JP2013160387A - Drying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating film drying device capable of suppressing drying irregularities while keeping an efficient drying capability in a film forming step requiring precise film thickness control.SOLUTION: The drying device dries the coating film continuously applied with a coating liquid to a traveling belt-like flexible base material by a coating head, while allowing the base material to travel in a direction opposite to the gravitational direction. The drying device includes a slit plate which is provided close to the coating film surface side of the base material, having a size equal to or larger than the coating film surface in the width direction and provided with a plurality of slits, an air distributing/exhausting means which has an air distributing means and an air exhausting means on a side opposite to the base material relative to the slit plate, and a means for heating the base material, which is provided on a side opposite to the slit plate relative to the base material. The plurality of slits of the slit plate are formed inclined to the traveling direction of the base material, an opening on a side close to the base material of the slits is on the upper side in the gravitational direction, and an opening on a side away from the base material of the slits is on the lower side in the gravitational direction.

Description

  The present invention relates to an apparatus for drying a coating film surface formed by applying various liquid compositions to a traveling flexible film.

  As a drying device that dries the coating film surface formed by applying various liquid compositions to a long flexible film that runs continuously, the non-coating surface side is supported by a roller and the coating surface side is air・ Drying equipment that blows air from the nozzle, and air is blown from the air nozzle on both the coated and non-coated surfaces to dry the substrate in a floating state, that is, without contacting the substrate with a roller, etc. Non-contact type air floating dryers are well known.

  Usually, in an apparatus for blowing and drying these winds, the solvent contained in the coating surface is evaporated and dried by blowing the conditioned air on the coating surface. Although the drying device of this type that blows air is excellent in drying efficiency, even when air is applied to the application surface through a porous plate, a rectifying plate, etc., the air is directly applied to the application surface Similarly, the coating surface is disturbed by this wind, resulting in uneven coating layer thickness and unevenness, and the solvent evaporation rate on the coating surface is uneven due to convection, resulting in so-called crushed skin. However, there is a problem that a uniform coating layer cannot be obtained.

  In particular, when the coating solution contains an organic solvent, the occurrence of such unevenness is remarkable. The reason for this is that the organic film is sufficiently contained in the coating film at the initial stage of drying, and if the evaporation distribution of the organic solvent occurs at this stage, the temperature distribution and surface tension distribution on the coating film surface will result. This is because a flow such as so-called Marangoni convection occurs in the coating film surface. The occurrence of such unevenness becomes a serious coating defect.

  As a method for preventing such unevenness, a method of blocking the turbulent wind by covering the entire coating film surface is used, but the evaporated solvent gas and the drying air are the causes of the turbulence of the air current on the coating film surface. The coating unevenness often did not disappear due to the turbulence of the air flow that was generated when the mixture was mixed.

  Therefore, for example, a method as disclosed in Patent Document 1 is disclosed in order not to disturb the airflow while removing the solvent component that evaporates. In Patent Document 1, hot air is sent in parallel to the coating film formed on the base material in the drying apparatus and in the transport direction of the coating film, and the speed of the hot air that is the laminar flow is transported of the base material. Control is performed so that the relative speed is 0.1 m / second to 5 m / second with respect to the speed. However, with this structure, in order to keep the air flow on the substrate surface to be conveyed in a laminar flow, it is necessary to set the blowing air volume and angle with high accuracy, which is difficult at a practical conveyance speed.

JP 2002-340479 A

  In view of the above problems, an object of the present invention is to provide a coating film drying apparatus capable of suppressing the occurrence of drying unevenness in a film forming process that requires precise film thickness control.

As means for solving the above-mentioned problems, the invention according to claim 1 of the present invention is directed to a coating film continuously applied to a belt-like flexible substrate by a coating head, and the substrate is opposite to the direction of gravity. A drying device that dries while traveling in a direction, at least,
A slit plate provided close to the coating film surface side of the substrate, having a width equal to or greater than the width of the coating film surface, and provided with a plurality of slits;
Blower exhaust means having air supply and exhaust on the opposite side of the substrate with respect to the slit plate,
Provided on the opposite side to the slit plate with respect to the base material, and comprises a substrate heating means for heating the base material,
The plurality of slits of the slit plate are provided to be inclined with respect to the traveling direction of the substrate, and the opening of the slit facing the substrate is on the upper side opposite to the direction of gravity, and the base of the slit is The drying device is characterized in that the opening opposite to the material is on the lower side in the direction of gravity.

