JPS61162337A - Polyester film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a polyester film, and more particularly to a polyester film that prevents precipitation of low-molecular compounds consisting of polyester-forming components on the surface of the film. More specifically, a conductive part is provided by printing a conductive substance on at least one side of the polyester film,
The present invention relates to a polyester film suitable for manufacturing thin-film switches such as membrane switches and touch panels by subsequent heat treatment and drying.

[Prior Art] With the modernization of electrical and electronic components, switches have changed from the conventional bush type, slide type, and rotary type to membrane switches using plastic films, touch panels, and il! 1) Thin-film switches such as the Yuakei chip panel are being used. In particular, membrane switches are widely used in card calculators and the like.

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 paint, and then place the printed sides facing each other. Some methods are known, such as a method in which films are stacked and bonded together, and a method in which a circuit is printed with conductive paint, the printed surfaces are placed facing each other, and an insulating material serving as a spacer is interposed between the circuits and the circuits are bonded.

Transparent touch panels are made by first applying a transparent conductive thin film on one side of transparent polyester by vapor deposition or sputtering, and then removing unnecessary parts by etching to form a transparent circuit. It can be created by printing a functional circuit and then bonding it together in the same way as a membrane switch. Note that at this time, a transparent material such as a transparent insulation paste or a polyester film is used as the intervening insulator.

As a method of printing a conductive circuit on the surface of a polyester film, a method of screen printing a conductive paint such as silver paste is generally adopted. This method is
First, silver paste is printed and dried, and then, in order to prevent silver from oxidizing, carbon paste is further printed to cover the printed area of the silver paste to form a circuit. However, carbon paste printing is only performed when using a conductive paint that is easily oxidized, such as silver paste, and if a conductive paint that is difficult to oxidize is used, printing the paint alone is sufficient. .

Further, the screen printing method is also used when providing insulating spacers on a film on which a circuit is provided by screen printing, vapor deposition, sputtering, or the like. 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, the thin film switch manufacturing process requires heat treatment for several minutes to one hour at a temperature within the range where screen printing is performed several times. However, under such drying conditions, the film shrinks due to heating, making it difficult to print accurately from the second time onwards, or when bonding the conductive circuit parts (printed surfaces) facing each other. Sometimes it becomes difficult to bond them together with high precision.

Furthermore, a major problem that is generally known is that when heat is applied to a polyester film as described above, low-molecular compounds (hereinafter referred to as "oligomers") consisting of compounds that form polyester are formed on the surface of the polyester film. ) precipitates, significantly impairing the appearance of the film, increasing the turbidity of the film, and reducing transparency.

If a film with poor transparency is used in a thin film switch such as a membrane switch or touch panel, the appearance of the switch will be significantly impaired. Moreover, when used as a membrane switch for calculators and other devices equipped with solar cells, a portion of the film is left transparent and the transparent portion is used as a protective film for the solar cells, which prevents the film from becoming cloudy. If this happens, the negative effect of reducing the performance of the solar cell will occur.

Among the problems listed in item L, the best way to solve the problems associated with shrinkage of polyester film is to heat-treat it under almost the same conditions as drying conditions before printing to shrink it before printing. It will be done. however,
Although this method solves the problem caused by film shrinkage, it does not solve the problem that oligomers precipitate during heat treatment and the transparency of the film decreases.

As a method to improve the decrease in transparency of the film due to oligomer precipitation, a method using a polyester film with reduced oligomer content through solid phase polymerization, etc.! 11! A method of removing oligomers by extracting the film after coating with an organic solvent such as xylene, a method of heat treatment before screen printing, and wiping off the precipitated oligomers with an organic solvent such as chloroform or xylene, or ultrasonic cleaning. There are several methods of removing it, but all of these methods require complicated operations and cannot produce reliable results.

Therefore, there has been a strong desire for the development of a polyester film that does not have its transparency reduced by heat treatment.

