JPS62140828A - Polyester film for transparent electrically conductive film - Google Patents

Abstract

PURPOSE:To prevent occurrence of whitening phenomena caused by oligomer precipitation in case of heat treatment by making a film haze less than 2.5% and making a deposited quantity of oligomer precipitation less than 5mg/m<2> when it is heat-treated at 130 deg.C for 2hr. CONSTITUTION:A polyester film, which has a film haze of less than 2.5% and has a deposited quantity of oligomer precipitation of less than 5mg/m<2> after heat treatment at 130 deg.C for 2hr, is obtained as follows. The oligomer is eliminated from the polyester by means of a solid-phase polymerization of polyester chips, which have been obtained by a usual melt polymerization method and contain substantially no particle or a small amt. of particles, by retaining the temp. at 180-240 deg.C for 1-10hr under reduced pressure of under a flow of an inert gas. The polyester film can be thereafter obtained by melt extrusion and by stretching adequately. It is desirable to use the polyester film whose shrinkage rate under heat treatment at 160 deg.C for 30min has been set to be less than 2.5% by heat treatment before preparing a transparent electrically conductive membrane in order to prevent a crack caused by shrinkage of a base film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyester film for use in transparent conductive films. Specifically, the present invention relates to a polyester film suitable for use as a transparent conductive film, which is provided with a transparent conductive layer on at least one side of the polyester film, which prevents precipitation of low-molecular compounds (oligomers) consisting of components forming polyester on the film surface.

<Prior Art> With the recent remarkable development of electrical and electronic components, various switches and switches using transparent conductive films have been developed. Examples include thin film switches such as transparent touch panels and electronic display devices such as liquid crystal displays.

In the production of transparent touch panels, a transparent conductive film is used, in which a transparent conductive thin film is provided on one side of transparent polyester by vapor deposition, sputtering, or the like. The general manufacturing method is to remove unnecessary parts by etching, form a transparent circuit, print the necessary conductive circuit for extraction, and then print a part of the spacer with insulating paint. There are known methods such as stacking and laminating films with the printed surfaces facing each other and laminating them with an insulating material interposed as a spacer.

In general, conductive parts are printed using silver paste, etc. Normal touch panels are used by setting them on various displays such as cathode ray tubes (!RT) and liquid crystal displays (LOD), and the base film is biaxially stretched. Polyester film is used, but in combination with a polarizing plate, LC
When used for D, a -axially stretched polyester film is used.

On the other hand, various methods are known for displaying LCDs, but the guest-host type using dichroic dyes and the twisted nematic type using optical rotation due to the twisted arrangement of nematic liquid crystals are widely adopted. There is. In the former case, a biaxially stretched polyester film is used, and in the latter case, a uniaxially stretched polyester is used, and a transparent conductive film is used, which is made in the same manner as in the touch panel.

By the way, since touch panels, r, +CDs are used in combination with other electrical and electronic components, dimensional stability at high temperatures is often required, and it is desirable that the thermal shrinkage rate of the transparent conductive film be as small as possible. As a means to reduce the thermal shrinkage rate, methods have been adopted, such as sputtering or vapor deposition on a polyester film that has been heat-treated to reduce the shrinkage rate, or heat-treating the transparent conductive film after making it to reduce the shrinkage rate. ing. Transparent conductive films made with an appropriate shrinkage rate using this method are used for touch panels and LCDs, but in order to prevent wrinkles from forming on the film when pasting the transparent conductive films together,
The vertical and horizontal shrinkage rates may be controlled as appropriate. Especially to some extent in the lateral direction, for example /40°C! 0 after heat treatment for 1 minute. If you give it a shrinkage rate of about /%,
Wrinkles appear when pasting the sheets together.

<Problems to be Solved by the Invention> It has been found that when a normal polyester film is used as a paste for the above-mentioned transparent conductive film, problems arise due to the oligomer contained in the polyester. That is, in the method of providing a transparent conductive film on a normal polyester film and then screen printing,
During the drying process, which takes several minutes to 7 hours at temperatures ranging from
This raises the issue of increased transparency and decreased transparency.

Here, even if the drying process is improved to prevent oligomer precipitation and adhesion, oligomer precipitation and adhesion occur during the heat treatment stage of the transparent conductive film in order to reduce the shrinkage rate as a final product, resulting in the problem that the film becomes cloudy. . or,
In such a heating process, the film shrinks and the transparent conductive film is likely to crack, causing transparent grooves 1! Situations may occur in which the performance of the film is impaired or it becomes difficult to perform printing multiple times with high precision.

Among the above problems, a method to solve the problem associated with shrinkage of polyester film is to shrink the film by heat treatment before forming a transparent conductive film by vapor deposition or sputtering, and then perform vapor deposition or sputtering. The method is to do so. However, although this method solves the problem of shrinkage of the film, oligo i- precipitates during heat treatment and reduces the adhesion of the transparent conductive film to the polyester film. However, the problem of reduced transparency of the film cannot be solved.

