JP2001293952A - Medium for ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a medium for ink jet recording, which excellent in ink absorbing property, surface glossiness, smoothness or the like and curl-preventing property in the atmosphere of a wide range. SOLUTION: The medium for ink jet recording is provided with an ink receiver layer on one side and a rear surface coated layer on the other side while 50 wt.% or more of a pigment in the rear surface coated layer is the plate- crystalline substance of amino silicic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording medium mainly composed of pulp such as paper.
The present invention relates to a sheet-shaped inkjet recording medium having excellent handling characteristics such as environmental curl prevention and transportability in addition to intrinsic characteristics such as ink absorption, image clarity, surface gloss and weather resistance.

[0002]

2. Description of the Related Art In recent years, with the spread of digital cameras and computers, hard copy technology for recording such images on paper or the like is rapidly demanded. The ultimate goal of these hard copies is silver halide photography. In particular, how to bring color reproducibility, image clarity, surface gloss, weather resistance, etc. close to silver halide photography has been an issue for development.

[0003] Hard copy recording methods include, in addition to a method of directly photographing a display displaying an image by a silver halide photograph, a sublimation heat transfer method, an ink jet recording method, and the like.
There are various types such as an electrostatic transfer method. Among them, the ink jet recording system has advantages such as a relatively small apparatus and low running cost, and is considered to be the mainstream of the hard copy system together with the sublimation type thermal transfer system and the like. In the ink jet recording method, ink droplets composed of a dye and a large amount of a solvent are ejected from a nozzle toward a recording medium at a high speed. 2. Description of the Related Art Printers based on the ink jet recording system have been rapidly spreading in recent years because they are easy to achieve full color and high speed and have low printing noise.

[0004] As the definition and speed of the ink jet recording system have been increased, the use thereof has been expanded and the environment in which the ink jet recording system is used has been expanded. Therefore, even for inkjet recording media,
In addition to essential properties such as ink absorbency, surface smoothness, clarity of the obtained image, and weather resistance, excellent properties in handling properties have been required.

[0005] In particular, when the support of the ink jet recording medium is a support such as paper mainly composed of pulp, the support has a large hygroscopic property unlike a plastic film or the like. Curling is greatly affected by changes in humidity. When curling occurs, not only a problem occurs during storage, but also a curl after printing in a rapid drying process after printing makes it difficult to use the printer. That is, when the ink jet recording medium is handled by the printer, the recording media adhere to each other, and the smooth transportability such as overlapping, skewing, and jamming is lost, thereby causing troubles in paper feeding and paper jam.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide ink-absorbing properties, image clarity, surface glossiness, weather resistance and other essential properties, as well as handling properties such as environmental curl prevention and transportability. The present invention provides a sheet-shaped ink jet recording medium excellent in quality.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an ink jet recording medium having an ink receiving layer containing a pigment and a binder on one surface of a support mainly composed of pulp. Having a back coating layer containing a pigment and a binder, wherein at least 50% by mass of the pigment in the back coating layer is a plate-like crystal of aluminosilicate. I will provide a.

In the ink jet recording medium according to the present invention, the above-described handling characteristics such as the prevention of environmental curl and the transportability based thereon are simultaneously solved. That is, the surface of the recording medium opposite to the surface having the ink receiving layer has 5
This can be achieved by providing a backside coating layer containing a pigment, which is a plate-like crystal of aluminosilicate in an amount of 0% by mass or more, and a binder. In the present invention, the plate-like crystal of aluminosilicate is a kind of kaolin group mineral,
Hexagonal plate-like crystals, kaolinite and deckite, are preferably used. These plate-like crystals are similar minerals of the kaolin family, and have excellent properties when used as the above-mentioned back coating layer of an ink jet recording medium, as compared with other crystal structures such as nacrylite and halloysite. Was found to show

For example, the above-mentioned back coating layer of an ink jet recording medium using kaolinite as a pigment not only has excellent curl prevention properties but also has a lower back coating as compared with, for example, a back coating layer using halloysite as a pigment. There are advantages such as high layer strength. This difference is due to the fact that kaolinite belongs to the same kaolin but has a different crystal form from halloysite, etc., and the former crystal form is a plate-like crystal, while the latter is a thin tube. It seems to be.

