JP3353925B2 - Ink jet recording sheet and method for producing the same - Google Patents

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 for recording using ink and a method for producing the same. The present invention relates to an ink jet recording sheet having improved density unevenness and a method for producing the same.

[0002]

2. Description of the Related Art Ink-jet recording is a method in which minute droplets of ink are made to fly and adhere to a recording sheet such as paper by various operating principles to record images and characters. It has features such as easy multi-coloring, great flexibility in recording patterns, and no need for development-fixing.
As a recording device for various figures and color images including complicated characters such as kanji, it has rapidly spread in various uses. Further, an image formed by the multi-color ink jet method can obtain image quality having a gradation property comparable to multi-color printing by a plate making method or printing by a color photographic method. In addition, in applications requiring a small number of copies, it is being widely applied to the field of full-color image recording because it is less expensive than the photographic technique.

An ink jet recording sheet used in this ink jet recording system needs to satisfy the following characteristics. There should be no uneven printing density in the image area. The print dot density is high, and the color tone is bright and vivid.

Heretofore, as an ink jet recording sheet having these characteristics, a coat type ink jet recording sheet in which an ink receiving layer is provided on the surface of a support such as paper such as high quality paper, synthetic paper, and synthetic resin film has been developed. Was.

[0005] The ink receiving layer is a coating layer obtained by applying and drying a coating liquid of an ink receiving layer obtained by adding a binder to a dispersion of an inorganic pigment onto a support, absorbing the ink and fixing it as an image. It is provided for the purpose. Here, the structural conditions of the ink receiving layer for satisfying the above-described characteristics are as follows. The thickness of the coating layer is uniform, and no coating unevenness or coating defects occur. The binder in the ink receiving layer liquid does not selectively penetrate into the support.

[0006] The uniform thickness of the coating layer of the ink receiving layer means that the ink absorbing property is uniform when the ink receiving layer has the same amount of ink to be received in the plane direction. Further, when the thickness of the coating layer is not uniform, it means that the image density becomes uneven. Further, coating defects observed as partial coating unevenness also cause image density unevenness.

When the binder contained in the coating solution of the ink receiving layer selectively penetrates into the support, the ratio of the binder in the ink receiving layer becomes low, and the ink absorption proceeds excessively, and the In addition to lowering the density of the ink, the sharpness of the color tone also decreases, and the binder that has permeated the support inhibits the absorption of the ink into the support, so that the ink easily penetrates in the surface direction in the ink receiving layer. And the sharpness of the image is reduced. Further, the penetrated ink reaches the back surface or the vicinity of the back surface, and an obstacle called “show-through” occurs in which an image on the front surface is reflected on the back surface.

However, when a conventionally used liquid supply section and a measuring section are separated and a measuring type coating apparatus or a roll coating apparatus is used for applying the coating liquid of the ink receiving layer, such ink receiving layer is not used. An ink jet recording sheet having an ink receiving layer satisfying the structural requirements of the layer could not be obtained.

In other words, when a blade coating method or a rod coating method is used, an ink receiving layer having a relatively smooth surface shape can be obtained. However, paper made from pulp or synthetic fiber is used as a support. In this case, an uneven coating amount corresponding to the surface shape of the support is generated. Further, in such a coating method, coating defects such as streaks and scratches are likely to occur in the operation of the coating layer, and an ink receiving layer having a uniform coating amount cannot be obtained.

In this coating method, the binder component in the coating liquid infiltrates the web more than necessary between the supply of the excess liquid and the measurement, and furthermore, the coating liquid at the tip of the blade or the rod contacting part. On the other hand, since a high pressure is applied, the penetration of the binder proceeds further. This not only lowers the image density and sharpness, but also the liquid scraped off as a surplus differs from the composition of the liquid before supply, so that the composition of the coating liquid changes over time and is stable. You cannot get a quality product.

