JP2000343814A - Manufacture of ink jet recording paper and ink jet recording paper manufactured by the manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a uniform dry coated face free from unevenness and provide a space type recording layer on which beading is hard to be generated, by setting the whole vertical distance of a carrying line for a substrate in a drying process to a specified value. SOLUTION: First, the whole vertical distance of a carrying line for a substrate in a drying process is set at 2 m or shorter. Then 450 L of a 20% water solution of a vapor phase process silica is added into 115 L of a water solution containing a 14 wt.% cationic polymer, 5 wt.% n-propanol and 2 wt.% ethanol and agitated therein, and the total amount dispersed under the 500 kg/cm2 pressure by a high voltage homogenizer is finished into 630 L of all pure water to prepare a transparent dispersed liquid. The liquid is filled by using a 30 μm filter, and then dispersed liquid is used and an additive is mixed therein, and a coating fluid is filtered by a 25 μm filter, and then so applied on a paper substrate with its both faces coated with polyethylene as to set the 200 μm and 150 μm wet film pressure on a paper substrate and the state of the film surface of a recording paper having varied vertical distance of a carrying line for a substrate and beading on the surface in the process are checked visually.

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 sheet (hereinafter, also simply referred to as a recording sheet) and a method for producing the same, and more particularly, to an ink jet recording sheet which is excellent in film surface condition and does not cause beading, and a method for producing the same. More particularly, the present invention relates to a method for producing an ink jet recording paper in which an aqueous coating composition containing inorganic fine particles and polyvinyl alcohol is applied to a continuously transported support and dried.

[0002]

2. Description of the Related Art In recent years, the image quality of ink jet recording has been rapidly improved, and the quality of photographs is approaching. In order to achieve such photographic quality with inkjet recording,
Improvements have also been made in the surface of recording paper, and recording paper provided with a microscopic void layer as an ink-absorbing material on a highly smooth support has the closest ink quality to photographic quality because of its high ink-absorbing and high-drying properties. It is becoming one of the things.

[0003] A high-smooth support is generally used as a polyester film, a polyolefin film, or a polyolefin-coated paper support.
A support that does not absorb ink. In providing an ink-absorbing void layer on such a non-ink-absorbing support, it is necessary to provide a thick-layer void layer in order to absorb ink sufficiently. Normally, when coating is performed so as to provide a void layer on such a non-ink-absorbing support, it is necessary to apply a dry film thickness of 30 μm or more, preferably 35 μm or more. When the coating is performed so that the film thickness of the void layer is 30 μm or more, the wet film thickness of the coating solution is 10 μm.
It is necessary to apply with a high wet film thickness of 0 μm or more, usually 130 μm or more. However, in the case of coating with such a high wet film thickness, there is no disclosure of a technique for coating and drying uniformly on a moving support without unevenness.

In recent years, a recording medium having a coating layer using an alumina hydrate having a boehmite structure has been proposed. For example, US Pat. No. 4,879,166, US Pat.
104,730, JP-A-2-276670, JP-A-3-275378, JP-A-3-281384,
No. 5-32037.

[0005] However, any of the proposals has an ink absorbing property,
Resolution, image density, color, color reproducibility, ink absorption,
This is related to improvement of transparency and the like, and even with such a proposal, beading is not improved or eliminated.

Here, beading generally occurs when the ink absorption speed in the ink receiving layer is low, and is visually recognized as color unevenness similar to a small circle. The size is generally about 0.2 to 2.0 mm, but in some cases, the size is out of the range. The name comes from the generally beaded shape.

This beading phenomenon is caused by the fact that the ink absorbing speed in the ink receiving layer is low during the process of absorbing the ink into the ink receiving layer, so that the ink remaining on the surface of the ink receiving layer attracts and repels the ink. Or move,
This creates high and low portions in the color density of the ink.
When observed after fixing the ink, the portion where the ink density is low is mostly a small circle, and frequently occurs in a portion where the ink ejection amount is large.

[0008] Regarding the ink absorption speed, beading tends to occur when the ink absorption speed is slow. However, when the ink absorption speed is too slow, the amount of ink remaining on the surface of the ink receiving layer becomes so large that repelling and shifting do not occur, and beading occurs. May not occur. However, in this case, the ink largely flows or mixes with nearby different color inks, resulting in a large disturbance of an image.

The frequency of occurrence of this beading varies depending on the type of the substrate on which the ink receiving layer is formed.

