JPH0985918A - White laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white laminated polyester film wherein whiteness and weathering resistance are highly improved, and it can be produced at a low cost. SOLUTION: 2-40wt.% of Anatase titanium dioxide of a mean particle size within a range of 0.1-1.0μm is contained in at least one side outermost layer of a laminated polyester film. 2-40wt.% of Rutile titanium dioxide of a mean particle size within a range of 0.1-1.0μm is contained in at least one layer of the layers excepting that.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white laminated polyester film, and more particularly to a white laminated polyester film which is highly improved in whiteness and weather resistance and can be produced at low cost.

[0002]

2. Description of the Related Art Biaxially oriented polyester film represented by polyethylene terephthalate is used as a base material for information recording materials and capacitors because of its excellent mechanical properties, electrical properties, chemical resistance and dimensional stability. It is used in many fields such as printing, wrapping, plate making, electricity loss, photographic film, etc.

[0003] In recent years, polyester film has been utilized for its properties as a whiteboard for electronic whiteboards, and also for magnetic cards such as credit cards, telephone cards, JR cards, and pachinko cards for finance, communication, and entertainment. Widely used in transportation facilities.

In particular, prepaid cards and the like have an added value as a design product, such as a premium added to the price displayed on the face of a card depending on the design of the printed surface, in combination with the excellent printing technology. ing. In this case, the whiteness of the white polyester film as the base material is particularly important in order to make the contrast of the pattern vivid and to reveal the delicate contrast of the shadow. Furthermore, in this application, the magnetic layer applied to the side opposite to the printing surface of the prepaid card is colored blackish brown or the like due to the magnetic material or binder that composes it. Therefore, the degree of hiding of the base film is extremely important so as not to reduce the whiteness of the printed surface.

However, in such applications, the white polyester film used as a base material is concealed because it is used while being affected by changes in temperature and humidity indoors and outdoors or by ultraviolet rays from sunlight and indoor fluorescent lamps. Is likely to decrease over time and the whiteness tends to decrease. These problems are caused by a phenomenon based on a deterioration reaction of titanium dioxide contained as a white masking agent in a white polyester film due to ultraviolet rays and temperature and humidity.

As a measure for preventing deterioration due to ultraviolet rays, it is known to incorporate an ultraviolet absorber into the white polyester film. This makes it possible to prevent deterioration to some extent.

However, since the organic ultraviolet absorber is generally easily decomposed by heat or oxidatively, for example, the film forming temperature of polyethylene terephthalate is 270 ° C. or higher.
At 300 ° C., the ultraviolet absorber undergoes thermal decomposition or sublimation and its ultraviolet absorbing ability is significantly reduced, and it is difficult to maintain sufficient weather resistance even if an organic ultraviolet absorber is added to the white polyester film. .

As a method for preventing deterioration of a white polyester film due to changes in ultraviolet rays and temperature / humidity to improve so-called weather resistance, Japanese Patent Publications No. 7-5763 and No. 7-5764 disclose zinc compounds. The use of anatase type titanium dioxide containing aluminum compounds, aluminum compounds, silicon compounds, etc. has been proposed.

However, titanium dioxide containing such a metal compound has the following problems. First, the inclusion of the metal compound sometimes reduces the whiteness of the polyester film. That is, the b value representing yellowness increases. Second, it is necessary to newly add a treatment facility for treating with the metal compound as described above to the titanium dioxide particle production facility, which increases the production cost of titanium dioxide and raises the price of the final product film.

By the way, titanium dioxide has two types of crystal forms, anatase and rutile. However, rutile generally has a lower optical activity, so that the deterioration rate of a coating film due to exposure is slower than that of anatase. Therefore, rutile has better weather resistance than the anatase-type titanium dioxide containing a metal compound. Under such circumstances, rutile type titanium dioxide is widely used as an industrial pigment for paints and the like, has a large production amount, and is lower in price than anatase type titanium dioxide. Since rutile looks more yellowish than anatase, there is a problem that it cannot be applied to a white polyester film that requires whiteness.

[0011]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a white laminated polyester film which is highly improved in whiteness and weather resistance and can be produced at low cost. To provide.