In the air knife coating method, it is inevitable that a pattern peculiar to the air knife is generated in the coating layer, and an ink receiving layer having a uniform coating amount cannot be obtained. Similarly, even in various roll coating apparatuses, when the coating liquid is transferred from the roll to the support, it is inevitable that uneven coating amount called a split pattern occurs.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink receiving layer having a uniform coating amount, which cannot be obtained by the conventional coating method, and to select a binder contained in the ink receiving layer liquid on a support. An object of the present invention is to obtain an ink jet recording sheet having no print density unevenness in an image area and having a high print density and sharp image quality due to non-absorption.

[0013]

The present invention SUMMARY OF] is a coating solution viscosity of the ink-receiving layer and 40～2000Cps, the surface tension of the coating liquid, as 23~55dyne / cm, a coating solution onto a support coater Head from manifold and slit
By using the extrusion type curtain coating apparatus, it is possible to obtain an ink jet recording sheet having no print density unevenness in an image area, high print density, and sharp image quality.

Coater head is manifold and slit
The extrusion type curtain coating device is a pre-metering type coating device, in which the measurement of the liquid is completed before coating on the support, and the curtain film is a free surface on both surfaces, One feature is that one side is stretched by contact with the support at the time of coating to form a coating layer film, so that there is no restriction on the flow path at the time of coating. That is, since a uniform liquid film is stretched to become a coating layer film, the coating layer film has an extremely uniform thickness regardless of the shape of the support.

However, in the case of curtain coating, the occurrence of a coating failure phenomenon as described below may be observed. Air entrainment in which air enters between the coating layer and the surface of the support. A phenomenon in which the coating liquid repels the substrate without getting wet.

When the air entrainment phenomenon occurs, the entrained air becomes bubbles, expands during drying, penetrates the coating layer, and forms air bubble marks without the coating layer. In particular, when the amount of entrained air is large, the coating layer is distributed in a sea-island shape on the surface of the support. Such unevenness in the distribution of the applied amount of the ink receiving layer causes unevenness or lack of image density, and it is not possible to obtain an ink jet recording sheet of satisfactory quality.

If a phenomenon occurs in which the coating liquid for the ink receiving layer does not wet the support and repels, the coating layer cannot be formed at all, and an ink jet recording sheet cannot be obtained.

In the present invention, as a result of intensive studies for the purpose of avoiding such coating failure, it was found that the viscosity and surface tension of the coating liquid for the ink receiving layer are closely related to the occurrence of such coating defects. did.

That is, the viscosity of the ink receiving layer coating liquid is 40 c
When the pressure is less than ps, the viscous force is insufficient when the curtain film is stretched during coating, and the flow is disturbed in a region where the curtain film is transferred to the base paper to form a coating layer. Cannot be formed. If the viscosity of the ink receiving layer coating liquid exceeds 2000 cps, the viscous force becomes excessive, and the falling point of the curtain film moves downstream with respect to the traveling direction of the support. It was found that the distribution was uneven.

Further, the surface tension of the ink receiving layer coating liquid is 2
When it is less than 3 dyne / cm, no coating failure such as uneven coating occurs, but after the coating, water or binder constituting the continuous phase in the coating liquid for the ink receiving layer invades the support unnecessarily, and The ratio of the binder in the receiving layer becomes low, the ink absorption excessively progresses, the density of the image becomes low, the sharpness of the color tone is lowered, and the binder permeated into the support is transferred into the support. Inhibiting the absorption of the ink, it was found that the ink easily penetrated in the plane direction in the ink receiving layer, and the sharpness of the image was reduced.
Furthermore, it was found that when the surface tension of the ink coating liquid exceeded 55 dyne / cm, the coating liquid for the ink receiving layer did not wet the support during coating, and a coating layer could not be formed.

Therefore, the viscosity of the ink receiving layer coating liquid is set to 4
By adjusting the surface tension of the coating solution to a range of 23 to 55 dyne / cm in a range of 0 to 2000 cps and avoiding both phenomena of air entrainment and a phenomenon in which the coating solution repels the support without getting wet. Thus, an ink jet recording sheet having a coating layer having a uniform coating amount distribution can be obtained.

Here, the viscosity value depends on the temperature of the coating solution, and it is difficult for the coating apparatus to maintain the same temperature throughout the year. The liquid was sampled, and the value measured with a B-type viscometer immediately after the sampling was taken as the viscosity value in the present invention.

