Gravure Roll

Abstract

To provide a gravure roll which can form a more uniform coating film.SOLUTION: A gravure roll includes: a first wall part provided along an entire first side, which is one side extending in a rotation direction of the gravure roll, of four sides of each cell; a second wall part provided along a part, which is connected to the first side, of a second side, which is one side located adjacent to the first side; a third wall part provided along an entire third side facing the first side; and a fourth wall part provided along a part, which is connected to the third side, of the fourth side facing the second side. The first and second wall parts and the third and fourth wall parts are formed so as to be point-symmetric with respect to a center of each cell. An angle formed by the first wall part and the third wall part relative to the rotation direction of the gravure roll ranges from -30° to 20°(however, excluding 0°).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a gravure roll.

Background Art

[0002] As methods for coating a coating liquid on a substrate, a gravure coating method, a micro gravure coating method, a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, an extrusion coating method, and the like are known.

[0003] For example, Patent Document 1 describes that the micro gravure coating method is preferable as a method for applying a coating liquid to a film. In Patent Document 1, a gravure roll having a gravure pattern engraved on the entire circumference is disposed below the film, and while the gravure roll is rotated reversely with respect to the conveyance direction of the film, a fixed amount of the coating liquid is transferred to the lower surface of the support and coated.

[0004] Further, Patent Document 2 describes that when applying an ink containing a phosphorescent flake by gravure printing, by using a rotogravure plate having a cell structure with a notch between cells, it becomes difficult to discriminate the transferred cell pattern.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] When forming a coating on a web using the reverse gravure method, a bead is formed between the web and the gravure roll. Depending on the cell pattern of the gravure roll, the coating liquid may flow in a direction perpendicular to the web transport direction, making the bead between the web and the gravure roll prone to collapse. As the web transport speed or the rotation speed of the gravure roll increases, the collapse of the bead becomes even more pronounced, resulting in streaky surface defects in the coating.

[0007] Therefore, the present invention aims to provide a gravure roll capable of forming a more uniform coating film. [Means for solving the problem]

[0008] The gravure roll according to the present invention is a gravure roll in which a plurality of parallelogram-shaped rotoflow type cells partitioned by partition walls are provided on the outer circumferential surface of the roll body, wherein the plurality of cells are arranged such that adjacent cells in the rotational direction of the gravure roll are aligned diagonally with respect to the rotational direction of the gravure roll, and the partition wall has a first wall portion provided along the entire first side which is one of the four sides of each cell that extends in the rotational direction of the gravure roll, a second wall portion provided along a part of the second side which is one of the sides adjacent to the first side that is connected to the first side, a third wall portion provided along the entire third side which is opposite to the first side, and a fourth wall portion provided along a part of the fourth side which is opposite to the second side that is connected to the third side. No partition wall is formed on the second side to connect with the third wall, and no partition wall is formed on the fourth side to connect with the first wall. The first and second walls, and the third and fourth walls, are formed to be point-symmetric with respect to the center of each cell. When the sign of the angle that the direction in which adjacent cells are aligned relative to the rotation direction of the gravure roll makes with respect to the rotation direction of the gravure roll is taken as positive, the angle that the first and third walls make with respect to the rotation direction of the gravure roll is between -30° and 20° (excluding 0°). [Effects of the Invention]

[0009] According to the present invention, a gravure roll capable of forming a more uniform coating film can be provided. [Brief explanation of the drawing]

[0010] [Figure 1] A perspective view showing the schematic configuration of a gravure roll according to the embodiment. [Figure 2] A diagram showing a collection of cells in a gravure roll according to the embodiment. [Figure 3] Enlarged view of one cell of the gravure roll according to the embodiment. [Figure 4] Diagram explaining angle α [Figure 5] A diagram showing a gravure roll with diagonal lines engraved on it, relating to a comparative example. [Figure 6] A diagram showing the relationship between the cell shape of the gravure roll, its rotational speed, and its transport speed. [Modes for carrying out the invention]

[0011] Figure 1 is a perspective view showing the schematic configuration of a gravure roll according to the embodiment, Figure 2 is a diagram showing the collection of cells of the gravure roll according to the embodiment, and Figure 3 is an enlarged view of one cell of the gravure roll according to the embodiment. In Figures 1 to 3, the direction of rotation of the gravure roll is indicated by an arrow.

