JP2010208086A - Gas barrier film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas barrier film which ensures high productivity and has compatibility between barrier property and transparency. <P>SOLUTION: Disclosed is the transparent barrier film having a silicon oxide layer formed on a transparent base film, wherein the silicon oxide layer comprises two layers of a first layer and a second layer in order from the transparent base film side, and the refractive index and the film thickness of respective layers has following relations, the refractive index: n1>n2; the film thickness: t1<t2, and t1+t2<100, wherein, n1:the refractive index of the first layer, n2: the refractive index of the second layer, t1:the film thickness (unit:nm) of the first layer, and t2: the film thickness (unit:nm) of the second layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a gas barrier film used in the fields of food, pharmaceuticals, electronic parts and the like.

  In the above field, various transparent barrier films are used. In these applications, it is necessary to have both transparency that transmits visible light and so-called barrier properties that block gas such as water vapor and oxygen.

  Among various transparent barrier films, in order to exhibit high barrier performance, a film formed on a base film by a vacuum film forming method using an oxide thin film as a barrier layer is widely used. Among oxide thin films, silicon oxide is one of the most widely used thin films because it has both barrier properties and durability.

  However, in order to enhance the barrier performance of silicon oxide, it is necessary to use SiOx in which oxygen is scarce. As a compensation, there is a negative aspect that the transmittance decreases.

  Japanese Patent Laid-Open No. 2008-142941 proposes a structure in which silicon oxide and silicon nitride are stacked in order to achieve both transparency and barrier properties. However, since the composition is different and manufacturing is not always easy, further improvement is required.

JP 2008-142941 A

  In view of the problems as described above, an object of the present invention is to provide a gas barrier film having high productivity and having both barrier properties and transparency.

The invention according to claim 1 is a transparent barrier film formed by forming a silicon oxide layer on a transparent substrate film, wherein the silicon oxide layer is a total of the first layer and the second layer from the transparent substrate film side. A gas barrier film comprising two layers, each having a refractive index and a film thickness in the following relationship.
Refractive index: n1> n2
Film thickness: t1 <t2 and t1 + t2 <100
In the formula, n1: refractive index of the first layer, n2: refractive index of the second layer, t1: film thickness of the first layer (unit: nm), t2: film thickness of the second layer (unit: nm)

  The invention according to claim 2 is the gas barrier film according to claim 1, wherein the refractive index of the silicon oxide layer is n1> 1.5 and n2 <1.5.

  The invention according to claim 3 is the gas barrier film according to claim 1 or 2, wherein the transparent substrate film is a polyethylene terephthalate film.

  The present invention can provide a gas barrier film having both transparency and gas barrier properties.

It is sectional drawing for demonstrating the gas barrier film of this invention. It is a light transmission spectrum of Example 4, Comparative Example 1, and Comparative Example 2.

Embodiments of the present invention will be described below. FIG. 1 is a cross-sectional view for explaining a gas barrier film of the present invention, in which a first layer and a second layer, which are silicon oxide layers, are provided on a transparent substrate film.
The transparent substrate film used in the present invention may be any film as long as it has transparency and flexibility. Examples thereof include polyethylene terephthalate, polyethylene, polyethylene naphthalate, polysulfone, and nylon. Among these, a polyethylene terephthalate film having a thickness of 12 μm or more and 100 μm or less is one widely used as a transparent substrate film for a barrier film. The transparent substrate film may contain additives such as an antistatic agent, an ultraviolet absorber, a plasticizer, and a slip agent as necessary. Further, the surface may be modified such as corona treatment, plasma treatment, and easy adhesion treatment.

  The silicon oxide layer of the present invention is composed of two layers which are laminated on the transparent base film from the transparent base film side in the order of the first layer and the second layer.

  Examples of the method for forming the silicon oxide layer include a vacuum evaporation method, a sputtering method, and a plasma chemical vapor deposition method. Among these, the vacuum deposition method has the fastest film formation speed and is most advantageous in terms of cost. Examples of the vacuum deposition method used for forming a thin film of silicon oxide include EB (electron beam) heating type vacuum deposition method, resistance heating type vacuum deposition method, and induction heating type vacuum deposition method.

