JPS58169707A - Transparent conductive 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 The present invention relates to a transparent conductive film mainly composed of an indium oxide film and tin oxide formed on the surface of a plastic substrate.

In general, thin films that are transparent in the visible light range and have conductivity are used not only as transparent electrodes in new display systems such as liquid crystal displays, electrochromic displays, and electroluminescent displays, but also for antistatic purposes in transparent articles, rapid cutting of electromagnetic waves, etc. is used for.

Hitherto, as such transparent conductive films, films formed by forming a stannic oxide film, an indium oxide film, or the like on glass are known. However, since the base material of this type of membrane is glass, it is inferior in flexibility and workability, and is therefore undesirable depending on the application. Therefore, in recent years, transparent conductive films based on plastic have been in the spotlight as they are superior in terms of flexibility, processability, impact resistance, weight, etc.

However, since the plastic base material of such a transparent conductive film has poor heat resistance, it has not been possible to use the same manufacturing method as that for a transparent conductive film using glass as a base material.

The conventional method using glass as a base material is to spray a hydrochloric acid solution of tin tetrachloride onto glass that has been heated to a high temperature of several hundred degrees, and then perform oxidation treatment at high temperatures to form a thin film made of tin oxide. This is the way to do it. Recently, a method of using indium oxide as an evaporation source and heating it to about 300°G to 350°C under vacuum evaporation under high vacuum of about 10 to 1 O-5 H2 on the 4 lath has also become known. It is being

As is clear, both methods require the glass substrate to be heated to a high temperature. This also applies to other known methods in which water vapor or a gas containing water vapor is introduced into the system during the vacuum deposition described above. Although this method aims to obtain a conductive film with low resistance, for example, 100 Ω/cj or less, it is still necessary to heat the glass substrate to 300° C. to 3500° C.

As described above, all of the conventional methods using glass as a base material require heating the base material to a high temperature, and without this, the desired conductive film could not be formed. Therefore, these methods were rejected due to their inferior heat resistance.

Various improved methods have been proposed to date to overcome this problem. Most of these proposed methods utilize vacuum evaporation methods, and can generally be divided into those using indium oxide as the main evaporation source and those using metallic indium as the main evaporation source.

The former method using indium oxide as the evaporation source was developed in
As seen in Japanese Patent Publication No. 1-35431 and Japanese Patent Publication No. 51-37667, when indium oxide is vapor-deposited onto a plastic substrate, the substrate is not heated at all or the temperature is moderate enough to be tolerated by the plastic substrate. Do not heat to
X10-4~1×10!5. Vacuum deposition is performed under a high vacuum of about .

However, this proposed method requires considerably harsh conditions for oxidation treatment after vacuum deposition. For example, when heat treatment is performed in air, the optimum temperature for practical use is usually 2006C.
to 250'C or more. The purpose of the oxidation treatment is to convert indium oxide into a higher order oxide since it decomposes into lower order oxides during vacuum evaporation, but under the harsh conditions mentioned above, the plastic base used Naturally, there are limitations depending on the material.

Moreover, according to this method, since the evaporation source is an oxide, the heating temperature of the evaporation source is 1300°C or higher, usually 1500°C to 21°C.
The temperature must be as high as 00°C. As a result, a specially treated and expensive crucible is required as a container for the evaporation source. Furthermore, at the generally applied distance between the evaporation source and the plastic substrate, there is a high risk that the plastic substrate will be heated to high temperatures by radiation, and this also limits the plastic substrates that can be used. I end up.

On the other hand, the latter method using metallic indium as an evaporation source generally involves introducing an oxidizing gas into the vacuum system to
10→1IIIH1) This method attempts to vacuum evaporate metallic indium onto a plastic substrate while converting it into its oxide at a relatively low degree of vacuum. For example, Japanese Patent Publication No. 40-14304 discloses that during the above-mentioned vacuum evaporation, the plastic substrate is heated at 100°C or higher, usually at 110°C to 10°C.
A method is disclosed that aids in the conversion of metallic indium to an oxide by heating to temperatures on the order of 50°C.

Furthermore, Japanese Patent Publication No. 43-8137 discloses that in similar vacuum evaporation, the evaporation rate is set at a high rate of 16 A/sec or higher, usually 150 λ/sec or higher to reduce the thickness of the evaporated film, while converting metallic indium into an oxide. A method is disclosed in which a step of heat treatment at a temperature of generally around 100° C. for several hours is added after vacuum deposition to accelerate the deposition.

As is clear, in these methods, the plastic substrate is not heated at all or is only heated to a relatively low temperature, and the heating of the evaporation source is also low, so that it can be said that only a small amount of heat is received from the evaporation source by radiation. . Furthermore, even when heat treatment is performed after vacuum deposition, the temperature is sufficiently permissible for various plastic substrates.

As described above, the method using metallic indium as an evaporation source has the great advantage of being almost unrestricted by the plastic substrate used, and can be said to be a desirable method as an industrial method for producing transparent conductive films.

However, despite these advantages, the conductive film obtained by this method has the disadvantage that its film properties and transparency are not sufficiently satisfactory.

For example, when examining the visible light transmittance at 5QQnm of a conductive film obtained according to the method described in Japanese Patent Publication No. 40-14304, it was found that even a thin film could only obtain a transmittance of about 30%. Ta. Furthermore, in the method described in Japanese Patent Publication No. 43-8137, the transparency can be improved to some extent by adding changes such as making the oxidation treatment conditions more severe. For example, when the visible light transmittance is set to about 1000λ or more, the maximum visible light transmittance is about 80%, and no material showing a transmittance higher than this was obtained.