In order to adjust the viscosity of the coating solution to the range in the present invention, a water-soluble polymer such as polyvinyl alcohol, starch, carboxymethyl cellulose or a thickener such as an acrylic emulsion is mixed with the coating solution to increase the viscosity. Means to increase the solids concentration of the coating solution, reduce the distance between the dispersed substances to increase the mutual force, increase the probability of collision,
Means can be taken to increase the viscosity, or conversely, dilute the coating solution to lower the viscosity.

Since the surface tension value also depends on the temperature of the coating liquid, as in the case of the viscosity, the coating liquid is formed immediately before coating by forming a curtain. The value measured by the method was defined as the surface tension value in the present invention.

In order to adjust the surface tension of the coating solution to the range in the present invention, anionic surfactants such as carboxylate, sulfonate, sulfate and phosphate, ether type, ether ester type , Ester type,
An arbitrary amount of a nonionic surfactant such as a nitrogen-containing surfactant and an amphoteric surfactant such as betaine, an aminocarboxylate and an imidazoline derivative can be mixed in the coating solution.

As a characteristic of the curtain coating method, as can be seen from FIG. 1, the place where the coating liquid flows with the flow path regulated is as follows.
That is, only the slit 2 portion. The selection range of the width of this slit is wide, but usually it is 0.2 mm to
It is between 1 mm. In curtain coating, the coating liquid flowing out of the lip 3 forms a free surface until it comes into contact with the web 5, so that the flow path is not restricted. In contrast, in the rod or blade coating method, the minimum gap between the rod or blade and the web where the liquid is measured is usually 0.05 g.
mm or less. Therefore, when the cause of streaks or scratches is aggregates or foreign matter, the probability of appearing as streaks or scratches is lower in the curtain coating system than in the rod or blade coating system. Is extremely low,
It is possible to obtain an ink jet recording sheet in which unevenness in ink reception due to such unevenness in application is extremely small.

Furthermore, since the curtain coating method is a pre-metering type coating method, the amount of the coating liquid flowing out of the head is recovered and used. On the other hand, since the blade coating method, the rod coating method, and the air knife coating method are post-metering coating methods in which the coating liquid is once supplied to the web excessively and then scraped off and weighed, the amount of liquid recovered is More than curtain coating. In addition, in such a coating method, when an excessive coating liquid is supplied to the web, water and a binder in the liquid are selectively absorbed by the web, and the recovered liquid is increased in concentration to increase the concentration of the coating liquid, Foreign matter adhering to the base paper surface accompanies the recovered liquid and causes a streak. In the curtain coating method, stable coating can be performed without a change in the concentration of the coating liquid even during a long operation.

Since the ink receiving layer in the present invention needs to have a function of fixing the solvent of the water-soluble ink,
It is preferable to contain a water-soluble binder in terms of affinity with the solvent of the water-soluble ink. Examples of the water-soluble binder that can be used in the present invention include polyvinyl alcohol, vinyl acetate, oxidized starch, and esterified starch. , Etherified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, casein, gelatin, soybean protein and the like.

In the present invention, other binders that can be used in the ink-receiving layer include conjugated diene copolymer latexes such as maleic anhydride resin, styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer. An acrylic polymer latex such as a polymer or a copolymer of an acrylate ester and a methacrylate ester; a vinyl polymer latex such as an ethylene-vinyl acetate copolymer; or a functional group such as a carboxyl group of these various polymers. Functional group-modified polymer latex by contained monomer; water-based adhesive such as thermosetting synthetic resin such as melamine resin and urea resin; polymethyl methacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride
Synthetic resin adhesives such as vinyl acetate copolymer, polyvinyl butyral, and alkyd resin can be used.

In the present invention, the cationic dye fixing agent is used for the purpose of increasing the strength of the ink receiving layer containing the water-soluble binder at the time of receiving the water-soluble ink, that is, the water resistance, and promoting the fixing property of the ink. Preferably, it is used. The cationic dye fixing agent in the present invention uses at least one or more of monomers, oligomers and polymers of primary to tertiary amines or quaternary ammonium salts which dissociate when dissolved in water to exhibit cationicity. , Preferably an oligomer or a polymer.

