JPS6124978B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a biaxially oriented polyester film for photography, and is a biaxially oriented polyester film that is suitable for use as a photographic film base that has excellent physical properties, particularly slipperiness, and optical properties. It is intended to provide film.

More specifically, in applications such as plate making printing, X-ray photography, microfilm, electrophotography, diazo photography, etc., which require a photographic film base with excellent slipperiness and transparency, It is an object of the present invention to provide a base film that has excellent transparency and is resistant to scratches.

In the past, nitrocellulose film and cellulose diacetate film were used as plastic films for the base of photographic film, but later triacetate film became more commonly used. However, since the development of polyester film, especially polyethylene terephthalate film, its field has gradually expanded due to its excellent mechanical properties, dimensional stability, thermal properties, chemical stability, etc., and triacetate film has gradually surpassed the past. It is becoming a thing.

Polyester film has the characteristics necessary for a photographic film base: it is transparent and cloud-free; it is resistant to tension, tearing, and twisting; it is dimensionally stable and does not curl; it is stable against emulsions, water, and alkaline solutions. However, in recent years, higher-grade photographic film bases have become desirable, especially transparency and smoothness. It has become necessary to satisfy the antinomy phenomenon of gender to a higher degree.

Conventionally, there are two main methods known for improving the slipperiness of polyester films.
One method is called the precipitation method, which utilizes inert fine particles precipitated in the reaction system by polymerizing a system using an alkali metal compound or alkaline earth metal compound as a transesterification catalyst by a conventional method during polyester production. It is. In these cases, it is also possible to adjust the slipperiness by adding a phosphorus compound. Furthermore, in the case of going through an esterification step, inert fine particles can be precipitated by these methods.

If an attempt is made to obtain the desired slipperiness using the inert fine particles precipitated in this reaction system, the turbidity of the film becomes too large, making it unsuitable for use as a photographic film base. Furthermore, the amount of precipitated particles often changes, making it impossible to obtain products of stable quality.

Another method is a method called an addition method, in which fine particles of inorganic compounds such as kaolin, talc, calcium carbonate, calcium phosphate, etc. are blended during the polymerization reaction or melt extrusion process to obtain a film.

In this case, the effect of imparting slipperiness is generally relatively remarkable, but the transparency of the film is likely to be impaired, and coarse particles are often formed in the polymer, shortening the filter life and other products themselves. It also has a fatal flaw.

According to the knowledge of the present inventors, almost all inorganic compounds have poor compatibility with polyester and create voids around the particles during stretching, significantly reducing transparency.

The inventors of the present invention have conducted intensive studies paying particular attention to slipperiness and transparency, and have developed a polyester composition with a specific particle size that provides an extremely transparent film with almost no slipperiness. The present invention was achieved by discovering that this high level of demand could only be met when a biaxially oriented polyester film was produced using a raw material containing a specific small amount of porous amorphous silica.

That is, when the biaxially stretched film of the present invention has a thickness of 100μ, a polyester composition that provides a film with a film haze of 1% or less and an average particle size of
Porous amorphous silica 1 to 0.2 to 2μ
40 ppm.

The present invention will be explained in more detail below.

When a biaxially stretched film with a thickness of 100μ, which is one of the constituent requirements of the present invention, the film haze is 1%.
The polyester composition that provides the following film is a polyester containing polyethylene terephthalate as a main component, and is usually made from dimethyl terephthalate and ethylene glycol, and if necessary, other tertiary copolymer components as a transesterification catalyst. Calcium, manganese, zinc,
Polyesters obtained using compounds such as cobalt and magnesium are preferably used. In this case, it is necessary to add a phosphorus compound in order to improve the thermal stability of the polyester or to reduce its slipperiness. Alternatively, a polyester obtained by performing an esterification reaction and then a polycondensation reaction of terephthalic acid and ethylene glycol, and if necessary, another third copolymer component can also be used.

In the case of transesterification, the combinations particularly preferably used in the present invention among the above combinations are a combination of a calcium compound and a phosphorus compound or a combination of a manganese compound and a phosphorus compound; in this case, the combination of a phosphorus compound with respect to a metal compound The amount of addition is preferably 0.6 to 3 times the mole, preferably 0.7 to 2 times the mole. If the amount of the phosphorus compound added is less than 0.6 times the mole of the calcium compound, it will not be possible to obtain a film haze of 1% or less when the resulting polyester composition is made into a biaxially stretched film. Furthermore, if the amount of the phosphorus compound added is less than 0.6 times the mole of the manganese compound, even if a film with good transparency can be obtained, the thermal stability of the polymer deteriorates, and this tendency becomes particularly pronounced when recycled.

