JPH0468147B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a coating device used in an inking device of a printing press, etc., and particularly to prevent the growth and fall of coating liquid deposits from the back side of a doctor blade (hereinafter abbreviated as back dripping). This invention relates to an improved coating device. (Prior art and its problems) An inking device in which a doctor blade is directly pressed against an inking roller having an elastic surface such as rubber to form a thin ink film is disclosed in, for example, Japanese Patent Laid-Open No. 178872/1983. ink equipment,
An inking device disclosed in Utility Model Application Publication No. 56-76438 is known. The inking device of the former (Japanese Patent Application Laid-open No. 57-178872) is
As shown in FIG. 14, the ink applicator roller 1 is composed of a single layer of rubber roller, and the doctor blade 2 is held approximately in the tangential direction of the ink applicator roller 1, and an ink scraping portion 2a is provided at the tip of the doctor blade 2. It is provided. In this ink scraping portion 2a, the leading edge 2 on the ink introduction side
b and the leading edge 2c on the ink outlet side are each polished to have a sharp edge so as to be curved with an extremely small radius of curvature. In this inking device, while pressing the ink scraping portion 2a of the doctor blade 2 against the inking roller 1,
The ink forming roller 1 is rotated in the direction of the arrow in the figure to form the ink film 3a.
When a high viscosity ink is used, the ink scraping portion 2a is damaged due to the deflection of the doctor blade 2.
As a result of the bending of the roller 1 and the deformation pattern of the roller 1, ink pools occur on the lower surface side of the ink scraping portion 2a.
This ink pool continues to grow as the operating time passes, and eventually falls, causing problems such as stains on printed matter and uneven print density. On the other hand, in the inking device of the latter (Utility Model Application Publication No. 56-76438), as shown in FIG. The ink outlet side surface 5a at the tip end thereof is finished with an inclined surface. In this inking device as well, when a high viscosity ink is used as the ink 3, the ink outlet side surface 5a at the tip of the doctor blade 5 is finished with an incline, and the influence of the deformation pattern of the roller 4 is further reduced. As a result, ink pools occur on the inclined surface 5a, and the same problem as in the above-mentioned inking device occurs in that ink stagnation occurs when the ink is operated for a long time. Although the above explanation has been about the sagging of the inking device in a printing press, the same problem also occurs in coating devices other than the inking device. (Object of the Invention) The present invention was made in order to solve the above-mentioned problems of the conventional example, and its purpose is to provide a coating device that can prevent the coating liquid from dripping from the doctor blade even when operated for a long time. shall be. (Means for achieving the object) The present invention includes an application roller having an elastic surface;
A coating device is provided with a doctor blade which is arranged to be movable forward and backward in the approximate radial direction of the coating roller with respect to the outer circumferential surface of the coating roller and adjusts the thickness of the coating film formed on the outer circumferential surface of the roller. In order to achieve this, the doctor blade includes a thin plate member whose tip end is pressed against the outer circumferential surface of the coating roller, and this thin plate member is in a state where the thin plate member is substantially inflexible in the tangential direction of the outer circumferential surface of the coating roller. The ink outlet side front edge at the tip of the thin plate member is curved, and the radius of curvature is set to 20 μm or less. (Embodiment) A. Configuration of inking device FIG. 2 shows a schematic diagram of a printing press equipped with an inking device which is an embodiment of the present invention. This printing press includes a bracket cylinder 6, a plate cylinder 7, and an impression cylinder 8, and an inking device 9 is detachably attached to the plate cylinder 7. The printing operation is carried out by wrapping the plate 10 around the plate cylinder 7, passing the continuous paper 11 between the bracket cylinder 6 and the impression cylinder 8, and then rotating each cylinder 6, 7, 8 in the direction of the arrow in the figure. While feeding the paper 11 in the direction of the arrow in the figure, ink is applied to the plate 10 from the inking device 9.
The ink supplied to the printing plate 10 is further transferred onto the continuous paper 11 via the bracket cylinder 6 to perform printing. FIG. 3 shows a schematic sectional view of the inking device 9, and FIG. 4 shows a plan view of the same device. As shown in both figures, an ink applicator roller 12 and an auxiliary ink applicator roller 13 are rotatably attached to left and right frames 14, 14. In addition, kneading rollers 15,1
6 is attached to the left and right frames 14, 14 so as to be rotatable and swingable in the axial direction of the roller. These kneading rollers 15 and 16 are configured such that their end surfaces are located outside of the end surface of the inking roller 12 at their swinging end positions. An ink amount adjusting member 17 is disposed at a rear position of the ink forming roller 12. The ink amount adjusting member 17 includes a doctor blade 18, left and right side plates 19 attached to both ends of the doctor blade 18,
19, and left and right fulcrum pins 20, 20 attached to the upper positions of these left and right side plates 19, 19. By fitting into the receivers 21, 21, the fulcrum pin 2
It is held so as to be swingable in the front-rear direction in FIG. 3 with 0 as a fulcrum. In this case, the front end surfaces 19a of the left and right side plates 19, 19 are formed in a generally arcuate shape so as to substantially follow the outer circumferential surface of the ink form roller 12, and the front end surfaces 19a are formed on the outer circumference of the ink form roller 12 at the ends of the ink form roller 12. placed in a position facing the surface.
