JPS6039090B2 - Method of forming transparent conductive film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a transparent conductive coating on the surface of a polyester film.

More specifically, by heat-treating a laminated film consisting of a polyester film with a transparent thermosetting polymer layer on both sides and a coating mainly composed of a low oxide of indium metal on one or both sides, the volatility in the film can be reduced. The present invention relates to a method for forming a transparent conductive coating on the surface of a polyester film using an industrially superior method that does not easily generate substances, particularly oligomers, and has excellent adhesion to the film. For example, the following method is known as a method for producing a transparent conductive film in which a film containing indium oxide as a main component is formed on the surface of a polyester film.

{a) A transparent conductive film is formed by an ionization plating method in which an evaporation source containing metallic indium or an oxide of indium metal as a main component and a polyester film are placed facing each other, and a high-frequency discharge plasma region is formed in the space between the two. method (see, for example, Japanese Unexamined Patent Publication No. 51-116999). {b' A method in which a film containing a low oxide of indium metal as the main component is formed on the surface of a polyester film by a vacuum deposition method, and then the film is arranged to become transparent and conductive. Among these known methods, the ta} method provides a transparent conductive film with excellent adhesion to the polyester film, but the formation of the film is based on a reaction with oxygen gas introduced into a vacuum chamber. However, the film formation rate was slow.

Furthermore, the apparatus is complicated and expensive, and cannot be applied to long polyester films. Method {b} has the characteristics of a fast evaporation rate and the ability to form a film continuously even on a long polyester film, but since the film is mainly formed of a low oxide of indium metal, it requires no oxidation step. was needed. As an oxidation method, a method of oxidizing in a solution containing an oxidizing agent (Japanese Patent Application Laid-Open No. 49-365
45), a method of anodic oxidation in an electrolytic solution (for example, JP-A-49-121468, JP-A-50-187)
(Refer to Publication No. 6). Although these methods have the characteristic that a transparent conductive film can be obtained by a conventional method, they are not industrially preferred methods because the adhesion between the film and the polyester film is insufficient, and wet oxidation is used. Another method for oxidizing a film containing a low oxide of indium metal as its main component is heating and oxidizing it in an oxygen atmosphere (for example, Tokusekki Publication No. 48-55267, Japanese Patent Laid-Open No. 55-118)
0-1172) and a method of glow discharge oxidation in an oxygen atmosphere (Japanese Unexamined Patent Publication No. 51-37957) have been proposed. The transparent conductive films obtained by these thermal oxidation methods are uniform, but require high temperatures during the oxidation process, and as a result, volatile substances,
In particular, since oligomers are generated and precipitated on the polyester surface, they cannot be practically supplied as they are and require an oligomer removal process. Attempts have also been made to improve adhesion by providing an undercoat layer between the polyester film and the transparent conductive coating, but the generation of oligomers was unavoidable. Furthermore, {a) or {
When the transparent conductive film obtained by method b- is used for practical purposes, oligomers are generated when a high temperature process is involved in either the processing stage or the use stage, so that its performance cannot be fully demonstrated. As a result of research to overcome these drawbacks of the conventional method, the present inventor has developed a polyester film having a transparent thermosetting polymer layer on both sides, with a low oxide of indium metal as the main component on one or both sides of the polyester film. The present inventors have discovered that by heat-treating a laminated composite film on which a coating has been formed, a transparent conductive film in which volatile substances do not precipitate can be obtained in an industrially superior manner, and also has excellent adhesion to the coating, and has thus arrived at the present invention. It is something.

That is, the present invention provides a laminated polyester film in which a transparent thermosetting polymer layer is provided on both sides of a polyester film, and a coating mainly composed of a low oxide of indium metal is formed on at least one side of the polymer layer. This method of forming a transparent conductive coating is characterized in that a film is heat-treated at a temperature that satisfies the softening point of the polyester film.

As the polyester film serving as the base material of the transparent conductive film of the present invention, for example, a film made of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, etc. is preferably used.