Therefore, the inventors conducted extensive research on methods for improving transparency without impairing the above-mentioned advantages of vacuum evaporation using metallic indium as an evaporation source.
3-8137, in which vacuum deposition is performed in an oxidizing gas atmosphere and then further oxidation treatment is performed, rather than using oxygen gas alone as the oxidizing gas, oxygen gas and nitrogen, It has been found that it is more desirable to use a mixed gas consisting of an inert gas such as argon gas to improve transparency.

Also, when performing vacuum deposition in such an oxidizing gas atmosphere, if an appropriate amount of water vapor is included in the vacuum system,
It has been found that the transparency of the deposited film is significantly improved when oxidation treatment is performed after vacuum deposition. The researchers discovered the surprising fact that this method allows for milder oxidation treatment conditions and that high transparency can be obtained even when the film is thick.

This is an extremely important fact, and the position could not be predicted using conventional preconceptions. That is, in general vacuum evaporation methods, the presence of water vapor in the vacuum system is believed to be detrimental to the formation of a uniform, high-quality deposited film, and efforts have been made to eliminate it. Of course, as mentioned above, when forming a vapor deposited film of indium oxide or the like on a glass plate heated to a high temperature, there has been a proposal to introduce water vapor into the vacuum system in order to make the surface resistance of the vapor deposited film extremely low. There is. However, even in this case, it was thought that introducing water vapor would impair the transparency of the membrane.

In this way, the inventors succeeded in greatly improving transparency by using a mixed gas consisting of oxygen gas and an inert gas as the oxidizing gas, and by incorporating water vapor into this oxidizing gas. .

However, another problem with the above-mentioned conventional method is that the resulting transparent conductive film has poor resistance stability, and the surface resistance tends to increase significantly when left in air for a long time. This tendency was similarly observed in the above-mentioned improved method by the present inventors.

For example, when a transparent conductive film with a thickness of 30 OA obtained by vacuum-depositing water vapor in a mixed gas and then oxidation treatment is left in the air (in a dark room), the change over time is as follows:
The curves in the figure are as shown. As is clear, after 240 hours, the value was about 1.7 times the initial value, and 6
After 00 hours, it increases to about 2.2 times or more of the initial value, and shows a tendency to increase thereafter.

Such materials with poor resistance stability pose a serious problem when applied to applications that require a constant resistance value, such as transparent electrodes and heaters.

In the course of subsequent research to improve such resistance stability, the inventors added a specific amount of metallic tin to metallic indium as an evaporation source, and vacuum-deposited and oxidized it in the same manner as described above, thereby converting both metals. When a specific vacuum evaporation means is added to obtain a transparent conductive film made of an oxide, the weight ratio of metal tin to metal indium constituting the oxide changes continuously in the thickness direction so that the film is coated on the outer surface of the film. It has been found that a conductive film is formed that is high and low on the inner surface of the film, and that this gives significantly good results in resistance stability.

Conventionally, it has been known that when a transparent conductive film made of indium oxide contains a very small amount of tin oxide, the surface resistance decreases. However, a transparent conductive film having a structure in which the metal ratio differs in the thickness direction as described above is not known, and the relationship between such a structure and resistance stability has not been completely elucidated.

Therefore, an object of the present invention is to provide a transparent conductive film having such a novel structure. That is, the transparent conductive film of the present invention is composed of an oxide of 60 to 95% by weight of metallic indium and 40 to 5% by weight of metallic tin formed on the surface of a plastic substrate, and The weight ratio of metallic tin to metallic indium (hereinafter simply referred to as the Sn/In ratio) is continuously varied in the film thickness direction by 1:N8, and the Sn/In ratio on the inner surface of the film is adjusted to the average of the entire layer. It is characterized in that the ratio (Sn/In ratio) is significantly lower than the ratio (Sn/In ratio), and the Sn/In ratio on the outer surface side of the film is comfortably higher than the average ratio of the entire layer.

Figures 1 and 2 show changes in the Sn/ln ratio in the film thickness direction for two types of transparent conductive films of the present invention, with the Sn/In ratio on the vertical axis and the film thickness It is expressed on the horizontal axis. In each case, the film thickness was 300%, and Figure 1 shows 90% by weight of metallic indium obtained by the method of Example 2 described later.
Figure 2 shows a transparent conductive film made of an oxide of 60% by weight of metallic indium and 40% by weight of metallic tin obtained by the method of Example 4 described later. Each represents a conductive film. Furthermore, the positions of dotted lines in both figures represent the average S n/I n ratio of the entire layer.

As can be seen from these figures, there are considerable differences in the degree of S n / I n ratio on the inner surface side of the membrane and on the outer surface side of the membrane and the change curve in the thickness direction depending on the embodiment, but this difference is particularly important in this invention. What is important is that the S n/l n ratio continuously changes in the film thickness direction, and that the inner surface of the film is significantly lower than the average ratio of the entire layer (resulting in a high concentration). While constituting an indium oxide layer, the outer surface of the film is considerably higher than the average ratio of the entire layer and constitutes a highly concentrated tin oxide layer.

FIG. 3 shows the resistance stability of the transparent conductive film of the present invention having such a structure, where fLo (initial resistance value)/
The vertical axis represents RE (resistance value after aging) and the horizontal axis represents the time of exposure in air (dark room). Curve in the figure -
2 is made of an oxide of 80% by weight of metallic indium and 20% by weight of metallic tin obtained by the method of Example 4 described later, and the film thickness is aooX and the change in the S n/1 n ratio in the thickness direction is shown in Figure 1. The transparent conductive film of the present invention having a structure close to
b indicates a transparent conductive film made of indium oxide alone obtained in Comparative Example 1 described later.

