JP2010005543A - Reverse gravure coating method and device using this method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reverse gravure coating method which can prevent the generation of a non-uniform film thickness, as well as a device using this method. <P>SOLUTION: This kiss-type reverse gravure coating method is to make a base 10 run reversely to the rotating direction of a gravure roll 11 by rotating the gravure roll 11, and thereby, apply a coating solution remaining inside of diagonal engraved grooves 4 to the base 10. The gravure roll 11 has a plurality of the diagonal engraved grooves 4 formed at a specified angle to a basic line, when the center axis of the gravure roll 11 is considered as the basic line. Further, in the case that the direction where the base 10 comes into contact with the gravure roll 11 is given as a top side, and the diagonal engraved grooves 4 are formed downward from the top side, in the gravure roll 11, the top side is, as a rule, considered as the inlet side of the diagonal line and the bottom as the outlet side of the diagonal line. In this case, it is so arranged that the number "b" of the lines of the one inch-wide diagonal engraved grooves 4 on the outlet side of the diagonal line, is larger than the number "a" of the lines of the one inch-wide diagonal engraved grooves 4 on the inlet side of the diagonal line. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a kiss-type reverse gravure coating method and apparatus for applying a coating liquid on the surface of a gravure roll to a substrate.

  In recent years, the use of a kiss-type reverse gravure coating method for so-called “solid coating” is increasing. The kiss type reverse gravure coating method is a gravure roll immersed in a liquid pan in the direction opposite to the direction of travel of the base material and rotating, adjusted by scraping with the installed doctor blade, and gravure on the base material It is a method of coating while pressing the roll.

  Among them, in recent years, a relatively small gravure roll having a diameter of 100 mm or less is often used in the field of relatively thin film coating such as an optical film. In such a case, the gravure roll engraving pattern is generally one in which a spiral groove called a slanted line shape is dug in the coating width direction. This coating method has a merit that a wide range of coating solutions can be applied with simple settings, and is often used.

  However, in such a kiss-type reverse gravure coating method, it is not so obvious in a thin film system having a wet film thickness of 7 μm or less, but in a low-speed region of 50 m / min or less in coating a thicker film, It was found that non-uniformity of the film thickness at the end of the film becomes a problem. The film thickness non-uniformity at the edge of a normal base material is due to a phenomenon such as thick coating of the edge as described in Patent Document 1, and in Patent Document 1, the edge of the plate is shaved. It has been shown to vary the amount applied.

  In addition, as described in Patent Document 2, non-uniformity of film thickness that is relatively symmetrical with respect to the center, such as curvature of a gravure roll and uneven wear of a doctor blade, is also well known. Various countermeasures have been proposed, such as a break-in operation before using the blade and a device for setting the doctor blade itself.

  However, it was found that an asymmetrical film thickness distribution that cannot be solved by these methods occurs. And this is a uniform amount in the width direction when the application liquid is raked up from the liquid pan by a gravure roll, but the application liquid flows down by gravity along the oblique engraving groove until it is raked up and applied. In addition, it was found that the coating liquid amount decreases on the starting side of the oblique engraving groove and the coating liquid amount increases on the opposite side, so that the film thickness distribution is asymmetric.

Japanese Patent Laid-Open No. 2001-38267 JP 2007-255339

  The objective of this invention is providing the reverse gravure coating method and apparatus which can prevent generation | occurrence | production of a nonuniform film thickness.

  In the reverse gravure coating method according to the first aspect of the present invention, the surface of the gravure roll is formed by rotating the gravure roll having a plurality of oblique engraving grooves that form a predetermined angle with the base line when the center axis of the gravure roll is the base line. After the surplus coating liquid on the surface of the gravure roll is scraped off by a doctor blade and the substrate is run in the direction opposite to the rotation direction of the gravure roll, the coating inside the oblique engraving groove is applied. In the kiss-type reverse gravure coating method for applying a liquid to the substrate, the oblique contact engraving groove is formed from the top to the bottom with the direction in which the substrate and the gravure roll are in contact with each other. When the upper side is defined as the oblique line entrance side and the lower side is defined as the oblique line exit side, the oblique line is determined from the number a of the oblique engraving grooves having a width of 1 inch on the oblique line entrance side. The number of lines b of the oblique engraving groove having a width of 1 inch on the outlet side is large.

