JPH04197776A - Recording medium and ink jet recording - Google Patents

Abstract

PURPOSE:To allow basic magnesium carbonate containing acid other than carbonic acid to ensure stable maintenance of a high specific surface area by forming an ink-receiving layer consisting of basic magnesium carbonate containing acid other than carbonic acid. CONSTITUTION:Basic magnesium carbonate used is cubic magnesium carbonate. If cubic particles account for more than 85% of the total particulate, such a magnesium carbonate is called 'cubic basic magnesium carbonate'. To allow the acid other than carbonic acid to be contained in basic magnesium carbonate, basic magnesium carbonate is mixed into an aqueous acid solution, then the acid is allowed to be absorbed into the surface of basic magnesium carbonate and the acid is dried. The recommended acid used is, for example, an organic acid such as phosphoric acid. If acid treatment is performed, the surface of basic magnesium carbonate is slightly dissolved by acid, resulting in the formation of numerous micropores on the surface of basic magnesium carbonate. Subsequently, the specific surface area is increased and this high specific surface state is stably maintained.

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) Conventionally, as an inkjet recording medium having an ink-receiving layer, a porous inorganic pigment is used on an ink-absorbing base paper, as described in JP-A-56-1.48585. Coated paper with an ink-receiving layer is used. As a porous inorganic pigment forming the coating layer, for example, silica disclosed in Japanese Patent Application Laid-open No. 185690/1984 can be cited as a pigment with excellent coloring properties. Many other examples include calcium carbonate and alumina.

(Problems to be Solved by the Invention) In the above conventional example, in order to obtain clear images with high image density, for example, silica with a high specific surface area as disclosed in Japanese Patent Application Laid-open No. 56-185690 is used. , the color of the recording dye changes over time, and the recorded image deteriorates even if it is left in a normal environment, such as by pasting it on an indoor wall. On the other hand, if a pigment with a small specific surface area such as calcium carbonate, kaolin, or talc is used, the above-mentioned indoor discoloration is suppressed, but the resulting image density is low (a problem arises in that the image is not clear).

That is, suppressing indoor discoloration and obtaining high image density are contradictory problems, which cannot be solved by conventional techniques.

Therefore, it is an object of the present invention to improve the storage stability of recorded images, especially to reduce deterioration due to indoor discoloration (and to provide a recording medium with high image density.
It is an object of the present invention to provide an inkjet recording method for a recording medium particularly suitable for inkjet use.

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

That is, the present invention provides a recording medium characterized in that a layer containing basic magnesium carbonate containing an acid other than carbonic acid is provided on the support surface, and ink is applied to the recording medium from an orifice of an inkjet recording head in accordance with a recording signal. This is an inkjet recording method characterized by performing recording by ejecting.

(Function) According to the findings of the present inventors, indoor discoloration of recorded images is a problem unique to coated paper that does not occur in non-coated paper such as general PPC paper. Furthermore, indoor discoloration is essentially different from fading of dyes due to irradiation with ultraviolet light or visible light, and occurs even in the absence of the above light.

From other findings of the present inventors, it is believed that the indoor angle change is due to the oxidative decomposition of the dye in the presence of interactions between the dye, the pigment, and the oxidizing gas. Therefore, if it is assumed that the larger the specific surface area of the pigment used, the more the oxidative decomposition reaction is promoted, this explains why coated paper with a larger specific surface area of the pigment has a greater degree of indoor discoloration.

On the other hand, from the point of view of image density, if there are many active surfaces near the surface of the coating layer where dye is adsorbed, the image density becomes thicker.

Therefore, in the conventional example, inkjet coated paper or coated paper, which satisfies the image density and does not cause indoor discoloration, is used.
An inkjet recording medium having layers could not be obtained.

The present inventors have previously discovered that by using basic magnesium carbonate to form an ink-receiving layer, sufficient image density can be provided with a pigment having a small specific surface area.

However, the specific surface area of conventionally known basic magnesium carbonate is in the range of 5 to 5 degrees, and when an ink-receiving layer is formed using this basic magnesium carbonate, it is insufficient to provide a clear color image. I can't say that. Furthermore, by appropriately setting the production conditions, basic magnesium carbonate with a high specific surface area may be obtained immediately after production, but this can be said to be in a metastable state, and it will not change over time. It returns to a stable crystalline state, and the specific surface area ends up being equivalent to that of conventionally known products.