[0012]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventor has made anatase titanium dioxide excellent in whiteness an outermost layer, and weatherproofs other layers. By having a laminated structure having at least one layer containing excellent rutile titanium dioxide,
The present invention has been completed by finding that the hiding power and whiteness can be maintained and the manufacturing cost of the film can be reduced.

That is, the gist of the present invention is that the outermost layer of at least one of the laminated polyester films contains 2 to 40% by weight of anatase type titanium dioxide having an average particle size of 0.1 to 1.0 μm. The white laminated polyester film is characterized in that at least one layer other than the above contains 2 to 40% by weight of rutile type titanium dioxide having an average particle size in the range of 0.1 to 1.0 μm.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The polyester referred to in the present invention refers to a polymer containing an ester group obtained by polycondensation of a dicarboxylic acid and a diol or a hydroxycarboxylic acid. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid. As diols, ethylene glycol, 1,4
-Butanediol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol and the like. Examples of the hydroxycarboxylic acid include p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid.

Typical examples of such a polymer include polyethylene terephthalate and polyethylene 2,6 naphthalate. These polymers may be homopolymers or may be copolymers of a third component.

In the present invention, anatase type titanium dioxide is blended with the polyester forming the outermost layer. The anatase type titanium dioxide may be an anatase type titanium dioxide containing an aluminum compound, a zinc compound, silicon dioxide or the like as long as the whiteness is not impaired.

Specific examples of the aluminum compound include aluminum oxide, aluminum hydroxide, aluminum carbonate, aluminum chloride and the like. Specific examples of the zinc compound include zinc acetate, zinc benzoate, zinc oxide, zinc carbonate, zinc chloride, zinc hydroxide, zinc lactate,
Examples thereof include zinc phosphate, zinc sulfate, and zinc nitrate. Among these, a zinc compound having good heat resistance is preferable.

The above compound may be contained inside the anatase type titanium dioxide or may be present on the surface thereof. Examples of the method of incorporating the above compound into the anatase type titanium dioxide include a method of adding the above compound during the production of the anatase type titanium dioxide, a method of surface treating the anatase type titanium dioxide with the above compound, and the like.

The amount of the aluminum compound or zinc compound contained in the anatase titanium dioxide is preferably 2.0% by weight or less in terms of aluminum or zinc element,
1.0% by weight or less is particularly preferable. When the content of the aluminum compound or the zinc compound exceeds the above range, the thermal stability of the polyester decreases, and problems such as film breakage tend to occur during film formation. Silicon dioxide has an effect of improving dispersibility of anatase type titanium dioxide in polyester by including it in the anatase type titanium dioxide in a ratio of 1.0% by weight or less in terms of silicon element.

In the present invention, rutile type titanium dioxide is blended with the polyester constituting at least one layer other than the outermost layer. The rutile type titanium dioxide may contain the above-mentioned aluminum compound, zinc compound, silicon dioxide or the like. The content is preferably set in the same range as described above.

As a coating method using the above compound as a surface treatment agent, (a) an alumina layer is provided on the surface of rutile type titanium dioxide, (b) an alumina / titania coprecipitation layer is provided, and (c) a high density. Examples of the method include a method of coating with a silica layer and then with an alumina layer, and a method of (d) coating with a porous silica layer and then with an alumina layer. It is not limited to.

The rutile type titanium dioxide may be further treated with an organic substance. As a compound used for organic matter treatment,
Examples thereof include polyol-based compounds such as pentaerythritol / trimethylolpropane, alkanolamine-based compounds such as organic acid salts such as triethanolamine / trimethylolamine, silicon resins, and silicon-based compounds such as alkylchlorosilanes. The treatment amount of the organic substance treatment is usually 0.5% by weight or less, and when the C analysis value of the pigment is 0.06% by weight or more, it can be considered that the organic substance treatment is performed. The above compound binds to and covers the new surface of the pigment particles generated by the crushing, and thus suppresses the recombination due to the collision between the pigment particles. Therefore, the organic substance treatment is effective for improving the pigment dispersibility.

The titanium dioxide used in the present invention has an average particle size of 0.1 to 1.0 μm, preferably 0.2 to 0.5 μm.
m range. If the average particle size is less than 0.1 μm,
The light transmittance becomes large and the white hiding effect becomes insufficient,
When the average particle size exceeds 1.0 μm, the original whiteness of titanium dioxide decreases.