These films are produced by a melt extrusion method, a calendering method, a casting method, etc., but in addition to these polyesters, various stabilizers and additives may be mixed as necessary. Furthermore, it may be a composite film in which polyester and one or more other polymer films are competitively layered, or a copolymer or blend type film of polyester and other polymers. Further, a polyester film subjected to stretching processing, particularly biaxial stretching processing, is particularly preferable because it has excellent mechanical properties, thermal properties, optical properties, and dimensional stability. Further, the polyester film may be subjected to physical or chemical surface modification treatments such as corona treatment, matting treatment, steam treatment, alkali treatment, etc., or may be provided with a surface modification layer, if necessary. Furthermore, there is no problem even if characters, figures, patterns, etc. are drawn on the surface. Transparent thermosetting polymers used in the present invention include, for example, xylene resins, melamine resins, sulfonamide resins, alkyds, epoxy resins, unsaturated polyester resins, or organometallic compounds, among which silicon, titanium, aluminum Particularly preferred are organometallic compounds containing metals such as.

As the organometallic compound, for example, a metal halide represented by the general formula M (where M is a metal, X is a halogen, and m and n are positive integers) is easily decomposed and heated. As a result, it is cured to form a polymer film. Examples of such metal halides include TIC14, AI
C13, ZrC! 4, Inc14, etc. Also, the general formula M20mRn (where M is a metal, R is an alkyl group, 1
, m and n are positive integers) are also used. Further, silicon-containing organometallic compounds represented by the following general formula are particularly preferred. [However, R, (R5 and R6 are hydrogen or an alkyl group having 1 to 4 carbon atoms), an alkylol compound thereof, a polyamino group, 1-SH, 1-CI, and R2 are hydrogen or an alkyl group having 1 to 4 carbon atoms.
12 alkyl groups; R3 and R4 are alkyl groups having 1 to 4 carbon atoms; x and y are each integers of 1 to 12; w is an integer of 0 to 2; z is an integer of 1 to 3, satisfying w+z=3 .

] Furthermore, the general formula RnSiXm (where R is an organic group such as methyl, ethyl, propyl, butyl, vinyl, phenyl, methacryloxy, methacryloxypropyrel; X is a halogen group; n is a halogen group, an alkoxy group, or an acyl group;
, m is an integer of 0 to 4, satisfying n+m=4).There are prepolymers obtained by hydrolyzing one or more of the following. The thermosetting polymer may be used alone or in combination with two or more types of thermosetting polymers, if necessary.
The composition is further dissolved in a solvent along with additives such as curing catalysts, adhesion promoters, wettability improvers, plasticizers, stabilizers, antioxidants, lubricants, antifoaming agents, thickeners, and pigments, as required. It can be done. In order to obtain the transparent conductive film of the present invention, a thermosetting polymer layer is first formed on the surface of a polyester film. The polymer layer may be a single layer or a multilayer. It may also be a blend of two or more types of thermosetting polymers. The first polymer layer may be provided on only one side of the polyester film, or may be provided on both sides. When installing on both sides,
The same polymer layer may be formed on both sides, or different types of polymer layers may be formed on both sides. The thickness of the polymer layer is not particularly limited, but is preferably in the range of 0.01 mm to 10 mm. If the thickness is less than 0.01 mm, it is difficult to achieve the desired goal because a continuous film will not be formed. Moreover, if the thickness exceeds 10 mm, the polyester film will lose its flexibility and properties, and cracks will appear on the surface, which is undesirable. Depending on its shape and properties, the thermosetting polymer layer can be applied using a known coating machine such as a doctor knife, bar coater, gravure roll coater, curtain coater, knife coater, or spinner, a spray method, or an immersion method. laws etc. are used.

Polyester film coated with thermosetting polymer is
The solvent must be allowed to evaporate and the material must be dried or cured. For drying and curing, the temperature and time should be selected so that problems such as blocking do not occur when the polyester films are stacked or rolled. Note that the thermosetting polymer layer does not need to be completely cured, and may be only partially cured. When a thermosetting polymer is coated on both sides of a polyester film, the temperature required for drying and/or curing is the lower of the heat resistance temperature of the thermosetting polymer or the softening point temperature of the polyester film. Must be below temperature. Note that the lower limit of the heat treatment temperature is about 2500°C. If it is coated on only one side, it is necessary to select a temperature and time that will not generate polyester oligomers.For example, in the case of polyethylene terephthalate, generally 1
The temperature is preferably 90°C or lower. A coating mainly composed of a low oxide of indium metal is formed on the polyester film on which the thermosetting polymer layer is formed, but the coating must be formed on the thermosetting polymer layer.

