JP5465912B2 - Film production method - Google Patents

Description

  The present invention relates to a corona discharge treatment method for the purpose of surface modification of a film.

  As one of the film surface modification technologies, it is well known that the surface characteristics such as adhesive strength, printing characteristics and anti-fogging properties can be improved by irradiating the film surface with corona discharge. This method is the corona discharge treatment. The film production line is no exception. Normally, in a film production line in which a film that has been extruded, film-formed, or stretched is taken up by a take-up machine and then taken up in a roll by a take-up machine, the corona discharge treatment device is provided in the take-up machine, and the surface is modified inline. Quality processing is performed.

  A method of corona discharge treatment at substantially atmospheric pressure by applying a high voltage between a corona discharge electrode and a grounded opposing treatment roll to modify the film surface is generally well known. . (For example, Patent Document 1)

 FIG. 2 shows an example of a conventional corona discharge treatment apparatus. A treatment roll is disposed facing the corona discharge electrode, and a high frequency high voltage is applied between the corona discharge electrode and the treatment roll to form a corona discharge. The method of corona-treating the surface of the film which passes along the discharge gap of this corona discharge electrode and a process roll along a process roll is shown.

Japanese Examined Patent Publication No. 62-4058

  The purpose of corona treatment is to obtain a treatment effect only on one side of the film that was originally treated. However, the corona treatment has a weak corona treatment effect on the back side (non-treatment side) of the film that is unnecessary or difficult to treat. There are problems that occur. This phenomenon in which the back surface is processed is referred to as “back leakage (or back surface processing)”.

  The reason for this back leakage is that a slight amount of air is interposed between the film and the processing roll, and this ionization phenomenon occurs due to the voltage applied to the air in the thickness direction of the film. It is. This back-missed film is a problem in post-processing and practical use such as processing failure due to deterioration of slip performance of the non-processed surface expected in the converting process such as printing and laminating and inhibition of releasability of the non-processed surface. Happens.

  The main process factors are as follows: (1) The film take-up tension is weak. (2) The film is wrinkled before entering the treatment roll. (3) Wrinkles on the treatment roll do not escape due to charging. (4) It does not adhere to the processing roll due to the surface distortion of the film. (5) High surface frictional resistance. Etc. are considered. Since the wrinkled portion is lifted from the processing roll, there arises a problem that the back surface of the film that does not need to be processed is corona-treated. This is an unavoidable problem, especially for in-line production of wide films.

  This invention solves the said subject and provides the method of acquiring the effect of only one side by corona treatment, without making a back side.

  In order to solve the above problems, the present inventor has reached the present invention by using an electrode that does not cause corona discharge from the discharge electrode to the treatment roll side.

That is, the present invention is as follows.
(1) A discharge electrode for applying a high-frequency high voltage and a ground electrode covered with an insulator and electrically grounded, and using an electrode in which ground electrodes are evenly arranged on both sides near the tip of the discharge electrode A method for producing a film, comprising generating a streamer-like corona discharge and passing the film through the streamer corona discharge region to corona-treat the film surface.
(2) The method for producing a film as described in (1), wherein the discharge electrodes and the ground electrodes are alternately provided in a plurality of rows and subjected to multistage treatment.
(3) The film production method according to (1) or (2), wherein the film is a biaxially stretched film.

  According to the present invention, “back leakage” in which the back surface of the film is corona-treated can be prevented, and a uniform treatment effect can be obtained only on the corona-treated surface.

It is explanatory drawing which shows the electrode structure and discharge condition of this invention. It is the schematic of the conventional corona treatment apparatus. It is the schematic which shows the electrode used for the Example, and the discharge condition.

  Hereinafter, embodiments of the present invention will be described in detail.

  In the present invention, a discharge electrode that generates a corona discharge by applying a high-frequency high voltage, and a ground electrode that is covered with an insulator and electrically grounded, are equally grounded on both sides near the tip of the discharge electrode. It is most important to generate a streamer-like corona discharge using the arranged electrodes. As shown in FIG. 1, a dew-like corona is formed so that a flame is ejected from the tip of the discharge electrode by the equal arrangement of both electrodes. The Kashiko Corona is a growth of many streamers, and it provides a highly efficient corona treatment effect.

  In the present invention, the corona treatment is performed by passing the film through the streamer corona discharge region from which the depressor-like corona is ejected and bringing the streamer corona into contact with the film surface. The gap between the ground electrode and the film is preferably in the range of 3 to 10 mm.

  The corona treatment method according to the present invention does not require a treatment roll as a counter electrode in principle. It is possible to corona-treat a film that is not in contact with the roll running between the rolls, and the discharge electrode and the ground electrode for the film running on the treatment roll like a conventional corona treatment device Can also be corona treated. However, at this time, it is necessary to consider the insulation specifications sufficient for the treatment roll so that corona discharge does not occur from the discharge electrode to the treatment roll side.

