JPH0443069A - Ink jet recording medium and method - Google Patents

Abstract

PURPOSE:To form a high density image of high grade by adding basic magnesium carbonate and magnesium phophate to a recording medium. CONSTITUTION:Spherical basic magnesium carbonate 15 pts. and water 85 pts. are mixed for 15min at 10,000rpm under stirring by a commercial homogenizer and, in the same way, magnesium phosphate 10 pts. and water 90 pts. are mixed under stirring. The obtained mixtures are mixed with an aqueous binder solution separately prepared for 5min under stirring so as to obtain a desired pigment/binder ratio. Thereafter, various additives are added to the resulting mixture in specific quantities if necessary to be mixed therewith for 5min under stirring. The coating solution thus obtained is applied to base paper whose sizing degree converted based on a basis wt. 65g/m<2> in a ratio of 5g/m<2> on a solid basis by a wire bar coater and dried at 110 deg.C for 5min. The coated paper is treated using a supercalender to obtain a recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a recording medium and an inkjet recording method suitably used for inkjet recording.

(Prior Art and its Problems) Conventionally, as inkjet recording media, plain paper without any special treatment or coated paper provided with an ink-receiving layer have been used.

In the case of the above-mentioned plain paper, when recording is performed using water-based ink, bleeding or feathering occurs in the formed image in most cases, and there is a problem that an image with high density and high resolution cannot be formed.

In order to solve these problems, various inkjet recording media have been proposed in which paper is used as a support and an ink-receiving layer for absorbing water-based ink is provided on the surface of the support. For example, JP-A-56-148585 describes coated paper in which an ink-receiving layer is provided using a porous inorganic pigment on an ink-absorbing base paper. Also, JP-A-61-135
No. 785 describes an inkjet recording medium containing a hydrotalcite compound, and Japanese Patent Laid-Open No. 6
Publication No. 1-57380 describes an inkjet recording medium provided with an ink-receiving layer containing a porous inorganic pigment and poorly soluble magnesium. In the conventional example described above, ink feathering and text thickening do not occur during image formation. Although it has the advantage of forming an image with good resolution, it is difficult to obtain a high-density image. When silica or alumina with a high content is used, the color of the recording dye changes over time, and there is a problem in that the recorded image deteriorates even if the recording dye is left in a normal environment, such as by pasting it on an indoor wall.

Furthermore, when an ink-receiving layer is formed using a pigment such as calcium carbonate, kaolin, or the hydrotalcite compound described in JP-A-61-135785, which has a small specific surface area,
Although the above-described indoor discoloration is suppressed, the resulting image density is low (feathering and text thickening occur, and a clear image cannot be obtained).

Furthermore, when the above-mentioned pigments are used alone or in combination in the ink-receiving layer, if the average particle diameter of the pigment is larger than 7 μm, there is a problem that white mist tends to occur in printing.

This white haze is a phenomenon peculiar to paper with a thin ink-receiving layer, i.e., a small amount of coated paper.As a result of the coating layer being thin, it cannot cover the fibers exposed on the surface of the paper that is the support, and the dye is applied to the exposed fibers. It was believed that this problem was caused by poor adsorption and a decrease in the 4 degrees of exposed fibers.

Of course, this kind of problem can be solved by forming a thick ink-receiving layer to cover all the paper fibers, but recording media with such a thick ink-receiving layer will only feel less like paper. (This is not preferable from the point of view of cost, weight, etc.).

Further, by adding a cationic polymer having excellent dye adsorption properties to the ink-receiving layer, problems such as thick characters can be solved, but there is a problem that the storage stability of recorded images is deteriorated.

In other words, in the case of conventional coated paper, when the ink receiving layer is formed thinly, it is possible to obtain high image density without the feathering or thick characters generally required for inkjet recording media, and to avoid white haze as a coated paper. It was difficult to simultaneously solve the problem and the problem of indoor discoloration.

Therefore, an object of the present invention is to provide an inkjet recording medium and an inkjet recording method that simultaneously solve the problems of the prior art described above, such as feathering, thick characters, white haze, indoor discoloration, etc., and are capable of forming high-density images. That's true.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention provides an inkjet recording medium characterized by containing basic magnesium carbonate and a magnesium phosphate oxylate, and a layer containing a basic magnesium carbonate and a magnesium phosphate oxylate on a support. An inkjet recording medium and an inkjet recording method using the recording medium are provided.