The content of the anatase type titanium dioxide with respect to the polyester constituting the outermost layer is 2.0 to 40% by weight, particularly preferably 5.0 to 30% by weight. When the content of the anatase type titanium dioxide is less than 2.0% by weight, the light transmittance becomes large and the hiding effect becomes insufficient,
On the other hand, if it exceeds 40% by weight, the mechanical strength of the polyester is lowered and, for example, problems such as film breakage occur during film formation.

The amount of rutile type titanium dioxide compounded in the polyester constituting the layers other than the outermost layer is 2.0 to 40.
%, Particularly preferably 5.0 to 20% by weight. Such a blending amount is defined by the same meaning as in the case of anatase type titanium dioxide.

The white laminated polyester film of the present invention can be produced by laminating by coextrusion and then biaxially stretching. Titanium dioxide can be added at any stage of the polyester film manufacturing process. The production method of titanium dioxide is not limited as long as it satisfies the conditions specified above.

In the present invention, the weather resistance and whiteness are not adversely affected, the number of coarse particles is not increased, and the smoothness of the polyester film surface is not adversely affected. Inert particles other than titanium dioxide may be used in combination as long as they have an average particle size and content. Further, so-called precipitation type fine particles precipitated by the reaction of the catalyst residue and the phosphorus compound in the polyester reaction system can be used together.

The thickness of the polyester layer constituting the outermost layer is usually 0.1 to 50 μm, preferably 0.2 to 40 μm.
m. If the thickness is less than 0.1 μm, the outermost layer becomes thinner than the particle diameter of the anatase type titanium dioxide used for the outermost layer of the biaxial polyester film, and the titanium dioxide particles are likely to fall off the film surface. It is difficult to expose the excellent whiteness of titanium dioxide. On the other hand, when it exceeds 50 μm, the effect of increasing the whiteness of the anatase type titanium dioxide decreases.

The thickness of the polyester layer constituting at least one other outermost layer is determined by the total thickness of the intended white laminated polyester film. What happens
Since the layer thickness of the outermost layer is selected from 0.1 μm to 50 μm, for example, the thickness of the polyester base film of the pachinko card is usually 188 μm. The total thickness of the other layers is 148 μm.

Specific examples of the layer structure of the white laminated polyester film of the present invention include (a) two kinds of two layers containing anatase type titanium dioxide in one outermost layer and rutile type titanium dioxide in the other layer. Examples thereof include a film, and (b) a two-kind three-layer film containing anatase type titanium dioxide in the outermost layer (both sides) and rutile type titanium dioxide in the intermediate layer. There is no limitation. Further, as a stretching method, a conventionally known method can be adopted.

[0031]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. The measuring methods used in the following examples and comparative examples are as follows. Also,
In Examples and Comparative Examples, “%” means “% by weight” and “part” means “part by weight”.

(1) Average particle size Centrifugal sedimentation type particle size distribution measuring device ("SA-C" manufactured by Shimadzu Corporation)
The value of the integrated (weight basis) 50% in the equivalent spherical distribution measured by "P3 type") is used.

(2) Whiteness of film This was measured using a color difference meter (“TC-5D type” manufactured by Tokyo Denshoku Co., Ltd.). The whiteness is represented by the b value, and the smaller the value, the higher the whiteness. In addition, the larger the b value, the stronger the yellowish color, which indicates yellowing.

(3) Concealment Degree The density of transmitted light under the G filter was measured using a Macbeth densitometer (TD-904 type). The larger this value is, the higher the hiding power is.

(4) Evaluation of Moisture and Heat Resistance The film was exposed in a moist heat oven in an environment of 85 ° C. and 98% RH, and 17 days later, using the Macbeth densitometer (TD-904 type) of the above (3). The transmission density (OD value) was measured. The larger the ratio (OD ′ / OD:%) of the initial OD value and the OD value (OD ′) after 17 days, the better the moist heat resistance.

(5) Evaluation of UV resistance Using a UV long life fade meter (“FAL-3 type” manufactured by Suga Test Instruments Co., Ltd.), UV irradiation was performed at 63 ° C. ± 3 ° C. for 300 hours, and then (2) above. Color difference meter (TC-5
The b value was measured using D type). Initial b value and 30
The greater the difference (Δb = b′−b) in the b value (b ′) after 0 hours, the poorer the weather resistance.