On the other hand, if the amount of the phosphorus compound added exceeds 3 times the mole of these metal compounds, the polymerization rate during polymer production will slow down, resulting in a significant industrial disadvantage.

Another method of obtaining the transparent polyester compositions required for this invention is without the use of a transesterification catalyst, ie through direct esterification. In this case, the polyester composition necessary for the present invention can usually be obtained if no metal compound is used during direct esterification, but it is preferable to add a small amount of a phosphorus compound in order to improve thermal stability. In addition, when calcium compounds or other metal compounds are added after the esterification reaction is completed, in order to improve thermal stability or reduce turbidity, the amount is 0.6 to 3 times the amount of the metal compound, preferably 0.7 to 2 times the amount by mole. It is better to add phosphorus compounds.

In this way, it is possible to obtain a polyester composition that has almost no slipperiness required for the present invention but provides an extremely transparent film.

Next, in the present invention, the transparency necessary for a photographic film is maintained by blending a specific trace amount, that is, 1 to 40 ppm, of porous amorphous silica with an average particle size of 0.2 to 2 μm to this polyester composition. Its greatest feature is that it provides smooth and slippery properties.

According to the knowledge of the present inventors, among many inorganic compounds, only porous amorphous silica does not form voids around the particles during stretching. This is probably because the silanol groups present on the particle surface react with the polyester ends to form strong covalent bonds, or because the polyester molecules penetrate through the many pores of the particle itself, or because the particle itself It is thought that this is because the polyester and the particles do not easily peel off even if a strong stretching stress is applied due to the combined effect of the stretching to some extent.

Therefore, there is almost no decrease in transparency due to the generation of voids, and the refractive index is originally close to that of polyester, and in the case of the present invention, the amount of the compound is extremely small, 1 to 40 ppm relative to polyester, so that almost no loss of transparency occurs. Nothing happens.

The porous amorphous silica used in the present invention has a specific surface area of 50 to 500 m ² /g. When the specific surface area is less than 50 m ² /g, voids often occur around the particles, resulting in a decrease in transparency. If the specific surface area is 50 m ² /g or more, the effect of the present invention is maintained, but if the specific surface area is 500 m ² /g while maintaining a specific average particle size, that is, 0.2 to 2μ.
It is industrially difficult to produce amorphous silica exceeding
Preferably, the area is 500 m ² /g or less.

In order to produce such porous amorphous silica, either a dry method, a wet method, or gelation of silicic acid is usually employed. Among these, a method based on gelation of silicic acid is particularly preferably employed, but of course commercially available silica compounds may be used if they meet the purpose of use of the present invention.

Crystalline silica is not preferred in the present invention. This is because in this case, it is generally difficult to obtain a porous material, and because there are few silanol groups on the particle surface or the particles themselves are difficult to deform, when polyester containing the particles is stretched, a large number of voids are created, which reduces the transparency of the film. This is because it will damage the

The porous amorphous silica used in the present invention should have an average particle size of 0.2 to 2 microns.

If the average particle size is less than 0.2μ, the effect of imparting slipperiness will be insufficient and workability when winding the film into a roll will be poor, and wrinkles will easily form or bumps will form on the roll surface. .

Furthermore, when stacking and aligning a number of sheets cut to a predetermined length, the workability is poor and it becomes difficult to align them, and each process is prone to scratches.

Furthermore, the particles often aggregate together to form coarse particles, resulting in a significant drawback as a photographic film.

On the other hand, if the average particle size exceeds 2μ, the film will look like it has fine heat wax in it, which will not only impair its appearance but also be particularly difficult to use when used at high magnifications, such as for aerial photography or microfilm. Particles appear as they are in the enlarged image, which is a fatal drawback.

In the present invention, the content of such porous amorphous silica must be 1 to 40 ppm based on the polyester. If this amount is less than 1 ppm, the slipperiness imparting effect will be insufficient and scratches will easily occur, which is not preferable, while on the other hand, if this amount is 40 ppm
If the amorphous silica exceeds this range, the amorphous silica has a refractive index close to that of polyester and does not generate voids during stretching, but the turbidity becomes high and the film becomes unsuitable for use as a photographic film. A particularly preferable range is 2 to
It is 15ppm.

