink receiving layer consisting of at least two layers is formed under the gloss developing layer, and the average particle diameter of the synthetic amorphous silica in the lowermost layer of the ink receiving layer is 10 to 20 μm, and the uppermost layer of the ink receiving layer. The average particle size of the synthetic amorphous silica in 1) is 1 to 10 μm. By appropriately combining the average particle size of the synthetic amorphous silica from the lower layer to the upper layer of the ink receiving layer, It is possible to improve the ink absorbency and the gloss of the gloss developing layer.

As the inorganic fine particles in the gloss developing layer,
Colloidal silica or alumina sol or alumina-doped silica is preferred. More preferably, colloidal silica treated with an organic cation is preferable. The colloidal silica treated with an organic cation is generally obtained by reacting silica with an organic cationic compound having an organic cationic group such as a primary to tertiary amine group and a quaternary ammonium salt group. At least the surface of silica is cationically charged.

Specific examples of the compound having an organic cationic group and used for treating the organic cation of colloidal silica include polyethyleneimine, polyvinylpyridine, polyamine sulfone, polydialkylaminoethyl methacrylate, polydialkylaminoethyl. Acrylate, polydialkylaminoethylmethacrylamide,
Compounds such as polydialkylaminoethylacrylamide, polyepoxyamine, polyamidoamine, dicyandiamide-formalin condensate, dicyandiamide polyalkyl-polyalkylenepolyamine condensate, polyvinylamine, polyallylamine and their hydrochlorides, and polydimethyldiallylammonium chloride and Examples thereof include copolymers of acrylamide and the like, polydiallylmethylamine hydrochloride, polymethacrylic acid ester methyl chloride quaternary salt and the like. It is unclear why both dye ink and pigment ink exhibit high color development and image sharpness when the gloss-developing layer according to the present invention contains an organic cation-treated colloidal silica. However, the inkjet ink has an anionic property, and due to the ionic attraction between the anionic coloring material in the ink and the cationic surface of the organic cation-treated colloidal silica in the gloss development layer, It is presumed that one of the factors is that a large amount of the color material is gathered on the gloss developing layer or the ink receiving layer.

The average particle size of the inorganic fine particles is 5 to 500 n.
m is preferable, and more preferably 20 to 300 nm. If the average particle size is less than 5 nm, the glossiness is high, but the ink absorbency is poor. If the average particle size is more than 500 nm, the ink absorbency is good, but the glossiness is difficult to obtain.

Examples of the bone-dry coating amount of the glossy layer mainly comprising the inorganic fine particles is preferably from 5 to 25 g / ^{m 2,} more preferably from 7~18g / ^{m 2.} If the absolutely dry coating amount of the gloss-developing layer is less than 5 g / m ² , there is a problem that sufficient gloss cannot be obtained. Absolute dry coating amount 25g / m ²
If the amount is larger, a good glossiness can be obtained, but the gloss-developing layer is likely to be cracked, resulting in a problem in image sharpness, and an excessive dry coating amount causes a cost problem.

The absolute dry coating amount of the ink receiving layer is 5 to 25 g.
/ M ² is preferable, and more preferably 10 to 20 g / m
It is ² . If the absolute dry coating amount of the ink receiving layer is less than 5 g / m ² , there is a problem that the ink absorbency is poor. If the absolute dry coating amount of the ink receiving layer is more than 25 g / m ² , the effect of ink absorption is saturated, and as with the gloss developing layer, the excessive dry coating amount causes a cost problem.

The 75-degree specular gloss is preferably 20 to 90%, more preferably 30 to 70%. When the glossiness is lower than 20%, the visual glossiness is insufficient, and when the glossiness is higher than 90%, a glaring feeling is strong, which is not preferable.

In the ink jet recording sheet of the present invention, when the gloss developing layer is applied onto the ink receiving layer and dried,
Although it already has gloss, it is possible to give high gloss by calendering. The calendering can be finished using a calendering machine such as a machine calender, a TG calender, a super calender, and a soft calender.