  The reverse gravure coating method according to the invention of claim 2 is the reverse gravure coating method of claim 1, wherein the ratio b / a of the number of lines a on the oblique line entrance side and the number of lines b on the oblique line exit side is The value is 1.05 or more and 1.5 or less.

  The reverse gravure coating method according to the invention of claim 3 is the reverse gravure coating method according to claim 2, wherein the reverse gravure coating method corresponds to the position where the coating end of the base material nearest to the oblique line entrance side travels. B / a where the position of the gravure roll is a reference position, the number of lines in the range where the inner width of the gravure roll is within 5 cm from the reference position is a, and the number of lines in other parts is b. Is a value of 1.05 or more and 1.5 or less.

  The reverse gravure coating method according to the invention of claim 4 is the reverse gravure coating method according to any one of claims 1 to 3, wherein the base line is used when the center axis of the gravure roll is a base line. And the oblique engraving groove have a small angle of 30 degrees or more and less than 90 degrees.

  The reverse gravure coating method according to the invention of claim 5 is the reverse gravure coating method according to any one of claims 1 to 4, wherein the static viscosity of the coating solution is 100 mPas or less. Features.

  The reverse gravure coating method according to the invention of claim 6 is the reverse gravure coating method according to any one of claims 1 to 5, wherein the coating liquid inside the oblique engraving groove is applied to the substrate. The coating speed to apply is 50 m / min or less.

  The reverse gravure coating method according to the invention of claim 7 is the reverse gravure coating method according to any one of claims 1 to 6, wherein the diagonal line occupying the widest region in the gravure roll. The number of lines of the engraving groove is less than 100.

  The reverse gravure coating apparatus according to the invention of claim 8 comprises a gravure roll having a plurality of oblique engraving grooves that form a predetermined angle with the base line when the central axis is a base line, and a rotation drive means for rotating the gravure roll. A coating liquid supply means for supplying a coating liquid to the surface of the gravure roll; a doctor blade for adjusting the amount of the coating liquid on the surface of the gravure roll; and a base material traveling means for running the base material, The gravure roll is rotated by the rotation driving means, the coating liquid is supplied to the surface of the gravure roll by the coating liquid supply means, and the excess coating liquid on the surface of the gravure roll is scraped off by the doctor blade. The oblique engraving groove is made to travel in the direction opposite to the rotation direction of the gravure roll by the material traveling means. In the kiss-type reverse gravure coating apparatus for applying the internal coating liquid to the base material, the oblique engraving groove is formed from the top to the bottom with the direction in which the base material and the gravure roll contact each other. In the case where the upper side is defined as the oblique line entrance side and the lower side is defined as the oblique line exit side, the 1 inch width on the oblique line exit side is determined from the number a of the oblique engraving grooves having a width of 1 inch on the oblique line entrance side. The number of lines b of the oblique engraving grooves is large.

  According to the present invention, when a diagonal engraving groove is formed from the top to the bottom with the direction in which the base material and the gravure roll contact each other, the upper side is defined as the diagonal inlet side and the lower side is the diagonal outlet side If the line number b of the 1-inch wide oblique engraving groove on the oblique line exit side is larger than the line number a of the 1-inch wide oblique engraved groove on the oblique line entrance side, Occurrence can be prevented.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a schematic diagram showing a reverse gravure coating apparatus according to Embodiment 1 of the present invention. FIG. 2 is a schematic side view showing a gravure roll of the reverse gravure coating apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the reverse gravure coating apparatus 1 according to Embodiment 1 of the present invention is of a kiss type. The reverse gravure coating apparatus 1 includes a gravure roll 11, a rotation drive device (rotation drive means) 2, a coating liquid supply means 3, a doctor blade 14, and a pair of transport rolls 16 and 17. The rotation drive device 2 is composed of a motor or the like, and rotates the gravure roll 11 in the direction of arrow c. The coating liquid supply means 3 includes a coating liquid storage container 12 and a coating liquid 13 stored in the coating liquid storage container 12. The pair of transport rolls 16 and 17 are arranged at predetermined intervals on both sides of the gravure roll 11. The transport rolls 16 and 17 cause the base material 10 to travel in the direction of the arrow d while pressing the base material 10 against the outer surface of the gravure roll 11. The transport rolls 16 and 17 and the driving device that rotates them constitute base material traveling means for causing the base material 10 to travel in the direction of arrow d.

