JP6683097B2 - Method for producing multilayer film - Google Patents

Description

  The present invention relates to a method for producing a multilayer film.

  A multi-layer film having two or more layers is produced by applying a coating solution on the surface of a running strip-shaped substrate to form a coating layer, and drying the coating layer if necessary. This has been done conventionally. Then, in order to satisfactorily apply the coating liquid onto the surface of the base material, the surface of the base material is subjected to corona discharge treatment prior to coating to modify the surface. As a device for efficiently performing such a discharge treatment, a device for performing continuous treatment on a continuously conveyed long film is known (for example, Patent Document 1).

  Generally, corona discharge treatment requires the presence of a controlled concentration of oxygen in the discharge environment. Therefore, in an apparatus for performing discharge processing on a long film, a part of the film transport path is surrounded by a chamber, and the oxygen concentration is controlled in the chamber to perform the processing. The oxygen concentration is controlled so that the oxygen concentration in the chamber becomes a specific value such as 0.2%. Such control is performed by adjusting the amount of inert gas such as nitrogen introduced into the chamber. Specifically, in the discharge process, air flows into the chamber along with the film, which increases the oxygen concentration.Therefore, increase the nitrogen introduction amount when the oxygen concentration becomes higher than the set value. The control such as lowering the oxygen concentration in the chamber and lowering the introduction amount of nitrogen to raise the oxygen concentration in the chamber when the oxygen concentration becomes lower than the set value is continuously performed in the discharge treatment.

JP, 2014-196454, A

  During the corona discharge treatment, a by-product formed by the chemical reaction of the active substance generated by the discharge may generate an unwanted foreign substance. The generation of such foreign matter contaminates the film and reduces the quality of the obtained product. Further, since such a foreign substance also contaminates the production line, it is necessary to clean the production line at a higher frequency, which lowers the production efficiency.

  Therefore, an object of the present invention is to provide a method for producing a multilayer film, which can suppress the generation of undesired foreign matters and can efficiently produce a high quality multilayer film.

The inventor has studied to solve the above-mentioned problem. As a result, they have found that the generation of foreign matter can be reduced by setting the oxygen concentration and the water content of the environment of the corona discharge treatment within the specific ranges. The present invention has been completed based on such findings.
That is, the present invention is as follows.

[1] A method for producing a multilayer film, which comprises a belt-shaped base material and a coating layer formed on the surface of the base material,
A discharge treatment step of performing corona discharge treatment on the surface of the base material that continuously runs under an environment of atmospheric pressure or more, oxygen concentration of 0.05 wt% or more and 0.55 wt% or less and water content of 5 mg / m ³ or less. When,
After the discharge treatment step, to form the coating layer by applying a coating liquid on the surface of the substrate subjected to the corona discharge treatment, a coating step,
A method for producing a multilayer film containing.
[2] The manufacturing method according to [1], wherein the discharge treatment step is performed using a corona discharge treatment device equipped with a means capable of forming the environment.
[3] The manufacturing method according to [2], wherein the corona discharge treatment is performed at 5 W · min / m ² or more and 100 W · min / m ² or less.
[4] The means capable of forming the environment includes a chamber surrounding the environment for performing the discharge treatment,
The discharge treatment step includes supplying an inert gas and dry air into the chamber,
[2] or [3], wherein the flow rate X (L / min) of the inert gas and the flow rate Y (L / min) of the dry air satisfy the relationship of 0.002 ≦ Y / X ≦ 0.025. Manufacturing method.
[5] The means capable of forming the environment includes a chamber surrounding the environment in which the discharge treatment is performed,
The discharge treatment step includes supplying an inert gas and dry air into the chamber,
The width W (mm) of the chamber and the flow rate X (L / min) of the inert gas into the chamber satisfy the relation of 0.05 ≦ X / W ≦ 0.30, [2] to [4] ] The manufacturing method of any one of these.
[6] The means capable of forming the environment includes a chamber surrounding the environment for performing the discharge treatment,
The discharge treatment step includes supplying a gas into the chamber,
The width W (mm) of the chamber and the flow rate Z (L / min) of the gas to the chamber satisfy the relationship of 5.05 × 10 ⁻² ≦ Z / W ≦ 3.03 × 10 ⁻¹ . The manufacturing method according to any one of [2] to [5].
[7] The production method according to any one of [1] to [6], wherein the substrate is a resin film containing an alicyclic structure-containing polymer.
[8] The manufacturing method according to any one of [1] to [7], further including a step of discharging the base material after the discharge treatment step and before the coating step.

  According to the method for producing a multilayer film of the present invention, a high quality multilayer film can be efficiently produced.

FIG. 1 is a schematic diagram schematically showing an example of a manufacturing apparatus for carrying out the method for manufacturing a multilayer film of the present invention and an operation of the manufacturing method of the present invention. FIG. 2 is a front view schematically showing a state in which the corona discharge treatment apparatus 100 shown in the example of FIG. 1 is observed from a direction perpendicular to the axis 112 of the roll 111. FIG. 3 is a cross-sectional view schematically showing a cross section of the corona discharge treatment device 100 shown in FIGS. 1 and 2 taken along a plane perpendicular to the axis 112 of the roll 111.

  Hereinafter, the present invention will be described in detail with reference to exemplary embodiments and exemplifications. However, the present invention is not limited to the embodiments and exemplifications shown below, and may be implemented by being arbitrarily modified within the scope of the claims of the present invention and the scope of equivalents thereof.

[1. Outline of manufacturing method]
FIG. 1 is a schematic diagram schematically showing an example of a manufacturing apparatus for carrying out the method for manufacturing a multilayer film of the present invention and an operation of the manufacturing method of the present invention. In FIG. 1, the manufacturing apparatus 10 has a corona discharge treatment apparatus 100, a coating apparatus 300, a scraping apparatus 400, and a stretching apparatus 500 in order from the upstream of the manufacturing line. In the operation of the production method of the present invention using the production apparatus 10, the long base film 30 is unwound from the film roll 60, conveyed in the direction A1, and subjected to corona discharge treatment by the corona discharge treatment apparatus 100, and then applied. The coating liquid is applied by the coating device 300, the excess coating liquid is scraped by the scraping device 400, and stretched by the stretching device 500, thereby obtaining the multilayer film 90, winding, and film roll. 80.

