JP2003326636A - Strong adhesion gas barrier transparent laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminate for packaging having excellent transparency and high gas barrier properties and having high practicality from an aspect of boiling resistance and retorting resistance not generating the deterioration of physical properties, delamination or the like even after sterilization processing such as boiling sterilization, retorting sterilization or the like. <P>SOLUTION: A strong adhesion gas barrier transparent laminate is obtained by laminating a metal vapor deposition thin film layer with a thickness of 10 nm or less on at least one surface of a base material comprising a transparent plastic material and further laminating an inorganic oxide vapor deposition thin film layer with a thickness of 5-300 nm on the metal vapor deposition layer. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate for packaging used in the field of packaging foods, non-foods, pharmaceuticals, etc., and particularly packaging of contents requiring boil sterilization, retort sterilization, autoclave sterilization, etc. The present invention relates to a strong adhesive gas barrier transparent laminate suitable for.

[0002]

2. Description of the Related Art In recent years, packaging materials used for packaging foods, non-foods, pharmaceuticals, etc., contain oxygen, water vapor, which permeate them in order to suppress alteration of contents and retain their functions and properties. In addition, it is necessary to prevent the influence of a gas that modifies the contents, and it is required to have a gas barrier property of blocking these gases (gas). Therefore, conventionally, a packaging material using a metal foil made of a metal such as aluminum, which is less affected by temperature and humidity, as a gas barrier layer has been generally used.

However, a packaging material using a metal foil made of a metal such as aluminum as a gas barrier layer has an excellent gas barrier property, but it is not possible to see through the packaging material to confirm the contents. In that case, it has a problem that it has to be treated as an incombustible material and that it cannot use a metal detector during inspection.

Therefore, as a packaging material for overcoming these drawbacks, for example, inorganic materials such as silicon oxide, aluminum oxide and magnesium oxide as described in US Pat. No. 3,442,686 and JP-B-63-28017 are used. A vapor deposition film has been developed in which a vapor deposition film of an oxide is formed on a polymer film by a forming means such as a vacuum vapor deposition method or a sputtering method. These vapor-deposited films are known to have transparency and gas barrier properties against oxygen, water vapor, etc., and are suitable as a packaging material having both transparency and gas barrier properties that cannot be obtained with a metal foil or the like. .

However, even the vapor-deposited film as described above is rarely used as a packaging container or a packaging material by itself, and after vapor deposition, the vapor-deposited film is subjected to printing processing such as characters and patterns,
Alternatively, the packaging body is completed through various post-processes such as bonding with another film or the like, and further forming into the shape of a packaging container. In addition, depending on the packaging form and the contents to be packaged, sterilization processing such as boil sterilization, retort sterilization, and autoclave sterilization may be performed during or after packaging. For example, after sticking with a sealant film using the above-described vapor deposition film to form a bag, the contents may be filled to perform sterilization by boiling or retort, but in this case, a part of the sealing portion after sterilization processing is performed. Delamination may occur and the appearance may be deteriorated, or a gas barrier property may be deteriorated from that portion to deteriorate the contents, and there is a strong demand for solving these problems. That is, in designing these packaging materials, it is strongly required to take into consideration proper printing processing, proper film bonding, and various sterilization processing.

[0006] In short, as a packaging material that constitutes a package in which such various packaging forms are assumed, the transparency that allows the contents to be directly seen through, and the gas that affects the contents. It has a high gas barrier property to block the like, and does not deteriorate the gas barrier property even after sterilization processing such as boil sterilization, retort sterilization, and autoclave sterilization, and does not cause delamination, etc. Boil resistance, retort resistance, and autoclave resistance. However, at present, no packaging material satisfying all of them has been found.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and has excellent transparency and high gas barrier properties, and has physical properties even after sterilization processing such as boiling sterilization and retort sterilization. It is an object of the present invention to provide a highly practical transparent laminate for packaging, which is free from deterioration and does not cause delamination and has high boiling resistance and retort resistance.

[0008]

The present invention has been made to achieve the above object, and the invention according to claim 1 has a thickness of 10 nm or less on at least one surface of a substrate made of a transparent plastic material. A strongly adherent gas barrier transparent laminate comprising a metal vapor deposition thin film layer and an inorganic oxide vapor deposition thin film layer having a thickness of 5 to 300 nm sequentially laminated on the metal vapor deposition thin film layer.