As a result, an ink reservoir space 22 surrounded by the doctor blade 18, the left and right side plates 19, 19, and the ink form roller 12 is formed. A blade pressing member 23 is disposed at a rear position of the ink amount adjusting member 17. The blade pressing member 23 includes an eccentric shaft 24 and left and right rollers 25, 25 rotatably fitted to the eccentric shaft 24,
These left and right rollers 25, 25 are rotatably attached to the left and right frames 14, 14 so as to be in contact with the back surface of the doctor blade 18. and,
This blade pressing member 23 is driven to rotate in forward and reverse directions by a pulse motor (not shown), its rotation angle is controlled by an electronic circuit, and its rotation range is regulated by a sensor (not shown). . The blade pressing member 23 functions to adjust the amount of pushing of the doctor blade 18 onto the ink applicator roller 12 by its rotation, and as a result, adjust the thickness of the ink film formed on the outer peripheral surface of the ink applicator roller 12. Next, the details of the configurations of the ink forming roller 12 and the doctor blade 18, which are key points of the present invention, will be explained using FIG. 5 and FIG. 1. FIG. 5 shows a sectional view of a main part of the inking device 9 during formation of a thin ink film, and FIG. 1 shows an enlarged sectional view thereof. First, the ink forming roller 12 is composed of, for example, a rubber roller having an elastic surface. The layer structure of the elastic portion of this roller may be a single layer structure, or may be a multilayer structure in which the surface layer has a higher hardness than the inner layer. In this embodiment, a rigid rotating shaft 121 such as a metal round bar is used as a core material, an inner layer 122 is provided with a soft rubber layer, and an outer layer 123 is provided with a rubber layer harder than the inner layer 122.
It has a layered structure. Both ends of the rotating shaft 121 are supported by rolling bearings (not shown) on the left and right frames 14, 14, and a drive gear (not shown) fixed to one end of the rotating shaft 121.
is configured to mesh with a plate cylinder gear (not shown) to drive the gear. The surface of the ink forming roller 12 is highly finished in roundness and straightness to prevent rotational run-out, and preferred values are approximately 0.02 roundness and 0.03 straightness. The surface hardness of the ink form roller 12 is JISK-6301.
It is desirable to set the rubber hardness specified by 15° to 70°. If the hardness is less than 15°, it will be impossible to form a thin ink film (3 to 15 μm) suitable for printing, while if the hardness exceeds 70°, not only will it be impossible to obtain a stable ink film, but the plate surface will not be able to form properly. This is because accurate ink transfer becomes impossible. A more preferred value of this hardness is 25° to 50°. Next, the doctor blade 18 rotates the thin plate member 181
The thin film member 181 is composed of a rigid upper holding member 182 and a rigid lower holding member 183 that sandwich and hold the thin film member 181 from above and below, leaving the tip of the thin film member 181. It is arranged so as to face the outer peripheral surface. The thin plate member 181 has a thickness of, for example, 0.1 to 0.8 mm.
Constructed from Swedish steel and other materials. Further, the protruding amount l of the tip of the thin plate member 181 from the upper holding member 182 and the protruding amount a from the lower holding member 183 are determined when the doctor blade 18 is moved to the ink forming roller when forming the ink thin film, as shown in FIG. Even if the tip of the thin plate member 181 is subjected to a force that bends and deforms in the tangential direction of the outer peripheral surface of the roller as the roller 12 rotates when the ink form roller 12 is rotated in the direction of the arrow while being pressed against the roller 12. , the dimensions are set so that substantially no flexural deformation occurs. As an example of preferable dimensional values for the amount of protrusion, l is 1.9 mm and a is 0.5 mm. At the tip of the thin plate member 181, the upper surface 18
The ink introduction side front edge 181c located at the intersection between 1a and the front end surface 181b is finished with a curved surface having a radius of curvature of dimension R, and the lower surface 1
The angle between 81d and front end surface 181b is substantially 90
The leading edge 181e on the ink outlet side, which is formed at the same time and located at the portion where these two surfaces intersect, is similarly finished with a curved surface having a radius of curvature of dimension r. In order to obtain an ink film thickness greater than the required thickness, it is necessary to set the radius of curvature R of the ink introduction side leading edge 181c to 30 μm or more. This radius of curvature R is determined by the elasticity of the ink forming roller 12, the relative speed of the ink forming roller 12 with respect to the doctor blade 18, and the ink forming roller 12.
It varies depending on the viscosity of 6, etc., and the above 30μ
An appropriate value may be selected within the range of m or more. As an example, when the rubber hardness of the surface of the ink forming roller 12 is 30 degrees, the relative speed to the doctor blade 18 is about 36 m/min, and the viscosity of the ink 26 is about 900 poise, the preferable value of the radius of curvature R is 50 to 75 μm.