  The invention according to claim 2 is the drying apparatus according to claim 1, wherein the slit plate is provided immediately after the coating head in the running direction of the substrate.

  The invention according to claim 3 is the drying apparatus according to claim 1 or 2, characterized in that a space between the slit plate and the coating head is covered with a cover.

  The invention according to claim 4 is the drying apparatus according to any one of claims 1 to 3, wherein an interval between the slit plate and the base material is 1 mm to 50 mm.

  According to the first aspect of the present invention, the solvent component evaporated from the coating film surface gently falls between the substrate and the slit plate due to its own weight, and is located on the upper side opposite to the direction of gravity. From the opening on the side close to the material, the flow can be naturally formed toward the opening on the side far from the base material located on the lower side, and the flow of the evaporated solvent component is rectified by the blower exhaust means, Occurrence of drying unevenness of the coating film can be suppressed. Further, by heating the substrate, it is possible to increase the drying efficiency while suppressing unevenness.

According to the second aspect of the present invention, the effect can be exhibited more particularly by installing the slit plate in the initial drying portion immediately after coating, which greatly affects the occurrence of unevenness.

  According to claim 3 of the present invention, by covering the space between the slit plate and the coating head with the cover, all the gas containing the vaporized solvent passes through the slit plate without leaking from between the slit plate and the coating head. Thus, it can be transferred into the box, and the occurrence of uneven drying of the coating film can be suppressed satisfactorily.

  According to claim 4 of the present invention, by setting the distance between the slit plate and the substrate to 1 mm to 50 mm, it is possible to satisfactorily suppress the occurrence of uneven drying of the coating film.

It is the schematic which shows the cross section of an example of the drying apparatus of this invention, Fig.1 (a) is a schematic sectional drawing which shows an example of the drying apparatus of this invention, FIG.1 (b) shows a slit board, FIG.1 (a). It is a schematic sectional drawing which shows the side surface seen from the left side of this paper surface.

  The drying apparatus of the present invention will be described in detail below in accordance with embodiments with reference to the drawings. Fig.1 (a) is a schematic sectional drawing which shows an example of the drying apparatus of this invention.

  In the drying apparatus of the present invention shown in FIG. 1 (a), the liquid composition is applied to one surface of the substrate 8 unwound from the unwinding roll 5 by the coating head 7, and then the vicinity of the coated surface. The slit plate 2 is installed in the vicinity.

The slit plate 2 opens in the width direction of the base material 8 at least more than the coating width, and allows air to enter and exit the entire width direction. FIG. 1B is a diagram showing a side surface of the slit plate 2 viewed from the left side of the paper surface of FIG. The slits 2 _a , 2 _{b to} 2 _n are continuously provided in the flow direction of the base material 8. For example, in the slit 2 _a , the opening 2 _a-1 is closer to the base material 8, and the opening 2 _a-2. Is provided on the far side, the slits 2 _a , 2 _b to 2 _n are provided to be inclined with respect to the traveling direction of the base material 8, and the opening of the slit near the base material 8 is in the direction of gravity. Is the upper side which is the opposite direction, and the opening on the side far from the base material 8 of the slit is provided on the lower side which is the direction of gravity. That is, when the slits 2 _a, the upper and the direction of the side of the opening 2 _a-1 gravity closer to the base 8 of the slits are opposite, on the far side to the substrate 8 of the slit opening 2 _{a- 2} is provided on the lower side which is the direction of gravity.

Here, the inclination angle of the slits 2 _a , 2 _b to 2 _n with respect to the base material 8 is arbitrarily set depending on the type of application target and the type of solvent contained.

  Further, by covering the space between the slit plate 2 and the coating head 7 with the cover 10, it is possible to prevent the gas containing the solvent from leaking out between the slit plate 2 and the coating head 7.