The invention described in claim 2 is the same as claim 1.
In the strong adhesion gas barrier transparent laminate according to the item 1, the metal vapor deposition thin film layer is made of aluminum having a thickness of 10 nm or less, and the inorganic oxide vapor deposition thin film layer is made of an inorganic oxide having a thickness of 5 to 300 nm. To do.

Furthermore, the invention described in claim 3 is the method for forming a strongly adherent gas barrier transparent laminate according to claim 1 or 2, wherein the metal vapor-deposited thin film layer is either sputtering or ion plating. It is characterized by being laminated by.

Furthermore, the invention according to claim 4 is the strong adhesion gas barrier transparent laminate according to any one of claims 1 to 3, wherein the inorganic oxide deposited thin film layer is made of aluminum oxide. It is characterized by

Furthermore, the invention according to claim 5 is the strongly adherent gas barrier transparent laminate according to any one of claims 1 to 4, wherein the metal vapor deposition thin film layer and the inorganic oxide vapor deposition thin film layer are provided. Are continuously formed in the same vacuum chamber.

Furthermore, the invention according to claim 6 is the strongly adherent gas barrier transparent laminate according to any one of claims 1 to 5, further comprising a water-soluble polymer and (a)
A gas barrier coating layer is obtained by applying a coating agent containing, as a main component, an aqueous solution or a water / alcohol mixed solution containing at least one of one or more kinds of metal alkoxides and hydrolysates thereof, or (b) tin chloride, and heating and drying. It is characterized in that they are further laminated.

Furthermore, in the invention described in claim 7, in the strongly adherent gas barrier transparent laminate according to claim 6, the metal alkoxide is tetraethoxysilane or triisopropoxyaluminum, or a mixture thereof. Characterize.

Furthermore, the invention of claim 8 is characterized in that, in the strongly adherent gas barrier transparent laminate of claim 6, the water-soluble polymer is polyvinyl alcohol.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a cross-sectional configuration diagram showing a schematic configuration of a strong adhesion gas barrier transparent laminate of the present invention.

This strongly adherent gas barrier transparent laminated body is basically a substrate 1 made of a transparent plastic material, and at least one surface thereof has a metal vapor deposition thin film layer 2 having a thickness of 10 nm or less.
Then, the inorganic oxide vapor deposition thin film layer 3 having a thickness of 5 to 300 nm is sequentially laminated on the metal vapor deposition thin film layer 2. In the present invention, the gas barrier coating layer 4 may be further provided on the laminated body having such a structure according to the required quality.

The above-mentioned substrate 1 is made of a transparent plastic material, for example, polyethylene terephthalate (PE).
T), polyester films such as polyethylene naphthalate, polyolefin films such as polyethylene and polypropylene, polystyrene films, polyamide films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, polyimide films and the like are used. Each of these films may be stretched or unstretched, and an appropriate one may be selected and used in consideration of mechanical strength, dimensional stability and the like. Among these,
In the present invention, polyethylene terephthalate arbitrarily stretched biaxially is preferably used. In addition, various well-known additives and stabilizers such as an antistatic agent, an anti-UV agent, a plasticizer, and a lubricant are dispersed or applied to the base material 1 for the purpose of preventing electrification and deterioration due to ultraviolet rays. May be. In order to improve the adhesion with the thin film,
As the pretreatment, corona treatment, low temperature plasma treatment, ion bombardment treatment or the like may be applied to the surface thereof, and further chemical treatment, solvent treatment or the like may be applied.

The thickness of the substrate 1 is not particularly limited, but it is suitable as a packaging material, may be laminated with other layers, the metal vapor deposition thin film layer 2 and the inorganic oxide vapor deposition thin film layer 3 may be laminated. Further, in consideration of workability when the gas barrier coating layer 4 is formed, it is practically preferable to be in the range of 3 to 200 μm and 6 to 30 μm depending on the application.

In consideration of mass productivity, it is desirable to use a long film so that the above layers can be continuously formed.

