JP2012071438A - Method of heat treatment of resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of heat treatment of resin films by which removal of the residual stress, dehydration, degassing, and solvent removal from the resin films are easily made.SOLUTION: The method enables a resin film 2 to undergo heat treatment to remove its residual stress. The method comprises, in order, a film placement step to place the resin film 2 in chamber 11, an evacuation step to evacuate the chamber 11, a heating step to heat the resin film 2, and a cooling step to cool the resin film 2. The resin film 2 is kept free of stress and the inside of the chamber 11 is kept evacuated from the heating step to the cooling step.

Description

  The present invention provides a resin film for removing moisture, solvent, oligomers and residual stress remaining in the resin film, and promoting crystallization of a transparent conductive film such as ITO formed on the resin film by a sputtering method or the like. It is related with the heat processing method of the resin film which heat-processes.

The demand for higher performance of transparent conductive films on resin films is becoming more severe, especially in the case of transparent conductive films with functionalities that are essential not only for solar cells but also for liquid crystal displays, organic EL, touch panels, mobile phones, personal computers, etc. There is a growing demand for higher performance for transparent conductive films.
Furthermore, the transparent conductive film such as ITO film on the resin film has very high quality required for spot performance and slidability in the resistance type touch panel, and in order to satisfy this requirement, the degree of crystallinity of ITO or the like is high. Therefore, it is required to satisfy the required performance. In addition, the transparent conductive film such as the electrostatic capacity type ITO film has high transparency, low resistance value, and the etching pattern has been made fine for high quality. It is required to be able to withstand the immersion time, and for this purpose, the adhesiveness between the resin film and the transparent conductive film is good, and high crystallinity of the transparent conductive film is required.

  Such a transparent conductive film is formed by sputtering a transparent conductive film made of ITO (indium tin oxide) or the like in combination with an HC (hard coat) film on the surface of a resin film mainly made of PET (polyethylene terephthalate) or the like. What is formed by is the subject.

  When the required quality such as heat resistance is higher than PET, the resin film is transparent such as PEN (polyethylene naphthalate), PC (polycarbonate), ZEONOR, ARTON, PI (polyimide), PEEK (polyether ether ketone), etc. Expansion to film is progressing gradually. Recently, as the transparent conductive film, methods according to various applications such as GZO (gallium zinc oxide), AZO (aluminum zinc oxide), and a coating film containing ITO powder have been used.

  The resin film used as a base film for such a transparent conductive film is not only transparent, but also has good dimensional stability and low residuals such as moisture, gas, and solvent. It is known that it greatly contributes to improving the adhesion of the film to the resin film, lowering the resistance of the transparent conductive film, ensuring the stability of the resistance value, and crystallization of ITO or the like constituting the transparent conductive film. Under such circumstances, in order to achieve the high quality required for the transparent conductive film such as ITO film, it is required to reduce the moisture, gas, residual solvent, etc. in the film as much as possible before sputtering. .

  Therefore, as disclosed in Patent Document 1, conventionally, sputtering was performed by heating in the atmosphere for a long time to reduce the heat shrinkage value as much as possible. However, this method cannot completely remove moisture, gas and solvent. This is because no matter how much heating is performed, the film is heated in the atmosphere, so that the equilibrium moisture, gas, solvent, and the like in this atmosphere remain, and the film only becomes in an equilibrium state. In addition, in order to stabilize the heat shrinkage value of the resin film, it is necessary to heat at a high temperature for a long time. Therefore, the energy required for this treatment is enormous, and the processing apparatus has a very large heating furnace (for example, a width). 3m × length 50m × height 3m) and the price is very high. In this apparatus, heating is performed while rewinding the resin film for a long time of about 150 ° C. × 60 to 90 minutes.

JP-A-1-275031

However, in the above heating furnace method in the atmosphere, since hot air is applied to the resin film in an atmosphere containing moisture and solvent, it is difficult to completely remove moisture, gas, solvent and the like from the resin film. Become.
And in order to heat shrink the resin film to ensure the dimensional stability of the resin film and sufficiently remove moisture etc., the heat treatment time of the resin film must be lengthened, and the productivity is greatly reduced. become. In addition, the heat treatment apparatus is increased in size.