As is clear from this figure, in the transparent conductive film of the present invention, the surface resistance after 240 hours is suppressed to about 1.2 times the initial value, and after that it remains stable and hardly increases. . The reason for this is that Sn/
Since the In ratio is significantly higher than the normal -/In ratio of the entire layer and constitutes a high concentration tin oxide layer,
This is believed to be because this outer layer acts as a barrier layer against resistance changes due to oxidation.

In this way, the transparent conductive film of the present invention provides high resistance stability, but another effect is that tin oxide can be removed completely (
It also has the effect of improving chemical resistance and abrasion resistance compared to those in which it is not included or is uniformly included in the film. This is also due to the fact that the outer layer is composed of a highly concentrated tin oxide layer. Note that such effects such as resistance stability can be expected even when a complete two-layer structure of an indium oxide layer and a tin oxide layer is used.

On the other hand, even though the outer layer is made of a highly concentrated tin oxide layer and the inner layer is made of a highly concentrated indium oxide layer, the S n/I n ratio changes continuously in the film thickness direction. In other words, even if the concentration difference is small, the entire layer contains tin oxide, so either it does not contain tin oxide at all, or it has a complete two-layer structure of indium oxide and tin oxide. It has the advantage that the initial surface resistance of the entire film is considerably lower (compared to those with a completely double-layer structure), and it also has the advantage of not causing the problem of delamination that occurs with completely two-layer structures. There is.

In the transparent conductive film of this invention, the weight ratio of metallic indium and metallic tin in the entire film constituting the oxide is 60%.
The reason why the content is set to 95% by weight and the latter 40 to 5% by weight is as follows. In other words, the higher the proportion of metallic tin, the better the resistance stability (but on the other hand, there is a tendency for the transparency of the film to decrease and the initial resistance value to increase; conversely, as the proportion of metallic tin increases) This is because if the ratio of metallic indium and metallic tin is set within the above range, the effect of improving resistance stability, chemical resistance, or wear resistance cannot be sufficiently obtained. Good results can be obtained in all of the above-mentioned properties when the metal indium is set to 65 to 90% by weight 1, .'11 and the metal tin is set to 35 to 10% by weight.

Next, a method for manufacturing the transparent conductive film of the present invention having such a structure will be explained.

The inventors have proposed such a method that metal indium 6
Using an evaporation source consisting of 0 to 95 stacked tin and 40 to 5% by weight of metal tin, set the amount necessary to obtain a predetermined film thickness in an evaporation source container, and then add oxygen gas to the evaporation source. At least metallic indium is evaporated in an oxidizing gas atmosphere consisting of a mixed gas with an inert gas, and vacuum evaporated onto the plastic substrate so that the evaporation rate remains constant throughout through an initial heating step and a subsequent temperature raising heating step. , a first production method characterized by further performing an oxidation treatment on the deposited film formed by this vacuum deposition, and a second production method characterized by including water vapor in the above-mentioned mixed gas in this production method. It has been found that the production method is suitable for and.

In other words, in these methods, metallic indium and metallic tin are first vacuum-deposited in an oxidizing gas atmosphere using metallic indium and metallic tin as evaporation sources, and then further oxidized.
Compared to methods using indium oxide and tin oxide as evaporation sources, this method has advantages such as not being limited by the material of the plastic base material and being able to heat the evaporation source at a relatively low temperature.

Furthermore, according to these methods, when vacuum evaporating metallic indium and metallic tin, Sn/tin can be formed by a simple operation of gradually raising the temperature from a preset initial heating temperature by utilizing the difference in vapor pressure between the two metals. Since it is possible to obtain a transparent conductive film having the above-described structure in which the In ratio changes in the thickness direction, industrially difficult vapor deposition techniques are not required.

In other words, when heating the evaporation source, first set an initial heating temperature corresponding to a predetermined evaporation rate and heat it for a certain period of time.Since the vapor pressure of metallic indium is considerably higher than that of metallic tin, the surface of the plastic base material An oxide mainly consisting of metallic indium is deposited on the surface. If this initial heating temperature is maintained as it is, the deposition rate will decrease as the metal indium evaporates, but if the temperature is gradually increased so that the deposition rate remains constant, the The amount of tin evaporated increases and finally an oxide mainly consisting of metallic tin is deposited.

The change in the S n/l n ratio achieved in this way in the thickness direction is typically as shown in FIG. Although Fig. 2 shows the same changes as above, S
The n/I n ratio reaches the -H peak and then decreases. This is because in the heating operation described above, depending on the vapor deposition conditions, some of the metallic indium and metallic tin are converted into oxides with low vapor pressure by the oxidizing gas before evaporating, and this evaporates in the latter stages of heating. Seem.

Next, in the first manufacturing method, a mixed gas of oxygen gas and inert gas is used as the oxidizing gas, which has the effect of lowering the initial surface resistance compared to when oxygen gas is used alone. There is. In other words, according to the transparent conductive film of the present invention in which the S n/I n ratio changes in the thickness direction, as mentioned earlier, indium oxide alone However, this surface resistance can be further reduced (to about X) by using a mixed gas. In addition, when such a mixed gas is used, the transparency of the conductive film obtained is improved compared to when oxygen gas is used alone, and when making a relatively thin film of about 500 8 or less, the visible light transmittance of □QQnm is increased. 80%
or more.

