JP2000033769A - Ink jet recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve image coloring density and sharpness by laminating in turn an ink acceptable layer and surface treatment layer on at least one surface of a base material, and by the use of a colloidal silica gel of a predetermined primary particle diameter in the surface treatment layer. SOLUTION: A colloidal silica gel used for the surface treatment layer of an ink jet recording medium is defined by a primary particle diameter and coagulation particle diameter. Employing the colloidal silica gel allows superior dispersibility to be obtained in coating liquid to render the coating liquid stable and form surface treatment for accomplishing excellent image characteristics. Concretely, the primary particle diameter is 5-30 nm, preferably 9-25 nm, especially preferably 10-18 nm, and most preferably 11-14 nm. In addition, the coagulation particle diameter is 18-250 nm, preferably 30-110 nm and most suitably 35-75 nm in the colloidal silica gel attains particularly superior image characteristics. Also, since an ink absorption speed is fast, it is adapted to high speed printing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium, and more particularly to a recording medium having a high print density, a clear image, excellent ink absorbability, a high ink absorption speed, and sufficient for high-speed printing. The present invention relates to an inkjet recording medium that can be used.

[0002]

2. Description of the Related Art Inkjet printers have been increasingly used in recent years because they have features such as clearness of recording, quietness of sound, and ease of colorization. In order to prevent clogging of the jet nozzle due to drying of the ink, it is necessary to use ink that is difficult to dry. In general, as an ink having this property,
A water-soluble ink in which a binder, a dye, a solvent, an additive, and the like are dissolved or dispersed in water is used. However, from the viewpoints of print density and clarity, characters, images, and the like formed on a recording sheet using a water-soluble ink are superior in all respects to those of a printed material or a silver halide photograph using a pigment-based ink. There is no present. In recent years, as inkjet printers have become inexpensive and their sharpness and color have become familiar, demands for various characteristics such as print density and sharpness have been gradually increased and become stricter. Therefore,
At present, it is now an essential condition of an ink jet recording medium to ensure these characteristics completely.

[0003]

In view of this situation, the present inventors have been studying an improvement of an ink jet recording medium having improved print density and sharpness of a printed image. Already, the present inventors have found that by using a specific binder resin for the ink receiving layer of the ink jet recording medium, the color development of the image, the sharpness is improved,
We have applied for a patent on the ink receiving layer.

On the other hand, in the case of an ink jet recording medium having a surface treatment layer (gloss adjusting layer), it is expected that various properties such as image print density and image sharpness largely depend on the properties of the material. Therefore, as a result of intensive studies on the surface treatment layer material (colloidal silica gel) of the ink jet recording medium, it has been found that the use of a specific colloidal silica gel provides an ink jet recording medium having extremely excellent print density and clearness of a printed image. They have found and completed the present invention. Accordingly, an object of the present invention is to provide an ink jet recording medium having various characteristics such as excellent image color density and sharpness by using a specific colloidal silica gel for a surface treatment layer.

[0005]

The present inventors have conducted various studies on colloidal silica gel used for a surface treatment layer of an ink jet recording medium. The inventors have found that it is possible to provide an ink jet recording medium in which various characteristics such as color density and sharpness of an image are remarkably improved, and have completed the present invention. That is, the present invention provides an ink receiving layer and a surface treatment layer which are sequentially laminated on at least one surface of a substrate, and the surface treatment layer has a primary particle diameter of 5 nm or more.
The use of colloidal silica gel of 30 nm makes it possible to obtain a clear image with high print density and saturation, and it has excellent ink absorbency, as well as a high ink absorption speed, and is capable of high-speed printing. Which is an ink jet recording medium. Hereinafter, preferred embodiments according to the present invention will be described in detail.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An ink jet recording medium using a specific colloidal silica gel for a surface treatment layer of the present invention is described below.
It has a layer configuration in which at least one ink receiving layer is provided on at least one surface of the substrate by a laminating means such as a coating method, and the number of ink receiving layers may be two or three or more. A surface treatment layer using a specific colloidal silica gel is laminated on the surface of the ink receiving layer to produce an ink jet recording medium excellent in print density and image clarity. First, the materials constituting the base material and the ink receiving layer will be described.

