JPH03134052A - Orientated polyester film - Google Patents

Abstract

PURPOSE:To obtain an orientated polyester film having very low shrinkage and excellent thermal dimensional stability by mixing silica particulates having a specific particle diameter. CONSTITUTION:An orientated polyester film which contains 5-50 wt.% silica particulates having an average particle diameter of 0.1 mum or less and has a thermal shrinkage factor of 1% or below (150 deg.C, 30 min) and a haze of 15% or below (in terms of value at a thickness of 12 mum). The film is useful for a mother print, flexible printed circuit board, a base for a membrane switch, an OHP, and a recording paper for a printer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to oriented polyester films with improved thermal dimensional stability.

[Conventional technology]

Due to its excellent mechanical strength, heat resistance, chemical resistance, and high transparency, oriented polyester films, represented by polyethylene terephthalate, are used for packaging, magnetic tapes, professional discs, photographic films, electrical insulation, etc. It is used in large quantities in many fields. Particularly in recent years, because of its good heat resistance, it has been widely used as a base material for flexible printed circuit boards, membrane switches, OH2, second original drawings, and recording paper for printers.

Thermal dimensional stability is an important characteristic required of the oriented polyester film when used in such applications. This is because, after a circuit diagram or design drawing is formed on a film, if the dimensions of the base film change due to the application of heat during a drying process or the like, it no longer serves as a circuit or original drawing. Particularly in recent years, the circuits used have become more complex and even the slightest dimensional change cannot be tolerated, so demands on the thermal dimensional stability of the base material are becoming increasingly strict.

[Problem to be solved by the invention]

Polyester film has excellent thermal dimensional stability compared to other general-purpose films, but it shrinks slightly at temperatures above 70°C.

Therefore, under strict requirements, they are used after being subjected to a low heat shrinkage treatment in advance.

For example, after cutting the film, leave it in a heated open,
A method is used in which the film is used after being sufficiently shrunk, or a method in which a long film wound into a roll is passed through a heating chamber and wound up while being subjected to a relaxation treatment. Furthermore, it has also been proposed to perform a similar thermal relaxation treatment in the process of manufacturing a biaxially stretched film.

However, the method of applying low heat shrinkage treatment to such films before use requires equipment for that purpose, which is not only expensive, but also causes oligomers to precipitate on the film surface, which reduces transparency. This has the drawback that it can easily cause foreign matter to adhere to the film. Also, 2
Although there are various proposals for low heat shrinkage treatment in the process of manufacturing an axially stretched film, these methods are insufficient in terms of productivity and performance, and have not been widely put into practical use. Furthermore, as an alternative to polyester film, many films made of materials having a higher glass transition point or melting point than polyester have been proposed, and some, such as polyimide film, have actually been put into practical use. However, these films are generally much more expensive than polyester, so they have not been widely used. In terms of price, attempts have been made to partially copolymerize polyester or blend heat-resistant polymers to suppress cost increases, but sufficient performance has not yet been achieved.

Furthermore, there is polyester in which at most 1.0% by weight of silica particles having an average particle size of 0.1 to 5 μm is added to polyester, but such polyester also cannot be used to form a film with good thermal dimensional stability. Can not.

Therefore, an object of the present invention is to provide an oriented polyester film with low shrinkage and excellent dimensional stability.

[Means to solve the problem]

In order to obtain an oriented polyester film with good thermal dimensional stability, we investigated how to achieve this goal by adding an inorganic compound with good thermal dimensional stability to the polyester film, and found that the average particle size was 0. By containing 5 to 50 weight i/% of silica fine particles having a diameter of .1 μm or less, an oriented polyester film having a heat shrinkage rate of 0.1% or less after treatment at 150'C for 30 minutes can be obtained. The present invention has been completed based on the discovery that the thermal dimensional stability of this material can be achieved while also satisfying properties such as transparency and mechanical strength.

That is, in the present invention, the average particle diameter is o, o o s ~
Contains 5 to 50 0.1 μm silica fine particles, 1
The oriented polyester film has a heat shrinkage rate of 1% or less at 50°C for 130 minutes. Further, the polyester film of the present invention has a haze of 15% or less when converted to a thickness of 12 μm.

The present invention will be explained in detail below.

The vine polyester used in the present invention has an aromatic dicarboxylic acid as the main carboxylic acid component, a diol having 2 to 8 carbon atoms as the main glyfur component, and is polymerized by any known method such as transesterification or direct esterification. It is made of polyester. Typical examples of such polymers include polyethylene terephthalate, polybutylene terephthalate, poly-1,4 cyclohexylene dimethylene tere 7-talate, polyethylene-2°6-7 tallate, and the like. The polyester used in the present invention includes:
In terms of thermal dimensional stability, homopoly! - is preferred, but
In order to impart other properties such as adhesiveness and transparency, a portion may be copolymerized.