[0012] The gravure roll 100 has a substantially cylindrical shape, is rotatably supported around a central axis, and applies the coating liquid to the surface of the substrate while rotating in a predetermined rotational direction. The gravure roll 100 is preferably made of a metal containing carbon copper because it is less prone to bending, but it may also be made of a single metal or multiple metals. The outer diameter of the gravure roll 100 is 45 mm or more, and is particularly preferably 50 mm. Multiple cells 1 for holding the coating liquid are formed on the outer circumferential surface of the gravure roll 100. The multiple cells 1 are formed, for example, in the patterned coating area shown in Figure 1.

[0013] As shown in Figure 3, each cell 1 has a parallelogram shape in the unfolded diagram, and each is partitioned by a partition wall 2. As will be described in detail later, multiple cells 1 are arranged such that adjacent cells 1 in the direction of rotation of the gravure roll 100 are aligned diagonally with respect to the direction of rotation of the gravure roll 100 (in the direction of the dotted line in Figure 2).

[0014] The partition wall 2 comprises a first wall portion 21, a second wall portion 22, a third wall portion 23, and a fourth wall portion 24, each partitioning one of the multiple cells 1. The first wall portion 21 is provided along the entire first side 21', which is one of the four sides of cell 1 that extends in the direction of rotation of the gravure roll 100. The second wall portion 22 is provided along a portion of the second side 22', which is one of the sides adjacent to the first side 21', that is connected to the first side 21'. The third wall portion 23 is provided along the entire third side 23', which is opposite the first side 21'. The fourth wall portion 24 is provided along a portion of the fourth side 24', which is opposite the second side 22', that is connected to the third side 23'. Cell 1 may be a rhombus in which the first side 21', second side 22', third side 23', and fourth side 24' are equal.

[0015] The first wall portion 21 and the second wall portion 22, and the third wall portion 23 and the fourth wall portion 24 are formed to be point-symmetric with respect to the center (centroid) of cell 1. Therefore, the lengths of the second wall portion 22 and the fourth wall portion 24 are equal. Thus, if the portion along the second side 22' in which the second wall portion 22 is not formed is called notch a, and the portion along the fourth side 24' in which the fourth wall portion 24 is not formed is called notch b, then the lengths of notch a and notch b are also the same. Cells 1 adjacent to each other in the rotational direction of the gravure roll 100 are connected by notches a and b. The widths of notches a and b can be, for example, 145 μm, and the ratio of the widths of notches a and b to the widths of the second wall portion 22 and the fourth wall portion 24 can be 2:3.

[0016] Figure 4 is a diagram illustrating the angle α shown in Figure 3.

[0017] The angle α formed by the first wall portion 21 and the third wall portion 23 with respect to the rotation direction of the gravure roll 100 is -30° or more and 20° or less (excluding 0°) with respect to the rotation direction of the gravure roll 100, when the sign of the angle formed by the arrangement direction of the cells 1 adjacent to the rotation direction of the gravure roll 100 with respect to the rotation direction of the gravure roll 100 is taken as positive. For example, in FIG. 3, the angle α is a negative value. When the angle α becomes smaller than -30°, the second wall portion 22 and the fourth wall portion 24 of the cell 1 approach the axial direction of the gravure roll 100 (the direction perpendicular to the circumferential direction of the gravure roll 100) (FIG. 4(a)). Therefore, the shapes of the second wall portion 22 and the fourth wall portion 24 of the cell 1 may be transferred. Also, when the angle α exceeds 20°, the centers of the cells 1 are continuous in the direction of 45° with respect to the rotation direction (FIG. 4(b)). In this case, the flow of the coating liquid between the adjacent cells 1 deteriorates, and there is a risk that the transfer of the coating liquid becomes non-uniform. Further, when the angle α is 0°, the first wall portion 21 and the third wall portion 23 are intermittently arranged along the circumferential direction of the gravure roll 100, respectively. When the partition wall 2 is intermittent or continuous in the circumferential direction, a flow of liquid in the running direction of the base material may occur due to the partition wall 2 (the first wall portion 21 and the third wall portion 23) of the cell 1 formed in the circumferential direction, and there is a risk of streak-like surface defects occurring.

[0018] The angle formed by the second wall portion 22 and the fourth wall portion 24 with respect to the axial direction of the gravure roll 100 is preferably other than 0°. In the case of 0°, the second wall portion 22 and the fourth wall portion 24 are formed in the axial direction of the gravure roll 100, and there is a risk that the shapes of the second wall portion 22 and the fourth wall portion 24 of the cell 1 are transferred.

[0019] FIG. 5 is a view showing a gravure roll having a slant-type engraving according to a comparative example.