When the substrate has a liquid absorbing property, even if the solvent of the coating liquid is absorbed from the time of coating and the drying speed is increased to some extent,
Since the non-uniformity of the binder in the coating film does not become remarkable, beading hardly occurs. Further, in the image forming method, in the case of a substrate having high liquid permeability and absorptivity even when the ink is ejected to the ink receiving layer, the substrate itself can absorb the ink, thereby increasing the ink absorption speed. Become.

As described above, it is possible to suppress the occurrence of beading depending on the type of the substrate. However, the substrate of the ink-jet image receiving member is made of plastic, metal, glass, sintered ceramic, coated paper irrespective of transparency or opacity. There is also a strong need for materials having low permeability and absorption of liquid, such as art paper having a high surface gloss.

With respect to the ink absorbency of a recording medium having an ink receiving layer containing a pigment and a binder as main components, the above prior art has been improved from the viewpoint of the pore volume and the pore radius. Is not described, and beading is not sufficiently solved only by considering both the pore volume and the pore radius.

For example, US Pat. No. 5,104,730
JP-A-2-276670 and JP-A-2-27667.
Nos. 1 and 3-275378 disclose a recording medium having an average pore diameter of 10 to 30 angstroms and a narrow pore diameter distribution. Beading occurs due to insufficient absorption of the solvent.

Japanese Patent Application Laid-Open No. 3-281384 discloses an alumina hydrate which forms a hair-like aggregate having a columnar shape with an aspect ratio of 3 or less and oriented in a certain direction, and the alumina hydrate used. A method for forming an ink-receiving layer having good absorption and color is disclosed.

However, since the alumina hydrate particles are oriented and closely packed, the gap between the alumina hydrate particles in the ink receiving layer tends to be narrow. Therefore, the pore diameter tends to be narrower and the pore diameter distribution tends to be narrower. As a result, there is a problem that beading occurs.

Further, the method of increasing the pore volume of the pigment and improving the ink absorbency impairs the transparency of the ink image-receiving layer, causing haze and lowering the color density of the image.

Japanese Patent Application Laid-Open No. 1-133779 discloses a measure against beading by surface modification, but relates to a non-porous image receiving body. In the technical disclosure related to a porous image receiving body using a pigment, Absent.

As described above, although the prior art includes improvements in pigments and improvements in the formulation of selective coating solutions for binders, at present, there is no significant effect in preventing beading.

With respect to the beading of the recording medium, those which have been studied from the viewpoint of the manufacturing method are not well known, and particularly, the relationship between the manufacturing method and the ink jet recording characteristics is hardly known. It is the current situation.

Japanese Patent Application Laid-Open No. 63-170075 discloses the drying conditions of the coating layer by temperature and its gradient, but it discloses a technical purpose for film forming properties such as smoothness and crack prevention. There is no description about the ding.

[0021]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for producing an ink jet recording paper having a gap type recording layer which can form a uniform and dry coating surface without unevenness and in which beading does not easily occur. An object of the present invention is to provide an inkjet recording paper manufactured by a manufacturing method.

[0022]

The above object of the present invention is achieved by the following constitution.

1. In a method for producing an ink jet recording paper in which an aqueous coating composition containing inorganic fine particles and a water-soluble binder is applied to a moving support and dried, the total vertical distance of the transport path of the support in the drying step is 2 m or less. A method for producing an ink jet recording sheet, comprising:

2. 2. The method for producing an ink jet recording sheet according to the above item 1, wherein the total vertical distance of the conveying path of the support from the coating step to the drying step is 1 m or less.

3. In a method for producing an ink jet recording paper, in which an aqueous coating composition containing inorganic fine particles and a water-soluble binder is applied and dried on a moving support, after application, the coating is cooled, then dried, and supported in a cooling step. A method for producing an ink jet recording sheet, wherein the total vertical distance of the body conveyance path is 1.5 m or less.

4. 4. The method for producing an ink jet recording sheet according to the item 3, wherein the total vertical distance of the transport path of the support from the application step to the cooling step is 1 m or less.

5. 5. The method for producing an ink jet recording sheet according to any one of the items 1 to 4, wherein the inorganic fine particles are alumina hydrate.

6. 5. The method for producing an ink jet recording sheet according to any one of the items 1 to 4, wherein the inorganic fine particles are silica.

7. The method for producing an ink jet recording sheet according to any one of the above items 1 to 6, wherein the water-soluble binder is polyvinyl alcohol.