(Function) In the present invention, problems such as feathering, thick characters, white haze, and indoor discoloration are solved because the recording medium contains basic magnesium carbonate and magnesium phosphate oxylate, and the recording medium has high concentration and An inkjet recording medium capable of forming high-quality images can be provided.

In other words, when the recording medium contains only basic magnesium carbonate, it simultaneously satisfies all functions such as excellent indoor discoloration prevention properties and image density, and does not cause problems such as white haze or thick characters. It is not possible to obtain an inkjet recording medium similar to the one obtained in this paper.

On the other hand, by using basic magnesium carbonate and a magnesium phosphate oxylate together, an inkjet recording medium that can satisfy all of the above-mentioned properties can be provided, although the mechanism is not clear.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The magnesium phosphate oxylate used in the present invention is
Compounds known per se, particularly preferred are magnesium phosphate. These magnesium phosphates include anhydrous salts, tetrahydrate salts, octahydrate salts, 22-hydrate salts, etc., and any of them can be used in the present invention, and their particle sizes are not particularly limited, but the average particle size is Preferably within 7 μm, 9
More preferably, the 0% particle size is within 12 μm. If the particle size exceeds the above range, the coating properties of the paper support will be poor and uncoated fibers will be generated, which is undesirable in terms of preventing white haze and text thickening.

The basic magnesium carbonate used in combination with the magnesium phosphate oxylate is not particularly limited, but
In particular, JP-A-60-54915 and JP-A-61
Spherical basic magnesium carbonate having the forms disclosed in Japanese Patent No. 63526 and Japanese Patent No. 63-89418 is preferable from the viewpoint of the effect of the present invention, but the manufacturing method is not limited thereto.

The spherical shape in the present invention refers to the shape of aggregated particles of secondary particles, and does not necessarily have to be perfectly spherical. A preferable spherical shape is 0.7≦, where the major axis is a and the minor axis is b.
It has a shape in the range of a/b≦1.0.

However, when producing such spherical basic magnesium carbonate, if the reaction conditions are changed to suppress the particle size, specific surface area, oil absorption, and other physical properties of the pigment, it is not always possible to produce a sufficiently spherical product. However, the present invention is not limited to this, and for example, there may be cases in which a part of the sphere is missing or a ball aggregated in the shape of a flower petal.

In the present invention, even if there is a missing part, if it is within 1/4 of the volume assuming a spherical shape, it is included in the spherical shape.

The average particle diameter of basic magnesium carbonate is 0.5
-20um, preferably 1-12gm is desirable. If the particle size is too small, the ink absorbency will decrease, and if the particle size is too large, powder will easily fall off, which is not preferable.

If the number of particles having too large a particle size is too large, the dispersibility of the particles decreases, large aggregates are formed during slurry preparation, and this adversely affects coating suitability or printing suitability, which is not preferable.

The support used in the present invention is preferably a base paper having ink-absorbing properties, but is not particularly limited thereto, and may be a polymer film such as polyester, for example. A preferred embodiment in which the support is a base paper having ink absorbing properties will be described below.

The ink-receiving layer of the inkjet recording medium of the present invention is composed of the above-described magnesium phosphate oxylate, basic magnesium carbonate, a binder, and other additives.

The ratio of basic magnesium carbonate and magnesium phosphate oxylate is preferably in the range of former/latter = 115 to 9/1 by weight; if the ratio of basic magnesium carbonate exceeds the above range, Although the indoor discoloration prevention properties of the formed images are good, problems such as image density, feathering, bleeding, and white haze are not sufficiently solved. If there,
Problems such as feathering, bleeding, and white haze do not occur, but
Image density and indoor discoloration prevention effects are insufficient, and within the above range of usage ratio, problems such as image density, indoor discoloration, feathering, bleeding, white haze, etc. are solved at once.

In the present invention, in addition to the above two types of pigments, other inorganic pigments and organic pigments that have been commonly used can also be used in combination within a range that does not impede the object of the present invention.

Examples of binders that can be used in the present invention include conventionally known water-soluble polymers such as polyvinyl alcohol, starch, oxidized starch, cationized starch, casein, carboxymethyl cellulose, gelatin, hydroxyethyl cellulose, acrylic resin, and SBR latex. , polyvinyl acetate emulsion, etc., or a mixture of two or more thereof may be used.

In the present invention, the preferred ratio of pigment and binder used is a weight ratio of pigment/binder (P/B) of 10/1 to 10/1.
The binder amount is within the range of 1/4, more preferably within the range of 6/1 to 1/1.If the amount of binder is larger than 1/4, the ink absorption property of the ink receiving layer will decrease; If the amount of pigment is too large, the ink-receiving layer will become more powdery, which is not preferable.

