JP7406722B2 - Flexible substrate manufacturing method and flexible substrate - Google Patents

Description

The present invention relates to a flexible substrate manufacturing method and a flexible substrate.

In recent years, with the spread of smartphones and tablets, so-called touch panels, which are operated by touching the screen with a finger, have become the mainstream user interface, and there is active development of technology to form transparent electrodes and conductive parts on transparent substrates. is being carried out. For example, Patent Document 1 listed below describes a conductive base material in which a transparent conductive part is formed by applying ink containing metal nanowires onto a transparent base material.

Furthermore, in recent years, so-called flexible displays formed on flexible film-like base materials have been developed, and techniques for manufacturing touch panels compatible with flexible displays are also being considered.

For example, Patent Document 2 listed below describes a method of manufacturing a transparent conductive sheet by applying a transparent conductive film onto a transparent film base material and heat-treating the film. It is also described that a flash lamp may be used for the heat treatment.

JP2016-91627A Japanese Patent Application Publication No. 2010-146757

As mentioned above, touch panels compatible with flexible displays are made by coating a transparent conductive material such as ITO (indium tin oxide) on the main surface of a base material made of a transparent and flexible polymer material such as resin. By doing so, sensor elements and signal lines are formed using the transparent conductive film.

Furthermore, it is known that the surface resistance of transparent conductive materials such as ITO can be reduced by subjecting them to baking treatment such as heat treatment. Therefore, as described above, heat treatment is performed after applying the transparent conductive film formed on the transparent film base material.

Therefore, the present inventor investigated a firing process using a flash lamp (hereinafter referred to as "flash lamp annealing" or simply "baking process") as described in Patent Document 2, and found the following problems. found that it exists.

For example, a rare gas flash lamp filled with xenon or the like is used for flash lamp annealing. FIG. 1 is a graph showing the spectrum of flash light emitted from a xenon flash lamp. As shown in FIG. 1, the flash light emitted from the xenon flash lamp includes light in a wavelength range from around 200 nm to 800 nm or more.

The flash light emitted from the flash lamp is irradiated not only to the transparent conductive film but also to the film-like base material coated with the transparent conductive film. Therefore, if the wavelength range included in the flash light includes a wavelength range in which the polymer material that makes up the base material has a high absorption rate, the base material will also absorb the energy of the flash light and instantly It will be heated to a high temperature. When the base material absorbs the energy of the flash light and is heated to a high temperature, the base material itself expands, melts, or releases gases such as C ₂ H ₄ and CO (also called "outgas") due to chemical reactions. .) may occur. This causes wrinkles and surface roughness on the surface of the base material itself. In addition, the base material and the applied transparent conductive film cannot expand and contract according to the deformation of the base material, resulting in damage such as peeling and cracking, causing local narrow wiring and disconnection. It ends up.

In view of the above problems, the present invention provides a method for manufacturing a flexible substrate that suppresses the occurrence of damage to a transparent base material and a transparent conductive film, and a flexible substrate that has improved reliability while lowering the resistance of the transparent conductive film. The purpose is to

The method for manufacturing a flexible substrate of the present invention includes:
A step (A) of preparing a transparent base material made of a polymeric material that exhibits a transmittance of 50% or more for light with a wavelength of 300 nm or more and 380 nm or less;
Step (B) of forming a transparent conductive film on the main surface of the transparent base material;
The transparent conductive film formed on the main surface of the transparent base material is irradiated with flash light containing a component in a wavelength band of at least 300 nm or more and 380 nm emitted from a rare gas flash lamp, and the transparent conductive film is formed on the main surface of the transparent base material. The method is characterized by including a step (C) of firing the film.

Typical materials used for the transparent conductive film include, for example, the above-mentioned ITO, ZnO, IGZO, and the like. Many of these materials used as transparent conductive films have a characteristic that the light absorption rate increases rapidly for light shorter than about 400 nm. Therefore, it is preferable from the viewpoint of energy efficiency that light in a wavelength range of at least 300 nm or more and 380 nm or less is included in the baking treatment of these transparent conductive films. A rare gas flash lamp is a discharge tube whose tube body is filled with a gas containing a rare gas, and which generates flash light by applying a voltage pulse between electrodes formed in the tube body. Examples of rare gases include xenon.

