JPS62127229A - Heat treatment of film - Google Patents

Abstract

PURPOSE:To manufacture a continuous film with excellent dimensional heat stability by a method wherein the film is picked up while being heat-treated under the state that a spacer is piled up to the film. CONSTITUTION:First, a film 1 and a spacer 2 are set in a preheating oven 4. The temperature in the preheating oven 4 is controlled to be at the atmospheric air temperature of 30 deg.C which is below the glass transition temperature of the film. Secondly, the temperature in a heat-treating oven 4b is raised so as to put a wind-up machine into rotation when said temperature reaches 140 deg.C in order to pick up the film under heat to a roll 3. The film 1 with 200m in length passes through the heat-treating oven 4b in 2min and is wound up to a wind-up shaft 3a by spending about 2hr. Finally, after the film is wound up, the spacer 2 is removed. The surface resistance value and the like of the obtained film are uniform. No scratch develops on the external surface. at the same time, the heat shrinkage factor of the obtained film is also small.

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 with 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 in optical and electrical applications, and long films with excellent dimensional stability in hot parts are available. ! 1 is a monkey.

(Prior Art) The heat treatment method for a film differs depending on the length of the film. As a heat treatment method for relatively short films, (1) Continuous treatment at low speed in a continuous tunnel furnace. ■ Roll the film relatively loosely and heat-treat it in a heating oven (for example, Japanese Patent Application Laid-Open No. 58-98219). ■ Heat-treat the rolled film in a heating furnace without intervening a spacer between the wound layers (for example, Japanese Patent Application Laid-Open No. 1987-98219). 60-823
Seven methods are known, such as Japanese Patent No. 38), but each of the above-mentioned conventional methods has the following problems. Method (2) is effective if the heat treatment time is from a few minutes to 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. This also increases the manufacturing cost of the heating furnace.

With method (2), it is difficult to wind the film loosely when the film is long, and it is also easy to cause misalignment (slips, etc.).Method (2) overcomes the problems of method (2), but
Since there is an air layer between the films, heat conduction between the films 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, the difference in heat treatment temperature and time between the beginning of winding and the central part 9 and the end of winding increases in the film's thickness direction. Also, the dimensional stability of the hot part of the film can differ in the length direction of the film. In other words, there is a problem in that uniform heat treatment over the entire film is difficult.

Therefore, as a heat treatment method for a relatively long film 11,
For short heat treatment times, the method (2) described above is generally used. However, no useful method has yet been found for a method that requires a good heat treatment time. Whatever method is used, it is necessary to avoid deformation, blocking, scratches, etc. due to thermal shrinkage of the film.

(Objective of the Invention) The present invention has been made in view of the current situation, and is aimed at preventing deformation and blocking due to heat shrinkage of the film.

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 objects are achieved by the invention as follows.

- However, the present invention provides a method for heat treating a film,
The film is unwound from the roll of the film held at a holding temperature lower than the heat treatment temperature and transferred to a heat treatment furnace maintained at the heat treatment temperature, and heated to approximately the heat treatment temperature in the heat treatment furnace, while at least A film characterized by stacking spacers on both ends, continuously winding up the film heated in the heat treatment furnace onto a roll with spacers interposed therebetween, and then heat-treating the film by holding the spacer-interposed roll at the heat treatment temperature for a predetermined period of time. This is a heat treatment method.

As mentioned above, in the present invention, a spacer is interposed between the film winding layers to achieve blocking between the films.

In addition to preventing the occurrence of scratches, the film on the unwinding side is maintained at a holding temperature below the temperature for heat treatment to eliminate the effect of heat on the roll at the unwinding section, and at the same time the film is kept at a temperature below the temperature for heat treatment. 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 the temperature between the wound layers of the film is uniform. Thus, an ideal heat treatment condition that is uniform in the length direction is achieved.

Further, when maintaining the reheating treatment temperature at which the film is 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 performed.

Note that a higher holding temperature is preferable from the viewpoint of reducing the temperature difference when entering the heat treatment furnace and during heating in the heat treatment furnace, but it is lower from the viewpoint of thermal deformation in the rolls during exposure. The temperature is preferably selected at a temperature that does not substantially affect the quality of the film being exposed (such as the occurrence of scratches).

