JPH11322973A - Clear polyester film for vapor deposition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a clear polyester film for vapor deposition which is excellent in adhesion to vapor-deposited metal oxide, esp. adhesion after retorting, by incorporating fine porous silica particles having specified properties into the same. SOLUTION: This polyester film contains 0.005-20 wt.% fine porous silica particles which are substantially mononuclear and have an average particle size of 1.0-10 μm, a micropore vol. of 0.1-1.0 ml/g, an average micropore size of 0.05-100 nm, and an oil absorption of 200 ml/100 g or lower. Pref., the cloudiness of the film is 0-5%. The fine porous silica particles are required to be substantially mononuclear. Silica particles in the form of aggregates are unfavorable since such aggregates have a high moisture absorptivity and each aggregate has an insufficient strength, and as the results, defects in a vapor-deposited thin film layer are liable to occur during retorting and the gas barrier properties are degraded. If necessary, the silica particles may be subjected to a surface treatment for preventing aggregation and then dispersed in a resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyester film for transparent vapor deposition. More specifically, excellent adhesion to transparent metal oxide deposited thin film, excellent retort resistance, food,
The present invention relates to a polyester film for vapor deposition, which is required to be airtight, such as pharmaceuticals and electronic components.

[0002]

2. Description of the Related Art Polyester films, especially polyethylene terephthalate films, have been used as components of many flexible packaging films because of their advantages in mechanical strength and thermal dimensional stability. Among them, when used for food packaging and the like, it is general to impart gas barrier properties to prevent deterioration of the contents.

As a method of imparting gas barrier properties, a method of laminating a polyester film and an aluminum foil, a method of depositing a metal such as aluminum on a polyester film, and the like are used. However, these methods have excellent gas barrier properties. However, there is a drawback that the obtained film is opaque and the contents to be packaged cannot be seen, and its use is limited.

As another method, another material having a gas barrier property and having transparency,
For example, a method in which polyvinylidene chloride, polyethylene polyvinyl alcohol copolymer, or the like is bonded or provided by coating is used. However, these methods have a drawback that although a transparent film is obtained, the heat resistance is poor, and the gas barrier property is deteriorated by a high-temperature moist heat treatment such as a retort treatment. In addition, vinylidene chloride-based polymers generate chlorine-based gas during combustion and the like, and there is a concern about the effect on the environment.

Further, as a gas barrier film which is transparent and heat resistant and can be used in a microwave oven, a gas barrier film having a thin layer provided by depositing or sputtering a metal oxide such as silicon oxide or aluminum oxide on a base film is known. Its development has attracted attention from today's global environmental problems.

However, even such a gas barrier film on which a metal oxide having excellent heat resistance is deposited has a disadvantage in that the gas barrier property is greatly reduced when a severe treatment such as a retort treatment is performed. As a cause of this, it is considered that the vapor-deposited film undergoes dimensional change due to moisture absorption and the adhesion between the metal oxide layer and the polyester film is deteriorated, so that cracks and cracks occur in the metal oxide layer, and the gas barrier properties are significantly reduced. .

In order to solve this problem, attempts have been made to improve the adhesion by increasing the deposition thickness or applying a primer treatment to the base film. However, when the film thickness is increased, the bending resistance deteriorates. In addition, ancillary equipment is required for the primer treatment, which complicates the processing step, and any method is not preferable because it increases the product cost. Therefore, a polyester film having low hygroscopicity and good adhesion to a metal oxide film has been desired.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a transparent vapor-deposited polyester film which is excellent in vapor deposition adhesion of metal oxides, particularly after vapor deposition after retort treatment, and maintains gas barrier properties. is there.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to improve these problems, and as a result, by using a polyester film containing silica fine particles having a specific property as a substrate, a retort treatment was performed. Later, they found that the gas barrier property could be prevented from lowering, and reached the present invention.

That is, according to the present invention, the average particle size is 1.0
-10 μm, pore volume of 0.1-1.0 ml / g, average pore diameter of 0.05-100 nm, and oil absorption of 200 ml / g
A polyester film for transparent vapor deposition characterized by being 100 g or less and containing 0.005 to 20% by weight of substantially mononuclear porous silica fine particles.