In the present invention, by forming the ink receiving layer using basic magnesium carbonate containing an acid other than carbonic acid, the basic magnesium carbonate containing an acid other than carbonic acid stably maintains a high specific surface area. It has been found that a recording medium can be provided which sufficiently suppresses the indoor discoloration of the image and provides an image with high image density and no change over time.

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

The basic magnesium carbonate used in the present invention may be any conventionally known basic magnesium carbonate and is not particularly limited, but a particularly preferred basic magnesium carbonate is spherical basic magnesium carbonate. This spherical basic magnesium carbonate refers to basic magnesium carbonate having the form already disclosed in JP-A-60-54915, JP-A-61-63526, and JP-A-63-89418. The manufacturing method is not limited to these.

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 07≦a, where the major axis is a and the minor axis is b.
/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 RN material, it is not always possible to produce a truly 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, if the missing portion is within 1/4 of the volume assuming a spherical shape, it is also included in the spherical shape.

In addition, if the particles forming the agglomerated structure are relatively large and if the particles protruding to the outermost part of the spherical body are connected, the unevenness becomes severe, the outermost line will form a circle or be within the tolerance range of b/a above. When the ellipse of is applied, a is set so that it is the largest.

In addition, in the present invention, if the spherical particles as described above account for 85% or more of the total particles, it is called spherical basic magnesium carbonate. In addition, if aggregated particles appear to have adhered to each other, and if at least half the contour of the particle can be distinguished, 1
It is counted as one agglomerated particle.

As a method for incorporating an acid other than carbonic acid into basic magnesium carbonate as described above, there is a general method such as mixing basic magnesium carbonate into an aqueous acid solution, allowing the surface of basic magnesium carbonate to absorb the acid, and then drying. Any method is fine. Examples of the acids used include inorganic acids such as phosphoric acid, boric acid, bromic acid, and iodic acid, and organic acids such as oxalic acid, formic acid, tartaric acid, butyric acid, propionic acid, and acetic acid.

A preferred method for treating basic magnesium carbonate with the above acid is to prepare an aqueous solution of acid with a concentration of about 0.001-IN, and to
The desired basic magnesium carbonate containing an acid other than carbonic acid can be obtained by mixing with 00 to 500 parts by weight of an aqueous solution of the above acid to form a slurry, and drying the slurry as it is after mixing or after filtration.

The action of acid treatment in the above is that the acid slightly dissolves the surface of basic magnesium carbonate, generates countless micropores on the surface of basic magnesium carbonate, increases the specific surface area, and stabilizes this high specific surface area state. It is thought that it will last for a long time.

The content of acids other than carbonic acid in the basic magnesium carbonate obtained after the above treatment is 0.01 to 5 in the total weight.
A range that accounts for % by weight is preferred.

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-mentioned basic magnesium carbonate containing an acid other than carbonic acid, a binder, and other additives.

The average particle diameter of basic magnesium carbonate containing an acid other than carbonic acid is 0.5 to 20 μm, preferably 1 to 1 μm.
A thickness of 2 μm is desirable. If the particle size is too small, ink absorption will decrease, and if the particle size is too large, powder will easily fall off (
Undesirable.

Here, the particle diameter is the value of the long axis a mentioned above, and the average particle diameter is given as a simple average of a of 100 or more particles obtained by an electron microscope. Further, as for the particle size distribution of the basic magnesium carbonate containing an acid other than carbonic acid, it is preferable that the number of particles of 25 μm or less accounts for 95% or more of the total number of particles. More preferably 1
It is desirable that the number of particles with a diameter of 511 m or less accounts for 95% or more of the total, and most preferably, the number of particles with a diameter of 10 μm or less accounts for 95% or more of the total.

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.

Further, the specific surface area is a value obtained by the BET method, and it is particularly preferable to use a value of 10rd/g or more and 170ryf/g or less. If the specific surface area is too small, the image density will not increase. Furthermore, if the 5 specific surface area is too large, the indoor discoloration resistance will decrease.