It is. On the other hand, in order to prevent ink from running down from the thin plate member 181, it is necessary to set the radius of curvature r of the ink outlet side leading edge 181e to 20 μm or less. Note that it is preferable to set the radius of curvature r to 10 μm or less because this increases the peeling force that overcomes the interfacial tension of the ink that tries to adhere to the leading edge 181e on the ink outlet side. If this setting is made, the peeling force becomes more stable than in the case described above, so that it is possible to prevent ink pooling from occurring even when using more types of ink. Hereinafter, the principle of sag will be explained using Examples and Comparative Examples of the present application, and the experimental results of each will be described. B Principle of underside droop and experimental results (1) Comparative example 1 (a) Principle First, as shown in Fig. 6, the thin plate member 18
1, the ink outlet side surface 18
A case will be considered in which the ink film 26a is formed using a doctor blade in which 1f is finished at an angle and the clearance angle θ is set to be smaller than 90 degrees (for example, 45 degrees). In this case, it is assumed that the ink forming roller 12 having a two-layer structure shown in FIG. 5 is used. The velocity distribution of the ink 26 at a position P ₁ near the leading edge 181g of the ink outlet side of the doctor blade thin plate member 181 is approximately equal to the roller surface velocity v ₀ at the boundary of the ink form roller 12, as shown in FIG. 6b. , the speed approaches zero as it approaches the thin plate member 181 side. On the other hand, the velocity distribution of the ink 26 at the position _P2 immediately after the formation of the ink film 26a is equal to the roller surface velocity _v0 . Therefore, the ink flowing along the boundary surface of the thin plate member 181 is accelerated while changing direction from velocity zero to v ₀ near the ink outlet side leading edge 181g. As a result, due to the viscoelastic properties of the ink 26, a force F is generated that tends to peel the ink 26 from the surface of the thin plate member 181. If this force F is larger than the interfacial tension between the ink 26 and the surface of the thin plate member 181, the ink 26 will peel off at the interface of the thin plate member 181. However, as shown in FIG.
When the clearance angle θ at the tip of 81 is set small, the leading edge 18 on the ink outlet side
Since the ink velocity changes slowly in the vicinity of 1 g, the position where the force F becomes large enough to cause ink peeling shifts to the lower right of the figure. However, since the ink 26 contains bubbles and the like and is not completely uniform, the ink may break in the ink before reaching this peeling point. In this way, the ink 26 remaining near the front edge 181g of the thin plate member 181 on the ink outlet side is
Since the ink has a velocity component V along the tapered surface 181f of the thin plate member 181, it is gradually pushed out to form an ink pool S as shown in FIG. 6b. This ink puddle S grows as the operating time passes, and finally the weight of the ink puddle S and the frictional force exerted by the boundary between the moving ink film 26a and the ink puddle S are applied to the ink 26 and the thin plate member 181. is larger than the adhesive force of the ink 26 or the breaking stress of the ink 26,
It falls from the thin plate member 181. From the above, the surface 181 on the ink derivation side
The clearance angle θ formed by f and the tangent to the outer peripheral surface of the coating roller is preferably 80 to 100 degrees, and 85 to 95 degrees.
More preferably, the angle is substantially 90 degrees, most preferably substantially 90 degrees. Here, if the relief angle θ is outside the above range, the thin plate member 181
Since a thin plate member having a stable plate thickness d and a radius of curvature r in the width direction cannot be obtained, a stable ink thin film without uneven printing density cannot be obtained. (b) Comparative Experimental Example 1 As the ink form roller 12, a metal round rod with a diameter of 20 mm was used as the rigid core material 121 (Fig. 5), and then a rubber hardness material was used as the inner layer 122.
After providing a 20° soft cushion rubber layer and increasing its outer diameter to 50 mm, an outer layer 1 is placed on top of it.
23 is formed by wrapping a rubber layer with a rubber hardness of 30° to a thickness of 5 mm, with an outer diameter of 60 mm and a length of 418 mm.
A two-layer rubber roller of mm was used. The surface of this roller has a sufficiently smooth finish, the roundness is 0.02, and the runout relative to the reference axis is 0.02.
Finished with high precision. On the other hand, the doctor blade has a thin plate member 181 made of Swedish steel as shown in FIG.
The distance t to g is 0.15 mm, and the distance between the upper surface 181a and the lower surface 181d, that is, the plate thickness d, is 0.8 mm.
Set to . In addition, the amount l of the tip of the thin plate member 181 protruding from the upper holding member 182 is determined.
The protrusion amount a from the lower holding member 183 is set to 0.5 mm (non-flexible support), and the clearance angle θ is set to 45 degrees. Further, the radius of curvature R of the ink introduction side leading edge 181c of the thin plate member 181 is set to 50 μm, and the ink leading side leading edge 181
Let the radius of curvature r of g be 10 μm. A printing experiment was carried out using an offset printing machine (VS-1000, manufactured by Toray Engineering Co., Ltd.) shown in FIG. 2 using the inking device equipped with the above-mentioned inking roller and doctor blade. The ink 26 used was a standard ink for waterless planography (viscosity 500 to 3000 poise), and the color was indigo blue. The printing speed was 4500I.PH and the number of revolutions of the ink forming roller 12 at that time was 192R.