[2. Discharge treatment process]
The manufacturing method of the present invention includes a discharge treatment step of performing corona discharge treatment on a surface of a continuously running base material under a specific environment. Such an electric discharge treatment process is performed using a corona electric discharge treatment apparatus equipped with means capable of forming such an environment. In the example shown in FIG. 1, the process is performed using the corona discharge treatment device 100.

  In the present application, the corona discharge treatment is broadly understood, and includes so-called glow discharge treatment and various discharge treatments called plasma discharge treatment.

[2.1. Discharge treatment device]
A more specific structure of the corona discharge treatment device 100 shown in FIG. 1 is shown in FIGS.
FIG. 2 is a front view schematically showing a state in which the corona discharge treatment apparatus 100 shown in the example of FIG. 1 is observed from a direction perpendicular to the axis 112 of the roll 111. As shown in FIG. 2, the corona discharge treatment device 100 includes a cylindrical roll 111 that can rotate around a shaft 112, a casing 120 provided below the roll 111 in the vicinity of the roll 111, and an inside of the casing 120. And a corona discharge electrode 131 provided in the.

  The housing 120 has a structure surrounding the lower part of the roll 111, and is close to the roll 111 with a slight gap. As a result, the surface of the roll 111 and the housing 120 define the chamber inside.

  As shown in the example of FIG. 2, the housing may be composed of a plurality of partial housings. In the example of FIG. 2, the housing 120 includes a central housing 120B and width-direction end housings 120A and 120C. By having a structure composed of a plurality of partial housings in this way, manufacturing, transportation, installation, width change and maintenance of the housing become easy. In FIG. 2, the partial housings 120A to 120C are shown separated for convenience of illustration, but in actual use, these partial housings are provided in a state of being in contact with each other. The partial housing constitutes one highly airtight chamber. However, the plurality of partial casings, even in a state of being in contact with each other, a slight flow of gas occurs through the gap, and in the portion near the gap in the chamber, the gas component ratio is out of the desired range, As a result, the generation of foreign matter may occur and the film and the chamber may be contaminated. However, according to the manufacturing method of the present invention, even if there is such a slight flow of gas, it is possible to improve the environment inside the chamber and thereby reduce the generation of foreign matter.

  A plurality of electrodes 131 are provided in the housing 120. Preferably, the electrode 131 is electrically connected to a high frequency generator (not shown) in a manner capable of adjusting frequency and power, and is installed in the housing 120 in such a manner that the distance to the roll 111 can be adjusted. By this, the aspect of discharge in the discharge treatment can be adjusted. The electrode 131 has a plate-like shape extending in parallel to the extension direction of the shaft 112 of the roll 111, and thereby contacts with a partial region of the surface of the roll 111 (region indicated by arrow A201 in FIG. 2). The discharge treatment can be uniformly applied to the entire widthwise direction of the base material 30 guided. The roll 111 is connected to the ground as necessary, so that the discharge from the electrode 131 can be efficiently directed to the roll 111.

  FIG. 3 is a cross-sectional view schematically showing a cross section of the corona discharge treatment device 100 shown in FIGS. 1 and 2 taken along a plane perpendicular to the axis 112 of the roll 111. As shown in FIG. 3, inside the housing 120 of the corona discharge treatment apparatus 100, a blowout port (I) 141 that is electrically connected to a gas supply device (not shown) and opens into a chamber defined by the roll 111 and the housing 120. Is provided.

  Inside the housing 120, an oxygen concentration measuring device 151 for measuring the oxygen concentration in the chamber is further provided. Thereby, the oxygen concentration near the electrode 131 during operation can be measured.

  An exhaust port 142 is provided at the bottom of the housing 120. The exhaust port 142 communicates with a conduit 143 extending from the housing 120 and opening to the outside of the housing. From the exhaust port 142, gas can be exhausted from the positive pressure chamber, if necessary.

  The housing 120 includes a front wall 121F that is an upstream wall and a rear wall 121B that is a downstream wall. The front wall 121F has a slit block 122F at its upper end, and the rear wall 121B has a slit block 122B at its upper end. The front wall 121F and the rear wall 121B further include support members 124F and 124B, respectively, and the support members 124F and 124B support the slit blocks 122F and 122B, respectively. Each of the support members 124F and 124B is provided in such a manner that the positions thereof can be changed upward and downward, whereby the width of the gap A31F between the base film 30 and the slit block 122F, and the base film 30 and the slit block. The width of the gap A31B from the 122B can be adjusted. The slit block 122B may have a structure extending over the entire width direction of the housing, or may have a structure in which a plurality of blocks are arranged over the width direction of the housing. For example, it may be composed of a plurality of blocks extending over each of the partial housings shown in the example of FIG. When the slit block is composed of a plurality of blocks, they may be provided in contact with each other. Alternatively, a gap may be provided between the blocks, and the gap portion may be covered with a transparent cover so that the corona discharge portion can be monitored from the outside.

  The electrode 131 is provided in the housing 120 via the support member 134 in the chamber. The support member 134 is provided in such a manner that its position can be changed upward and downward, and thus the size of the gap A33 between the base film 30 and the electrode 131 can be adjusted.

  In the example of FIG. 3, the outlet (II) 123F is provided in the slit block 122F of the front wall 121F. In this example, the blow-out port (II) 123F is provided as a hole provided in the slit block 122F of the front wall 121F (hence, it is provided so as to be embedded inside the slit block 122F of the front wall 121F). , Opening toward the roll 111. The blow-out port (II) 123F is electrically connected to the pipe 126 for supplying the gas from the gas supply device, whereby the gas can be ejected from the blow-out port (II) to form a gas curtain. The blowout port (II) 123F is provided over the entire width direction of the housing 120, and thereby, the reduction of the associated flow can be achieved over the entire introduction port of the base film. The slit block 122F has a structure capable of varying the size of the gap A32 of the blowout port (II) 123F. By adjusting the amount of gas introduced from the pipe 126 and the width of the gap A32, the amount and speed of the gas ejected from the outlet (II) can be adjusted.

