JPH1081061A - Ink jet recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a recording medium excellent in the resolution, color reproducibility, sharpness, ink absorbing property and the like of an image, which can deal with a high speed and highly fine full color recording by a method wherein a surface coat layer, which mainly contains acrylic resin emulsion under the specified conditions, is formed on a porous ink absorbing layer provided on a support. SOLUTION: A porous ink absorbing layer is formed by applying paint consisting of pigment such as porous synthetic amorphous silica or the like and binder such as polyvinyl alcohol or the like by one layer or more. By applying a surface coat layer made of acrylic resin emulsion obtained through emulsion-polymerization by adding monomer mixture, polymerization initiator, emulsifying agent, water-soluble polymerization chain transfer agent and the like, to dispersing medium such as water or the like on the porous ink absorbing layer, this recording medium is formed. The glass transition temperature of the acrylic resin emulsion is set to be 15 deg.C or higher. The particle diameter of the emulsion is set to be 0.25μm or less. The spread of the surface coat layer is set to lie within the range of 0.5-1.0g/m<2> . As a result, the excellent gradient, color reproducibility, vividness, ink absorbency and easily handleable surface strength are given to the recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium used in an apparatus of an ink jet recording system using a liquid ink.
The present invention relates to an ink jet recording medium having excellent ink absorption and surface strength.

[0002]

2. Description of the Related Art In recent years, demand for color hard copy has been widened. In particular, the ink jet recording system, which is a type of non-impact recording system, is a high-speed, low-noise, direct recording that does not require a development process,
It has spread rapidly because color printing is possible with relatively simple devices.

In particular, as an application field of the multi-color ink jet system, an attempt is being made to apply it to the field of small-volume printing, which is quantitatively expensive for the multi-color printing of the plate-making system. However, it is required that a full-color, high-definition image comparable to that of an image can be output at a higher speed.

In the case of recording on a recording material by the ink jet system, generally, an original image to be recorded is equally subdivided, and each of the subdivided images is defined as a pixel.
By forming one ink dot or a plurality of ink dots at the time of recording, it is reproduced on the recording material. When trying to reproduce a higher-definition image, it is necessary to divide the image more finely and increase the number of pixels to increase the amount of information on the recording material, but the number of ink dots required to compose the image is This increases the time required to record all images. That is, in high-definition image recording, especially in full-color high-definition image recording, the recording speed is a major bottleneck.

[0005] To address this problem, the approach from the recording apparatus technology is to increase the nozzle density by reducing the size of the nozzles and the size of the ink particles, and at the same time, increase the frequency of the dot discharge head (the number of discharges per unit time) to increase the speed. And high definition.

[0006] From the ink technology side, in order to stably eject smaller ink droplets even at a high-speed frequency, an ink having a low surface tension that requires less energy to generate the surface of the droplet in the process of particleization. Will be used.

In order to reproduce a higher definition full-color image on a recording material, the recording density of dots on the recording material is high, the dot diameter is small, the dot shape is uniform, and the density is high. It is necessary to suppress color mixture of adjacent ink dots having different colors. The ink droplets are ejected on the surface of the recording material at a very high speed, but the kinetic energy of the droplets is absorbed by expanding the surface area by flattening the rubber material on the recording material and expanding the surface area. After that, the ink adheres to the recording material and further penetrates into the recording material to form dots. The ink corresponding to high-speed recording has a low surface tension, so the kinetic energy is absorbed by expanding the surface area more flatly, but the ink droplet is ejected immediately next to the ink droplet that has spread greatly, and the recording material Ink droplets come into contact with each other on the surface to mix with each other, which tends to reduce the reproducibility of the obtained image.

In order to record such full-color, high-definition images at high speed, the recording paper has been required to have higher recording characteristics in accordance with the recording device technology and the ink technology. Was. In addition, the diversification of the use environment of the recorded matter has required high paper properties.

That is, the characteristics required for such recording paper include: (1) that the ink absorbency is sufficiently high and no bleeding or stain occurs even in the superimposed recording portion of the ink; (3) The density of the ink dots is high and clear (4) The circularity of the ink dots is high. 5) The ink receiving layer does not peel off even if the recording medium surface is rubbed or the recording medium is bent.

