Gravure printing roll

Abstract

A gravure printing roll that enables printing of fine dots with a size close to that of cells and enables printing on a print subject, such as a printing substrate, without changing the appearance of the print subject. The gravure printing roll includes: a gravure printing roll body; and cells formed in a peripheral surface of the gravure printing roll body. Each of the cells has an opening with a ratio between a dimension in a circumferential direction of the gravure printing roll body and a dimension in an axial center direction of the gravure printing roll body (dimension in the circumferential direction/dimension in the axial center direction) being 1.15 to 7, and have an opening area of 3900 m.sup.2 or smaller.

Claims

1. A gravure printing roll comprising: a gravure printing roll body; and cells formed in a peripheral surface of the gravure printing roll body, the cells each having an opening with a ratio between a dimension in a circumferential direction of the gravure printing roll body and a dimension in an axial center direction of the gravure printing roll body, dimension in the circumferential direction/dimension in the axial center direction, being 1.16 to 5.27, the cells each having an opening area of 675 to 3869 m.sup.2 and a formation density of the cells in the gravure printing roll being 25 cells/mm.sup.2 or smaller.

2. The gravure printing roll according to claim 1, wherein the opening of each of the cells has a rectangular shape.

3. The gravure printing roll according to claim 1, wherein the cells each have a depth of 6 to 25 m.

4. The gravure printing roll according to claim 2, wherein the cells each have a depth of 6 to 25 m.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a perspective view illustrating a gravure printing roll.

(2) FIG. 2 is a plan view illustrating a cross section of a cell.

(3) FIG. 3 is a plan view illustrating an opening of a cell.

(4) FIG. 4 is a plan view illustrating openings of cells.

(5) FIG. 5 is a schematic view illustrating the ink in a cell in the middle of being transferred onto a print subject.

(6) FIG. 6 is a diagram illustrating cells adjacent to each other.

(7) FIG. 7 is a diagram illustrating cells adjacent to each other.

(8) FIG. 8 is a schematic view illustrating a gravure printer.

DESCRIPTION OF EMBODIMENTS

(9) An example of a gravure printing roll of the present invention will be described with reference to the drawings. As shown in FIG. 1, a gravure printing roll A is configured to include a large number of cells 2 formed in a peripheral surface of a gravure printing roll body 1.

(10) The cells 2 having openings are formed in a peripheral surface 11 of the gravure printing roll body 1. More specifically, the cells 2 having openings are formed all over a surface part 12 of the gravure printing roll body 1.

(11) As shown in FIG. 2, the cell 2 includes: a bottom surface 2a formed in a concave arc shape in cross section; and a peripheral wall part 2b gradually extending outward from a peripheral edge of the bottom surface 2a toward the peripheral surface (surface) of the gravure printing roll body 1. The bottom surface 2a smoothly connects with the peripheral wall part 2b by intermediary of a concave arc part 2c, so that an ink in the cell 2 can be smoothly withdrawn.

(12) As shown in FIGS. 3 and 4, a ratio between a dimension in a circumferential direction X of the gravure printing roll body 1 and a dimension in an axial center direction Y of the gravure printing roll body 1 (dimension in the circumferential direction/dimension in the axial center direction) (hereinafter referred to simply as a dimension ratio) in an opening of the cell 2 is 1.15 to 7, preferably 1.2 to 7, and more preferably 1.2 to 6. The dimension ratio of the cell 2 set to be 1.15 or greater can reduce adhesion between the cell 2 and the ink. This can also facilitate the withdrawal of the ink from the cell 2 and thus ensure the withdrawal of the ink from the cell. This also enables sharp dot printing on a print subject without producing an unprinted portion. The dimension ratio of the cell 2 set to be 7 or smaller can prevent the ink from breaking off during the separation of the ink from the cell 2. This also enables the ink to be smoothly withdrawn from the cell 2 and transferred to the print subject. Thus, sharp and accurate dot printing can be achieved on the print subject without producing an unprinted portion.