In the present invention, within the scope that does not impede achievement of the purpose of the present invention,
In addition to basic magnesium carbonate containing an acid other than self-carbonic acid, other inorganic pigments or organic pigments that have been commonly used can also be used in combination.

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.
It is within the range of 1/4, more preferably within the range of 6/1 to 1/1; if the amount of binder is greater than 1/4, the ink absorbency of the ink receiving layer will decrease; on the other hand, 10/] If the amount of pigment is too large, the ink-receiving layer will become more powdery, so in the present invention, the ink-receiving layer preferably contains a dye fixing agent (waterproofing agent), a fluorescent whitening agent, a surfactant, and an eraser as necessary. Additives such as foaming agents, pH adjusters, fungicides, ultraviolet absorbers, antioxidants, dispersants, and thinners may be included. These additives may be arbitrarily selected from conventionally known compounds depending on the purpose.

Describing a dye fixing agent as an example of an additive, the water resistance of an image formed can be improved by using the following dye fixing agent in combination.

The above examples are merely illustrative, and the present invention is not limited thereto. Further, since the water resistance effect of the dye fixing agent differs depending on the dye used for inkjet recording, it is desirable to give sufficient consideration to the combination with the dye used for recording.

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 amount of pigment applied in the ink receiving layer is 0 as the total amount of pigment.
．． 2-50g/rrr, more preferably 02-20g/rrr
It is within the range of rrr. When the coating amount is small, a part of the base material may be exposed on the surface. Also, the coating amount is 0.2
g/rrf (J, there is no effect in terms of color development of the dye compared to the case where no ink-receiving layer is provided,
On the other hand, 50g/rr? If it is provided beyond this range, powder of the coating layer will occur, which is not preferable. When the coating amount is expressed in terms of thickness, the coating amount of the pigment is preferably in the range of 05 to 100 μm in thickness.

When performing inkjet recording on the recording medium described above, any known ink itself can be used without any problem. In addition, as a recording agent, water-soluble dyes such as direct dyes, acid dyes, basic dyes, 1 reactive dye, and 2 food dyes can be used, and there are no particular restrictions as long as they are used for recording purposes. It can be used.

Such water soluble dyes are generally found in conventional inks at about 0. ] to 20% by weight, and this ratio 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 polyhydric alcohol, which has the effect of preventing ink from drying.

The method for performing recording by applying the above-mentioned ink to the above-mentioned recording medium is preferably an inkjet recording method,
The method may be any method as long as it can effectively separate the ink from the nozzle and apply the ink to the recording medium, which is the projectile.

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.

An example of an inkjet recording apparatus suitable for recording using the recording medium of the present invention will be described below. Examples of the head configuration, which is the main part of the device, are shown in Figures 1(a) and 1(b).
) and shown in Figure 2.

The head 13 is made by bonding a glass, ceramic, or plastic plate, etc., having a groove 14 through which ink passes, and a heat-generating head 15 (a head is shown in the figure, but is not limited to this) used for thermal recording. It can be obtained by

The heat generating head 15 has a protective film 1 formed of silicon oxide or the like.
6. It consists of aluminum electrodes 17-1, 17-2, a heating resistor layer 18 made of nichrome or the like, a heat storage layer 19, and a substrate 20 with good heat dissipation properties such as alumina.

The ink 21 has reached a discharge orifice (micropore) 22, and a meniscus 23 is formed by the pressure P.

Now, when an electric signal is applied to the electrodes 17-1 and 17-2, the area indicated by n of the heating head 15 suddenly generates heat, bubbles are generated in the ink 21 in contact with this area, and the pressure causes The meniscus 23 protrudes, the ink 21 is ejected, and the recording small/I! from the orifice 22! i24, recording medium 2
Fly towards 5. FIG. 2 shows an external view of a multi-head in which a large number of heads shown in FIG. 1(a) are arranged. The multi-head is multi-Lf! Glass plate 27 with 426
and a heat generating head 2 similar to that explained in FIG. 1(a).
8 is made in close contact with each other.

Note that FIG. 1(a) is a cross-sectional view of the head 13 along the ink flow path, and FIG. 1(b) is a cross-sectional view taken along the line AB in FIG. 1(a).