However, if the transparent substrate is made of a material with a high absorption rate, the substrate will absorb the energy of the flash light and be heated to a high temperature, causing the substrate itself to undergo thermal expansion, melting, or chemical The reaction may generate gas (also called "outgas").

Therefore, by using the above method, the loss of light energy in the wavelength band of 300 nm or more and 380 nm or less, which is used in the baking treatment of the transparent conductive film, due to the transparent base material can be suppressed to at least 50% or less. Furthermore, since absorption of light energy by the transparent base material is suppressed, the transparent base material is less likely to expand or melt, and is also suppressed from contributing to chemical reactions. Therefore, deformation of the transparent base material and generation of outgas are suppressed, and damage to the transparent base material and the transparent conductive film can be suppressed.

In addition, when baking a transparent conductive film, it is better to apply high energy instantaneously and process it for a short time than to perform low-energy light irradiation or low-temperature heating for a long time. becomes smaller. Therefore, according to the above method, a transparent conductive film having a lower surface resistance value can be formed. Note that the surface resistance value of the transparent conductive film after firing is smaller when high energy is instantaneously applied and the firing is completed in a short time, as described in the "Details of the Invention" section. will be presented with reference to experimental results.

In the above manufacturing method,
The transparent base material prepared in step (A) may be made of a material containing any one of polyethylene, polypropylene, polystyrene, polycarbonate, polyvinyl chloride, cycloolefin polymer, and acrylic resin.

The above material exhibits a transmittance of 50% or more for light in a wavelength band of 300 nm or more and 380 nm or less. In addition, the above-mentioned materials are materials that have less or no carbonyl groups that generate outgas when irradiated with light of 300 nm or more and 380 nm or less, suppress the generation of outgas, and have higher transparency. Damage to the base material and transparent conductive film can be suppressed.

In the above manufacturing method,
The transparent conductive film formed in the step (B) may be ITO with a Sn content higher than 5% by mass.

A film-like transparent base material made of resin or the like is more susceptible to heat than a base material such as glass, and is more likely to suffer from the problems described above. can't raise it enough. Therefore, when using a transparent substrate in the form of a film, it is common practice to use ITO with a reduced Sn content in order to be able to perform firing treatment even at low temperatures.

However, according to the method of the present invention, ITO, which is a transparent conductive film, can be treated at high temperature with flash light, so there is no need to prepare ITO with a reduced Sn content.

In the above manufacturing method,
The step (B) may be a step of forming a transparent conductive film on the main surface of the transparent base material.

In the above manufacturing method,
The step (C) may be a step of irradiating the flash light only once with an irradiation energy such that the surface resistance value of the transparent conductive film is 150 Ω/cm ² or less.

By using the above method, the time required for the process can be shortened, and furthermore, the surface resistance value of the transparent conductive film can be significantly reduced. Note that the fact that the surface resistance value of the transparent conductive film after firing becomes smaller when the number of irradiations is higher and the number of times of irradiation is lower is shown in the section of "Detailed Description of the Invention" with reference to experimental results.

The flexible substrate of the present invention is
A transparent base material made of a polymeric material that exhibits a transmittance of 50% or more for light in a wavelength range of 300 nm or more and 380 nm or less;
It is characterized by comprising a transparent conductive film formed on the main surface of the transparent base material, which is made of ITO and has a surface resistance value of 150 Ω/cm ² or less and a Sn content higher than 5% by mass. .

The transparent base material may be made of a material containing any one of polyethylene, polypropylene, polystyrene, polycarbonate, polyvinyl chloride, cycloolefin polymer, and acrylic resin.

With the above configuration, there is a low possibility that peeling or cracking will occur in the transparent base material or the transparent conductive film during manufacturing, so that a high-quality flexible substrate can be obtained. Furthermore, since the surface resistance value of the transparent conductive film can be configured to be low, it is possible to configure a device in which voltage drop and signal deterioration during signal transmission are suppressed.

According to the present invention, a method for manufacturing a flexible substrate in which damage to a transparent base material or a transparent conductive film is suppressed, and a flexible substrate in which the resistance of the transparent conductive film is lowered and reliability is improved are realized.