On the other hand, the metal vapor-deposited thin film layer 2 is provided on the base material 1 made of the above-mentioned transparent plastic material, and the transparency is maintained by keeping the thickness to 10 nm or less. The purpose is to improve the adhesion with the inorganic oxide vapor-deposited thin film layer 3 made of an inorganic oxide and prevent the occurrence of delamination after boiling sterilization, retort sterilization, and autoclave sterilization. In short, the metal vapor deposition thin film layer 2 plays a role of a transparent primer layer.

The metal vapor-deposited thin film layer 2 is a thin film layer made of, for example, aluminum and is a layer provided for maintaining the adhesion between the base material 1 and the inorganic oxide vapor-deposited thin film layer 3 while maintaining the transparency as described above. The film thickness of 10 nm or less is sufficient as long as the thin metal vapor deposition layer is provided on the substrate 1. If the thickness exceeds 10 nm, the adhesion is not affected, but the transparency is lost.

As a method of forming the metal vapor deposition thin film layer 2, sputtering or ion plating is preferable. For forming the metal vapor deposition thin film layer 2 by spattering, conventionally known techniques such as a DC (direct current) sputtering method, a high frequency sputtering method, a magnetron sputtering method and a dual magnetron sputtering method can be used. For example, in the case of the sputtering method, aluminum is used as the target, an inert gas such as argon gas is introduced into the chamber, and DC, high frequency, or pulse voltage is applied to the electrodes of the target by applying DC, high frequency, or pulse voltage. The metal vapor deposition thin film layer 2 made of aluminum may be formed on the substrate 1. Alternatively, the film may be formed by magnetron sputtering using a magnetic field, which is performed by installing a permanent magnet or an electromagnet inside the electrode on which the target is installed. On the other hand, the film formation by the ion plating method may be performed, for example, by using a metal material such as aluminum as a raw material, vaporizing and ionizing the metal material in a vacuum chamber, and colliding it with the base material 1.
In the film formation by the sputtering or the ion plating method, since aluminum or the like is formed with high energy, it is said that the adhesion is very good.

The inorganic oxide vapor-deposited thin film layer 3 provided on the metal vapor-deposited thin film layer 2 is made of an inorganic oxide vapor-deposited thin film such as aluminum oxide, silicon oxide, tin oxide, magnesium oxide, or a mixture thereof. The layer is transparent and has a gas barrier property against oxygen, water vapor and the like. Among them, those composed of aluminum oxide or silicon oxide are particularly preferably used.

The optimum thickness of the inorganic oxide vapor-deposited thin film layer 3 varies depending on the type and composition of the inorganic compound used, but an appropriate thickness is selected within the range of 5 to 300 nm according to the required quality. Just set it. If the film thickness of the inorganic oxide vapor-deposited thin film layer 3 is less than 5 nm, a uniform film may not be obtained, and the function as a gas barrier layer may not be sufficiently fulfilled. When the film thickness exceeds 300 nm, flexibility cannot be maintained in the thin film, and cracks may be generated in the thin film due to external bending or pulling force applied after the film formation.
It is preferably in the range of 10 to 150 nm.

As a method for forming the inorganic oxide vapor-deposited thin film layer 3 made of this inorganic oxide on the metal vapor-deposited thin film layer 2,
Although there is a usual vacuum vapor deposition method, other thin film forming methods such as a sputtering method, an ion plating method, and a plasma vapor deposition method (CVD) can also be used. However, in view of productivity, the vacuum vapor deposition method is the best at the present time. An electron beam heating method, a resistance heating method, an induction heating method is preferable as a heating means of the vacuum evaporation apparatus by the vacuum evaporation method, and a plasma assist method or a plasma assist method is used to improve the adhesion between the thin film and the substrate and the denseness of the thin film. It is also possible to use the ion beam assist method. Further, in order to improve the transparency of the vapor deposition film, reactive vapor deposition in which oxygen gas or the like is blown during the vapor deposition may be adopted.

In forming the metal vapor-deposited thin film layer and the inorganic oxide vapor-deposited thin film layer, it is preferable that these layers are successively formed in the same vacuum chamber. This is due to contamination of the surface of the metal vapor deposition thin film layer caused by opening the laminated body in the process of production to the atmosphere after forming the metal vapor deposition thin film layer and before forming the inorganic oxide vapor deposition thin film layer. This is to prevent it.

