JPS62149415A - Manufacture of low shrinkable polyester film - Google Patents

Abstract

PURPOSE:To obtain a low shrinkable polyester film excellent in flatness by a method wherein a plurality of sheets of polyester film, the shrinkage factor of which is below specified value, and piled up and heat-treated within the specified temperature range. CONSTITUTION:A plurality of sheets of polyester film, the shrinkage factor of which is 0.8% or less when placed at 150 deg.C for 2hr, are piled up and heat- treated in a furnace of 150-220 deg.C. Because the flatness is improved and the heat shrinkage factor is lowered in advance as mentioned above, a slow shrink polyester film the flatness of which is excellent when cut and heat-treated and the shrinkage factor of which is 0.1% or less when placed at 150 deg.C for 2hr.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing a low shrinkage polyester film. More specifically, the present invention relates to a low shrinkage film with good flatness and a method for producing the same.

<Conventional technology> With the modernization of electrical and electronic components, thin film switches such as tamembran switches and touch panels using plastic films have appeared, replacing the conventional bush type, slide type, and rotary type switches. Also, among various flexible substrates, substrates in which circuits are printed directly on plastic films have appeared.

The manufacturing method for thin film switches such as membrane switches and touch panels is usually to print a circuit with conductive paint on one side of a polyester film, then print a spacer part with insulating porcelain, and then print the printed side on the opposite side. Known methods include stacking films together and bonding them together, and printing circuits with conductive paint and then bonding them together with the printed surfaces facing each other with an insulating material interposed as a spacer.

Generally, the method of printing a conductive circuit on the surface of a polyester film such as polyethylene terephthalate is as follows.
Screen printing of barrel-conductive paints such as silver paste has been adopted.

In this method, first, silver paste is printed and dried, and then carbon paste is printed to cover the printed area of the silver paste to prevent the silver from oxidizing, thereby forming a circuit. be. However, printing with carbon paste is performed when using a material that easily oxidizes, such as silver paste, as a 4-electroconductive paint, and when using a conductive paint that does not oxidize, printing the paint alone is sufficient. It is. Screen printing is also used when providing insulating spacers. Further, depending on the intended use of the switch, display printing may be applied, and screen printing is also used in this case.

<Problems to be Solved by the Invention> As described above, screen printing is performed several times in the manufacturing process of thin film switches, but drying after printing is usually performed within the range of /30 to 110°C. It requires heat treatment at a temperature of from several minutes to one hour. However, under such drying conditions, the film shrinks due to heating, making it difficult to perform subsequent printings with high precision. ,
When pasting them together, it may be difficult to past them together accurately.

In order to prevent such problems caused by shrinkage, a method has been adopted in which the polyester film is heat-treated to shrink it before the printing process.

The heat treatment method involves cutting the polyester film to an appropriate size depending on the application and the size of the screen printing machine, then stacking it in a pile of 10 to several hundred sheets and heat-treating them in a hot air oven. Common. At this time, if the size of the cut polyester film is small, it can be heat-treated without impairing its flatness, but if the 7 sides of the cut product exceed the SOO dragon, the flatness of the film after heat treatment will deteriorate. Unfortunately, it may not be possible to screen print the film with high precision.

The present inventors have discovered that the above drawbacks are caused by the heat treatment method and the properties of the polyester film used for the heat treatment, and have arrived at the present invention.

Means for Solving the Problems> The gist of the present invention is to stack a plurality of polyester films whose shrinkage rate is 0.1% or less when placed in an atmosphere at 730°C for one hour, ～---The shrinkage rate when placed in an atmosphere of 150°C for one hour characterized by heat treatment in a furnace at The film is heat treated. In a specific embodiment, the polyester film is first heated to an appropriate size, for example, 5ooHNxsoo.
After cutting to the size of Ryuya & 001H heat-treated in the If the cut size is relatively small, such as 100 x 100 x 100 x 100 x 100 x 100 x 100 x 100 x 100 x 100 x 100 x 100 mm, even ordinary films can be heat-treated with good flatness. Sexuality often worsens.

Examples of deterioration in flatness include: l) As shown in FIG. 1, the edges of the film are wavy, making it impossible to print accurately in the printing process.

e) As shown in Figure 1, a maximum of 20 mm in the plane of the film.
For example, a film having a thickness of 11 it or more and a length of zoH1 or more has bulges of 1 or more, making it impossible to print accurately in the printing process.

During heat treatment, flatness often deteriorates if the film and stainless steel are connected to each other during heat treatment. In the present invention, in order to prevent this blocking, a polyester film and a stainless steel plate are used. In Hyogo, it is possible to use a method such as coating a stainless steel plate with 11 bales of Isuri I++ Tacoat, or placing a film coated with I2 IHJ between them.