[Means for Solving the Problems] The present invention solves the above-mentioned conventional problems, and provides thin film switches such as membrane switches and touch panels 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 suitable for use in a thin film switch, which has a conductive portion on at least one side of the polyester film, and has a conductive portion on at least one side of the polyester film. A polyester film characterized by being provided with a layer of a compound that prevents precipitation of low molecular weight compounds on the surface of the film.

The present invention will be explained in detail below.

The polyester in the polyester film of the present invention is an aromatic dibasic acid or an ester-forming derivative thereof,
A highly crystalline linear saturated polyester synthesized from diol, specifically polyethylene terephthalate,
Examples include polyethylene isophthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate. Further, it may be a copolymer in which a part of these is substituted with other components, or a blend of other resins such as polyalkylene glycol.

Therefore, polyester films, especially two-wheel stretched polyester films, are generally used to produce films containing substantially no particles and calcium carbonate, kaolin,
A film with improved blocking properties that contains inorganic particles such as silica or precipitated particles formed from the residue of the catalyst used in the reaction can be used.

However, for application to thin film switches, it is usually 12 to 250μ.
A diameter of about m is used.

In the present invention, the surface of such a polyester film, preferably the entire surface of both surfaces, is coated with a layer (hereinafter referred to as " However, if the polyester film is electrostatically charged, the compound that prevents oligomer precipitation may be repelled, resulting in an uneven coating layer.

In order to solve this problem, it is preferable to use a polyester that has been antistatically treated using a known method.As an antistatic treatment, for example, full-kyl esters such as sodium dodecylsulfonate and sodium dodecylbenzenesulfonate can be used. Examples include a method in which the polyester contains 0.01 to 5% by weight of a sulfonate.

+ II Izu+fr'+-9+ +1. Noshi seat, ^niyama b-24 = , + The above four compounds include: ■ Polymerizable organometallic compounds, ■ Heat-resistant resins with a glass transition temperature of 150°C or higher, ■ Acrylic resins, and Vinylidene Chloride Co., Ltd. Examples include, but are not limited to, amide-based resins, and amide-based resins.When forming the coating layer, these compounds 1 to 2 may be used alone or in combination of two or more. I can do it. Incidentally, specific examples of the compounds (1) to (2) will be described later.

There are no particular restrictions on the method for forming the coating layer, and any well-known method may be used as long as it can be applied thinly, but usually a compound that prevents oligomer precipitation is added in an appropriate solvent, etc. as necessary. The dissolved liquid is coated with a rod coater, gravure coater, and various roll coaters.
A method of coating is used. At this time, the coating liquid may contain an antistatic agent, type 11 agent, etc. within a range that does not impair the desired effect of the present invention, and the coating liquid may be applied to the stretched film of the two wheels. It may be applied to the surface of the film before oriented crystallization is completed, and then subjected to stretching and heat treatment. Furthermore, in the present invention, before applying the coating liquid, the polyester film may be subjected to physical treatment such as corona treatment or UV (ultraviolet) treatment, if necessary.

The thickness of the coating layer is o, oooi-t.

4 m, preferably 0.001 to 54 m. If the coating layer is thin, the effect of preventing oligomer precipitation will be low, and if it is made unnecessarily thick, it will not only be economically disadvantageous but also affect the properties of the polyester film.

In this way, the polyester film of the present invention, in which a coating layer of a compound that prevents oligomer precipitation is formed, has a change in film turbidity before and after heat treatment because the coach ink layer prevents oligomer precipitation. However, in the present invention, the film turbidity change value defined below is 2% or less, preferably 1.5% or less, more preferably 0.5% or less. desirable.

Film turbidity change value "+H+H.

If the change value of film turbidity exceeds 2%, a relatively large amount of oligomers will precipitate in the film due to heat treatment, and when used in membrane switches, touch panels, etc., the film will have a partially dusty appearance. For,
Its commercial value is low, and it is not suitable for also serving as a cover film for solar cells.