Several proposals have hitherto been made to satisfy these requirements.

For example, Japanese Patent Application Laid-Open No.
In JP-A-2-158084 and JP-A-57-107879, an ink-receiving layer containing a pigment having excellent absorbability such as synthetic fine-grained silica as a main component is provided on the base paper surface to achieve high ink absorbency and recording. An ink jet recording medium having a density is disclosed. In this case, in order to cope with high-speed and high-definition recording, a method of increasing the void amount and the void ratio by using a bulkier pigment has been adopted.However, the strength of the ink receiving layer is reduced, and the generation of paper dust and image quality is reduced. It causes a problem in use such as peeling off.

Further, as a non-coating type, Japanese Patent Application Laid-Open No. Sho 53-4978 has been proposed in order to improve absorptivity and bleeding of ink dots.
No. 113 discloses an ink jet recording paper in which a water-soluble polymer is impregnated into a sheet in which a urea-formalin resin is added, and Japanese Patent Application Laid-Open No. 58-110288 discloses a paper in which synthetic fine-particle silica is incorporated. An ink jet recording paper is disclosed. Although the fillers are incorporated into the paper, the ink absorbency and surface strength are secured, but the pulp fibers are exposed on the paper surface, and the dot shape and size of the dots are not uniform. Cannot support full-color high-definition recording.

In order to improve the wettability of a recording material with ink, JP-A-60-171190 discloses an ink jet recording paper in which a surfactant is contained in a paint and an ink absorbing layer is provided. Although the ink droplets penetrate the recording material faster and the adjacent inks are less likely to come into contact with each other on the paper surface and mix together, the ink corresponding to high-speed recording has a low surface tension, so that the ink droplets are recorded. When penetrating inside the recording material, the dot diameter becomes larger than the target diameter.In addition, in the case of ink with low surface tension, the penetration progresses rapidly, so that dots of uneven shape may be formed or deep inside the recording material. The permeation lowers the dot recording density, making it impossible to obtain a desired full-color high-definition image.

[0014]

As described above, in the prior art, characteristics such as a resolution capable of recording a full-color image with high definition, a sufficient ink absorbency capable of recording at a high speed, and a surface strength at a level that does not cause a practical problem are obtained. At present, they were not fully satisfied.

That is, an object of the present invention is to provide an ink jet recording medium which is excellent in image resolution, color reproducibility, clarity, ink absorbency, and surface strength, which can support high-speed, high-definition full-color recording.

[0016]

In ink jet recording, ink droplets ejected from an ink jet head collide with and adhere to the surface of a recording medium, and then expand on the surface of the recording medium and penetrate into the inside of the recording medium. In the high-density printing required for full-color reproduction, extremely fine ink droplets of different colors come close to each other, causing the microstructure structure and surface chemical characteristics of the recording medium surface to rise. It greatly affects the expansion and penetration of ink droplets, which greatly affects the quality of the recorded image obtained.

The inventors of the present invention have conducted intensive studies in consideration of the principle of ink-jet recording and the above object, and have found that an ink-jet recording medium is provided with a porous ink-absorbing layer on a support and a surface coat layer formed thereon. In the recording material, the surface coat layer has an average particle size of 0.25 μm or less,
g By using an acrylic resin emulsion having a temperature of 15 ° C. or higher as a main component, the micro ink absorption characteristics of the porous ink absorbing layer are controlled by a surface coat layer mainly composed of an acrylic resin emulsion, thereby achieving stable recording. The characteristics and ink absorptivity were ensured, and the image resolution, color reproducibility, clarity, ink absorptivity, and surface strength were excellent, and the present invention was completed.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The support of the ink jet recording medium of the present invention is not particularly limited, and for example, natural pulp paper, synthetic pulp paper, cloth, nonwoven fabric, porous film, film and the like are used. The thickness and basis weight of the support are selected in consideration of the transportability in the recording apparatus.
0 to 250 μm and a basis weight of 30 to 200 g / m ² are used. The porous ink absorbing layer is formed by applying one or more paints composed of a pigment and a binder on the surface of the support. Pigment is porous synthetic amorphous silica, porous magnesium carbonate,
As a main component, a porous inorganic pigment such as porous alumina, light calcium carbonate, heavy calcium carbonate, synthetic amorphous silica which is a white pigment used in the papermaking field if necessary,
Colloidal silica, colloidal alumina, pseudo-boehmite, aluminum hydroxide, alumina, alumina white, aluminum silicate, magnesium silicate, magnesium carbonate, magnesium hydroxide, zeolite, clay, talc, mica, barium sulfate, calcium sulfate, titanium dioxide, satin white , Zinc oxide, zinc sulfide, zinc carbonate and other inorganic pigments, plastic pigments, urea resin,
An organic pigment such as a melamine resin is used in combination. For the purpose of the present invention, silica is particularly preferred as the porous synthetic amorphous material having a large pore volume.