  In addition, the above-described heating furnace method in the air has a problem in that, particularly when a thin resin film such as a PET film having a thickness of 50 μm or less is heat-treated, twist wrinkles or wrinkles are likely to occur in the resin film. It was.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a method for heat-treating a resin film capable of efficiently performing residual stress removal, dehydration, degassing, and desolvation in the resin film. It is.

The present invention is a method of heat treating the resin film so as to remove the residual stress of the resin film,
A film placement step of placing the resin film in a chamber;
Next, a evacuation step for evacuating the chamber;
Next, a heating step for heating the resin film;
Next, a cooling step for cooling the resin film,
Between the heating process and the cooling process, the resin film heat treatment method is characterized by maintaining a state where no tension is applied to the resin film and a vacuum state in the chamber (Claim 1).

  In the heat treatment method for the resin film, a state in which no tension is applied to the resin film and a vacuum state in the chamber are maintained from the heating step to the cooling step. Thereby, removal of residual stress in the resin film, dehydration, degassing, and solvent removal can be performed efficiently in a short time at a low temperature.

  That is, by performing the heating step while maintaining the vacuum state in the chamber, moisture, gas, solvent, and the like in the resin film can be effectively removed in a short time. Moreover, the residual stress in the resin film can be removed in a short time. Accordingly, the chamber can be miniaturized, and the heat treatment apparatus can be miniaturized.

  Moreover, since the said heating process is performed maintaining a vacuum state, the heat dissipation from a resin film is smaller than in the air, and heat retention is very good. Moreover, since the boiling point drop by vacuum can be expected, the residual stress in the resin film can be removed, dehydrated, degassed, and desolventized more efficiently.

Further, during the period from the heating step to the cooling step, the resin film is kept in a state where no tension is applied, so that residual stress is removed in a state where no external force acts on the resin film, and the surface flatness of the resin film is reduced. Can be secured. Further, since the cooling step is performed in a state where no tension is applied to the resin film, the distortion generated with the cooling is hardly left as residual stress in the resin film, and the flatness of the surface of the resin film can be ensured. it can.
That is, by maintaining tension free, heat shrinkage is not hindered and residual strain is not left, so that the heat treatment effect of the resin film can be sufficiently imparted to the resin film.

  As described above, according to the present invention, it is possible to provide a method for heat-treating a resin film that can efficiently perform removal of residual stress, dehydration, degassing, and solvent removal in the resin film.

FIG. 3 is an explanatory diagram of a heat treatment apparatus in the first embodiment. The diagram showing the moisture content after heat processing in example 1 of an experiment. The diagram showing the relationship between the heating temperature at the time of heat processing in Example 2, and a thermal contraction rate. The diagram showing the X-ray diffraction data in before and after heat processing in example 3 of an experiment. In Experimental Example 4, (A) SEM photograph of ITO film before heat treatment, (A) SEM photograph of ITO film after heat treatment.

  In the invention of claim 1, examples of the resin film include PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PE (polyethylene), PP (polypropylene), PMMA (polymethyl methacrylate resin), and PC (polycarbonate). ), TAC (triacetyl cellulose), PI (polyimide), PEEK (polyether ether ketone), PPS (polyphenylene sulfide), nylon, Arton (registered trademark), ZEONOR (registered trademark), and the like. Further, a hard coat layer made of, for example, an ultraviolet curable paint may be formed on these resin films. Moreover, you may add the inclination coating material and hard-coat-paint adhesion additive for improving the adhesiveness between a hard-coat layer and a resin film.

Moreover, the thickness of the said resin film can be 10-250 micrometers, for example. Moreover, when the thickness of the resin film is 10 to 50 μm, the effects of the heat treatment method described above can be further enhanced.

