JP2003293292A - Method for producing sheet having fine pore-containing coating layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet which is obtained by coating a water-based coating having excellent homogeneity and containing stably presentable cells and then drying the coating and having an excellent heat-insulating property and an excellent masking property. <P>SOLUTION: This method for producing the sheet having a fine pore- containing coating layer is characterized by stirring an aqueous medium containing a coating film-forming polymer, simultaneously adding a hydrophobia pigment to the aqueous medium to prepare the water-based coating containing cells therein, coating the water-based coating on a support, and then drying the coated coating. It is desirable that the water-based coating is treated with a liquid-defoaming device before coated. The coating sheet has pores surrounded with a hydrophobic pigment in the coating layer. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a sheet having a coating layer containing fine voids.

[0002]

2. Description of the Related Art It is known that a coating layer containing fine voids is obtained by applying a coating material obtained by foaming a liquid containing a resin component by stirring and drying the coating material (Japanese Patent Laid-Open No. 1-275184).
No. 2, JP-A-2-131985, JP-A-2-17528
3 gazette). However, since this method foams by mechanical force, the size of the formed bubbles tends to be non-uniform, and since the stability of the bubbles is increased, only a highly viscous paint can be prepared, There is a problem that the coating method is limited.

Further, as a coating layer containing other microscopic voids, a coating material containing particles having a hollow structure is applied,
A method of obtaining by drying is known (JP-A-59-50).
No. 93). However, the production of particles with a hollow structure
It is very complicated, the hollow particles are very expensive, and it is difficult to reduce the cost of the sheet having the coating layer containing microvoids.

Another method for producing a coating layer containing minute voids is to apply a coating material containing a foaming polyurethane-based adhesive that applies the foamability and adhesiveness of polyurethane, and after drying, foam by a chemical reaction. Occurs, and there is a coating layer in which voids are formed (JP-A-2-2699091). However, since this paint uses foaming after drying, the surface roughness of the coating layer due to foaming is remarkable, and a smooth coating layer cannot be obtained.

Japanese Unexamined Patent Publication (Kokai) No. 5-32052 proposes a paint containing an organic and / or inorganic pigment and a film-forming resin as main components, which is foamed by stirring. This coating material can form a coating layer having a continuous pore structure formed as a gas escape passage due to the expansion of the gas in the pores in the drying step. Also in such a manufacturing method, there are problems that the stability of the bubbles formed in the paint is poor and that the sizes of the obtained bubbles are likely to be non-uniform.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a void-containing coating excellent in heat insulation and concealment obtained by applying and drying a water-based coating material containing air bubbles which has excellent uniformity and can exist stably. To provide a sheet having layers.

[0007]

Means for Solving the Problems A sheet having a coating layer containing microvoids of the present invention has a structure in which a hydrophobic pigment is added to an aqueous medium containing a film-forming polymer while stirring to form bubbles inside. It can be obtained by preparing a water-based coating material to be contained, coating the water-based coating material on a support, and drying.

The water-based paint is preferably treated with a liquid defoaming device prior to application.

The water-based paint preferably contains air bubbles surrounded by the hydrophobic pigment.

The hydrophobic pigment preferably has an M value of 10 to 80 and an average primary particle diameter of 0.01 to 5 μm.
Is preferred.

The mass ratio of the hydrophobic pigment to the film-forming polymer (hydrophobic pigment: film-forming polymer) is 5: 9.
It is preferably 5 to 70:30.

The void is surrounded by a hydrophobic pigment. The void size has an average diameter of 0.5 μm to 1000 μm.
It is preferably m.

The M value referred to in the present specification means that about 5 ml of a mixture of water and methanol at 5 to 30 ° C. is sampled in a 10 ml test tube, and 1 to 2 of the mixture is mixed with a microspatel.
After inserting a pigment amount of about a cup and shaking the pigment twice, when the pigment begins to settle, the volume of methanol in the mixture is increased.
It is a value measured as%.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The water-based paint used in the present invention is
While stirring the aqueous medium containing the film-forming polymer,
A hydrophobic pigment is added to this to contain bubbles inside.

The hydrophobic pigment used in the present invention includes
As long as it has hydrophobicity, pigments which are made hydrophobic by surface-treating an inorganic pigment with an organic compound, a silane compound, a fluorine compound, or the like, and hydrophobic plastic pigments can be given.