From this point of view, the holding temperature is selected to be below the glass transition fAα 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.

(a) The present invention (e) involves heat treatment to adjust the thermal tenacity of the film itself, such as a plastic film described below, or a transparent conductive film is applied to the film as a substrate by vacuum evaporation, sputtering, chemical coating, etc. Electrical properties and optical properties of films with functional thin films such as membranes and photo-selective films 2 Heat treatment to improve mechanical properties, heat resistance, humidity resistance, etc. Applicable to general heat treatment that needs to be maintained. This is particularly advantageous for heat treatment that requires a long heat treatment time, such as a transparent conductive film shown in Examples below. Therefore, the film to which the present invention can be applied is not particularly limited to υj as long as it can withstand the above-mentioned heat treatment, and may include a plastic film or a film in which a functional thin film is laminated on top of the plastic film as a substrate.

For example, polyethylene terephthalate film.

Examples include poly-[tyrene naphthalate film, polystyrene film, polycarbonate film, l-lyacetate film, polysulfone film, polyether sulfone film, polyimide film, polyamide-imide film, etc., but heat resistance, humidity resistance, thermal dimension Polyethylene terephthalate film is preferably used from the viewpoint of stability.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an apparatus used in an embodiment of the present invention.

In Figure 1, 1 is the roll of the unrolled copper film, 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 Figure 2. , 4a represents a preheating furnace, and 4b represents a heat treatment furnace. The preheating furnace 4a and the heat treatment furnace 4b are well-known hot blast furnaces, and the temperatures i and II 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 O-ru 2a of the spacer 2 to be installed at both ends of the film is similarly attached. There are no particular restrictions on the spacers 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 type as the film 1 to be heat-treated. That is, if the spacer 2 is of the same type as 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, deformation due to unrolling or tightness of the winding can be minimized. It is possible.

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, since it is the spacer 2 that contacts the guide roll 5 and the film 1 to be heat treated does not come into contact with it, it is possible to prevent the film 1 from being scratched by the idle roll 5. The temperature of the film 1 and spacer 2 that have entered the heat treatment furnace 4b rises to nearly LgIm (degrees) before being wound up, so heat shrinkage begins, and some degree of heat shrinkage has already been completed by the time the film is wound up. A heat treatment time of 1 minute to 10 minutes is sufficient.

Further, the larger the width and thickness of the spacer 2, the larger the distance between the film surfaces, which is advantageous, but the cutting of the film end to remove the spacer 2 after the heat treatment is completed increases. The loss in the 1] direction of the film increases,
Moreover, the diameter of the film roll 3 increases, which is disadvantageous. Therefore, the width of spacer 2 is 1/10 to 11 of the film width.
50. The thickness is preferably 50 μm to 500 μm. Note that 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. 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 ventilated 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 rapid heating of the film roll 1a without causing any practical problems. Depending on the situation, the time it takes for all of the film on the unwinding side to be fed out should be within 2 hours. This is because if the unwinding time exceeds 2 hours, the film on the unwinding side will start 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 two-wheel stretched polyethylene terephthalate film having a width of 400 am and a thickness of 100 μm was placed in a vacuum evaporation apparatus, and the vacuum chamber was evacuated until the degree of vacuum reached I x 10" T Orr. Thereafter, In 203/31102 (Sn
025wt%) was heated and evaporated with an electron beam to form an indium tin oxide film].
ti-biased.

Spacer 2 has a thickness of 125 μm and a width of 15. A polyethylene terephthalate film was prepared by winding it into a roll of 200 m.

Film 1 with the above-mentioned indium tin oxide film formed
The roll 1a of the spacer 2 is attached to the unwinding shaft 1b, the roll 2a of the spacer 2 is attached to the shaft 2b, the film 1 is taken out to the winding shaft 3a of the winder (not shown), and the roll 2a of the spacer 2 is attached to the preheating furnace 4a. The temperature 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 a time of 19 hours until it was rewound. The film entered the heat treatment furnace 4b and the film surface temperature reached 138° C. within 1 minute.

After winding was completed, the film was further treated at 140°C for 24 hours (in this case, the rotation of the winder was stopped), the heat treatment furnace 4b was cooled, and the film roll 3 was taken out and passed through a winder with a slitter. The width of both ends of the film is 251 mm.
The film was cut with 1Il to remove the substrate and the deformation and dirt on the edges of the film caused by the spacer.