  The gravure roll 11 is arranged so that the lower part is immersed in the coating liquid 13 of the coating liquid storage container 12. The gravure roll 11 has a plurality of oblique engraving grooves 4 formed in a spiral shape on the outer surface (see FIG. 2). The gravure roll 11 is rotated in the direction of the arrow c by the rotation driving device 2 at the time of coating, and this surface scrapes up the coating liquid 13. The doctor blade 14 is disposed on the side where the gravure roll 11 scoops up the coating solution. The doctor blade 14 adjusts the amount of the coating liquid on the surface of the gravure roll 11.

  The reverse gravure coating apparatus 1 rotates the gravure roll 11 to supply the coating liquid to the surface of the gravure roll 11 and scrapes off the excess coating liquid on the surface of the gravure roll 11 by the doctor blade 14. By running the gravure roll 11 in the direction opposite to the rotation direction (arrow d direction), the surface of the gravure roll 11 is brought into contact with the substrate 10 to apply the coating liquid inside the oblique engraving groove 4 to the substrate 10. The coating film 15 is formed.

  As shown in FIG. 2, the plurality of oblique engraving grooves 4 are formed so that the direction in which the base material 10 and the gravure roll 11 are in contact is up, and the oblique engraving grooves 4 are formed from the top to the bottom. When the oblique line entrance side (the side indicated by the arrow A) is defined and the lower side is defined as the oblique line exit side (the side indicated by the arrow B), the number a of the oblique engraving grooves 4 having a width of 1 inch on the oblique line entrance side is determined. The oblique line engraving groove 4 having a width of 1 inch on the oblique line exit side is formed to have a large number of lines b. The oblique engraving groove 4 is formed so as to have a V-shaped cross section, for example.

  In order to define the coating amount of the coating liquid on the substrate 10, it can be accomplished by changing the number of lines of 1 inch width of the oblique engraving groove 4 applied to the gravure roll 11. As the number of 1-inch wide lines in the oblique engraving groove 4 decreases, the groove becomes deeper and the coating amount of the coating liquid increases.

  FIG. 2 is a schematic side view showing a gravure roll of the reverse gravure coating apparatus according to Embodiment 1 of the present invention. The substrate 10 runs in a direction perpendicular to FIG. In this case, the upper direction is e, and the lower direction is f. The upper side is defined as the hatched inlet side (the side indicated by arrow A), and the lower side is defined as the hatched outlet side (the side indicated by arrow B). In the range where the oblique engraving grooves 4 are formed, when the A-side line number a is set, the B-side line number b is larger than the line number a.

  When the ratio b / a of the number a of lines on the oblique line entrance side and the number b of lines on the oblique line exit side is less than 1.05, the difference in the number of lines is too small and the coating amount tends to be uneven. When the value of the ratio b / a exceeds 1.5, the difference in the number of lines becomes too large and the coating amount tends to be non-uniform.

  Further, the range in which the number of lines is a is a position where the gravure roll 11 corresponding to the position where the coating end of the nearest base material 10 travels on the oblique line entrance side, and the gravure roll 11 from this reference position. It is desirable to have a very limited range of the inner width. The range in which the number of lines in the gravure roll 11 is a is determined by the balance with the coating end position of the traveling substrate.

  For example, the position of the gravure roll 11 corresponding to the position where the coating end of the nearest base material 10 travels on the oblique line entrance side is set as the reference position, and the line within the range where the inner width of the gravure roll 11 is within 5 cm from the reference position. When the number is a and the number of lines in other parts is b, the value of b / a is preferably 1.05 or more and 1.5 or less.

  The number of lines can be changed in a plurality of stages. For example, the number of lines may be changed in two stages as indicated by a line 18 in FIG. 3, or may be changed in three stages as indicated by a line 19.

  The phenomenon which is a problem in the present invention is born when the coating amount is relatively large. This is because, when the number of lines is large, the amount of coating liquid that is scraped up is small, so that the resulting difference in coating amount is small. Even when the application speed of the application liquid is high, the rotation of the gravure roll 11 becomes faster, so that the time from scratching to application becomes shorter and the application liquid is applied before dropping, which is a big problem. do not become. Therefore, the effect of the present invention can be expected when the number of lines b occupying the widest area in the gravure roll 11 is 100 or less and the coating speed is 50 m / min or less.