Such a hydrophobic pigment is a particle which does not have a hollow structure by itself, but it is mixed with stirring in an aqueous medium containing a film-forming polymer so as to surround fine bubbles. It becomes densely present in. That is, the pigments aggregate to form minute hollow portions in the coating material.

The term "hydrophobicity" as used in the present invention means that the M value represented by the volume percentage of methanol which begins to wet when the content of methanol is increased in a mixed solution of water and methanol is 10 to 80. Say the degree. If the hydrophobic treatment is insufficient, the M value may not be 10 or more, and the hydrophobic pigment according to the present invention may not be obtained.

The M value is 5 to 30 ° C. in a 10 ml test tube.
About 5 ml of a mixture of water and methanol was sampled, and 1 to 2 cups of a pigment was added to the mixture with a microspatel, and the mixture was shaken twice. It is measured as the vol% of methanol in the mixture.

Examples of the inorganic pigment used as the hydrophobic pigment include silica, titanium oxide, zinc oxide, aluminum hydroxide, barium sulfate, calcium carbonate, talc, kaolin, calcined kaolin, clay, calcined clay and sericite. . As a method of rendering these inorganic pigments hydrophobic, there are a method of coating with a hydrophobic substance, a method of treating with a coupling agent or the like to modify the surface with a hydrophobic group, and the like. Examples of such a hydrophobic substance or coupling agent (hereinafter, both are collectively referred to as "surface treatment agent") include dimethyl silicone oil, cyclic silicone oil, methylphenyl silicone oil, silicone polyether copolymer, and alkoxy-modified silicone. Silicone-based polymers such as; fluoro-based compounds such as perfluoroalkyl phosphates; hydrocarbon-based polymers such as polyethylene; silicon-containing compounds such as methyl hydrogen siloxane, trimethylsiloxy silicic acid, halogenated silanes, etc. .

Examples of the plastic pigment used for the hydrophobic pigment include polystyrene particles, nylon powder, polyethylene powder, silicone resin filler, and urea formalin resin filler whose surface is made hydrophobic by a polymerization method or the like.

The average primary particle diameter of the hydrophobic pigment used in the present invention is preferably 0.01 μm or more, more preferably 0.02 μm or more. This is because a pigment having an average primary particle size smaller than 0.01 μm is difficult to handle. On the other hand, the upper limit of the average primary particle diameter is preferably 5 μm or less, more preferably 2 μm or less. This is because a pigment having an average primary particle diameter of more than 5 μm lowers the stabilizing effect of bubbles, and it may be difficult to form stable voids in the coating layer.

As the aqueous medium used in the water-based paint of the present invention, a mixture of water and a film-forming polymer is used.

Examples of the film-forming polymer include polyvinyl alcohol, sodium polyacrylate, carboxymethylcellulose, polyvinylpyrrolidone, casein, water-soluble resins such as alkali salts of styrene-maleic acid copolymers, polyacrylates, polyesters, styrene-butadiene-based copolymers. A water-dispersible resin such as a polymer, a polyurethane resin, a vinyl chloride / vinyl acetate copolymer, or an ethylene vinyl acetate copolymer can be used. These may be used alone or in combination of two or more kinds. Good.

The mixing ratio (mass ratio) of water to the coating film forming polymer is 85:15 to 4 as water: coating film forming polymer.
It is preferably 0:60. Within these ranges, it is appropriately selected depending on the viscosity of the coating material, the surface tension of the resulting aqueous medium, and the like. In addition, the mass ratio of the hydrophobic pigment and the coating film forming polymer (hydrophobic pigment / coating film forming polymer)
Is preferably 5/95 to 70/30, and 10/90 to 7
0/30 is more preferable. If it is less than 5/95, it is difficult to form stable bubbles in the paint, and if it exceeds 70/30, the resulting water-based paint exhibits thixotropic properties, which makes it difficult to handle the water-based paint.

The content of bubbles contained in the water-based paint of the present invention can be adjusted according to the content of the hydrophobic pigment in the paint, the kind of the hydrophobic pigment used, the combination of the hydrophobic pigment and the aqueous medium, and the like.

In the water-based paint of the present invention, the bubbles surrounded by the hydrophobic pigment are stably present, and the formed bubbles are smaller than the variation in the size of the bubbles formed by mechanical stirring or the like. Existence is stable. still,
The bubbles contained in the paint may be surrounded not only by the hydrophobic pigment alone but also by the hydrophobic pigment and the film-forming polymer.

