JPH10314660A - Coating method for continuously traveling web and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the fluctuation in the thicknesses of coating films at the time of subjecting both surfaces of a continuously traveling web to coating by coating means, then drying both surfaces of this web by drying means. SOLUTION: Air vibration radiating means 6 and 7 radiates air vibration to the web 1 between the coating means 2 and 3 and the drying means 4. A reference signal measuring means 11 measures the web vibration in the direction perpendicular to the web surface between the position where the air vibration is radiated to the web 1 and the drying means 4. A signal computing means 10 computes the signals having the amplitude and phase to absorb the vibration of the web 1 in accordance with the signals of the web vibration measured by this reference signal measuring means 11 and controls the air vibration radiating means 6 and 7 in such a manner that the air vibration to negate the vibration of the web 1 is radiated to the web 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for coating a continuously running web. More specifically, the present invention relates to a coating method and an apparatus for forming a coating liquid film (coat layer) having a uniform and good appearance, which can be applied to an off-line coating on a running web or an in-line coating in a film production process. Furthermore, the present invention relates to a technique for eliminating a spot called a horizontal step spot that enters a direction perpendicular to a web traveling direction caused by web vibration.

[0002]

2. Description of the Related Art When applying a coating material to both sides of a continuously running plastic film, paper, or other web, the web must be flat without vibrations, wrinkles, etc. in order to apply the coating without unevenness on the coating surface. Is the first condition. When drying is carried out by a hot air non-contact dryer which is usually used, the web is inevitably vibrated by the hot air, and in a tenter for gripping a film edge, vibration is generated when the film edge is gripped by a clip. Guide rolls before and after the application means,
A method called a cross guider, which grips a web edge to apply tension in the lateral direction and remove wrinkles, has been used.

[0003] However, in the case of coating on both sides, a guide roll cannot be provided after the coating means, and the cross guider alone cannot prevent the vibration at the center of the web. , Which greatly reduced the quality of the product.

[0004]

In order to solve this problem, Japanese Patent Application Laid-Open No. Sho 62-247861 discloses a method of absorbing vibration of a web by a method in which a gas blowing cylinder and a solid blade opposed to each other across a web are brought into contact with the web. It has been proposed to ensure flatness. However, even if the vibration is absorbed, simply blowing out the gas cannot completely absorb the vibration of the web, and the application amount changes when the blade is applied to the application surface. For this reason, in the prior art, there remains a problem that a variation in the thickness of a coating film, which is called horizontal unevenness in double-sided coating, cannot be prevented.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to prevent the thickness of a coating film from fluctuating when a continuous running web is coated on both sides.

[0006]

The continuous running web coating method of the present invention comprises a coating step of coating both sides of a continuously running web, and a drying step of drying both sides of the web after the coating step. In a continuous running web coating method,
Between the application step and the drying step, air vibration is emitted to the web so as to cancel the vibration of the web.

Here, in order to further enhance the effect of preventing the thickness variation of the coating film, the vibration of the web in the direction perpendicular to the web surface between the coating step and the drying step is determined by the position at which the air vibration is radiated to the web. More preferably, air vibrations having an amplitude and a phase that absorb the vibrations of the web and are measured during the drying step are emitted to the web. Further, it is more preferable that the phase and amplitude of the air vibration radiated to the web be controlled so that the web vibration between the application step and the position where the air vibration is radiated to the web is minimized.

[0008] The continuous running web coating apparatus of the present invention is a continuous running web coating apparatus in which coating is performed on both sides of a continuously running web by a coating unit, and thereafter, both sides of the web are dried by a drying unit. The air vibration radiating means that radiates air vibration to the web is provided between the drying means and the air vibration, and the web vibration in the direction perpendicular to the web surface between the position where the air vibration is radiated to the web and the drying means is measured. Calculating a signal having an amplitude and a phase for absorbing the web vibration based on the web vibration signal measured by the reference signal measuring means, and radiating air vibration to cancel the web vibration to the web Signal calculation means for controlling the air vibration radiating means.

Here, in order to further enhance the effect of preventing the thickness variation of the coating film, control for measuring the web vibration in the direction perpendicular to the web surface between the coating means and the position where the air vibration is radiated to the web is performed. It is more preferable that a signal measuring unit is provided, and the signal calculating unit also takes in the signal measured by the control signal measuring unit, and controls the air vibration radiating unit to radiate the air vibration to cancel the web vibration to the web.