Moreover, when the said resin film is a stretched film, removal of a residual stress can be effectively performed especially by using the heat processing method of the resin film concerning this invention.
In the present invention, if necessary, heat treatment is performed while flowing an appropriate amount of gas such as N ₂ , O ₂ , H ₂ , Ar, Xe, Kp, and NH ₃ in the above-described chamber in a vacuum state. Is also possible.

In the method for producing a resin film according to claim 1, it is preferable that a transparent conductive film is formed on at least one surface of the resin film (claim 2).
In this case, the film formation state of the transparent conductive film can be improved. That is, the resistance and uniformity of the transparent conductive film can be ensured and crystallization can be promoted. Thereby, since durability at the time of etching for patterning performed in a subsequent process can be improved, the selectivity of the etchant is increased and the etching process can be stabilized. As a result, the uniformity of the resistance value can be ensured and the durability can be improved.
As the transparent conductive film, for example, ITO (indium tin oxide), AZO (aluminum zinc oxide), GZO (gallium zinc oxide), SnO ₂ (tin oxide) or the like formed by a sputtering method or the like is used. be able to.

Moreover, it is preferable that the said vacuum state is a vacuum degree of a pressure of 5 * 10 ^<-2 > Pa or less.
In this case, moisture, gas, solvent and the like in the resin film can be effectively removed in a shorter time. Moreover, the residual stress in the resin film can be removed in a shorter time.
In addition, when the degree of vacuum is a pressure exceeding 5 × 10 ⁻² Pa, it is difficult to sufficiently shorten the removal time of moisture, gas, solvent, etc. in the resin film. It may be difficult to sufficiently shorten the time for removing the residual stress.
In addition, it is more preferable that the vacuum state is a degree of vacuum of a pressure of 5 × 10 ⁻³ Pa or less.
From the viewpoint of the time required for the evacuation step, the pressure in the vacuum state is preferably 1 × 10 ⁻⁴ Pa or more.

Moreover, it is preferable that the heating temperature in the said heating process is less than the secondary transition temperature of the said resin film (Claim 4).
In this case, it is possible to prevent the resin film from being deformed by the heat treatment, and for example, it is possible to prevent the occurrence of distorted skin, craters, etc. on the surface of the resin film. Since the present invention maintains a vacuum state in the heating process as described above, heat treatment at a relatively low temperature is possible due to the boiling point effect, and effective heat treatment at a temperature sufficiently lower than the secondary transition temperature of the resin film. It is easy to be able to do.

Example 1
A resin film heat treatment method according to an embodiment of the present invention will be described with reference to FIG.
The heat treatment method of the resin film of this example is a method of heat-treating the resin film 2 so as to remove the residual stress of the resin film 2, and includes the following film placement step, vacuum drawing step, heating step, and cooling step. Have.

In the film placement step, a resin film is placed in the chamber 11.
Next, in the evacuation step, the chamber 11 is evacuated.
Next, in the heating step, the resin film 2 is heated.
Next, in the cooling step, the resin film 2 is cooled.
Then, during the period from the heating step to the cooling step, a state where no tension is applied to the resin film 2 (a tension-free state) and a vacuum state in the chamber 11 are maintained.

For the heat treatment method of the resin film, a heat treatment apparatus 1 as shown in FIG. 1 is used.
The heat treatment apparatus 1 includes a delivery roller 121 and a take-up roller 122 in the chamber 11, and the resin film 2 is wound around these. In the vicinity of each of the feed roller 121 and the take-up roller 122, an auxiliary roller 123 for normally operating the resin film 2 is disposed, and the resin film 2 is sent out at a correct position so that the resin film 2 is not displaced or loosened. It is made to wind up. A pair of support rollers 124 for supporting the resin film 2 is disposed above the feed roller 121 and the take-up roller 122. On the upper side of each support roller 124, a pressing roller 125 that sandwiches the resin film 2 with the support roller 124 is disposed.

  A preheating part 131 for preheating the resin film 2 and a heating part 132 for heating the resin film 2 are disposed below the support roller 124 on the side close to the feed roller 121. In addition, a cooling unit 133 for cooling the resin film 2 is disposed below the support roller 124 on the side close to the winding roller 122.