8. In an ink jet recording paper containing inorganic fine particles and polyvinyl alcohol,
8. An ink jet recording paper manufactured by using the method for manufacturing an ink jet recording paper according to any one of items 7 to 7.

Hereinafter, the present invention will be described in detail.

The aqueous coating composition of the present invention contains inorganic fine particles. Examples of the inorganic fine particles include, for example, light calcium carbonate, heavy calcium carbonate, magnesium carbonate,
Kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate,
Synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide,
Examples include white inorganic pigments such as lithopone, zeolite, magnesium hydroxide, and alumina hydrate.

Such inorganic fine particles can be used as they are as primary particles or in a state where secondary aggregated particles are formed.

Particularly preferred pigments from the viewpoint of resolution suitability such as ink absorption and resolution characteristics are alumina hydrate,
It is silica. Alumina hydrate is more preferable as a pigment used for the ink receiving layer because it has a positive charge and thus fixes the dye in the ink well, and provides an image with high gloss, high image density and good color development.

The alumina hydrate preferably used in the present invention is preferably represented by the following general formula (1).

Formula (1) Al ₂ O ₃ n (OH) ₂ n · mH ₂ O In the formula (1), n represents an integer of 0, 1, 2 or 3, and m represents an integer of 0 to 10. , Preferably an integer of 0 to 5. Since mH ₂ O often represents a detachable aqueous phase that is not involved in the formation of a crystal lattice, m can take a non-integer value. Further, when this kind of alumina hydrate is calcined, m may reach a value of 0.

The alumina hydrate suitable for carrying out the present invention is an amorphous alumina hydrate analyzed by an X-ray diffraction method.
No. 5438, No. 5-125439, No. 6-11457
It is preferable to use the alumina hydrate described in No. 1.

In the present invention, as the inorganic fine particles, fine particle silica synthesized by a gas phase method is also preferable because the low-temperature viscosity is easily increased.

The fine particle silica synthesized by the gas phase method is usually a silica powder having a primary particle diameter of 5 to 500 nm obtained by burning silicon tetrachloride with hydrogen and oxygen at a high temperature.
In the present invention, those having a primary particle diameter of 50 nm or less are particularly preferable from the viewpoint of glossiness.

Examples of such fumed silica which are currently commercially available include various types of Aerosil manufactured by Nippon Aerosil Co., Ltd.

The silica synthesized by the above gas phase method is
The surface may be cationically modified,
Further, it may be one that has been treated with Al, Ca, Mg, Ba, or the like, or one that has a part of its surface rendered hydrophobic.

Any particle diameter can be used for the inorganic fine particles, but the average particle diameter is 1 μm so that the viscosity change can be greatly changed with the temperature change of the coating solution.
m or less, and particularly preferably 0.2 μm or less.

Although the lower limit of the particle size is not particularly limited, it is usually preferably at least 3 nm, particularly preferably at least 6 nm from the viewpoint of production of the particles.

In the above, the average particle diameter of the inorganic fine particles is determined by observing the cross section or surface of the particles themselves or the void layer with an electron microscope, obtaining the particle diameter of 100 arbitrary particles, and calculating the simple average value (number average). Desired. Here, each particle size is represented by a diameter assuming a circle equal to the projected area.

The content of the inorganic fine particles in the water-based coating composition is usually from 3% by weight to 20% by weight from the viewpoint of increasing the viscosity at a low temperature and maintaining an appropriate viscosity at the time of coating. 5 to 15% by weight is preferred.

In the aqueous coating composition of the present invention, a water-soluble binder is used as a binder.

Examples of the water-soluble binder include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, carrageenan (λ, ι, λ, etc.), agar, pullulan, and water-soluble polyvinyl. Butyral, hydroxyethyl cellulose,
Examples thereof include carboxymethylcellulose, and among them, polyvinyl alcohol is preferable.

The polyvinyl alcohol includes not only ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, but also modified polyvinyl alcohol such as polyvinyl alcohol having a cation-modified terminal or anion-modified polyvinyl alcohol having an anionic group. It is.

The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 300 or more, and particularly preferably has an average degree of polymerization of 1,000 to 4,000.

The degree of saponification is preferably from 70 to 100%, particularly preferably from 80 to 99.5%.