[0010] The continuous running web of the present invention is preferably a plastic film. Examples of the plastic film include a polyolefin film (eg, polyethylene (PE) film, polypropylene (PP) film, etc.), a polyester film (eg, polyethylene terephthalate (PET) film, polyethylene-2,6-naphthalate film, etc.), a polyamide film ( For example, a nylon 6 film, a nylon 66 film, etc.), a polyetheretherketone film, a polycarbonate film and the like can be exemplified. Among them, polyester film, especially polyethylene terephthalate film, polyethylene-2,6-
Naphthalate films are preferred. The thickness of such a web is usually 5 to 800 μm, preferably 10 to 200 μm.
m. The running speed of the web is 5 to 1000 m / m.
in is preferred, and 10 to 350 m / min is optimal.

In the present invention, the coating liquid has functional properties such as adhesion (including easy adhesion and heat sealability), easy slip (running), antistatic property, conductivity, and abrasion resistance on the web surface. Abrasion resistance, weather resistance, mold release properties, chemical resistance (including water resistance, solvent resistance), easy printability, drip resistance, stain resistance, writability,
Any coating solution may be used as long as it is a surface processing coating liquid that imparts light-shielding properties, waterproof properties, gas barrier properties, and the like. As these coating liquids, those conventionally known or used can be used. The viscosity of the coating liquid is 1 to 200
Centipoise (cP), more preferably 1.1 to 20 cP.

The double-sided coating in the present invention is directed to a method of coating one side and coating the other side without drying, and then drying both sides. However, it is also applicable to the case where one side coating or one side coating and drying is performed, and then the other side coating is performed.In order to prevent the web surface from being scratched or the like, it is not necessary to apply a guide roll or the like to the web surface. In some cases it is useful. Further, as a coating means in the present invention, there is a great advantage particularly in a method easily affected by web vibration such as a die coater or a roll coater.

The drying means in the present invention may be, for example, a floating dryer using hot air, or a drying apparatus using both an IR heater and hot air. Further, a horizontal stretching device such as a clip tenter in a film forming line may be used.

In the present invention, as the means for generating air vibration on the web, any apparatus may be used as long as it can vibrate air at a frequency of 20 to 200 Hz and has a capacity sufficient to suppress the vibration of the web. The required volume is the thickness of the web,
It varies with the magnitude of web vibration caused by width, dryer air volume, wind speed, etc.

In the present invention, the reference signal measuring means or the control signal measuring means for measuring the web vibration in the direction perpendicular to the web surface is preferably of a non-contact type because of the influence on the coated surface, and the response frequency is higher than the web vibration frequency. Needs to be A commercially available measuring instrument can be applied, and for example, a displacement meter using reflection of laser light can be measured.

The signal calculating means takes in the position, displacement speed or displacement acceleration signal of the web measured by the reference signal measuring means or the control signal measuring means and performs a frequency analysis to generate a signal for eliminating the vibration of the web. A general personal computer with an input / output expansion board incorporated therein can be used.

The signal calculating means receives a signal from the reference signal measuring means as a reference for the amplitude and cycle of the web vibration, generates a signal for canceling the web vibration before the system is started, and outputs the signal. The state of application (web tension, web temperature, etc.) changes from moment to moment, and the vibration state of the web also changes. Therefore, in order to follow this, it is also possible to intermittently take in the signal of the reference signal measuring means and change the output.

In addition, the present system includes a method of transmitting vibration from surrounding speakers to air, transmitting force from air to the web, and the like.
Complex transfer functions are inherent. For this reason, a signal obtained only based on the signal from the reference signal measuring means may not be able to effectively absorb web vibration. For this reason, the signal of the control signal measuring means for measuring the web vibration in the direction perpendicular to the web surface between the coating means and the position where the air vibration is radiated to the web is sent to the signal calculating means for controlling the air vibration emitting means. It is preferable to apply feedback for appropriately adjusting the amplitude and phase of the output signal to the capturing and air vibration radiating means. That is, the output signal is slightly changed, and if the result is good, the amplitude and phase of the output signal are changed further in that direction, or worse, in the opposite direction. When the vibration state of the web changes and changes up to the vibration period, it may not be possible to follow only with the signal of the control signal measuring means, and it is preferable that the signal from the reference signal measuring means is also fed back to the signal calculating means. .

[0019]

FIG. 1 shows an example of a coating apparatus according to the present invention.
In the figure, 1 is a web, 2 is an upper surface application unit, 3 is a lower surface application unit, 4 is a drying unit, 5 is a hot air nozzle, 6 and 7 are air vibration generation units, 8 and 9 are signal amplification units, and 10 is a signal operation unit. Means, 11 is a reference signal measuring means, and 12 is a control signal measuring means.