In the present invention, one or more known white pigments can be used in the ink receiving layer. For example,
Light calcium carbonate, heavy calcium carbonate, kaolin,
Talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white,
Aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica,
White inorganic pigments such as colloidal alumina, pseudoboehmite, aluminum hydroxide, alumina, lithopone, zeolite, hydrohaloysite, magnesium carbonate, magnesium hydroxide, styrene plastic pigment, acrylic plastic pigment, polyethylene, microcapsules, urea resin, melamine Organic pigments such as resins are exemplified. Among the above, a porous inorganic pigment is preferable as the white pigment contained as a main component in the ink receiving layer,
Examples include porous synthetic amorphous silica, porous magnesium carbonate, and porous alumina, and porous synthetic amorphous silica having a large pore volume is particularly preferable.

In the present invention, the support to be used may be paper, a thermoplastic resin film, synthetic paper, a synthetic resin laminated paper such as a photographic support, a sheet such as a nonwoven fabric mainly composed of wood fibers or synthetic fibers. Substances. In the case of paper, addition or non-addition of an internal sizing agent, neutral sizing agent, polymer sizing agent, sizing agent such as acidic sizing agent alone or in combination, filler may or may not be included,
There is no restriction on the presence or absence of a size press. As the internal filler of the paper support, a conventionally known pigment is used as a white pigment, and can be used alone or in combination.Examples include light calcium carbonate, heavy calcium carbonate, kaolin, clay, talc,
Calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic silica, aluminum hydroxide, alumina, lithopone, zeolite, magnesium carbonate, water Examples include white inorganic pigments such as magnesium oxide, styrene plastic pigments, acrylic plastic pigments, organic pigments such as polyethylene, microcapsules, urea resins, and melamine resins. Furthermore, if the support is paper, it contains neutral sizing and filler and the ratio of wood pulp / filler is 90-70% by weight / 10-30% by weight.
It is preferable that the basis weight is 60 to 120 g / m ² , but there is no limitation.

In the present invention, as other additives,
Pigment dispersants, thickeners, flow improvers, defoamers, foam inhibitors,
Release agents, foaming agents, penetrants, coloring dyes, coloring pigments, optical brighteners, ultraviolet absorbers, antioxidants, preservatives, anti-binders,
A water-proofing agent, a wet paper strength enhancer, a dry paper strength enhancer, and the like can be appropriately blended.

The ink used in the present invention includes the following colorants:
This is a recording liquid composed of a liquid medium and other additives. Examples of the coloring agent include a direct dye, an acid dye, a basic dye, a reactive dye, and a water-soluble dye such as a food colorant.

As the solvent for the aqueous ink, water and various water-soluble organic solvents such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, Alkyl alcohols having 1 to 4 carbon atoms such as isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyethylene glycol and polypropylene glycol Polyalkylene glycols such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, Alkylene glycols having 2 to 6 alkylene groups such as lene glycol and diethylene glycol; lower alkyl ethers of polyhydric alcohols such as glycerin, ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether and triethylene glycol monomethyl ether; No. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether are preferable. Other additives include, for example, P
Examples include H regulators, sequestering agents, fungicides, viscosity modifiers, wetting agents, surfactants, and rust inhibitors.

[0036]

[0037]

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an embodiment of the present invention, and is a schematic view of a coating apparatus for coating an ink receiving layer. The ink receiving layer coating liquid prepared in advance is sent from the coating liquid storage tank 11 to the coater head 1 by the liquid supply pump 12.

The inside of the coater head 1 comprises a manifold 6 and a slit 2, each of which is finished with high precision. The supplied coating liquid is filled in the manifold 6, and the influence of the dynamic pressure due to the liquid supply of the pump 12 is reduced in the narrow gap that passes when the liquid is supplied to the slit 2, and the pressure distribution in the width direction is made uniform. , Lip 3
More outflow and vertical curtain film 4 is formed.

