JPH0519899B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application) The present invention relates to a method for heat treating a long film to obtain a film having excellent dimensional stability when heated. It is particularly useful for heat treatment of plastic films laminated with functional thin films such as photo-selective films and transparent conductive films used for optical and electrical applications, allowing long films with excellent dimensional stability under heat to be obtained. .

(Prior Art) The heat treatment method for a film differs depending on the length of the film. As a method of heat treating a relatively short film, the film is continuously treated at a low speed in a continuous tunnel furnace. A film is wound relatively loosely and then heat-treated in a heating furnace as it is (e.g., JP-A No. 58-98219). A rolled film with a spacer interposed between the wound layers is heat-treated in a heating furnace (e.g., JP-A-60-1999). 82338) are known, but each of the above-mentioned conventional methods has the following problems. This method is effective if the heat treatment time is between a few minutes and several tens of minutes, but that time is usually insufficient, and the longer the heat treatment time, the longer the heating furnace, and the loss during handling of the film. Moreover, the manufacturing cost of the heating furnace also increases. In the method described above, it is difficult to wind the film loosely when the film is long, and scratches are likely to occur due to miswinding. The method described above overcomes the problems of the method described above, but since there is an air layer between the films, heat conduction between each film is slow and it takes time for the temperature of the entire rolled film to rise. That is, a temperature distribution occurs in the length direction of the wound film, and it takes a long time for the entire film to reach a uniform temperature. For this reason, in the length direction of the film, there is a large difference in heat treatment temperature and time between the winding start part, the central part, and the winding end part. Also, the film can have different dimensional stability when heated in the longitudinal direction of the film. That is, there is a problem in that it is difficult to uniformly heat treat the entire film.

Therefore, as a heat treatment method for a relatively long film, the above-mentioned method is generally used as long as the heat treatment time is short. However, no useful method has yet been found for those that require a long heat treatment time. Whatever method is used, it is necessary to avoid deformation, blocking, scratches, etc. due to thermal shrinkage of the film.

(Object of the invention) The present invention was made in view of the current situation,
Deformation and blocking due to film heat shrinkage,
The object of the present invention is to provide a method for heat-treating a long film that does not cause scratches, can be heat-treated uniformly in the longitudinal direction, and can produce a good film.

(Structure and operation of the invention) The above-mentioned object is achieved by the following present invention.
That is, the present invention provides a film heat treatment method in which the film is unwound by a roll of the film maintained at a holding temperature lower than the heat treatment temperature and guided into a heat treatment furnace maintained at the heat treatment temperature. While heating the film to
This method of heat treating a film is characterized in that the film heated in the heat treatment furnace is continuously wound onto a roll with a spacer interposed therebetween, and then the roll with spacers is held at a heat treatment temperature for a predetermined period of time for heat treatment.

As mentioned above, in the present invention, a spacer is interposed between the wound layers of the film to prevent blocking between the films.
In addition to preventing the occurrence of scratches, the film on the unwinding side is held at a holding temperature below the heat treatment temperature to eliminate the effect of heat on the roll at the unwinding section, and the film is kept at a temperature below the heat treatment temperature. By inserting spacers along both ends of the film between the wound layers while heating and winding the film into a roll, hot air at the same temperature as the heat treatment temperature is drawn between the films, so that the temperature between the wound layers of the film is An ideal heat treatment condition that is uniform and uniform in the length direction is achieved.

Further, when the film is heated to a heat treatment temperature after being wound, by continuing to rotate the winding side, deformation and blocking due to sagging of the film can be prevented, and better heat treatment can be achieved.

Note that a higher holding temperature is preferable from the viewpoint of reducing the temperature difference when entering the heat treatment furnace and the heating time in the heat treatment furnace, but a lower holding temperature is preferable from the viewpoint of thermal deformation in the rolls during unwinding. Preferably, the temperature is selected so as not to substantially affect the quality of the film during unwinding (such as the occurrence of scratches).
From this point of view, the holding temperature is selected to be below the glass transition temperature of the film to be processed. A preheating furnace that blows hot air or the like can be used as a means for maintaining the holding temperature, but this is not necessary if the holding temperature can be kept at atmospheric temperature.