(1) Substrate The substrate to be used in the present invention on which at least one surface is provided with an ink receiving layer is a chemical pulp such as LBKP or NBKP,
GP, PGW, RMP, TMP, CTMP, CMP, C
Regular paper making such as pigment and sizing agent, fixing agent, retention improver, paper strength enhancer, etc., mainly composed of wood pulp such as mechanical pulp such as GP, waste paper pulp such as DIP, and synthetic fiber pulp such as polyethylene fiber. One or more of the various additives used in the above are used and mixed as necessary, and a fourdrinier paper machine.
Base paper manufactured by various devices such as a round paper machine and a twin wire paper machine, base paper having a size press with starch, polyvinyl alcohol, etc., and an anchor coat layer provided on the base paper, and a coat layer formed thereon. And coated paper such as art paper, coat paper, cast coat paper, etc. An ink receiving layer may be provided on such base paper and coated paper as it is, or a calendar device such as a machine calendar, a TG calendar, or a soft calendar may be provided at a stage prior to coating the ink receiving layer for the purpose of controlling flattening. May be used.

As the base material, a polyolefin resin layer may be provided on the base paper, or a film material of a synthetic resin such as polyethylene, polypropylene, polyester, nylon, rayon, polyurethane, or a mixture thereof, A sheet formed by forming a resin into fibers is also included.

(2) Ink receiving layer (A) Pigment In the ink receiving layer in the present invention, one or more kinds of commonly used pigments which are insoluble or hardly soluble in water 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, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, colloidal alumina, pseudoboehmite, aluminum hydroxide, alumina, lithopone, zeolite, hydrohaloisite, magnesium carbonate, magnesium hydroxide, etc. Examples include white inorganic pigments, styrene-based plastic pigments, acrylic-based plastic pigments, polyethylene, microcapsules, organic pigments such as urea resins, and melamine resins.

Among the above, as the white pigment contained as a main component in the ink receiving layer, a porous inorganic pigment is preferable because the ink jet ink is excellent in drying property and absorptivity, etc., and porous synthetic amorphous silica, Examples include porous magnesium carbonate and porous alumina. Among them, in the present invention, sedimentation type and gel type porosity having a specific surface area of about 200 to 600 g / m ² satisfying both print quality and storage stability (prevention of discoloration / fading to indoor storage and direct sunlight). It is preferred to use amorphous silica.

(B) Binder Resin The binder contained in the ink receiving layer according to the present invention includes polyvinyl alcohol, vinyl acetate, oxidized starch, etherified starch, cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, casein,
Gelatin, soy protein, carboxyl-modified polyvinyl alcohol, silyl-modified polyvinyl alcohol, water-soluble resins such as water-soluble acrylic polymers; maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-
Conjugated diene copolymer latex such as butadiene copolymer; acrylic polymer latex such as acrylate and methacrylate polymer or copolymer; vinyl polymer latex such as ethylene vinyl acetate copolymer; Alternatively, a functional group-modified polymer latex of a functional group-containing monomer such as a carboxyl group of these various polymers; an aqueous adhesive such as a thermosetting synthetic resin such as a melamine resin or a urea resin; a polymethyl methacrylate, a polyurethane resin, Synthetic resin adhesives such as a saturated polyester resin, a vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, and an alkyd resin are used, and one or more kinds are used.

The mixing ratio of the pigment and the binder resin in the ink receiving layer is as follows: binder resin: pigment = 1: 1 to 1:
15 is preferable, and 1: 2 to 1:10 is particularly preferable.

(C) Other Additives Further, in the ink receiving layer, other additives such as a pigment dispersant, a thickener, a flow improver, an antifoaming agent, a foam inhibitor, a release agent, and a foaming agent. An agent, a penetrant, a coloring dye, a coloring pigment, a fluorescent whitening agent, an ultraviolet absorber, an antioxidant, a preservative, a water-proofing agent, a hardening agent, and the like can be appropriately compounded as necessary.