In the present invention, good results are obtained particularly when plate-like aluminosilicates having an aspect ratio of not less than a predetermined value are used. In this case, it is observed that the aluminosilicate plate-like crystals are regularly arranged horizontally in the layer direction in the coating layer, but the ease of this arrangement is due to the resistance to bending stress (rigidity). ) Is considered to suppress curling of the sheet-shaped recording medium.

Thus, according to the present invention, the prevention of environmental curl, which has conventionally been a problem with ink jet recording media containing pulp as a main component, has been greatly improved, handling characteristics have been improved, and usability in a printer has been improved. And to greatly increase its commercial value. Hereinafter, the present invention will be described in more detail.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION As a support used in the present invention,
A paper base mainly composed of pulp is used. The paper substrate is not particularly limited, and acidic paper, neutral paper, and the like used in the coated paper field are preferably used. As the pulp constituting the paper base material, a softwood pulp, a hardwood pulp, or a natural pulp mainly containing a mixed pulp thereof is preferably used. They are preferably used in bleached pulp such as kraft pulp, sulfite pulp, soda pulp and the like. Further, a paper substrate containing synthetic fibers or synthetic pulp can also be used. The basis weight of these substrates is
Although it is selected according to the application, it is preferably from 60 to 250 g / m ² . The paper base may contain various additives, for example, fillers, sizing agents, paper strength agents, pH adjusters, retention agents, and the like.

Further, the support in the present invention may be a coated paper in which a pigment coating layer comprising a pigment and a binder is provided on one or both sides of a paper substrate. As the coated paper, preferably, for example, cast coated paper,
One-sided or two-sided coated products such as super art paper, art paper, coated paper, super dull art paper, mat art paper, dull art paper, mat coated paper, dull coated paper and the like can be mentioned.

In the present invention, an ink-receiving layer is formed on the above-mentioned support. As the pigment used for forming the ink-receiving layer, any of inorganic substances, organic substances and polymer substances can be used. Among them, an inorganic oxide or a hydrate thereof is preferable. Preferred specific examples include silica, alumina, alumina hydrate, and mixtures or composites thereof. Of these, alumina hydrate is preferable because it absorbs and fixes the ink well. In particular, boehmite (Al ₂ O ₃ .nH ₂ O, n = 1
To 1.5) are preferred. Although various forms of alumina hydrate can be used, it is preferable to use sol boehmite as a raw material because a smooth layer can be easily obtained.

Since the ink receiving layer has sufficient ink absorbency and transparency, the average pore radius of the pore structure is preferably 3 to 25 nm, more preferably 5 to 15 nm. And the pore volume is preferably 0.
^{3 to} 2.0 cm ³ / g, especially 0.7 to 1.5 cm ³ / g
It is appropriate to have Thus, the ink receiving layer,
In particular, by increasing the transparency of alumina hydrate,
The color density can be increased and a clear image can be obtained. Especially, it is preferable that the pore radius is substantially distributed in the range of 1 to 50 nm. The pore radius distribution in the present invention is measured by a nitrogen adsorption / desorption method.

Examples of the binder used in the ink receiving layer include starch and modified products thereof, polyvinyl alcohol and modified products thereof, styrene / butadiene rubber latex, nitrile / butadiene rubber latex, methylcellulose, hydroxycellulose, hydroxymethylcellulose and carboxymethylcellulose. And water-soluble polymers such as gelatin, polyvinylpyrrolidone, polyacrylic acid and polyacrylamide, alcohol-soluble polymers, and mixtures of these polymers. In particular, in the present invention, use of polyvinyl alcohol or a modified product thereof is preferred because ink absorption and water resistance are good. The binder is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the pigment in the ink receiving layer.
In particular, it is appropriate to contain 3 to 15 parts by mass.

In the present invention, the coating amount of the ink receiving layer provided on the support is determined by the ink absorption, the strength of the coating layer,
It is also selected according to the application, but preferably, 1 to 10
0 g / m ² is adopted. If the coating amount is less than 1 g / m ² , the effect as an ink receiving layer is hardly exhibited, while if it exceeds 100 g / m ² , transparency and strength may be reduced, which is not preferable. In particular, the coating amount of the ink receiving layer is suitably from 5 to 50 g / m ² . In addition, the coating amount in the present invention is a value after drying after coating.

Means for providing the ink receiving layer on the support include, for example, a slurry prepared by adding a binder to a pigment, and a roll coater, an air knife coater, a blade coater, a rod coater, a bar coater, a comma coater, a gravure coater, a die coater. It is possible to adopt a method of applying and drying using a coater, a curtain coater, a spray coater or the like.