In order to improve the glossiness, the formation of the glossy layer mainly composed of the inorganic fine particles may be obtained by a cast treatment. The cast treatment is a processing method in which the glossy layer is pressed to a heated mirror-finished roll in a swollen state to give a mirror-like finish. Examples of the cast treatment in the present invention include a direct method, a gelation method, a rewet method and the like.

Further, in order to improve the glossiness, the formation of the gloss developing layer mainly composed of the inorganic fine particles of the present invention is carried out by swelling the gloss developing layer and bringing a smooth film into close contact with the film to remove and remove it to give a mirror finish. May be obtained by

In the case where the coating strength cannot be obtained only by the inorganic fine particles in the gloss developing layer, it is necessary to use the binder in combination. When the amount of the binder is too large, the binder component becomes the main component and the ink absorbability is deteriorated.
It is preferably part by weight, more preferably 3 to 15 parts by weight.

Examples of the binder include polyvinyl alcohol, casein, soybean protein, synthetic proteins,
Starch, cellulose derivatives such as carboxymethylcellulose and methylcellulose, urethane, polyvinylpyrrolidone, acrylic, vinyl acetate, ethylene vinyl acetate,
The binder is not particularly limited as long as it is a binder such as a styrene-acrylic copolymer, styrene, or latex that can be generally used for coated paper. Of these, polyvinyl alcohol is preferable.

Further, in the gloss-developing layer, first grade, second grade or 3 grade
By using a cationic dye fixing agent such as a primary amine salt or a quaternary ammonium salt, the color developability and fixability of the ink can be further improved.

The pigment of the ink receiving layer in the present invention includes
Synthetic amorphous silica, which has good ink absorption and high printing clarity, is desirable. However, other pigments may be used in combination as long as sufficient ink absorbency can be maintained. Examples of the pigment include various pigments publicly known and used in the general coated paper field, such as kaolin, clay, calcined clay, calcium carbonate, and aluminum hydroxide.

In order to obtain coating strength in the ink receiving layer, it is necessary to use a binder in combination. When the amount of the binder is too large, the binder component becomes the main component and the ink absorbability is deteriorated.
The amount is preferably 10 to 100 parts by weight, more preferably 25 to 75 parts by weight.

Examples of the binder used in the ink receiving layer include polyvinyl alcohol, casein, soybean protein, synthetic proteins, starch, cellulose derivatives such as carboxymethylcellulose and methylcellulose, urethane, polyvinylpyrrolidone, acryl, vinyl acetate, ethylene acetic acid. The binder is not particularly limited as long as it is a binder such as vinyl, styrene-acrylic copolymer, styrene, and latex which can be generally used for coated paper. Of these, polyvinyl alcohol is preferable.

The ink receiving layer is a coating layer which is provided adjacent to the gloss developing layer and between the support and absorbs the solvent component in the ink. The solvent component is removed from the gloss developing layer by the ink receiving layer, and the problem of ink overflow can be avoided.

The ink receiving layer according to the present invention preferably contains a water-soluble binder. When the binder is present, the adhesiveness is developed at the interface between the gloss developing layer and the ink receiving layer, and the securing of the adhesiveness at the interface is improved. The reason for the development of this adhesiveness is not clear, but since the coating composition for the ink receiving layer uses water as the dispersion medium, when the gloss developing layer is applied, the dispersion medium is It is considered that it penetrates into the ink receiving layer, redissolves the water-soluble binder in the ink receiving layer, adheres to the gloss developing layer, and secures strength at the interface.

Further, as an additive to the ink receiving layer,
Dye fixing agent, pigment dispersant, thickener, fluidity improver, defoaming agent, foam suppressor, penetrant, coloring dye, coloring pigment, fluorescent whitening agent, ultraviolet absorber, antioxidant, preservative, An anti-fungal agent, a water-proofing agent, a wet paper strength enhancer, a dry paper strength enhancer and the like can also be appropriately added.

The method for coating or impregnating the gloss-developing layer and the ink-receiving layer according to the present invention is used in machines such as various blade coaters, roll coaters, air knife coaters, bar coaters, rod blade coaters and curtain coaters. be able to.