Furthermore, in the present invention, dye fixing agents (water-resistant agents), optical brighteners, surfactants, antifoaming agents, pH adjusters, fungicides, ultraviolet absorbers, and antioxidants are added to the ink-receiving layer as necessary. Additives such as agents, dispersants, and thinners may also be included. These additives may be arbitrarily selected from conventionally known compounds depending on the purpose.

In preparing the recording medium of the present invention, a water-based coating solution containing the pigments, binders, and other additives as described above is used.
Known methods such as roll coater method, blade coater method, air knife coater method, gate roll coater method
It is applied to the surface of the substrate by a method such as a method or a size press method. Thereafter, the recording medium of the present invention is obtained by drying using, for example, a hot air drying oven or a hot drum.

Furthermore, a supercalender treatment may be performed to smooth the surface of the ink-receiving layer or to increase the surface strength of the ink-receiving layer.

The coating amount of the ink receiving layer is within the range of 0.2 to 50 g/rrl', more preferably 0.2 to 20 g/rrl'. When the coating amount is small, a part of the base material may be exposed on the surface. Furthermore, if the coating amount is less than 0.2 g/rrf, the color development of the dye will not be as effective as when no ink-receiving layer is provided (on the other hand, if the coating amount exceeds 50 g/rrf This is undesirable as powdering of the coating layer occurs.When the coating amount is expressed in terms of thickness, the coating amount of the ink receiving layer is preferably in the range of 0.5 to 100 μm in thickness.

The recording medium of the present invention has been described above in terms of preferred embodiments. In addition to the ink-receiving layer formed on the surface of the support, the recording medium of the present invention also includes pigments of the above combination inside the paper support. It may be something that has been done.

When performing inkjet recording on the recording medium described above, any known ink itself can be used without any problems. In addition, water-soluble dyes such as direct dyes, acid dyes, basic dyes, reactive dyes, and food dyes can be used as recording agents, and they can be used without any particular restrictions as long as they are for normal inkjet recording. I can do it.

Such water-soluble dyes are generally used in a proportion of about 0.1 to 20% by weight in conventional inks, and this proportion may be the same in the present invention.

The solvent used in the water-based ink used in the present invention is water or a mixed solvent of water and a water-soluble organic solvent, and a particularly preferable one is a mixed solvent of water and a water-soluble organic solvent. It contains a polyhydric alcohol that has an effect of preventing ink from drying out. The method for performing recording by applying the above-mentioned ink to the above-mentioned recording medium is preferably an inkjet recording method, and this method effectively releases the ink from a nozzle to the recording medium, which is a projectile. Any method that can apply ink may be used.

In particular, the method described in Japanese Patent Application Laid-Open No. 54-59936 is an inkjet method in which ink subjected to the action of thermal energy undergoes a rapid volume change, and the acting force due to this change in state causes the ink to be ejected from a nozzle. can be used effectively.

(Example) Next, the present invention will be explained in more detail by giving examples and comparative examples. In the text, parts or percentages are based on weight unless otherwise specified.

Examples 1 to 5 Table 1 below shows the average particle diameter of the magnesium phosphate oxylate used in producing the recording medium according to the present invention. Further, as basic magnesium carbonate, spherical basic magnesium carbonate A and B having the average particle diameter and BET specific surface area shown in Table 1 below were synthesized and used (the synthesis method is described in JP-A-60-54915). (Performed by the same method as disclosed with varying reaction conditions).

(Left below) Fat 1''-j *1 Magnesium phosphate is made into fine particles using a sand mill in-house.

The recording medium was created by the following method.

First, 15 parts of spherical basic magnesium carbonate was mixed with 85 parts of water, and the mixture was heated to 10,00 rpm using a commercially available homogenizer.
Stir for 15 minutes.

Similarly, 10 parts of magnesium phosphate is mixed with 90 parts of water and stirred.

Thereafter, it is mixed with a binder aqueous solution (10% polyvinyl alcohol aqueous solution) prepared separately so as to obtain a desired pigment/binder ratio (in terms of solid content), and stirred for 5 minutes. After adding specific amounts of various additives as necessary,
Stir for 5 minutes.

The coating solution obtained as described above was coated with a wire bar coater with a basis weight of 65 g/rT? It was applied to a base paper having a sizing degree of 3 seconds based on the standard at a solid content of 5 g/m 2 , dried at 110° C. for 5 minutes, and treated with a supercalender to obtain a recording medium of the present invention.