Thick'-"b uu T kk-:>circle//7L
11! if↑I ノ1jjr AM-1111
/ ("V-DingIllj乍:b i"J) If the film is deformed before heat treatment, it is best to press it with light heat to correct its flatness before heat treatment.

In the present invention, /! in the same direction of the film before heat treatment. O'
G, the heat shrinkage rate for 2 hours is o, lI% no matter where it is measured.
It is more preferable to use one that has a range of deflection, preferably O, flathead. If the runout exceeds this range, the flatness of the film after heat treatment may deteriorate.

If a polyester film is charged with static electricity, the film may block, and abnormal bulges may occur in the blocking portion during heat treatment, resulting in poor flatness. As a means to solve this problem, it is preferable to use a polyester film which has been antistatically treated by a known method. For example, the antistatic agent may be polyester, A/
How to coat the film, θ, θ/-!
A method of containing heavy weight etc. is adopted.

According to the findings of the present inventors, if the temperature exceeds 730° C. when heat-treating a cut product, the flatness of the film may be extremely deteriorated. This is because polyester film has poor thermal conductivity, and the surface layer of the stacked films has a high temperature and the film shrink lid is large, but the lower film does not heat up and the film does not shrink, so the upper film does not shrink. It is presumed that this is because the lower film is deformed by the shrinking force.

Therefore, in the method of the present invention, as a method for preventing film deformation, the shrinkage rate of the film when placed in an atmosphere at Izo°C for one hour is 0.1% or less, preferably 0.5r.
Multiple sheets using polyester film below elk,
Preferably several tens to hundreds of sheets stacked /jO℃~λkoO℃
Heat treated in a furnace.

A film having a heat shrinkage rate of O, RGB or less at 150° C. for one hour can be obtained by the following method. For example, when forming a polyester film, the heat setting temperature is set between 3S℃ and λdaj℃.
The crystallinity of the polyester film is increased to t
This can be obtained by increasing the winding tension to 4t, t or more and weakening the winding tension. Also, the heat setting temperature is 2.7!
The crystallinity of the polyester film is lI below r'C
Tension of commonly used films of G to JL and J levels! rkg~10k, (//rn width 1
It can also be obtained by passing it through a hot air oven at 50°C to 30°C for several seconds to several minutes. In this method, a long continuous polyester film is heat-treated under tension, so the heat shrinkage rate cannot be reduced to a large extent, but the flatness is very good.

In addition, for films with a heat shrinkage rate of /30°C or less of o, g%, after cutting the film, lay it out at a temperature of 750°C or less, preferably at a temperature of /4Ij' (: It can also be obtained by a method of optically heat-treating the films until they all reach the same temperature. According to this method, a film with good flatness and a somewhat reduced heat shrinkage rate can be obtained.

In this way, if the flatness is improved and the heat shrinkage rate is lowered in advance, a low shrinkage film with very excellent flatness can be obtained when cut and heat treated according to the method of the present invention.

In a preferred embodiment of the method of the present invention, a polyester film obtained by heat-treating in a furnace according to the above-described method is heat-treated at a temperature Tr, and then heated to a temperature of (T, -10)°C or higher, and/or -7001°C. '4/crl preferably Ko~
Pressing or calendering is carried out at a pressure of sokg/crI. Here, TI is a temperature of 1SQ to -10°C. Also, the heat shrinkage rate at 150°C for an hour is not necessarily o, i
It is not necessary to use a film of less than By such pressing or calendering, a high quality polyester film with further improved flatness can be obtained.

Note that if heat treatment is performed while pressing from the beginning, not only will the shrinkage rate of the film not decrease, but the film will completely stick and cannot be peeled off into seven sheets one by one.

On the other hand, as described above, if the method of pressing after heat treatment is adopted, the oligomer deposited and attached to the film surface during heat treatment prevents blocking between the films, so that pressing can be performed without any problem.

When heat-treating a polyester film cut by IC as in the present invention, blocking between the films becomes a problem as described above, so in the present invention, a coating layer is provided on the film in advance in order to prevent blocking of the film. It is also an effective means to keep it.

<Examples> Hereinafter, the present invention will be further explained in A-body form by way of Examples, but the present invention is not limited to the following Examples unless the gist is exceeded.

In the examples, "part" means it part. Further, film haze and heat shrinkage were measured by the following methods.