FIG. 2 is a schematic structural explanatory view showing an example of a vacuum film forming apparatus for producing the strongly adherent gas barrier transparent laminate of the present invention. In the illustrated vacuum film forming apparatus 5, a temperature-adjustable coating drum 6 is arranged in a vacuum chamber, and is divided into a winding chamber 8 and a film forming chamber 9 by partition plates 7 and 7. In the winding chamber 8, a winding shaft 10 that allows the web-shaped plastic substrate to be wound while applying a constant back tension and a winding shaft 11 that can be wound with a constant tension are installed. In this apparatus, the substrate discharged from the unwinding shaft 10 enters the film forming chamber 9 while being held by the coating drum 6, where the film is formed and then returns to the winding chamber 8 again. Wrapped around 11 to become a product. The film formation chamber 9 is divided into a sputter chamber 12 for forming a metal vapor deposition thin film layer and a vapor deposition chamber 13 for forming an inorganic oxide vapor deposition thin film layer, and the metal vapor deposition thin film layer and the inorganic oxide vapor deposition thin film layer are continuously formed. Can be formed into a film.

On the other hand, the gas barrier coating layer 4 is provided on the inorganic oxide vapor-deposited thin film layer 3 as necessary in order to impart a gas barrier property as high as that of an aluminum foil, which is required as a laminate for packaging. is there.

The gas barrier coating layer 4 is an aqueous solution or a water / alcohol mixed solution containing a water-soluble polymer and at least one of (a) one or more metal alkoxides and a hydrolyzate or (b) tin chloride. It consists of a coating agent as the main ingredient. The gas barrier coating layer 4 is subjected to a treatment in which a water-soluble polymer and tin chloride are dissolved in an aqueous (water or water / alcohol mixed) solvent, or a metal alkoxide is directly or previously hydrolyzed. It is provided by coating the inorganic oxide thin film layer 3 with a solution obtained by mixing the above and heating and drying it.

Hereinafter, each component contained in this coating agent will be described in more detail. Examples of the water-soluble polymer used in the coating agent in the present invention include polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate and the like. In particular, when polyvinyl alcohol (hereinafter PVA) is used as a water-soluble polymer that constitutes a coating agent, it has the best gas barrier property. PVA as used herein is generally obtained by saponifying polyvinyl acetate, and includes from so-called partially saponified PVA having acetic acid groups remaining to several tens of percent to complete PVA having only a few percent acetic acid groups remaining. The type is not particularly limited.

Further, tin chloride is stannous chloride (SnCl 2
₂ ), stannic chloride (SnCl ₄ ), or a mixture thereof, and either anhydrous or hydrated can be used.

Further, the metal alkoxide is a general formula such as tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ] or triisopropoxyaluminum [Al (O-2′-C ₃ H ₇ ) ₃ ], M (OR). _n (M: metal such as Si, Ti, Al, Zr, etc .; R: alkyl group such as CH ₃ , C ₂ H ₅ etc.). Of these, tetraethoxysilane and triisopropoxyaluminum are preferable because they are relatively stable in an aqueous solvent after hydrolysis.

Each of the above-mentioned components can be added to the coating agent singly or in combination, and further, an isocyanate compound, a silane coupling agent, a dispersant, or a stabilizer as long as the gas barrier property of the coating agent is not impaired. Well-known additives such as viscosity modifiers and colorants can be added.

For example, the isocyanate compound added to the coating agent is one having two or more isocyanate groups (NCO groups) in its molecule, such as tolylene diisocyanate (hereinafter TDI) and triphenylmethane triisocyanate (hereinafter There are monomers such as TTI) and tetramethylxylene diisocyanate (TMXDI), and polymers and derivatives thereof.

As a method for applying the coating agent, conventionally known means such as a dipping method, a roll coating method, a screen printing method and a spray method which are commonly used can be used. The thickness of the coating varies depending on the type of coating agent and processing conditions, but the thickness after drying is 0.01μ
If the thickness is 50 μm or more, cracks are likely to occur in the film, so the range of 0.01 to 50 μm is preferable.