  The refractive indexes n1 and n2 of the first layer and the second layer constituting the silicon oxide layer of the present invention are preferably in a relationship of n1> n2. In particular, it is more preferable that the refractive index n1 of the first layer is larger than 1.5 and the refractive index n2 of the second layer is smaller than 1.5. Furthermore, the film thicknesses t1 and t2 of the first and second layers constituting the silicon oxide layer of the present invention are preferably in a relationship of t1 <t2 and t1 + t2 <100 (unit: nm). By satisfying this condition, a gas barrier film with little yellowishness and excellent barrier properties and transparency can be obtained.

  The refractive index of the silicon oxide layer can be adjusted by the amount of oxygen gas added during silicon oxide film formation and the pressure during film formation.

  From the viewpoint of maintaining the flexibility as the transparent barrier film, the total film thickness of the first layer and the second layer is preferably less than 100 nm. If it is more than this, there will be many adverse effects such as cracks in the film. Further, considering safety with respect to flexibility, the total film thickness is desirably 70 nm or less.

EXAMPLES The present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Water vapor permeability and optical properties were evaluated according to the following methods.
Water vapor permeability: Measured according to JISZ0208.
Optical characteristics: The transmittance was measured using an absolute reflectance measuring unit (5 °) with a U4000 spectrophotometer manufactured by Hitachi, Ltd. The color calculation used a D65 light source 2 ° field of view.

The contents common to the examples and comparative examples will be described.
Polyethylene terephthalate (P60, 12 μmt) was used for the transparent substrate film. As the film forming method, an EB heating type vapor deposition method (single wafer type) was used. The film forming apparatus was provided with an oil diffusion pump and a cryopanel as the main vacuum exhaust system, and the ultimate pressure was up to 10 ⁻⁴ Pa. As the vapor deposition material, a molded and baked silicon oxide material (O / Si≈1.0) was used. The parameters during film formation in this example and the comparative example were the presence or absence of oxygen gas addition during film formation and the film thickness. The pressure during film formation was 2 × 10 ⁻² Pa when oxygen gas was not added, and 4 × 10 ⁻² Pa when oxygen gas was added. When the single layer refractive index of the thin film formed in advance at a wavelength of 550 nm was measured with an ellipsometer, it was 2.01 when no oxygen gas was added and 1.43 when oxygen gas was added. The film thickness of each layer was formed after confirming the correlation in advance by taking a cross-sectional TEM image of the formed film thickness with a crystal oscillator type film thickness meter attached in the film forming apparatus.

Examples 1-4
Table 1 shows the conditions of Examples 1 to 4. In any case, the barrier property is not inferior, and particularly, it has little yellowness and excellent transparency.

Comparative Examples 1-7
Table 1 shows the conditions of Comparative Examples 1-7. Except for Comparative Example 1 which is only the base film, it can be seen that it is particularly yellowish and inferior in transparency as compared with the Examples.

  In FIG. 2, the light transmission spectrum of Example 4, the comparative example 1, and the comparative example 2 is shown. It turns out that the gas barrier film of this invention is excellent in transparency.

  As mentioned above, according to the structure of this invention, it became clear that the gas barrier film which balances barrier property and transparency is obtained.

Claims (3)

In a transparent barrier film formed by forming a silicon oxide layer on a transparent substrate film, the silicon oxide layer is composed of a total of two layers of a first layer and a second layer from the transparent substrate film side, and each refractive index. And a gas barrier film characterized in that the film thickness has the following relationship:
Refractive index: n1> n2
Film thickness: t1 <t2 and t1 + t2 <100
In the formula, n1: refractive index of the first layer, n2: refractive index of the second layer, t1: film thickness of the first layer (unit: nm), t2: film thickness of the second layer (unit: nm)   The gas barrier film according to claim 1, wherein the refractive index of the silicon oxide layer is n1> 1.5 and n2 <1.5.   The gas barrier film according to claim 1 or 2, wherein the transparent substrate film is a polyethylene terephthalate film.

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