(13) The circumferential direction X of the gravure printing roll body 1 refers to a rotational direction, i.e., print direction of the gravure printing roll body 1. The axial center direction Y of the gravure printing roll body 1 refers to a direction perpendicular to the rotational direction of the gravure printing roll body 1.

(14) When two straight lines L.sub.1, L.sub.1 intersecting or in contact with the cell 2 and parallel to the axial center direction of the gravure printing roll body 1 are drawn, the dimension of the cell in the circumferential direction of the gravure printing roll body 1 refers to a maximum distance W.sub.1 between the two straight lines L.sub.1, L.sub.1.

(15) When two straight lines L.sub.2, L.sub.2 intersecting or in contact with the cell 2 and parallel to the circumferential direction of the gravure printing roll body 1 are drawn, the dimension of the cell in the axial center direction of the gravure printing roll body 1 refers to a maximum distance W.sub.2 between the two straight lines L.sub.2, L.sub.2.

(16) The shape of the opening of the cell 2 is not limited to a particular shape so long as the above-described dimension ratio and an opening area to be described later fall within respective predetermined ranges. Examples of the shape of the opening include polygons, such as a triangle (for example, FIG. 4(b)), a quadrangle, a pentagon, and a hexagon (for example, FIG. 4(d)). Preferred shapes are a triangle and a quadrangle, and a more preferred shape is a rectangle. Examples of the quadrangle include a rectangle (for example, FIG. 4(a)) and a parallelogram (such as a rhombus (for example, FIG. 4(c))). Note that corners of such a polygon may be formed in an arc shape. Each side of the polygon does not need to be straight, but may be curved.

(17) Although the mechanism that enables the ink in the cell 2 to be smoothly transferred and fixed to the print subject by setting the dimension ratio of the cell within the above-described range has not been made clear, the following is thought to be the reason.

(18) As shown in FIG. 5, an ink C is first fed into the cells 2 of the gravure printing roll A in order to perform printing on a print subject B with the gravure printing roll A. Thereafter, the print subject B is fed between the gravure printing roll A and a back-up roll 3, and the ink C in the cells 2 of the gravure printing roll A is transferred and fixed onto the print subject B.

(19) More specifically, the print subject B is first in contact with the openings of the cells 2. As shown in FIG. 5, the print subject B is gradually separated from the openings of the cells 2 along with the rotation of the gravure printing roll A. The print subject B is sequentially stripped off starting with the leading side of the gravure printing roll A in the rotational direction. The ink C withdrawn from the cells 2 is sequentially transferred to the stripped portion. In order for the ink C to be withdrawn from the cell 2 and transferred to the print subject B, adhesion between the print subject B and the ink C needs to be greater than adhesion between the cell 2 and the ink C. In view of this, the dimension ratio in the opening of the cell 2 in the above-described gravure printing roll A is set to 1.15 to 7, so that the opening of the cell 2 has a shape elongated in the circumferential direction of the gravure printing roll body 1. When cells having the same opening area are compared with each other, one with a shape elongated in the circumferential direction X of the gravure printing roll body 1 can reduce adhesion between the cell 2 and the ink C due to its reduced ink amount in the axial center direction Y. Consequently, the adhesion between the print subject B and the ink C can be made greater than the adhesion between the cell 2 and the ink C. This is assumed to be the reason why the ink C can be easily withdrawn from the cell 2 and easily transferred and fixed onto the print subject B.

(20) The opening area of the cell 2 in the gravure printing roll A is 3900 m.sup.2 or smaller, preferably 3600 m.sup.2 or smaller, more preferably 2500 m.sup.2 or smaller, and particularly preferably 2000 m.sup.2 or smaller. The opening area of the cell 2 set to be 3900 m.sup.2 or smaller enables the printing of fine dots with a diameter of 100 m or smaller, in particular, fine dots with a diameter of about 20 to 50 m, which can be hardly identified by human eyes.

(21) The opening area of the cell 2 in the gravure printing roll A is preferably 200 m.sup.2 or greater, more preferably 300 m.sup.2 or greater, and particularly preferably 400 m.sup.2 or greater. The opening area of the cell 2 set to be 200 m.sup.2 or greater enables smoother withdrawal of the ink from the cell 2 and sharp dot printing on the print subject.