The surface of the ink receiving layer thus formed is further subjected to a temperature of preferably 0 to 160 ° C. using a device such as a super calender or a gloss calender.
In particular, the pressure is preferably 30 to 100 ° C., and the pressure is preferably 50 to 4
Gloss may be imparted by calendering by passing between rolls at 00 kN / m, particularly 100 to 250 kN / m. When forming the ink receiving layer, the gloss may be imparted by so-called cast coating in which the surface of the ink receiving layer is dried and released in contact with a smooth molding surface.

On the surface on the opposite side of the recording medium of the present invention having the ink receiving layer, a back coating layer is formed. The back coating layer contains a pigment, which is a plate-like crystal of aluminosilicate, in an amount of 50% by mass or more, and a binder. In the present invention, kaolinite or deckite represented by the chemical formula Al ₂ O ₃ .2SiO ₂ H ₂ O and having a plate-like crystal such as a hexagon is preferably used as the plate-like crystal of the aluminosilicate. . According to the findings of the present inventor, even with such a plate-like crystal, the aspect ratio (the size of the longest diagonal of the plate / the thickness of the plate) is related to curl suppression of the obtained recording medium, and the average aspect ratio is as follows: Preferably, particles having 3 or more, especially 5 to 80, have been found to be suitable. Further, the average particle diameter is preferably 0.1 to 5 μm, particularly preferably 0.2 to 3 μm, and these may be called clay.

The plate-like aluminosilicate used as a pigment in the back coating layer according to the present invention does not have to be entirely such a substance, but 50% by mass of the plate-like aluminosilicate is used. It turned out that it was necessary to be an object in terms of characteristics. Among them, it is preferable that 70% by mass or more, particularly 80% by mass or more of the pigment is a plate-like crystal of aluminosilicate. In the present invention, as the pigment used in combination with the aluminosilicate plate-like crystals, halloysite, kaolin minerals other than those applicable to the present invention, such as nacrites, light calcium carbonate, heavy calcium carbonate, talc, satin white, dioxide Titanium, zinc oxide, zinc carbonate, zinc sulfide, barium sulfate, calcium sulfate, calcium silicate, magnesium silicate, aluminum silicate, magnesium hydroxide, aluminum hydroxide, magnesium carbonate, hydrohaloisite, silica, alumina,
Examples include inorganic pigments such as alumina hydrate, urea resin-based, melamine resin-based, styrene-based, and acrylic pigments.

The plate-like aluminosilicate used in the present invention may be obtained naturally as a mineral,
By applying a shear force to such a natural product, especially by having a large aspect ratio by thinning,
What is called a delaminate clay or the like, or a naturally obtained mineral which is calcined to make bulky crystals and opaque can also be preferably used.

In the present invention, a binder selected from the above-mentioned binders for the ink receiving layer is used as the binder used for forming the back coating layer. Of these, the use of rubber-based latex such as styrene-butadiene rubber latex and nitrile-butadiene rubber latex is preferable because of the excellent adhesive strength of kaolinite. In addition, the amount of the binder used is selected from the same range as the above-described ink receiving layer.

In the formation of the back coating layer of the present invention, if necessary, other auxiliary agents such as an antifoaming agent, a dispersant, a water retention agent, a thickener, and a wetting agent may be added and used. Can be. Also,
In order to prevent mutual adhesion of recording media and improve transportability in a printer, a ratio of (average particle diameter of particles) / (thickness of back coating layer) besides the aluminosilicate plate-like crystals. Preferably contains particles having a particle size of 0.25 to 2.0. More preferably, such particles have a spherical or rounded shape. Preferred examples of these particles include organic spherical particles such as poly (meth) acrylate, polystyrene, nylon, starch, and cellulose, and inorganic spherical particles such as glass and silica. Among them, poly (meth) acrylate-based particles are particularly suitable.

The means for providing the back surface coating layer on the support is carried out in the same manner as the means for providing the ink receiving layer on the support. For example, a method in which a binder is added to the above-mentioned pigment and the above-mentioned particles used as needed to form a slurry, which is coated with an appropriate coater, and then dried.