For example, the following method is preferably used to blend the amorphous silica used in the present invention into a polyester film.

(1) When producing a polyester composition A that provides a biaxially stretched polyester film with a thickness of 100μ and a film haze of 1% or less, add 1 to 40 ppm of the amorphous silica to complete the polymerization of the polyester. A film is formed using the polyester.

(2) Catalyst system that provides polyester with good transparency;
For example, the amorphous silica-containing polyester is produced under a catalyst system for producing polyester composition A, and the polyester and polyester composition A are blended to form a film.

(3) Before forming a film The amorphous silica and polyester composition A are blended and the mixture is melt-extruded to form a film.

In any case, in the present invention, the amorphous silica must be contained in the final film in an amount of 1 to 40 ppm based on the polyester.

In order to obtain such a film, a known film forming method is used, for example, it is usually melt-extruded at 270 to 295°C into a film, cooled and solidified at 50 to 70°C to form an amorphous sheet, and then sequentially rolled vertically and horizontally. A method such as axial stretching or simultaneous biaxial stretching and heat treatment at 160 to 240° C. (for example, the method described in Japanese Patent Publication No. 30-5639) can be used.

The thickness of the biaxially stretched film in the present invention is
The diameter is 25 to 200μ, and those with a diameter of 50 to 175μ are particularly preferably used.

As detailed above, the present invention relates to a biaxially stretched polyester film for photography, which is characterized by comprising a specific polyester composition with excellent transparency and a specific trace amount of porous amorphous silica having a specific particle size. Although it was possible to achieve both transparency and slipperiness, which had been difficult in the past, it has become clear that the effects of the present invention are not limited to this, but are also excellent in the following points.

That is, the film has almost no scratches, which are called latent failures, which become apparent only when the undercoat layer is dried after being applied. This is one of the remarkable features of the film of the present invention.
This improves the drawbacks of conventional films and increases the practical value of the present invention.

Hereinafter, the present invention will be explained in more detail based on Examples.

In addition, "parts" in the examples indicate "parts by weight." The measurement method used is shown below.

Film haze: Measured using a Nippon Denshoku turbidimeter model NDH-2A according to the method of ASTMD1003-61.

Sliding property: Two films are stacked on a smooth glass plate, a rubber plate is placed on top of that, and a load is placed on top of that, and the contact pressure between the two films is 2 g/cm ² 20
The frictional force was measured by sliding the films together at a rate of mm/mm. The coefficient of friction at the point where it slid 5 mm was defined as the coefficient of dynamic friction.

Average particle size: Coulter Counter TA manufactured by Nikkaki Co., Ltd.
- Measured using a mold. Measured values are expressed as equivalent sphere values (diameter, μ).

Example 1, Comparative Example 1, and Comparative Example 2 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.07 part of calcium acetate monohydrate were placed in a reactor, heated to raise the temperature, and methanol was distilled off to perform a transesterification reaction. It took about four and a half hours after the start to reach 230°C, and the transesterification reaction was substantially completed.

Then 0.04 part of phosphoric acid and 0.035 part of antimony trioxide
part was added and polymerized according to a conventional method. That is, the reaction temperature was gradually increased to a final value of 280°C, while the pressure was gradually decreased to a final value of 0.5 mmHg. After 4 hours, the reaction was completed and polyester A was obtained (manufacture of polyester A).

Next, using this polyester A, a polyester film having a thickness of 100 μm was obtained. That is, the polymer
After extruding into a sheet shape from an extractor at 290℃ and rapidly cooling it to make an amorphous sheet, it was stretched to 3.5 times in the vertical and horizontal directions at 95℃ and heat treated at 210℃ for 10 seconds to form a biaxially stretched film with a thickness of 100μ. I got it. This film had a haze of 0.4% and good transparency, but its coefficient of dynamic friction was 0.9, making it extremely difficult to handle. Moreover, when it was wound into a roll, it was easily wrinkled and the edges were uneven, resulting in a significantly inferior commercial value (Comparative Example 1).

On the other hand, in the production of polyester A, after the transesterification reaction, the average particle size was 1.2μ and the specific surface area was 280m ² /
Amorphous silica-containing polyester B was obtained in the same manner as in the production of polyester A, except that 0.10 parts of amorphous silica (g) was added (production of polyester B).