Further, in order to impart curl suitability, it is possible to coat a back coat layer on the surface opposite to the ink receiving layer side sandwiching the support.

As the support used in the present invention, paper, film, non-woven fabric or a composite thereof can be generally used, but the support is not particularly limited thereto.

[0041]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In addition, "parts" and "%" shown in the examples mean absolute dry weight parts and absolute dry weight% unless otherwise specified.

In the following Examples and Comparative Examples, a commercially available high-quality paper was used as the support, and the support was common.
The inkjet recording sheets obtained in the present invention were all evaluated after being processed with a super calendar (linear pressure: 100 Kg / cm).

Example 1 Formation of Bottom Layer of Ink Receiving Layer: The bottom layer of the ink receiving layer was coated on the surface of the support. The coating composition for the ink receiving layer was composed of 100 parts of synthetic amorphous silica (Mizukasil P-78D: manufactured by Mizusawa Chemical Industry Co., Ltd.) having an average particle diameter of 12 μm and 35 parts of polyvinyl alcohol (PVA-117: manufactured by Kuraray Co., Ltd.). These were prepared by adding water to obtain a solid content of 15%. This liquid was applied so that the absolute dry coating amount was 6 g / m ² . Forming the uppermost layer of the ink receiving layer: The uppermost layer of the ink receiving layer was applied to the surface of the lowermost layer of the ink receiving layer. The coating composition for the ink receiving layer is a synthetic amorphous silica having an average particle size of 6 μm (Mizukasil P-78A: manufactured by Mizusawa Chemical Industry Co., Ltd.).
00 parts and 35 parts of polyvinyl alcohol (PVA-117: manufactured by Kuraray Co., Ltd.) were used to prepare a solution having a solid content of 15% by adding water. This liquid is absolutely dry coating amount 6g / m
^It was coated so as to be ² . Forming a gloss-developing layer: Colloidal silica (Cab-O-Sperse) treated with an organic cation which is an inorganic fine particle.
PG022: 100 parts of Cabot Specialty Chemicals, Inc., polyvinyl alcohol (PV
A-117: Kuraray Co., Ltd.) 5 parts, cationic dye fixing agent (Sumireds resin 1001: Sumitomo Chemical Co., Ltd.) 5 parts were used to prepare a solid content of 15% by addition of water, and these were dried and dried. The coating amount was 10 g / m ² . Calendar treatment was carried out under the condition of a linear pressure of 100 kg / cm so that the coated surface of the glossy layer contacted the chilled rolls to obtain an inkjet recording sheet of the present invention.

Example 2 The synthetic amorphous silica in the lowermost layer of the ink receiving layer was a synthetic amorphous silica having an average particle diameter of 18 μm (Mizukasil P-78F:
An inkjet recording sheet of the present invention was obtained in the same manner as in Example 1 except that the amount was 100 parts.

Example 3 The present invention was carried out in the same manner as in Example 1 except that 100 parts of anionic colloidal silica (Cab-O-Sperse PG002: manufactured by Cabot Specialty Chemicals, Inc.) was used as the inorganic fine particles in the gloss developing layer. To obtain an inkjet recording sheet.

Example 4 In Example 3, the synthetic amorphous silica in the lowermost layer of the ink receiving layer was 100 parts of synthetic amorphous silica (Mizukasil P-78F, manufactured by Mizusawa Chemical Industry Co., Ltd.) having an average particle diameter of 18 μm. An inkjet recording sheet of the present invention was obtained in the same manner as in Example 1 except for the above.

Example 5 Alumina-doped silica (VP
(3375: manufactured by Nippon Aerosil Co., Ltd.) An inkjet recording sheet of the present invention was obtained in the same manner as in Example 1 except that the amount was 100 parts.

Example 6 In Example 5, the synthetic amorphous silica in the lowermost layer of the ink receiving layer was 100 parts of synthetic amorphous silica (Mizukasil P-78F: manufactured by Mizusawa Chemical Industry Co., Ltd.) having an average particle diameter of 18 μm. An inkjet recording sheet of the present invention was obtained in the same manner as in Example 1 except for the above.