It was PM. When printing under the above conditions, continuous
Ink pool S occurred and fell after printing 2000 to 4000 sheets. (2) Comparative Example 2 (a) Principle As shown in FIG. 7, at the tip of the thin plate member 181, the leading edge on the ink introduction side and the leading edge on the ink leading side are respectively curved, and their curvature radii R and r to a value larger than 20μm, e.g.
Set it as large as 40μm. In this case as well, a two-layer roller is used as the ink forming roller 12, as in Comparison Row 1 above. If the radius of curvature r of the leading edge on the ink outlet side is finished to be larger than 20 μm as described above, the deformation of the ink form roller 12 during the formation of the ink film will occur along the surface of the thin plate member 181 as shown in FIG. Recovery follows a curve as shown in . The velocity distribution of the ink 26 flow at the tip _P1 of the thin plate member 181 is similar to the case of Comparative Example 1 above, where the roller boundary surface is v ₀ approximately equal to the roller circumferential speed, and as it approaches the thin plate member 181, The velocity _vo at the boundary surface approaches zero. On the other hand, immediately after passing the leading edge on the ink outlet side, P ₂ has finished forming the ink film 26a.
The velocity distribution at a point is the overall roller surface velocity v ₀
is equal to Therefore, in this case as well, the ink flowing along the boundary surface of the thin plate member 181 is accelerated near the _P1 point while changing direction from zero to _v0 , and the ink 26 is pulled from the surface of the thin plate member 181. A force F is generated to try to peel it off. However, the thin plate member 1
If the radius of curvature r of the leading edge of the ink outlet side of No. 81 is set large, the speed change near point _P1 will be gradual, and the position where the force F becomes large enough to cause ink peeling will be as described above. As in the case of Comparative Example 1, the flow moves toward the lower right of the figure. As a result, as in the case of Comparative Example 1 above,
The ink remaining on the thin plate member 181 is gradually pushed out by the velocity component V along the surface of the thin plate member 181, creating an ink puddle S, and the ink puddle S grows and falls during long-term operation. Become. (b) Comparative Example 2 The thin plate member 181 is made of Swedish steel, and the radii of curvature R and r of the leading edge on the ink introduction side and the leading edge on the ink outlet side are respectively 40μ.
m, clearance angle θ is set to 90°, and plate thickness d is
Set to 0.15mm. When the ink film 26a was formed with all other conditions set the same as in Comparative Example 1, an ink pool S was generated and dropped by the time the number of consecutive prints reached 2000 sheets. (3) Comparative Example 3 (a) Principle As shown in FIG. 8, the radius of curvature r of the leading edge 181e on the ink outlet side of the thin plate member 181 of the doctor blade is set to 20 μm or less, for example, 10 μm, and the tip of the thin plate member 181 The amount of protrusion l and a at the ink forming roller 1
A case will be considered in which the dimensions are set to such a size that the tip end of the thin plate member 181 can have flexibility in the tangential direction of the outer circumferential surface of the roller as the roller 2 rotates. In this case as well, a two-layer roller is used as the ink forming roller 12. Now, in FIGS. 8b and 8c, l: From the upper holding member 182 to the thin plate member 181
Distance from the lower holding member 183 to the tip of the thin plate member 181
Distance to the tip b: l-a E: Young's modulus of the thin plate member 181 I: Moment of inertia W of the thin plate member 181: When defined as the force applied to the tip of the thin plate member 181, the maximum force at the tip of the thin plate member 181 The deflection y is expressed by the following formula. y=a ² (4l-b)/12EI・W Here, as a specific example, if we compare the deflections of the following two examples, Example 1 When l=1.9 and a=0.5, y ₁ =0.13(W/ EI) Example 2 When l = 1.9, a = 1.5 y ₂ = 1.35 (W/EI) In other words, when the value of a is 1.5 mm, the amount of deflection y is 10.5 times (y ₂ /y ₁
= 10.5). This means that the support of the thin plate member 181 by the lower holding member 183 becomes a flexible support unless a portion closer to the tip of the thin plate member 181 is supported. Note that the calculated value of the deflection amount y in the case of Comparative Example 3 was approximately 15 μm. Therefore, in order to support the thin plate member 181 inflexibly, it is preferable that the amount of deflection y be less than 15 μm. In Comparative Example 3, we will consider a case where the tip of the thin plate member 181 is bent, as in the case of [Example 2] above. A model of the deformation of the ink forming roller 12 and the ink flow when such a deflection occurs is shown in FIG. 8a, and the roller surface and the thin plate member 181
An inverted wedge is formed between the tip surface 181b and the tip surface 181b. Under these conditions, just before the ink film is formed,
The ink velocity distribution at _one point P is greatest at v ₀ at the roller surface boundary position, and v _o becomes almost zero at the boundary surface at the tip of the thin plate member. At this time, the reverse wedge-shaped ink flow causes the position P ₁
The velocity distribution (from v ₀ to v _o ) changes gradually until reaching . As a result, the tensile force F in the ink is generated earlier than in the case where there is no deflection. This force F causes the ink 26 to