The back coating layer and the ink receiving layer in the present invention can be formed in any order. However, in the case where the ink receiving layer is formed first and then the back coating layer is formed. However, it is preferable since the curl adjustment under normal temperature and normal humidity can be easily performed. Further, the coating amount of the back coating layer is determined in relation to the coating amount of the ink receiving layer, and the coating ratio of the back coating layer / ink receiving layer is 0.3%.
Preferably it is ~ 2.0. When the coating amount ratio is 0.
When it is smaller than 3, the curl suppressing effect in a wide range of environments becomes insufficient. On the other hand, when it exceeds 2.0, the curl toward the rear surface side becomes large. Above all, the above coating amount ratio is 0.1.
A case of 5 to 0.8 is appropriate. From the viewpoint of curling suppression in a wide range, the absolute amount of the coating amount of the back coating layer is preferably 1 to 60 g / m ² , particularly 5 to 40 g / m ² .
g / m ² is appropriate.

[0027]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the following, Examples 1 to 6 are examples of the present invention, and Examples 7 and 8 are comparative examples. Parts in the examples are parts by mass unless otherwise specified.

[Example 1] The following ink receiving layer formulation 1 was coated on one surface of a high-quality paper having a basis weight of 157 g / m ² with a bar coater, and the coated amount after drying was 20 g / m ^2. Then, by drying at 120 ° C., a sheet having an ink receiving layer (average pore radius: 10 nm, pore volume: 1.0 cm ³ / g) was obtained. Ink receiving layer formulation 1 ・ Alumina sol (manufactured by Catalyst Kasei Co., Ltd., trade name: Cataloid A
S-3): 100 parts ・ Polyvinyl alcohol (Kuraray Co., Ltd., trade name: PVA)
-124): 10 parts On the back side of the sheet having the ink receiving layer on one side, the following back side coating layer formulation 1 was applied using a bar coater so that the coating amount after drying was 8 g / m ^2. By drying at 120 ° C. for 2 minutes, a sheet having a coating layer on both sides was obtained. Back coating layer formulation 1 ・ Kaolinite (manufactured by JM HUBER, trade name: H
YDRAGLOSS 90 (average aspect ratio: about 7, average particle diameter 0.2 μm): 100 parts ・ Styrene butadiene latex (trade name: SN-307, manufactured by Sumika ABS Latex): 30
Part, ・ Antifoaming agent (manufactured by San Nopco, trade name: Formaster J)
K): 0.05 parts

Example 2 On the back side of the sheet having the ink receiving layer on one side in Example 1, the following back layer coating layer formulation 2 was applied:
Coating was performed using a bar coater so that the coating amount was 8 g / m ^2, and a sheet having coating layers on both surfaces was obtained in the same manner as in Example 1. Back coating layer formulation 2-Delamination clay (manufactured by JM HUBER, trade name: HYDRAPRINT, total content of kaolinite and deckite is 90% or more, average aspect ratio: about 30, average particle diameter: 0. 9 μm): 100 parts ・ Styrene butadiene-based latex (SN307):
30 parts ・ Defoamer (Fourmaster JK): 0.05 part

[Example 3] On the back side of the sheet having the ink receiving layer on one side in Example 1, the following backside coating layer formulation 3 was applied:
Coating was performed using a bar coater so that the coating amount was 8 g / m ^2, and the same procedure as in Example 1 was performed to obtain a sheet having a coating layer on both sides. Backside coating layer formula 3-Fired clay (manufactured by JM HUBER, trade name: H
YCAL, total content of kaolinite and deckite is 90% or more, average aspect ratio: about 15, average particle diameter: 0.4 μm): 100 parts, styrene butadiene latex (SN307):
30 parts ・ Defoamer (Fourmaster JK): 0.05 part

Example 4 A sheet having coating layers on both surfaces was obtained in the same manner as in Example 1 except that the following ink receiving layer formulation 2 was used as the ink receiving layer. Ink receiving layer formulation 2 • Silica sol (Nissan Chemical Co., trade name: Snowtex UP, average particle diameter: 45 nm): 100 parts • Polyvinyl alcohol (Kuraray Co., trade name: R-1)
130): 10 parts

Example 5 A sheet having a coating layer on both sides was obtained in the same manner as in Example 1 except that the following ink receiving layer formulation 2 was used as the ink receiving layer. Ink-receiving layer formulation 3-Amorphous silica (manufactured by Mizusawa Chemical Co., Ltd., trade name: P78A, average particle diameter 3.3 μm): 100 parts-Polyvinyl alcohol (manufactured by Kuraray, trade name: R-1)
130): 40 parts