The mechanism by which bubbles can be stably present in the water-based paint is not clear, but it is considered to be related to the affinity between the hydrophobic pigment and the aqueous medium. That is, it is considered that the hydrophobic pigment and the aqueous medium are achieved by having an appropriate affinity that is not too high and not too low. If the affinity of both is too high, the pigment will be stably dispersed at the particle level in the aqueous medium, and if the affinity of both is too low, the pigment and the aqueous medium will be completely separated. Because.

Therefore, the combination of the hydrophobic pigment and the film-forming polymer is a combination in which the hydrophobic pigment can be present so as to surround air having a small size, in other words, bubbles can be stably present in the water-based paint. It is preferable to select a combination. Further, since the bubble size contained in the paint depends on the combination of the hydrophobic pigment and the film-forming polymer, depending on the size and amount of the bubbles contained in the water-based paint, the type, amount, and particle size of the hydrophobic pigment The diameter, the type and amount of the film-forming polymer, and the combination thereof may be selected.

Here, the surface tension of the aqueous medium is changed depending on the kind of the film-forming polymer used for the aqueous medium or the hydrophobic pigment to be combined, even when the desired air bubbles cannot be contained. By appropriately adding a surface tension adjusting agent capable of forming the bubbles, it becomes possible to form bubbles and allow them to exist stably.

Examples of the surface tension adjusting agent include surfactants; lower alcohols such as methanol and ethanol; lower ketones such as acetone. As a surfactant,
For example, known surfactants such as those described in "Introduction to New Surfactants" (published by Takehiko Fujimoto, Sanyo Kasei Kogyo) can be used. Specifically, anionic surfactants such as aromatic or aliphatic carboxylic acid salts, sulfuric acid ester salts, sulfonic acid salts, and phosphoric acid ester salts; aromatic or aliphatic primary amine salts, secondary acids Cationic surfactants such as amine salts, tertiary amine salts and quaternary ammonium salts; amphoteric surfactants such as aromatic or aliphatic amino acid type and betaine type; polyoxyethylene glycol type nonionic surfactants A polyhydric alcohol type nonionic surfactant; acetylene glycol, an ethylene oxide adduct of acetylene glycol, acetylene alcohol, an ethylene oxide adduct of acetylene alcohol, and the like. These surface tension adjusting agents may be used alone or in combination of two or more as needed.

In the water-based paint of the present invention, hydrophobic pigments of different M values are used as long as the balance between the hydrophobic pigment and the aqueous medium is not impaired, that is, the formation of bubbles by the hydrophobic pigment is not impaired. , Hydrophilic pigments, wetting agents, antifoaming agents and the like may be added. Here, calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, amorphous silica, aluminum hydroxide, barium sulfate, talc, kaolin, clay, calcined clay, etc. are hydrophilic unless surface treatment is performed to make them hydrophobic. It is a hydrophilic pigment, and some of the plastic pigments such as styrene microballs, nylon powder, polyethylene powder and urea / formalin resin filler are hydrophilic.

The water-based paint of the present invention is produced by mixing an aqueous medium as an essential component and a hydrophobic pigment, and further, if necessary, a surface tension adjusting agent and an appropriate additive. Also, regarding the film-forming polymer contained in the aqueous medium, it is sufficient that a predetermined amount of the film-forming polymer is contained in the state of the finally prepared coating material, and the film-forming polymer having a predetermined concentration is contained in advance. In addition to being mixed as an aqueous medium, an aqueous medium containing a part of the film-forming polymer may be first prepared, and the film-forming polymer may be added at an appropriate stage so as to contain the film-forming polymer at a required concentration. Specifically, a method of dispersing a hydrophobic pigment while stirring an aqueous medium containing a film-forming polymer at a predetermined concentration, and a hydrophobic pigment while stirring an aqueous medium containing a part of the film-forming polymer. After dispersing, the coating film forming polymer is added to a required concentration. In the case of containing a surface tension adjusting agent, an aqueous medium containing a predetermined concentration of the film-forming polymer or an aqueous medium containing a part of the film-forming polymer is allowed to contain a surface tension adjusting agent in advance. The hydrophobic pigment may be dispersed in the medium while stirring, or the surface tension adjusting agent may be added after dispersing the hydrophobic pigment in an aqueous medium containing a predetermined concentration of the film-forming polymer. Then, after dispersing the hydrophobic pigment in the aqueous medium containing a part of the film-forming polymer, the surface tension adjusting agent is added, and the film-forming polymer is further added to contain the film-forming polymer at a predetermined concentration. The water-based paint may be prepared. Moreover, when an additive is contained, the additive can be added at an appropriate stage.