Further, when water vapor is further included in the above-mentioned mixed gas by the second production method, the initial surface resistance of the resulting transparent conductive film is further reduced, and the transparency is further improved. In particular, with regard to transparency, even when the oxidation treatment conditions are very mild compared to the first production method, the same or higher transparency can be obtained, and the film thickness is 2.
It has the advantage that a visible light transmittance of 80 qb or more can be obtained even when the thickness is about 000 λ.

Below, the method for manufacturing the transparent conductive film of the present invention, which is comprised of the first and second manufacturing methods, will be described in detail.

From a thermal standpoint, there are almost no restrictions on the material of the plastic base material used in this invention. As will be described later, the plastic base material becomes 15% during vacuum deposition.
This is because the evaporation source is not heated to a temperature higher than 0.6C, and since the evaporation source is metal indium and metal tin, there is little radiant heat from the evaporation source, and the oxidation treatment can be performed under relatively hidden conditions.

Therefore, in this invention, any of the various conventionally known plastics can be used. Specific examples include polyester, polyamide, polypropylene, polycarbonate, polyimide, polyparabanic acid, polyamideimide, polybenzimidazole, triacetate, polyacrylic, cellulose resin, and fluororesin. When these plastics are used as base materials, they can be appropriately used as sheets, films, and other molded products.

In addition, these plastic substrates are processed by vacuum deposition prior to vacuum deposition.
Dust is removed and cleaned by solvent cleaning, ultrasonic cleaning, etc., and if necessary, an undercoat layer or surface treatment can be applied to improve the adhesion and abrasion resistance between the deposited film and the plastic substrate. .

Formation of the coating layer is also effective for alleviating strain between the base material and the deposited film during the oxidation treatment process.

To form an undercoat layer, a resin coating such as an organic solvent type, emulsion type, or non-solvent type is usually prepared and coated to a predetermined thickness on the plastic substrate to be used, and then heated, cured at room temperature, or cured at room temperature. It may be dried by an appropriate means such as electron beam or ultraviolet irradiation.

The resins used here include a wide range of known resins such as epoxy resins, polyester resins, urethane resins, alkyd resins, vinyl chloride-vinyl acetate copolymer resins, and acrylic resins.

Further, as a coating method, methods such as gravure roll coating, Meyer bar coating, doctor blade coating, reverse roll coating, dip coating, air knife coating, kiss coating, nip coating, and fountain coating are employed.

Examples of methods for surface treatment include corona discharge treatment, fire treatment, sputtering treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, chemical conversion treatment, and oxidizing agent treatment. These surface treatments are effective means for improving the adhesion between the plastic substrate and the deposited film.

The evaporation sources used in this invention are metal indium and metal tin, and in some cases, the above metals include cadmium,
Small dopings of other metals such as molybdenum can also be used. The ratio of metallic indium and metallic tin is 60 to 95% by weight for the former, 40 to 5% by weight for the latter,
and (preferably the former is 65 to 90% by weight and the latter is 35 to 90% by weight)
The amount is 10% by weight, and the reason for this is as described above.

Note that these metals may be made into an alloy from the beginning or may be used as a single metal. Further, the shape is not particularly limited, and any shape such as a rod, a film-like granule, or a powder can be used.

In the present invention, when such an evaporation source is vacuum-deposited on the plastic substrate mentioned above in an atmosphere consisting of an oxidizing gas, a mixed gas consisting of oxygen gas and an inert gas is used as the oxidizing gas. .

Typical inert gases include nitrogen gas and argon gas. These inert gases may be used alone, both gases may be used together, or other inert gases such as xenon and krypton may be mixed.

It has been found that the mixing ratio of such an inert gas and oxygen gas greatly influences the characteristics, particularly the transparency, of the resulting transparent conductive film.

A generally applicable and desirable mixing ratio for improving transparency is one in which the proportion of inert gas in the mixed gas is approximately the same as the proportion of inert gas contained in air (approximately 78 to 80% by volume). It is better to make it happen. This typical gas mixture is air containing nitrogen gas as the primary inert gas. Using such air can be carried out industrially advantageously.

The proportion of inert gas in the mixed gas can be greater than the proportion of inert gas contained in air, but in this case only when water vapor is included in the mixed gas, and at most about 86 The volume should be less than 83 cm, preferably less than 83 cm. If there are too many more than this,
This results in a loss of transparency. By increasing the proportion of inert gas in this manner, it is possible to suppress oxidative deterioration of the boat and exhaust system during vacuum evaporation, and the surface resistance can be further reduced. This leads to the benefits of including water vapor.

The proportion of inert gas in the mixed gas can also be lower than the proportion of inert gas contained in air;
It should be larger than the volume. If it is less than this (too much), no effect of improving transparency or reducing surface resistance will be observed in any case.

Next, in order to include water vapor in such a mixed gas in the second production method, the mixed gas may be passed through a water tank or a constant humidity atmosphere. Of course, other humidification means can also be used. The amount of water vapor is approximately 30% relative humidity of the mixed gas.
The above is preferably about 70% or more. If the relative humidity is too low, little effect on improving transparency or reducing surface resistance can be expected.