In the strongly adherent gas barrier transparent laminate of the present invention, another layer may be further laminated on the inorganic oxide thin film layer 3 and the gas barrier coating layer 4. For example, a print layer, an intermediate layer, a heat seal layer and the like. The printing layer is formed for practical use as a packaging bag, etc., and various pigments have been used for ink binder resins conventionally used such as urethane-based, acrylic-based, nitrocellulose-based, rubber-based, vinyl chloride-based, etc. It is a layer composed of an ink to which an extender pigment and additives such as a plasticizer, a desiccant, a stabilizer and the like are added, and is formed into a character or a pattern. As a forming method, for example, a known printing method such as an offset printing method, a gravure printing method, a silk screen printing method or the like, or a known coating method such as a roll coating, a knife edge coating or a gravure coating can be used. Thickness is 0.1
It may be about 2.0 μm.

The intermediate layer is provided in order to impart further functions and properties to the laminate and further improve the performance. For example, when it is provided to increase the bag breaking strength during sterilization of boil and retort, from the viewpoint of mechanical strength and thermal stability, biaxially stretched nylon film, biaxially stretched polyethylene terephthalate film, and biaxially stretched polypropylene film are generally used. This intermediate layer is composed of a film selected from The thickness is determined in accordance with the material and the required quality, etc., but is generally in the range of 10 to 30 μm, and for example, a dry lamination method in which an adhesive such as a two-component curing type urethane resin is used for bonding. It may be provided by stacking by a known method.

The heat-sealing layer is provided to provide the adhesiveness required when forming a bag-shaped package or the like. For example polyethylene, polypropylene,
Resins such as ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer and metal cross-linked products thereof. Is formed by. The thickness is decided according to the purpose,
Generally, it is in the range of 15 to 200 μm. As a forming method, it is general to use a dry laminating method or the like in which a film-like material made of the above resin is attached using an adhesive such as a two-component curing type urethane resin, but other known methods are used. You may laminate.

[0040]

EXAMPLES The strongly adherent gas barrier transparent laminate of the present invention will be further described with reference to specific examples. <Example 1> As the substrate 1, a biaxially stretched polyethylene terephthalate (PET) film having a thickness of 12 µm was used.
A film was formed on this one surface by using the vacuum film forming apparatus shown in FIG. In forming the film, first, aluminum was used as a target in the sputtering chamber, and an aluminum layer was formed to a thickness of 1 nm by the high frequency magnetron sputtering method using argon gas, and then metallic aluminum was evaporated by the electron beam heating method in the deposition chamber. While introducing oxygen gas, aluminum oxide having a thickness of 20 nm was vapor-deposited to further stack and form an inorganic oxide thin film layer. Then, a coating agent having the following composition was applied on it and dried with a dryer at 120 ° C. for 1 minute to form a gas barrier coating layer having a thickness of 0.3 μm to obtain a strong adhesive gas barrier transparent laminate. . Next, as an intermediate layer, a biaxially stretched nylon film having a thickness of 15 μm is laminated by a dry lamination method via a two-component curing type urethane adhesive, and further, as a polyolefin type thermoplastic resin layer, a low density polyethylene film having a thickness of 40 μm. Was laminated by a dry laminating method via a two-component curing type urethane adhesive to obtain a strong adhesion gas barrier transparent laminate for retort according to Example 1.

<Composition of coating agent> A mixture of liquid A and liquid B at a compounding ratio (wt%) of 60/40. (Note: A
The solution was prepared by adding 10.4 g of tetraethoxysilane to hydrochloric acid (0.1
N) A hydrolyzed solution having a solid content of 3 wt% (converted to SiO ₂ ) which was hydrolyzed by adding 89.6 g and stirring for 30 minutes. Liquid B is a 3 wt% water / isopropyl alcohol solution of polyvinyl alcohol (water: isopropyl alcohol weight ratio 9
0:10)).

Comparative Example 1 A gas barrier transparent laminate according to Comparative Example 1 was obtained under the same conditions as in Example 1 except that the thickness of the aluminum layer formed by spattering was 15 nm.

<Comparative Example 2> A gas barrier transparent laminate according to Comparative Example 2 was obtained under the same conditions as in Example 1 except that the aluminum layer was not formed.