As the cation-modified polyvinyl alcohol, for example, a tertiary amino group or a quaternary ammonium group as described in JP-A-61-10483 can be used in the main chain or side chain of the polyvinyl alcohol. Which is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl). Ammonium chloride, N-vinylimidazole, N-vinyl-2-methylimidazole, N
-(3-dimethylaminopropyl) methacrylamide,
Hydroxyethyltrimethylammonium chloride,
Trimethyl-(-methacrylamidopropyl) ammonium chloride, N- (1,1-dimethyl-3-dimethylaminopropyl) acrylamide and the like.

The ratio of the cation-modified polyvinyl alcohol-containing monomer having a cation-modified group is 0.1 to vinyl acetate.
It is 1 to 10 mol%, preferably 0.2 to 5 mol%.

The anion-modified polyvinyl alcohol is, for example, a polyvinyl alcohol having an anionic group as described in JP-A-1-206088;
Copolymers of vinyl alcohol and a vinyl compound having a water-soluble group, as described in JP-A-1-237681 and JP-A-63-307979, and JP-A-7-2852.
No. 65, a modified polyvinyl alcohol having a water-soluble group.

Examples of the nonion-modified polyvinyl alcohol include polyvinyl alcohol derivatives having a polyalkylene oxide group added to a part of vinyl alcohol as described in JP-A-7-9758, and JP-A-8-25795. And a block copolymer of a vinyl compound having a hydrophobic group and a vinyl alcohol.

Two or more kinds of polyvinyl alcohols such as different degrees of polymerization and different types of modification can be used in combination.

The content of the above polyvinyl alcohol in the aqueous coating composition of the present invention can vary widely depending on the type of polyvinyl alcohol and the type and amount of the inorganic fine particles, but is usually 0.1 to 10% by weight. , 0.3-5% by weight
Is particularly preferred.

The ratio of the inorganic fine particles to polyvinyl alcohol is preferably 3 to 10 by weight. If it is less than 3, the thickening at low temperatures will be small, and if it exceeds 10, the coated film will be too brittle and it will be difficult to obtain a good coated surface.

The aqueous coating composition of the present invention preferably contains polyvinyl alcohol as a main binder. However, if the effect of the present invention, that is, an increase in low-temperature viscosity is not significantly adversely affected, the above-mentioned water-soluble coating composition is naturally used. Anionic binders can also be used.

Preferably, the water-soluble binder is usually 20% by weight or less, particularly preferably 10% by weight or less, based on polyvinyl alcohol.

The pH of the aqueous coating composition has a relatively large effect on the surface charge state of the inorganic fine particles and the degree of hydration of the hydroxyl group of polyvinyl alcohol, and is preferably in the range of pH 3.5 to 6.0. .

When the pH is less than 3.5, the width of thickening at a low temperature decreases, and when the pH exceeds 6, the interaction in the coating solution becomes too strong to cause agglomeration. Gelation easily occurs even in a high temperature state.

A particularly preferred pH range is from 3.5 to 5.5.
It is.

The compound for adjusting the viscosity of the aqueous coating composition of the present invention includes a surfactant, a water-miscible organic solvent and a polymer latex.

Among them, the surfactant and the water-miscible organic solvent are used as means for lowering the viscosity of the coating composition. On the other hand, the polymer latex is used as a means for increasing the viscosity.

The surfactant is a cationic surfactant or a nonionic surfactant when the coating composition is cationic, and a nonionic surfactant or anionic surfactant when the coating composition is anionic. Used. The amount of the surfactant varies widely depending on the viscosity to be adjusted, but is generally 0.01 to 10 g per liter of the coating composition.

As the water-miscible organic solvent, methanol,
Alcohols such as ethanol, n-propanol and i-propanol; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate and propyl acetate;
Examples include amides such as N-dimethylformamide, and polyols such as ethylene glycol, diethylene glycol, and glycerin.

The amount of the water-miscible organic solvent to be used is generally 0.1 to 20 ml per liter of the aqueous coating composition.

Various latexes such as silicone oil, acrylic latex and urethane latex can be used as the polymer latex.

Various additives other than those described above can be added to the aqueous coating composition of the present invention.

Among them, a cationic mordant is preferable for improving water resistance and moisture resistance after printing. As the cationic mordant, a polymer mordant having a primary to tertiary amino group and a quaternary ammonium group is used, and the discoloration and deterioration of light resistance with time are small, and the mordant ability of the dye is sufficiently high. Therefore, a polymer mordant having a quaternary ammonium base is preferred.

Preferred polymer mordants include homopolymers of the above-described monomers having a quaternary ammonium salt group, and copolymers or condensation polymers with other monomers.