Example 7 The bottom layer of the ink receiving layer had an absolute dry coating amount of 5 g / m ² , the top layer of the ink receiving layer had an absolute dry coating amount of 5 g / m ² , and the gloss developing layer had an absolute dry coating amount. An inkjet recording sheet of the present invention was obtained in the same manner as in Example 1 except that the amount was 8 g / m ² .

Example 8 Absolute dry coating amount of the lowermost layer of the ink receiving layer was 10 g / m ^2, and absolute dry coating amount of the uppermost layer of the ink receiving layer was 8 g / m ² , and absolutely dry coating of the gloss developing layer. An inkjet recording sheet of the present invention was obtained in the same manner as in Example 1 except that the amount was 15 g / m ² .

Comparative Example 1 Example 1 was repeated except that the synthetic amorphous silica in the lowermost layer of the ink receiving layer was changed to 100 parts of the synthetic amorphous silica having an average particle size of 6 μm (Mizukasil P-78A, manufactured by Mizusawa Chemical Industry Co., Ltd.). An inkjet recording sheet of the present invention was obtained in the same manner as.

Comparative Example 2 In Comparative Example 1, 100 parts of the synthetic amorphous silica of the uppermost layer of the ink receiving layer was 100 parts of synthetic amorphous silica (Mizukasil P-78D: manufactured by Mizusawa Chemical Industry Co., Ltd.) having an average particle diameter of 12 μm. An inkjet recording sheet of the present invention was obtained in the same manner as in Example 1 except for the above.

Comparative Example 3 In Comparative Example 1, the synthetic amorphous silica in the uppermost layer of the ink receiving layer was 100 parts of synthetic amorphous silica (Mizukasil P-78F, manufactured by Mizusawa Chemical Industry Co., Ltd.) having an average particle diameter of 18 μm. An inkjet recording sheet of the present invention was obtained in the same manner as in Example 1 except for the above.

Comparative Example 4 In Comparative Example 2, the synthetic amorphous silica in the lowermost layer of the ink receiving layer was 100 parts of synthetic amorphous silica having an average particle diameter of 12 μm (Mizukasil P-78D, manufactured by Mizusawa Chemical Industry Co., Ltd.). An inkjet recording sheet of the present invention was obtained in the same manner as in Example 1 except for the above.

Comparative Example 5 In Comparative Example 4, the synthetic amorphous silica of the uppermost layer of the ink receiving layer was 100 parts of synthetic amorphous silica (Mizukasil P-78F, manufactured by Mizusawa Chemical Industry Co., Ltd.) having an average particle diameter of 18 μm. An inkjet recording sheet of the present invention was obtained in the same manner as in Example 1 except for the above.

Comparative Example 6 In Comparative Example 5, 100 parts of the synthetic amorphous silica in the lowermost layer of the ink receiving layer was 100 parts of synthetic amorphous silica (Mizukasil P-78F, manufactured by Mizusawa Chemical Industry Co., Ltd.) having an average particle diameter of 18 μm. An inkjet recording sheet of the present invention was obtained in the same manner as in Example 1 except for the above.

Comparative Example 7 In Comparative Example 5, the inorganic fine particles in the gloss developing layer were anionic colloidal silica (Cab-O-Sperse PG).
(002: manufactured by Cabot Specialty Chemicals, Inc.), and an ink jet recording sheet of the present invention was obtained in the same manner as in Example 1.

Comparative Example 8 In Comparative Example 5, the inorganic fine particles of the gloss developing layer were alumina-doped silica (VP3375: Nippon Aerosil Co., Ltd.) 1
An ink jet recording sheet of the present invention was obtained in the same manner as in Example 1 except that the amount was changed to 00 parts.