In the production of thin-film switches such as membrane switches and touch panels, the transparency itself before heat treatment of the film may be a problem due to the nature of the switch, but the polyester film of the present invention has a high turbidity, i.e. , HO in the above definition is 10% or less, preferably 6% or less.

The two-wheel stretched polyester film is made of polyester containing substantially no particles, or precipitated particles formed from inorganic particles such as calcium carbonate, kaolin, silica, and the residue of the catalyst used in the reaction, with an HO content of 10% or less. It can be obtained by sequentially biaxially stretching or simultaneous biaxially stretching a polyester containing an appropriate amount within the range.

A large amount of particles improves the blocking prevention effect, but
Ho becomes high and cannot be used as the film of the present invention.

Next, specific examples of compounds that prevent the oligomer coated in the present invention from being deposited on the film surface will be shown.

■A polymerizable organometallic compound is an organometallic compound that has at least one type of chemical bond such as a metal-carbon bond, a metal alcoholade bond, a metal acylate bond, or a metal chelate bond, and is either uncatalyzed or catalyzed. A compound that can easily form a condensation polymer after hydrolysis in the presence of metals and 1. t±, aluminum, silicon, titanium, chromium, zirconium, tin, etc., but are not necessarily limited to compounds of these metals.

Examples of organic silane compounds include tetraalkoxysilane,
Examples include trialkoxysilanes and dialkoxysilanes represented by the following formula (1) or (2), and compounds represented by the following formula (3).

R'-5i-(OR2)3 ...... (
1) (In the above formula, R1 and R2 are an alkyl group, a cycloalkyl group, a vinyl group, an alkenyl group, an aryl group, or a group in which some of the hydrogen atoms of these groups are substituted with other atoms such as halogen) group, hydroxyl group, carboxyl group, epoxy group, epoxycyclohexyl group, glycidoxy group, methacryloxy group, amino group, diamino group,
Indicates a group substituted with a reactive functional group such as a ureido group or a mercapto group. R3 is an alkyl group such as a methyl group or an ethyl group.
5. Indicates a substituted alkyl group such as a methoxyethyl group (R'
)4-n -s +-(R3) n (3
) (wherein R4 is an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, an alkoxy group such as a methoxy group or an ethoxy group, a vinyl group, a phenyl group, a methacryloxy group,
It represents a group such as a methacryloxypropyl group, and R5 represents a group such as a halogen atom, a tert-butylperoxy group, an acyl group, or an isocyanate group. n is a number from 1 to 4. Note that the number of carbon atoms in the alkyl group, cycloalkyl group, alkenyl group, and alkoxy group of R1 to R4 is preferably 10 or less.

Specific examples of these compounds include tetraethoxysilane, tetrabutoxysilane, methyltrimethoxysilane, methyltrinidoxinane, ethyltrimethoxysilane, methyltripropoxylane, phenyltrimethoxysilane, dimethyldimethoxysilane, and vinyltrimethoxysilane. Ethoxysilane, vinyl tris (β-methoxyethoxy)
Silane, γ-chloropropyltrimethoxysilane, β-
(3,4-Epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyljethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ
-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-(amineethyl)-
γ-Aminopropyltrimethoxysilane, N-β-(amineethyl)-γ-aminopropylmethyldimethoxysilane, N-(benzyl)-β-(aminoethyl)-γ-
Aminopropyltrimethoxysilane, N-β-(aminoethyl)-β-(aminoethyl)-γ-aminopropyltrimethoxysilane/, γ-ureidopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, diethyldichlorosilane , n-propyltrichlorosilane, tetraisocyanatesilane, phenyltriisocyanatesilane, triisocyanatemethoxysilane, etc., but are not limited to these.