[2.2. Operation of discharge processing]
An example of the operation in the discharge treatment process using the corona discharge treatment device 100 shown in FIGS. 2 and 3 will be described. In the discharge treatment step of this example, the substrate film 30 is applied with an appropriate tension to bring it into contact with the roll 111, the roll 111 is rotated, and the substrate film 30 is conveyed in the direction indicated by the arrow A1. As a result, the gap between the roll 111 and the slit block 122F acts as an inlet for introducing the base material film 30 from the outside of the chamber, and the gap between the roll 111 and the slit block 122B becomes the inside of the chamber. It functions as a lead-out port for leading the base material film 30 from the outside. Further, the electrodes 131 are energized to generate corona discharge toward the roll 111, whereby the base film 30 is subjected to continuous corona discharge treatment.

In the discharge treatment step, the oxygen concentration and the water content in the environment in which the corona discharge treatment is carried out are adjusted within a specific range.
The oxygen concentration in the discharge treatment environment is adjusted to 0.05% by weight or more and 0.55% by weight or less. The oxygen concentration is preferably 0.4% by weight or less. The presence of oxygen in the discharge treatment environment imparts polar groups to the surface of the substrate that has been subjected to the corona discharge treatment to achieve the desired modification treatment. By setting the oxygen concentration to the above lower limit or more, it is possible to achieve the application of the polar group in a short time, so that efficient discharge treatment can be performed. However, if the oxygen concentration is too high in an environment without pressure reduction, non-uniform corona discharge may occur. On the other hand, if the oxygen concentration is too high, undesired foreign substances are often generated by byproducts. Therefore, by setting the oxygen concentration to the lower limit or more and the upper limit or less, good corona discharge can be achieved even in an environment without decompression, and the polar group can be efficiently applied to the surface of the base material. It is possible to reduce the generation of foreign matter.

The water content in the discharge treatment environment, that is, the amount of water contained in the gas in the discharge treatment environment is adjusted to 5 mg / m ³ or less. The water content is preferably 2 mg / m ³ or less, ideally 0 mg / m ³ . When the oxygen concentration in the discharge treatment environment is within the above specific range and the water content is within this range, it is possible to suppress the generation of undesired by-products due to discharge.

  The discharge treatment environment having such an oxygen concentration and a water content is, as in the example shown in FIGS. 2 to 3, a treatment apparatus including a chamber surrounding the environment for performing the discharge treatment, and the oxygen concentration in the chamber is used. And by adjusting the water content.

  In a preferred example, the electric discharge treatment step includes supplying an inert gas and dry air into the chamber. Examples of the inert gas include rare gases such as nitrogen and argon, but nitrogen is usually used from the viewpoint of cost.

Dry air is dried air. As the dry air, one whose dew point has a predetermined low value can be used. The dew point of atmospheric pressure of dry air can be preferably -20 ° C or lower, and more preferably -30 ° C or lower. The dry air with a dew point of -20 ° C has a water content of about 1.07 g / m ³ under atmospheric pressure, and by introducing this into the chamber, the water content in the chamber can be easily adjusted to a low value. it can.

Dry air can be prepared by compressing the atmosphere with a compressor to remove condensed water. By such a preparation method, useful dry air can be easily prepared, and a pressure for pumping can be applied to the air. As a specific example of the dry air, air having a dew point of -10 ° C or less under a compression of 0.76 MPa (a dew point of about -34.4 ° C or less under atmospheric pressure, a moisture content of 0.314 g / m under atmospheric pressure). ³ or less) can be used. It is preferable to use dry air to remove particles with a filter before the air is sent to the chamber for good discharge treatment. Specifically, it is preferable that the amount of particles satisfy the requirements of Class 5 of the ISO 14644-1 standard or a stricter class than that.

  When supplying the inert gas and the dry air into the chamber, it is preferable that the flow rate X (L / min) of the inert gas and the dry air flow rate Y (L / min) have a specific ratio. Specifically, it is preferable that X and Y satisfy the relationship of 0.002 ≦ Y / X ≦ 0.025. Y / X is more preferably 0.005 or more, and even more preferably 0.02 or less. When X and Y satisfy such a relationship, the oxygen concentration and the water content in the chamber can be easily adjusted to desired ranges.

  When supplying the gas into the chamber, the flow rate of the gas to be supplied is preferably a specific amount. When supplying the inert gas and the dry air into the chamber, it is preferable that the flow rate of the inert gas supplied into the chamber is a specific amount. Such a flow rate can be defined as a gas flow rate Z (L / min) and an inert gas flow rate X (L / min), that is, Z / W and X / W per chamber width W (mm). The width W of the chamber corresponds to the width A202 of the housing 120 in the example shown in FIGS.

Specifically, it is preferable that Z and W satisfy the relationship of 5.05 × 10 ⁻² ≦ Z / W ≦ 3.03 × 10 ⁻¹ . Z / W is more preferably 0.1 or more, and even more preferably 0.25 or less. Further, it is preferable that X and W satisfy the relationship of 0.05 ≦ X / W ≦ 0.30. X / W is more preferably 0.1 or more, and even more preferably 0.25 or less.

When Z / W, X / W, or both satisfy such a relationship, the oxygen concentration and the water content in the chamber can be easily and stably adjusted to a desired range.
For example, when only an inert gas (Y / X = 0) is supplied to the chamber, the only oxygen supply source is the air flowing in through the gap between the chambers, the main one of which is the base film 30. Along with that, the air flows in through the gap A31F. In this case, the oxygen concentration in the chamber is adjusted by adjusting the supply amount of the inert gas. Since the amount of inert gas supplied at that time becomes relatively small and the inflow of oxygen becomes unstable, if the oxygen concentration becomes higher than the set value during the operation of the discharge treatment, the inert gas will become unstable. It is necessary to continuously perform control such as increasing the amount of introduced oxygen and lowering the amount of inert gas introduced when the oxygen concentration becomes lower than the set value. In addition, when such a gas is supplied, the amount of the gas flowing in from the gap between the partial housings forming the chamber increases, and the generation of foreign matter may increase.
On the other hand, when Z / W or X / W satisfies the relationship described above, a relatively large amount of gas is supplied into the chamber. As a result, the degree to which the oxygen concentration in the chamber is affected by the air flowing in from the gap of the chamber such as the accompanying flow decreases. As a result, even if the Y / X value is set to a certain value without continuous control and only a constant gas supply is maintained without changing it in the discharge processing operation, It is possible to maintain the oxygen concentration in the inside at a desired value. This makes it possible to easily and stably adjust the oxygen concentration in the chamber to a desired range. Also, the water content can be easily and stably adjusted to a desired range by the same principle.