  As shown in FIG. 2, the angle of the oblique engraving groove 4 engraved on the gravure roll 11 is a small angle 21 formed by the base line 20 and the oblique engraving groove 4 when the central axis of the gravure roll 11 is the base line 20. Is preferably 30 degrees or more and less than 90 degrees. When the angle 21 is less than 30 degrees, the influence of gravity is small, so that there is little problem even if the present invention is not used.

  The gravure roll 11 is formed of a metal material or ceramics. The doctor blade 14 is formed of a metal material, a resin material, ceramic plating, or the like, and the influence of the doctoring method is irrelevant to the present invention.

  The base material 10 is made of paper or plastic film. In general, as a material of the substrate 10 for an optical film in which kiss-type reverse gravure coating is often used, for example, a cellulose film such as acetyl cellulose and triacetyl cellulose, a polyester film such as polyethylene terephthalate and polyethylene naphthalate, or Examples thereof include, but are not limited to, acrylic films such as polymethyl methacrylate. Moreover, the base material 10 may consist of a single layer, and may consist of a some layer. The thickness of the substrate 10 is preferably 10 to 500 μm.

  The coating solution 13 is not particularly limited as long as it can be coated with a kiss type reverse gravure coater. Among them, the present invention is effective in a relatively low viscosity coating solution having a static viscosity of 100 mPas or less. It is. The static viscosity of the coating solution can be measured with a vibration viscometer or a B-type viscometer. Such a low-viscosity coating liquid is generally a dispersion dissolved in a diluting solvent such as an organic solvent.

  What is used as the dilution solvent is not particularly limited, but considering the stability of the composition, volatility with respect to the coating film, alcohols such as methanol, ethanol, isopropanol, butanol, 2-methoxyethanol, acetone, Ketones such as methyl ethyl ketone and methyl isobutyl, 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, ethyl cellosolve, butyl cellosolve and ethyl carb Glycol ethers such as tall and butyl carbitol, aliphatic hydrocarbons such as hexane, heptane and octane, halogenated hydrocarbons, aromatic hydrocarbons such as benzene, toluene and xylene, N-methylpyrrolidone Dimethylformamide and the like are. These solvents may be used as one kind or a mixture of two or more kinds.

  In the conventional coating method, the amount of coating liquid decreases on the starting point side of the oblique engraving groove (indicated by the oblique line entrance), and the amount of coating liquid increases on the opposite side (the oblique line exit side), so the film thickness becomes asymmetrical. ing. On the other hand, in the first embodiment of the present invention, when the oblique engraving groove 4 is formed from the top to the bottom with the direction in which the substrate 10 and the gravure roll 11 are in contact with each other, the upper side is the oblique entrance. When the lower side is defined as the hatched exit side, the number b of the 1 inch wide hatched engraving groove 4 on the hatched exit side is less than the number a of the 1 inch wide hatched groove 4 on the hatched entrance side. Since it is large, it is possible to increase the coating amount of the coating liquid on the oblique line entrance side as compared with the conventional case, so that it is possible to prevent the occurrence of uneven film thickness.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 4 is a schematic diagram showing a kiss-type reverse gravure coater according to Embodiment 2 of the present invention.

  As shown in FIG. 4, the kiss type reverse gravure coater according to the second embodiment of the invention includes a reverse gravure coating apparatus 1, a feeding roll 25, conveying rolls 26, 27 and 28, a drying apparatus 23, A radiation device 24 and a winding roll 29 are provided. The film-like substrate 10 fed from the feeding roll 25 is conveyed in the direction of arrow g, conveyed by the conveying rolls 16 and 17 and the conveying rolls 26, 27, and 28 of the reverse gravure coating apparatus 1, and is taken up by the winding roll 29. It is wound up.

  When the base material 10 is conveyed, the reverse gravure coating apparatus 1 applies a coating liquid to form a coating film 15. Next, after the coating film 15 of the base material 10 is dried by the drying device 23, the coating film 15 of the base material 10 is cured by receiving ionizing radiation emitted from the radiation device 24.

(Example)
Next, examples of the present invention will be described.
A polyethylene terephthalate material having a width of 650 mm is used as the base material 10, and a 50 wt% acrylic UV curable resin using methyl ethyl ketone (MEK) and methyl acetate as dilution solvents by a reverse gravure coater as shown in FIG. The coating film 15 was applied to the base material 10 at a speed of 30 m / min so that the wet film thickness was 25 μm.