Examples of organic titanium compounds include titanium esters, titanium acylates, and titanium chelate compounds. Specific examples include tetraisopropoxy titanium,
Tetrabutoxytitanium, Tetrakis(2-ethylhexyloxy)titanium, Diisopropoxybis(acetylacetonato)titanium, Tetrakis(2-ethylhexanediorad)titanium, Isopropoxytitanium tristearate, Impropoxytitanium tri(dioctyl phosphate) ), but are not limited to these.

Among these compounds, in particular organometallic compounds containing amine groups, such as γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-
β-(aminoethyl)-γ-aminobrobyltrimethoxysilane, N-β-(aminoethyl)-γ-7minopropylmethyldimethoxysilane, N-β-(aminoethyl)-β-(amineethyl)- Preferred are γ-7 minobrobyl trimethoxysilane, N-(benzyl)-β-(amineethyl)-γ-7 minopropyl trimethoxysilane, and the like.

In the present invention, one type or a mixture of two or more of these organometallic compounds can be used as is, partially hydrolyzed, or as a low polymer of a hydrolyzate.

■Glass transition temperature is 150℃ or higher, preferably 200℃
Examples of the above heat-resistant resins include polysulfone, polyethersulfone, polyarylate, polyphenylene sulfide, polyetherimide, polyesterimide, polyamideimide, polyimide, aramid, polybenzimidazole, polyhydantoin, etc. It is not limited.

Among these, polysulfone has -S O2- in the main chain.
It is a polymer containing groups, and aromatic polysulfone is used from the viewpoint of heat resistance. Its skeletal structure is shown by and may contain appropriate substituents.

Polyether sulfone is also a polymer containing a -502- group in its main chain, and its skeletal structure is shown by.

Polyarylate is an aromatic polyester, and the typical skeleton structure is shown below.

Polyetherimide contains an imide group and an ether group in its main chain, and a typical skeletal structure is shown below.

The polyimide resin is not particularly limited, but may include one or more compounds selected from aromatic tetrabasic acids, aromatic tribasic acids, or acid anhydrides, esters, and acid/logonides thereof; Acid anhydrides are usually used. are synthesized.

Among these, a preferred compound is a polyimide composed of an acid anhydride of an aromatic tetrabasic acid and a diamine or a diisocyanate compound, which is used to solubilize in a solvent with the aim of improving the coating properties of a coating solution during coating. , appropriately copolymerized polyimide is particularly preferred.The specific structure of these polyimide resins is represented by the following formula.

(In the formula, Rs represents a carbonyl group, an epoxy group, or a methylene group, and R7 represents an aromatic or aliphatic alicyclic divalent hydrocarbon residue.) As the resin, various resins can be used as R11 and R7 in the above formula. It may contain structural units of combinations.

In order to make polyimide soluble in solvents, relatively flexible bonds such as ether bonds, sulfide bonds, methylene bonds, and ethylene bonds are introduced into the main chain to facilitate the movement of segments. Coating can be made easier by employing methods such as reducing the rigidity of the molecule by introducing a substituent such as a methyl group or a halogen group as appropriate. When coating, the above compounds can be used alone or as a mixture of two or more.

In addition, for films provided with a coach ink layer made of a resin with a glass transition point of 150°C or higher, the films are stacked and heated at 170°C.
Even when left for 30 minutes in this state, the turbidity of the film does not increase and the film does not block at all, so it is particularly preferred when it is necessary to perform a shrinkage reduction treatment in a stacked state.

(2) Examples of acrylic resins include homopolymers and copolymers of acrylic acid and its esters, methacrylic acid and its esters, and copolymers of these monomers with vinyl compounds such as styrene and acrylonitrile. Furthermore, those having glycidyl groups, amino groups, hydroxyl groups, etc. introduced into these reactive polymers may also be used.

(2) Examples of the vinylidene chloride resin include copolymers of vinylidene and vinyl chloride or acrylic esters.

