JP5515961B2 - Method for producing multilayer coating film and multilayer coating film - Google Patents

Description

  The present invention relates to a method for producing a multilayer coating film and a multilayer coating film obtained by the production method. More specifically, the present invention relates to a method for producing a multilayer coating film that is extremely excellent in adhesion between layers by applying a plurality of coating liquids at once, simply and with good productivity, and a multilayer coating film obtained by the method. .

For forming a multilayer coating film, a method using an “organic solvent-based” coating solution and a method using a “water-based” coating solution are known. From the viewpoint, it can be said that a method using a water-based coating solution or a so-called non-torque coating solution that does not use toluene, which is a harmful substance, is preferable.
As a method for forming a multilayer coating film, a tandem coating method in which a plurality of coating liquids are used to repeat coating and drying processes is known. In the tandem coating method, it is necessary to fix the lower layer before applying the upper layer coating solution so that the lower layer coating solution is not washed away by the upper layer coating solution. In particular, in the production of a multilayer coating film using an aqueous coating solution, a very large amount of time and energy is required for one drying process. Therefore, an extremely large amount of time and energy is required in a tandem coating method in which coating and drying processes are repeated. The tandem coating method is not suitable for the production of a multilayer coating film using an aqueous coating solution. Further, in the tandem coating method, since the coating and the drying process are repeated, air inevitably enters between the layers, so that the interlayer adhesion tends to be insufficient. Furthermore, since the probability of contamination is increased as the number of layers is increased, this leads to a decrease in yield.

On the other hand, as a method for solving the above problem, a multilayer coating method is known in which a multilayer is formed on a traveling substrate by a single coating process, and the multilayer coating method is a coating process for photographic films and the like. Widely used. In the multilayer coating method, for example, as shown in FIG. 1, coating liquids A and B are extruded from a plurality of narrow slits in the coating head 1, and naturally flow down on the inclined slide surface 2 by the action of gravity. The coating liquids A and B are transferred onto the traveling substrate 4 by a roll 3 to form a multilayer coating film.
As a method using an aqueous coating solution and employing such a multilayer coating method, a method of simultaneously coating a halogenated emulsifier using gelatin as a binder and then cooling (see Patent Document 1) It has been known. This method uses a gelatin sol-gel conversion property to gel the multilayer film to make it ultra-highly viscous, making it difficult to mix between layers and forming a coating film (coating film) by hot air drying etc. To do.

  Moreover, in the method using the organic solvent-based coating liquid, since the surface tension is lower than that of the aqueous system, diffusion mixing is likely to occur. Therefore, by adding a viscosity adjusting component such as a thickener, A method for controlling fluidity at the interface and the degree of mixing (see Patent Document 2) or at least one of two or more non-aqueous coating liquids contains an electron beam curable compound, and after simultaneous multilayer coating, an electron beam Has been proposed that cures or thickens the coating layer by irradiation and obtains a multilayer coating film by drying (see Patent Document 3).

JP 58-199074 A Japanese Examined Patent Publication No. 63-20584 JP-A-61-74675

Like the method described in Patent Document 1, a conventional method for producing a multilayer coating film using an aqueous coating liquid uses a large amount of a gelling agent typified by gelatin in order to ensure a laminated structure. . Therefore, for example, various functions such as hard coat properties and transparency cannot be imparted, and the resulting multilayer coating cannot be used because a component that is incompatible with or does not react with the gelling agent cannot be used. There is a problem that the use of the film is limited.
In addition, in the method using the organic solvent-based coating liquid described in Patent Document 2, a certain amount of thickener is necessary for viscosity adjustment, and these additives are generally low molecular weight organic materials and are used for multilayer coating. After the formation of the work and the laminate, the layers move between the layers, and the mechanical properties and the adhesion between the layers are assumed to be lowered. In the method using the organic solvent-based coating solution described in Patent Document 3, it is necessary to perform an electron beam irradiation step after the coating step before the coating solution is diffusely mixed, and the operation is complicated and large-scale. There is a problem that a complicated device is required.