In the manufacturing method of the present invention, the supply of oxygen to the chamber can be performed by introducing dry air into the chamber, so that the amount of air that flows together with the base film through the gap A31F that is the film introduction port is A small amount is preferable for forming a stable chamber environment.
Therefore, it is preferable that the size of the gap A31F is narrower than a certain extent. Specifically, the width of the gap A31F of the inlet is preferably 2 mm or less, more preferably 1.5 mm or less. On the other hand, from the viewpoint of carrying the film smoothly, the lower limit of the width of the gap A31F may be, for example, 0.5 mm or more.
Further, it is preferable that the gas blowing speed from the blowing port (II) is higher than a certain speed, and therefore the width of the gap A32 of the blowing port is preferably narrower than a certain amount. Specifically, the width of the gap A32 of the blowout port is preferably 2 mm or less, more preferably 1.5 mm or less. The lower limit of the width of the gap A32 may be, for example, 0.2 mm or more.

  The atmospheric pressure of the environment in the chamber is controlled to atmospheric pressure or higher, preferably atmospheric pressure + 0.02 MPa or higher. As a result, the amount of outside air flowing into the chamber can be reduced, and an environment with a low oxygen concentration can be easily maintained. On the other hand, the atmospheric pressure of the environment in the chamber is preferably atmospheric pressure + 0.3 MPa or less, more preferably atmospheric pressure + 0.2 MPa or less, because good corona discharge can be formed.

  In the example shown in FIGS. 2 to 3, the gas can be supplied into the chamber by introducing the gas into the chamber from the blowout port (I) 141. The gas supply is performed by deriving a gas flow from a source of the inert gas and the dry air (a device that generates or stores the inert gas and a device that generates or stores the dry air) and joins these flow paths to combine them. Can be mixed and supplied to the outlet (I) 141. When deriving the gas flow from the supply source, the flow rate is measured by a flow meter, and the flow rate is adjusted by a flow rate adjusting device such as a valve to mix the mixture, so that mixing at a desired ratio can be achieved. The flow rates of the inert gas and the dry air may be continuously controlled in parallel with the execution of the electric discharge treatment, but, for example, when the values of Z / W, X / W or both of them are set within a specific range. May set the value of Y / X to a certain value and then maintain it without changing it.

  When the atmospheric pressure of the environment in the chamber becomes higher than the set pressure, the path from the exhaust port 142 to the outside can be opened to exhaust gas from the exhaust pipe 143 to adjust the pressure. Further, in the case where a substance such as a gas which is harmful in performing the discharge treatment is accumulated in the chamber by the discharge treatment, the substance can be removed from the chamber by exhausting it from the exhaust port 142 and the exhaust pipe 143. it can. In that case, in order to maintain the atmospheric pressure in the chamber, the flow rate of the gas blown from the blowout port (I) can be increased as necessary.

  The oxygen concentration in the chamber is preferably adjusted on the basis of the value measured by the oxygen concentration measuring device 151 provided close to the electrode 131 in the housing. By using the value as a reference, it is possible to obtain a value of the oxygen concentration that accurately reflects the oxygen concentration of the discharge space, and to adjust the oxygen concentration more appropriately.

  In the discharge treatment step of this example, oxygen having a concentration lower than that of the atmosphere is contained from the outlet (II) (the outlet (II) 123F in FIG. 4) provided at the upper end of the slit block of the housing 120. It is preferable to blow a gas and blow the gas onto the surface of the base material 30. As the gas, it is preferable to use the same gas as the gas introduced into the chamber from the blowout port (I) 141 from the viewpoint of low supply cost and easy control of the environment in the chamber. An air curtain is formed by blowing a gas containing oxygen at a concentration lower than atmospheric air onto the surface of the base material on the roll from an outlet (II) provided at the upper end of the housing to form the roll 111 and the casing. It is possible to reduce the amount of outside air flowing into the chamber through the gap between the holes 120 and 120. In particular, since the outside air can be introduced together with the introduction of the base material into the introduction port of the base material, at least in the gap which is the introduction port for introducing the base material 30 from the outside to the inside of the chamber. It is preferable to perform such spraying. The blowout port (II) 123F is provided at a position sufficiently separated from the electrode 131, and by blowing from there, the disturbance of corona discharge due to the blowing airflow can be reduced. The distance between the outlet (II) 123F and the electrode 131 is preferably 10 mm or more, more preferably 50 mm or more.

The electric power applied to the electrode 131 during the corona discharge treatment can be appropriately adjusted so that a good corona discharge is formed. From the viewpoint of further reducing the generation of foreign matter, it is preferable to perform corona discharge treatment at a relatively low output. The specific output of the discharge treatment is preferably 5 W · min / m ² or more, more preferably 7 W · min / m ² or more, preferably 100 W · min / m ² or less, more preferably 60 W · min / m 2. It is ² or less. The gap A33 between the base film and the electrode is preferably 0.5 mm or more, and preferably 2 mm or less.

[3. Static elimination process]
In the manufacturing method of the present invention, it is preferable to optionally perform a step of neutralizing the base material after the discharge treatment step and before the coating step. In the example of FIG. 1, the static elimination step can be performed at an arbitrary position in the manufacturing line, which is downstream of the discharge treatment apparatus 100 and upstream of the coating apparatus 300.