(22) The depth of the cell 2 in the gravure printing roll A is preferably 6 to 25 m, and more preferably 10 to 25 m. The depth of the cell 2 set within the aforementioned range enables smoother withdrawal of the ink from the cell 2 and sharp dot printing on the print subject. Note that the depth of the cell 2 refers to the depth of the deepest portion.

(23) The interval between the cells 2 adjacent to each other in the gravure printing roll A may be any distance as long as the ink parts withdrawn from the respective cells 2 and transferred to the print subject are prevented from being merged and integrated with each other on the print subject. Specifically, the interval between the cells 2 adjacent to each other in the gravure printing roll A is preferably 50 to 1000 m, more preferably 100 to 800 m, and particularly preferably 150 to 500 m.

(24) Note that cells adjacent to each other and an interval therebetween are defined in the following manner. As shown in FIG. 6, a perfect circle D with the minimum diameter capable of surrounding the opening of the cell is drawn, and then the center of the perfect circle D is defined as a cell center S.

(25) A straight line L.sub.3 connecting between the cell centers S, S of cells 21 and 22 is drawn. As shown in FIG. 6, if there is no other cell on the straight line L.sub.3, the cell 21 and the cell 22 have an adjacent relationship to each other. As shown in FIG. 7, on the other hand, if another cell 23 is present on the straight line L.sub.3, the cell 21 and the cell 22 have no adjacent relationship to each other.

(26) The interval between the cells adjacent to each other refers to a distance W.sub.3 between points R.sub.1 and R.sub.2 at which the straight line L.sub.3 intersects with the opening edges of the cells 21 and 22.

(27) The formation density of the cells 2 in the gravure printing roll A is preferably 25 cells/mm.sup.2 or smaller, more preferably 10 cells/mm.sup.2 or smaller. The formation density of the cells 2 set within the aforementioned range enables the ink parts withdrawn from the respective cells in the gravure printing roll A and transferred onto the print subject to be transferred and fixed onto the print subject independently without being merged with one another. Thus, sharp dots can be printed on the print subject.

(28) A method for manufacturing the gravure printing roll A will be described next. The gravure printing roll A can be manufactured by known manufacturing methods.

(29) The gravure printing roll body 1 described above is typically made of a metal such as iron or aluminum. The surface of the gravure printing roll body 1 includes a plating layer (surface layer) made of copper, for example. The cells 2 are then formed on the surface of the plating layer in the gravure printing roll body 1 by a chemical method or a mechanical method. In this manner, the gravure printing roll A can be manufactured. Note that the surface of the plating layer is subjected to chrome plating, for example, after the formation of the cells 2 in the plating layer of the gravure printing roll body 1.

(30) As a method for forming cells by a chemical method, the surface of the plating layer of the gravure printing roll body 1 is subjected to mirror polishing, and then a photosensitizer is applied to the surface of the plating layer (surface layer). After the photosensitizer is cured so as to form a negative type of a cell pattern (dot pattern), uncured part of the photosensitizer is removed. The portion of the plating layer uncovered by the photosensitizer is subjected to etching by an etching solution so as to form recesses. In this manner, the cells can be formed.

(31) Alternatively, as a method for forming cells by a mechanical method, for example, the plating layer (surface layer) of the gravure printing roll body 1 is subjected to mirror polishing. Thereafter, the surface of the plating layer is subjected to engraving with a diamond needle called a stylus so as to form recesses. In this manner, the cells can be formed.

(32) A procedure to perform dot printing on a print subject with the above-described gravure printing roll A will be described next. First, a gravure printer employed in a gravure printing method will be described. In FIG. 8, the letter A denotes the gravure printing roll, and an application liquid pan 4 for storing the ink C is disposed below the gravure printing roll A. Note that a doctor blade 5 for removing excess ink adhering to the outer peripheral surface of the gravure printing roll A is disposed on the lateral side of the gravure printing roll A.

(33) Furthermore, the back-up roll 3 is disposed above the gravure printing roll A. The gravure printing roll A and the back-up roll 3 are configured to sandwich and press the print subject B by their surfaces facing each other.