Other than the above, for example, Japanese Patent Application Laid-Open No. 57-7419
Nos. 3, 57-87988 and 62-261476
UV absorber described in JP-A-57-74192,
No. 57-87989, No. 60-72785, No. 61
146951, JP-A-1-95091 and 3-
13376, various anionic, cationic or nonionic surfactants described in JP-A-13376, etc .;
9-42933, 59-52689, 62-2
No. 80069, No. 61-242871 and JP-A-Hei.
Known various additives such as a fluorescent whitening agent, an antifoaming agent, a lubricant such as diethylene glycol, a preservative, a thickener, an antistatic agent, a matting agent and the like described in 219266 and the like can be contained.

As the support to be used, any known supports can be used, but preferred supports are those which do not absorb the moisture of the coating composition.

Examples of such non-water-absorbing supports include polyester films, diacetate films, triacetate films, acrylic films,
Polycarbonate film, polyvinyl chloride film, polyimide film, transparent film made of a material such as cellophane or celluloid, or resin-coated paper having a polyolefin resin coating layer obtained by adding a white pigment or the like to at least one of base paper (so-called RC Paper), and a translucent or opaque support such as a so-called white pet obtained by adding a white pigment such as titanium oxide or barium sulfate to polyethylene terephthalate.

In applying the coating composition of the present invention to the support, the support is subjected to a corona discharge treatment, a subbing treatment, or the like for the purpose of increasing the adhesive strength between the surface and the coating layer. Is preferred. Further, the recording paper of the present invention does not necessarily need to be colorless, and may be a colored support.

The support particularly preferably used in the present invention is a transparent polyester film, an opaque polyester film, an opaque polyolefin resin film, and a paper support in which both sides of a base paper support are laminated with polyethylene.

Particularly preferred is a paper support laminated with polyethylene, as described below.

The base paper used for the paper support is made of wood pulp as a main raw material, and if necessary, in addition to wood pulp, synthetic pulp such as polypropylene or synthetic fiber such as nylon or polyester. As wood pulp, LBKP, LBSP, NBKP, NBSP, LD
Any of P, NDP, LUKP, and NUKP can be used, but LBKP, NBSP, and LBS containing a large amount of short fibers
It is preferable to use more P, NDP, and LDP.
However, the ratio of LBSP and / or LDP is preferably 10% by weight or more and 70% by weight or less.

As the pulp, a chemical pulp containing less impurities (sulfate pulp or sulfite pulp) is preferably used.
Further, pulp having improved whiteness by performing a bleaching treatment is also useful.

In the base paper, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength agents such as starch, polyacrylamide and polyvinyl alcohol, fluorescent whitening agents, Water retention agents such as polyethylene glycols, dispersants, and softening agents such as quaternary ammonium can be appropriately added.

The freeness of the pulp used for papermaking is preferably 200 to 500 ml according to the CSF standard, and the fiber length after beating is 24% by weight of the remaining 24 mesh specified in JIS-P-8207. The sum with the calculated weight% is 3
0-70% is preferred. The weight percentage of the remaining 4 mesh
Is preferably 20% by weight or less.

The basis weight of the base paper is preferably 30 to 250 g,
Particularly, 50 to 200 g is preferable. Base paper thickness is 40-2
50 μm is preferred.

The base paper may be calendered at the papermaking stage or after the papermaking to provide high smoothness. The base paper density is 0.
7 to 1.2 g / m ² (JIS-P-8118) is common. Further, the rigidity of the base paper is preferably from 20 to 200 g under the conditions specified in JIS-P-8143.

A surface sizing agent may be applied to the surface of the base paper. As the surface sizing agent, the same sizing agent as can be added to the base paper can be used.

The pH of the base paper is preferably 5 to 9 when measured by the hot water extraction method specified in JIS-P-8113.

The polyethylene covering the front and back surfaces of the base paper is mainly composed of low-density polyethylene (LDPE) and / or
Or high density polyethylene (HDPE) but other L
LDPE, polypropylene and the like can also be partially used.

In particular, the polyethylene layer on the coating layer side is preferably one in which rutile or anatase type titanium oxide is added to polyethylene to improve opacity and whiteness, as is widely used in photographic printing paper. The content of titanium oxide is approximately 3 to 20% by weight, preferably 4 to 13% by weight, based on polyethylene.