Example 1 (Production method of polyester chip) 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol and 0.07 part of calcium acetate-hydrate were placed in a reactor, heated and heated to distill off methanol for transesterification reaction. After the reaction was started, it took about 4 and a half hours to reach 230 ° C. to substantially end the transesterification reaction.

Next, 0.04 part of phosphoric acid and 0.035 part of antimony trioxide were added, and polymerization was carried out according to a conventional method. That is, the reaction temperature was gradually raised to 280 ° C., while the pressure was gradually reduced to finally reach 0.05 mmH.
It was set to g. After 4 hours, the reaction was completed, and chips were obtained by a conventional method to obtain polyester.

(Production of Masterbatch Chip) 60 parts of the obtained polyester and an average particle diameter of 0.
A master-batch chip (A) was obtained by melt-mixing 40 parts of 3 µm anatase type titanium dioxide in a twin-screw extruder according to a conventional method. Separately, 60 parts of polyester and 40 parts of rutile titanium dioxide having an average particle diameter of 0.3 μm produced by a conventional method were melt-mixed in a twin-screw extruder according to a conventional method to obtain a masterbatch chip (R).

(Film Forming Method) The Polyester Chip (A)
And (R) are separately blended with polyester to adjust the blending amount of titanium dioxide to be 7%, and then 18
It was dried at 0 ° C for 5 hours, co-extruded and then rapidly solidified, and the length and width were 3.1 times at 83 ° C and 3.6 times at 125 ° C.
2 times, biaxially stretched one after another, and then heat treated at 230 ° C. for 1
A 88 μm white laminated biaxial polyester film was obtained.
The layer structure was such that a polyester layer containing 7% of anatase type titanium dioxide was used as the outermost layer (thickness 15 μm), and a polyester layer containing 7% of rutile type titanium dioxide was used as the intermediate layer (thickness 15%).
8 μm). The properties of the obtained white laminated biaxial polyester film are shown in Table 1, and the whiteness and weather resistance are very good. In Table 1, titanium dioxide type A is anatase and R is rutile.

Example 2 The same procedure as in Example 1 was carried out except that the anatase titanium dioxide content was 20% and the rutile titanium dioxide content was 5%. An axially stretched polyester film was obtained. The properties of the obtained laminated film are shown in Table 1, and have the properties which are very satisfactory as in Example 1.

Comparative Example 1 The procedure of Example 1 was repeated except that the titanium dioxide used for the intermediate layer of the film was changed to anatase type titanium dioxide.
A white laminated biaxial polyester film was obtained in the same manner as in Example 1. Table 1 shows the properties of the obtained laminated film.

Comparative Example 2 A white laminated biaxially stretched polyester film was prepared in the same manner as in Example 2 except that rutile titanium dioxide was used as the outermost layer of the film in place of the anatase titanium dioxide. Obtained. Table 1 shows the properties of the obtained laminated film.

[0044]

[Table 1] ──────────────────────────────────── Example Comparative Example 1 2 1 2 <Max Outer layer> Titanium dioxide type A A A R Titanium dioxide concentration 7 20 7 20 Layer thickness (μm) 15 15 15 15 <Intermediate layer> Titanium dioxide type R R A R Titanium dioxide concentration 7 5 7 5 Layer thickness (μm) 158 158 158 158 <Total thickness (μm)> 188 188 188 188 188 <Physical properties> Initial opacity (OD) 1.13 1.14 1.15 1.13 Initial b value -2.3 -2.6 -2.5 -1.0 OD '/ OD 98 97 84 97 Δb 0.6 0.7 4.0 0.6 <Comprehensive evaluation> ○ ○ × × ────────────────────────────────────

[0045]

The white laminated polyester film of the present invention described above has a high degree of whiteness and hiding power, and these characteristics can be maintained at a high level even when exposed to ultraviolet rays and changes in temperature and humidity. Moreover, it is excellent in productivity and cost, and its industrial value is very large.

Claims (1)

[Claims] 1. An outermost layer of at least one of the laminated polyester films contains 2 to 40% by weight of anatase type titanium dioxide having an average particle size of 0.1 to 1.0 μm, and at least one of the other layers. Has an average particle size of 0.1
The rutile titanium dioxide in the range of
A white laminated polyester film comprising 40% by weight.