  By performing the static elimination step, it is possible to reduce the electrostatic pressure on the surface of the base material, prevent the base material and the coating liquid from repelling each other in the coating step, and fix the coating liquid on the base material surface. Can be promoted.

  The static elimination step can be performed using a known static eliminator. For example, a commercially available static eliminator (for example, SJ-H156A manufactured by Keyence Corporation) can be used to perform static elimination under conditions of static elimination pulse frequency 1 to 68 Hz and downflow 0 to 0.3 m / s.

[4. State of substrate after discharge treatment]
A polar group can be provided on the surface of the base material that has been subjected to the discharge treatment step and, if necessary, the static elimination step. The amount of polar groups on the surface of the treated substrate can be measured by X-ray photoelectron spectroscopy (XPS). The proportion of polar groups on the surface of the treated substrate is 100, which is the total of C—C bond, C—O bond, C═O bond, C (═O) O bond, and O—C (═O) O bond. The ratio of the peak intensity derived from a bond other than the C—C bond is preferably 20 to 100% when the percentage is defined as%.

  The presence of many polar groups on the surface of the treated substrate enhances the affinity for the polar liquid, and the contact angle for the polar liquid becomes smaller than that before the treatment. In addition, since a uniform treatment can be achieved, the standard deviation when the contact angle is measured at many points in the plane can be a small value. For example, even when a stretched film of a resin containing an alicyclic structure-containing polymer having a low affinity for water is used as a base material, the average contact angle θ with water is less than 50 °, and the standard deviation σ of θ is Can achieve a high hydrophilicity, such as less than 4.0.

[5. Coating process]
The manufacturing method of the present invention, after the discharge treatment step, or after the discharge treatment step and the subsequent static elimination step, a coating step of forming a coating layer by applying a coating liquid to the surface of the substrate subjected to the corona discharge treatment. including.

  The coating process can be performed by a known coating device such as a gravure coater, a roll coater, and a die coater. The coating step may also include an operation of scraping the excess coating liquid by a scraping device equipped with a smoothing roll or the like, in addition to the coating operation by the coating device. In the example shown in FIG. 1, the process is performed using the coating device 300 and the scraping device 400.

[6. Other arbitrary steps]
In the manufacturing method of the present invention, any step may be performed in addition to the steps described above. For example, a step of performing a heating operation or the like on the layer of the coating liquid, thereby curing the layer of the coating liquid, and forming the coating layer can be performed. Further, the substrate can be stretched, and the area, thickness, and optical characteristics of the multilayer film obtained thereby can be adjusted to a desired range. Such a stretching step can be performed after the step of curing the layer of the coating liquid, or since the stretching is usually performed by heating the base material at a temperature close to its glass transition temperature, The step of curing the layer of the coating liquid can be performed simultaneously.

[7. Other Embodiments]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and may be modified and implemented.

  For example, in the above-described embodiment, the oxygen concentration measuring device 151 is provided in the chamber to measure the oxygen concentration. However, not only the oxygen concentration but also the concentration of other kinds of substances may be measured in the chamber. It is also possible to provide a measuring device that also measures the above information, and perform the measurement in the discharge treatment step. For example, by the discharge process, substances such as harmful gas in performing the discharge process may accumulate in the chamber, so a measuring device for measuring the amount of the substance is provided, and based on the information obtained from the measuring device, When the amount of the substance is equal to or more than a predetermined amount, the exhaust port 142 is opened to perform the exhaust control in the discharge treatment process.

[8. Description of substrate]
A substrate that can be used in the manufacturing method of the present invention will be described. A film-shaped member is usually used as the substrate. Above all, it is preferable to use a resin film as the substrate. Among the resins forming the base material, a preferable example is a resin containing an alicyclic structure-containing polymer (hereinafter, appropriately referred to as “alicyclic structure-containing polymer resin”). The alicyclic structure-containing polymer resin is excellent in transparency, low hygroscopicity, dimensional stability and light weight, and is suitable for an optical film.

  The alicyclic structure-containing polymer has an alicyclic structure in its main chain and / or side chain. Examples of the alicyclic structure include a saturated cyclic hydrocarbon (cycloalkane) structure and an unsaturated cyclic hydrocarbon (cycloalkene) structure. Among these alicyclic structures, those having a cycloalkane structure are preferable from the viewpoint of light resistance, heat deterioration resistance and the like. The number of carbon atoms constituting the alicyclic structure is not particularly limited, but is usually 4 to 20, preferably 5 to 15, and more preferably 5 to 12 when, for example, heat resistance. Also, the properties of heat deterioration resistance are balanced, which is preferable.

  The proportion of repeating units having an alicyclic structure in the alicyclic structure-containing polymer used in the present invention can be appropriately selected according to the purpose of use, but is usually 40% by weight or more, preferably 60% by weight or more. , And more preferably 70% by weight or more. If the proportion of repeating units having an alicyclic structure in the alicyclic structure-containing polymer is excessively low, the heat resistance of the molded product is deteriorated, which is not preferable. The rest other than the repeating unit having an alicyclic structure in the alicyclic structure-containing polymer is not particularly limited and various ones can be used.

  Specific examples of the polymer having such an alicyclic structure include (1) hydrogenated ring-opening metathesis polymer of norbornene-based monomer disclosed in JP-A-3-109418 and JP-A-4-170425. (2) Addition-type copolymers of norbornene-based monomers and vinyl compounds disclosed in JP-A-61-292201, JP-A-62-252406, JP-A-62-252407, and the like, ( 3) Polymer hydrides of aromatic vinyl compounds disclosed in JP-A 64-001706, JP-A 1-2944753, WO 98/55886, etc., and (4) JP-A 1-294721. , WO 2000/32646, JP 2002-540229 A, JP 2002-370304 A, WO 200. Block copolymer hydride / 018656 Patent aromatic vinyl compounds disclosed in pamphlets and chain conjugated diene compounds, and the like. Among these, from the viewpoint of heat resistance and moldability, a ring-opening metathesis polymer hydride of a norbornene-based monomer, a copolymer hydride of an aromatic vinyl compound and a chain conjugated diene compound, and the like are preferable, and from the viewpoint of mechanical strength. Is more preferably a hydrogenated ring-opening metathesis polymer of a norbornene-based monomer, and more preferably a hydrogenated copolymer of an aromatic vinyl compound and a chain conjugated diene compound from the viewpoint of light resistance.