  On the opposite side of the base plate 8 with respect to the slit plate 2, a ventilation exhaust means 3 having exhaust and intake air is installed. As a result, the gas containing a large amount of the solvent flowing in from the slits of the slit plate 2 is removed, the solvent concentration does not increase without limit, and continuous solvent inflow becomes possible. The direction of the air flow may be from the top to the bottom of the flow direction of the base material 8, from the bottom to the top, or the width direction of the base material 8. Further, the rectifying plate 1 may be installed in order to prevent the turbulence of the airflow inside the exhaust box 13.

  Further, the substrate heating means 4 can be installed on the side opposite to the slit plate 2 with respect to the substrate 8. As the substrate heating method, a non-contact heating method using a near infrared heater, a far infrared heater, a heat ray heater, a microwave heater, etc., or a roll substrate heated by hot water, steam, oil, heat ray, etc. is brought into contact. A contact heating method for heating the substrate may also be used. The substrate heating means 4 can promote the evaporation of the organic solvent in the coating liquid, and it is possible to increase the drying efficiency while suppressing drying unevenness.

  The drying apparatus according to the present invention can remove the solvent by evaporation without adversely affecting the coating film surface and suppress the occurrence of slight drying unevenness, but the effect is most apparent in the initial stage of drying. Therefore, the entire length of the drying apparatus is not based on the drying apparatus of the present invention, and the effect can be obtained even if the drying apparatus of the present invention is introduced only in the initial drying stage immediately after application to the substrate 8. In that case, you may introduce | transduce a well-known drying apparatus as a 2nd drying apparatus after the drying apparatus of this invention.

  As the second drying device, a method of applying a jet of increased temperature to the coating film formed on the substrate from a slit nozzle or punching metal may be introduced, or a quick return nozzle or substrate A system in which hot air is ejected from a nozzle that uses a parallel flow in the transport direction may be used. Moreover, you may provide a heating means not only from one side but from both sides. Use of any commonly used drying apparatus does not hinder the effects of the present invention.

  Examples of the coating head 7 used in the present invention include, but are not limited to, a die coater, a bar coater, a curtain coater, an extrusion coater, a roll coater, a dip coater, and a gravure coater. is not.

  The base material 8 used in the present invention is polyethylene terephthalate, polyethylene-2,6 naphthalate, cellulose diacetate, cellulose triacetate (triacetyl cellulose), cellulose acetate propionate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyimide. And plastic films such as polyamide, but are not limited thereto. In addition, paper or paper coated or laminated with α-polyolefins having 2 to 10 carbon atoms such as polyethylene, polypropylene, ethylene butene copolymer, and metal foils such as aluminum, copper, and tin are also included. However, it is not limited to these.

  The coating liquid used in the present invention contains a solvent, and any known coating liquid can be used as long as it forms a coating film on a substrate.

  Examples of the solvent used in the present invention include alcohols such as methanol, ethanol, isopropanol, butanol and 2-methoxyethanol, ketones such as acetone, methyl ethyl ketone and methyl isobutyl, and esters such as methyl acetate, ethyl acetate and butyl acetate. , Ethers such as diisopropyl ether, glycols such as ethylene glycol, propylene glycol and hexylene glycol, glycol ethers such as ethyl cellosolve, butyl cellosolve, ethyl carbitol and butyl carbitol, and aliphatic carbonization such as hexane, heptane and octane Examples include hydrogens, halogenated hydrocarbons, aromatic hydrocarbons such as benzene, toluene, and xylene, N-methylpyrrolidone, dimethylformamide, and the like, or one or a mixture of two or more There may be, but is not limited to these.

<Example>
With a drying apparatus as shown in FIG. 1 (a), the coating film immediately after the coating liquid was applied to the substrate was dried, and it was confirmed whether or not uneven drying occurred.