  The present invention has been made under such circumstances, and is a multilayer coating system in which a multilayer is formed by a single coating process, and there is no need to use a gelling agent such as gelatin. A method for producing a multilayer coating film capable of imparting various functions such as transparency, and by applying a plurality of aqueous coating liquids at once, a multilayer coating film having extremely excellent interlayer adhesion can be easily and It is an object of the present invention to provide a method for producing with good productivity and a multilayer coating film obtained by the method.

  As a result of intensive research to solve the above-mentioned problems, the present inventor has specified between two types of aqueous coating liquids to be laminated in a multilayer coating method in which a multilayer is formed by a single coating process. By inserting this water-containing organic solvent as an intermediate layer, this intermediate layer suppresses the mixing of the two aqueous coating liquid layers and does not have a clear boundary surface, but the laminated structure of the two aqueous coating liquids It was found that (concentration gradient structure in the vicinity of the interface) was well formed. The present invention has been completed based on such findings.

That is, the present invention relates to the following [1] to [8].
[1] Two types of aqueous coatings to be laminated in a method for producing a multilayer coating film having a step of multilayering a plurality of aqueous coating solutions in advance and transferring the multilayered aqueous coating solution onto a substrate A method for producing a multilayer coating film, characterized in that a multilayer is formed by inserting the following water-containing organic solvent as an intermediate layer between liquids.
Hydrous organic solvent: A mixed liquid of a hydrophilic organic solvent and water, and the hydrophilic organic solvent is an organic solvent having a property of dissolving 1 to 55 parts by mass of water with respect to 100 parts by mass of the hydrophilic organic solvent. is there. The water content in the water-containing organic solvent is 10 to 120% by mass of the maximum amount of water in which the hydrophilic organic solvent can be dissolved.
[2] Production of multilayer coated film according to [1], wherein the water-containing organic solvent is an organic solvent having a property capable of dissolving 1 to 25 parts by mass of water with respect to 100 parts by mass of the hydrophilic organic solvent. Method.
[3] The above-mentioned [1], wherein the hydrophilic organic solvent is an alkyl acetate, (di) alkylene glycol monoalkyl ether, (di) alkylene glycol dialkyl ether, (di) alkylene glycol monoalkyl ether acetate or alkylene glycol diacetate. ] Or the manufacturing method of the multilayer coating film as described in [2].
[4] The hydrophilic organic solvent is methyl acetate, ethyl acetate, isopropyl acetate, n-propyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, dipropylene glycol n-propyl ether, propylene glycol n-butyl ether. , Dipropylene glycol n-butyl ether, dipropylene glycol dimethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, propylene Glycoldia A Tate or 1,3-butylene glycol diacetate, the above-mentioned [1] or [2] The method for producing a multilayer coating film according to.
[5] The method for producing a multilayer coating film according to any one of the above [1] to [4], wherein the hydrophilic organic solvent has a boiling point of 70 to 180 ° C.
[6] The above-mentioned [1], wherein the concentration in each aqueous coating liquid of the component (film forming component) capable of forming a film contained in the two aqueous coating liquids to be laminated is 20 to 50% by mass. The manufacturing method of the multilayer coating film in any one of-[5].
[7] The above [1] to [1], wherein a slide surface that is inclined when a plurality of aqueous coating liquids are previously multilayered is used, and the inclination angle of the slide surface is 5 to 40 degrees with respect to the horizontal direction. 6] The manufacturing method of the multilayer coating film in any one of.
[8] A multilayer coating film obtained by the production method according to any one of [1] to [7].

According to the present invention, a method for producing a multilayer coating film using an aqueous coating film, which suppresses mixing of two aqueous coating liquids to be laminated without using a gelling agent such as gelatin. In addition, it is possible to provide a method for producing a multilayer coating film having excellent interlaminar adhesion with ease and high productivity. In the production method of the present invention, various functions such as hard coat properties and transparency can be imparted to the multilayer coating film.
In the present invention, as described above, since it is not necessary to use an additive such as a gelling agent, an adverse effect due to the additive can be eliminated, and the manufacturing cost can be reduced.

It is a schematic diagram which shows an example of the apparatus which performs the simultaneous multilayer coating method.