The water-based paint of the present invention thus prepared has air bubbles in a stable manner. The size of bubbles in the coating material is appropriately determined according to the size and amount of the hydrophobic pigment contained, the degree of hydrophobicity of the hydrophobic pigment, and the relationship with the aqueous medium. Generally, bubbles having an average diameter of about 0.5 μm to 1000 μm are formed. The bubbles formed here are more stable than those obtained by the conventional stirring method or the like, and moreover, the variation in size is small.

Further, the prepared water-based paint is preferably treated with a liquid defoaming device in order to remove bubbles other than the bubbles of the present invention. By this treatment, it is possible to obtain a stable water-based coating material containing a large number of bubbles with a small variation in size. Examples of the defoaming mechanism include a mechanism utilizing centrifugal force, a mechanism utilizing temperature change such as heating, a mechanism utilizing pressure change and the like, which are appropriately selected and used.

The method for applying the water-based paint of the present invention is not particularly limited. The coating can be carried out using a coating method which has been conventionally used, that is, a coating machine such as a blade coater, an air knife coater, a bar coater, a rod blade coater, a curtain coater or a slot die coater.

There is no particular limitation on the material, shape, size, etc. of the support, and for example, high quality paper (acidic paper, neutral paper), medium quality paper, coated paper, art paper, cast coated paper, glassine In addition to paper, resin-laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, non-woven fabric, synthetic resin film and the like, various transparent supports and the like can be appropriately selected and used.

The coating amount is 1 dry weight on the support.
~ 20 g / m ² is preferred, more preferably 3-15 g
/ M ² . If it is less than 1 g / m ² , a uniform coating surface cannot be obtained, and the thickness of the coating layer to be formed becomes thin, so that the desired heat insulating effect and concealing property due to the voids cannot be obtained. On the other hand, if the amount exceeds 20 g / m ² , a large amount of energy is required for the drying step and the productivity is lowered, but the heat insulating effect and the concealing effect of the obtained coating layer are saturated, which is not economical.

The coating layer formed by coating and drying as described above has voids corresponding to the bubbles contained in the coating material of the present invention. That is, in the coating layer to be formed, voids exist in the coating film-forming polymer, and the periphery of the voids is surrounded by the hydrophobic pigment. In this way, the coated sheet of the present invention can be produced.

The voids contained in the coating layer of the coating sheet of the present invention substantially correspond to the diameter of the bubbles contained in the water-based paint, and specifically, the average diameter thereof is 0.5 μm to 1000 μm.
Is about 0.5 μm to 200 μm, and more preferably about 0.5 μm to 100 μm. 0.
If it is less than 5 μm, the effects of heat insulation, cushioning property, anti-slip property, opacity, etc., which are exhibited by having voids, are reduced, which is not preferable. On the other hand, when it is larger than 1000 μm, bubbles are easily floated and separated in the water-based paint, and it becomes difficult to obtain a uniform paint, and large bubbles may affect the smoothness of the coated surface. In addition,
The void size is a value obtained by measuring an electron micrograph with an image analyzer.

The content of voids in the coating layer according to the present invention corresponds to the content of bubbles in the water-based paint, and is specifically 25 to 95% by volume. Here, the porosity (%) in the coating layer is represented by the following formula. Porosity = (area of coating layer−area of solid component) / area of coating layer × 100 The difference between the area of coating layer and the area of solid component is the coating layer area from the cross-sectional photograph of the obtained coating layer. , Measure the area of solid components,
It can be obtained as the difference between them.

In the coating layer obtained by applying the coating material of the present invention, a large number of voids (closed cells) having a small size variation are dispersed based on the bubbles contained in the coating material.
The hydrophobic pigment is present around the void so as to surround the void. The coating layer having such voids has excellent concealing properties and thermal insulation properties, and the coated surface has smoothness similar to that of a coating type having no voids. Therefore, the coating layer obtained by applying the coating composition of the present invention, as a coating film when the hiding property is required, as the receiving layer of the thermal transfer paper,
Alternatively, it is formed on the support as a heat-insulating layer formed between the support and the heat-sensitive color-developing layer so as to improve the sensitivity of the heat-sensitive color-developing layer, or as a smoothing layer when the surface is smoothed. be able to.