[0020] Here, the gravure roll 100 according to the invention of the present application is compared with the gravure roll of the comparative example shown in FIG. 5. When forming a coating film on a web by the reverse gravure method, a bead is formed between the web and the gravure roll. As shown in FIG. 5, when the engraving pattern provided on the gravure roll is parallel diagonal lines (spirals), as the gravure roll rotates, the coating liquid flows along the diagonal lines, so a flow of the coating liquid occurs in a direction orthogonal to the conveyance direction of the web (the axial direction of the gravure roll). The flow of the coating liquid in the axial direction of the gravure roll causes the bead between the web and the gravure roll to collapse, and surface unevenness defects due to the collapse of the bead occur in the coating film. Since this surface unevenness defect becomes prominent as the conveyance speed of the web or the rotation speed of the gravure roll increases, a gravure roll having an engraving pattern that easily causes a flow of the coating liquid in the axial direction, as in the comparative example, is not suitable for high-speed coating.

[0021] In contrast, in the invention of the present application, as shown in FIG. 2, a plurality of cells 1 of the rotogravure type are arranged so as to be arranged obliquely with respect to the rotation direction of the gravure roll 100, and cutouts a and b are provided between adjacent cells 1. When a plurality of rotogravure-type cells 1 are arranged in this way, the coating liquid held in the ink pocket of the cell 1 is more likely to flow in the rotation direction than in the length direction of the gravure roll 100. When the bead on the gravure roll 100 flows in the rotation direction of the gravure roll, the collapse of the bead is less likely to occur, so that surface unevenness defects of the coating film can be reduced and high-speed coating can also be realized.

[0022] Furthermore, in the invention of the present application, since the first wall portion 21 and the third wall portion 23 are not arranged intermittently or continuously along the circumferential direction of the gravure roll 100, streak-like surface unevenness defects can be reduced.

[0023] The width W of cell 1 in the direction perpendicular to the first wall 21 and the third wall 23 is preferably 45 lines / inch or more and 200 lines / inch or less. If it is less than 45 lines / inch, the coating film will be thicker, making it easier for uneven coating to occur, and if it exceeds 200 lines / inch, the required processing accuracy of cell 1 will be higher. If the width W of cell 1 (spacing between partition walls 2) is 45 lines / inch or more and 200 lines / inch or less, it is superior in both reducing uneven coating and the processing accuracy of the gravure roll 100. In addition, the width of the partition wall 2 provided between adjacent cells 1 is preferably 0.025 to 0.028 mm.

[0024] The depth from the enveloping surface on the upper surface of the partition wall 2 to the deepest part of cell 1 is preferably 30 μm to 170 μm. If it is less than 30 μm, the required processing accuracy of cell 1 will be higher, and if it exceeds 170 μm, the coating film will be thicker, making transfer unevenness more likely. If the depth of cell 1 is 30 μm to 170 μm, it is superior in both the processing accuracy of the gravure roll 100 and the reduction of coating film unevenness. [Examples]

[0025] (Examples) As an example, a gravure roll having cells 1 with the shape shown in Figures 2 and 3 was fabricated. The outer diameter of the gravure roll was 50.5 mm, the width of the area where the cells are provided (axial length of the gravure roll) was 1475 mm, the depth of the deepest part of cell 1 was 130 μm, the angle α was -15°, the width of the partition wall 2 separating cell 1 was 25 mm, and the width W of cell 1 (distance between partition walls 2) was 380 μm.

[0026] (Comparative example) As an example, a gravure roll with the diagonal line engraving shown in Figure 5 was fabricated. The angle that the diagonal line engraving makes with respect to the axial direction of the gravure roll was set to 45°.

[0027] Using the gravure rolls described in the examples and comparative examples, a coating solution for forming an anti-glare (AG) layer was applied to an acrylic film with a thickness of 60 μm. After drying the coating film, it was cured by ultraviolet irradiation. Multiple coatings were performed while varying the web transport speed and the rotation speed of the gravure roll during coating, and optical film samples were obtained for each coating condition (combination of transport speed and rotation speed).

[0028] <Evaluation of coating film uniformity> The uniformity of the coating film was evaluated by observing the surface of the cured film in optical films prepared using the gravure rolls described in the examples and comparative examples, using reflected and transmitted light.