  Hereinafter, the manufacturing method of the multilayer coating film of this invention is demonstrated in detail. In addition, although the manufacturing method of the simultaneous multilayer coating film of 2 layers is demonstrated below as an example, this invention is not limited to 2 layers, It is applied also to manufacture of the simultaneous multilayer coating film of 3 layers or more. Is possible.

The present invention relates to a method for producing a multilayer coating film comprising a step of multilayering a plurality of aqueous coating solutions in advance and transferring the multilayered aqueous coating solution onto a substrate. It is a method for producing a multilayer coating film, characterized in that a multilayer is formed by inserting a specific water-containing organic solvent described later as an intermediate layer between the working liquids.
As described above, the method for producing a multilayer coating film of the present invention is such that the upper layer aqueous coating liquid A and the lower layer aqueous coating liquid B are previously multilayered, and the multilayered aqueous coating liquid is transferred onto the substrate. Including a step of producing a multilayer coating film.
There is no particular limitation on the method of previously multilayering the upper layer aqueous coating solution A and the lower layer aqueous coating solution B. For example, (1) a method of multilayering on an inclined slide surface, (2) a horizontal planar shape And (3) a method of multilayering on a circular cylinder, and (4) a method of multilayering on an inclined paraboloid. Among these, the method (1) is usually preferably used.
In the present invention, a specific water-containing organic solvent is inserted as an intermediate layer between the two aqueous coating liquids to be laminated, but a clear boundary surface is not formed, but a layer separation structure is ensured as a whole. A multilayer coating film is formed. When the intermediate layer is not inserted, the aqueous coating liquids A and B are mixed and the layer separation structure cannot be maintained.

(Water-based coating medium)
The aqueous coating liquid A and the aqueous coating liquid B are aqueous coating liquids containing water as a medium. There is no restriction | limiting in particular as water which an aqueous coating liquid contains, Ion exchange water, distilled water, etc. can be used. As a medium in the aqueous coating solution, in addition to water, a water-soluble organic solvent such as acetone, methanol, or methyl ethyl ketone may be used in combination. The content of water in the medium is 80% by mass or more, preferably 90% by mass with respect to the total amount of the medium from the viewpoint of environmental protection and the solubility of the film-forming component when the present invention is industrially implemented. % Or more, more preferably 95% by mass or more, and still more preferably 100% by mass.

(Film forming component)
There are no particular limitations on the components that can form the coating film contained in the aqueous coating liquids A and B, that is, the coating film forming component, as long as they are hydrophilic and can form a coating film. For example, hydroxymethyl cellulose, hydroxyethyl cellulose , Methyl cellulose, ethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol (PVA) having a saponification degree of 50 mol% or more and its derivatives, polystyrene sulfonic acid having a sulfonation degree of 50 mol% or more, ethylene-vinyl alcohol copolymer , Polyacrylic acid and derivatives thereof, polyvinyl pyrrolidone, polyethylene glycol, alginates and the like.
The saponification degree of the PVA and its derivatives is preferably 55 mol% or more, more preferably 60 mol% or more, and further preferably 70 mol% or more from the viewpoint of enhancing water solubility. The degree of sulfonation of polystyrene sulfonic acid and its derivatives is preferably 55 mol% or more, more preferably 60 mol% or more, and further preferably 70 mol% or more from the viewpoint of enhancing water solubility.
The weight average molecular weight of the film forming component is preferably 5,000 to 1,000,000, more preferably 10,000 to 500,000, and even more preferably 50,000 to 200,000. In the present specification, the weight average molecular weight is a value in terms of polystyrene measured by gel permeation chromatography (GPC).
Specific examples of the polyvinyl alcohol derivative include carboxylated polyvinyl alcohol, sulfonated polyvinyl alcohol, acetoacetylated polyvinyl alcohol, and mixtures thereof.
In the present invention, the concentration of the film-forming component in the two aqueous coating liquids A and B to be laminated is usually preferably 20 to 50, respectively, from the viewpoint of the balance of multilayer coating film formability and productivity. It is 25 mass%, More preferably, it is 25-45 mass%.