  In a normal corona treatment apparatus, the treatment roll has an essential role of stably maintaining corona discharge. The insulator (dielectric) coated on the treatment roll is designed to have electrical characteristics having an impedance and a dielectric constant that are optimal for corona discharge. However, in the present invention, it is not allowed to discharge from the discharge electrode to the treatment roll side. Therefore, sufficient insulation specifications are necessary. As a material for the insulator, silicon rubber, hyperon rubber, EPT rubber or the like is preferably used, and at least the treatment roll surface is preferably coated with a thickness of 10 mm or more.

  The reason is that the discharge is not discharged from the discharge electrode to the treatment roll side, so that even if the film is lifted from the treatment roll, the ionization phenomenon on the back surface does not occur, so that only one side can be treated without leaving the back.

  As the discharge electrode in the present invention, an electrode having a sharp tip is used. As a material, stainless steel is preferable, and examples of the shape of the electrode include a needle, a blade, a knife edge, and a wire. The ground electrode is a metal electrode covered with an insulating material. As the insulating material, for example, a sleeve made of silicon rubber or Teflon (registered trademark), a glass tube, or a metal rod is directly coated with ceramic. Examples include those that are spray-coated.

  Furthermore, in the present invention, in order to uniformly treat the film surface, it is preferable to perform multistage treatment by alternately providing a plurality of rows of discharge electrodes and ground electrodes.

  The corona treatment in the present invention can be carried out by either an in-line treatment installed in a film production line or an off-line treatment in which a film once wound up in a roll is redrawn and treated, but from the viewpoint of industrial production efficiency. Inline processing is preferable.

  The present invention can also be applied to a biaxially stretched film production line involving a process of stretching after extrusion and film formation.

  The film take-up speed (processing speed) of the present invention can be processed at an arbitrary speed within the range of equipment capacity.

In the present invention, the discharge amount is usually 12 to 280 W / m ² / min.

  The present invention is applicable to the production of almost all plastic films such as polyolefin, polyamide, polyarylate, polysulfone, polyurethane, polyimide, polyester, polyethylene terephthalate and polycarbonate.

  Next, the present invention will be specifically described with reference to examples.

Example 1
A biaxially stretched nylon 6 film having a width of 1.5 m and a thickness of 10 μm was taken up at a speed of 100 m / min, subjected to corona treatment on the upper surface of the film with a corona treatment device, and wound into a roll. As the corona treatment apparatus, an apparatus in which eight rows of discharge electrodes are arranged as shown in FIG. 3 was used. The pitch between the corona discharge electrode and the ground electrode was set at an equal interval of 10 mm. The film running between the rolls was irradiated with corona discharge with a discharge gap of 5 mm.
Processing was performed at 40 W / m ² / min by applying electric power with a discharge amount of 6000 W. The wetting tension of the non-treated surface of the obtained film was 38 mN / m, and no back side was observed. The wetting tension of the treated surface was uniformly treated at 54 mN / m.

Example 2
The same corona treatment as in Example 1 was performed except that a treatment roll insulatively coated with a 10 mm thick hyperon rubber was used and the electrodes described in Example 1 were arranged in an arc shape.
The wetting tension of the non-treated surface of the obtained film was 38 mN / m, and no back side was observed. The wetting tension of the treated surface was uniformly treated at 54 mN / m.

Comparative Example 1
In the corona treatment apparatus, corona treatment was performed in the same manner as in Example 1 except that the discharge electrode was made of two aluminum 3-types made by Kasuga Denki, and a treatment roll coated with silicon rubber having a thickness of 4 mm was used as the counter electrode.
The treatment was performed at 24 W / m ² / min by applying electric power with a discharge amount of 3600 W. An irregular streak-like back side was observed on the back surface of the obtained film. The wetting tension of the non-processed surface was 38 to 44 mN / m, which was uneven.

[Evaluation of film]
(1) Wetting tension (mN / m)
Measured according to JIS K6768 (plastic-film and sheet-wetting tension test method).
About the non-processed surface, evaluation of variation in wet tension measurement values and visual observation of the back leakage pattern when the wetting reagent of the same test method was applied in a range of 200 mm × 200 mm were performed as the back leakage evaluation.

(2) Discharge amount (W / m ² / min)
The discharge amount (W / m ² / min) was calculated by dividing the corona treatment power amount (W) by the electrode width (m) and the film take-up speed (m / min).

DESCRIPTION OF SYMBOLS 1 Discharge electrode 2, 3 Ground electrode 4 Streamer corona area 5 High voltage power supply 6 Processing roll 7 Film passage line

Claims (3)

  It consists of a discharge electrode that applies high-frequency high voltage and a ground electrode that is covered with an insulator and is electrically grounded, and uses an electrode with ground electrodes evenly arranged on both sides near the tip of the discharge electrode. The film surface is corona-treated by generating a corona discharge and passing the film through the streamer corona discharge region.   The method for producing a film according to claim 1, wherein the discharge electrode and the ground electrode are alternately provided in a plurality of rows and subjected to multistage processing. The film manufacturing method according to claim 1, wherein the film is a biaxially stretched film.