Next, mix polyester A and polyester B at a ratio of 99:1.
A biaxially oriented polyester film having a thickness of 100 μm was obtained by blending the mixture with the following materials and forming a film in the same manner. The particles were extremely uniformly dispersed in this film, and no voids were observed around them. Therefore, the film haze was as low as 0.5% and the film had excellent transparency. Moreover, its dynamic friction coefficient is 0.4
It was easy to handle and had a good appearance when rolled, and had a high commercial value.

Next, this film was evaluated for potential scratches. Namely, 1 part gelatin, 2 parts water, 10 parts P-chlorophenol, 40 parts methanol, and acetone.
After applying a subbing agent consisting of 47 parts and drying at 120° C. for 10 minutes, the film was visually judged for scratches, and almost no latent scratches were observed (Example 1).

On the other hand, a similar evaluation was performed on a film obtained only from polyester A (comparatively 1), but
In this case, an extremely large number of scratches were observed. A polyester film containing 150 ppm of amorphous silica was also obtained and evaluated. That is, after blending polyester A and polyester B at a ratio of 85:15, a biaxially stretched polyester film having a thickness of 100 μm was obtained in the same manner. This film has a dynamic friction coefficient of
Although the film haze was low at 0.3, the film haze was extremely high at 2.5%, making it unsuitable for use as a photographic film (Comparative Example 2).

Example 2 and Comparative Example 3 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.03 part of manganese acetate tetrahydrate were placed in a reactor, and a transesterification reaction was carried out in the same manner as in Example 1.

Then 0.015 part of phosphoric acid and 0.035 part of antimony trioxide
Polyester C was prepared in the same manner as in Example 1 by adding
was obtained (manufacture of polyester C). A biaxially stretched polyester film with a thickness of 100 μm was obtained using this polyester in the same manner as in Example 1. The film haze was 0.2% and transparency was good, but the coefficient of dynamic friction exceeded 1 and handling workability was poor. It was extremely bad (Comparative Example 3).

Next, polyester C and polyester B are 98.5:
Blend to 1.5 and process as in Example 1 to a thickness of 100μ.
A biaxially stretched polyester film was obtained.

The film haze and coefficient of dynamic friction of the film were 0.4 and 0.35, respectively, and it was excellent in transparency and slipperiness, and was particularly suitable for use as a photographic film.

Note that latent flaws were evaluated in the same manner as in Example 1 and were found to be satisfactory (Example 2).

Example 3 and Comparative Example 4 In the presence of 100 parts of bis-(β-hydroxyethyl) terephthalate oligomer, 87 parts of terephthalic acid and 42 parts of ethylene glycol were reacted at 260° C. under atmospheric pressure to perform esterification. After 4 hours, a polyester oligomer with an esterification rate of 97% was obtained.

Next, take 106 parts of this reaction mixture and heat it at 260°C.
0.01 part of phosphoric acid, 0.03 part of antimony trioxide, and 0.0008 part of amorphous silica having an average particle size of 0.9 μ and a specific surface area of 300 m ² /g were added and polymerized according to a conventional method to obtain polyester D after 4 hours. (Manufacture of polyester D).

The particles were uniformly dispersed in polyester D, although in small amounts.

Next, a biaxially stretched film was obtained in the same manner as in Example 1 except that polyester D was used and the film thickness was changed. The obtained film with a thickness of 75 μm had a film haze of 0.4% and a coefficient of dynamic friction of 0.4, and was suitable for use as a photographic film in terms of transparency and slipperiness. The film was also excellent in terms of latent scratch evaluation and had high commercial value in terms of film appearance (Example 3).

Polyester E was obtained in the same manner as in the production of polyester D, except that 0.0008 part of amorphous silica was not added in the production of polyester D (production of polyester E).

Using this polyester E, a biaxially stretched film with a thickness of 100 μm was obtained in the same manner as in Example 1, but although the film haze was low at 0.3%, the coefficient of dynamic friction was high at 1 or more, making it extremely difficult to handle and work. . Moreover, when rolled into a roll, it was easy to wrinkle, the edges were uneven, and it was inferior in terms of latent scratches (Comparative Example 4).

Claims (1)

[Claims] 1. A polyester composition that provides a biaxially stretched film with a film haze of 1% or less when made into a biaxially stretched film with a thickness of 100 μm, and a porous material with an average particle size of 0.2 to 2 μm and a specific surface area of 50 to 500 m ² /g. A photographic biaxially oriented polyester film comprising 1 to 40 ppm of amorphous silica.