The polyethylene-coated paper may be used as glossy paper, or may be subjected to a so-called embossing process when the polyethylene is melt-extruded onto the surface of the base paper and subjected to a so-called molding process to obtain a matte surface or a silk surface which can be obtained with ordinary photographic printing paper. Those having a surface can also be used in the present invention.

The amount of polyethylene used on the front and back of the base paper is selected so as to optimize the film thickness of the aqueous coating composition and the curl under low and high humidity conditions after providing the back layer. The polyethylene layer on the side to which the coating composition is applied is 20
４０40 μm, and the thickness of the back layer is 10-30 μm.

Further, the polyethylene-coated paper support preferably has the following characteristics.

Tensile strength: The strength specified in JIS-P-8113 is 2 to 30 kg in the vertical direction and 1 to 1 in the horizontal direction.
20 kg is preferable. Tear strength: 10 to 200 g in the longitudinal direction and 20 to 200 g in the horizontal direction are preferable according to the method specified in JIS-P-8116. Compressive modulus ≧ 103 kgf / cm ² is preferable. Surface Beck smoothness: JIS-P-8119. 20 seconds or more is preferable as a glossy surface under the conditions specified in (1), but may be less than this for so-called molded products. Opacity: Transmission of visible light rays under the measurement conditions of linear light incidence / diffuse light transmission conditions The rate is preferably 20% or less, particularly preferably 15% or less.

The aqueous coating composition of the present invention may have one layer or two or more layers on the same side of the support. When there are multiple layers, one of them may not be a void layer, but when simultaneously coated, it is formed from a coating composition having a property of thickening or gelling at a low temperature from the viewpoint of coating. preferable.

The method of applying the aqueous coating composition of the present invention can be appropriately selected from known methods. A preferred method is obtained by applying a coating solution constituting one or more layers on a support and drying the coating solution. In the case of a multi-layer structure, two or more layers can be applied simultaneously, and in particular, simultaneous application in which all the hydrophilic binder layers need only be applied once is preferable.

The coating method is preferably a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method or an extrusion coating method using a hopper described in US Pat. No. 2,681,294. Used.

In the present invention, the total vertical distance (Ct ₁ ) of the conveying path of the support in the drying step is C ₁ + C ₂ in FIG.
It is represented by the distance of In the present invention, Ct ₁ is 2 m or less.

In the present invention, the total vertical distance (C) of the support transport path from the coating step to the drying step is represented by the distance C in FIG. In the present invention, C is 1 m
The following is preferred.

In the present invention, the total vertical distance (Dt ₁ ) of the conveyance path of the support in the cooling step is represented by D ₁ + D ₂ in FIG.
It is represented by the distance of In the present invention, Dt ₁ is 1.5 m
It is as follows.

In the present invention, the total vertical distance (D) of the conveyance path of the support from the coating step to the cooling step is represented by the distance D in FIG. In the present invention, D is 1 m
The following is preferred.

The temperature at which the aqueous coating composition of the present invention is applied is preferably 35 to 50 ° C., and 36 to 4 ° C.
It is particularly preferred to apply at 8 ° C.

The viscosity of the coating composition of the present invention is relatively low at the time of coating, and is 10 to 100 cp at 40 ° C.
Are preferred from the viewpoint of high-speed coating.

A third aspect of the present invention is characterized in that a cooling step is provided after coating. The cooling temperature is usually preferably set to 20 ° C. or lower, particularly preferably 15 ° C. or lower.

The cooling in the present invention means that the coated sample is
Preferably, a cooling step of 10 ° C. or less is passed for a certain period of time (preferably, 5 seconds or more). At the time of this cooling, it is preferable not to blow a very strong wind because liquid twisting does not occur.

As a cooling method, an arbitrary cooling method such as a cooling method using an air current or a cooling roll method can be selected.

After cooling once, even if a strong wind is blown, the liquid is hardly twisted due to the thickening of the coating solution itself, and even if the strong wind is blown, the generation of the liquid twist can be suppressed. Also,
The temperature of the strong wind to be blown can be a wind of 20 ° C. or more, but it is preferable to gradually raise the temperature of the wind.

As a drying method, not only a flash drying method but also an arbitrary drying method such as a microwave drying method, an infrared drying method and a freeze drying method can be selected.

The drying time depends on the wet film thickness, but is usually preferably within 10 minutes or 5 minutes.

The coating speed depends on the wet film thickness and the drying ability of the equipment, but is usually 10 to 1000 m, preferably 20 to 500 m per minute.