(34) The print subject B is not limited to a particular print subject. Examples of the print subject B include a laminated sheet including a metal foil (for example, an aluminum foil or the like) and a synthetic resin film integrally laminated on the metal foil, and a laminated sheet including a metal foil (for example, an aluminum foil or the like) and a print layer formed on a surface of the metal foil.

(35) Furthermore, the ink C is fed into the application liquid pan 4. A lower part of the gravure printing roll A is immersed in the ink C in the application liquid pan 4. Along with the clockwise rotation of the gravure printing roll A in FIG. 8, the ink C excessively fed to the cells 2 of the gravure printing roll A is removed by the doctor blade 5.

(36) Thereafter, the elongated print subject B is continuously fed between the facing surfaces of the gravure printing roll A and the back-up roll 3. By pressing the print subject B from the both sides thereof by the gravure printing roll A and the back-up roll 3, the ink C held in each of the cells 2 is transferred onto the print subject B. The ink C is then dried. In this manner, dot printing can be performed on the print subject B.

(37) The ink transferred onto the print subject B is fixed independently from one another without being merged and integrated with one another on the print subject B. Thus, dots each having an area close to the opening area of the cell in the gravure printing roll A are printed on the print subject B.

(38) The ink fed into the cells 2 of the gravure printing roll A is reliably transferred onto the print subject B. Thus, a dot pattern with no unprinted portions is beautifully printed on the print subject B.

(39) Since the dots printed on the print subject each have a very small diameter of 100 m or smaller, such dots can be hardly identified by human eyes. Note that the diameter of a dot refers to the diameter of a perfect circle with the minimum diameter capable of surrounding the dot.

(40) Therefore, the above-described gravure printing roll A enables dot printing on a print subject without changing the appearance thereof. For example, the gravure printing roll A can be used to print dots on a surface of a drug packaging body (for example, a PTP (press through pack) packaging body, a pouched packaging body, an SP (strip package) packaging body) without changing the appearance thereof. In the case of the PTP packaging body, for example, dots can be printed on the entire outer surface of a sealing film without changing the appearance of the sealing film. A drug code is configured by a plurality of dots, and arrangement patterns of dots are varied to correspond to respective drugs. With a dot arrangement pattern corresponding to a drug stored in a drug packaging body, a plurality of dots are printed on the outer surface of the drug packaging body with the gravure printing roll A. In this manner, a drug code corresponding to a drug stored in a drug packaging body can be printed on the outer surface of the packaging body without changing the appearance of the packaging body. By reading the drug code with a known reader, the drug stored in the packaging body can be checked.

EXAMPLES

(41) While the present invention will be described more specifically by way of examples, the present invention is not limited thereto.

Examples 1 to 11, Comparative Examples 1 and 2

(42) Gravure printing rolls A each including a huge number of cells 2, each of which had an opening of a rectangular or square shape, formed in a peripheral surface 11 (surface part 12) of a gravure printing roll body 1 were prepared. The corners of the opening of the cell were all formed in an arc shape. The cell 2 included: a bottom surface 2a formed in a concave arc shape in cross section; and a peripheral wall part 2b gradually extending outward from a peripheral edge of the bottom surface 2a toward the peripheral surface of the gravure printing roll body 1. The bottom surface 2a smoothly connected with the peripheral wall part 2b by intermediary of a concave arc part 2c. The bottom surface 2a had a plane rectangle or square shape. When the opening of the cell 2 and the bottom surface 2a each had a rectangular shape, the long side of the rectangle was positioned along the circumferential direction X of the gravure printing roll body 1. When the opening of the cell 2 and the bottom surface 2a each had a square shape, two sides opposed to each other among the sides of the square were positioned along the circumferential direction X of the gravure printing roll body 1. Dimensions of the openings of the cells in the circumferential direction X and in the axial center direction Y of the gravure printing roll bodies as well as depths thereof were as shown in Table 1. Opening areas of the cells were as shown in Table 1. Intervals between adjacent cells were as shown in Table 1. Formation densities of the cells were as shown in Table 1.