  The alicyclic structure-containing polymer has a weight average molecular weight (Mw) of usually 10,000 or more, preferably 15,000 or more, more preferably 20,000 or more, and usually 100,000 or less, preferably It is 80,000 or less, more preferably 50,000 or less. Here, the weight average molecular weight (Mw) is the weight average molecular weight in terms of polyisoprene or polystyrene measured by gel permeation chromatography using cyclohexane (toluene when the sample does not dissolve in cyclohexane) as a solvent. is there. When the weight average molecular weight is in such a range, the mechanical strength and molding processability of the multilayer film are highly balanced, which is preferable.

  The resin forming the base material may contain other optional components other than the polymer as long as the effects of the present invention are not significantly impaired. Examples of optional components include colorants such as pigments and dyes; optical brighteners; dispersants; heat stabilizers; light stabilizers; ultraviolet absorbers; antistatic agents; antioxidants; lubricants; Is mentioned. The optional components may be used alone or in combination of two or more at an arbitrary ratio.

  The base material may be a film having a single-layer structure having only one layer or a film having a multi-layer structure having two or more layers. The thickness of the base material is not particularly limited, but is preferably 10 μm or more, more preferably 15 μm or more, preferably 120 μm or less, more preferably 100 μm or less, from the viewpoint of material cost and reduction in thickness and weight. .

  As the base material, a strip-shaped long film is usually used. Here, the long length means that the length is about 5 times or more the width of the film, preferably 10 times or more, and specifically, wound in a roll shape. It has a length that allows it to be rotated and stored or transported. The upper limit of the length with respect to the width is not particularly limited, but may be 100,000 times or less, for example.

  Further, when the multilayer film is used as an optical film, the substrate has a total light transmittance of 1% thickness conversion of preferably 80% or more, and more preferably 90% or more. Here, the total light transmittance can be measured according to JIS K7361-1997. Further, when the multilayer film is used as an optical film, the substrate has a haze in terms of a thickness of 1 mm of preferably 0.3% or less, and particularly preferably 0.2% or less. Here, the haze can be measured according to JIS K7136-1997.

[9. Description of coating liquid]
The coating liquid that can be used in the production method of the present invention will be described.
As the coating liquid, a liquid that can enhance the wettability of the substrate with respect to the liquid by an electric discharge treatment step on the substrate and is suitable for forming a coating layer can be appropriately used. In particular, as the coating liquid, a liquid containing a solvent and a substance that may remain in the coating layer after the coating liquid is dried (hereinafter sometimes simply referred to as “solid content”) can be used.

In the discharge treatment step in the production method of the present invention, a polar group is usually provided on the surface of the base material, so a liquid that can be wetted by the polar group can be used as the solvent.
Specific examples of the solvent include water; organic solvents such as methanol, ethanol, isopropyl alcohol, acetone, tetrahydrofuran, N-methylpyrrolidone, dimethyl sulfoxide, ethylene glycol monomethyl ether, and ethylene glycol monobutyl ether; and the like. Of these, water is usually used. Further, the solvent contained in the coating liquid may be one kind or two or more kinds.

  For example, a liquid composition containing water as a solvent and polyurethane as a solid content dispersed therein can be used as the coating liquid. This composition is called a water-based urethane resin. By using the water-based urethane resin as the coating liquid, an easily adhesive layer can be obtained as the coating layer. The easy-adhesion layer is a layer that functions to reinforce the adhesion between the base material and the arbitrary member by the adhesive to make the adhesion stronger when the base material is bonded to the arbitrary member such as the polarizer. Also called.

  As the polyurethane contained in the water-based urethane resin, for example, (i) a polyurethane obtained by reacting a component having an average of two or more active hydrogens in one molecule with (ii) a polyvalent isocyanate component; The component (i) and the component (ii) are subjected to a urethanization reaction in an organic solvent that is inert to the reaction and has a high affinity for water under conditions of excess isocyanate groups to obtain an isocyanate group-containing prepolymer, and then the prepolymer Polyurethane produced by neutralizing the polymer, extending the chain with a chain extender, and adding water to form a dispersion; and the like. An acid component (acid residue) may be contained in these polyurethanes.

  The component (i) (that is, the component containing an average of two or more active hydrogens in one molecule) is not particularly limited, but one having a hydroxyl group active hydrogen is preferable. Specific examples of such compounds include polyol compounds, polyether polyol compounds, polyester polyol compounds, polyether ester polyol compounds, polycarbonate polyol compounds, and mixtures thereof.

  Examples of the component (ii) (that is, the polyvalent isocyanate component) to be reacted with the component (i) include an aliphatic, alicyclic or aromatic compound containing an average of two or more isocyanate groups in one molecule. Is mentioned.

It is preferable that the polyurethane has an acid structure such as a carboxyl group (—COOH) and a sulfo group (—SO ₃ H) because the dispersibility in water is high. The polyurethane having such an acid structure is preferably used together with a neutralizing agent such as a non-volatile base that neutralizes it, from the viewpoint of enhancing the durability of the product. As the non-volatile base, for example, a base which is substantially non-volatile under the treatment conditions when the coating liquid is applied to the substrate and then dried (for example, when the coating liquid is left at 80 ° C. for 1 hour) can be mentioned. The term "substantially non-volatile" as used herein usually means that the amount of reduction of the non-volatile base is 80% by weight or less.

  As the non-volatile base, an inorganic base may be used, but an organic base is preferable. Among them, an organic base having a boiling point of 100 ° C. or higher is preferable, an amine compound having a boiling point of 100 ° C. or higher is more preferable, and an amine compound having a boiling point of 200 ° C. or higher is particularly preferable. The organic base may be a low molecular weight compound or a polymer.