Although it is not strong enough to peel it off at once from the front end surface 181b of the ink, it may cause breakage at a weak portion in the ink. As a result of the irregular breaks that occur in the ink in this way, the ink left behind on the thin plate member 181 side gradually accumulates due to the velocity component V along the surface of the thin plate member 181 and the wetting of the lower surface 181d of the thin plate member. do. In this way, during long-term operation, the ink pool S grows and falls downward. In this way, when the thin plate member 181 is supported by a flexible support method, the front end surface 181b of the thin plate member 181 corresponds to the relief angle θ of Comparative Experiment Example 1 with respect to the tangent to the outer peripheral surface of the ink form roller 12. Since an inclined surface is formed, the same problem as in Comparative Experiment Example 1 occurs. A similar phenomenon also occurs when the thin plate member 181 is attached with the thin plate member 181 facing diagonally downward. (b) Comparative Experimental Example 3 In FIG. 8, the radius of curvature r of the leading edge 181e on the ink outlet side at the tip of the thin plate member 181 is set to 10 μm, the radius of curvature R of the leading edge 181c on the ink introducing side is set to 50 μm, and the thin plate The protruding amount l of the tip of member 181 is 1.9
mm and a were set to 1.5 mm. Other conditions are
All settings were made the same as in Comparative Experiment Example 1 above. When the ink film 26a was formed under these conditions, the tip of the thin plate member 181 was bent in the tangential direction of the outer peripheral surface of the roller, and an ink pool S was generated at the leading edge 181e on the ink outlet side. The ink puddle S grew and fell after 4000 to 5000 sheets were printed continuously. Note that when the printing machine is temporarily stopped before the ink puddle S falls and printing is restarted using new paper, most of the ink puddle S is carried away to the surface of the ink form roller 12, and as a result, the surface of the ink form roller 12 is removed. The uniformity of the ink film was impaired, resulting in uneven density on printed matter. (4) Example 1 (a) Principle As shown in FIG. 9, the radius of curvature r of the ink outlet side leading edge 181e of the thin plate member 181 of the doctor blade is set to 20 μm or less, for example, 10 μm or less, and the thin plate member 181 is Consider the case where the protrusion amounts l and a at the tip are set to such a size that the tip of the thin plate member does not substantially have flexibility in the tangential direction of the roller outer peripheral surface as the ink form roller 12 rotates. do. The specific numerical values of the protrusion amounts l and a are, for example, as in the above [Example 1], l=
Examples include 1.9 mm and a=0.5 mm. In this case as well, a two-layer roller is used as the ink forming roller 12. Under the above conditions, the velocity distribution at _point P immediately before the leading edge 181e on the ink outlet side is fastest at the roller boundary surface v ₀ and slowest at the boundary surface 181b of the thin plate member 181 and becomes almost zero (v _o ≒ 0). Further, the ink speed at point _P2 immediately after the ink film is formed is equal to the roller surface speed _v0 . Therefore, the ink flow with a velocity v _o ≒ 0 near P ₁ rapidly increases its velocity from a flow parallel to the roller surface and the front end surface 181b of the thin plate member toward the roller 12 side, that is, in the direction of F, and increases the roller surface velocity. v becomes ₀ . That is, the ink near the boundary surface of the thin plate member at point _P1 is accelerated while changing direction to the speed _v0 . As a result, due to the viscoelastic properties of the ink, a force F is generated that tends to peel off the ink from the surface of the thin plate member. If this force F is larger than the interfacial tension between the ink and the surface of the thin plate member, the ink will peel off at the blade interface. However, the thin plate member 181
However, when r≦20 μm and there is no downward deflection, the above-mentioned speed change near P ₁ occurs rapidly and instantaneously. Therefore the force F
Since the force F increases rapidly, the force F overcomes the interfacial tension on the surface of the thin plate member, and stable peeling occurs at the leading edge 181e on the ink outlet side. Therefore, irregular breaks in the ink hardly occur, and no ink is left behind on the thin plate member 181 side. In other words, almost no ink pools occur. In addition, as an ink application roller,
When an inking roller 12 having a two-layer structure in which the outer layer 123 is harder than the inner layer 122 is used, the swelling deformation of the rubber roller that reduces the relief angle of the thin plate member tip surface 181b with respect to the roller surface is reduced. Therefore, the above-mentioned peeling occurs more stably, and ink pooling becomes less likely to occur. (b-1) Embodiment 1 of the present application In FIG. 9, the radius of curvature γ of the leading edge 181e on the ink outlet side of the thin plate member 181 is set to 15μ.
m, and the amount of protrusion a at the tip of the thin plate member 181 was set to 0.5 mm.
The inks used were water or standard lithographic inks (viscosity 500 to 3000 poise), and the colors used were indigo, grass green, and brown. All other conditions were set to be the same as in Comparative Experiment Example 3 shown in FIG. When the ink film 26a was formed under these conditions, the thin plate member 181 exhibited substantial rigidity in the tangential direction of the outer peripheral surface of the roller, and the accumulation of ink on the lower surface of the thin plate member 181 was suppressed as much as possible. During printing, a rod-shaped ink with a diameter of about 1 to 2 mm is formed on the front edge 181 of the ink outlet side.
It was attached to e. After printing about 4,000 sheets, the indigo ink puddles did not grow much and there was no fear of it falling off. Furthermore, for grass-colored and brown inks, which are extremely prone to ink puddles, there were cases where ink puddles were observed to grow after 4,000 sheets.