FIG. 3 shows an example of an ink jet recording apparatus incorporating such a head.

In FIG. 3, 61 is a blade as a wiping member, one end of which is held by a blade holding member and becomes a fixed end, forming a cantilever shape. The blade 61 is disposed adjacent to the recording area of the recording head, and in this example, is held in a protruding form in the movement path of the recording head. A cap 62 is disposed at a home position adjacent to the blade 61, and is configured to move in a direction perpendicular to the moving direction of the recording head and come into contact with the ejection port surface to perform capping. Furthermore, 63 is an ink absorber provided adjacent to the blade 61;
Like the blade 61, it is held in a protruding form in the movement path of the recording head. The blade 61 and cap 62
The absorber 63 constitutes an ejection recovery section 64, and the blade 61 and the absorber 63 remove moisture, dust, etc. from the ink ejection orifice surface.

Reference numeral 65 has an ejection energy generating means, and a print head that performs printing by ejecting ink onto a print medium facing the ejection port surface on which ejection ports are arranged; and 66, a print head that mounts the print head 65 and controls the movement of the print head 65; It is a carriage for carrying out. The carriage 66 is slidably engaged with a guide shaft 67, and a portion of the carriage 66 is connected to a belt 6 driven by a motor 68.
9 (not shown). As a result, carriage 6
6 can be moved along the guide shaft 67, and the recording head 65 can move the recording area and its adjacent area.

Reference numeral 51 is a paper feed section for inserting a recording medium, and 52 is a paper feed roller driven by a motor (not shown). With these configurations, the recording medium is bound to a position facing the ejection orifice surface of the recording head, and as recording progresses, the recording medium is discharged to a paper discharge section provided with a paper discharge roller 53.

In the above configuration, when the recording head 65 returns to the home position after recording is completed, the cap 62 of the head recovery section 64
is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. As a result, the ejection port surface of the recording head 65 is wiped. Note that when the cap 62 contacts the ejection surface of the recording head 65 to perform capping, the cap 62 moves so as to protrude into the movement path of the recording head.

When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are in the same position as the wiping position described above. As a result,
During this movement as well, the ejection orifice surface of the recording head 65 is wiped.

The above-mentioned movement of the print head to the home position is not limited to when recording is completed or when ejection is restored, but also to the home position adjacent to the print area at predetermined intervals while the print head moves across the print area for printing. The wiping is performed along with this movement.

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

In preparing the recording medium according to the present invention, spherical basic magnesium carbonate (A to F) containing an acid other than carbonic acid and having the following average particle diameter, high specific gravity, and specific surface area were synthesized (Table 1, The synthesis method was the same as that disclosed in JP-A-60-54915, changing the reaction conditions. Table 1 also shows the acids used for surface treatment.

).

(Margin below) Table 1 After treatment; Immediately after treatment After being left for one month at 60°C and RH90%*: Immediately after synthesis Examples 1-4 The recording medium was created by the following method.

First, 15 parts of spherical basic magnesium carbonate listed in Table 1 was mixed with 85 parts of water, and the mixture was mixed with a commercially available homogenizer for 10 minutes.
Stir for 15 minutes at OOOrpm. After that, separately prepared binder/8 liquid (polyvinyl alcohol 10%
water/8 liquids) and desired pigment/binder ratio (solid content equivalent)
Mix and stir for 5 minutes. After that, specific amounts of various additives are added as needed, and then stirring is performed for 5 minutes.

The coating solution obtained as described above was applied using a wire bar coater, dried at 110°C for 5 minutes, and processed using a supercalender to obtain a recording medium.

The binders used in both recording media were polyvinyl alcohol pvAz7 (degree of M 98.5 mol%, degree of polymerization 1,700) manufactured by Kuraray (...) and PVA-217 (degree of saponification 89).
mol%, degree of polymerization 1.700) and solid content ratio of PVA l
17/PVA217 at a ratio of 8/2 was used.

The type of basic magnesium carbonate used in the recording medium obtained as above, the type of support, the pigment/binder ratio, the coating amount, the type of additive, and the percentage added to the pigment (%)
The results are summarized in Table 2 below.