<Test 1> For Examples and Comparative Examples,
A four-way pouch was prepared for sterilization by retort, 150 g of water was filled as a content, and sterilized by boiling at 90 ° C. for 30 minutes. As an evaluation, oxygen permeability before and after boiling (c
c / m ² / day) and laminate strength (gr / 15m
m) was measured and the state of delamination after boil was visually observed. The results are shown in Table 1.

[0045]

[Table 1]

The gas barrier transparent laminate according to the comparative example has a transparency that allows the contents to be directly seen through and a gas that affects the contents under the conditions of being used as the packaging material for the boil described above. It does not satisfy all of the high gas barrier properties for blocking the above, and the boiling resistance without deterioration of the gas barrier properties after boiling and the occurrence of delamination and the like, but it can be said that the examples satisfy all of them.

[0047]

As described above, according to the present invention,
It has excellent transparency and a highly adhesive gas-barrier transparent laminate for packaging, which has a high level of gas barrier properties similar to that of aluminum foil, and is also suitable for boiling. Widely usable.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram showing a schematic configuration of a strong adhesion gas barrier transparent laminate of the present invention.

FIG. 2 is a schematic configuration explanatory view showing an example of a vacuum film forming apparatus for producing a strong adhesion gas barrier transparent laminate of the present invention.

[Explanation of symbols]

1 base material 2 Metal evaporated thin film layer 3 Inorganic oxide deposition thin film layer 4 Gas barrier coating layer 5 Vacuum film forming equipment 6 coating drum 7 partition boards 8 winding room 9 Film forming chamber 10 Unwinding axis 11 winding shaft 12 Sputter room 13 evaporation chamber 14 Sputtering electrode and target 15 electron gun 16 crucibles

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C23C 14/08 C23C 14/08 A 14/20 14/20 (72) Inventor Kenjiro Kuroda Taito, Taito-ku, Tokyo 1-5-1, Toppan Printing Co., Ltd. (72) Inventor Shunichi Shiokawa 1-5-1, Taito, Taito-ku, Tokyo Top-term Printing Co., Ltd. F-term (reference) 4F100 AA05D AA17C AA19C AB01B AB10B AK01A AK21D AT00A BA04 BA07 EH66B EH66C GB15 JD02 JD02D JL11 JN01 JN01A YY00B YY00C 4K029 AA11 AA25 BA03 BA44 BB02 BC07 CA03 CA05

Claims (8)

[Claims] 1. A metal vapor deposition thin film layer having a thickness of 10 nm or less, and an inorganic oxide vapor deposition thin film layer having a thickness of 5 to 300 nm on at least one surface of a substrate made of a transparent plastic material. A strong adhesion gas barrier transparent laminate, which is characterized by being laminated in order. 2. The metal vapor deposition thin film layer is made of aluminum having a thickness of 10 nm or less, and the inorganic oxide vapor deposition thin film layer has a thickness of 5 nm.
The strong adhesive gas barrier transparent laminate according to claim 1, which is made of an inorganic oxide having a thickness of 300 nm. 3. The strong adhesion gas barrier transparent laminate according to claim 1, wherein the metal vapor-deposited thin film layers are laminated by any method of sputtering or ion plating. 4. The strongly adherent gas barrier transparent laminate according to claim 1, wherein the inorganic oxide vapor-deposited thin film layer is made of aluminum oxide. 5. The metal vapor-deposited thin film layer and the inorganic oxide vapor-deposited thin film layer are continuously formed in the same vacuum chamber, as claimed in any one of claims 1 to 4.
A strong adhesive gas barrier transparent laminate according to item. 6. A coating agent comprising an aqueous solution or a water / alcohol mixed solution containing a water-soluble polymer, (a) at least one metal alkoxide and its hydrolyzate, and (b) at least one of tin chloride as a main component. The strong adhesive gas barrier transparent laminate according to any one of claims 1 to 5, further comprising a gas barrier coating layer formed by applying the above composition and heating and drying. 7. The strong adhesive gas barrier transparent laminate according to claim 6, wherein the metal alkoxide is tetraethoxysilane, triisopropoxyaluminum, or a mixture thereof. 8. The strong adhesive gas barrier transparent laminate according to claim 5, wherein the water-soluble polymer is polyvinyl alcohol.