The ink receiving layer is formed by mixing a material comprising the pigment and the binder resin as described above for forming the layer, and other additives used as needed in a suitable solvent such as water, alcohol, or the like. The coating liquid prepared by dissolving or dispersing is applied to the substrate by appropriately using various devices such as various blade coaters, roll coaters, air knife coaters, bar coaters, rod blade coaters, size presses, etc. on-machine or off-machine. To be formed.
The coating amount of the ink receiving layer is, for example, preferably 5 to 30 g / m ² for a single layer type, particularly 5 to ²⁰ g / m ^2.
m ² is preferred. Further, a first ink receiving layer is laminated on a base material, and a second ink receiving layer is laminated on the first ink receiving layer to achieve better image clarity, water resistance and the like. If the type, the coating amount of the first ink receiving layer is preferably from 5 to 30 g / m ^2, in particular 5 to 20 g / m ² is preferred. The coating amount of the second ink receiving layer is 5 to 15
preferably g / m ^2, in particular 5 to 10 g / m ² is preferred.
If the coating amount is less than the above range, the ink absorbency and the fixability may not be sufficiently obtained. In particular, the second
When the coating amount of the ink receiving layer exceeds 15 g / m ² ,
It may be difficult for the ink to pass through the second ink receiving layer, causing bleeding and impairing the sharpness of the image. It is preferable to control the coating amount of the ink receiving layer depending on the number of the ink receiving layers to be laminated as described above.

After the ink receiving layer is applied, the ink receiving layer may be finished by using a calender such as a machine calender, a TG calender, a super calender, and a soft calender.

(3) Surface treatment layer The ink jet recording medium of the present invention uses a specific colloidal silica gel as a surface treatment layer material, and is laminated on the surface of the ink receiving layer having the above-described structure, and has excellent print density and excellent print density. The image has sharpness with saturation. Hereinafter, the material configuration, laminating method, laminating conditions, and various characteristics of the obtained surface treatment layer used in the ink jet recording medium of the present invention will be described.

<Material> Colloidal silica gel The colloidal silica gel used for the surface treatment layer of the inkjet recording medium of the present invention is characterized by being defined by a primary particle diameter and an aggregated particle diameter. By using such colloidal silica gel, good dispersibility can be obtained in the coating liquid, and a stable coating liquid can be obtained, and a surface treatment layer that achieves excellent image characteristics can be formed. Specifically, 1
Secondary particle diameter of 5 nm to 30 nm, preferably 9 nm to 25
nm, particularly preferably 10 nm to 18 nm, most preferably 11 nm to 14 nm. Furthermore, the aggregate particle diameter is 1
8 nm to 250 nm, preferably 30 nm to 110 n
m, most preferably from 35 nm to 75 nm, colloidal silica gel achieves particularly good imaging properties. In the present invention, the primary particle diameter is determined by BE by nitrogen adsorption.
The T particle size is referred to, and the aggregated particle size refers to the N4 particle size measured by a laser method.

Further, colloidal silica gel suitable for the present invention can be selected by referring to these two factors, but the aggregated particle diameter is preferably 2.0 to 10.0 times the primary particle diameter, and Is 3.0 to 9.0 times
It is preferable to use colloidal silica gel having a ratio of 3.0 times to 6.0 times, and more excellent image characteristics can be obtained in the present invention. Further, the primary particle diameter is 5 to 3
0 nm colloidal silica gel (A) and a primary particle size of 3
5-70 nm colloidal silica gel (B) is mixed in a solid content ratio of A: B = 9.5: 0.5-2: 8, most preferably in a combination of A: B = 7: 3-5: 5. Also in this case, an effect excellent in image characteristics can be achieved.

The colloidal silica gel used in the ink jet recording medium of the present invention is produced by a known method, such as an acid decomposition method, an electrodialysis method or an ion exchange method, using a dilute sodium silicate aqueous solution as a raw material. Things. For the primary particle diameter, various conditions such as adjustment of the molar ratio between silicon oxide and sodium oxide, control of the heating temperature during synthesis, control of the amount of alkali added to the active silicic acid, heat aging conditions, and the raw material concentration are set arbitrarily. 5 nm
It can be adjusted to 30 nm. In addition, the aggregated particle diameter is affected by the above-described primary particle synthesis conditions, but the conditions for promoting and stabilizing the association between the primary particles (catalysis of hydroxyl ions, dehydration by salt, acid-base bonding, By controlling cation-crosslinked bonds and the formation of hydrogen bonds by compounds containing an electron donating group).
It can be adjusted to a range of 8 nm to 250 nm.

When the colloidal silica gel used here is one whose particle surface is treated with a magnesium compound, a calcium compound, an aluminum compound, a zirconium compound, etc., the ink component is particularly excellent in the adsorbability of the dye component of the ink and the color is developed. It is preferable because of good properties. The colloidal silica gel selected in this manner or a mixture of a plurality thereof is prepared as a coating material for a surface treatment layer of an ink jet recording medium of the present invention together with a binder resin, and is laminated on the surface of the ink receiving layer and used.