(43) Gravure printing was performed with the gravure printer shown in FIG. 8. A laminated sheet in which a white ink (manufactured by Fuji Ink Corporation, under the trade name of MBA White) was applied all over a surface of an aluminum foil with a thickness of 17 m was used as a print subject B.

(44) Ink (manufactured by Fuji Ink Corporation, under the trade name of MBA Black Ink) C was fed into the application liquid pan 4. Along with the clockwise rotation of the gravure printing roll A in FIG. 8, the ink C excessively fed to the cells 2 of the gravure printing roll A was removed by the doctor blade 5.

(45) Thereafter, the elongated laminated sheet B was continuously fed between the facing surfaces of the gravure printing roll A and the back-up roll 3. By pressing the laminated sheet B from the both sides thereof by the gravure printing roll A and the back-up roll 3, the ink C held in the cells 2 was transferred onto the laminated sheet B. The ink C was then dried. In this manner, dot printing was performed on the laminated sheet B. The laminated sheet B was fed between the facing surfaces of the gravure printing roll A and the back-up roll 3 so that the surface of the laminated sheet B applied with the white ink was positioned closer to the gravure printing roll A.

Example 12

(46) A gravure printing roll A including a huge number of cells, each of which had an opening of an isosceles triangular shape elongated in the circumferential direction of a gravure printing roll body, formed in a peripheral surface 11 (surface part 12) of the gravure printing roll body 1 was prepared. The cell 2 included: a bottom surface 2a formed in a concave arc shape in cross section; and a peripheral wall part 2b gradually extending outward from a peripheral edge of the bottom surface 2a toward the peripheral surface of the gravure printing roll body 1. The bottom surface 2a smoothly connected with the peripheral wall part 2b by intermediary of a concave arc part 2c. The bottom surface 2a had an isosceles triangular shape. The base of the isosceles triangle was positioned along the axial center direction Y of the gravure printing roll body 1. The dimensions of the opening of the cell in the circumferential direction and the axial center direction of the gravure printing roll body as well as the depth thereof were as shown in Table 1. The opening area of the cell was as shown in Table 1. The interval between adjacent cells was as shown in Table 1. The formation density of the cells was as shown in Table 1.

(47) Dot printing was performed on a print subject in the same manner as that in Example 1 except that the above-described gravure printing roll A was employed. The cells were configured such that the vertex of the isosceles triangle, which was the shape of the opening of the cell, was positioned on the leading side in the rotational direction of the gravure printing roll A.

(48) In each of Examples, the ink transferred onto the laminated sheet B was fixed independently from one another without being merged and integrated with one another on the laminated sheet B. Dots corresponding to the cells were formed independently from one another on the laminated sheet B.

(49) Fixing rates and dot shapes of the resultant dot print on the laminated sheets were measured in the following manner and their results were shown in Table 1.

(50) (Fixing Rate)

(51) A photomicrograph of the dot print on the laminated sheet was taken at a 200-fold magnification. Ten measuring zones each in the shape of a square with a side of 2 mm were determined in arbitrary portions on the photomicrograph. The number of dots present in each measuring zone was counted. In each measuring zone, the fixing rate was calculated in accordance with the following formula. The arithmetic mean value of the fixing rates in the measuring zones was calculated. Such an arithmetic mean value was employed as a fixing rate. Note that dots partially present in the measuring zones were excluded. In Comparative Example 2, the ink broke off during the separation of the ink from the cell. Thus, accurate dot printing was unable to be performed. Since the number of printed dots was greater than the number of the cells in the gravure printing roll, the fixing rate was over 100%.
Fixing rate (%)=100(the number of dots within a measuring zone)/(the number of cells formed in a gravure printing roll per 4 mm.sup.2)
(Dot Shape)

(52) A photomicrograph of the dot print on the laminated sheet was taken at a 200-fold magnification. A measuring zone in the shape of a square with a side of 1 cm was determined in an arbitrary portion on the photomicrograph. Dimensions of each dot in the measuring zone in the circumferential direction and the axial center direction of the gravure printing roll body were measured. The arithmetic mean value of the dimensions of the dots in the circumferential direction and the arithmetic mean value of the dimensions of the dots in the axial center direction were calculated. Such arithmetic mean values were shown in Table 1. Note that dots partially present in the measuring zone were excluded.