In the film placement step, the feed roller 121 around which the resin film 2 is wound is set in the chamber 11 of the heat treatment apparatus 1, and the resin film 2 is appropriately locked to the auxiliary roller 123 and the support roller 124. One end is attached to the winding roller 122. At this time, the resin film 2 is arranged so that the resin film 2 delivered from the delivery roller 121 sequentially passes through the preheating unit 131, the heating unit 132, and the cooling unit 133. And the resin film 2 arrange | positioned between a pair of support rollers 124 is in the state which hung down from a pair of support rollers 124, and exists in the state which forces other than self-weight do not act. That is, the resin film 2 is in a so-called tension-free state where substantially no tension is applied.
This tension-free state can be maintained by appropriately controlling the rotation of the feed roller 121 and the take-up roller 122.
In this example, the resin film 2 is a biaxially stretched PET film having a hard coat layer made of an ultraviolet curable coating film on one side and having a thickness of 175 μm.

Next, in the evacuation step, the chamber 11 is evacuated to a vacuum state. At this time, the degree of vacuum is set to 1 × 10 ^{−4 to} 5 × 10 ⁻² Pa. In this example, it was set to 5 × 10 ⁻² Pa.
Next, the film 2 is moved from the feed roller 121 to the take-up roller 122 at a constant speed by rotating the take-up roller 122 and the feed roller 121. Here, the preheating temperature by the preheating unit 131 is 170 ° C., and the main heating temperature by the heating unit 132 is 150 ° C. Thereby, in the heating part 132, the resin film 2 is heat-processed for 150 degreeC x 2 minutes. In the cooling unit 133, the resin film 2 is cooled by water cooling at a water temperature of 20 ° C. While passing through the cooling section 133, the resin film 2 is cooled to near room temperature (about 30 ° C.). Then, the cooled resin film 2 is wound around the take-up roller 122.

150 degreeC which is the heating temperature in a heating process is less than the secondary transition temperature (160 degreeC) of the resin film 2, ie, biaxially stretched PET.
During the period from the main heating (heating step) in the heating unit 132 to the cooling (cooling step) by the cooling unit 133, the resin film 2 is kept in a state where no tension is applied.

  The wound heat-treated resin film 2 is put into a sputtering apparatus, and a transparent conductive film such as ITO is formed on the surface thereof, whereby a high-performance transparent conductive film can be produced. Such a transparent conductive film can be used for a touch panel, for example.

Next, the function and effect of this example will be described.
In the heat treatment method for the resin film, a state where no tension is applied to the resin film 2 (tension-free state) and a vacuum state in the chamber 11 are maintained from the heating step to the cooling step. Thereby, the removal of the residual stress in the resin film 2, dehydration, degassing, and solvent removal can be performed efficiently. Further, when an ITO film, for example, is formed on the resin film 2, crystallization of the ITO film can be promoted.

  That is, by performing the heating process while maintaining the vacuum state in the chamber 11, moisture, gas, solvent and the like in the resin film 2 can be effectively removed in a short time. Moreover, the residual stress in the resin film 2 can be removed in a short time. Further, when an ITO film, for example, is formed on the resin film 2, crystallization of the ITO film can be promoted. Accordingly, the chamber 11 can be downsized, and the heat treatment apparatus 1 can be downsized.

  Further, in order to maintain a state where the resin film 2 is not tensioned (a tension-free state) from the heating step to the cooling step, the residual stress is removed without external force acting on the resin film 2. The flatness of the surface can be ensured. In addition, since the cooling process is performed in a state in which no tension is applied to the resin film 2, there is little distortion left as a residual stress in the resin film 2 due to cooling, and the flatness of the surface of the resin film 2 is ensured. Can do.

  Moreover, since the heating temperature in a heating process is less than the secondary transition temperature of the resin film 2, it can prevent that the resin film 2 deform | transforms by heat processing, for example, can prevent that a skin skin, a crater, etc. generate | occur | produce. In addition, since the heat treatment method of this example maintains a vacuum state in the heating process, heat treatment can be performed at a relatively low temperature, and effective heat treatment can be performed at a temperature sufficiently lower than the secondary transition temperature of the resin film 2. Is likely to be possible.