  As examples of the non-volatile base, examples of the inorganic base include sodium hydroxide and potassium hydroxide. Examples of organic bases include N-methyl-3-aminopropyltrimethoxycarboxylic acid dihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid. Examples thereof include hydrazides such as dihydrazide and terephthalic acid dihydrazide. As the neutralizing agent, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.

  The number average molecular weight of the polyurethane is preferably 1,000 or more, more preferably 20,000 or more, preferably 1,000,000 or less, more preferably 200,000 or less.

  When the coating liquid is an aqueous polyurethane resin, the polyurethane is usually dispersed in water as a solvent, but may be in the form of, for example, an emulsion, a colloidal dispersion system or an aqueous solution.

  The amount of the solvent contained in the coating liquid is such that the solid content concentration of the coating liquid is preferably 0.5% by weight or more, more preferably 1% by weight or more, and preferably 15% by weight or less, more preferably 10% by weight. % Or less. This is because the coating liquid is easy to handle and coating is easy.

  Further, the coating liquid may contain any component other than those described above as long as the effect of the present invention is not significantly impaired. Examples thereof include silica, a cross-linking agent, a heat stabilizer, a weather stabilizer, a leveling agent, an antistatic agent, a slip agent, an antiblocking agent, an antifogging agent, a lubricant, a dye, a pigment, a natural oil, a synthetic oil, and a wax. Etc. In addition, as the optional component, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.

  The viscosity of the coating liquid is preferably 10 mPa · s or less, and particularly preferably 8 mPa · s or less. As a result, the coating liquid can be applied thinly and uniformly.

[10. Description of multilayer film]
The multilayer film produced by the production method of the present invention includes a base material and a coating layer formed on the base material. Here, the dry thickness of the coating layer is preferably 10 nm or more, more preferably 20 nm or more, preferably 120 nm or less, more preferably 100 nm or less.

  In the production method of the present invention, since the discharge treatment step is performed under the specific conditions, the multilayer film obtained thereby can be a film which is less contaminated by foreign matter in the discharge treatment. The foreign matter generated in the electric discharge treatment step usually becomes particles having a particle size of 100 to 600 μm and can adhere to the film. In the multilayer film obtained by the production method of the present invention, the adhesion of particles having such a particle size. It can be a film with less.

The multilayer film is usually used as an optical film. Examples of the optical film used for the multilayer film include a protective film, a retardation film and an optical compensation film.
Moreover, you may use a multilayer film as a stretched film. That is, a stretched film may be used as a substrate to form a coating layer thereon, or a coating layer may be formed on a substrate (either a stretched film or an unstretched film) to form a multilayer film. After being produced, it may be further stretched and used.

  Above all, the multilayer film obtained by the production method of the present invention is suitable as a polarizing plate protective film. When the multilayer film obtained by the production method of the present invention is used as a polarizing plate protective film, such a polarizing plate protective film is, for example, the multilayer film obtained by the production method of the present invention itself as a polarizing plate protective film. The polarizing plate protective film may be a combination of the multilayer film obtained by the production method of the present invention and another film.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following embodiments, and may be arbitrarily modified and carried out within the scope of the claims of the present invention and the scope of equivalents thereof. Further, in the following description, “%” and “parts” representing amounts are by weight unless otherwise specified. Furthermore, in the following description, the operations were carried out in an environment of normal temperature and normal pressure unless otherwise specified regarding temperature and pressure.

[Example 1]
(1-1. Production of coating liquid)
100 parts of an aqueous polyurethane dispersion (“Superflex 210” manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) in an amount of polyurethane, 15 parts of an epoxy compound (“Denacol EX313” manufactured by Nagase Chemtex) as a cross-linking agent, and a non-volatile base. As adipic acid dihydrazide 2 parts, as a lubricant 10 parts of an aqueous dispersion of silica particles (Nissan Chemical Co., Ltd. "Snowtex ZL"; average particle diameter 85 nm) in the amount of silica particles, and acetylene-based surfactant as a wetting agent. 0.5 wt% of the agent (“Surfynol 440” manufactured by Air Products and Chemicals Co., Ltd.) with respect to the total solid content, and water are mixed to prepare a liquid composition having a solid content of 4%. Got as. The viscosity of this coating liquid was 1.2 mPa · s.

(1-2. Production of base film)
Pellets of an alicyclic olefin resin (“ZEONOR” manufactured by Nippon Zeon Co .; glass transition temperature 126 ° C.) containing a norbornene polymer were dried at 100 ° C. for 5 hours. The pellets are supplied to an extruder, melted in the extruder, extruded into a sheet form from a T die onto a casting drum through a polymer pipe and a polymer filter, cooled, and then a long base material having a thickness of 80 μm and a width of 2100 mm. I got a film. Both ends of the obtained base film in the width direction were cut and removed, and the width was set to 1700 mm, and the film was wound into a film roll.

(1-3. Production of multilayer film)
A multilayer film was manufactured using the manufacturing apparatus 10 schematically shown in FIG.

  The substrate film 30 was unwound from the film roll 60 obtained in (1-2), conveyed in the A1 direction, and subjected to corona discharge treatment by the corona discharge treatment device 100 (manufactured by Kasuga Denki KK). Subsequently, the coating liquid obtained in (1-1) is applied by the coating device 300, the surplus coating liquid is scraped by the scraping device 400, and a stretching process is performed by the stretching device 500. The film 90 was obtained and wound to obtain a film roll 90.

As the corona discharge treatment device 100, the device schematically shown in FIGS. 2 and 3 was used. The width A202 of the housing 120 was 2200 mm, and the length of the electrode 131 was 2000 mm. The width of the gap A33 between the electrode 131 and the base film 30 was 1 mm. A gap A31F between the slit block 122F on the front wall of the housing and the base film 30 was set to 1 mm. The discharge amount of the corona discharge treatment device 100 was 10 W · min / m ^2, and the transport speed of the base film 30 introduced into the device 100 was 30 m / min. The amount of nitrogen gas introduced into the chamber in the housing 120 was 300 L / min, and the amount of dry air introduced was 3 L / min (dry air volume / inert gas volume = 0.01). When the oxygen concentration in the chamber was monitored by the oxygen concentration measuring device 151 during the discharge process, the oxygen concentration in the chamber was stably 0.2% without adjusting the introduction amount of gas. It was kept. The atmospheric pressure in the chamber was kept above the atmospheric pressure and below the atmospheric pressure + 0.1 MPa. The water content of the environment inside the chamber was 0.9 mg / m ³ .
The corona-treated film was subjected to static elimination with a static eliminator (SJ-HA manufactured by Keyence Corporation).