The low oxide of indium metal used in the present invention is represented by the general formula lny0y (where o<y/x<1.5). The film mainly composed of a low oxide of indium metal is produced by vacuum vapor deposition of indium oxide or a mixture of indium oxide mixed with a metal oxide such as tin oxide, cadmium oxide, tungsten oxide, or molybdenum oxide.
It is formed by methods such as ion plating, sputtering, plasma vapor phase plating, chemical plating, electroplating, chemical coating, and combinations thereof.
Among these methods, the vacuum evaporation method is particularly suitable from the viewpoint of uniformity of the formed film and ease of production. At this time, the thickness of the coating mainly composed of a low oxide of indium metal cannot be uniformly determined because it is related to the conductivity and transparency of the transparent conductive film, the temperature and time of the oxidation treatment, etc. However, the upper limit is thought to be approximately 3000A based on the oxidation rate at the heat-resistant temperature of the polyester film, but the upper limit is approximately 3000A due to the ease of oxidation.
From the viewpoint of the transparency of the resulting film, a value of A or less is preferably 500Δ or less. On the other hand, the lower limit thereof is preferably a thickness that allows the transparent conductive thickness to impart conductivity, and is suitably 50 Δ or more. In the method of the present invention, a thermosetting polymer layer is formed on a polyester film, a film containing a low oxide of indium metal as a main component is formed thereon, and then heat treated to form a transparent conductive film.

The heat treatment is a method of heat curing the thermosetting polymer layer at a temperature below the heat resistance temperature of the polyester film having the thermosetting polymer layer, and/or oxidizing the film whose main component is a low oxide of indium metal in an oxidizing atmosphere. It is. An oxidizing atmosphere is an atmosphere necessary to carry out the above oxidizing action, and includes air,
It is made of oxygen gas or activated by ultraviolet irradiation, discharge, etc., and it is preferable that at least the oxygen component is contained in an i-string capacity % or more. Generally, the more oxygen gas components there are, and the more activated it is, the lower the temperature and the shorter time required for the oxidation. The required temperature and time are the heat resistance temperature of the polyester film having the thermosetting polymer layer, the curing temperature and time of the thermosetting polymer, and the factors that determine the desired properties - namely, the low oxide of indium metal. It varies depending on the composition of the main component layer (degree of oxidation, type and amount of additives, etc.), thickness and composition, or the desired conductivity and transparency. In the method of the present invention, a polyester film having a transparent thermosetting polymer layer on both sides is coated with a film containing a low oxide of indium metal as a main component on one or both sides of the polyester film. A transparent conductive film is formed by heat treatment at high temperatures, but
An example of the specific procedure is shown in Table 1.

Table 1 Procedure for forming transparent conductive film Note (1) Numbers indicate the order of the steps.

(0) The same number indicates that the steps are performed simultaneously in the same process.

(m) 1' means to perform after 1 or at the same time as 1. The same applies to 2' and 2, 3' and 3, and 4' and 4.

(N)') indicates the case where both sides are made transparent and conductive, and is omitted when only one side is made transparent and conductive. In Table 1, side A and side B indicate the respective sides of both sides of the polyester film. In each of the steps in Table 1, for example, method A involves coating a thermosetting polymer layer on both sides of a polyester film (1 and 1'), and then applying a coating containing a low oxide of indium metal as the main component. (2 or 2 and 2') and heat-treated to oxidize the coating film and at the same time harden the thermosetting polymer layer (3 or 3 and 3')
represents something. In addition to the methods in Table 1, for example, in the method of
This should be done after 3 rounds of heat treatment (i.e. {2}
→4, '3}→5) is also possible, and other methods are also obvious. In any case, according to the method of the present invention, it is preferable that both surfaces of the polyester film be coated with a thermosetting polymer before the heat treatment step. Among the methods listed in Table 1, in methods A, B, and C, the polyester film is not exposed on the surface even when the thermosetting polymer is heat-cured, so even if the heat-curing temperature is sufficiently high, the oligo This is a preferable method as it does not cause The method of Zarani and Ro is particularly preferred because it requires fewer steps. Furthermore, this method requires fewer steps because the thermosetting polymer and the oxidation of the layer mainly composed of a low oxide of indium metal can be simultaneously performed by heat treatment, and the adhesion between the two layers is also extremely good. ing. It is thought that the adhesion is improved by some kind of chemical bond between the two layers when they are cured and oxidized, but the reason for this is not clear. A polyester film having a transparent conductive coating formed by the method of the present invention does not generate oligomers even at high temperatures.