[0042]

The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the invention.

[Preparation of Waterborne Paint and Production of Coating Layer] Paint No. 1 Acrylic emulsion containing acrylic resin as film forming polymer (trade name: NFA-830, solid content concentration 40
%, Manufactured by Teikoku Kagaku Co., Ltd.) and 377 g of water were added to prepare an aqueous medium. While stirring this aqueous medium with a Cowles stirrer, hydrophobic silica (trade name: Nipseal SS-50F, M value 60, average primary particle diameter 0.02 μ)
m, manufactured by Nippon Silica Co., Ltd.). 100 g of the obtained dispersion liquid was collected, and a liquid defoaming device MS-SNB350
Defoaming treatment condition CH14 using N (Matsuo Sangyo Co., Ltd.)
A defoaming treatment was carried out in (Step 1: Revolution 7; no rotation for 6 minutes; Step 2: Revolution 9, rotation 7 for 3 minutes for 2 minutes) to prepare an aqueous paint. As a support, basis weight 50 g /
Using high-quality paper of m ² , one side of this support was coated with the previously prepared coating material so that the coating amount after drying was 10 g / m ^2, and then dried with hot air at 80 ° C. It was

Paint No. 2-6 An aqueous paint was prepared in the same manner as in Example 1 except that the type and amount of the coating film forming polymer and the type and amount of the pigment were changed as shown in Table 1. A coating layer was prepared in the same manner as in 1.

Paint No. 7 Paint No. Light calcium carbonate (trade name: Brilliant 15, M value 0, manufactured by Shiraishi Kogyo Co., Ltd., average primary particle diameter 0.2 μm) was used in place of the hydrophobic calcium carbonate 2 and the defoaming treatment was not applied. No. A water-based paint was prepared in the same manner as in 2, and a coating layer was formed using this. However, the coating amount was 40 g / m ² .

The amount of the coating film-forming polymer in Table 1 indicates the amount of solid content, and the amount of water indicates the total amount of water contained in the emulsion and added water. Also, Table 1
The following compounds were used as the compounds therein.

Acrylic: Acrylic emulsion "NFA-830" manufactured by Teikoku Kagaku KK, solid content concentration 40% SBR1: Styrene butadiene latex "Bonron S-1120" manufactured by Mitsui Chemicals, solid content concentration 45% Hydrophobic silica: Japan Silica “Nipseal SS-
50F ", average primary particle size 0.02 µm Hydrophobic calcium carbonate:" Calfine 100 "manufactured by Maruo Calcium Co., average primary particle size 0.15 µm Silica:" Mizukasil P527 "manufactured by Mizusawa Chemical Co., Ltd., average primary particle size 0 .02 μm polyethylene-treated silica: “P802” manufactured by Mizusawa Chemical Co., Ltd.
“Y”, silica treated with polyethylene, average primary particle size 0.02 μm Paraffin treated silica: “NP-8” manufactured by Mizusawa Chemical Co., Ltd.
And silica treated with paraffin and having an average primary particle diameter of 0.02 μm Light calcium carbonate: “Brilliant 1” manufactured by Shiraishi Industry Co., Ltd.
5 ", average primary particle size 0.2 μm

[Measurement and Evaluation Method] The coating material prepared above,
The following items were measured and evaluated about the obtained coating layer. The results are shown in Table 1.

(1) About 5 ml of a mixture of water and methanol at 5 to 30 ° C. was sampled in a test tube having an M value of 10 ml, and 1 to 2 cups of pigment was added to the mixture with a microspatel. After shaking twice, it was measured as the vol% of methanol in the mixture when the pigment started to settle.

(2) Surface tension (mN / m) The surface tension of an aqueous medium is measured by the Dunois surface tension meter (TOMB).
It was measured at 25 ° C. using O BORL).

(3) Average Primary Particle Diameter of Pigment The obtained coating layer was cut by freeze fracture, and the major axis and minor axis of the pigment were measured based on the electron micrograph of the cross section,
The average value was defined as the average primary particle diameter (μm) of the pigment.