The transparent conductive film thus obtained had good surface resistance value of 9, surface resistance linearity, and transmittance with little variation over the entire length and width directions of the film.

Further, when the external appearance was inspected, no scratches were observed and the external appearance was good.

12 in the length direction (MD) and width direction (TD) of the film
The heat shrinkage rates of the used films when heated for 30 minutes at 0°C were 0.9% and 0.8%, respectively, and after heat treatment they were 0.1% and 0.1% or less, respectively, and the film length Both locations in the horizontal direction were within this range.

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

Next, the temperature of the heat treatment furnace 4b was raised to 140°C, and 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 C for about 20.1 minutes, with the time until it was wound up being 2 minutes.

Note that the film surface (temperature reached 138° C.) within 1 minute after entering the heating oven.

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

As in Example 1, the transparent conductive film obtained in this manner had good surface resistance value, surface resistance linearity, and transmittance with little variation in the entire length direction and 11] direction of the film. Ta. Further, when the external appearance was inspected, no scratches were observed and the external appearance was good. Further, its heat shrinkage rate was exactly the same as that of Example 1 and was good.

(Comparative example) 200 m of film prepared in the same manner as in Example 1.2 and spacer (++3: 15 #I, thickness 125 μm,
The film having a thickness of 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. After that, the temperature of the heat treatment furnace 4b was set to 140°C.
Heat treatment was performed for 4 hours.

The cutting 19 at both ends of the resulting film for removing the spacer had to be cut to 30#I due to deformation due to heat shrinkage of the film, resulting in a large loss.

In addition, the surface resistance value after heat treatment is 11 for the outermost and innermost sides of the film in the heat-treated +15 rolled state.
] The surface resistance value of about 6 pieces from both ends in the direction was almost the same /υ, but the surface resistance value of the center part excluding both ends of the width and the center part of the winding was 1.5 times that of the outermost circumference. In addition, there was a very large variation in the width direction at the center. This is because during heat treatment, the temperature rise in the center of the wound film in the length and width directions was slow, and the temperature did not rise sufficiently within 24 hours, resulting in insufficient heat treatment. In addition, thin scratches were generated throughout the length of the film, and the film was of poor quality in terms of appearance and quality.

In addition, the dimensional stability of the hot part was 0.9% and 0 for the film used with the above-mentioned heat shrinkage rates in the MD and TD directions, respectively.
．． After heat treatment, it was 0.1% and 0.1% or less at the outermost and innermost peripheries in the length direction, respectively, but it was 0.4% and 0.4% at the center, This indicated that the heat treatment was insufficient.

Although the present invention has been explained in detail by examples above, the present invention
The present invention is not limited to such examples.

[Brief explanation of drawings]

FIG. 1 is an explanatory view of a film heat treatment apparatus used in an example 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 Patent applicant: Teijin Co., Ltd.
1 Figure 2

Claims (1)

[Claims] 1. In a method for heat treatment of a film, the film is unwound from a roll of the film held at a holding temperature lower than the heat treatment temperature, and introduced into a heat treatment furnace maintained at the heat treatment temperature, and in the heat treatment furnace. While heating to approximately the heat treatment temperature, spacers are stacked on at least both ends of the film in the meantime, the heated film in the heat treatment furnace is continuously wound onto a roll with spacers interposed therebetween, and then the spacer-interposed roll is heated to the heat treatment temperature. A method for heat treatment of a film, characterized in that the heat treatment is performed by holding the film for a predetermined period of time. 2. The method for heat treatment of a film according to claim 1, wherein the holding temperature is below the glass transition temperature of the film to be treated. 3. The method for heat treating a film according to claim 1 or 2, wherein the roll of film to be treated is held in a preheating furnace controlled at a holding temperature. 4. The method of heat treating a film according to claim 1, 2 or 3, wherein the spacer is placed on the film before the film enters the heat treatment furnace. 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 for heat treatment. 6. The method of heat treating a film according to claim 1, 2, 3, 4, or 5, wherein the film is a functional film obtained by laminating a functional thin film on a plastic film.