It is a graph showing the spectrum of flash light emitted from a xenon flash lamp. FIG. 1 is a cross-sectional view schematically showing the structure of an embodiment of a flexible substrate. FIG. 1 is a schematic cross-sectional view of one step for explaining the method for manufacturing a flexible substrate of the present invention. FIG. 1 is a schematic cross-sectional view of one step for explaining the method for manufacturing a flexible substrate of the present invention. FIG. 1 is a schematic cross-sectional view of one step for explaining the method for manufacturing a flexible substrate of the present invention. It is a graph showing the transmittance of each material that is a material of a transparent base material applicable to the present invention. It is a graph showing the transmittance of each material that is a material of a transparent base material that is not applicable to the present invention. 2 is a graph showing the light transmittance of ITO, ZnO, and IGZO, which are the materials of the transparent conductive film. 2 is a graph showing changes in surface resistance value with respect to the number of irradiations for each irradiation energy in the flexible substrate of Example 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for manufacturing a flexible substrate and the flexible substrate of the present invention will be described below with reference to the drawings. It should be noted that each of the following drawings is schematically illustrated, and the dimensional ratios and numbers on the drawings do not necessarily match the actual dimensional ratios and numbers.

[structure]
FIG. 2 is a cross-sectional view schematically showing the structure of one embodiment of the flexible substrate 1. As shown in FIG. The flexible substrate 1 has a structure in which a transparent conductive film 11 is formed on the main surface 10a of a transparent base material 10. From the viewpoint of device structure and human visibility, the transparent conductive film 11 is preferably formed with a thickness of 5 nm or more and 10 μm or less.

The transparent base material 10 is a film-like base material made of a polymer material and transparent to visible light. More specific types of materials will be described later in the description of the manufacturing method.

The transparent conductive film 11 is a film made of a material that is transparent to visible light and has conductivity. More specific types of materials for the transparent conductive film 11 will be described later in the description of the manufacturing method.

[Production method]
An example of a method for manufacturing the flexible substrate 1 having the transparent conductive film 11 will be described below with reference to FIGS. 3A to 3C.

(Step S1)
As shown in FIG. 3A, a film-like transparent base material 10 having flexibility and transparency to visible light is prepared. The transparent base material 10 constitutes a base layer for forming the transparent conductive film 11 formed in the next step S2.

Generally, the material of the transparent base material 10 is, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyvinyl chloride. (PVC), polysulfone (PSF), polyether resin, polyimide (PI), triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), acrylic resin (PMMA), polyurethane resin (PU), polyvinyl resin (PVA), polyether sulfone (PES), cellulose nanofiber, and the like.

When the material of the transparent base material 10 according to the present invention is irradiated with light in a wavelength range of 300 nm or more and 380 nm or less in step S3 described below, the material of the transparent base material 10 is 50% A material that exhibits a transmittance higher than that is used. This is because if the transmittance of the transparent base material is 50% or less, chemical changes will be induced within the material and outgas will be generated. Specific materials used include polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyvinyl chloride (PVC), cycloolefin polymer (COP), acrylic resin (PMMA), etc. It is preferable.

This step S1 corresponds to step (A).

(Step S2)
As shown in FIG. 3B, a transparent conductive film 11 is formed on the main surface 10a of the transparent base material 10. Note that in FIGS. 3B and 3C, hatching different from that in FIG. 2 is used to represent the difference between before and after the firing process of the transparent conductive film 11.

Specific materials for the transparent conductive film 11 include, for example, ITO, ZnO, IGZO, and the like. Note that in this embodiment, since firing treatment at high temperatures is possible, ITO with a Sn content higher than 5% by mass is used, similar to ITO used in glass-based devices that can be treated at high temperatures. be able to.

As the content of Sn increases, the resistance value decreases, and the resistance value is the lowest at about 10% by mass, but on the other hand, firing at a high temperature is required. However, when using a transparent base material made of a polymeric material, firing at high temperatures becomes difficult. For example, if the base material is a PET film, high-temperature firing cannot be performed, so a transparent conductive film for low-temperature processing with a Sn content of 5% by mass or less is often used.