  As described above, according to this example, it is possible to provide a heat treatment method for a resin film that can efficiently perform removal of residual stress, dehydration, degassing, and solvent removal in the resin film.

In addition, about the resin film 2 processed by the heat processing method shown in the said Example 1, when the change of the moisture content in a film and the change of a heat contraction rate were measured, the following results were obtained.
That is, the moisture content before treatment was 0.5% by weight, whereas the moisture content after treatment was greatly reduced to 0.04% by weight or less. Further, the heat shrinkage rate before the treatment was 0.5%, whereas the heat shrinkage rate after the treatment was greatly reduced to 0.05% or less. Here, the heat shrinkage rate is a value obtained by measuring a dimensional change when the resin film before and after the treatment by the heat treatment method is heat-treated in a heating furnace at 150 ° C. for 60 minutes with a highly accurate dimension measuring instrument.

(Experimental example 1)
In this example, as shown in FIG. 2, the heat treatment method for the resin film of the present invention shown in Example 1 above and the heat treatment method for applying hot air to the resin film in the atmosphere (the method described in Patent Document 1: Comparative Example 1) ), And a comparison of changes in the amount of water in the resin film before and after treatment.
In any method, the water content before the treatment was 0.28% by weight. The heating temperature was 150 ° C., and the heating time was variously changed.

And the moisture content in the resin film after performing each heat processing is shown in the graph of FIG. In the figure, the curve indicated by reference numeral E1 indicates the result after the heat treatment of Example 1, and the curve indicated by reference numeral C1 indicates the result after the heat treatment of Comparative Example 1. As can be seen from the figure, the water content after heat treatment of Example 1 decreases in a very short time compared to that after heat treatment of Comparative Example 1.
That is, according to the heat treatment method of Example 1, it can be seen that moisture can be sufficiently removed even if the heat treatment time is significantly shortened.

(Experimental example 2)
As shown in FIG. 3, this example is a resin film heat treatment method according to the present invention shown in Example 1 above and a heat treatment method in which hot air is applied to the resin film in the atmosphere (Comparative Example 1). It is the example which compared the reduction effect of the residual stress.

  FIG. 3 shows the relationship between the heating temperature during the heat treatment and the heat shrinkage rate of the resin film after the treatment, for the sample according to Comparative Example 1 (C21 to C24) and the sample according to the present invention (Example 1), respectively. As a result (E2). In the figure, the curve with the symbol E2 is the result for the sample according to the present invention (Example 1), and the processing time is 1 minute. The curve with the symbol C21 is the result for the sample subjected to the heat treatment of Comparative Example 1 for 1 minute, and the curve with the symbol C22 is the result for the sample subjected to the heat treatment of Comparative Example 1 for 10 minutes. The curve with the symbol C23 is the result for the sample that was subjected to the heat treatment of Comparative Example 1 for 30 minutes, and the curve with the symbol C24 is the result for the sample that was subjected to the heat treatment of Comparative Example 1 for 60 minutes. is there.

As can be seen from the figure, when compared at the same processing time (1 minute), the sample (E2) after the heat treatment of the present invention (Example 1) is better than the sample (C21) after the heat treatment of Comparative Example 1. The heat shrinkage rate can be greatly reduced. In addition, even when comparing the time required to reduce the thermal shrinkage rate to a certain level (for example, less than 0.10%), the present invention (E2) is compared to Comparative Example 1 (C22 to C24). It is extremely short time.
That is, according to the present invention (Example 1), it was confirmed that the residual stress can be reduced in a very short time.
That is, it can be seen that the present invention can greatly shorten the processing time as compared with the method of heat treatment in the atmosphere.