As binders for adhering these pigments, polyvinyl alcohol, polyvinyl acetate, oxidized starch, etherified starch, esterified starch, carboxymethyl chitin, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, casein, soy protein, gelatin, Polyacrylates, alkylene maleate copolymer salts, water-soluble resins such as silyl-modified polyvinyl alcohol, styrene-butadiene copolymer latex,
Ethylene-vinyl acetate copolymer latex, acrylic
An emulsion such as an ethylene-vinyl acetate copolymer latex is used. Further, other additives include a dye fixing agent, a pigment dispersant, a flow improver, an antifoaming agent, a foam inhibitor, a release agent, a coloring dye, a coloring pigment, a fluorescent brightener, an ultraviolet absorber, and an antioxidant. An agent, a water-proofing agent and the like can be appropriately added. A coating composed of these pigments, binders and other additives is coated on a support at ² to 40 g / m ² , preferably 3 to 20 g / m ² to form a porous ink absorbing layer.

The compounding ratio (P / B) of the above-mentioned porous pigment, which is the main component of the porous ink absorbing layer, and the binder
Preferably has a weight ratio of 7/2 to 3/2. Within this range, both ink absorbency due to porosity and surface strength or coating suitability of the surface coat layer can be satisfied.

The acrylic resin emulsion used for the surface coat layer of the present invention may be prepared by a conventional emulsion polymerization method, that is, a method in which a monomer mixture, a polymerization initiator, an emulsifier, and a water-soluble polymer are added to a dispersion medium (eg, water). It can be obtained by adding a chain transfer agent or the like and conducting emulsion polymerization.

The monomer mixture is (A) methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, 2-hydroxyethyl acrylate , An acrylic monomer such as amyl acrylate, lauryl acrylate, or hexadecyl acrylate as a main component, and (B) 1,3-butadiene as required.
Conjugated diene monomers such as isoprene and 2-chloro-1,3-butadiene; methacrylic esters such as methyl methacrylate and glycidyl methacrylate; acrylamide compounds such as acrylamide, methacrylamide and N, N-dimethylacrylamide; and methacrylamide compounds ,
Vinyl cyanide compounds such as acrylonitrile, methacrylonitrile, and α-chloroacrylonitrile; unsaturated carboxylic acids such as acrylic acid, matacrylic acid, crotonic acid, maleic acid, and fumaric acid; styrene; α-methylstyrene; and P-methylstyrene In addition to aromatic vinyl compounds such as vinyl toluene and the like, (C) divinylbenzene having a cross-linking ability is appropriately mixed and used.

The polymerization initiator is not particularly limited. For example, inorganic persulfates such as potassium persulfate and sodium persulfate, for example, cumene hydroperoxide,
Organic peroxides such as benzoyl peroxide and isopropyl peroxide, for example, azo initiators such as azobisisobutylnitrile, and redox polymerization initiators obtained by combining the above persulfates with sodium bisulfite or ferrous sulfate Etc. can be used.

As the emulsifier, generally, anionic surfactants such as sodium dodecylbenzenesulfonate, sodium laurylbenzenesulfonate, sodium dialkyl succinate and the like, for example, polyoxyethylene alkyl ester, polyoxyethylene alkyl allyl ether Nonionic surfactants such as
Examples include amphoteric surfactants such as lauryl betaine and stearyl betaine salts. The amount of the emulsifier to be used is usually 0.05 to 100 parts of the total monomer mixed component.
About 2 parts. If the number exceeds this, the effect of improving the recording resolution is impaired.