On the side opposite to the side to which the aqueous coating composition of the present invention is applied, various types of back layers may be provided in order to prevent curling, to further improve sticking when superimposed immediately after printing, and to further improve ink transfer. preferable.

Although the structure of the back layer varies depending on the type and thickness of the support and the structure and thickness on the front side, a hydrophilic binder or a hydrophobic binder is generally used. The thickness of the back layer is usually in the range of 0.1 to 10 μm.

The surface of the back layer can be roughened in order to prevent sticking to other recording papers, improve writing properties, and improve transportability in an ink jet recording apparatus. Organic or inorganic fine particles having a particle size of 2 to 20 μm are preferably used for this purpose. These back layers may be provided in advance, or may be provided after applying the coating composition of the present invention.

[0112]

EXAMPLES The present invention will be described below in more detail with reference to examples, but embodiments of the present invention are not limited thereto.

Example 1 The average particle diameter of the primary particles dispersed uniformly in advance is about 0.1.
012 μm fumed silica (manufactured by Nippon Aerosil Co., Ltd .:
A200) of 450 liters of a 20% aqueous solution A1 (pH = 2.3, containing 1% by weight of ethanol) was added to an aqueous solution C1 containing 14% by weight of a cationic polymer, 5% by weight of n-propanol, and 2% by weight of ethanol (pH: 2.3). = 2.5,
The mixture was added to 110 liters of an antifoaming agent SN381 manufactured by Sannobuco (containing 2 g) while stirring at room temperature.

Then, the mixture was dispersed at a pressure of 500 kg / cm ² with a high-pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd.
After finishing to 30 liters, an almost transparent dispersion B1 was obtained.

This dispersion has a filtration accuracy of 30 μm.
Filtration was performed using a TCP-30 type filter manufactured by Advantex Toyo.

Next, the following additives were sequentially mixed using the above-mentioned dispersion to prepare a coating solution (CS1) (the amount of each solution prepared was 1 liter).

Silica dispersion B1 580 ml Polyvinyl alcohol (PVA235, Kuraray) 5% aqueous solution 250 ml Silicon dispersion (BY-22-839, manufactured by Dow Corning Silicone Toray) 30 ml Latex dispersion (manufactured by Showa Kogyo Kogyo Co., Ltd.) AE803) 20 ml Ethanol 8.5 ml Pure water (finish the total amount to 1000 ml) The pH of CS1 of the obtained coating composition was 4.2 at 40 ° C.

Next, each coating solution was filtered three times with a 25 μm filter, and then applied onto a paper support (240 μm thick) coated on both sides with polyethylene so that the wet film thickness was 200 μm and 150 μm. After the coating, the state of the film surface of the recording paper and the beading of the recording paper surface obtained by changing the total vertical distance (Ct ₁ ) of the conveyance path of the support in the drying step were visually evaluated. The results are shown.

The evaluation of the coating film surface (visual observation) is as follows. The wet film thickness (μm) is 200 μm.

：: Smooth and good ○: Cracks occurred at the end ×: Cracks, unevenness occurred over the whole area Evaluation of beading Ink jet recording after solid printing of Y, M, C, and Bk inks of the following composition in single color or multicolor The beading on the paper surface was visually evaluated. The ink amount for monochromatic printing is 10
0%.

◎: When not generated at 300% of ink amount, ：: When not generated at 200% of ink amount, ×: When generated, ×: When frequently generated ink composition Ink Dye 5 parts ・ Ethylene glycol 10 parts ・ Polyethylene glycol 10 parts ・ Water 75 parts Ink dye Y: C.I. I. Direct Yellow 86 M: C.I. I. Assid Red 35 C: C.I. I. Direct Blue 199 Bk: C.I. I. Food black 2

[0122]

[Table 1]

Example 2 Alumina hydrate was used as a pigment. The specific surface area and the pore volume are 200.2 m ^{2 /} g and 0.71 ml / g, respectively.
Met.

The specific surface area is the BET specific surface area,
It was calculated using the method of er et al.

The pore volume was measured by a nitrogen adsorption / desorption method after degassing at 120 ° C. for 24 hours (Autosoap I, manufactured by Cantachrome).

The production method is described in US Pat. No. 4,242,27.
An aluminum alkoxide is produced by the method described in No. 1. Next, the aluminum alkoxide was hydrolyzed by the method described in U.S. Pat. No. 4,202,870 to produce an alumina slurry. Water was added to the alumina slurry until the alumina hydrate solid content became 7.9%. The pH of the alumina slurry was 9.5. 3.
The pH was adjusted to 6.8 by adding a 9% nitric acid solution. This was aged at 110 ° C. for 6 hours to obtain a colloidal sol. Alumina hydrate obtained by spray drying this colloidal sol at 75 ° C. was used.