(Other ingredients)
Each of the aqueous coating liquids further contains various additives as necessary, for example, an antioxidant, an ultraviolet absorber, a light stabilizer, a leveling agent, an antifoaming agent, a filler, a lubricant, a lubricant, and the like. Can be made.
In addition, about the solid content concentration and viscosity of the coating liquid in this invention, what is necessary is just the density | concentration and viscosity which can be applied, and it does not restrict | limit, It can select suitably according to a condition.

(Water-containing organic solvent)
The water-containing organic solvent used in the present invention is a mixed liquid of a hydrophilic organic solvent and water, and the hydrophilic organic solvent dissolves 1 to 55 parts by mass of water with respect to 100 parts by mass of the hydrophilic organic solvent. It is an organic solvent of the property to obtain. The water content in the water-containing organic solvent is 10 to 120% by mass of the maximum amount of water in which the hydrophilic organic solvent can be dissolved.
The hydrophilic organic solvent is preferably an organic solvent having a property of dissolving 1 to 25 parts by mass of water with respect to 100 parts by mass of the hydrophilic organic solvent from the viewpoint of securing a layer separation structure. Further, the water content in the water-containing organic solvent is preferably 110% by mass or less, more preferably 105% by mass or less of the maximum amount of water in which the hydrophilic organic solvent can be dissolved, from the viewpoint of securing a layer separation structure. More preferably, it is substantially 100% by mass or less. That is, even if the water is saturated, the water may be further excessively contained within the above range. Furthermore, the water content in the water-containing organic solvent is preferably 10% by mass or more of the maximum amount of water in which the hydrophilic organic solvent can be dissolved, from the viewpoint of securing a layer separation structure.

As the hydrophilic organic solvent, for example, alkyl acetate, (di) alkylene glycol monoalkyl ether, (di) alkylene glycol dialkyl ether, (di) alkylene glycol monoalkyl ether acetate or alkylene glycol diacetate are preferable.
Examples of the alkyl acetate include methyl acetate, ethyl acetate, isopropyl acetate, n-propyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate and the like.
Preferred examples of (di) alkylene glycol monoalkyl ether include dipropylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene glycol n-butyl ether and the like.
Preferred examples of (di) alkylene glycol dialkyl ether include dipropylene glycol dimethyl ether.
Examples of (di) alkylene glycol monoalkyl ether acetate include ethylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate or dipropylene glycol monomethyl ether acetate. Preferably mentioned.
Preferred examples of the alkylene glycol diacetate include propylene glycol diacetate and 1,3-butylene glycol diacetate.
The boiling point of the hydrophilic organic solvent is preferably 70 to 180 ° C, more preferably 80 to 150 ° C, from the viewpoint of reducing the energy load and drying time in the drying step.

In the present invention, it is considered that by inserting the intermediate layer, a concentration gradient is formed and mixing of the upper aqueous coating solution A and the lower aqueous coating solution B can be suppressed. The intermediate layer is preferably inserted in a wet film thickness of 1 μm to 100 μm, more preferably 5 μm to 80 μm, and even more preferably 10 μm to 50 μm.
By the way, it is not clear why the upper and lower aqueous coating liquids effectively maintain the layer separation structure by inserting the intermediate layer composed of the water-containing organic solvent. Since the intermediate layer contains water, it may be mixed with the upper and lower aqueous coating solutions. Nevertheless, the reason why the layer-separated structure can be maintained in the present invention is that the water in the intermediate layer is probably the upper aqueous coating liquid after the intermediate layer is in contact with the two types of water and sewage coating liquids. It is speculated that by moving toward the lower layer aqueous coating liquid, mixing into the lower layer from the upper layer aqueous coating liquid and mixing into the upper layer from the lower layer aqueous coating liquid was effectively suppressed. . Note that due to the movement of water from the intermediate layer to the upper and lower layers, there is no clear boundary surface in the vicinity of the boundary surface, and there is a concentration gradient of the hydrophilic organic solvent. It is presumed that the adhesion will be extremely high.