(Example 2)
This example is an example of a method of heat-treating the resin film 2 after forming a transparent conductive film on one surface.
Specifically, a heat treatment apparatus 1 is formed by sputtering a transparent conductive film made of ITO on one side of a biaxially stretched PET film provided with a hard coat layer made of an ultraviolet curable coating film on the other side. Set to. The thickness of the PET film is 125 μm.
Then, heat treatment was performed under the same conditions as in Example 1.
Others are the same as in the first embodiment.

When the change in the surface resistance value of the transparent conductive film and the change in the etching time due to immersion in a 5% HCl aqueous solution were measured for the resin film 2 treated by the heat treatment method of this example, the following results were obtained. It was.
That is, the surface resistance value before the heat treatment was 300Ω / □, whereas the surface resistance value after the heat treatment was reduced to 170Ω / □. The etching time before the heat treatment was 1 minute or less, whereas the etching time after the heat treatment was greatly extended to 10 minutes or more. That is, by performing the heat treatment of this example, the surface resistance of the transparent conductive film can be lowered and the durability of the transparent conductive film can be improved.
In addition, the same effects as those of the first embodiment are obtained.

(Experimental example 3)
In this example, it was confirmed that crystallization of the transparent conductive film was promoted by the heat treatment method shown in Example 2 as shown in FIG.
That is, the crystal growth of the transparent conductive film (ITO) before and after the heat treatment shown in Example 2 was confirmed by X-ray diffraction. The heat treatment was performed at 150 ° C. for 2 minutes.

The X-ray diffraction data of the transparent conductive film before and after the heat treatment is shown in FIG. In the figure, the curve with the symbol C3 is the data before the heat treatment, and the curve with the symbol E3 is the data after the heat treatment. As can be seen from the figure, the diffraction peak is not particularly shown in the data (C3) before the heat treatment, but the data (E3) after the heat treatment shows that In ₂ O in the (222) plane and the (400) plane. ₃ peaks appear. That is, it can be seen that the crystallization of ITO is progressing by the heat treatment of Example 2.
(Experimental example 4)
In this example, the degree of crystallization of the ITO film was observed with an SEM (scanning microscope) in the same sample as in Experimental Example 3. The results are shown in FIGS. 5 (A) and 5 (B). The SEM photograph shown in FIG. 5 (A) is an untreated product, and the SEM photograph of this sample that was vacuum heat treated by the heat treatment method of the present invention (Example 2) is shown in FIG. 5 (A). is there.

In the photograph of the untreated product (FIG. 5 (A)), the crystal parts of the ITO particles are scattered in small white dots, but in the photograph of the treated product (FIG. 5 (B)), the ITO film is greatly crystallized. It is recognized that white spots are growing greatly. And the thing after a process (FIG.5 (B)) will also be in the state where the surface state was a little rough, and it turns out that the crystal grain is growing large.
From this result, it is understood that crystallization of the transparent conductive film can be greatly promoted by performing the heat treatment by the heat treatment method of the present invention.

  In addition, the heat processing method of the resin film concerning this invention is not only when heat-treating the resin film which forms a transparent conductive film as shown in Example 1, 2, but the application | coating of the adhesive agent to a resin film, resin films It can be used for various purposes such as pretreatment such as adhesion.

DESCRIPTION OF SYMBOLS 1 Heat processing apparatus 11 Chamber 2 Resin film

Claims (4)

A method of heat treating the resin film so as to remove the residual stress of the resin film,
A film placement step of placing the resin film in a chamber;
Next, a evacuation step for evacuating the chamber;
Next, a heating step for heating the resin film;
Next, a cooling step for cooling the resin film,
A method for heat-treating a resin film, comprising maintaining a state in which no tension is applied to the resin film and a vacuum state in the chamber from the heating step to the cooling step.   The method for producing a resin film according to claim 1, wherein a transparent conductive film is formed on at least one surface of the resin film. 3. The method for heat-treating a resin film according to claim 1, wherein the vacuum state is a degree of vacuum of a pressure of 5 × 10 ⁻² Pa or less.   The method for producing a resin film according to any one of claims 1 to 3, wherein a heating temperature in the heating step is lower than a secondary transition temperature of the resin film.