The present invention described above involves heat treatment to adjust the thermal properties of the film itself, such as plastic film, which will be described later, or by using these films as a substrate and applying vacuum evaporation, sputtering, chemical coating, etc., to form a transparent conductive film and photo-selection. In order to improve the electrical properties, optical properties, mechanical properties, heat resistance, humidity resistance, etc. of a film on which a functional thin film such as a functional film is formed, it is necessary to maintain a predetermined processing temperature for a predetermined period of time or longer. Applicable to general heat treatment. This is particularly advantageous for heat treatments that require a long heat treatment time, such as transparent conductive films shown in Examples below. Therefore, the film to which the present invention can be applied is not particularly limited as long as it can withstand the above-mentioned heat treatment, and includes the following plastic film or a film in which a functional thin film is laminated thereon using the plastic film as a substrate.

Examples include polyethylene terephthalate film, polyethylene naphthalate film, polystyrene film, polycarbonate film, triacetate film, polysulfon film, polyether sulfon film, polyimide film, polyamide-imide film, etc.; Polyethylene terephthalate film is preferably used from the viewpoint of thermal dimensional stability and the like.

Hereinafter, details of the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an apparatus used in an embodiment of the present invention. In FIG. 1, 1 is the roll of film on the unwinding side, 2 is the spacer installed at both ends of the film, and 3 is the roll wound up with the spacer 2 interposed as shown in FIG. 4
A indicates a preheating furnace, and 4b indicates a heat treatment furnace. The preheating furnace 4a and the heat treatment furnace 4b are well-known hot blast furnaces whose temperatures can be controlled independently. Roll 1 of film 1 that has been subjected to prescribed processing and wound up
A is attached to the unwinding part of the preheating chamber 4a, and the rolls 2a of the spacers 2 to be installed at both ends of the film are similarly attached. There are no particular restrictions on the spacer 2 as long as the spacing is constant, but if the film 1 to be heat-treated is subject to heat shrinkage, it is preferably the same as the film 1 to be heat-treated. In other words, if the spacer 2 is similar to the film 1 to be heat-treated, the heat shrinkage rate will be almost the same, and even if the spacer 2 is heat-shrinked due to heat treatment after winding, it is possible to minimize deformation due to unwinding or tightness of the winding. It is.

The film 1 sent out from the roll 1a on the unwinding side in the preheating furnace 4a is overlapped with the spacer 2 by the guide roll 5. In this case, the spacer 2 is in contact with the guide roll 5 and the film 1 to be heat-treated does not come into contact with it, so that the film 1 can be prevented from being scratched by the guide roll 5. The temperature of the film 1 and the spacer 2 entering the heat treatment furnace 4b rises to near the heat treatment temperature by the time they are wound up, so that heat shrinkage begins, and some degree of heat shrinkage has ended by the time they are wound up. Usually, a time period of 1 minute to 10 minutes is sufficient for this heat treatment.

Furthermore, as the width and thickness of the spacer 2 are increased, the gap between the film surfaces becomes larger, which is advantageous, and the cutting width at the end of the film for removing the spacer 2 after the heat treatment is increased. The loss in the width direction of film roll 3 increases, and
This is disadvantageous because the diameter of the Therefore, the width of spacer 2 is 1/10 to 1/50 of the film width, and the thickness is 50μ.
It is preferable to set it as m - 500 micrometers. Incidentally, when the width of the film 1 is wide, the spacer 2 may be provided not only at both ends but also at the middle part thereof. Further, the spacer 2 may have the above-mentioned thickness and be made uneven by knurling or the like so that the air between the films of the film roll 3 can be slightly vented to the outside.