(Base material)
There is no restriction | limiting in particular in the base material which transfers the multilayered coating liquid, According to the use of the member which has a multilayer coating film, it can select suitably. Examples of the base material include polyester films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film; polyolefin films such as polyethylene film and polypropylene film; cellophane, diacetyl cellulose film, triacetyl cellulose film, and acetyl cellulose. Cellulose film such as butyrate film; Vinyl chloride film such as polyvinyl chloride film and polyvinylidene chloride film; Polyvinyl alcohol film; Vinyl copolymer film such as ethylene-vinyl acetate copolymer film; Polystyrene film; Polycarbonate Film; Polymethylpentene film; Polysulfone film; Polyetheretherketone fill , Polyether sulfone film, polyether film such as polyetherimide film; polyimide film; fluororesin film; polyamide films, acrylic resin films; norbornene resin film; cycloolefin resin films.

These substrates may be either transparent or translucent, may be colored, or may be uncolored, and may be appropriately selected depending on the application.
There is no restriction | limiting in particular in the thickness of these base materials, Although it selects suitably according to a condition, Usually, it is 15-250 micrometers, Preferably it is the range of 30-200 micrometers. Moreover, this base material can be surface-treated by the oxidation method, the uneven | corrugated method, etc. on one side or both surfaces as needed for the purpose of improving the adhesiveness with the layer provided in the surface. Examples of the oxidation method include corona discharge treatment, chromic acid treatment (wet), flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment and the like, and examples of the unevenness method include a sand blast method and a solvent treatment method. Is mentioned. These surface treatment methods are appropriately selected depending on the type of the substrate, but in general, the corona discharge treatment method is preferably used from the viewpoints of effects and operability.

(Formation of multilayer coating film)
In the present invention, as described above, a method is adopted in which a plurality of aqueous coating liquids are multilayered in advance, and the multilayered aqueous coating liquid is transferred onto the substrate.
In the case of using an inclined slide surface at the time of multi-layering, a slide coater as shown in FIG. 1 is preferably exemplified as one having an inclined slide surface for flowing an aqueous coating solution. In the present invention, a slit for the water-containing organic solvent is provided between the aqueous coating liquids A and B on the slide surface 2.
From the viewpoint of efficiently forming a multilayer coating film, the tilt angle of the slide surface is preferably 5 to 40 degrees, more preferably 10 to 35 degrees, and even more preferably 15 to 35 degrees with respect to the horizontal direction. Further, from the viewpoint of efficiently forming a multilayer coating film, the distance between the center of the discharge port of the aqueous coating solution on the slide surface and the center of the discharge port of the adjacent aqueous coating solution is 8 to 30 cm. Is preferable, 10-28 cm is more preferable, and 12-26 cm is further more preferable. In addition, from the viewpoint of efficiently forming a multilayer coating film, the center of the discharge port closest to the portion where the aqueous coating solution is transferred to the substrate among the discharge ports of the aqueous coating solution on the plurality of slide surfaces The distance from the substrate is preferably 2 to 14 cm, more preferably 3 to 12 cm, and still more preferably 4 to 11 cm. In particular, when a slide coater designed in this way is used, the effects of the present invention tend to be prominent.
Hereinafter, an example of a method of multilayering an aqueous coating solution will be described in detail with reference to the slide coater of FIG.
The aqueous coating solution A, the water-containing organic solvent, and the aqueous coating solution B are extruded from the discharge ports of the coating head 1 having at least three slit-shaped discharge ports, respectively, and naturally on the inclined slide surface 2 by the action of gravity. The aqueous coating liquids A and B are multi-layered via a water-containing organic solvent. The multilayered aqueous coating liquid (coating film) is transferred onto the base material 4 that runs by the roll 3.