2. Binder Resin As the binder resin contained in the surface treatment layer of the ink jet recording medium of the present invention, the same resin as the above-described ink receiving layer can be appropriately used. In the present invention, a water-soluble acrylic polymer is preferably used as the binder resin because of its excellent dispersibility of the specific colloidal silica gel. Among them, for example, a dialkylaminoalkyl methacrylate, a nitrogen-containing acrylic copolymer containing acrylamide or the like as a monomer component is preferable. As a result of earnest studies, it was confirmed that the combination was most suitable in terms of print image density, image clarity, and light fastness. The solid content weight ratio of the colloidal silica gel and the binder resin in the surface treatment layer was as follows: colloidal silica gel: binder resin = 11: 1.
To 8: 2, particularly 11: 1 to 9: 1.

3. Other additives In addition to the surface treatment layer, other additives include an antifoaming agent, a foam inhibitor, a release agent, a penetrant, a coloring dye, a coloring pigment, a fluorescent brightener, an ultraviolet absorber, and an antioxidant. An agent, a preservative, a water-proofing agent, a hardening agent and the like can be appropriately compounded as required. The surface glossiness can also be adjusted by using one or more commonly used water-insoluble or hardly soluble pigments such as synthetic amorphous silica gel, alumina, and talc together with the colloidal silica gel of the present invention. It is possible.

<Laminating method, laminating conditions, various properties such as glossiness> The surface treatment layer of the present invention can be arbitrarily controlled with respect to glossiness, but is not limited thereto. In the case where a glossy layer having excellent glossiness subjected to a surface treatment such that the glossiness according to the glossiness test method has a characteristic of 10 or more is used, ink absorption and image quality which are not sufficiently satisfied by the conventional glossy layer are obtained. There is an effect that good glossiness and image characteristics can be achieved without impairing characteristics such as sharpness at all.

In order to laminate the surface treatment layer on the ink receiving layer, it can be formed on the ink receiving layer by a general coating method. Further, for example, a coating liquid for a surface treatment layer is applied to a substrate having poor adhesion (for example, a polyolefin resin film, a tetrafluoroethylene resin film, a releasable siliconized resin film, etc.), and the coating liquid surface is left The layer can also be formed by layering on the ink receiving layer in a dry state and peeling the substrate after drying. The coating amount at which the surface treatment layer exhibits good characteristics without impairing the function of the ink receiving layer is preferably 3 to 25 g / m ² , and preferably 5 to 25 g / m ^2.
It is more preferable if it is １５15 g / m ² .

[0025]

Next, examples based on the present invention and comparative examples will be shown to further clarify the effects of the present invention. Examples 1 to 1
The formulations of the coating liquids for the ink receiving layer and the surface treatment layer of Comparative Examples 0 and 1 to 6 are as follows. [Coating liquid for ink receiving layer]-Binder resin Itaconic acid-modified polyvinyl alcohol (Kuraray Co., Ltd .: KL-318K) 20 parts-White pigment synthetic amorphous (Mizusawa Chemical Co., Ltd .: Mizukasil P78D) 20 parts-Water 250 parts

[Coating liquid for surface treatment layer]-Colloidal silica 55 parts of amorphous colloidal silica gel having particle diameter characteristics shown in Table 1-Binder resin Water-soluble acrylic resin (dimethylaminoethyl methacrylate / acrylamide / 2-hydroxyl Ethyl methacrylate / 2-hydroxyethyl acrylate, weight ratio 48/4/24/24) 5 parts ・ Water 20 parts

Table 1 shows the primary particle size and agglomerated particle size of each of the colloidal silica gels of Examples 1 to 10 and Comparative Examples 1 to 6 used for the surface treatment layer.

[Table 1]

In each of the examples and comparative examples, the base material was a high-quality paper having a basis weight of 90 g / m ² , and the above-described coating solution was applied to one surface of the base material and dried to form an ink receiving layer and a base material. What provided the surface treatment layer in order was used as the present invention or an inkjet recording medium for comparison. Here, the surface treatment layer is calendered after the formation to have a glossiness of 10 (6
(0 degree specular glossiness). In addition,
The coating amount was 10 g / m ² for both the ink receiving layer and the surface treatment layer. In Comparative Example 6, since the primary particle diameter of silica was large, the coating solution gelled and a surface treatment layer could not be provided, so the following image evaluation was not performed.