It did not fall, and there was no problem in practical use. (b-2) Experimental example 2 of the present invention In FIG. 9, the radius of curvature γ of the ink outlet side leading edge 81e of the thin plate member 181 is set to
All other settings were the same as in Experimental Example 1 of the present invention. When the ink film 26a was formed under these conditions, a thin rod-shaped ink with a diameter of 1 mm or less adhered to the leading edge 181e on the ink outlet side after 2000 sheets were printed continuously for each color ink, but the indigo ink did not adhere to the leading edge 181e on the ink outlet side after 2000 sheets were printed continuously. However, there was almost no growth observed, and the number was 6000 to 8000 in a row.
There was no danger that even a single sheet would fall. As for the grass-colored and brown leaves, 6,000 to 8,000 pieces were grown in a row to a diameter of about 2 mm, but they did not fall to the point of falling and were not a problem for practical use. (b-3) Experimental example 3 of the present invention In FIG. 9, the radius of curvature γ of the leading edge 181e on the ink outlet side of the thin plate member 181 is
m, and all other settings were the same as in Experimental Example 1 of the present invention. When the ink film 26a was formed under these conditions, the amount of ink pooling on the lower surface of the thin plate member 181 showed a tendency to decrease compared to the case of Experimental Example 2 of the present application. Specifically, when printing 2,000 sheets continuously, a thin bar of ink within 1 mm in diameter is printed on the front edge 181e of the ink outlet side.
However, no ink puddle growth was observed for the indigo blue and grass blue inks even after printing 6,000 to 8,000 sheets. As for the brown color, it was observed that it gradually grew to a diameter of about 2 mm after 6000 to 8000 sheets, but there was no fear of it falling and there was no problem in practical use. (b-4) Experimental example 4 of the present invention In FIG.
All other settings were the same as in Experimental Example 1 of the present invention. When the ink film 26a was formed under these conditions, the thin plate member 1
The amount of ink pooling on the lower surface of No. 81 was further reduced compared to the case of Experimental Example 3 of the present application. In other words, after continuous printing of 2000 sheets, thin ink sticks of less than 1 mm in diameter partially adhere to the leading edge 181e on the ink outlet side, but no ink pools are observed to grow even after 6000 to 8000 sheets of ink of each color are printed. I couldn't help it. (b-5) Experimental example 5 of the present invention In FIG. 9, the radius of curvature γ of the leading edge 81e on the ink outlet side of the thin plate member 181 is
All other settings were the same as in Experimental Example 1 of the present invention. When the ink film 26a was formed under these conditions, the thin plate member 1
Regarding the ink pooling on the lower surface of No. 81, the same results as in Experimental Example 4 of the present invention were obtained. In other words, after continuous printing of 2000 sheets, a stick of ink within a diameter of 1 mm partially adheres to the leading edge 181e on the ink outlet side, but even after printing 6000 to 8000 sheets of ink of each color, no ink pool growth was observed. Ta. Furthermore, although a prototype was made to set the radius of curvature γ of the leading edge 181e on the ink outlet side of the thin plate member 181 to 0.2 μm, the radius of curvature γ over the entire length was
The experiment was abandoned because stability could not be obtained. (c) Factors determining the upper limit of the thickness of the thin plate member 181 Here, the upper limit of the thickness d of the thin plate member 181 will be considered. As shown in FIG. 10a, the thickness of the thin plate member 181 is defined as d, and the height of the flat portion at the tip is defined as H. Now, assuming that the radius of curvature R of the leading edge of the thin plate member 181 on the ink introduction side is set to a constant value, if the plate thickness d of the thin plate member 181 is set large, the flatness at the tip of the thin plate member 181 will increase. The height H of the part becomes larger and the first
As shown in Figure 0b, the area of "high" pressure corresponding to the flat portion H becomes wider. As a result, the force exerted by the thin plate member 181 on the roller 12 increases, and the deformation of the roller 12 increases.