Incidentally, the film 1 and the spacer 2 may be subjected to a conventional pretreatment or coating in order to suppress the generation of oligomers and the like.

The temperature at which the heat treatment is performed is appropriately selected depending on the purpose of the heat treatment. When the film 1 includes a plastic film, any temperature may be used as long as it exceeds the glass transition point of the plastic film, but in the case of polyethylene terephthalate, the temperature is usually 120°C or more and 180°C or less. Further, the time required for heat treatment of the wound film roll 3 varies depending on the purpose, and the higher the heat treatment temperature, the shorter the time required, but it is usually 30 minutes or more. That is, the time and temperature of the heat treatment are appropriately selected experimentally depending on the object, specifically the film to be heat treated, for example, the material of the thin film processed thereon.

If the holding temperature of the preheating furnace 4a is lower than the temperature of the heat treatment furnace 4b, it is possible to minimize scratches and scratches caused by the rapid heating of the film roll 1a without causing any practical problems, but this depends on the holding time. Preferably, the time required for all of the film on the unwinding side to be fed out is within 2 hours. This is because after two hours or more, the film on the unwinding side begins to shrink due to heat, resulting in a large number of scratches. Note that this problem does not occur when the holding temperature is below the glass transition point of the film.

The present invention will be explained below with reference to Examples.

Example 1 A biaxially stretched polyethylene terephthalate film having a width of 400 mm and a thickness of 100 μm was placed in a vacuum deposition apparatus, and the vacuum chamber was evacuated until the degree of vacuum reached 1×10 ⁻⁵ Torr. Then In ₂ O ₃ /SnO ₂ (SnO ₂ 5wt%)
A 200 m long film 1 was prepared by heating and evaporating with an electron beam to form an indium tin oxide film.

Spacer 2 is a roll of polyethylene terephthalate film with a thickness of 125 μm and a width of 15 mm.
I prepared by winding up 200m.

The roll 1a of the film 1 on which the indium tin oxide film is formed is attached to the unwinding shaft 1b, the roll 2a of the spacer 2 is attached to the spacer attachment shaft 2b, and the film is rolled up to the winding shaft 3a of a winder (not shown). 1 was taken out and installed, and the temperature of the preheating furnace 4a was controlled at 110°C to enable continuous winding.

Next, when the temperature of the heat treatment furnace 4b rose to 140°C, the winding machine was rotated to heat the film and wind it onto the roll 3. The film 1 entered the heat treatment furnace 4b and was rewound for about 1 hour, with the time until it was wound up being 1 minute. The film entered the heat treatment furnace 4b and its surface temperature reached 138°C within 1 minute.

After winding, the film roll 3 is further heat treated at 140°C for 24 hours (in this case, the winder was not rotated), the heat treatment furnace 4b is cooled, and the film roll 3 is heated.
The film was taken out and both ends of the film were cut to a width of 25 mm using a winding machine with a slitter to remove the spacers and the deformation and dirt on the ends of the film caused by the spacers.

The transparent conductive film thus obtained had good surface resistance, surface resistance linearity, and transmittance with little variation over the entire length and width directions of the film. Further, when the appearance was inspected, no scratches were observed and the appearance was good.

Film length direction (MD) and width direction (TD)
When heated at 120℃ for 30 minutes, the heat shrinkage rates of the films used were 0.9% and 0.8%, respectively, and after heat treatment they were 0.1% and 0.1% or less, respectively, and at any point along the length of the film. It was within this range.

Example 2 In exactly the same manner as in Example 1, the same film 1 and spacer 2 were set in the preheating furnace 4a for 200 m each, and taken out up to the winding shaft 3a, and placed in the preheating furnace 4a.
The temperature was controlled at an atmospheric temperature of 30°C, which is below the glass transition temperature.