The vertical curtain film 4 having a uniform profile in the width direction comes into contact with the continuously running web 5,
It is applied to the web 5. Here, the edge guides 10a, 1
Ob is provided not exceeding the width of the coater head 1 and further exceeding the width of the web 5, and the vertical curtain film is formed exceeding the width of the web 5. The vertical curtain film 4 is formed so as to exceed the width of the web 5 in order to prevent a thick coating of the coating layer at both ends of the vertical curtain film 4. Web 5
The coating liquid flowing down beyond the width is collected in the liquid receiving tank 9, returned to the coating liquid storage tank 11, and then applied again. Also,
Even when the application is interrupted, for example, when the web 5 is cut, the coating liquid is collected in the liquid receiving tank 9.

The contact portion between the continuously running web 5 and the vertical curtain film 4 (hereinafter referred to as "coating portion") shields the air flow accompanying the web 5 and circulates air around the curtain. The web 5 without disturbing the vertical curtain film 4
A wind shield plate 8 is provided so as to reach. The transport direction of the web 5 is changed by a roll 7 immediately before the application section, so that the influence of air accompanying the web 5 on the application section is minimized.

In order to apply the formed vertical curtain film 4 in a stable state, the coater head 1 is removed from the web 5.
Although a certain height is required to the lower outflow portion, in the present embodiment, the height can be controlled, and the height suitable for stabilizing the vertical curtain film 4 is 60 to 30.
0 mm, preferably 100 to 250 mm, more preferably 120 to 180 mm.

It is needless to say that the present invention is not limited to the above embodiments, but can be variously modified. In the above-described embodiment, the width of the formed curtain film is larger than the width of the web 5. This is to prevent an increase in the coating amount at both ends of the coating layer. If the size is small or not so much of a problem, or if the problem can be solved by adopting the method disclosed in Japanese Patent Publication No. 49-14130 and other methods for preventing an increase in the coating amount, the vertical curtain film is used as a web. It can be equal to the width of 5, or slightly smaller.

[0044]

[Action] The viscosity of the ink receiving layer coating liquid is 40 to 2000 cp.
s, adjusting the surface tension of the coating liquid to a range of 23 to 55 dyne / cm, and setting the coater head to the manifold and the slit.
Is applied to the support by using an extrusion type curtain coating apparatus made of the above, there is no occurrence of coating defects, and the coating amount distribution of the ink receiving layer becomes uniform. Since the pressure applied to the coating liquid during coating is low and the coating liquid is not supplied to the support excessively, the selective absorption of the binder contained in the ink receiving layer coating liquid to the support can be achieved. Does not happen.

[0045]

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

The ink jet recording suitability was measured by the following method. 1) Print Density The print density was measured by using a sharp (IO-720) inkjet printer to measure the optical density of a recorded image printed in a single color of black, yellow, magenta, and cyan. The numerical values indicate that the higher the density, the higher the density.
For example, if it is black, 1.30 or more indicates that it is sufficiently good.

2) Print-through Print-through is performed by using a (IO-720) inkjet printer manufactured by Sharp Corporation to print solid blue prints (cyan + magenta) and print the optical density of magenta from the back side of the recorded image. It was measured. If the optical density is 0.25 or less, there is no particular problem in practical use.

3) Image Density Unevenness The image density unevenness was measured by using a Sharp (IO-720) ink jet printer so that the area ratio of print dots was 5%.
0%, a printed portion (50 mm × 5) in which a single color of each of black, yellow, magenta, and cyan is printed.
0 mm) was binarized into a grayscale image by an image analyzer, and the area distribution of print dots was measured. As the evaluation value, the average value of the variation coefficient value of each color was adopted.

4) Coating Defects Coating defects were detected by an optical defect detector installed in the coating device, and the defect length was defined as the defect length relative to the coating length. The coating defects that can be detected by the defect detection device are defects having uncoated portions such as streaks and scratches and excessive coating portions such as dirt.
If the length is not less than m and the length is not less than 2.0 mm, detection is possible. The length of the defect is a length obtained by adding 1 m before and after the defect in consideration of the margin when deleting the defect, for example, even if the actual length of the defect is 0.1 m, The length is 2.1 m.