A multilayer coating film can be formed by transferring the multilayered aqueous coating liquid (coating film) onto the substrate 4 and then drying by heating. The heat drying temperature is usually preferably 50 to 130 ° C, more preferably 60 to 120 ° C. Although there is no restriction | limiting in particular in heat drying time, Usually, about 1 minute-5 minutes are required.
Thus, the thickness of the multilayer coating film after drying is about 0.1 micrometer-10 micrometers normally, Preferably it is 1 micrometer-5 micrometers, and the layer which consists of each aqueous coating liquid has isolate | separated. This layer separation structure can be confirmed using, for example, an interfacial ultraviolet-visible spectroscopic measurement apparatus using slab type optical waveguide spectroscopy. Moreover, it can also confirm with the scanning electron microscope (SEM) and optical microscope of a cross section.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

Production Example 1 (Aqueous Coating Solution for Upper Layer)
30 g of polyvinyl alcohol (manufactured by Kanto Chemical Co., Ltd.), 70 g of pure water (manufactured by Kanto Chemical Co., Ltd.) and 0.5 g of Indigo (manufactured by Kanto Chemical Co., Ltd.) as a colorant for identification are mixed and stirred at room temperature. A blue aqueous coating solution 1 (polyvinyl alcohol concentration: about 30% by mass) was obtained.

Production Example 2 (Lower layer aqueous coating solution)
Hydroxyethyl cellulose (manufactured by Daicel Chemical Industries, Ltd.) 35 g, pure water (manufactured by Kanto Chemical Co., Ltd.) 65 g, and anthraquinone (manufactured by Kanto Chemical Co., Ltd.) 0.5 g as a colorant for identification are mixed and stirred at room temperature. A red aqueous coating liquid 2 (hydroxyethylcellulose concentration: about 35% by mass) was obtained.

Production Example 3 (Water-containing organic solvent for intermediate layer 1)
Propylene glycol monomethyl ether acetate (manufactured by Tokyo Chemical Industry Co., Ltd., about 18 g of water can be dissolved in 100 g) at room temperature, and 2.0 g of pure water (manufactured by Kanto Chemical Co., Ltd.) (hydrophilic) 11.7 mass% of the maximum amount of water in which the organic solvent can be dissolved) was mixed to obtain a water-containing organic solvent 1 (water content: 2 mass%).

Production Example 4 (Water-containing organic solvent 2 for intermediate layer)
To 94 g of propylene glycol monomethyl ether acetate (manufactured by Tokyo Chemical Industry Co., Ltd.) at room temperature, 6.0 g of pure water (manufactured by Kanto Chemical Co., Ltd.) (35. which is the maximum amount of water in which the hydrophilic organic solvent can be dissolved). 6 mass% equivalent) was mixed to obtain a water-containing organic solvent 2 (water content: 6 mass%).
The compositions of the aqueous coating liquids 1 and 2 and the water-containing organic solvents 1 and 2 obtained in Production Examples 1 to 4 are summarized in Table 1.

Example 1
Using the aqueous coating solution 1 produced in Production Example 1 as the upper layer aqueous coating solution, using the aqueous coating solution 2 produced in Production Example 2 as the lower layer aqueous coating solution, and further producing as an intermediate layer (mixing prevention layer) Using the water-containing organic solvent 1 produced in Example 3, a device as shown in FIG. 1 (however, a device having a slit for the intermediate layer between the water-based coating liquid A and the slit for B on the slide surface 2 is used. Inclination angle of slide surface: 25 degrees with respect to the horizontal direction, distance between adjacent discharge ports: 8 cm, distance between the center of the discharge port closest to the site where the aqueous coating liquid is transferred to the substrate and the substrate; 10 cm The film was coated on a polyethylene terephthalate film “Cosmo Shine A4100” (manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm and dried in an oven at 70 ° C. for 2 minutes to obtain a coated film.
When the cross section of the coating film was observed with a scanning electron microscope (SEM), no significant mixing of the colorant for identification was observed in the upper and lower layers to which the colorant for identification was added. The formation of the coating film was confirmed.

Example 2
In Example 1, a coating film was obtained in the same manner except that the water-containing organic solvent 2 produced in Production Example 4 was used instead of the water-containing organic solvent 1 as the intermediate layer (mixing prevention layer). .
When the cross section of the coating film was observed with a scanning electron microscope (SEM), no significant mixing of the colorant for identification was observed in the upper and lower layers to which the colorant for identification was added. The formation of the coating film was confirmed.

Comparative Example 1
In Example 1, a coating film was formed on a polyethylene terephthalate film in the same manner except that the water-containing organic solvent 1 was not inserted as an intermediate layer. When the cross section of the coating film was observed with an SEM, the colorant for identification was mixed, the interface was not secured, and the formation of the layer separation structure could not be confirmed.