According to the vacuum evaporation method of the present invention, first, the amount of evaporation source necessary to obtain a predetermined film thickness is set in the evaporation source container in the evaporation apparatus such as a bell jar, and the inside of the apparatus is preliminarily filled with 1O-51.
A high vacuum of about IlIHy is created, and then the above-mentioned mixed gas or humidified mixed gas is introduced to adjust the degree of vacuum to an appropriate degree. The degree of vacuum greatly affects the characteristics of the transparent conductive film obtained, and the optimal degree of vacuum varies depending on whether humidified gas or dry gas is used, so it must be determined appropriately for each case. For example, when using humidifying gas, the most suitable degree of vacuum is to set the atmospheric pressure inside the device to 9 x 10-2 to 5 x 10-31 mH1.Generally, if the degree of vacuum becomes too low, , especially when the degree of vacuum is lower than I x 10"waHfl,
The evaporation source is quickly oxidized, which tends to impede the vapor deposition operation, and also reduces the vapor deposition efficiency. In addition, the surface of the deposited film becomes uneven, making it impossible to obtain a transparent film even if oxidation treatment is performed afterwards (on the other hand, if the degree of vacuum is too high (too much is undesirable), in a high vacuum system, oxidation treatment No significant improvement in transparency will be observed.

Next, under such a moderate degree of vacuum, the evaporation source is evaporated and deposited on the plastic substrate by appropriate means such as resistance heating, electron beam, induction heating, etc. At this time, a preset evaporation rate is set. The initial heating step is to set an initial heating temperature that can evaporate at least metallic indium and heat it for a certain period of time so that at least metal indium can be evaporated. Assign a process number.

The deposition rate to be set is generally determined from the viewpoint of transparency).
Although it is in the range of 6λ/sec, the optimum speed when using humidified gas is usually 2 to IOA/sec, and the corresponding initial heating temperature is about c1600 to 900''.

Further, during this vacuum deposition, it is not necessary to heat the plastic base material in advance (Ct); rather, heating the plastic base material at a site provides better results in improving transparency.

However, in general, when using a humid gas that heats up to about 1508C, vacuum evaporation can be carried out under conditions such that the temperature is preferably 125°C or lower, and most preferably 100°C or lower (including non-heating). .

The vapor-deposited film obtained in this way adheres uniformly and firmly to the surface of the plastic substrate, and is mainly composed of lower-order oxides, indium oxide and tin oxide, and has a dark brown color and low transparency. .

The thickness of this vapor-deposited film is usually about 60 to 500 mm when using a non-humidified gas, that is, a mixed gas that does not contain water vapor, and about 60 to 2000 mm when using a humidified gas.
It is λ. Of course, depending on the situation, it may be thinner than the above thickness,
Or you can make it thicker.

However, if the film thickness is too thin, local defects are likely to occur (on the other hand, if it is too thick, the oxidation treatment must be performed under harsh conditions, such as heat treatment at high temperature for a long time, which is not preferable).

Next, in the present invention, the above deposited film is subjected to an oxidation treatment.

Transparency can only be improved through this process. For the oxidation treatment, methods such as a chemical treatment, a chemical conversion treatment, a glow discharge oxidation treatment, and an autogelation treatment can also be employed, by generally performing a heat treatment in an oxidizing atmosphere such as air, oxygen, or ozone.

In this invention, the conditions for the oxidation treatment vary depending on whether water vapor is included in the mixed gas. When water vapor is not included, it is generally better to use somewhat harsher conditions. -1 When water vapor is included, fairly mild conditions can be selected over a relatively wide range of film thicknesses as described above. For example, when heat treatment is performed in air, it is usually 130 to 1.
506C is sufficient. Of course, a treatment temperature up to 2008C that is acceptable for the plastic base material may be selected. The treatment time is usually 30 to 60 minutes at the above heat treatment temperature.
A short time of about a minute is sufficient. If necessary, the processing time may be longer than this.

The thus obtained transparent conductive film of the present invention generally has a film thickness in the range of 60 to 2000A, and has an S n/
The I n ratio changes continuously in the thickness direction, and the S n ratio on the inner surface of the film increases.
/I n ratio is significantly lower than the average ratio of the entire film, and the S n /I n ratio on the outer surface side of the film is significantly higher than the average ratio of the entire film. In addition, the surface resistance generally ranges from 0.1Ω/d to LOOKΩ/d, usually as low as 0.1 to 1 (lΩ/-), and even as low as 600Ω/d.
It has a visible light transmittance of 75% or more, usually 80% or more, and (in a preferred embodiment, a good transparency of 90 cm or more).

As described above, the transparent conductive film of the present invention can be manufactured advantageously by the first and second manufacturing methods, but it goes without saying that it can also be manufactured by other methods. For example, as a means to continuously change the Sn/ln ratio in the thickness direction, instead of using the difference in vapor pressure between metallic indium and metallic tin, two evaporation source containers are used and metallic indium is added to these containers. The amount of evaporation may be changed over time by setting the metal tin and the metal tin separately and adjusting the heating temperature of both metals as appropriate.

In addition, in order to enable continuous vapor deposition, the plastic substrate is run at an appropriate speed, and of the two evaporation source containers lined up in the running direction, metal indium is set in the rear container and metal tin is set in the front container. Even when both are simultaneously heated and evaporated, it is possible to obtain a transparent conductive film having the structure of the present invention in which the S n/I n ratio continuously changes in the thickness direction.

Note that in these methods, a mixed gas of oxygen gas and an inert gas is used as the oxidizing gas, as in the first and second manufacturing methods described above, and humidification in which water vapor is included in this mixed gas is used. When gas is used, good results can be obtained in terms of transparency and initial surface resistance.

Of course, if the transparent conductive film of the present invention is not required to have a high degree of permeability or low surface resistance, oxygen gas may be used as the oxidizing gas in the first and second manufacturing methods and the other manufacturing methods mentioned above. It is okay to make changes such as using it alone.