As the silica particles contained in the polyester in the present invention, thermoformable silica particles generally called colloidal silica having an average particle diameter of 0.1 μm or less can be used. Furthermore, amorphous silica fine particles obtained by a dry gas phase decomposition method can also be used. These are commercially available and generally have an average particle size of 5 to 0.1 μm.

According to the present invention, the content of silica fine particles relative to the polyester film must be 5 to 50% by weight. If the content is less than 5% by weight, the desired thermal dimensional stability cannot be achieved. On the other hand, if the content exceeds 50% by weight, it will be difficult to stretch the film and mechanical strength will not reach a practical level. Furthermore, it is necessary that the average particle diameter of the silica fine particles be 0.1 μm or less.

If the average particle diameter exceeds 0.1 μm, the transparency and mechanical strength of the film will deteriorate, making it impractical.

In the present invention, the method of incorporating silica particles into polyester is generally carried out by adding a slurry in which silica particles are dispersed in a glycol component, such as ethylene glycol, to a reaction vessel when polymerizing polyester. In addition, a method of kneading molten polymer and silica fine particles under high shear force can also be used.

Incidentally, the silica fine particles are uniformly dispersed in the polyester. If the silica fine particles aggregate, the transparency and mechanical strength of the film formed will deteriorate, which is undesirable, as is the case with particles having a large average particle size. Therefore, in the oriented film of the present invention, the haze value converted to a thickness of 12 μm is preferably 15% or less, and is preferably 0.According to the present invention, the polyester containing fine silica particles is generally After melt-extruding using an extruder in step C, the desired oriented film can be obtained by carrying out the following stretching treatment and heat setting treatment.

The oriented polyester/l/film of the present invention is a film in which the molecules are oriented by stretching the above-mentioned polyester, and is a film that has been stretched and oriented by a tubular method, a tenter method, an inter-roll stretching method, or the like. Preferably, after stretching 2 to 4 times in both the longitudinal and transverse directions at a temperature 50°C higher than the glass transition point,
Preferably, the crystallization treatment is performed by heat-setting at a temperature of at least 100% or less than the melting point. Furthermore, if desired, a final thermal relaxation treatment may be performed both vertically and horizontally. The above-mentioned stretching increases the mechanical strength in the longitudinal and lateral directions, and the crystallization treatment improves chemical resistance and the like.

Further, thermal dimensional stability is further improved by thermal relaxation treatment.

The oriented film of the present invention needs to have a heat shrinkage rate of 1% or less at 150°C for 30 minutes. If the heat shrinkage rate is greater than 1%, it is not suitable for use in fields that require a high degree of thermal dimensional stability, which is the object of the present invention. For example, when used as a base material for a 7-lexiple printed circuit board, a membrane switch base material, etc., it may lead to problems such as misalignment of the circuit.

The oriented film of the present invention is dimensionally stable enough to be used as a base material for flexible printed circuit boards, membrane switches, OHP, second original drawings, recording paper for printers, etc. without special heat relaxation treatment. Because of its good performance, it is possible to significantly reduce the price. However, the oriented film of the present invention can also be effectively used in fields requiring higher thermal dimensional stability by further subjecting it to thermal relaxation treatment.

The oriented film of the present invention can also be laminated with other polyester films containing less than 5% of silica particles or films of other materials by coextrusion or lamination. However, if the laminated structure is not symmetrical with respect to the center in the thickness direction, care must be taken as curling may occur due to heat treatment. By laminating the oriented film of the present invention, the laminated film It is possible to suppress thermal shrinkage. Therefore, the laminate M made by laminating the oriented polyester films of the present invention
Films are also suitable in areas where a high degree of thermal dimensional stability is required.

The oriented polyester film of the present invention may optionally contain a heat stabilizer, an ultraviolet absorber, a lubricant, a colorant, a flame retardant, a crystal nucleating agent, etc. in addition to the silica fine particles.

〔Example〕

Next, the present invention will be explained by examples, but prior to that,
A method for measuring the fiber properties of an oriented film will be explained below.

(1) Intrinsic viscosity: Measured at 30°C using a mixed solution of phenol and tetrachloroethane in a weight ratio of 6/4 as a solvent.

(2) Heat shrinkage rate: Cut the film into a rectangle of 150m+ in the length direction and 10cm in the width direction to use as a sample piece, and heat-treat by leaving it in a tension-free state while the gear is open at a temperature of 1500C. The length of the sample was calculated from the length of the sample before and after the treatment.

(a Haze: The haze of the film was measured using an integrating sphere haze meter manufactured by Toyo Seiki in accordance with J.E.S. K6714.A film with a low value indicates good transparency.The haze is proportional to the thickness. The values are shown based on a thickness of 12 μm.