As the emulsion polymerization, either a seed polymerization method or a no-seed polymerization method can be used.

In the present invention, the glass transition temperature and the average particle size of the acrylic resin emulsion are important. The glass transition temperature is 15 ° C. or more, and the particle size of the emulsion is 0.25.
If it is not more than μm, the object of the present invention cannot be achieved. Further, the glass transition temperature is preferably 15 to 50 ° C., and the emulsion particle size is preferably 0.05 to 0.20 μm. The glass transition temperature (Tg) can be adjusted by the mixing ratio of these monomers and the amount of cross-linked molecules introduced, and the average particle size can be adjusted by the type of emulsifier and the stirring conditions of the addition amount.

The surface coat layer is formed by applying a paint containing the acrylic resin emulsion as a main component on the porous ink absorbing layer. The emulsion may be used alone or in combination of two or more, but it is preferably at least 50 parts by weight, preferably at least 70 parts by weight based on 100 parts by weight of the components for forming the entire surface coat layer. In addition to the acrylic resin emulsion, known white pigments, for example, light calcium carbonate, heavy calcium carbonate, synthetic amorphous silica, colloidal silica, colloidal alumina, pseudoboehmite, aluminum hydroxide, alumina, alumina white, aluminum silicate,
White inorganic pigments such as magnesium silicate, magnesium carbonate, magnesium hydroxide, zeolite, clay, talc, mica, barium sulfate, calcium sulfate, satin white, zinc oxide and zinc sulfide, and white organic pigments such as plastic pigment, urea resin and melamine resin Pigments can be used. Among these pigments, similarly to the ink absorbing layer, porous synthetic amorphous silica, porous magnesium carbonate, and porous alumina are preferable, and porous synthetic amorphous silica having a large pore volume is particularly preferable. The coating amount of the surface coat layer is selected in the range of 0.5 to 1.0 g / m ² , and if it is more than this, the drying property of the ink is extremely reduced, and if it is less than this, the dot shape is impaired. More preferably 0.6
It is a ~0.8g / m ^2.

The coating method is not particularly limited, and a known technique can be used. For example, size press, roll coater,
Blade coaters, bar coaters, air knife coaters, curtain coaters, gravure coaters and the like are used.

If necessary, after impregnation and coating, a surface treatment with a metal roll, a cotton roll, a resin roll, or a combination thereof may be performed to control the surface properties of the recording medium.

[0030]

EXAMPLES The present invention will be specifically described below with reference to preferred examples, but the present invention is not limited to these examples. Further, "parts" and "%" shown in Examples are parts by weight and% by weight unless otherwise specified.

Among the objects of the present invention, the resolution of an image is related to the dot diameter and the circularity coefficient, the sharpness is related to the print density, the circularity coefficient, and the dot mixture color, and the color reproducibility is the dot mixture color and the solid portion. Uniformity and overall visual assessment can be obtained.

The recording suitability of the ink jet recording sheet was measured according to the following method.

Recording device: PIXCEL JE manufactured by Canon
T (Inkjet full color copier, resolution 400
dpi) was used.

1) Print Density: Color Test Chart NO. Black, cyan,
Magenta and yellow solid recording was performed, and the measurement was performed with a Macbeth recording densitometer (model: Macbeth RD915).

2) Circularity coefficient: Color Test Chart NO. 11 was used as an original figure, the area and perimeter of a single dot of cyan in the recorded image were actually measured using an image analyzer (PIAS-III manufactured by Pierce Co., Ltd.), and the circularity coefficient was calculated according to the following equation.

Circularity coefficient = {(4π) × (measured area)}
÷ (Measured perimeter) ^{2 The} closer to 1 is circular, the farther it is from 1 (<1), the less circular.

3) Dot diameter: color test chart No. 11 was used as an original figure, the area of a single dot of cyan in the recorded image was actually measured using an image analyzer, and the diameter of a perfect circle equivalent in area value was calculated according to the following equation to obtain the dot diameter.

Dot diameter = {(4 / π) × (actually measured area)} ^1/2 4) dot mixture: color test chart N of the Institute of Image Electronics Engineers of Japan
O. 11 was used as an original figure, and the degree of color mixing at the boundary where dots of different colors in the recorded image contact each other was observed with a stereoscopic microscope, and the following evaluation points were given.