As detailed above, the transparent conductive film of the present invention has S n
/1 has a specific structure in which the n ratio changes continuously in the thickness direction, and this structure provides effects such as greatly improving resistance stability, chemical resistance, and abrasion resistance, as well as improving the first and second As seen in the manufacturing method of 2007, it is possible to provide a conductive film that is improved in terms of transparency and conductivity compared to conventional ones. Since this conductive film is formed on the surface of a plastic base material, it can take advantage of the base material's advantages in terms of flexibility, processability, impact resistance, weight, etc., making it possible to create new displays. It can be effectively used for various purposes such as preventing static electricity on transparent articles and blocking electromagnetic waves.

In order to further improve the abrasion of the transparent conductive film and to make it moisture resistant, a protective coating may be applied to this film by a conventionally known method, if necessary. In addition, in order to impart adhesive properties to the conductive film,
If necessary, further appropriate processing can be performed on this film.

Hereinafter, the present invention will be explained in more detail based on examples. Note that this invention' is not limited to these embodiments.

Example 1 After evacuating the inside of the bell jar to 1 x 1 O-511IIIH, a dry mixed gas consisting of 20 volumes of oxygen gas and 80 volumes of argon gas was introduced to achieve 20 x 10" mHp.
The vacuum level was adjusted to . Next, an evaporation source made of metallic indium and metallic tin (metal tin 10% by weight) loaded on a tungsten board was first heated to about 800°C by resistance heating, and then placed at a distance of about 9 cm from the evaporation source. Vacuum deposition was performed on the set polyester film having a thickness of 100 μm at a deposition rate of 6 A/sec. After that, the temperature was gradually increased to about 1100° while keeping the above deposition rate constant.
The entire amount was vapor-deposited by heating to C. ) The obtained vapor deposited film was 300 mm thick, blackish brown, and opaque. Further, when the surface resistance and visible light transmittance of this vapor-deposited film were examined, the surface resistance was IKΩ/-1 and the visible light transmittance was 6%. , 1 The visible light transmittance was measured by placing a polyester film on which no vapor deposited film was formed into the compensation optical path.

All visible light transmittances described in this specification were measured according to the above method.

Next, the above deposited film was heat-treated in air at 200°C for 30 minutes to obtain a transparent conductive film of the present invention. The surface resistance of this film was 1.2 KΩ2, and the J1 visible light transmittance was 90%. Also, when this film was left in the air (dark room) for 10 days, the surface resistance was 1.4Ω/d, and RO (initial value)/
RE (value after days) was 0.83.

Furthermore, the film having such characteristics is etched little by little by sputtering, and the content of metallic indium and metallic tin at each thickness is determined by ElectronSpect.
roscopy for chemical anal
ysis (hereinafter referred to as ESCA) to examine each Sn/In ratio, the changes in the thickness direction were almost the same as those shown in FIG.

On the other hand, in this method, the oxidation treatment conditions are 130℃ and 60℃.
When the temperature was changed to 150°C for 60 minutes, the surface resistance was 0.7 K, IJ/ld, and the visible light transmittance was 37 inches and 60 inches, respectively.

As described above, when water vapor is not included in the vacuum system, high transparency cannot be obtained under relatively mild oxidation conditions.

Reference Example 1 A transparent conductive film was obtained in exactly the same manner as in Example 1, except that the metal tin content of the evaporation source consisting of metal indium and metal tin was approximately 3% by weight. The surface resistance of this film is 3.97
4. The visible light transmittance was 92%. In addition, Ro/Rt after leaving this film in the air (dark room) for 10 days.
was 0.65.

Reference Example 2 Using the same dry mixed gas as in Example 1 and in a vacuum system adjusted to the same degree of vacuum, metal indium on a tungsten board was first heated to about 800°C and then heated to 6λ/
Vacuum deposition was performed on a polyester film at a deposition rate of seconds to form a deposited film with a thickness of about 250 to 300^. Next, the vacuum system was returned to the atmosphere, and metal tin was loaded onto the tungsten board as a new evaporation source, and the heating temperature was increased to approximately 1.20℃.
A vapor deposited film having a thickness of about 20 to 40 λ was further formed on the vapor deposited film formed on the polyester film by the same method as in the case of metal indium except that the temperature was 0°C. The ratio of the metal indium and the metal tin used as the evaporation source is almost the same as in Example 1.

Then, heat treatment was performed in air at 200° C. for 30 minutes to obtain a transparent conductive film having a completely double-layered vapor deposited film of indium oxide and tin oxide. The surface resistance of this film is 3Ω
The visible light transmittance was about 90%. The Ro/Rt after leaving this film in the air (dark room) for 10 days was about 0.81. On the other hand, a cellophane tape manufactured by Nitto Electric Industries, Ltd. After attaching A29 and peeling it off, it was observed that a tin oxide film was attached to the surface of the peeling tape. Ro/Rt is approximately 0.63~
0.,7, and the resistance stability was marked and decreased.Furthermore, even when trying to attach the release tape to the vapor deposited film again, it could not be applied due to the adhesiveness.

Example 2 After evacuating the inside of the bell jar to 1 x 105 mH9, a mixed gas of 20 volumes of oxygen gas and 80 volumes of argon gas with a relative temperature of about 95% was introduced, and the temperature was 20 x 10" mmH.
The degree of vacuum was adjusted to 5'. Next, an evaporation source made of metallic indium and metallic tin (metal tin 10% by weight) 0°021 loaded on a tungsten board was first heated to about 800°G by resistance heating, and set at a distance of about 9 CIN from the evaporation source. Vacuum deposition was performed on a 100μ thick polyester film at an evaporation rate of 6/sec. After that, the temperature was gradually raised to about 1100℃ to keep the above deposition rate constant.
The entire amount was vapor-deposited by heating to .