Evaluation method: The inkjet recording sheets obtained in Examples 1 to 8 and Comparative Examples 1 to 8 were evaluated for glossiness, sharpness of printed images, ink absorbency and surface strength by the following methods. Regarding the sharpness of the printed image, the ink absorbency, and the print density, PM-9000 manufactured by Epson, which is an inkjet plotter of dye ink, and M manufactured by Epson, which is an inkjet plotter of pigment ink, is used.
Recording was performed with a C-10000 machine and evaluated. The obtained results are shown in Tables 1 and 2.

Glossiness: Regarding the white background of the ink jet recording sheet, according to the method of JIS Z 8741,
The specular glossiness at an incident angle of 75 degrees was measured with a gloss meter (GM-26D, manufactured by Murakami Color Research Laboratory).

Strength: The coated surface was rubbed with a finger to evaluate powder falling. ⊚: There is no powder drop on the coated surface, and it is very good because it does not adhere to the fingers. ◯: There is little powder falling off on the coated surface, and it is good because it does not adhere much to the fingers. Δ: The coated surface had some powder falling off and was slightly attached to the finger. X: There are many powder drops on the coated surface, and they also adhere to the fingers.

Sharpness of printed image: Printing was performed with a PM-9000 machine and an MC-10000 machine, and the sharpness of the printed image was visually evaluated. ⊚: The printed image is very clear and the contrast is clear. ◯: The printed image is clear and has contrast. Δ: The printed image is clear, but the contrast is not so clear, and it is slightly blurred. X: The printed image is not clear and is slightly blurred.

Ink absorptivity: In order to evaluate the ink absorptivity, a high-quality paper is attached to the printed surface every 5 seconds immediately after printing, and whether or not the ink is transferred to the high-quality paper is observed. Measure the time until no transfer occurs at all. The measured number of seconds was evaluated in four levels as follows. ⊚: No transfer occurs within 5 seconds immediately after printing. Good: No transfer at all for 5 seconds or more and less than 10 seconds. Δ: Not transferred at all for 10 or more and less than 30 seconds. X: Transferred for 30 seconds or more.

Print density: The print density of a solid black portion was measured with a reflection densitometer (RD-918 manufactured by Gretag Macbeth Co.).

[0065]

[Table 1]

[0066]

[Table 2]

As is clear from the results of Tables 1 and 2,
The inkjet recording sheets obtained by the examples of the present invention were excellent in ink absorbency, had high printing density and appropriate gloss, and were excellent in color reproducibility and image reproducibility with both dye ink and pigment ink. It was a thing.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shintaro Isa             1-6-6 Minami, Tsubame City, Niigata Prefecture F-term (reference) 2C056 EA04 FC06                 2H086 BA16 BA33 BA41 BA45

Claims (6)

[Claims] 1. A ink-receiving layer in an ink jet recording sheet formed by providing a support surface, a glossy layer mainly composed of the top layer to the inorganic fine particles of the recording sheet is provided, and at least under the glossy layer An ink jet recording sheet, characterized in that a synthetic amorphous silica-containing ink receiving layer comprising two layers is formed, and the average particle size of the synthetic amorphous silica is gradually decreased from the lower layer to the upper layer of each ink receiving layer. . 2. The average particle size of the synthetic amorphous silica in the lowermost layer of the ink receiving layer is 10 to 20 μm, and the average particle size in the uppermost layer of the ink receiving layer is 1 to 10 μm. Inkjet recording sheet. 3. The inorganic fine particles are colloidal silica, alumina sol or alumina-doped silica, and the average particle size of the inorganic fine particles is 5 to 500 nm.
Alternatively, the inkjet recording sheet described in 2. 4. The absolute dry coating amount of the glossy layer mainly composed of inorganic fine particles is 5 to 25 g / m ² , and the absolute dry coating amount of the ink receiving layer is 5 to 25 g / m ^2. The ink jet recording sheet according to any one of items 1 to 3. 5. The ink jet recording sheet according to claim 1, which has a 75-degree specular gloss of 20 to 90% specified in JIS P8142. 6. The inorganic fine particles are colloidal silica treated with an organic cation, and the average particle diameter of the inorganic fine particles is 5
The ink jet recording sheet according to any one of claims 1 to 5, which has a thickness of ˜500 nm.