The coating liquid was continuously applied to the running web 1 using the equipment shown in FIG. The coating liquid used was an aqueous emulsion coating liquid having a viscosity of 10 cP and a surface tension of 40 dyne / cm, and the web used was a PET film having a thickness of 50 μm and a width of 500 mm. The coating speed was adjusted to 80 m / min, and the tension was adjusted to 10 kg over the entire width of the web. The coating amount was 5 g / m ² in a wet state on both sides. For the air vibration generators 6 and 7, audio cone type speakers having an input capacity of 200 W and a diameter of 40 cm were used. The distance between the web and the upper and lower sides was set to 10 mm.

The signal amplifying means 8 and 9 correspond to the signal arithmetic means 1
It is a device that amplifies a weak electric signal from 0 and generates sufficient electric power to drive the air vibration generating means 6 and 7, as long as the device has a capacity enough to suppress the vibration of the web. A general audio amplifier can be used. Here, the signal amplification means 8 and 9 have an output of 100 W for music reproduction.
Were used. As the reference signal measuring means 11 and the control signal measuring means 12, a laser focus displacement meter manufactured by Keyence Corporation was used.

[Comparative Example 1] First, when the vibration of the web was measured in a state where the signal calculation means 10 was not operated, the vibration was observed over a frequency of 30 to 100 Hz as a result of the frequency analysis. In particular, the amplitude of the vibration at 40 to 50 Hz was large, and the maximum amplitude was 2 mm. When the coated surface after the coating liquid was dried was observed with transmitted light, horizontal step spots at a frequency of 40 to 50 Hz were observed. This was a level of unevenness that exceeded the product limit and could not be shipped.

[Example 1] In this state, signals having opposite phases for canceling the web vibration were generated based on the signal from the reference signal measuring means 11 and output from the air signal generators 6 and 7. The upper and lower air vibration generators output air vibrations of completely opposite phases. As a result, the maximum amplitude of the web vibration between the coating means 3 and the air vibration generator was reduced to 1.2 mm, and the horizontal unevenness after the coating liquid was dried was reduced to a level at which it could be shipped.

[Embodiment 2] Here, the control signal measuring means 12
When the amplitude and phase of the air vibration emitted to the web were automatically adjusted so that the signal from the web became minimum, the maximum amplitude of the web vibration was reduced to 0.5 mm after 30 seconds, and after the coating liquid was dried. The horizontal step became invisible to the naked eye.

[0025]

According to the present invention, the vibration of the web is positively applied to the vibrating web to absorb the vibration of the web, thereby preventing the variation in the thickness of the coating film called horizontal unevenness in double-sided coating. The quality at the time of application can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a continuous running web coating apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Web 2 Upper surface application means 3 Lower surface application means 4 Drying means 5 Hot air nozzle 6, 7, Air vibration generator 8, 9 Signal amplifier 10 Signal calculation means 11 Reference signal measurement means 12 Control signal measurement means

Claims (5)

[Claims] 1. A continuous running web coating method comprising: a coating step of coating both sides of a continuously running web; and a drying step of drying both sides of the web after the coating step.
A coating method for a continuous running web, wherein air is radiated to the web so as to cancel the vibration of the web between the coating step and the drying step. 2. A method for measuring the vibration of a web in a direction perpendicular to the web surface between a coating step and a drying step between a position where air vibration is emitted to the web and a drying step, and an amplitude at which the vibration of the web is absorbed. 2. A method for coating a continuous running web according to claim 1, wherein air vibration having a phase with the web is radiated to the web. 3. The method according to claim 2, wherein the phase and the amplitude of the air vibration radiating to the web are controlled so that the web vibration between the application step and the position where the air vibration radiates to the web is minimized. The coating method for a continuous running web as described above. 4. A continuous running web coating apparatus in which coating is performed on both sides of a continuously running web by a coating unit, and thereafter drying of both sides of the web is performed by a drying unit. A reference signal measuring means for measuring a web vibration in a direction perpendicular to the web surface between a position where the air vibration is radiated to the web and a drying means, comprising air vibration radiating means for radiating air vibration, and reference signal measuring By calculating a signal having an amplitude and a phase for absorbing the web vibration based on the web vibration signal measured by the means,
And a signal calculating means for controlling the air vibration radiating means so as to radiate the air vibration to the web to cancel the vibration of the web. 5. A control signal measuring means for measuring a web vibration in a direction perpendicular to a web surface between the coating means and a position where air vibration is radiated to the web, wherein the signal calculating means measures the control vibration by the control signal measuring means. 5. The continuous running web coating apparatus according to claim 4, wherein the air vibration radiating means is controlled so as to irradiate the web with air vibration which cancels the vibration of the web by also taking in the generated signal.