(4) Tensile strength and tensile elongation: Measured using Tensilon UTM-II-500 manufactured by Toyo Baldwin Co., Ltd. at a temperature of 23° C. and a relative humidity of 65% in accordance with J.E.S.C2318.

A general method for producing silica-containing polyester resin is shown below.

A predetermined amount of ethylene glycol slurry of silica particles was charged into an esterification reactor, and ethylene glycol was added in an amount of 2 moles or more per mole of terephthalic acid to be charged next.

Next, add antimony trioxide and sodium acetate to terephthalate.
0004 mol and O1α00 per mol respectively
08 mol was added. A predetermined amount of terephthalic acid was added while rotating the stirring blade, and while the pressure inside the reactor was maintained at 3.5 degrees/d, the temperature was raised to 250°C, esterification was performed, and the produced water was distilled off. When the water has finished distilling off, the esterified oligomer is transferred to a polycondensation reactor,
While raising the temperature from 0°C to 285°C, the pressure in the reactor was gradually reduced to carry out polycondensation. When the polymerization progressed to a predetermined stirring torque, the vacuum was broken with nitrogen and the resin was taken out.

A general method for producing an oriented film is shown below.

The silica-containing polyester resin obtained by the above production method is melt extruded through a slit using an extruder at 285 to 295°C, and the molten polymer sheet is wound up while being electrostatically adhered to a cooling drum at 30°C to form an amorphous sheet. I got it. 90 m x 90 from the center of this amorphous sheet
A square sheet of rras was cut out, and it was simultaneously stretched by 3.5 times in the right angle direction at 90'C using a small biaxial stretching machine manufactured by Toyo Seiki ■. This stretched film is 1
It was cut into a square with sides of 170 m, fixed in a stainless steel frame, and heat-set in a hot air dryer at 220°C for 10 seconds to obtain a crystallized oriented film with a thickness of about 12 μm.

When measuring the fiber properties of this oriented film, the sample was cut out from the center as far as possible. Further, the heat shrinkage rate and tensile strength/elongation were measured in each perpendicular direction, and the average values were taken.

Examples 1, 2, and 3 Organosilica sol manufactured by Catalysts & Chemical Industry ■ (dispersion medium was ethylene glycol, average particle size 0.025 μm, solid content concentration 20 weight 1, using the above-mentioned additive needle as shown in Table 1) A silica-containing polyester resin was produced by the method, and an oriented film was obtained by the general method described above.The properties of the obtained oriented film are also shown in Table 1.

Example 4 The average particle diameter of the organosilica sol used was o, o
The oriented film shown in Table 1 was obtained in the same manner as in Example 1 except that the thickness was 0 s μm.

Comparative Example 1 Example 1 except that polymerization was performed without adding silica particles.
In the same manner as above, the oriented films shown in Table 1 were obtained.

Comparative Example 2 An oriented film shown in Table 1 was obtained in the same manner as in Example 1 except that the amount of silica fine particles added was 1% by weight.

Comparative Example 3 The average silica particle diameter of the organosilica sol used was 0.2
As shown in Table 1, the oriented film of the present invention shown in Examples 1 to 4 was compared with the oriented film not containing silica particles shown in Comparative Example 1. has a small thermal shrinkage rate and greatly improved thermal dimensional stability. In comparison, even if the same silica fine particles are contained, in an oriented film whose content is less than the conventionally known 5% by weight (Comparative Example 2), the heat shrinkage rate is lower than that of Comparative Example 1, which does not contain the silica fine particles. It is almost the same as an oriented film.

In addition, when large silica particles were used as shown in Comparative Example 3, although the effect of improving the heat shrinkage rate was improved, the transparency and mechanical strength were significantly inferior, making it impractical.

〔Effect of the invention〕

The oriented polyester film of the present invention has excellent thermal dimensional stability, so it can be used for 7 lexiple printed circuit boards, membrane switch substrates and OHPs, second original drawings, etc.
1. It can be used as recording paper for printers without any post-processing such as thermal relaxation treatment; It can prevent whitening due to contamination of foreign substances and precipitation of oligomers due to processing. Further, since there is no need for post-processing, costs can be reduced, which is extremely useful. Furthermore, by carrying out thermal relaxation treatment if desired, it is possible to easily meet the requirements for higher thermal dimensional stability. In addition, it has excellent thermal dimensional stability when used as a base material for packaging materials for high temperature sterilization or for printing with ink that requires heat curing.
It is possible to prevent product distortion and flatness defects.

Claims (1)

[Claims] 1. Silica fine particles with an average particle diameter of 0.1 μm or less
An oriented polyester film containing 50% by weight and having a heat shrinkage rate of 1% or less at 150°C for 30 minutes. 2. The oriented polyester film according to claim 1, which has a haze value of 15% or less when converted to a thickness of 12 μm.