Example 1 100 parts of synthetic amorphous silica (Fine Seal X-37B; manufactured by Tokuyama Soda Co., Ltd.) was used on the surface of high quality paper having a basis weight of 80 g / m ² as a base paper.
Polyvinyl alcohol solid content 10% (PVA117, manufactured by Kuraray Co., Ltd.) 600 parts, cationic dye fixing agent solid content 3
A coating solution (viscosity 43 cps, surface tension 52 dyne / cm, solid content 10%) containing 67% of 0% (Sumilace Resin 1001; manufactured by Sumitomo Chemical Co., Ltd.) and 0.7 part of acetylene glycol is applied. So that the amount is 6 g / m ² ,
The ink receiving layer was applied using a curtain coating apparatus, and was subjected to a super calender finish, thereby producing an ink jet recording sheet.

Example 2 The same as Example 1 except that the amount of acetylene glycol added to the ink receiving layer coating liquid used in Example 1 was changed to 1.5 parts and the viscosity was 43 cps and the surface tension was 30 dyne / cm. Under the conditions, an ink jet recording sheet was produced.

Example 3 A viscosity of 42 cps and a surface tension of 25 were used instead of 2.2 parts of acetylene glycol in the coating solution used in Example 1.
An ink jet recording sheet was produced under the same conditions as in Example 1 except that dyne / cm was used.

Example 4 The solid content of the ink receiving layer coating solution used in Example 1 was 16
%, Viscosity 540 cps, surface tension 51 dyne / c
An ink jet recording sheet was produced under the same conditions as in Example 1 except that m was used.

Example 5 The viscosity of 420 cps was changed by changing the amount of acetylene glycol added to the ink receiving layer coating solution used in Example 4 to 1.5 parts.
An ink jet recording sheet was produced under the same conditions as in Example 4 except that the surface tension was 35 dyne / cm.

Example 6 The viscosity of 400 cps was changed by changing the addition amount of acetylene glycol in the ink receiving layer coating solution used in Example 4 to 2.2 parts.
An ink jet recording sheet was produced under the same conditions as in Example 4 except that the surface tension was 27 dyne / cm.

Example 7 The solid concentration of the ink receiving layer coating solution used in Example 1 was 19
%, Viscosity 1940 cps, surface tension 50 dyne /
An ink jet recording sheet was produced under the same conditions as in Example 1 except that the thickness was set to cm.

Example 8 The viscosity of 1900 cp was changed by changing the addition amount of acetylene glycol in the ink receiving layer coating liquid used in Example 7 to 1.5 parts.
An ink jet recording sheet was produced under the same conditions as in Example 7 except that the s and the surface tension were 33 dyne / cm.

Example 9 The viscosity of 1830 cp was changed by changing the addition amount of acetylene glycol in the ink receiving layer coating liquid used in Example 7 to 2.2 parts.
An ink jet recording sheet was produced under the same conditions as in Example 7 except that the s and the surface tension were 26 dyne / cm.

Comparative Example 1 The solid concentration of the ink receiving layer coating solution used in Example 1 was 20
%, The amount of acetylene glycol added was changed to 1.5 parts, the viscosity was 2140 cps, and the surface tension was 35 dyne / c.
An ink jet recording sheet was produced under the same conditions as in Example 1 except that m was used.

Comparative Example 2 The solid content of the ink receiving layer coating solution used in Example 1 was 9%.
An attempt was made to produce an ink jet recording sheet under the same conditions as in Example 1 except that the amount of acetylene glycol added was changed to 1.5 parts, the viscosity was 36 cps, and the surface tension was 30 dyne / cm. It was too low, no coating layer was formed, and an ink jet recording sheet could not be obtained.

Comparative Example 3 The solid content of the ink receiving layer coating solution used in Example 1 was 16
%, The amount of acetylene glycol added was changed to 2.9 parts, the viscosity was 370 cps, and the surface tension was 21 dyne / cm.
An ink jet recording sheet was produced under the same conditions as in Example 1 except that the above conditions were satisfied.