The polyester film having a transparent conductive coating obtained according to the present invention can be used to apply the interaction between light and lightning fields, such as collective light emitting devices, photoelectric conversion devices, facsimile recording bodies, EL displays, and substrates for electrophotography. However, they do not generate oligomers even when exposed to high temperatures during their production. Furthermore, condensation and
Even when used as a heating element for freezing prevention, oligomers are not generated. Furthermore, the transparent conductive film obtained according to the present invention is also used for antistatic purposes, such as cathode ray tubes of televisions, windows of indicating instruments, and work mats. It can also be used for quick start of fluorescent lamps or as a selective light transmission film. The present invention will be explained below with reference to Examples.

Example 1 A silica sol solution of an alcoholic solvent containing ethyl silicate as a main component (manufactured by Nippon Alcoat Chemical Co., Ltd.; H
AS-2) was applied with a gravure coater, 135q0,
9. The inkstone sand was dried to obtain a coating film with a thickness of about 0.1 mm.

When the surface was gently wiped, the coating peeled off, was soluble in alcohol solvents, and remained uncured. A mixture of indium oxide and tin oxide in an amount of 7.5% by weight was vacuum deposited onto the film. The obtained film is a low oxide of indium metal, and is a black conductive film having a thickness of 350 Å, a surface resistance of 5 KQ', and a transmittance of about 40% for 60 nm of light. The film was heat treated under biaxial tension at 180 oo for 1 hour. The obtained film had a surface resistance of 4000/c current, a light transmittance of about 89% at 60°C, and no oligomers were observed at all. Furthermore, the results of the stripping test using Scotch tape were also perfect. Comparative Example 1 A biaxially oriented polyester film sheet having a thickness of 75 mm was subjected to vacuum deposition and heat treatment in the same manner as in Example 1.

The obtained transparent conductive film contained oligomers and looked like frosted glass. Furthermore, the adhesion between the conductive coating and the film was also extremely poor. Example 2 A 5% normal hexane solution of tetrabutyl titanate was coated on both sides of a 75 mm thick double-stretched polyethylene terephthalate film using a bar coater, and then air-dried at room temperature.

The obtained film was subjected to vacuum deposition and heat treatment in the same manner as in Example 1, but no oligomers were observed at all. Example 3 A curable polymer layer was made of ethyl silicate and glass resin (
The same experiment as in Example 1 was carried out using the mixture of Owen Sirinoy Co., Ltd., but no oligomers were observed.

Example 4 A polyester film coated with a thermosetting polymer was heated at 180°C under the same conditions as Examples 1, 2, and 3.
Although it was thermally cured for 20 minutes, no oligomers were generated at all.

A film mainly composed of a low oxide of indium metal was formed on the film using the same vacuum evaporation method as in Example 1, and 18
000, and heat treated for 1 hour to form a transparent conductive film. The obtained transparent conductive film did not contain any oligomers. Furthermore, the adhesion between the film and the polymer layer before heat treatment was good, and the results of the cross-cut test were also 100% perfect. Example 5 The transparent conductive films of Examples 1, 2, 3, and 4 were
No olicomer was generated even if the product was left in a hot air dryer at 0oo for 2 hours.

Claims (1)

[Claims] 1. A laminated polyester film in which a transparent thermosetting polymer layer is provided on both sides of the polyester film, but a coating mainly composed of a low oxide of indium metal is formed on at least one side of the polymer layer. A method for forming a transparent conductive film, characterized by heat treatment at a temperature below the softening point of a polyester film.