  The slit plate 2 is arranged immediately after the application, and a box 13 having an equivalent size is installed on the opposite side of the base plate 8 with respect to the slit plate 2, and air is supplied from the air inlet 11 therein. Exhaust was performed from the exhaust port 12. At this time, the rectifying plate 1 was provided with a honeycomb rectifying plate. Further, a far infrared heater was installed on the side opposite to the slit plate 2 with respect to the substrate 8. Here, the total length of the slit plate 2 in the conveyance direction of the substrate 8 was 2 m, and the distance between the substrate 8 and the slit plate 2 was 10 mm. The length in the longitudinal direction of each slit of the slit plate 2 was 50 mm, the thickness of the slit plate 2 was 30 mm, and the width of the slit was 5 mm. In addition, the slit angle was 45 ° with respect to the vertical direction of the base material 8, and the slit was arranged so that the base material 8 side was on top. The air supply and exhaust air blowers were adjusted so that the air speed inside the box 13 of the blower / exhaust means 3 was 1 m / min, and the differential pressure from the atmospheric pressure inside the box 13 was 0 Pa. Moreover, it adjusted so that the surface temperature of a far-infrared heater might be set to 100 degreeC, and it has arrange | positioned so that the distance from the base material 8 may be set to 100 mm.

  As the coating solution, a coating solution of 50% toluene solvent and 50% acrylic resin was used, and a polyethylene terephthalate film having a thickness of 100 μm was used for the substrate 8. As coating conditions, coating was performed by die coating at a coating speed of 20 m / min.

  When coating was performed under the above-mentioned conditions, it was not possible to confirm unevenness that would cause a problem.

<Comparative example>
In the state where the drying apparatus of the present invention is not installed at all, when coating was performed under the same conditions as in the above examples, it was possible to confirm unevenness of the coating film as a smear, or a visible scratch on the product, As a product, a good product could not be obtained.

  Table 1 shows the results of the appearance evaluation of the coated film after drying when the distance between the slit plate and the coated substrate was changed using the drying apparatus of the present invention under the above conditions. A sample was produced under the same conditions as in the example except that the distance between the slit plate and the coated substrate was changed between 0.5 mm and 60 mm. In that case, when the coating film after drying was 0.5 mm, the slit plate and the substrate were in contact with each other, and scratches were observed on the surface of the coating film. In the case of 55 mm, it was possible to confirm slight drying unevenness that was dull in the coating film, and in the case of 60 mm, it was possible to clearly confirm the dullness. From this, it was determined that the distance between the slit plate and the coated substrate is desirably set between the lower limit interval of 1 mm and the upper limit interval of 50 mm.

  The drying apparatus of the present invention requires high-precision quality, such as optical films, electronic substrates, food packaging materials, medical packaging materials, etc., in the mass production field using a wet coating method that requires a drying process, This ensures stable production quality and contributes to lower costs and higher accuracy.

DESCRIPTION OF SYMBOLS 1 ... Rectifying plate 2 ... Slit plate 3 ... Air exhausting means 4 ... Base-material heating means 5 ... Unwinding roll 6 ... Coating roll 7 ... Coating head 8 ... -Base material 10 ... cover 11 ... air supply part 12 ... exhaust part 13 ... box 14 ... solvent flow 2a, 2b-2n in the gaseous state ... slit 2a-1, 2a-2 ... Slit opening

Claims (4)

A drying device that dries a coating film continuously applied to a belt-like flexible substrate by a coating head while running the substrate in a direction opposite to the direction of gravity, at least,
A slit plate provided close to the coating film surface side of the substrate, having a width equal to or greater than the width of the coating film surface, and provided with a plurality of slits;
Blower exhaust means having air supply and exhaust on the opposite side of the substrate with respect to the slit plate,
Provided on the opposite side to the slit plate with respect to the base material, and comprises a substrate heating means for heating the base material,
The plurality of slits of the slit plate are provided to be inclined with respect to the traveling direction of the substrate, and the opening of the slit facing the substrate is on the upper side opposite to the direction of gravity, and the base of the slit is A drying apparatus characterized in that the opening opposite to the material is on the lower side in the direction of gravity.   The drying apparatus according to claim 1, wherein the slit plate is provided immediately after the coating head in the running direction of the substrate.   The drying apparatus according to claim 1, wherein a space between the slit plate and the coating head is covered with a cover.   The drying apparatus according to any one of claims 1 to 3, wherein an interval between the slit plate and the base material is 1 mm to 50 mm.

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