After this alumina hydrate was dispersed in ion-exchanged water, polyvinyl alcohol (Kuraray PVA23) was used.
An aqueous solution of ion-exchanged water in which 5) was dissolved was added. At this time, the solid content weight of alumina hydrate / the solid content amount of polyvinyl alcohol (pigment / binder = P / B) was 13 /
The mixture was measured, added, mixed and stirred so as to obtain a dispersion liquid of 1, and a coating liquid was obtained. Next, the obtained coating solution was filtered three times with a 25 μm filter, and then a wet film thickness of 25 μm was formed on a paper support (thickness: 240 μm) coated on both sides with polyethylene.
0 μm was applied. After coating, the film thickness of the recording paper obtained by changing the total vertical distance (Ct ₁ ) of the support transport path in the drying step and the vertical distance (C) of the support transport path from the coating step to the drying step. The state of the surface and the beading of the recording paper surface were visually evaluated in the same manner as in Example 1, and the results are shown below. The wet film thickness was 250 μm.

[0128]

[Table 2]

Example 3 In Example 1, the wet film thickness was set to 310 μm, and a cooling step was provided before the drying step to solidify the coated material before drying. The total vertical distance (Dt ₁ ) and the total vertical distance (D) of the conveyance path of the support from the coating step to the cooling step were changed. The results of the visual evaluation of the state of the film surface and the beading of the recording paper surface as in Example 1 are shown below.

[0130]

[Table 3]

Example 4 In Example 3, the wet film thickness was set to 330 μm, and the total vertical distance (D ₁ + D ₂ ) of the conveying path of the support in the cooling step was changed. The state of the film surface of the recording paper obtained and the beading of the recording paper surface were visually evaluated in the same manner as in Example 1, and the results are shown below. The solid weight of alumina hydrate / the solid content of polyvinyl alcohol (pigment / binder = P / B) was 10/1.
Further, the total vertical distance (D) of the conveying path of the support from the coating step to the cooling step was 0.3 m.

[0132]

[Table 4]

[0133]

According to the present invention, as demonstrated in the examples,
The method for producing an ink jet recording sheet and the ink jet recording sheet produced by the method can provide an ink jet recording sheet which can form a uniform coated and dried surface without unevenness and has a void-type recording layer in which beading does not easily occur. It has the effect.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating an example of a method for manufacturing an ink jet recording sheet of the present invention.

FIG. 2 is a schematic view illustrating an example of a method for manufacturing an ink jet recording sheet of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coating process 2 Coater 3 Coating start part 4 Support 5 Drying process entrance 6 Drying process outlet 7 Coating process 8 Drying roller highest part 9 Cooling process inlet 10 Cooling process outlet 11 Cooling process 12 Cooling roller highest part

Claims (8)

[Claims] 1. A method for producing an ink jet recording paper in which an aqueous coating composition containing inorganic fine particles and a water-soluble binder is applied to a moving support and dried, wherein the total vertical distance of the transport path of the support in the drying step is reduced. A method for producing an ink jet recording sheet, which is not more than 2 m. 2. The method for producing an ink jet recording sheet according to claim 1, wherein the total vertical distance of the support transport path from the coating step to the drying step is 1 m or less. 3. A method for producing an ink jet recording paper in which an aqueous coating composition containing inorganic fine particles and a water-soluble binder is applied to a moving support and dried, followed by cooling after application, drying, and A method for producing an ink jet recording sheet, wherein the total vertical distance of the conveying path of the support in the cooling step is 1.5 m or less. 4. The method for producing an ink jet recording sheet according to claim 3, wherein the total vertical distance of the support conveying path from the coating step to the cooling step is 1 m or less. 5. The method for producing an ink jet recording sheet according to claim 1, wherein the inorganic fine particles are alumina hydrate. 6. The method according to claim 1, wherein the inorganic fine particles are silica. 7. The method for producing an ink jet recording sheet according to claim 1, wherein the water-soluble binder is polyvinyl alcohol. 8. An ink jet recording sheet containing inorganic fine particles and polyvinyl alcohol.
8. An ink jet recording paper manufactured by using the method for manufacturing an ink jet recording paper according to any one of items 7 to 7.