：: Boundary portion is cut off △: Boundary shape is jagged ×: Boundary portion is mixed and blurred 5) Solid portion uniformity: Color Test Chart No. 22 as the original figure, black, cyan, magenta,
Solid of yellow, green, red, blue each,
The halftone was recorded and evaluated visually, and the following evaluation points were given.

◎: Uniform や: Slight density unevenness is observed in the halftone recording portion Δ: Density unevenness is observed in the halftone recording portion X: Graininess, white spots, and density unevenness are observed in the solid recording portion 6) Full-color image reproducibility: Color Test Chart NO. 11 was used as an original figure, and a full-color image portion was visually evaluated, and the following evaluation points were given. ◎: The image is reproduced in detail. ○: The reproducibility is poor in the area adjacent to the solid part where the amount of ink applied is large, or in the halftone part where the amount of ink applied is large.
Lack of depth perception of image part with large ink ejection amount Δ: Poor reproducibility of solid part and halftone part, lack of depth perception of image part, and emphasized boundary in part with relatively large amount of ink X: Poor gradation reproducibility in the halftone portion, and false contours are observed in the highlight portion. 7) Ink absorption: Color test chart NO. 22 was used as an original figure, recording was performed with the ink ejection amount of the recording apparatus set to the maximum amount (apparatus density adjustment scale MAX), and the recorded image generated at the time of poor ink absorption and the image stain at the time of contact of the paper discharge roll were observed. .

◎: Good ink absorbency and a clear image are obtained. イ ン ク: Good ink absorption, but shine is observed in a portion with a large amount of ink immediately after discharge. Δ: A portion with a large amount of ink. Unabsorbed ink is stretched on the image by the paper discharge roll, and the image of the portion with a large amount of ink appears to be slightly swollen. ×: The unabsorbed ink transferred to the roll is retransferred to the image, and the image is significantly damaged. 8) Surface strength: The recording portion was bent and squeezed twice with a plastic ruler to evaluate the degree of falling off of the coating layer.

：: No falling off Δ: Slightly falling off, but recording portion remains ×: Coating layer completely dropped off, and recording portion missing [Example 1] LBKP (freeness: 320 mlcsf) 80
Parts, wood pulp consisting of NBKP (freeness 390 mlcsf), light calcium carbonate 20 parts, and molecular weight 400
After preparing a stock containing 0.02 parts of 10,000 commercially available polyacrylamide, the stock was made with a Fourdrinier paper machine to obtain a support. The obtained support had a basis weight of 60 g / m ² .

A paint was prepared by mixing 100 parts of precipitated silica (Fine Seal X-37 manufactured by Tokuyama Corporation) as a porous pigment, 500 parts of a 10% solution of polyvinyl alcohol (PVA117 manufactured by Kuraray Co., Ltd.) as a binder, and 100 parts of water. It was prepared, coated and dried on the above support, and provided with a porous ink absorbing layer having a coating amount of 5 g / m ² .

Further, an acrylic emulsion A (Tg: 22 ° C., average particle diameter: 0.08 μm) was further formed on the porous ink absorbing layer.
Is applied with a Mayer bar # 4, and then the hot air drier 11
After drying at 0 ° C., a surface coat layer having a coating amount of 0.8 g / m ² was provided to obtain an ink jet recording medium.

Example 2 An acrylic emulsion B (Tg 40 °) was used instead of the acrylic emulsion A in Example 1.
C, average particle diameter 0.08 μm), and the applied amount is 0.9 g.
An ink jet recording medium was obtained in the same manner as in Example 1 except that a surface coat layer of / m ² was provided.

Example 3 An acrylic emulsion C (Tg35) was used in place of the acrylic emulsion A in Example 1.
° C, average particle size 0.15μm), application amount 1.0g
An ink jet recording medium was obtained in the same manner as in Example 1 except that a surface coat layer of / m ² was provided.