Here, the transparent vapor deposition means forming a transparent thin film on a film by vapor deposition of a metal oxide such as silicon oxide or aluminum oxide.

The polyester film for transparent vapor deposition of the present invention can form a metal oxide vapor-deposited layer on at least a part of one or both surfaces, and if necessary, anchor coat between the substrate film and the metal oxide layer. A layer may be provided.
Examples of the anchor coat layer include a copolymerized polyester compound, an acrylic copolymerized compound, and a urethane compound, and these can be used alone or as a mixture. These are provided during the formation of the base film,
So-called in-line coating may be used, or it may be provided in a separate step.

The metal oxide thin film may be formed by a conventional method, for example, a physical method such as vacuum deposition, reactive deposition, sputtering, reactive sputtering, ion plating, or reactive ion plating. The film can be formed by a CVD method, a plasma CVD method, a laser CVD method, or the like as a chemical method, for example.
In addition, as a method for heating the evaporation source, for example, a heating method such as resistance heating, high-frequency induction heating, or electron beam heating can be used.

In the present invention, the thickness of the metal oxide thin film is
It is preferably from 5 to 150 nm. If the thickness is less than 5 nm, it is difficult to obtain a sufficient gas barrier property, and if it exceeds 150 nm, it is disadvantageous in terms of cost and the flexibility is undesirably reduced.

As the metal oxide used for vapor deposition, for example, oxides of aluminum, silicon, magnesium, calcium, titanium, chrome, zinc and the like can be mentioned. These can be used alone or in a mixture of a plurality of types, and can be used by laminating a plurality of types. Among these, oxides of silicon and aluminum are preferred. These may be organic metal compounds such as metal alkoxides or inorganic metal compounds such as halides as starting materials. After vapor deposition, it can be used as it is, or can be used by being laminated with another base material, for example, polyethylene, polypropylene, nylon or the like, if necessary, using an appropriate anchoring agent. The lamination method is not particularly limited, but a method such as a dry lamination method or an extrusion lamination method is preferable.

The polyester forming the base film of the polyester film for transparent vapor deposition of the present invention is a crystalline line synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Is a saturated polyester. Specific examples of the polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene 2,6-naphthalenedicarboxylate, and the like. These include copolymers or blends of these with small proportions of other resins. Among these, polyethylene terephthalate, polyethylene-
2,6-Naphthalenedicarboxylate is preferred.

The porous silica fine particles used in the present invention must be substantially mononuclear porous silica fine particles. Porous silica fine particles composed of aggregates have high hygroscopicity and lack the strength of the fine particles themselves, which is not preferable because the vapor deposition thin film layer is likely to have a defect during retort processing and the gas barrier property is lowered.

The porous silica fine particles in the present invention must have an oil absorption of 200 ml / 100 g or less. When the oil supply amount exceeds 200 ml / 100 g, the hygroscopicity increases, which is a disadvantage during retort processing, and the gas barrier property is undesirably reduced.

Here, the oil absorption is a value obtained by measuring according to JIS K5101, and is represented by the oil absorption of natural linseed oil with respect to 100 g of a sample.

The porous silica fine particles in the present invention need to have an average pore diameter of 0.05 to 100 nm. If the average pore diameter is less than 0.05 nm, the affinity at the interface with the polyester is insufficient, and it is easy to fall off from the surface after film formation. On the other hand, if it exceeds 100 nm, the strength of the porous silica fine particles themselves is low, and the It is not preferable because it is easy to be crushed during kneading and it is difficult to maintain properties.

Here, the average pore diameter is a value determined by measuring the surface area with a surface area measuring device and calculating the pores as cylindrical based on the surface area and the pore volume.

The porous silica fine particles in the present invention need to have an average particle diameter of 1.0 to 10 μm.
If it is smaller than 1.0 μm, the handleability as a base film tends to be inferior, and if it exceeds 10 μm, coarse projections tend to be formed, which is not preferable.