(2) Examples of the amide resin include ternary copolymers of 6.6, 6.6, and 10 nylon, and nylon obtained by converting 6,6 nylon into methylol with formalin and methoxylating with methanol.

By subjecting the polyester film of the present invention to conductive screen printing in accordance with a conventional method, it is possible to manufacture thin film switches with high transparency and good quality, such as membrane switches and touch panels.

[Action J] The polyester film of the present invention has the following properties on the surface of the film:
It is equipped with a coating layer of a compound that prevents oligomers from precipitating on the film surface, and this coating layer can effectively prevent oligomers from precipitating during heat treatment and reducing the transparency of the film. can.

[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 it exceeds the gist thereof.

In addition, in the following Examples and Comparative Examples, "part" means "part by weight". In addition, the turbidity of the film itself is Ho
shall be. The turbidity determined after being placed in an air oven controlled at 170°C for 30 minutes is designated as H+. Film turbidity is measured according to the method of ASTM D1003-61 using a Nippon Heavy Color Turbidity Meter Model NDH-2A.

Comparative Example 1 Average particle size determined by Coulter Counter method is 1°7 gm
A polyester film (hereinafter referred to as "film A") having a film turbidity Ho of 0.8% and a thickness of 100 gm was produced by melt-extruding a polyester containing 40 ppm of thyroid particles and using a conventional sequential biaxial stretching method.

This polyester film was left in an air oven at 170° C. for 30 minutes, and then the film turbidity HI was determined, and the film turbidity H1 was 3.4%. Additionally, oligomers were scattered on the surface of the film, making it white, making it unusable for membrane switches and touch panels.

Comparative Example 2 Comparative Example 1 and 18'I repair 1. 3.
A polyester film (hereinafter referred to as "film B") having a film turbidity of 4.0% and a thickness of 1004 m was manufactured using polyester containing 00 ppm of polyester.

After heat-treating this film under the same conditions as Comparative Example 1, the film turbidity H+ was determined to be 6.8%, and like Comparative Example 1, it was not in a state that could be used for membrane switches or touch panels.

Examples 1 to 3 A solution consisting of 1 part of the organosilane compound listed in Table 1, 0.1 part of water, and 29 parts of ethyl alcohol was prepared, and the solution was made to have a thickness of 0.5 parts.
Each was applied to both sides of Film A in an amount of 17 parts m.

The turbidity Ha of each film was 0.8%, and the turbidity H+ of the film after heat treatment was also 0.8%, with no increase in turbidity.

Furthermore, when the film was observed after heat treatment, no oligomer precipitation was observed.

Examples 4 to 7 A coating solution was prepared by mixing 90 parts of a heat-resistant resin with a glass transition temperature of 150°C or higher listed in Table 1 and 3910 parts of each solvent listed in Table 1. Thickness O, 14 on both sides
Each coating was applied so that the thickness was 100 m.

The turbidity HO of each film was 0.8%, and the turbidity H+ of the film after heat treatment was also 0.8%, and the turbidity did not increase. In addition, when observing the surface of the film after heat treatment,
No oligomer precipitation was observed.

Example 8 Benzophenone-3,3',4,4'-tetracarbo4
N,N-dimethylformamide/toluene = N,N-dimethylformamide solution (manufactured by Kasei Upjohn ■, 2080) of polyimide whose main component units are carbon diisocyanate and 4,4'-diphenylmethane diisocyanate. Add 773 (weight ratio) of solvent,
A coating solution containing 0.3% resin was prepared and coated on both sides of Film A to a thickness of 0.05 gm.

The turbidity (Ho and Hl) of the film before and after heat treatment is both 0.
．． 8%, and there was no increase in film turbidity due to heat treatment. When we observed the surface of the film after heat treatment, we found that
No oligomer precipitation was observed.

Example 9 The coating solution prepared in Example 8 was applied to both sides of Film B to a thickness of 0.051 part m.