Measurement of film haze: Using an integrating sphere type sheath density haze meter, using a standard 4c light source, incident light mcTI = 100 setting), total light transmission amount (Tm
), the amount of scattered light by the device (T, ), and the scattered light by the device and the test piece -k (T, ) are determined, and the shear haze (H) is calculated using the following formula.

Total light transmittance; Tt (%) = Axio.

T.

Scattered light transmittance; Td (%) = 1.

T(L H (chi) = 1τxio.

Measurement of heat shrinkage rate Test specimens with width (3) and length (QO) were placed in the longitudinal direction of the film.
Take a piece. The test piece is heated for a predetermined time in a hot air circulation constant temperature bath set to a predetermined temperature, taken out, rapidly cooled, and the distance between both ends is measured, read to the o and iH digits, and calculated using the following formula.

Heat shrinkage rate (俤) = trouble; 4 fallen group Shiba"L X/o
.

Measurement of Redundant Crystallinity Using a density gradient tube of a carbon tetrachloride-n-hebutane mixed system, the density was determined at 3° C., and the crystallinity was calculated using the following formula.

Crystallinity = -Voice m-Nikai-! -! -! -x i o o
(%) Waste! ! -/, JJA; The heat treatment conditions for the polyethylene terephthalate film in the following examples are as follows.

Heat treatment conditions: SOO TOMOX! 00m cut product, layered with SO sheets, placed on a 600mm x 600mm stainless steel backing plate, and set in a hot air circulation type open set at 30°C. /, t℃/mu, %fi curve to raise the temperature inside the open to 110℃ over 100 minutes, then ito℃
Hold for tyo minutes. Thereafter, the temperature inside the open chamber was lowered to 30° C. over 90 minutes, and the film was taken out.

Example: Film haze containing 200 ppm of amorphous silica, width, thickness 100μ, vertical direction /! The film was heat-treated with a yield rate of 1 at 0''C time.

Place the film directly on the stainless steel plate and heat treat it, or coat it with silicone! PI of rθμ! I
Two T films were stacked with the coated side facing inside, placed on a stainless steel plate, and the film was placed on top and heat treated. The heat-treated film obtained by silicone coating is i
Thermal shrinkage rate at zo℃ for 1 hour is 0. Although the flatness was not as excellent as that of the film before heat treatment, screen printing could be performed with high precision.

On the other hand, large bulges occurred on the entire surface of the film obtained without silicone coating, making it difficult to use.

EXAMPLE A polyester with a collection rate of Example 1/Hiro% was applied to a 7 m width under tension in a drying oven at -00'Q.
By passing it for about -θ seconds at a speed of about 7 o-m7, one lumen of polyester film with a permeation absorption rate of 0.3% at 10° C. in the vertical direction was obtained.

This polyester film was heat treated in the same manner as in Example. The heat shrinkage rate was the same as in Example/1, and a flat, soaked film was obtained.

Example J A polyester containing 00 ppm of amorphous silica was melt-extruded, stretched in the vertical and horizontal directions, and then stretched in the vertical and horizontal directions.
Heat set at 9℃ and crystallinity jj, jchi, /! 0'
A polyester film having a CJ time heat shrinkage rate of o, rch and a thickness of IOθμ was obtained. The film was heat treated in the same manner as in Example 1 to obtain a film which also had excellent flatness and a low heat shrinkage rate.

Example/In the middle of heat treatment of a polyester film not coated with silicone/e! When the temperature reached 'C, the temperature was maintained at /, j hours/das °C, and then the temperature was raised from / hiroj °C to ito °C according to a prescribed curve, and the flatness was good.
The polyester film has a heat loss rate of 0.1% or less at 50℃ for 2 hours.

/, 3 o'clock 1 = 1 / 'I j 7 of the film kept at ℃! The heat shrinkage and shrinkage rate of rO'Q for one hour was 0.3.

Example: A polyester film with poor flatness obtained by heat treatment without silicone coating was heated at 200℃/! kp/cIIt
When pressed, the flatness was improved and it became usable.

<Effects of the Invention> According to the method of the present invention, a low-shrinkage polyester film with excellent flatness can be obtained.

[Brief explanation of drawings]

FIGS. 1 and 1 each represent the edge punching of the film, and in FIG. 1, l represents the rise of the film. Applicant: Diafoil Co., Ltd. Agent: Patent attorney - 1 other person

Claims (1)

[Claims] (1) It is characterized by stacking multiple polyester films whose shrinkage rate is 0.8% or less when placed in an atmosphere at 150°C for 2 hours and heat-treating them in a furnace at 150°C to 220°C. A method for producing a low shrinkage polyester film having a shrinkage rate of 0.1% or less when placed in an atmosphere at 150°C for 2 hours.