The thickness of the ink film 26a increases. By the way, the appropriate film thickness (3~
15 μm), it is necessary to reduce the radius of curvature R of the ink introduction side front edge 181e of the thin plate member 181, or to increase the amount by which the thin plate member 181 is pushed into the roller 12. However, when the radius of curvature R is set to 30 μm or less, a problem arises in that the roller surface is damaged by the leading edge on the ink introduction side. Further, if the thin plate member 181 is pushed in by 0.6 mm or more, there will be a problem that the durability of the rubber roller will be impaired due to friction and heat generation. From these, the appropriate plate thickness d and radius of curvature R are determined, and these specific values are d = 0.1 to 0.8
mm, R≧0.03 mm. (d) Factors determining the lower limit of the thickness of the thin plate member 181 Next, the lower limit of the thickness d of the thin plate member 181 will be considered. As shown in FIG. 11a, when the thickness d of the thin plate member 181 is set small,
As shown in FIG. 11b, the range of the high pressure part at the tip of the thin plate member 181 is reduced,
As the pressure exerted on the roller 12 is reduced, the roller deformation is also reduced, resulting in an ink film 26
The thickness of a becomes thinner. In order to obtain an appropriate ink film thickness (3 to 15 μm) under such circumstances, it is necessary to increase the radius of curvature R or to decrease the amount by which the thin plate member 181 is pushed into the roller 12. However, in the former case,
The radius of curvature R cannot be set larger than the plate thickness d,
Moreover, since the plate thickness d is set to be small here, there is a limit to setting the radius of curvature R to be large. On the other hand, in the latter case, a predetermined pushing amount (for example, 0.2 mm or more) is required to obtain a uniform film thickness along the roller axial direction, and if the pushing amount is too small, the thin plate member 181 will be pushed in the roller axial direction. Due to the influence of the shape of the tip along the roller and the shape of the roller surface, it becomes impossible to form a substantially uniform ink film along the roller axis direction. Further, if the thickness d of the thin plate member 181 is made smaller, a problem arises in that the rigidity of the cutting edge is reduced. From the above, the appropriate plate thickness d and radius of curvature R are determined, and their specific values are d=0.1 to 0.8 mm and R≦0.1 mm. (5) Example 2 (a) Principle Instead of the two-layer rubber roller 12 shown in FIG. 9, a single-layer rubber roller 2 as shown in FIG.
Let us consider the case where 7 is used. In this case, the same doctor blade as the doctor blade of Example 1 of the present application shown in FIG. 8 is used. When the rubber roller 27 is used, the deformation of the rubber roller is concentrated locally in response to the pressure applied to the tip of the thin plate member 181, and a bump-like bulge deformation occurs near the ink introduction side leading edge 181c. Similarly, bulging deformation as shown in the figure is also seen near the leading edge 181e on the ink outlet side (pressure release area). Therefore, the thin plate member 1
The relative angle between the vicinity of the front edge of the lower surface 181d of the rubber roller 27 and the surface of the rubber roller 27, that is, the clearance angle in FIG. Become. As a result, for the same reason as explained using FIG. 6, the peeling point shifts to the right in the figure, creating a wetted surface near the front edge of the lower surface 181d of the thin plate member. In reality, by the time this peeling point is reached, fractures occur in the ink due to non-uniformity of the ink, and ink pools occur. Ink 2 remaining on the thin plate member 181 in this way
Since ink 6 has a velocity component V along the thin plate member 181, it is gradually pushed out and an ink pool S grows. However, the doctor blade used here is the same as the doctor blade of Embodiment 1 of the present application shown in FIG. In addition, since the radius of curvature r of the leading edge 181e on the ink outlet side is set to 20 μm or less, the growth rate of the ink pool S can be suppressed considerably lower than in Comparative Examples 1, 2, and 3. (b) Experimental Example 6 In place of the two-layer rubber roller 12 shown in FIG. 9, a single-layer rubber roller 2 as shown in FIG.
7, and the other conditions were set exactly the same as in the case of Experimental Example 2 of the present invention described using FIG. If a thin ink film is formed under these conditions, a small linear ink rod with a diameter of about 1 mm will adhere after 2,000 continuous prints, and then continue to grow to become ink droplets. And continuous
It grows to the point where it falls after 6,000 to 8,000 pieces. The experimental results of Comparative Experimental Examples 1 to 3 and Examples 1 to 6 of the present application are summarized as shown in the table below. In addition, the meaning of each symbol of the experimental conditions used in the table below is as follows. M; represents the method of supporting the thin plate member 181;
"Non" indicates a non-flexible support method, and "Possible" indicates a flexible support method. θ: Front end surface 181b of thin plate member 181 and ink outlet side surface 181f or lower surface 18
Angle (degrees) formed with 1d R: Radius of curvature of the leading edge of the ink introduction side of the thin plate member 181 (μm) r: Radius of curvature of the leading edge of the ink outlet side of the thin plate member 181 (μm) N: Rubber coating of the ink form roller Number of layers (layers) In addition, the criteria for determining the results are as follows. X: The ink pool falls within 30 minutes after printing starts. △: The ink puddle may fall within 60 minutes. ○: A little growth of the ink pool is observed within 1 to 2 hours, but it does not lead to falling. ◎: The ink pool does not grow even after 2 hours or more. Note that the number of sheets printed corresponding to the 30 minute printing time of the inking device used in the comparative example and the example of the present application is approximately 2300 sheets.

[Table] As is clear from the above table, when comparing the comparative example and the experimental example of the present application, the supporting method of the thin plate member 181 is the non-flexible supporting method, the relief angle θ is 90°,
It can be seen that when the radius of curvature r is 20 μm or less and the number of rubber coating layers of the ink forming roller 12 is 1 to 2, good results can be obtained in preventing back sag. In particular, the radius of curvature r of the thin plate member 181
When it is set to 10 μm or less, the effect of preventing back sagging becomes higher, and continuous operation for 1 to 2 hours becomes possible. Furthermore, the radius of curvature r is set to 5 to 0.5 μm.
By doing so, stable printing can be achieved with many types of ink without sagging on the back side for a long time. (6) Reference experiment example In Fig. 9, doctor blade thin plate member 1
The radius of curvature R of the ink introduction side leading edge 181e of 81
Various doctor blades with diameters of 20 .mu.m, 30 .mu.m, 50 .mu.m, 75 .mu.m, and 100 .mu.m were prepared, and printing was carried out under the same conditions as in Experimental Example 1 of the present application explained using FIG. FIG. 13 shows a density index obtained by measuring the density of a solid portion of a printed matter printed under the above conditions using a reflection densitometer (Gretag densitometer) using a blue filter. In Fig. 13, the pushing amount △P (mm) of the doctor blade, which is the index on the horizontal axis, is the first
As shown in the figure, the thin plate member 181 is
It represents the distance that the tip has moved in the approximate radial direction of the ink forming roller 12 (in other words, the distance that it has been pushed). The value of this pushing amount △p is
Dimensions and physical properties of ink form roller 12, ink 2
Although it may be selected appropriately depending on the usage conditions such as No. 6, in this experimental example, it was set to 0.2 to 0.5 mm.
When the pushing amount △p is less than 0.2 mm, the ink film thickness tends to become unstable due to the influence of variations in the accuracy and assembly precision of each component that makes up the inking device, while on the other hand, when the pushing amount △p exceeds 0.5 mm,
This is because not only the driving energy of the ink forming roller 12 becomes excessive, but also causing problems such as heating of the ink forming roller 12. As is clear from FIG. 13, the density at the time of pressing for each radius of curvature R is found to be darker as the value of R is larger, and lighter as the value of R is smaller. In this experiment, the solid density on printed matter using high-quality paper as the printing material was in the range showing the standard density index of 1.0 to 1.4, and in the range where the pushing amount △p was 0.2 to 0.5 mm. The radius R of the curve that can realize almost the entire region specified by is 50 μm and 75 μm. radius of curvature R
When the radius of curvature R
When the printing density is 100 μm, the printing density becomes dark over the entire area, making it difficult to obtain a low density. However, in printing that accepts these tendencies, a radius of curvature R of 30 μm or 100 μm can be used satisfactorily. On the other hand, the radius of curvature R is 20 μm
In this case, the printing density was low over the entire area, and density unevenness occurred in the printing width direction, making it unusable. Although the inking device for an offset printing press has been described above, this invention can also be widely applied to inking devices for general printing presses such as letterpress printing and planographic printing. It can also be widely applied to so-called coating devices that form shapes. (Effects of the Invention) As described above, in the coating device of the present invention, the coating roller is formed of an elastic roller, and the thin plate member of the doctor blade is substantially inflexible in the tangential direction of the outer peripheral surface of the coating roller. support in the state,
In addition, since the leading edge of the ink outlet side at the tip of the thin plate member is curved and the radius of curvature is set to 20 μm or less, it is possible to prevent the coating liquid from dripping from the doctor blade even during long-term operation. .

[Brief explanation of the drawing]

Fig. 1 is an enlarged sectional view of the main parts of an inking device which is an embodiment of the present invention, Fig. 2 is a schematic sectional view of an offset printing press equipped with the above inking device, and Fig. 3 is a schematic sectional view of the inking device. , FIG. 4 is a plan view of the inking device, FIG. 5 is a sectional view of main parts of the inking device during ink film formation, FIG. 6 is an explanatory diagram of Comparative Example 1, and FIG. 7 is an explanatory diagram of Comparative Example 2. Fig. 8 is an explanatory diagram of Comparative Example 3, Fig. 9 is an explanatory diagram of Example 1 of the present application, and Fig. 10 is an explanatory diagram of Comparative Example 3.
11 is an explanatory diagram when the thickness of the doctor blade thin plate member is set to be small. FIG. 12 is an explanatory diagram of Example 2 of the present application. Fig. 13 is a characteristic diagram showing the relationship between the amount of depression of the doctor blade and the Gretag reflection densitometer index, Fig. 14 is a cross-sectional view of the conventional example,
FIG. 15 is a sectional view of another conventional example. 12... Ink application roller, 18... Doctor blade, 26... Ink, 26a... Ink film,
122...Inner layer, 123...Outer layer, 181...Thin plate member, 181e...Ink outlet side leading edge, 182
...Upper holding member, 183...Lower holding member, r
……curvature radius.

Claims (1)

[Claims] 1. A coating roller having an elastic surface, and a coating roller disposed so as to be able to move forward and backward in the approximate radial direction of the coating roller with respect to the outer circumferential surface of the coating roller to adjust the thickness of a coating film formed on the outer circumferential surface of the roller. In the coating device, the doctor blade is configured to include a thin plate member whose tip is pressed against the outer circumferential surface of the coating roller, and a thin plate member that is substantially movable in a tangential direction to the outer circumferential surface of the coating roller. and a holding member that holds the thin plate member in a non-flexible state, and the front edge on the ink outlet side at the tip of the thin plate member is curved to have a radius of curvature of 20μ.
A coating device characterized in that the coating temperature is set to less than m. 2. The coating device according to claim 1, wherein the coating roller has a multilayer structure in which the surface layer has a higher hardness than the inner layer. 3. The coating device according to claim 1 or 2, wherein the coating roller is an ink forming roller.