(53) TABLE-US-00001 TABLE 1 CELL DIMENSION IN DIMENSION IN BOTTOM CIRCUMFERENTIAL AXIAL CENTER OPENING SURFACE DIRECTION DIRECTION DIMENSION DEPTH SHAPE SHAPE (m) (m) RATIO (m) EXAMPLE 1 RECTANGLE RECTANGLE 73 53 1.38 10 EXAMPLE 2 RECTANGLE RECTANGLE 54 33 1.64 10 EXAMPLE 3 RECTANGLE RECTANGLE 66 18 3.67 10 EXAMPLE 4 RECTANGLE RECTANGLE 64 41 1.56 10 EXAMPLE 5 RECTANGLE RECTANGLE 56 17 3.29 10 EXAMPLE 6 RECTANGLE RECTANGLE 83 27 3.07 10 EXAMPLE 7 RECTANGLE RECTANGLE 79 15 5.27 10 EXAMPLE 8 RECTANGLE RECTANGLE 67 19 3.53 10 EXAMPLE 9 RECTANGLE RECTANGLE 56 14 4.00 10 EXAMPLE 10 RECTANGLE RECTANGLE 47 20 2.35 10 EXAMPLE 11 RECTANGLE RECTANGLE 45 15 3.00 10 EXAMPLE 12 ISOSCELES ISOSCELES 44 38 1.16 10 TRIANGLE TRIANGLE COMPARATIVE RECTANGLE RECTANGLE 41 42 0.98 14 EXAMPLE 1 COMPARATIVE RECTANGLE RECTANGLE 106 15 7.07 10 EXAMPLE 2 CELL DOT FORMATION CIRCUM- AXIAL OPENING DENSITY (THE FIXING FERENTIAL CENTER AREA INTERVAL NUMBER OF RATE DIRECTION DIRECTION (m.sup.2) (m) CELLS/mm.sup.2) (%) (m) (m) EXAMPLE 1 3869 200-500 10 100 80 52 EXAMPLE 2 1782 200-500 10 95.6 43 32 EXAMPLE 3 1188 200-500 10 79.6 64 44 EXAMPLE 4 2624 200-500 10 75.0 61 42 EXAMPLE 5 952 200-500 10 71.6 61 46 EXAMPLE 6 2241 200-500 10 100 86 59 EXAMPLE 7 1185 200-500 10 98.7 76 40 EXAMPLE 8 1273 200-500 10 93.3 64 44 EXAMPLE 9 784 200-500 10 100 44 38 EXAMPLE 10 940 200-500 10 96.0 56 45 EXAMPLE 11 675 200-500 10 89.3 40 40 EXAMPLE 12 836 200-500 10 65.0 58 50 COMPARATIVE 1722 200-500 10 50.0 61 61 EXAMPLE 1 COMPARATIVE 1590 200-500 10 180 70 40 EXAMPLE 2

CROSS REFERENCE TO RELATED APPLICATIONS

(54) This application claims the benefit of Japanese Patent Application No. 2015-22715, filed on Feb. 6, 2015, the disclosure of which is hereby incorporated in its entirety by reference.

INDUSTRIAL APPLICABILITY

(55) The gravure printing roll of the present invention can print dots hardly identifiable by human eyes without producing unprinted portions. Thus, a dot pattern can be sharply printed on a print subject without changing the appearance thereof. Therefore, the gravure printing roll of the present invention can be preferably used to print a dot pattern on a surface of a print subject, such as a drug packaging body, for which a change in its appearance is unfavorable.

REFERENCE SIGNS LIST

(56) 1 gravure printing roll body 11 peripheral surface 12 surface part 2 cell 2a bottom surface 2b peripheral wall part A gravure printing roll B print subject, laminated sheet C ink X circumferential direction Y axial center direction