Example 4 On the support described in Example 1,
Precipitated silica (manufactured by Tokuyama Corporation) as a porous pigment
Fine seal X-37) 100 parts and polyvinyl alcohol as binder (PVA11 manufactured by Kuraray Co., Ltd.)
7) 500 parts of a 10% aqueous solution of polyethyleneimine (B
ASF Ltd. POLYMIN-P) 50% aqueous solution of 10 parts of mixed paint with 100 parts of water was prepared, coated and dried, provided the porous ink absorbing layer of the coating amount 6 g / m ^2.

Further, on the porous ink absorbing layer, 100 parts of a 30% dispersion of acrylic emulsion A, 10 parts of γ-alumina (Taimicron TM-300 manufactured by Daimei Chemical), and 1 part of water
000 parts was prepared and applied with a Meyer bar # 4, and then dried with a hot air drier at 110 ° C. to apply 1.0 g.
/ M ² , to provide an ink jet recording medium.

Comparative Example 1 An acrylic emulsion D (Tg-20) was used in place of the acrylic emulsion A of Example 1.
° C, average particle size 0.08 µm), coating amount 0.7 g
An ink jet recording medium was obtained in the same manner as in Example 1 except that a surface coat layer of / m ² was provided.

[Comparative Example 2] An acrylic emulsion E (Tg 0 ° C,
(Average particle diameter: 0.08 μm), coated amount: 0.8 g / m
An ink jet recording medium was obtained in the same manner as in Example 1, except that the surface coat layer of No. ² was provided.

[Comparative Example 3] An acrylic emulsion F (Tg 40
° C, average particle size 0.5 µm), and the coating amount 0.8 g /
An ink jet recording medium was obtained in the same manner as in Example 1 except that a surface coat layer of m ² was provided.

Comparative Example 4 The procedure of Example 1 was repeated except that the dispersion of the acrylic emulsion A of Example 1 was applied using a Meyer bar # 4 to provide a surface coat layer having a coating amount of 0.3 g / m ^2. Similarly, an ink jet recording medium was obtained.

Comparative Example 5 The acrylic emulsion A of Example 1 was applied using a Mayer bar # 8, and the applied amount was 1.3 g.
An ink jet recording medium was obtained in the same manner as in Example 1 except that a surface coat layer of / m ² was provided.

Comparative Example 6 Styrene butadiene emulsion F was used in place of acrylic emulsion A in Example 1.
(Tg 15 ° C., average particle size 0.16 μm), and an ink jet recording medium was obtained in the same manner as in Example 1 except that a surface coat layer having a coating amount of 0.7 g / m ² was provided.

Table 1 shows the structures and evaluation results of Examples 1 to 4.
Table 2 shows the configurations and evaluation results of Comparative Examples 1 to 4, and Table 3 shows the configurations and evaluation results of Comparative Examples 5 to 6, respectively. From these tables, it can be seen that the ink jet recording medium of the present invention has a print density balance of each color, a dot circularity count, a dot diameter, a degree of color mixing when dots are overlapped, uniformity of a solid printing portion, and full-color image reproduction by visual observation. It can be seen that images having good color reproducibility and good reproducibility were reproduced. Also,
Since the ink has excellent ink drying properties (absorbency) and strong surface strength of the recording medium, it can be seen that an ink jet recording medium which is easy to handle and suitable for practical use was obtained.

[0056]

[Table 1]

[Table 2]

[Table 3]

[0057]

According to the constitution of the present invention, it is possible to obtain an ink jet recording medium which is excellent in resolution, color reproducibility, clarity and ink absorption of an ink jet recorded image and has excellent surface strength which is easy to handle. .

Continuation of front page (72) Inventor Atsushi Ono 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Japan Paper Manufacturing Co., Ltd.

Claims (2)

[Claims] 1. A porous ink absorbing layer is provided on a support,
Furthermore, an average particle size of 0.25 μm or less, Tg of 15 ° C.
An aqueous ink jet recording medium, wherein the surface coat layer containing the above-mentioned acrylic resin emulsion as a main component is formed in a coating amount of 0.5 to 1.0 g / m ² . 2. The porous ink-absorbing layer contains porous silica (P) and polyvinyl alcohol (B) as main components, and the ratio (P / B) is 7/2 to 3/2 in terms of solids weight ratio. The aqueous inkjet recording medium according to claim 1, wherein