  As the coating device 300, a device including a coating roll was used. The coating liquid 40 was applied to the surface of the base film 30 by rotating the coating roll in the same direction as the transport direction of the base film 30 at a peripheral speed of 30 m / min.

  As the scraping device 400, a device equipped with a scraping roll having a diameter of 40 mm was used. The scraping roll was rotated at a rotation speed of 8.5 rpm in the direction opposite to the conveying direction of the base material film 30 and operated so as to obtain a coating layer having a dry thickness of 45 nm.

  In the stretching device 500, both ends of the base film 30 in the width direction were gripped, and the film was continuously stretched in the film width direction at a stretching temperature of 139 ° C. and a stretching ratio of 1.50. During the stretching treatment, the coating liquid layer was heated and cured on the base film 30 to form a coating layer. Thereby, the multilayer film 90 including the base film and the coating layer was obtained.

  Both ends and the width direction of the multilayer film 90 thus obtained were cut and removed, and the remaining part was wound up to form a film roll 80.

The obtained multilayer film 90 was inspected by a regular transmission defect detector (LSC4000V system manufactured by Mec Co., Ltd.), and the number of foreign matters in the multilayer film 90 was counted. As a result, the number of foreign substances that can be confirmed in a size of 100 to 600 μm was 0.001 / m ² .

[Example 2]
A multilayer film was produced and inspected by the same operation as in Example 1 except that the following matters were changed.
In the corona discharge treatment in the production of the multilayer film of (1-3), the introduction amount of dry air was changed from 3 L / min to 6 L / min. When the oxygen concentration in the chamber was monitored by the oxygen concentration measuring device 151 during the discharge process, the oxygen concentration in the chamber was stably 0.4% even if the introduction amount of gas was not adjusted. It was kept. The water content of the environment in the chamber was 1.7 mg / m ³ .

In the multilayer film 90, the number of foreign matters that can be confirmed in a size of 100 to 600 μm was 0.004 pieces / m ² .

[Comparative Example 1]
A multilayer film was produced and inspected by the same operation as in Example 1 except that the following matters were changed.
-Dry air was not introduced in the corona discharge treatment in the production of the multilayer film of (1-3). When the oxygen concentration in the chamber was monitored by the oxygen concentration measuring device 151 during the discharge treatment, the oxygen concentration in the chamber was not stable, so that the oxygen concentration in the chamber was 0.2 to 0.3%. Thus, the introduction amount of nitrogen gas was adjusted within the range of 110 to 150 L / min. The water content of the environment in the chamber was 35 mg / m ³ .

In the multilayer film 90, the number of foreign matters that can be confirmed in a size of 100 to 600 μm was 0.1 / m ² .

10: Manufacturing device 30: Base film 60: Film roll 80: Film roll 90: Multilayer film 100: Corona discharge treatment device 111: Roll 112: Shaft 120: Enclosure 120A: Partial housing at end 120B: Central part Case 120C: Partial case at the end 121B: Case rear wall 121F: Case front wall 122B: Slit block 122F: Slit block 123F: Air outlet (II)
124B: Support member 124F: Support member 126: Tube 131: Corona discharge electrode 134: Support member 141: Blowout port (I)
142: Exhaust port 143: Conduit 151: Oxygen concentration measuring device 300: Coating device 400: Scraping device 500: Stretching device A1: Roll conveying direction A201: Area where substrate is guided A202: Width of housing A31B: Gap A31F : Gap A32: Gap A33: Gap

Claims (8)

A method for producing a multilayer film comprising a belt-shaped base material and a coating layer formed on the surface of the base material,
A discharge treatment step of performing corona discharge treatment on the surface of the base material that continuously runs under an environment of atmospheric pressure or more, oxygen concentration of 0.05 wt% or more and 0.55 wt% or less and water content of 5 mg / m ³ or less. When,
After the discharge treatment step, to form the coating layer by applying a coating liquid on the surface of the substrate subjected to the corona discharge treatment, a coating step,
A method for producing a multilayer film containing.   The manufacturing method according to claim 1, wherein the discharge treatment step is performed using a corona discharge treatment device provided with a means capable of forming the environment. The manufacturing method according to claim 2, wherein the corona discharge treatment is performed at 5 W · min / m ² or more and 100 W · min / m ² or less. The means capable of forming the environment includes a chamber surrounding the environment in which the discharge treatment is performed,
The discharge treatment step includes supplying an inert gas and dry air into the chamber,
The production according to claim 2 or 3, wherein the flow rate X (L / min) of the inert gas and the flow rate Y (L / min) of the dry air satisfy the relationship of 0.002 ≦ Y / X ≦ 0.025. Method. The means capable of forming the environment includes a chamber surrounding the environment in which the discharge treatment is performed,
The discharge treatment step includes supplying an inert gas and dry air into the chamber,
The width W (mm) of the chamber and the flow rate X (L / min) of the inert gas to the chamber satisfy the relationship of 0.05 ≦ X / W ≦ 0.30. The manufacturing method according to any one of items. The means capable of forming the environment includes a chamber surrounding the environment in which the discharge treatment is performed,
The discharge treatment step includes supplying a gas into the chamber,
The width W (mm) of the chamber and the flow rate Z (L / min) of the gas to the chamber satisfy the relationship of 5.05 × 10 ⁻² ≦ Z / W ≦ 3.03 × 10 ⁻¹ . The manufacturing method according to any one of claims 2 to 5.   The manufacturing method according to any one of claims 1 to 6, wherein the base material is a film of a resin containing an alicyclic structure-containing polymer.   The manufacturing method according to claim 1, further comprising a step of discharging the base material after the discharging step and before the coating step.

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