The obtained deposited film had a thickness of 300^, was blackish brown, and was opaque. In addition, when we investigated the surface resistance and visible light transmittance of this vapor-deposited film at 600 μm, we found that the surface resistance was 2,9 Ω/c+#, and the visible light transmittance was 25%.
Met.

Next, the above deposited film was heat-treated in air at 150°C for 60 minutes to obtain a transparent conductive film of the present invention. The surface resistance of this film was 1.5 Ω/d, and the visible light transmittance was 97 cm. Furthermore, when this film was left in the air (dark room) for 10 days, the surface resistance was 1.8Ω/d, and lLo/Rt was 0.8
It was 3. Further, a film having such characteristics was subjected to S n/S by ESCA in the same manner as described in Example 1
When the ln ratio was examined, the change in the thickness direction was as shown in FIG.

Example 3 Oxidation treatment conditions were 1306C for 30 minutes, 130°C for 6
Three types of transparent conductive films were obtained in exactly the same manner as in Example 2, except that the heating time was 0 minutes, 150°C for 30 minutes, 200°C for 30 minutes, and 200°C for 60 minutes.

The surface resistance of these films is 1.3 Ω/cd and 1
．． 3 to Ω/cd, 1.3 to Ω/C1#, 1.2 to Ω
/d and 1.2Ω/d. The visible light transmittance is 87cm, 88%, 95cm, 99% and 9cm respectively.
It was 9%. In addition, these films were placed in the air (dark room).
When we investigated the change in surface resistance after leaving it for O days, we found that
Almost the same good results as in Example 2 were obtained for IL O/&L L.

Example 4 Three types of transparent conductive films were obtained in exactly the same manner as in Example 2, except that the metallic tin content of the evaporation source consisting of metallic indium and metallic tin was changed as shown in Table 1 below. . Surface resistance, visible light transmittance, and IL o / ) L of these films after being left in air (dark room) for 10 days
t was as shown in Table 1.

Table 1 Also, for the metal tin content of 20% by weight, IL
When we investigated the relationship between o/IL L and leaving time, we found that
This was as shown in curve-a in FIG. Furthermore, for those with a metal tin content of 40% by weight, ESC: A
When the change in the S n/I n ratio in the thickness direction was investigated, the results were as shown in FIG.

Reference Example 3 A transparent conductive film was obtained in exactly the same manner as in Example 2, except that the metal tin content of the evaporation source consisting of metal indium and metal tin was approximately 3% by weight. The surface resistance of this film was 5.5 Ω/cI#, and the visible light transmittance was 98%. Also,
After this film was left in the air (dark room) for 10 days, the surface resistance increased to 8.6Ω/C1#, iL o /i
Lt was 0.64.

Comparative Example 1 Except for using metallic indium alone as an evaporation source,
A transparent conductive film was obtained in exactly the same manner as in Example 2. The surface resistance of this film is 6Ω/cI#, and the visible light transmittance is 98%.
However, when this conductive film was left in the air (in a dark room) and the change in surface resistance over time was investigated, iLo/lLt was as shown in the curve in Figure 11. Note 10
The surface resistance after standing for a day was 9.8 Ω/CI#, and i o /it at this time was Example 5. By changing the gas composition of the mixed gas in Example 2, the volume ratio of argon gas in the mixed gas was The relationship between this and the surface resistance and visible light transmittance of the resulting transparent conductive film was investigated. The results were as shown in Table 2 below. As is clear from the table below, the volume percentage of argon gas is the same as the volume percentage of inert gas contained in the air (approximately 78 to 80% by volume).
Particularly good results have been obtained in terms of film transparency in the gas composition range that is made almost the same as . In addition, if the volume ratio is more than the above (if the volume is less than about 86 volume), and if the volume is less than the above (if the volume is less than about 5 volume), both will provide excellent transparency and lower surface resistance. It can be seen that a film with low conductivity was obtained.

Table 2 (6) Corresponds to the volume percentage of inert gas contained in air.

Example 6 Example 2 except that instead of a mixed gas consisting of oxygen gas and argon gas with a relative humidity of 95%, a mixed gas consisting of 21 volumes of oxygen gas and 21 volumes of nitrogen gas at the same humidity was used. A transparent conductive film was obtained in exactly the same manner.

The surface resistance of this film was 1.6 Ω/CI#, and the visible light transmittance was 98%. Also, put this film in the air (dark room) for 1 hour.
The surface resistance after standing for 0 days was 1.9Ω/d, and IL o /IL t at this time was 0.83.

Furthermore, when the change in the S n/I n ratio in the thickness direction due to ESC:A was examined, it was found to be almost the same as in Example 2.

Example 7 Except that the oxidation treatment conditions were 130'C: for 60 minutes,
A transparent conductive film was obtained in exactly the same manner as in Example 6. The surface resistance of this film is 1.2Ω/cr11, and the visible light transmittance is 8
It was 8%. Further, the change in surface resistance over time was almost the same as in Example 6.

Example 8 In Example 6, the gas composition of the mixed gas was changed, and the relationship between the volume ratio of nitrogen gas in the mixed gas and the surface resistance and visible light transmittance of the resulting transparent conductive film was investigated. The results were as shown in Table 3 below.

Table 3 (To) Air was used as the mixed gas.

As is clear from the table above, particularly good results in film transparency are obtained near gas compositions in which the volume ratio of nitrogen gas is approximately the same as the volume ratio of inert gas contained in air. . In addition, if the volume ratio is higher than the above, it is 86 volume squares or less, and when the volume ratio is lower than the above volume ratio, it is approximately 5 volume squares or more, and a conductive film with excellent transparency and low surface resistance can be obtained. It can be seen that

In Example 2, the degree of vacuum of the vapor deposition atmosphere was varied and the relationship between the degree of vacuum and the surface resistance and visible light transmittance of the resulting transparent conductive film was investigated.