Example 6 On the back surface of the sheet having the ink receiving layer on one side in Example 1, the following back coating layer formulation 4 was applied:
Coating was performed using a bar coater so that the coating amount was 8 g / m ^2, and the same procedure as in Example 1 was performed to obtain a sheet having a coating layer on both sides. Backside coating layer formulation 4 ・ Kaolinite (JM HUBER, trade name: H
YDRAGLOSS 90 (average aspect ratio: about 7, average particle diameter 0.2 μm): 70 parts; Light calcium carbonate (trade name: Bri, manufactured by Shiraishi Industry Co., Ltd.)
liant-SI, average aspect ratio: about 7, average particle diameter 0.2 μm): 30 parts, styrene-butadiene-based latex (SN-30)
7): 10 parts Antifoaming agent (Fourmaster JK): 0.05 part

Example 7 On the back side of the sheet having the ink receiving layer on one side in Example 1, the following back coating layer formulation 5 was applied:
Coating was performed using a bar coater so that the coating amount was 8 g / m ^2, and the same procedure as in Example 1 was performed to obtain a sheet having a coating layer on both sides. Back coating layer formulation 5-Light calcium carbonate (Shiraishi Industry Co., Ltd., trade name: Bri
lliant-S1, average aspect ratio: about 7, average particle diameter: 0.2 μm): 100 parts ・ Styrene butadiene-based latex (SN-30)
7): 10 parts Antifoaming agent (Fourmaster JK): 0.05 part

Example 8 On the back side of the sheet having the ink receiving layer on one side in Example 1, the following backside coating layer formulation 6 was applied:
Coating was performed using a bar coater so that the coating amount was 8 g / m ^2, and the same procedure as in Example 1 was performed to obtain a sheet having a coating layer on both sides. Backside coating layer formula 6 ・ Heavy calcium carbonate (Bihoku Powder Chemical Industry Co., Ltd., trade name: H
YDROCARB60, average aspect ratio: about 6, average particle diameter 1.5 μm): 100 parts, styrene butadiene latex (SN-30)
7): 30 parts ・ Antifoaming agent (manufactured by San Nopco, Formaster JK):
0.05 parts

With respect to the ink jet recording sheets of Examples 1 to 8, curl evaluation and strength evaluation of the back coating layer were conducted in the following environment, and the results are shown in Table 1. [Curl evaluation method] Under the following three conditions A to C, the recording sheet was allowed to stand for 24 hours with the ink receiving layer facing upward. The heights of the four corners of the recording sheet after the treatment from the horizontal plane were measured and averaged. The curl on the ink receiving layer side was defined as + (plus) curl, and the curl on the opposite side was defined as-(minus) curl. [Environmental conditions] Condition 1: Normal temperature and low humidity (20 ° C, 20% relative humidity) Condition 2: Normal temperature and normal humidity (20 ° C, 65% relative humidity) Condition 3: High temperature and high humidity (30 ° C, 80% relative humidity) [Curl Variation range] Curl value (unit: mm) of the above three environments
The difference between the maximum value and the minimum value was expressed.

[0037]

[Table 1] As shown in Table 1, the sheets of Examples 1 to 5, which are the ink jet recording sheets of the present invention, have excellent properties of suppressing curling in a wide range of environments as compared with the sheets of Examples 7 to 8. You can see that it is doing.

According to the present invention, the ink absorbency is high,
Provided is an ink jet recording sheet that can form a clear image, has excellent intrinsic properties such as surface gloss and smoothness, and has excellent curl prevention properties in a wide range of environments, and a method for producing the same.

Claims (5)

[Claims] 1. An ink jet recording medium having an ink receiving layer containing a pigment and a binder on one side of a support mainly composed of pulp, and a pigment and a binder on the other side. An ink jet recording medium having a backside coating layer containing at least 50% by mass of the pigment of the backside coating layer is a plate-like aluminosilicate. 2. The ink jet recording medium according to claim 1, wherein the aluminosilicate plate-like crystal is a hexagonal plate-like crystal made of kaolinite or deckite. 3. The ink receiving layer, wherein the pigment is alumina hydrate, the average pore radius is ³ to 25 nm, and the pore volume is 0.3 to 2.0 cm ³ / g. 1 or
3. The inkjet recording medium according to 2. 4. The ink jet recording medium according to claim 1, wherein the plate-like crystal of aluminosilicate has an average aspect ratio of 5 or more. 5. The ink jet recording medium according to claim 1, wherein the coating ratio of the back coating layer / ink receiving layer is from 0.3 to 2.0.