The porous silica fine particles in the present invention need to have a pore volume of 0.1 to 1.0 ml / g. When the amount is less than 0.1 ml / g, it is not preferable because it does not easily adapt to dispersion on a substrate. On the other hand, if it exceeds 1.0 ml / g, the specific gravity becomes low, the dispersibility in the base polyester becomes low, and the strength of the fine particles themselves becomes low, so that it is difficult to maintain the properties at the time of kneading into the polyester.

Here, the pore volume is such that when pure water is dropped on 5 g of a sample, the sample eventually becomes a uniform hard putty, and when the dropping is continued, the pure volume in a state where moisture can be visually recognized on the sample surface is determined. It is expressed as the volume of water dropped per gram of sample.

The content of the porous silica fine particles in the base polyester film is 0.005 to 20% by weight.
Needs to be When the content is less than 0.005% by weight, the slipperiness of the film becomes insufficient. On the other hand, if it exceeds 20% by weight, it becomes unfavorable because it tends to become coarse projections on the film surface.

The porous silica fine particles used in the present invention are substantially mononuclear porous silica fine particles, and may be subjected to a surface treatment, if necessary, before being dispersed in the polyester resin in order to prevent aggregation. Can be applied. As the surface treatment method, a known method can be used. Known surface treatment agents can be used. For example, various organic silicon compounds, organic titanium compounds, lower alcohols, higher alcohols, derivatives such as ethylene glycol, etc., which can react with silanol groups on the surface of the silica fine particles can be used. These can be used alone or in combination of two or more.

Within a range that does not impair the object of the present invention,
If necessary, other organic or inorganic fine particles can be used in combination with the porous silica fine particles substantially consisting of a mononuclear particle. Examples of such fine particles include inorganic fillers such as silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, titanium oxide, zinc oxide, barium sulfate, etc., crosslinked silicone resins, crosslinked polystyrene resins, crosslinked acrylic resins, urea. Organic fillers made of a heat-resistant resin such as a resin and a melamine resin can be used.

Further, resins other than polyesters such as polyethylene, polypropylene, ethylene-propylene terpolymer, and olefinic ionomers, coloring agents, antistatic agents, catalysts, stabilizers, antioxidants, ultraviolet absorbers, flame retardants, and fluorescent enhancers A whitening agent and the like may be contained as necessary within a range not to impair the object of the present invention.

In the present invention, the polyester film as the substrate film may have a thickness generally used as a polyester film for vapor deposition, and preferably has a thickness of 4.5 to 50 μm, particularly preferably 9 to 25 μm.

In the present invention, the base film is preferably subjected to a stretching treatment, but is preferably subjected to a preheat treatment before the stretching treatment. When the polyester film is polyethylene terephthalate, the pre-heat treatment of the polyester film is preferably performed at 90 to 130 ° C. for 1 to 20 seconds. In the subsequent stretching treatment, the film is stretched 2.0 to 5.0 times, preferably 3.0 to 4.0 times in the machine direction at a temperature of 60 to 140 ° C., preferably 90 to 125 ° C., and then at a temperature of 6 to 140 in the transverse direction.
0 to 150 ° C, preferably 2.0 to 90 to 140 ° C
It is preferably stretched 5.0 times, preferably 3.0 to 4.0 times. In addition, it is desirable that the area magnification after longitudinal and transverse stretching is 20 or less.

Further, a method of performing unidirectional stretching in multiple stages of two or more stages can be used, but also in this case, the final stretching ratio is within the above range, and the intermediate heat treatment is performed after the second stage stretching. After that, the film may be stretched again in the same direction as the first step and / or in the same direction as the second step.

The heat setting after the stretching is preferably performed at a temperature higher than the final stretching temperature and lower than the melting point for 1 to 30 seconds. For example, for polyethylene terephthalate film,
It is preferable to heat set at 250 ° C. for 2 to 30 seconds. At that time, the contraction or elongation within 20%, or under a fixed length, may be carried out, or may be carried out in two or more stages.