Note that a transparent conductive film having an Sn content of 10% by mass requires firing at 200° C. for a holding time of 30 minutes or more, for example. In a PET film, the temperature at which it can withstand high temperatures for a long period of time is around 150° C., and the optimal Sn content cannot be achieved, so ITO for low-temperature processing with a low Sn content is used.

In this embodiment, as will be described later in step S3, the firing process is performed by instantaneous optical heating using the flash lamp 20. Therefore, it is not necessary to prepare ITO for low-temperature treatment with an Sn content of 5% by mass or less, and the same ITO used for high heat-resistant base materials such as glass can be used to form the transparent conductive film 11. be able to. More specifically, it is preferable to use ITO with a Sn content higher than 5% by mass, and more preferably ITO with a Sn content of 7 to 20% by mass. For example, as described above, ITO having a Sn content of 10% by mass can be used.

Methods for forming the transparent conductive film 11 on the main surface of the transparent substrate 10 include methods such as direct coating, vapor deposition, and sputtering. The method of applying the transparent conductive film 11 to the transparent base material 10 is difficult because the density of the film may be uneven depending on the method of application, or the transparent conductive film 11 may expand or contract during the process of evaporating the solvent after application, and the transparent conductive film 11 may This may put stress on the material 10. Therefore, the method for forming the transparent conductive film 11 is preferably vapor deposition or sputtering.

This step S2 corresponds to step (B).

(Step S3)
As shown in FIG. 3C, the transparent conductive film 11 formed on the transparent base material 10 is irradiated with flash light L1 from the flash lamp 20 only once, and the transparent conductive film 11 is subjected to a baking process. Here, the light intensity of the flash light L1 emitted from the flash lamp 20 is preferably set so that the surface resistance value of the transparent conductive film 11 becomes 150 Ω/cm ² or less with one irradiation. The relationship between the light intensity and the surface resistance value will be explained in the experimental results described later.

In order to cope with the above, the flash lamp 20 can use a rare gas flash lamp as an example of a lamp that emits the flash light L1 including light in a wavelength band of 300 nm or more and 380 nm or less, and can instantly obtain high light output. A xenon flash lamp is preferred. Note that the light emitted by the flash lamp 20 may include light other than the wavelength band of 300 nm or more and 380 nm or less. Moreover, although one flash lamp 20 is shown in FIG. 3C, an apparatus in which a plurality of flash lamps 20 are arranged may be used.

When the transparent base material 10 is irradiated with the flash light L1 having a wavelength range of 300 nm or more and 380 nm or less, most of the light energy is absorbed by the transparent conductive film 11 made of ITO, and is used in the baking process of the transparent conductive film 11. consumed. At this time, since not all the light is absorbed by ITO, some of the light in the wavelength range of 300 nm or more and 380 nm or less is also irradiated onto the transparent base material 10.

However, as described above, in the present embodiment, the transparent base material 10 exhibits a transmittance of 50% or more for light in a wavelength band of 300 nm or more and 380 nm or less, and is not irradiated with light in the wavelength band. Materials that are less likely to generate outgassing are also selected. Therefore, although the transparent base material 10 is slightly heated, the generation of deformation, peeling, cracking, etc. during the firing process is suppressed.

FIG. 4A is a graph showing the transmittance of each material that is a material of a transparent base material applicable to the present invention. Specifically, polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyvinyl chloride (PVC), acrylic resin (PMMA), triacetyl cellulose (TAC), cycloolefin polymer ( COP), the results of measuring the transmission spectrum of each base material are shown. All of these base materials have high transmittance in a wavelength range of 300 nm or more, and maintain a transmittance of 70% to 80% or more in this wavelength range.

On the other hand, FIG. 4B is a graph showing the transmittance of each material used as the material of the transparent base material that cannot be applied to the present invention. Specifically, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), cycloolefin copolymer (COC), polyimide (PI), polyvinyl resin (PVA), polyether sulfone (PES), polyurethane resin (PU ) are shown. As shown in FIG. 4B, the transmittance is low for light in a wavelength band of 300 nm or more and 380 nm or less. Therefore, most of the light in the wavelength band of 300 nm or more and 380 nm or less that is not absorbed by the transparent conductive film is absorbed by the transparent base material, which tends to cause a thermal load on the base material. This makes it difficult to suppress the occurrence of deformation, peeling, cracking, etc. of the base material during the firing process.