Comparative Example 4 The solid content of the coating solution for the ink receiving layer used in Example 1 was 16
%, The amount of acetylene glycol added was changed to 0.4 part, the viscosity was 710 cps, and the surface tension was 58 dyne / cm.
An attempt was made to produce an ink jet recording sheet under the same conditions as in Example 1, except that the surface tension was too high, no coating layer was formed, and no ink jet recording sheet could be obtained.

Comparative Example 5 An ink jet recording sheet was produced under the same conditions as in Example 5 except that a blade coating device was used as the coating device.

Comparative Example 6 An ink jet recording sheet was produced under the same conditions as in Example 5 except that a rod coating device was used as the coating device.

Comparative Example 7 An air knife coating device was used as a coating device.
An ink jet recording sheet was produced under the same conditions as in Example 5.

Comparative Example 8 An ink jet recording sheet was produced under the same conditions as in Example 5 except that a reverse roll coating device was used as the coating device.

[0067]

[Table 1]

Table 1 shows the evaluation results. As shown in Examples 1 to 9, the viscosity of the ink receiving layer coating liquid was 40 to 2000 c.
ps, the surface tension of the coating solution is adjusted to a range of 23 to 55 dyne / cm, and coating is performed on the support by using a curtain coating device, whereby high print density, show-through, and uneven image density are observed. Thus, an ink jet recording sheet free from coating defects can be obtained.

In Comparative Example 1, the viscosity of the coating solution was too high, and the coating layer became uneven. In Comparative Example 2, the viscosity of the coating solution was too low, and the coating line portion was not stable, and the coating was not performed. Could not do. In Comparative Example 3, since the surface tension of the coating liquid was too low and the absorptivity of the ink receiving layer was too high, the print density was slightly low, and show-through was observed. In Comparative Example 4, the surface tension of the coating liquid was too high, so that the coating liquid did not wet and could not be applied. In Comparative Examples 5 to 8, when a coating device other than the curtain coating device was used, the occurrence of uneven image density and the occurrence of coating defects were conspicuous.

[0070]

According to the present invention, it is possible to obtain an ink jet recording sheet having no coating defects, high print density, uniform image density and no show-through.

[Brief description of the drawings]

FIG. 1 is a schematic view of a curtain coating apparatus showing one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coater head 2 Slit 3 Lip 4 Curtain film 5 Web 6 Manifold 7 Roll 8 Wind shield 9 Liquid receiving tank 10a, 10b Edge guide 11 Storage tank 12 Liquid supply pump

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-65742 (JP, A) JP-A-57-39985 (JP, A) JP-A-58-3672 (JP, A) JP-A-55-657 73365 (JP, A) JP-A-53-115754 (JP, A) JP-A-61-16883 (JP, A) JP-A-4-70389 (JP, A) JP-A-4-327296 (JP, A) JP-B-49-35447 (JP, B1) JP-B-53-31005 (JP, B1)

Claims (2)

(57) [Claims] 1. An ink jet recording sheet comprising at least one ink receiving layer provided on both sides or one side of a support, wherein the viscosity of the ink receiving layer coating liquid is 40 to 20.
00 cps, the surface tension of the coating solution is 23 to 55 dyne /
cm, and the coating solution is coated on the support by a vertical curtain using an extrusion-type curtain coating apparatus comprising a slit having a narrow gap between a coater head and a manifold.
A coating having a film height of 100 to 250 mm , wherein the coating liquid is a group consisting of synthetic amorphous silica and pseudo-boehmite.
At least one white pigment selected from
An ink jet recording sheet comprising a water-soluble binder comprising coal . 2. A method for producing an ink jet recording sheet comprising at least one ink receiving layer provided on both sides or one side of a support, wherein the viscosity of the coating liquid for the ink receiving layer is 40 to 2000 cps. Surface tension 23-55
dyne / cm, the coating liquid was coated on the support using an extrusion-type curtain coating apparatus comprising a slit having a narrow gap between a coater head and a manifold .
The vertical curtain film is applied at a height of 100 to 250 mm, and the coating solution is composed of synthetic amorphous silica and pseudo-boehmite.
At least one white pigment selected from the group consisting of
And a water-soluble binder comprising alcohol .