Comparative Example 2
In Example 1, coating on a polyethylene terephthalate film was performed in the same manner except that dehydrated propylene glycol monomethyl ether acetate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the intermediate layer instead of the water-containing organic solvent 1. Tried. However, the aqueous coating solution 1 and the propylene glycol monomethyl ether acetate in the intermediate layer repelled on the slide surface, and a laminated structure could not be formed.

Comparative Example 3
In Example 1, it tried similarly on the polyethylene terephthalate film except having used toluene instead of the water-containing organic solvent 1 as an intermediate | middle layer. However, the aqueous coating solution 1 and the intermediate layer of toluene repelled on the slide surface, and a laminated structure could not be formed.

Comparative Examples 4-6
In Example 1, instead of the water-containing organic solvent 1, dioxane that can be dissolved in an arbitrary ratio with water (those having a water content of 1% by mass, 50% by mass, and 100% by mass, respectively) were used as the intermediate layer. A coating film was formed on a polyethylene terephthalate film in the same manner except that was used.
When the cross section of each coating film was observed with a scanning electron microscope (SEM), the colorant for identification was mixed in any case, the interface was not secured, and the formation of the layer separation structure could not be confirmed. It was.

  The production method of the present invention uses a so-called non-torque coating solution and an aqueous coating solution that do not use harmful substances such as toluene, and therefore can be widely used industrially from the viewpoint of health and environmental conservation. It is. In addition, since the multilayer coating film obtained by the present invention can impart various functions such as hard coat properties and transparency, for example, as various optical films, film antennas for cars, heat dissipation sheets, heat ray reflective films, etc. Is available.

1: Coating head 2: Slide surface 3: Roll 4: Base material A: Upper layer aqueous coating solution B: Lower layer aqueous coating solution

Claims (7)

In the manufacturing method of the multilayer coating film which has the process of multilayering a plurality of aqueous coating liquids beforehand, and transferring the multilayered aqueous coating liquid onto the substrate, between the two aqueous coating liquids to be laminated A method for producing a multilayer coating film, characterized in that a multilayer is formed by inserting the following water-containing organic solvent as an intermediate layer.
Hydrous organic solvent: A mixed liquid of a hydrophilic organic solvent and water, and the hydrophilic organic solvent is an organic solvent having a property of dissolving 1 to 55 parts by mass of water with respect to 100 parts by mass of the hydrophilic organic solvent. is there. The water content in the water-containing organic solvent is 10 to 120% by mass of the maximum amount of water in which the hydrophilic organic solvent can be dissolved.   The manufacturing method of the multilayer coating film of Claim 1 whose said water-containing organic solvent is an organic solvent of the property which can melt | dissolve 1-25 mass parts of water with respect to 100 mass parts of this hydrophilic organic solvent.   The hydrophilic organic solvent is alkyl acetate, (di) alkylene glycol monoalkyl ether, (di) alkylene glycol dialkyl ether, (di) alkylene glycol monoalkyl ether acetate or alkylene glycol diacetate. The manufacturing method of the multilayer coating film of description.   The hydrophilic organic solvent is methyl acetate, ethyl acetate, isopropyl acetate, n-propyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, dipropylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene. Glycol n-butyl ether, dipropylene glycol dimethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, propylene glycol diacetate Or 1,3-butylene glycol diacetate, a method for manufacturing a multilayer coating film according to claim 1 or 2.   The manufacturing method of the multilayer coating film in any one of Claims 1-4 whose boiling point of the said hydrophilic organic solvent is 70-180 degreeC.   The concentration in each aqueous coating liquid of the component (film forming component) capable of forming a coating film contained in the two aqueous coating liquids to be laminated is 20 to 50% by mass, respectively. A method for producing a multilayer coating film according to claim 1.   In any one of Claims 1-6 which use the sliding surface inclined when multi-layering several water-system coating liquid beforehand, and the inclination angle of this sliding surface is 5-40 degree | times with respect to a horizontal direction. The manufacturing method of the multilayer coating film of description.

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