In the case of a configuration in which the transparent base material 10 is formed on one side and the transparent conductive film 11 is formed on the other side, the surface on which the transparent conductive film 11 is formed faces the flash lamp 20 side. It is preferable to perform the firing treatment after arranging. By irradiating the flash light L1 in this way, the transparent conductive film 11 absorbs most of the light in the wavelength band of at least 300 nm or less and functions as a filter, so that the light in the wavelength band reaches the transparent base material 10. It becomes difficult to do. Therefore, since the amount of light energy absorbed by the transparent base material 10 is suppressed, deformation of the transparent base material 10 and generation of outgas are suppressed.

As shown in FIG. 5, the light transmittance of ITO, ZnO, and IGZO, which are the materials of the transparent conductive film 11, decreases rapidly in the wavelength range of 300 nm to 380 nm. It has characteristics.

Although various factors can be considered to cause outgassing, carbonyl groups included in the composition of the material of the transparent base material 10 are considered to be one of the factors. As shown in the reaction formula below, when carbonyl groups are irradiated with ultraviolet light with a wavelength of 400 nm or less, the bonds are broken and gases such as ethylene gas (C ₂ H ₄ ) and carbon monoxide (CO) are generated. . This ethylene gas, carbon monoxide, etc. accumulate as outgas inside the transparent base material 10 or between the transparent base material 10 and the transparent conductive film 11, causing damage to the transparent base material 10 and the transparent conductive film 11. This is thought to be the cause of the

This step S3 corresponds to step (C).

[Example]
The present invention will be explained in more detail with reference to the following examples, but the scope of the present invention is not limited by these examples.

(Example 1)
Example 1 is a flexible substrate 1 manufactured through the steps S1 to S3 described above. The detailed conditions of the materials and processes used are as follows.

《Step S1》
As the transparent base material 10, a film base material whose main component was COP was used. The thickness of the substrate was 188 μm.

《Step S2》
The transparent conductive film 11 was formed on the transparent base material 10 by vapor deposition using ITO having a Sn content of 10% by mass as a material for the transparent conductive film 11. The transparent conductive film 11 was formed to have a thickness of 80 nm in an area of 50 mm x 50 mm.

《Step S3》
Using the flash lamp 20 schematically shown in FIG. 3C, flash light L1 having a spectrum as illustrated in FIG. 1 and having an optical output in a wavelength band of 300 nm or more and 380 nm or less was irradiated. Specifically, the flash lamp 20 used was a device in which 10 lamps each having a light emission length of 250 mm, a tube diameter of φ13, and a sealed gas pressure of 450 torr were lined up.

(Comparative example 1)
Comparative Example 1 was a substrate manufactured through each of the steps S1 to S3 above using a transparent base material 10 made of a material different from that of Example 1. The detailed conditions of the materials and processes used are as follows.

《Step S1》
As the transparent base material 10, a film base material whose main component was PET was used. The size of the substrate was 50 mm x 50 mm, and the thickness was 125 μm.

《Step S2》
The transparent conductive film 11 was formed on the transparent base material 10 by vapor deposition using ITO having a Sn content of 10% by mass as a material for the transparent conductive film 11. The transparent conductive film 11 was formed to have a thickness of 80 nm in an area of 50 mm x 50 mm.

(Comparative example 2)
Comparative Example 2 was a substrate manufactured through each of the steps S1 to S3 above using a transparent base material 10 made of a material different from that of Example 1, Comparative Example 1, and Comparative Example 2. The detailed conditions of the materials and processes used are as follows.

《Step S1》
As the transparent base material 10, a base material whose main component was glass was used. The size of the substrate was 50 mm x 50 mm, and the thickness was 1000 μm.

《Step S2》
The transparent conductive film 11 was formed on the transparent base material 10 by vapor deposition using ITO having a Sn content of 10% by mass as a material for the transparent conductive film 11. The transparent conductive film 11 was formed to have a thickness of 80 nm in an area of 50 mm x 50 mm.

(Comparative example 3)
A substrate manufactured by using a transparent base material 10 made of a material different from that of Example 1, forming a transparent conductive film 11 having a thickness different from that of Comparative Example 1, and going through each of the steps S1 to S3 above. was designated as Comparative Example 2. The detailed conditions of the materials and processes used are as follows.