The binder for both recording media was polyvinyl alcohol PVAI 17 (saponification degree 98.5, manufactured by Kuraray@).
mol%, concentration 4% viscosity 35 cps at 20°C) and P
VA-217 (saponification degree 89 mol%, concentration 4% viscosity 30 cps at 20°C) and PVA117/P in solid content ratio
The one containing VA217 at a ratio of 4/1 was used.

In addition, as a dye fixing agent, PAS-A-1 manufactured by 1st Nittobo Co., Ltd.
205 (polyamine sulfonate, 10') was added in a weight percentage of 10% based on the pigment. In the above, the pigment/binder ratio was 2/l.

The pigment compositions of the recording media 1 to 5 prepared above are summarized in Table 2 below.

1 mrr? using ink having the following composition on the recording medium of Examples 1 to 5 above? Inkjet recording was performed using an ink amount of 8 nl/mrrf per single color.

Ko2 no Nagikai dye 5 parts diethylene glycol 20 parts water
80 parts Tooth-11 Material Y: C, 1, Direct Yellow 86 M, C, 1, Acid Red 35 C: C, 1, Direct Blue 199 Bk: C, 1, Food Black 2 As evaluation items (1) Image Concentration, (2) Indoor storage stability, (
Four points were evaluated: 3) white blur and (4) thick letters.

The image density is the reflection density OD (B
k) was evaluated using a Macbeth reflection densitometer RD-918.

Regarding indoor shelf life, prints are left in an office environment where outside air circulates well but is not exposed to direct sunlight, and the color difference (△E") after 1 month and 3 months is determined by Murakami Color. Measured using a color difference meter CA-35 at the Institute.

A sensory evaluation was performed for white haze and thick letters, and the evaluation was performed in three stages: ◯ (good), △ (slightly poor), and × (poor). The evaluation results are listed in Table 3.

Comparative Example 1 P-Type (basic magnesium carbonate 4Mg (:03MgfOH) 21H20 manufactured by Ube Chemical Industry ■ as a pigment)
, average particle size I2, 8μm, BET specific surface area 35g/g)
The same recording media as in Examples 1 to 5 were prepared except that only
As shown in Table 4, although the indoor discoloration prevention property was excellent, the image density was low, and the white haze and thick characters were also unsatisfactory.

Comparative Example 2 Synthetic hydrotalcite (basic magnesium aluminum hydroxy carbonate hydrate Mg manufactured by Tomita Pharmaceutical Co., Ltd.) was used instead of magnesium phosphate oxylate.
4. Jl□(OH) + 5cOs・3.5H20,
Example 3~ except that the average particle size was 2.98 μm
When a recording medium similar to Example 5 was prepared and evaluated in the same manner as in Examples 1 to 5, as shown in Table 4, the indoor discoloration, white haze, and thick characters were somewhat good, but the image density was poor. I was not satisfied.

(Hereinafter referred to as the margin) 1 Δ reduction (Effect of the invention) As described above, according to the present invention, it is possible to provide a high-density recorded image in which problems such as indoor discoloration, white haze, and thick characters are solved at the same time. An inkjet recording medium and an inkjet recording method are provided.

Claims (8)

[Claims] (1) An inkjet recording medium characterized by containing basic magnesium carbonate and a magnesium phosphate oxylate. (2) An inkjet recording medium characterized in that a layer containing basic magnesium carbonate and a magnesium phosphate oxylate is provided on a support. (3) The inkjet recording medium according to claim 1 or 2, wherein the basic magnesium carbonate is spherical basic magnesium carbonate. (4) The inkjet recording medium according to claim 1 or 2, wherein the average particle size of the magnesium phosphate oxylate is 7 μm or less. (5) The inkjet recording medium according to claim 1 or 2, wherein the magnesium phosphate oxylate is magnesium phosphate. (6) The inkjet recording medium according to claim 1 or 2, wherein the weight ratio of basic magnesium carbonate to magnesium phosphate oxylate is within the range of former/latter = 1/5 to 9/1. (7) The coating amount of basic magnesium carbonate and magnesium phosphate oxylate is 0.2 to 50 g/m^ based on solid content.
3. The inkjet recording medium according to claim 2, wherein the inkjet recording medium is within the range of 2. (8) In an inkjet recording method carried out by applying droplets of aqueous ink to a recording medium, the recording medium has a layer containing basic magnesium carbonate and a magnesium phosphate oxylate formed on a support. An inkjet recording method characterized by: