JP2014069359A - Doctor blade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of fogging phenomena due to poor scraping with a doctor blade in gravure printing.SOLUTION: In a part, on the side of the base 3a of a doctor blade 3, separated by a specified distance L2 from the blade tip part 3b protruding from the base 3a of a doctor blade 3 on the side of a holder holding the blade, a strip groove 6 which extends in parallel in the longitudinal direction of the doctor blade 3, or in the longitudinal direction of the rotation shaft of a plate cylinder, reduces changing of the wedge angle, stabilizes scraping of an ink and eliminates residue of the ink.

Description

  The present invention relates to a doctor blade provided in a gravure printing machine.

  The role of the doctor blade in the gravure printing machine is to scrape off excess ink supplied to the plate surface of the plate cylinder, fill only the ink necessary for printing into the cell on the plate surface, and transfer only the ink in the cell to the web (printing) ). If the ink is not sufficiently scraped off by the doctor blade and printing is performed with excess ink remaining on the plate surface, a phenomenon called “fogging” in which unnecessary ink is transferred to the printed matter. When designing a doctor, in order to prevent this fogging, it is necessary to consider followability to the shape of the plate surface, rigidity and durability with respect to the plate surface and ink, and the like.

Conventionally, the shape of a doctor blade is designed by the following two methods as a fog prevention measure.
(1) In order to improve followability to the shape of the plate surface, the cutting edge portion of the doctor blade is processed thinly. This is broadly divided into a stepped doctor blade 8 shown in FIG. 5A, a tapered doctor blade 9 shown in FIG. 5B, a beveled doctor blade 10 shown in FIG. There are a combination type doctor blade 11 of a stepped type and a bevel type shown in (D), and a combination type doctor blade 12 of a tapered type and a bevel type shown in FIG.
(2) To increase the rigidity and durability of the doctor blade, the cutting edge and base are processed thick. This includes a straight doctor blade 13 shown in FIG.

  Further, as a countermeasure for preventing fogging due to wear of a doctor blade, it has been proposed to form a nitrided modified layer in the surface layer of the blade edge of the doctor blade (see, for example, Patent Document 1).

JP-A-10-337840

  The accuracy of the plate surface of the plate cylinder, that is, the cylindricity or the roundness is not perfect, and when exaggerated, the plate surface 1a is uneven as shown in FIG. 4B.

  According to the doctor blades 8 to 12 shown in FIGS. 5A to 5E, the blade edge portion is thin, so that it is easily bent. As shown in FIG. 4B, the wedge angle α of the doctor blade with respect to the plate surface 1a is wedged. It is easy to change greatly to the angle β. Therefore, it becomes easy to scrape ink. In FIG. 4 (B), the symbol B indicates scraped ink, which causes fogging. Further, since the doctor blade 8 has a small contact area between the blade edge portion 8b and the plate surface 1a from the base portion 8a, the blade edge portion 8b of the doctor blade 8 is quickly worn and lacks durability.

  The doctor blade 13 in the above figure (F) is easy to stabilize the wedge angle and has durability. However, if the followability to the shape of the plate surface 1a is poor and the accuracy (cylindricity and roundness) of the plate surface 1a is not good, fogging occurs due to ink scraping.

  Further, the method of forming the nitriding modified layer in the surface layer of the blade edge portion of the doctor blade can reduce the abrasion of the blade edge portion and prevent fogging, but the accuracy of the plate surface such as roundness is improved. It is difficult to prevent the occurrence of fogging due to low.

  Therefore, an object of the present invention is to provide a doctor blade of a gravure printing machine that can solve the above-mentioned problems.

  In order to solve the above problems, the present invention employs the following configuration.

  In addition, although the code | symbol with a parenthesis is attached | subjected in order to make an understanding of this invention easy, this invention is not limited to this.

  That is, the invention according to claim 1 is a blade edge portion (3b) protruding from the base portion (3a) on the holder (4) side of the doctor blade (3), and the base portion (3b) is protruded from the tip of the blade edge portion (3b). A doctor blade in which a groove (6) extending in parallel with the length direction of the doctor blade (3) is formed at a predetermined distance on the 3a) side is employed.

  As described in claim 2, in the doctor blade according to claim 1, a portion of the blade tip portion (3b) on the tip side of the groove (6) is on the opposite side of the groove (6). It may be formed thinner than the portion.

  As described in claim 3, in the doctor blade according to claim 1 or 2, the groove (6) is a portion on the tip side of the groove (6) in the blade edge part (3b). And can be formed to have substantially the same width.

As described in claim 4, in the doctor blade according to any one of claims 1 to 3, the groove (6) corresponds to the plate surface (1a) of the plate cylinder (1) of the gravure printing machine. It can be formed on the wedge angle (α) side of the blade edge portion (3b).

  According to the present invention, the portion on the tip side of the cutting edge portion (3b) from the groove (6) is thicker than the cutting edge portion (8b) of the conventional stepped mold, so that the followability to the plate surface (1a) is conventional. Therefore, the rigidity and durability of the doctor blade (3) are superior to the conventional stepped doctor blade (8). Further, since the contact area between the tip of the blade edge portion (3b) and the plate surface (1a) is increased, the amount of wear of the blade edge portion (3b) is reduced and the durability is improved. Furthermore, since the portion of the doctor blade (3) is located farther from the tip of the blade edge part (3b) than the conventional type, the tip of the blade edge part (3b) is reduced in the processing accuracy of the plate surface (1a), etc. Even if it rides on the convex part (14) generated by the above, the change in the wedge angle is small, the ink scraping is stable, and the ink remaining in the part other than the image line part causing the fogging is eliminated. Therefore, according to the present invention, the occurrence of fog is appropriately prevented, and the quality of gravure printing is improved.

It is a front view which shows the use condition of the doctor blade which concerns on this invention. It is a vertical sectional view of a doctor blade according to the present invention. It is a vertical sectional view of a modification of the doctor blade according to the present invention. (A) is a vertical sectional view for explaining the action of the doctor blade according to the present invention, and (B) is a vertical sectional view for explaining the action of the conventional doctor blade. (A)-(E) are vertical sectional views showing various conventional doctor blades. It is a schematic cross section of the gravure printed matter in which fog is generated.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  In FIG. 1, the code | symbol 1 shows the cylinder type | mold cylinder of a gravure printing machine, and the code | symbol 2 shows a doctor apparatus.

  The doctor device 2 includes a doctor blade 3 and a holder 4 for holding the doctor blade 3 in a fixed position. The doctor blade 3 and the holder 4 extend in a strip shape parallel to the rotation axis of the plate cylinder 1 of the gravure printing machine. Although not shown, the lower part of the plate cylinder 1 is immersed in ink stored in an ink pan.

  As shown in FIG. 2, the doctor blade 3 has a tip portion of a base portion 3a as a blade tip portion 3b, and as shown in FIG. 1, the base portion 3a is held by a holder 4 and the tip of the blade tip portion 3b is at a plate cylinder. 1 is pressed against a cylindrical plate surface 1a. A patch plate 5 is provided between the doctor blade 3 and the holder 4 as necessary.

  As shown in FIG. 1, when the plate cylinder 1 rotates in the direction of the arrow during gravure printing, the ink A adheres to the plate surface 1a and moves upward together with the plate surface 1a. A part of the ink A rising together with the plate surface 1a is filled in a large number of cells constituting a print image (not shown) of the plate surface 1a, and the remaining ink is scraped off from the plate surface 1a by the blade edge portion 3b of the doctor blade 3. It is done.

  As described above, the doctor blade 3 includes the blade edge portion 3b that protrudes from the base portion 3a on the holder 4 side. As shown in FIG. 2, the blade edge portion 3b has a predetermined distance from the tip to the base portion 3a side. A groove 6 extending in parallel with the length direction of the doctor blade 3, that is, the length direction of the rotation axis of the plate cylinder 1, is formed at the spot.

  Since the doctor blade 3 is made of a strip-shaped metal having a uniform thickness, the thickness T is equal on the tip side of the blade edge portion 3 b across the groove 6 and on the opposite side of the groove 6. The depth of the groove 6 is desirably about T / 2.

  When the width of the groove 6 is L1, and the distance from the groove 6 to the tip of the blade edge portion 3b is L2, it is preferably L1≈L2. However, as required, L1> L2 or L1 <L2.

  Further, a curved surface 7 is formed at the tip of the cutting edge portion 3b of the doctor blade 3 as necessary for reducing wear, and a portion where the groove 6 is in contact with the outer surface of the doctor blade 3 is also necessary for improving the strength. Thus, the curved surface 6a is formed.

  As shown in FIG. 4, the doctor blade 3 is preferably arranged so that the groove 6 comes to the wedge angle α side when the tip of the blade edge portion 3b is brought into contact with the plate surface 1a. Of course, it is also possible to arrange the groove 6 so as to be on the side opposite to the wedge angle α side.

  As shown in FIG. 4 (A), the doctor blade 3 according to the present invention has a followability with respect to the plate surface 1a since the portion on the tip side of the groove 6 is as thick as the portion on the opposite side of the groove 6. The same is maintained as in the case of the conventional stepped doctor blade 8 (FIG. 5A), and the rigidity and durability of the doctor blade 3 are superior to those of the conventional stepped doctor blade 8. Further, since the contact area between the tip of the blade edge portion 3b and the plate surface 1a is increased, the wear amount of the blade edge portion 3b is reduced and the durability is improved.

  Further, as apparent from the comparison between (A) and (B) in FIG. 4, the cutting edge portion of the doctor blade 3 is located farther from the tip of the blade edge portion 3 b than the conventional type. When the tip of 3b rides on the convex portion 14 generated due to a decrease in processing accuracy of the plate surface 1a, the wedge angle changes from α to β in the case of the present invention, whereas the conventional stepped doctor blade If it is 8, the wedge angle changes greatly from α to γ (β> γ). As a result, according to the doctor blade 3 of the present invention, the change in the wedge angle is reduced, the ink scraping is stabilized, and the area other than the image area that causes the fogging shown in FIG. Residue of ink B is eliminated.

  The doctor blade 3 may have the shape shown in FIG. 3 instead of the shape shown in FIG. The doctor blade 3 shown in FIG. 3 is formed such that the tip side portion of the cutting edge portion 3 b of the blade edge portion 3 b is thinner than the portion on the opposite side across the groove 6. That is, t <T. Desirably, t≈T / 2.

  Moreover, although not shown in figure, you may make it provide what made the said groove 6 shallower on both surfaces side of the blade edge | tip part 3b.

  The prototype blades 1 and 2 shown in Table 1 are prepared using the doctor blade having the cross-sectional shape shown in FIG. 2 as a base material of a strip-shaped iron plate, and the surface of the blade edge portion is subjected to cera plating (plating using nickel and ceramic) )

The test conditions are as follows.
Printing speed: 200m / min
Doctor pressure: 5N / cm
Doctor angle: 45 °
Plate engraving conditions: Cell shape is engraved 70 lines / cm2 and engraving needle is stylus 130 °
Ink: Ink for film back printing Solvent: Ethyl acetate: Propyl acetate: IPA = 5: 3: 2
Original fabric: 20μm thick transparent stretched polypropylene film Ink viscosity: 14-15sec (Zahn cup # 3)

The evaluation method is as follows.
The fog rate was determined by the following calculation formula and evaluated (n = 5).

Fog rate = (CP) ÷ (BP)
6, reference numeral 15 denotes a transparent original fabric, reference numeral 16 denotes a white ink layer, reference numeral 17 denotes a solid printing layer made of ink other than white ink, and reference numeral 18 denotes an ink adhesion portion caused by fog. Respectively. In the calculation formula, P, B, and C are reflection density values shown below.
P: Base color DEN value (printing only for white ink for concealment)
B: Print color DEN value (print color solid + concealed white ink printing part)
C: fog generation part DEN value (fog generation part + concealed white ink printing part)
Gretag Macbeth Spectroeye (Reflection ANSI T) was used as a reflection density measuring device.

  Table 2 shows the test results.

  As is apparent from Table 2, when the viscosity of the ink is increased, the fog rate is doubled for the conventional doctor blade, but no change can be recognized by the doctor blade according to the present invention, and It was found that there was almost no change in the fog rate, that is, almost no fog was generated.

  The result of the prototype 2 was almost the same as that of the prototype 1.

DESCRIPTION OF SYMBOLS 1 ... Plate cylinder 1a ... Plate surface 3 ... Doctor blade 3a ... Base part 3b ... Cutting edge part 4 ... Holder 6 ... Groove α ... Wedge angle

Claims (4)

  A blade edge projecting from the base part on the holder side of the doctor blade, and a groove extending in parallel to the length direction of the doctor blade is formed at a position at a predetermined distance from the tip of the blade edge part to the base side. Doctor blade characterized by that.   2. The doctor blade according to claim 1, wherein a portion of the blade tip portion on the tip end side with respect to the groove is formed thinner than a portion on the opposite side across the groove. 3.   3. The doctor blade according to claim 1, wherein the groove is formed to have substantially the same width as a portion of the blade edge portion on the tip side with respect to the groove. 4.   The doctor blade according to any one of claims 1 to 3, wherein the groove is formed on a wedge angle side of the blade edge portion with respect to a plate surface of a plate cylinder of a gravure printing machine.

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