《Step S1》
As the transparent base material 10, a base material whose main component was PET was used. The size of the substrate was 50 mm x 50 mm, and the thickness was 125 μm.

《Step S2》
The transparent conductive film 11 was formed on the transparent base material 10 by vapor deposition using ITO having a Sn content of 5% by mass as a material for the transparent conductive film 11. The transparent conductive film 11 was formed to have a thickness of 80 nm in an area of 50 mm x 50 mm.

[Experiment 1]
For the above-mentioned Example 1, Comparative Example 1m, Comparative Example 2, and Comparative Example 3, an experiment was conducted in which the transparent conductive film 11 was subjected to baking treatment by changing the irradiation energy (J/cm ² ) of the flash light L1. The surface resistance value of the flash light L1 was measured by increasing the irradiation energy every 0.1 J/cm ² . Furthermore, for Comparative Examples 1 to 3, as a comparative experiment, firing treatment was also performed by heating at a low temperature for a long time using a furnace.

(result)
The results of baking the transparent conductive film 11 by changing the irradiation energy (J/cm ² ) of the flash light L1 are as follows. In Example 1, neither wrinkles nor surface roughness occurred on the transparent base material 10. When the transparent conductive film 11 whose surface resistance value before the baking process is 45 Ω/cm ² is irradiated with the flash light L1 with an irradiation energy of 6.5 J/cm ² , the surface resistance value of the transparent conductive film 11 after the baking process is was the minimum value of 23Ω/cm ² .

In Comparative Example 1, when the irradiation energy was 3.2 J/cm ² or more, wrinkles were observed on the transparent base material 10, and when the irradiation energy was 5.0 J/cm ² or more, surface roughness was observed on the transparent base material 10. As a result, a portion of the transparent conductive film 11 was ruptured. When the transparent conductive film 11 whose surface resistance value before baking treatment is 45Ω/cm ² is irradiated with flash light L1 with irradiation energy of 3.1 J/cm ² , the surface resistance value of the transparent conductive film 11 after baking treatment is was 37Ω/cm ² .

Regarding the baking treatment by heating at a low temperature for a long time, the surface resistance value of the transparent conductive film 11 was changed from 45Ω/cm ² to 44Ω/cm ² by performing the treatment at 150° C. for 30 minutes.

In Comparative Example 2, since the transparent substrate 10 was made of glass, wrinkles and surface roughness did not occur even when the irradiation energy was up to 13 J/cm ² . When the transparent conductive film 11 with a surface resistance value of 48 Ω/cm ² before the baking process is irradiated with the flash light L1 with an irradiation energy of 12 J/cm ² , the surface resistance value of the transparent conductive film 11 after the baking process becomes the minimum. The result was 22Ω/cm ² .

Regarding the baking treatment by heating at a low temperature for a long time, the surface resistance value of the transparent conductive film 11 was changed from 48Ω/cm ² to 27Ω/cm ² by performing the treatment at 200° C. for 60 minutes.

In Comparative Example 3, when the irradiation energy was 3.2 J/cm ² or more, wrinkles were observed on the transparent base material 10, and when the irradiation energy was 3.4 J/cm ² or more, the transparent base material 10 had surface roughness. Occurred. When a flash light L1 is irradiated with an irradiation energy of 3.0 J/cm ² to a transparent conductive film 11 whose surface resistance value before baking treatment is 200Ω/cm ² , the surface resistance value of the transparent conductive film 11 after baking treatment is was 162Ω/cm ² .

Regarding the baking treatment by heating at a low temperature for a long time, the surface resistance value of the transparent base material 10 was changed from 200Ω/cm ² to 35Ω/cm ² by performing the treatment at 150° C. for 30 minutes.

The results of the firing process using the flash lamp 20 and the firing process using low-temperature, long-term heating are summarized as follows. In addition, in the table, the numerical value in parentheses for irradiation energy indicates the minimum irradiation energy at which wrinkles and surface roughness were confirmed on the transparent base material 10.

From the above, according to the configuration of Example 1, the resistance can be lowered without causing wrinkles or surface roughness in the transparent conductive film 11 by using less energy and by short-time baking treatment using the flash lamp 20. is confirmed.