The results were as shown in Table 4 below.

As is clear from this table, when water vapor is contained in the vacuum system in this invention, the atmospheric pressure is 9X10-5X.
It turns out that it is particularly desirable to have a HP of 10-3 smHP.

Table 4 Example 10 In Example 2, the relative humidity of the vapor deposition atmosphere was varied and the relationship between the relative humidity and the surface resistance and visible light transmittance of the resulting transparent conductive film was investigated. The results were as shown in Table 5 below. As is clear from this table, when water vapor is introduced into the vacuum system in the present invention (or relative humidity is preferably about 30 degrees or more, preferably about 70% or more) .

Example 11 In Example 2, a polyester film, which is a plastic base material, was heated during the vapor deposition of an evaporation source consisting of metallic indium and metallic tin, and the heating temperature of the base material and the surface resistance and visible light of the resulting transparent conductive film were determined. The relationship with transmittance was investigated. The results were as shown in Table 6 below. The heating means for the substrate was a ceramic heater, and the heating temperature was measured using a thermolabel and a thermocouple. In the table, the substrate temperature in the case of non-heating (corresponding to Example 2) was about 35°C.

Table 6 As is clear from the above table, in the present invention, it is preferable not to heat the plastic base material;
It can be seen that it is preferable to set the temperature to 256C or less, preferably 1000C or less.

Example 12 In Example 2, the deposition film thickness was kept constant (300A), and the deposition rate and the initial heating temperature of the evaporation source and the heating temperature at the end of the deposition were changed, and the deposition rate and the resulting transparency were changed. The relationship between the surface resistance and visible light transmittance of the conductive film was investigated. The results were as shown in Table 7 below. In addition, ESC of transparent conductive films obtained by these methods
The changes in S n/I n in the thickness direction due to A were all close to those in Example 2.

Table 7 Example 13 In Example 2, the deposition rate was kept constant (6λ/sec), the amount of the evaporation source was changed, and the thickness of the deposited film was varied. The results of examining the relationship between the color and visible light transmittance are shown in Table 8 below. Furthermore, the changes in the S n/I n ratio in the thickness direction of the transparent conductive films obtained by these methods by ESCA were similar to those in Example 2.

Table 8 Example 14 The evaporation rate was set to 3 A/sec, the initial heating temperature of the evaporation source was approximately 700°C, and the final heating temperature was approximately 100°C.
A vacuum-deposited film was obtained in exactly the same manner as in Example 2, except that the temperature was 0°C, the amount of evaporation source charged was 0°0661, and the thickness of the deposited film was 1000λ.

The surface resistance of this film was 2Ω/cI#, and the visible light transmittance was 6%. Next, this vapor deposited film was oxidized under the same conditions as in Example 2 to obtain a transparent conductive film of the present invention. The surface resistance of this film is IKΩ/CI#, and the visible light transmittance is 92%.
Met. In addition, when the change in surface resistance was examined when it was left in the air (dark room) for 10 days, the surface resistance was 1.2 Ω/cd, and Ko/lLt at this time was 0.82. Furthermore, the change in the S n/l n ratio in the thickness direction due to ESCA was almost the same as in Example 2.

Example 15 Oxidation treatment conditions were 130°G for 60 minutes and 200°C for 60 minutes.
Two types of Wanming conductive films of the present invention were obtained in exactly the same manner as in Example 14, except that the heating time was 0 minutes.

The surface resistance of these films is 1.3 Ω/d, respectively.

IKΩ/CI#, and the visible light transmittance was 80% and 97%, respectively. Furthermore, when left in air (dark room) for 10 days, Ro/ILL was 0.83.
It was 0.84.

Comparative Example 2 A transparent conductive film was obtained in exactly the same manner as in Example 14, except that metal indium' was used alone as an evaporation source. The surface resistance of this film is 5Ω/cJ, and the visible light transmittance is 96.
%Met. In addition, this conductive film was immersed in air (dark room) for 10 minutes.
When we investigated the change in surface resistance over time by leaving it for 8', the surface resistance was 8.3 Ω/d, and Ro/Rt at this time was 0.
It was 6.

[Brief explanation of the drawing]

Figures 1 and 2 are characteristic diagrams showing different examples of changes in the S n / I n ratio in the thickness direction in the transparent conductive film of the present invention, and Figure 3 shows changes over time in the surface resistance of the transparent conductive film. FIG. Curve-1...Transparent conductive film of this invention. Curve-b...Transparent conductive film different from this invention. Patent Applicant: Nitto Electric Industry Co., Ltd. Agent: Patent Attorney Kunio Newata] Figure 1 Figure 2

Claims (2)

[Claims] (1) An acid of 60 to 95% by weight of metallic indium and 40 to 5% by weight of metallic tin formed on the surface of a plastic base material;
This is a transparent conductive film made of metal indium, in which the weight ratio of metallic tin to metallic indium constituting the oxide is continuously changed in the film thickness direction, and the same ratio on the inner surface of the film is maintained for the entire film. A transparent conductive film characterized by having a wearable ratio that is lower than the average ratio (and at the same time, the same ratio on the outer surface of the film is set to be wearable and higher than the average ratio of the entire film. (2) Film thickness is 60-200OA, visible light (600n
m) The transparent conductive film according to claim (1), which has a transmittance of 80% or more and a surface resistance of 0.1 to 100 Ω/d.