Next, the temperature of the heat treatment furnace 4b is raised to 140°C, and the winding machine is rotated to heat the roll 3.
rolled up. The time from when the film 1 enters the heat treatment furnace 4b to when it is wound up is approximately 2 minutes.
I took my time and recovered. The film surface temperature reached 138°C within 1 minute after entering the heating oven.

After winding was completed, heat treatment was performed in exactly the same manner as in Example 1, and the spacers 2 were removed.

The transparent conductive film thus obtained had good surface resistance, surface resistance linearity, and transmittance with little variation throughout the length and width directions of the film, as in Example 1. Further, when the appearance was inspected, no scratches were observed and the appearance was good. Moreover, its thermal shrinkage rate was exactly the same as that of Example 1 and was good.

(Comparative example) Film prepared in the same manner as Examples 1 and 2
200m and spacer (width: 15mm, thickness 125μm, length
200 m) was wound up in the same manner as in Example 1, with the temperatures of both the preheating furnace 4a and the heat treatment furnace 4b set at 30°C. Thereafter, the temperature of the heat treatment furnace 4b was set at 140° C., and heat treatment was performed for 24 hours.

The cutting width at both ends of the obtained film for spacer removal is due to deformation due to heat shrinkage of the film.
It had to be 30mm, which resulted in a large loss.

In addition, the surface resistance value after heat treatment was almost the same for the outermost and innermost sides of the film in the rolled state during heat treatment, approximately 6 cm from both ends in the width direction of the film. The surface resistance value of the center part of the width excluding both ends and the center part of the winding is 1.5 at the outermost circumference.
The width was more than twice as large, and the variation in the width direction was also very large at the center. This is because during heat treatment, the temperature at the center of the wound film in the length and width directions rose slowly, and did not rise sufficiently within 24 hours, resulting in insufficient heat treatment. Further, thin scratches were generated throughout the length of the film, and the film was poor in terms of appearance and quality.

In addition, the dimensional stability when heated is 0.9% and 0.8% for the film used at the aforementioned heat shrinkage rates in the MD and TD directions, respectively, and after heat treatment, it is 0.1% at the outermost and innermost peripheries in the length direction, respectively. % and 0.1 or less, but in the central part it was 0.4% and 0.4%, indicating that the heat treatment was insufficient.

Although the present invention has been described above in detail with reference to examples, the present invention is not limited to these examples.

[Brief explanation of drawings]

FIG. 1 is an explanatory view of a film heat treatment apparatus used in an embodiment of the present invention, and FIG. 2 is an explanatory cross-sectional view of a film roll on the winding side in FIG. 1. 1: film, 2: spacer, 4a: preheating furnace,
4b: Heat treatment furnace.

Claims (1)

[Claims] 1. In a film heat treatment method, the film is unwound from a roll of the film maintained at a holding temperature lower than the heat treatment temperature, and introduced into a heat treatment furnace maintained at the heat treatment temperature. While heating to the heat treatment temperature, spacers are stacked on at least both ends of the film during that time, the heated film is continuously wound up in the heat treatment furnace onto a roll with spacers interposed therebetween, and then the spacer interposed roll is brought to a predetermined heat treatment temperature. A method for heat-treating a film, which is characterized by heat-treating the film by holding it for a period of time. 2. The method of heat treating a film according to claim 1, wherein the holding temperature is equal to or lower than the glass transition temperature of the film to be treated. 3. Claim 1, wherein the roll of film to be processed is held in a preheating furnace controlled at a holding temperature.
2. The method for heat treatment of a film according to item 1 or 2. 4. Claims 1 and 2, in which the spacer is stacked on the film before the film enters the heat treatment furnace.
The method for heat treatment of a film according to item 1 or 3. 5. The method of heat treating a film according to claim 1, 2, 3, or 4, wherein the spacer-interposed roll is rotated in the winding direction while being held at a heat treatment temperature for a predetermined period of time. 6. The method of heat treating a film according to claim 1, 2, 3, 4, or 5, wherein the film is a functional film in which a functional thin film is laminated on a plastic film.