<Means for solving the problems> The present invention solves the problems caused by oligomers, and provides a film suitable for transparent conductive films in which the turbidity of the film hardly increases even when the polyester film is subjected to heat treatment. The present invention provides a polyester film.

That is, the gist of the present invention is that the film haze is 2! The present invention provides a polyester film for a transparent conductive film, characterized in that the amount of oligomer deposited upon heat treatment at 130° C. for one hour is not more than j■/rrL2. Even if the film of the present invention is provided with a transparent conductive layer and then subjected to heat treatment, no clouding phenomenon due to oligomer precipitation occurs.

More preferably, among the above polyester films,
When heat treated at 760°C for 3θ minutes, the shrinkage rate of the film in the vertical and horizontal directions is θ,! The film header is 3. A polyester film is used which is less than or equal to θ and has an amount of deposited oligomer as defined above of less than 70 cm/7FL1.

The present invention will be explained in detail below.

The polyester in the polyester film of the present invention refers to an aromatic dibasic acid or an ester-forming derivative thereof,
A highly crystalline linear saturated polyester synthesized from diol, specifically polyethylene terephthalate,
Polyethylene isophthalate, polyethylene-2, lh
-f phthalate and the like.

The polyester film of the present invention may be an unstretched film, a -axially stretched film, or a biaxially stretched film, and has a thickness of J~3! A θμ wind is used. In particular, -axially stretched films and biaxially stretched films are preferred. As raw materials for the polyester film, for the purpose of the present invention, polyester containing virtually no particles, inorganic particles such as calcium carbonate, kaolin, chestnut, etc., and precipitated particles formed from the residue of the catalyst used in the reaction are used. It is possible to use polyester containing within the achievable range.

The polyester film of the present invention, that is, the film haze is 2. ! A polyester film that is less than , or polyester chips containing a small amount of particles under reduced pressure or
The polyester is obtained by solid-phase polymerization at /rO<0>C to <0>C for about 10 hours under inert gas flow to remove oligomers from the polyester, followed by melt extrusion and appropriate stretching. Transversely or longitudinally oriented films and also biaxially oriented films are obtained by employing known stretching conditions.

Furthermore, since the precipitation and adhesion phenomenon of oligomers occurs only on the surface layer of a polyester film, the polyester film of the present invention can also be obtained by a method in which an ordinary polyester is used as an inner layer, and a solid phase polymerized polyester is coextruded on the surface layer and then stretched. I'm happy.

Incidentally, the amount of oligomer precipitated and deposited in a film formed as it is from raw materials obtained by a normal melt polymerization method at 130° C. for 2 hours is −20 Wl/y(″).

After providing a transparent conductive film on the polyester film of the present invention to form a transparent conductive film, no clouding occurs at all even when heat-treated at 0°C or higher, but transparent grooves 1! There may be cases where the film cracks and quality is compromised.

In order to prevent this problem, it is preferable to use a polyester film that has been heat-treated to have a heat treatment shrinkage rate of 00j% or less at 760° C. for 30 minutes before providing the transparent conductive film.

In the present invention, transparent groove 1! For the purpose of improving the durability of the layer, known subbing agents such as organosilane compounds such as mono-, di-, and trialkoxysilane compounds and their derivatives, organotitanium compounds such as titanium esters and titanium acylates, etc. It is also possible to set a layer.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

In addition, in the following Examples and Comparative Examples, "part" means "part by weight". Further, the viscosity, haze of the film, light transmittance of the film, amount of deposited oligomer, and heat shrinkage rate of the film were measured as follows.

Measurement of viscosity: Polyester film/f is dissolved in a mixed solvent of phenol/tetrachloroethane=/// (weight ratio) 700.1, and the viscosity is measured at 30°C.

An integrating sphere precision haze meter measures the incident light amount (TI=/θO setting) and total light transmission amount (T-
), the amount of scattered light by the device (T3), and the amount of scattered light by the device and the test piece (1=) are determined, and the haze (H) is calculated using the following formula.

Using a double beam spectrophotometer and a tungsten lamp light source, the light transmittance was continuously measured in the wavelength range of 110 to 100 nm, and a record chart was written. Onm
Read the light transmittance at wavelength.

! Ows X @ 0■ test piece /! Immerse the solution in chloroform at 30°C for 20 minutes,
The absorbance at nm was measured using a spectrophotometer (Ei newly manufactured by Hitachi).
PEKTROPHOTOMKTERJ! ? ), and the amount of oligomer is calculated from the calibration curve created in advance.

The unit is M9/m'.