The polyester film for vapor deposition in the present invention preferably has a haze of 0 to 5%. If the haze exceeds 5%, the appearance after vapor deposition may be deteriorated, or the glossiness of the film may be reduced when vaporized.

[0034]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the present invention, various physical properties and characteristics are measured and defined as follows.

(1) Average Particle Diameter of Porous Silica Fine Particles Using a Shimadzu automatic sedimentation balance, the settling time corresponding to each particle diameter is calculated using the Stokes equation shown below, and the range of each particle diameter is calculated. Is determined, and the weight of the inert substance within the settling time range is determined to be the composition ratio to the total weight of the inert substance. An integration curve is created by integrating the obtained composition ratios in descending order of particle size, and an integration rate of 5
The particle size indicated by 0% is defined as the average particle size. T = 18ηh / [G (ρ _p −ρ _o ) × d ² ] where T: sedimentation time (sec) η: viscosity of medium (g / cm × sec) h: sedimentation distance (cm) G: gravity Acceleration (980 cm / sec ² ) ρ _p : density of inert substance (g / cm ³ ) ρ _o : density of medium (g / cm ³ ) d: particle size of inert substance (cm)

(2) Pore volume 5 g of a sample was placed in a flask, and pure water was gradually dropped from a burette. The whole sample was eventually formed into a uniform hard putty. There is a point on the surface where moisture can be seen. The amount of pure water immediately before the visual recognition was determined and expressed in ml / g.

(3) Oil absorption The oil absorption is measured according to JIS K5101, and is expressed as the oil absorption of natural linseed oil per 100 g of sample (ml / 100 g).

(4) Average Pore Diameter A sample of 0.10 to 0.15 g is weighed, the surface area is measured by a simple and quick surface area measuring device (SA-1000, manufactured by Shibata Kagaku), and the pores are regarded as one cylindrical shape. Using the value of the pore volume, the value was calculated from the following equation. Average pore size = 4 ×
Pore volume / surface area

(5) Oxygen Permeability According to JIS K-7126, an oxygen permeability at 25 ° C. is measured using a gas permeability measuring device (MC-1 type, manufactured by Toyo Seiki). ^{2.0cm 3 / (m 2 / 24hr} / atm) of less than a which it is desirable.

Example 1 Polyethylene terephthalate was subjected to transesterification of manganese acetate, a polymerization catalyst of antimony trioxide, dimethyl terephthalate using phosphorous acid as a stabilizer, and an average particle diameter of 3.7 μm and a pore volume in a conventional manner. Was polymerized using ethylene glycol in which mononuclear porous silica fine particles having an average pore diameter of 1.9 nm and an oil absorption of 80 ml / 100 g were dispersed. The concentration of the silica fine particles in the obtained polyethylene terephthalate was 0.035% by weight. The resin was supplied to an extruder, melt-extruded from a slit die, and quenched and solidified on a rotary cooling drum having a surface temperature of 30 ° C. to obtain an unstretched sheet.

The unstretched sheet was stretched 3.6 times in the machine direction at a stretching temperature of 90 ° C. to obtain a uniaxially stretched film. Next, one side of the uniaxially stretched film was stretched 4.0 times in the transverse direction while drying at 100 ° C., and once cooled, subjected to a 5% relaxation treatment in the width direction while being subjected to a heat treatment at 230 ° C. to a thickness of 12 μm. Was obtained. This film is supplied to a vacuum evaporation apparatus, and the film is formed under a vacuum of 3 × 10 ⁻⁵ Torr.
SiO and SiO ₂ are heated and evaporated by a kw electron beam heating method, and a 50 nm thick Si
An evaporated film on which a transparent thin film of O _x was formed was obtained.

Next, a urethane-based adhesive (Dick Dry LX-7, manufactured by Dainippon Ink and Chemicals, Inc.) was applied to the deposition surface of the film.
After applying 3 μm of a two-component adhesive in which 03A and KR-90 were mixed at a ratio of 15: 1), a low-density polyethylene film (manufactured by Tamapoly, V-1) having a thickness of 50 μm was laminated by a dry lamination method. .