  The gravure roll 11 used has an oblique engraving groove 4 having a diameter of 50 mm and a small angle 21 formed by the base line 20 and the oblique engraving groove 4 is 45 degrees. The coating solution 13 has a viscosity of 4 mPas and a surface tension of 25 mN / m. The film thickness of 10 representative points in the width direction of the coating film 15 is measured with a contact-type film thickness meter, and the film thickness distribution of 3% is marked as ◯, and the film thickness not included is marked as x. Judged. The results are shown in the following table.

table

It is the schematic which shows the reverse gravure coating apparatus which concerns on Embodiment 1 of this invention. It is a schematic side view which shows the gravure roll of the reverse gravure coating apparatus which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the number of lines of the oblique engraving groove | channel of the gravure roll which concerns on Embodiment 1 of this invention. It is the schematic which shows the kiss type reverse gravure coater which concerns on Embodiment 2 of this invention.

Explanation of symbols

1 Reverse gravure coating device 2 Rotation drive device (Rotation drive means)
DESCRIPTION OF SYMBOLS 3 Coating liquid supply means 4 Diagonal engraving groove 10 Base material 11 Gravure roll 12 Coating liquid storage container 13 Coating liquid 14 Doctor blade 15 Coating film 16, 17 Conveyance roll

Claims (8)

When the center axis of the gravure roll is used as a base line, the gravure roll having a plurality of oblique engraving grooves that form a predetermined angle with the base line is rotated to supply a coating liquid to the surface of the gravure roll, and the surface of the gravure roll by a doctor blade After the excess coating solution is scraped off, the substrate is moved in the direction opposite to the rotation direction of the gravure roll to thereby apply the coating solution inside the oblique engraving groove to the substrate. In the construction method,
When the oblique engraving groove is formed from the top to the bottom, the upper side is defined as the oblique line entrance side and the lower side is defined as the oblique line exit side when the direction in which the base material and the gravure roll are in contact is the top. In this case, the reverse gravure coating method is characterized in that the number b of the 1-inch wide oblique engraving grooves on the oblique line exit side is larger than the number a of the 1-inch wide oblique engraving grooves on the oblique entrance side.   2. The ratio b / a between the number of lines a on the oblique line entrance side and the number of lines b on the oblique line exit side is 1.05 or more and 1.5 or less. Reverse gravure coating method.   The number of lines in the range where the position of the gravure roll corresponding to the position where the coating end of the base material nearest to the oblique line entrance side travels is a reference position, and the inner width of the gravure roll is within 5 cm from the reference position The value of b / a is 1.05 or more and 1.5 or less, where a is a and the number of lines in other parts is b. The reverse gravure coating method described.   When the center axis of the gravure roll is a base line, the small angle formed by the base line and the oblique engraving groove is 30 degrees or more and less than 90 degrees. Item 4. The reverse gravure coating method according to any one of Items 3 above.   The reverse gravure coating method according to any one of claims 1 to 4, wherein the static viscosity of the coating solution is 100 mPas or less.   The reverse gravure coating according to any one of claims 1 to 5, wherein a coating speed at which the coating liquid inside the oblique engraving groove is applied to the substrate is 50 m / min or less. Method.   The reverse gravure coating method according to any one of claims 1 to 6, wherein the number of lines of the oblique engraving grooves that occupy the widest region in the gravure roll is less than 100. A gravure roll having a plurality of oblique engraving grooves that form a predetermined angle with the base line when the central axis is a base line, a rotation driving means for rotating the gravure roll, and a coating liquid that supplies the coating liquid to the surface of the gravure roll A supply means, a doctor blade for adjusting the amount of the coating liquid on the surface of the gravure roll, and a base material traveling means for causing the base material to travel,
The gravure roll is rotated by the rotation driving means, the coating liquid is supplied to the surface of the gravure roll by the coating liquid supply means, and the excess coating liquid on the surface of the gravure roll is scraped off by the doctor blade. In a kiss-type reverse gravure coating apparatus that applies the coating liquid inside the oblique engraving groove to the substrate by running the substrate in a direction opposite to the rotation direction of the gravure roll by a material running means,
When the oblique engraving groove is formed from the top to the bottom, the upper side is defined as the oblique line entrance side and the lower side is defined as the oblique line exit side when the direction in which the base material and the gravure roll are in contact is the top. In this case, the reverse gravure coating apparatus is characterized in that the number b of the 1-inch wide oblique engraving groove on the oblique line exit side is larger than the number a of the 1-inch wide oblique engraving groove on the oblique entrance side.

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