Heat shrinkage rate of the film: J pieces of test pieces each with a width of about 2 m x a length of 10 θ (or product width) were taken from the longitudinal and transverse directions of the film.
Cut it out. The sample is heated for a predetermined time in a hot air circulation constant temperature bath set to a predetermined temperature, taken out, immediately cooled with water, and the total length is read to the nearest /m using a stainless steel scale, and calculated using the following formula.

Example/700 parts of dimethyl terephthalate, 60 parts of ethylene glycol, and 0.0 parts of calcium acetate hydrate? 7 parts were heated to a transesterification tank Kl), the temperature was raised, methanol was distilled off, and the temperature was raised to 1.230° C. over a period of time for fishing bait to complete the transesterification reaction. Next, this reaction product was placed in a polymerization tank, and while maintained at 230°C, amorphous silica θ with an average diameter of t μ (average diameter measured by Coulter counter method is /, μ), 00. A solution of 2 parts dispersed in 0.0 parts ethylene glycol is added, followed by 0.0 parts phosphoric acid dispersed in 0.0 parts ethylene glycol. O
J 7 parts, tertiary antimony 0, and OJ 7 parts were added and polymerized by a conventional method, and the intrinsic viscosity was 0. A polyester of 1/2 was obtained, extracted into strands, and cut into chips. (This chip is referred to as Chip A.) Chip A was also heated at λθ°C for 70 hours in a nitrogen stream to obtain a solid phase polymerized chip. (Let this chip be Chip B.) Chip B is 2? The amorphous sheet was obtained by melt extrusion with an average residence time of 3.5 g in the longitudinal direction.
Stretched 3.6 times in the transverse direction, heat treated at 230°C,
Film haze o, r% light transmittance/7. A film with a thickness of j%/θ0μ was obtained. 130°C of the film,
The amount of oligomer deposited after heat treatment for one hour was 10♂1
When heat-treated at 7660° C.j min at 1Q/m”, the heat shrinkage rates in the longitudinal and transverse directions were /, 9% and 0%, respectively.

A mixture of indium oxide and tin oxide was sputtered onto the polyester film according to a conventional method to prepare a transparent conductive film. Transparent conductive film @0CIILX
@Cut into 0CWL pieces, /! O'C: Even after 2 hours of heat treatment, no oligomer adhesion was observed, and the transparency and appearance were good.

A film having a film haze of 0.1%, a light transmittance of 11%, and a thickness of 100 μm was obtained in exactly the same manner as in Comparative Example/Example, except that polyester B was replaced with polyester. The amount of oligomer deposited on the film at 130°C for 2 hours is /
It was 311115I/-.

Next, sputtering was carried out in the same manner as in Example 1 to obtain a transparent conductive film, and heat treatment was performed at 0°C for 2 hours. As a result, oligomer deposition was observed on the non-sputtered surface, and the appearance was significantly deteriorated. .

The polyester film of Example 1 was heat-treated by passing it through a floating type furnace blowing hot air at 210° C. under a tension of 'Is//m width for /θ seconds. The haze of the film is 0.2%,
When the film was heat-treated at 130°C for 2 hours, the amount of oligomer precipitated was 3 mq/m''. When the film was heat-treated at 760°C for 30 minutes, the longitudinal and lateral shrinkage was 0.2%, respectively. At θ, the amount of oligomer deposited is
j~/, Ll.

A transparent conductive film was obtained in the same manner as in Example. Since this product already has low shrinkage, it can be used as is, but depending on the application, 76% can be used to further reduce shrinkage.
Even after heat treatment at 0° C. for 7 hours, no oligomer precipitation was observed from the appearance.

Comparative Example The film of Comparative Example/ was subjected to the same heat treatment as in Example 2,
A low shrinkage film was obtained.

This low-shrinkage film showed partial oligomer deposition and had faint stain-like marks, and was of poor quality to be used as a transparent conductive film. Such oligomer precipitation and adhesion was concentrated at locations such as scratches and press marks created during film forming, slitting, and heat treatment steps before heat treatment.

When the film was heat-treated at 740°C for 30 minutes, the amount of oligomer precipitated was 2j/rIL''.
The film haze of the oligomer precipitation area is 3.5.
It was Chi.

<Effects of the Invention> When the polyester film of the present invention is used as a base film for a transparent 411i film, the disadvantages of insufficient adhesion of the transparent grooves tNj and cloudiness of the film due to oligomer precipitation adhesion do not occur, and the polyester film of the present invention can be used as a transparent film with low shrinkage. A conductive film can be produced.

Sender: Diafoil Co., Ltd. Representative Patent attorney (if necessary) - Others/Name

Claims (1)

[Claims] (1) Film haze is 2.5% or less, and 1
A polyester film for a transparent conductive film, characterized in that the amount of oligomer deposited upon heat treatment at 30° C. for 2 hours is 5 mg/m^2 or less.