[Experiment 2]
The irradiation energy was changed to 2J/cm ² , 3J/cm ² , 4J/cm ² , 5J/cm ² , and 6J/cm ² to the flexible substrate 1 having the configuration of Example 1, and flash light of each energy was applied. An experiment was conducted in which irradiation of L1 was repeated 0 times, 1 time, 2 times, 3 times, 4 times, 5 times, 10 times, and 20 times. The time interval of light irradiation was 5 seconds.

(result)
FIG. 6 is a graph showing changes in surface resistance value for each irradiation energy and the number of irradiations in the flexible substrate 1 of Example 1. As shown in FIG. 6, it can be seen that by irradiating the high energy flash light L1, the degree of decrease in the surface resistance value is increased. Even if the irradiation is repeated several times, no significant decrease in the surface resistance value is observed after the second and subsequent irradiations.

From the above, it can be seen that it is preferable to adjust the irradiation energy so that the surface resistance value of the transparent conductive film 11 is reduced to the expected range, and to complete the irradiation with the flash light L1 in one irradiation.

[Experiment 3]
Polyethylene terephthalate (PET), polyimide (PI), polyethylene naphthalate (PEN), polycarbonate (PC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene (PE), which are the materials of the transparent base material 10 , polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and acrylic resin (PMMA), experiments were conducted on the damage that appears on the surface depending on the irradiation energy.

(result)
The damage to each material is as shown in the table below. A shows no change, B shows the occurrence of wrinkles due to thermal expansion and contraction, and C shows the occurrence of surface roughness due to outgas. In addition, in the table, t=10 indicates that the thickness is 10 μm.

As can be seen from the table above, in Experiment 1, the materials for which no change appeared on the substrate surface at the irradiation energy of 7 J/cm ² that provided the minimum surface resistance value of the transparent conductive film were polycarbonate (PC) and cycloolefin. They were polymer (COP), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and acrylic resin (PMMA).

[Another embodiment]
Another embodiment will be described below.

<1> The method for manufacturing the flexible substrate 1 described above not only irradiates the transparent base material 10 and the transparent conductive film 11 layer by layer with the flash light L1, but also irradiates each layer of the transparent base material 10 and the transparent conductive film 11 with the flash light L1. The flash light L1 may be irradiated onto a multilayered substrate.

In the method for manufacturing the flexible substrate 1 of the present invention, by appropriately adjusting the irradiation energy of the flash light L1, it is possible to easily perform the optimum firing process according to the material and shape. In other words, it is possible to perform the optimum firing process depending on the flexible substrate 1 for each layer or the flexible substrate 1 having a multilayer structure.

1: Flexible substrate 10: Transparent base material 11: Transparent conductive film 20: Flash lamp L1: Flash light

Claims (5)

A step (A) of preparing a transparent base material made of a polymeric material that exhibits a transmittance of 50% or more for light with a wavelength of 300 nm or more and 380 nm or less;
Step (B) of forming a transparent conductive film on the main surface of the transparent base material;
The transparent conductive film formed on the main surface of the transparent base material is irradiated with flash light containing a component in a wavelength band of at least 300 nm or more and 380 nm emitted from a rare gas flash lamp, and the transparent conductive film is formed on the main surface of the transparent base material. A method for manufacturing a flexible substrate, comprising a step (C) of firing a film. The transparent base material prepared in step (A) is characterized in that it is made of a material containing any one of polyethylene, polypropylene, polystyrene, polycarbonate, polyvinyl chloride, cycloolefin polymer, and acrylic resin. The method for manufacturing a flexible substrate according to claim 1. 3. The method for manufacturing a flexible substrate according to claim 1, wherein the transparent conductive film formed in the step (B) is ITO with a Sn content higher than 5% by mass. The flexible substrate according to any one of claims 1 to 3, wherein the step (B) is a step of forming the transparent conductive film on the main surface of the transparent base material. Production method. 1. The step (C) is a step of irradiating the flash light only once with an irradiation energy such that the surface resistance value of the transparent conductive film is 150 Ω/cm ² or less. 4. The method for manufacturing a flexible substrate according to any one of 4.

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