The turbidity Ho of the film was 3.6%, which was lower than that of the film before coating. The turbidity H1 of this film after heat treatment was 3.6%, and no increase in turbidity was observed at all due to the heat treatment. Furthermore, when the film surface was observed, no oligomer precipitation was observed.

Example 10 A coating solution was prepared by mixing 60 parts of acrylic resin (5R-546 (trade name) manufactured by Mitsubishi Rayon ■) and 940 parts of toluene, and coated on both sides of film A to a thickness of 0.3 m. Coated.

The turbidity Ho of the obtained film and the turbidity H+ of the film after heat treatment were both 0.8%, and no increase in turbidity was observed due to heat treatment. Also.

When the surface of the film after heat treatment was observed, no oligomer precipitation was observed.

Example 11 Polyethylene terephthalate containing 300 parts of amorphous silica with an intrinsic viscosity of 0.66 and an average diameter of 1°7 JLm was
It was melt extruded at 5°C, cast onto a cooling drum at 60°C, and then stretched 3.5 times in the machine direction. On both sides of this longitudinally stretched film, an aqueous dispersion of an 8% solids emulsion of an acrylic resin containing acrylic acid, methyl methacrylate, and methacrylic acid as main components and 0.08% by weight of a fluorine-based surfactant was applied. was coated with a bar coater so that the coating amount was 4.5 g/r11'.Then, this film was stretched 3.7 times in the transverse direction at 110°C, and heat-set at 230°C. A biaxially oriented polyester film having a thickness of 100 gm was produced.

The turbidity HO of the obtained film and the turbidity H1 of the film after heat treatment were both 4.3%, and no increase in turbidity was observed due to heat treatment. Further, when the film surface after heat treatment was observed, no oligomer was observed at all.

The results of Comparative Example 1.2 and Example 1-11 are summarized in the first
As shown in Table 1, it is clear that the polyester film of the present invention does not increase film turbidity due to heat treatment and has extremely excellent transparency. teeth,
A coating layer of a compound is provided on the surface of the film to prevent oligomers from precipitating on the film surface, and this coating layer prevents oligomers from precipitating during heat treatment and reducing the transparency of the film.
Can effectively defend against IF.

Therefore, in the manufacturing process of thin film switches such as membrane switches and touch panels, even if heat treatment and drying are applied when forming conductive parts on a film by screen printing, the transparency of the film will not be impaired, and the transparent appearance will remain unchanged. This makes it possible to purchase switches with high commercial value. By the way.

Since such a polyester film of the present invention can be used as a protective film for solar cells, it is also extremely useful as a thin film switch for equipment equipped with solar cells.

Claims (6)

[Claims] (1) In a polyester film used for a thin film switch that has a conductive portion on at least one side of the polyester film, precipitation of a low-molecular compound consisting of a component forming polyester on the surface of the film is prevented. A polyester film characterized by being provided with a layer of a compound. (2) The polyester film according to claim 1, wherein the change value of film turbidity before and after heat treatment expressed by the following formula is 2% or less. Film turbidity change value = H_1 - H_0 [H_1: Turbidity of polyester film after heat treatment at 170°C for 30 minutes H_0: Turbidity of polyester film at room temperature before heat treatment] (3) Turbidity of polyester film before heat treatment is 10%
The polyester film according to claim 1 or 2, which is as follows. (4) Claims 1 to 3, characterized in that the compound that prevents the precipitation of a low-molecular compound consisting of a polyester-forming component on the film surface is a polymerizable organometallic compound. The polyester film according to any one of the items. (5) Claims 1 to 5, characterized in that the compound that prevents the precipitation of a low-molecular compound consisting of a component forming polyester on the film surface is a heat-resistant resin with a glass transition temperature of 150°C or higher. The polyester film according to any one of item 3. (6) Any one of claims 1 to 3, wherein the compound that prevents the precipitation of a low-molecular compound consisting of a component forming polyester on the film surface is an acrylic resin. The polyester film described in section.