(4) Bubbles in water-based paint The prepared paint was observed by an optical microscope, and when the bubbles could be confirmed, the mark was "◯", and when the bubbles could not be confirmed, the mark was "x".

(5) Void size in coating layer (μm), variation (μm), porosity (%) The coating layer was cut by freeze fracturing, and its cross section was observed with an electron microscope to find voids. In this case, the major axis and minor axis of each void were measured based on the electron micrograph, and the average value was taken as the void size (μm). The range (μm) from the maximum diameter to the minimum diameter of the observed average void diameter was determined, and this was taken as the variation of the void diameter. In the field of view of the micrograph, the sum of the areas of the voids was calculated, and the void ratio (%) was calculated by the following formula. Porosity = total void area / field-of-view area × 100 When a void is desired to be observed, it is indicated by “−”.

(6) Opacity The opacity was measured according to the method A of JIS P8138. That is, a coating layer was formed on a backing white plate, its reflectance (R _0.80 ) was measured, then a coating layer was formed on the backing black plate, and its reflectance (R ₀ ) was measured. The measurement was performed, and the opacity (C) was calculated by the following formula. C (%) = R ₀ / R _0.80 × 100 The larger the opacity (C%), the higher the hiding property.

[0055]

[Table 1]

From Table 1, the water-based paint of the present invention (No. 1) is prepared by mixing a hydrophobic pigment having an M value of 10 or more in an aqueous medium.
In each of 3 to 3), there were voids. Further, the coating layers obtained from these water-based paints all had voids.

On the other hand, no bubbles could be observed in the water-based paint (No. 4) using a pigment having no hydrophobicity. Also, there were no voids in the coating layer.
In addition, even with hydrophobically treated silica, no bubbles were formed in the paint when the pigment had an M value of less than 10 (Nos. 5 and 6).

Paint No. foamed by mechanical stirring 7
Then, even when the hydrophilic pigment was used, air bubbles were present, and voids were also present in the coating layer. However, the size of the voids in the coating layer varies, and the variation in the void size is large. Further, although some pigment was present around the voids, it was scattered to the same extent as the coating film portion other than the voids, and no denseness was observed around the voids.

No. 1 and No. Comparing Nos. 4, 5 and 6, no.
No. 1 had the largest hiding power.

[0060]

EFFECTS OF THE INVENTION The water-based coating composition of the present invention provides a coating layer which stably contains air bubbles of substantially uniform size and does not foam by mechanical stirring or heating, and which has voids corresponding thereto. You can Further, the water-based paint of the present invention can form bubbles due to the combination of the aqueous medium and the hydrophobic pigment, so that it is cheaper than the case of using hollow particles,
A paint containing bubbles can be provided.

Since the coating sheet of the present invention has a coating layer having a large number of fine voids with a small variation in size, a coating without voids containing the same amount of pigment is applied. Compared with the above-mentioned coating layer, it has excellent concealing properties, has a heat insulating effect, and has a smooth coated surface.

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Claims (7)

[Claims] 1. A hydrophobic pigment is added to an aqueous medium containing a film-forming polymer while stirring to prepare an aqueous paint containing bubbles therein, and the aqueous paint is applied onto a support, A method for producing a sheet having a coating layer containing microvoids, which comprises drying. 2. The method for producing a sheet having a coating layer containing microvoids according to claim 1, wherein the water-based coating material is treated with a liquid defoaming device prior to coating. 3. The method for producing a sheet having a microvoid-containing coating layer according to claim 1, wherein the water-based coating material contains air bubbles surrounded by the hydrophobic pigment. 4. The hydrophobic pigment has an M value of 10 to 80,
The average primary particle diameter is 0.01 to 5 μm.
A method for producing a sheet having the coating layer containing microvoids according to any one of 1. 5. The mass ratio of the hydrophobic pigment and the film-forming polymer (hydrophobic pigment: film-forming polymer) is 5:
It is 95-70: 30, The manufacturing method of the sheet | seat which has a micro void containing coating layer as described in any one of Claims 1-4. 6. The method for producing a sheet having a coating layer containing fine voids according to claim 1, wherein the voids are surrounded by a hydrophobic pigment. 7. The average size of the voids is 0.5 μm to 1
It is 000 micrometers, The manufacturing method of the sheet | seat which has a micro void containing coating layer as described in any one of Claims 1-6.