Next, the above Examples 1 to 10 and Comparative Examples 1 to 5
When an evaluation object such as a color patch was printed on a commercially available ink jet recording medium using a commercially available ink jet printer (manufactured by Seiko Epson Corporation: PM-700C), all of the printed images had good ink absorptivity (dryness). was gotten. Using these images, image print density and image clarity were evaluated by the following methods.

1. Evaluation of Image Print Density Using a spectrophotometer GRETAG SPM50 (manufactured by Gretag Macbeth), the reflection densities of black, cyan, magenta, and yellow were measured, and the print image density characteristics were evaluated.

2. Evaluation of Image Visibility Using a spectrophotometer GRETAG SPM50 (manufactured by Gretag Macbeth), the saturation C = (a ² + b ² ) ^1/2 of each color of cyan, magenta and yellow was measured and evaluated.

[0032]

[Table 2]

[Table 3] As is clear from the results in Tables 2 and 3, the ink jet recording medium of the present invention had high print density, high chroma, and excellent image characteristics with excellent clarity. On the other hand, the images of Comparative Examples 1 to 5 all had poor print density and sharpness.

[0033]

As described above, by laminating the surface treatment layer using the colloidal silica gel of the present invention on the ink receiving layer, the printing density is high, the image is clear,
An unprecedented ink jet recording sheet having excellent ink absorbency can be obtained. In addition, since the ink absorption speed is high, there is an effect that it is possible to cope with high-speed printing technology. In addition, since these surface treatment layers can control the degree of surface gloss, they can sufficiently respond to design requirements such as glossy paper, semi-glossy paper, and matte paper.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Yoshimoto 3-1 Yomoe-cho, Shizuoka-shi, Shizuoka Prefecture Inside the paper division of Hamakawa Paper Co., Ltd. (72) Inventor Nobuhiro Kubota 3 Yomune-cho, Shizuoka-shi, Shizuoka No. 1 Inside the Paper Division of Hamakawa Paper Mills Co., Ltd. (72) Kiyoshi Iwamoto Inventor Kiyoshi Tomoe 3-1, Yomibacho, Shizuoka City, Shizuoka Prefecture Inside of the Paper Division of Hamakawa Paper Mill Co., Ltd. 3-5-5 Seiko Epson Corporation (72) Inventor Hiroyuki Onishi 3-5-5 Yamato Suwa City, Nagano Prefecture Seiko Epson Corporation (72) Inventor Yukari Sano Yamato 3-chome, Suwa City, Nagano Prefecture No. 3-5 Seiko Epson Corporation F-term (reference) 2H086 BA13 BA15 BA21 BA32 BA45 4F100 AA20C AA20H AB09C AB09H AB10C AB10H AB19C A B19H AK21B AK25C AL07B AR00B AT00A BA03 BA07 BA10A BA10C BA13 CA23B CC00B CC00C DE01C DG10A EJ68H GB90 JA20C JD14B JN21 YY00C

Claims (6)

[Claims] 1. An ink receiving layer on at least one surface of a substrate,
An ink jet recording medium comprising: a surface treatment layer provided in a layered manner; and a colloidal silica gel having a primary particle diameter of 5 nm to 30 nm is used for the surface treatment layer. 2. The aggregate particle size of colloidal silica gel is 1
The inkjet recording medium according to claim 1, wherein the thickness is 8 nm to 250 nm. 3. The aggregate particle size of colloidal silica gel is 1
3. The ink jet recording medium according to claim 1, wherein a value obtained by dividing by a secondary particle diameter is in a range of 2.0 to 10.0. 4. Colloidal silica gel having a primary particle diameter of 5 to 30 nm (A) and colloidal silica gel having a primary particle diameter of 35 to 70 nm (B)
2. The ink jet recording medium according to claim 1, wherein a mixture is used in a solid content weight ratio of A: B = 9.5: 0.5 to 2: 8. 5. The ink jet recording medium according to claim 1, wherein colloidal silica gel treated with a metal compound is used. 6. The ink jet recording medium according to claim 5, wherein the metal compound is at least one compound selected from a magnesium compound, a calcium compound, an aluminum compound and a zirconium compound.