Support ■: tsubo 170 g/rr? , high-quality paper with a size degree of 30 seconds*l: Polyallylamine hydrochloride (PA
A-HCl-31, average molecular weight 10,000) Examples 1 to 4
Inkjet recording was carried out on a recording medium using an ink having the following composition at an ink amount of 8 nl/mrrf per ml per monochromatic color (hereinafter, Examples 5 to 9 were similarly evaluated).

Tech Z2 ■ Dye 5 parts diethylene glycol 20 parts water
80 parts Vermilion Y: C, 1, Direct Yellow 86 M: C, 1, Acid Red 35 C: C, 1, Direct Blue 199 8: C, 1, Food Black 2 As evaluation items (1) Two points were evaluated: image density and (2) indoor storage stability.

Image density is 1 degree 0D (Bkl
was evaluated using a Macbeth reflection densitometer RD-918, and the indoor storage stability was determined by creating an environment in an office where outside air circulates well but not direct sunlight, and leaving the printed matter there for one month. The color difference (ΔE'') after 3 months was measured using a color difference meter CA-35 of the Murakami Color Research Institute. After storage for about 1 year at R) 455%), an image was formed in the same manner, and the results of evaluating the OD after the environmental test are also described.

Margins below C) ] 1"Lj Nao, discoloration is visually observed when ΔE° is around 10, and below that, discoloration is hardly noticeable.

As described above, the Examples using basic magnesium carbonates A-D containing acids other than carbonic acid had high image density and also had a sufficient indoor discoloration suppressing effect.

Further, the recording suitability of the recording media of Examples 1 to 4 did not change for one year under normal environment.

Example 5 The spherical basic magnesium carbonate E shown in Table 1 above was left as a powder in an environment of 60°C and R890% for one month, and the results shown in Table 4 below were carried out in the same manner as Examples 1 to 4. A recording medium was prepared according to the specifications and evaluated in the same manner as in Example 1. The results are shown in Table 5.

Support II Basis weight 100g/n (, thickness 1100u,
High-quality paper with a size degree of 2 seconds *1: Polyallylamine hydrochloride (PA
A-) ICI-3L) The inkjet recording suitability and indoor change of the above recording medium were evaluated in the same manner as in Example 1, and the results are shown in Table 5 below.

As shown in Table 5 and above, Example 5, which used basic magnesium carbonate E containing an acid other than carbonic acid, had high image density and also had a sufficient indoor discoloration suppressing effect.

Examples 6 to 9 Using spherical basic magnesium carbonate E and F, a support,
The pigment/binder ratio, additives, and coating amount were the same as in Example 5, and the pigments shown in Table 6 below were added to spherical basic magnesium carbonate F in the proportions shown in the same table as a ready-to-use powder. A recording medium was prepared in the same manner as in Example 1, except that it was left in an environment of 60° C. and FIH 90% for one month. The recording medium was subjected to an environmental exposure test and the results are shown in Table 7 below. As a result, the image density was sufficient and the effect of suppressing indoor discoloration was also large. Further, the inkjet recording suitability of the recording media of Examples 6 to 9 did not change even after environmental protection.

(Margin below) Table 6 Table 7 (Effects of the Invention) As shown above, according to the present invention, an inkjet recording medium and an inkjet recording that can provide a recorded image that has both image density and indoor discoloration resistance. A method is provided.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are a longitudinal cross-sectional view and a cross-sectional view of a head portion of an inkjet recording apparatus used in the method of the present invention. FIG. 2 is an external perspective view of a multi-head head shown in FIG. 1. FIG. 3 is a perspective view showing an example of an inkjet recording device. 61: Wiping member 62: Cap 63: Ink absorber 64/discharge recovery section 65: Recording head 66: Carriage Figure 1 (a) Figure 1 (b) Figure 2

Claims (4)

[Claims] (1) A recording medium characterized in that a layer containing basic magnesium carbonate containing an acid other than carbonic acid is provided on the support surface. (2) The recording medium according to claim 1, wherein the basic magnesium carbonate is spherical basic magnesium carbonate. (3) An inkjet recording method, comprising performing recording on the recording medium according to claim 1 by ejecting ink from an orifice of an inkjet recording head in accordance with a recording signal. (4) The inkjet recording method according to claim 3, wherein the ink is ejected using thermal energy.