[0029] <Method for observing the surface of a hardened film using reflected light> A black PET (polyethylene terephthalate) film was laminated to the back side (substrate side) of the film. Next, in a darkroom, a three-wavelength fluorescent lamp (1500 lx or more) was shone from the coated surface side, and the condition of the coating was visually observed. Specifically, the distance between the light source and the coated surface was set to 60 cm, and the distance between the inspector's eye and the coated surface was also set to 60 cm, so that the angle between the illuminated light and the coated surface was approximately 90°, and the illuminated surface was observed from a vertical direction.

[0030] <Method for observing the surface of a coating film using transmitted light> In a darkroom, the film was illuminated from the back side (substrate side) with a three-wavelength fluorescent lamp (1500 lux or more), and the condition of the coating was visually observed. Specifically, the distance between the light source and the coated surface was 60 cm, and the distance between the inspector's eye and the coated surface was 80 cm. The angle between the illuminated light and the coated surface was varied between 40 and 60°, and the coating was observed from the coated surface side.

[0031] Figure 6 is a plot showing the surface evaluation results of optical films produced using gravure rolls according to the examples and comparative examples, plotted for each coating condition. In Figure 6, the plots represented by solid circles indicate the surface evaluation results of optical films obtained by coating using gravure rolls according to the examples. The plots represented by solid circles indicate that there were no surface defects such as fine streaks along the transport direction, as observed using both reflected and transmitted light methods.

[0032] In Figure 6, the plots indicated by dashed circles show the evaluation results of the optical film surface obtained by coating using a gravure roll in the comparative example. The plots indicated by dashed circles indicate that there were no surface defects such as fine streaks along the transport direction, as observed using both reflected and transmitted light methods.

[0033] In Figure 6, the plots marked with an "x" indicate the evaluation results of the optical film surface obtained by coating using a gravure roll related to the comparative example. The "x" plots indicate that surface defects such as fine streaks along the transport direction were confirmed by either the reflected light or transmitted light observation method.

[0034] As shown in Figure 6, when using the gravure roll according to the embodiment, no surface defects due to uneven coating occurred even when the web transport speed and the rotation speed of the gravure roll exceeded 50 m / min. When using the diagonal gravure roll according to the comparative example, as shown by the dashed circle plot, no surface defects due to uneven coating occurred when the substrate transport speed and the rotation speed of the gravure roll were low (generally less than 30 m / min). However, when the substrate transport speed and the rotation speed of the gravure roll were low (30 m / min or more), surface defects due to uneven coating occurred.

[0035] From the above, it has been confirmed that when using the gravure roll 100 according to the present invention, a uniform coating film can be formed on the surface without streaky surface defects, etc., during the application of the coating liquid, and that high-speed coating with a conveying speed and / or rotation speed of 30 m / min or more is also possible. [Industrial applicability]

[0036] This invention can be used in gravure rolls for applying coating liquids to substrates. [Explanation of Symbols]

[0037] 1 cell 2 partition walls 21 First wall section 21' First side 22 Second wall section 22' Second side 23 Third Wall 23' Third side 24 The fourth wall 24' Fourth side α angle W width 100 Gravure Rolls

Claims

1. A gravure roll having a plurality of parallelogram-shaped rotoflow type cells partitioned by partition walls on the outer circumferential surface of the roll body, The multiple cells are arranged such that adjacent cells in the rotational direction of the gravure roll are aligned diagonally with respect to the rotational direction of the gravure roll. The partition wall is, A first wall portion is provided along the entire length of the first side, which is one of the four sides of the cell that extends in the rotational direction of the gravure roll, A second wall portion is provided along a part of the second side that is adjacent to the first side and connected to the first side, A third wall portion is provided along the entire length of the third side opposite to the first side, It has a fourth wall portion provided along a part of the fourth side that is connected to the third side, which is opposite to the second side, No partition wall is formed on the second side that connects to the third wall. No partition wall is formed on the fourth side that connects to the first wall. The first wall portion and the second wall portion, and the third wall portion and the fourth wall portion are formed to be point-symmetric with respect to the center of each of the cells, A gravure roll in which, when the sign of the angle that the direction in which the cells adjacent to the rotation direction of the gravure roll make with respect to the rotation direction of the gravure roll is taken as positive, the angle that the first wall portion and the third wall portion make with respect to the rotation direction of the gravure roll is -30° or more and 20° or less (excluding 0°).

2. The gravure roll according to claim 1, wherein the width of the cell is 45 lines / inch or more and 200 lines / inch or less.

3. The gravure roll according to claim 1 or 2, wherein the depth from the enveloping surface of the upper surface of the partition wall to the deepest part of the cell is 30 μm or more and 170 μm or less.

Images