The resulting laminate film was measured for oxygen permeability, and subjected to a retort treatment (120 ° C. × 30).
Min) was also measured. The results are shown in Table 1.

Example 2 Mononuclear porous silica fine particles having an average particle diameter of 2.0 μm, a pore volume of 0.95 ml / g, an average pore diameter of 11.2 nm, and an oil absorption of 180 ml / 100 g were used. Except for changing to 0.050% by weight.
A laminate film was obtained in the same manner as in Example 1. The properties of this film are shown in Table 1.

Comparative Example 1 Mononuclear porous silica fine particles having an average particle diameter of 3.6 μm, a pore volume of 1.35 ml / g, an average pore diameter of 18.4 nm, and an oil absorption of 230 ml / 100 g 0 0.035% by weight except
A laminate film was obtained in the same manner as in Example 1. The properties of this film are shown in Table 1.

Comparative Example 2 Porous silica fine particles having an average particle diameter of 1.9 μm, a fine pore volume of 1.50 ml / g, an average fine pore diameter of 19.8 nm, and an oil absorption of 270 ml / 100 g and comprising an agglomerated nucleus 0 A laminated film was obtained in the same manner as in Example 1 except that the thickness was changed to 0.050% by weight.
The properties of this film are shown in Table 1.

[Comparative Example 3] Porous silica fine particles having an average particle diameter of 1.2 µm, a pore volume of 1.75 ml / g, an average pore diameter of 22.3 nm, and an oil absorption of 330 ml / 100 g, comprising an aggregated nucleus 0 A laminated film was obtained in the same manner as in Example 1, except that the composition was changed to 0.065% by weight.
The properties of this film are shown in Table 1.

Comparative Example 4 Porous Silica Fine Particles Consisting of Aggregated Nucleus with Average Particle Diameter of 2.3 μm, Pore Volume of 1.90 ml / g, Average Pore Diameter of 25.2 nm, and Oil Handling Volume of 320 ml / 100 g Except for changing to 0.050 weight,
A laminate film was obtained in the same manner as in Example 1. The properties of this film are shown in Table 1.

[0049]

[Table 1] ―――――――――――――――――――――――――――――――― Oxygen permeability Oxygen permeability after retort treatment cm ³ / (m ² / 24hr / atm) cm ³ / (m ² / 24hr / atm) ―――――――――――――――――――――――――――― ―――――――― Example 1 1.2 1.4 Example 2 1.4 1.6 Comparative Example 1 1.3 2.8 Comparative Example 2 1.2 2.6 Comparative Example 3 1.4 3.5 Comparative Example 4 1.2 3.7 ――――――――――――――――――――――――――――――――――――

[0050] Table than 1, in the film obtained in Example, the oxygen permeability ^{1.2~1.4cm 3 / (m 2 / 24hr} / at
m), the oxygen permeability after retort treatment is 1.4 to 1.6 cm ³ /
(m ² / 24hr / atm), which was very excellent.

[0051] However, in the film of the comparative example using the present range of porous silica, met oxygen permeability embodiment similar to the ^{1.2~1.4cm 3 / (m 2 / 24hr} / atm) despite, neither after retorting 2.0cm ³ / (m ^2/24
(hr / atm) or more, the barrier property was remarkably reduced, and was unsuitable as a gas barrier film.

[0052]

The polyester film for transparent vapor deposition of the present invention is excellent in metal oxide vapor deposition adhesion and retort resistance, so that the gas barrier property in the post-processing step, product production and cooking is reduced. It is less useful as a substrate for a polyester film for transparent vapor deposition.

Claims (2)

[Claims] An average particle diameter of 1.0 to 10 μm, a pore volume of 0.1 to 1.0 ml / g, and an average pore diameter of 0.05 to 1
00 nm and an oil absorption of 200 ml / 100 g or less, and a substantially mononuclear porous silica fine particle
A polyester film for transparent vapor deposition, characterized in that it contains from 0.5 to 20% by weight. 2. The polyester film for transparent vapor deposition according to claim 1, wherein the degree of haze is 0 to 5%.