JPS63302049A - Coating device - Google Patents

Abstract

PURPOSE:To prevent a coating liquid from running off even in a long-time drive, by a method wherein, a coating device consists of a film member and members holding the film member in unflexible states, an ink guiding-side front edge at the tip end of the film member is formed to be bent with a radius of 20 mum or less. CONSTITUTION:A doctor blade 18 consists of a sheet member 181 to be pressed down against the peripheral surface of an application roller 12 at the tip end thereof and upper and lower holding members 182, 183 holding the sheet member 181 in substantially unflexible states tangentially to the peripheral surface of the application roller 12. An ink guiding-side front edge at the tip end of the sheet member 181 is formed to be curved with a radius of curvature (r) of 20 mum or less. The setting of the radius of curvature (r) to be 20 mum or less enables a coating liquid to be prevented from running off from the doctor blade 18 even in a long-time drive.

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, and particularly to a coating device that prevents the growth and fall of coating liquid deposits from the back surface of a doctor blade (hereinafter referred to as This invention relates to a coating device with improved sharpness.

(Prior art and its problems) An inking device in which a doctor blade is directly pressed against an ink forming roller having an elastic surface such as rubber to form a thin ink film is disclosed in, for example, Japanese Patent Laid-Open No. 57-1788.
The inking device disclosed in No. 72 and Utility Model Application No. 56-76
An inking device disclosed in No. 1.38 is known.

The inking device of the former (Japanese Patent Application Laid-Open No. 57-178872) is
As shown in FIG. 14, the ink layer 1 roller 1 is constituted by a layer of rubber rollers, and the doctor blade 2 is held approximately in the tangential direction of the ink layer E layer 1 and scrapes ink at its tip position. A section 2a is provided. In the ink scraping portion 2,a, the ink introduction side leading edge 2b and the ink outlet side leading edge 2C are polished to have sharp edges with extremely small radii of curvature. There is. In this inking device, the ink scraping portion 2 of the doctor blade 2 is
The ink film 3a is formed by rotating the ink forming roller 1 in the direction of the arrow in the figure while pressing the ink forming roller 1 onto the ink forming roller 1.If a high viscosity ink is used as the ink 3, the doctor blade The ink scraping part 2a bends forward due to the deflection of the roller 2, and further affected by the deformation pattern of the roller 1, an ink pool is generated on the lower surface side of the ink scraping part 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 58 portion, and when the ink is operated for a long period of time, sagging occurs, which is the same problem as in the case of the above-mentioned inking device.

The above explanation has been given regarding the sagging of the inking device in the printing press, but 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 a coating roller having an elastic surface, and a coating roller disposed on the outer circumferential surface of the coating roller so as to be movable forward and backward in the approximate radial direction of the coating roller. A coating device comprising a doctor blade for adjusting the thickness of a coating film, in order to achieve the above object, the doctor blade is a thin plate member whose tip is pressed against the outer peripheral surface of the coating roller; and a holding member that holds the thin plate member in a substantially inflexible state in the tangential direction of the outer circumferential surface of the application roller, and a front edge on the ink outlet side at the tip of the thin plate member is curved. , the radius of curvature is set to 20 μm or less.

(Embodiment) A. Structure 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 blanket cylinder 61, a plate cylinder 7, and an impression cylinder 8, and has an inking device 9 detachably attached to the plate rI47. The printing work is
After wrapping the plate 10 around the plate cylinder 7 and passing the continuous paper 11 between the blanket 116 and the impression cylinder 8, the continuous paper 11 is rotated in the direction of the arrow in the figure by rotating the multi-cylinders 6, 7.8 in the direction of the arrow in the figure. While feeding in the direction of the arrow, ink is supplied from the ink supply M9 to the printing area of the plate 10, and the ink supplied to the plate 10 is further transferred onto the continuous paper 11 via the blanket 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 mounted on left and right frames 14,14. Further, kneading rollers 15 and 16 are rotatably attached to the left and right frames 14, 14 and swingably in the roller axial direction.

These kneading rollers 15 and 16 are constructed such that their end surfaces are located outside of the end surface of the inking roller 12 at their oscillation vJ 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°19 attached to both ends of the doctor blade 18, and these left and right side plates 19.
9. Left and right fulcrum pins 20 installed at the top position of 19
．． 20, and these left and right fulcrum pins 20.20 are connected to left and right pin receivers 2 provided on the left and right frames 14.14.
By fitting at an angle of 1° 21, it is held swingably in the front-rear direction in FIG. 3 using the fulcrum pin 20 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 arc shape so as to substantially follow the outer circumferential surface of the ink form roller 12, and the front end surfaces 19a of the left and right side plates 19.
2 at a position facing the outer circumferential surface of the roller. As a result, an ink reservoir space 22 surrounded by the doctor blade 18, the left and right side plates 19.degree. 19, and the ink forming 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, and these left and right rollers 25,
25 is rotatably attached to the left and right frames 14 and 14 so as to be in contact with the back surface of the doctor blade 18. This blade pressing member 23 is driven to rotate forward and backward by a pulse motor (not shown), its rotation angle is controlled by an electronic circuit, and its rotation range is controlled 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 ink forming roller 1 which is the key point of this invention
2 and the structure of the doctor blade 18 will be explained in detail with reference to FIG. 5 and FIG. FIG. 5 shows a cross-sectional view of the main part of the inking device 9 when forming an ink thin film,
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. Then, the rotating shaft 121
Both ends of the plate 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 meshes with a plate cylinder gear (not shown) to drive the plate cylinder. It is configured as follows. The surface of the ink form roller 12 is highly finished in roundness and straightness to prevent rotational run-out, and the preferred values thereof are approximately 0.02 roundness and 003 straightness. The surface hardness of the ink forming roller 12 is JISK-6
It is desirable that the rubber hardness is set at 15° to 70° as defined in 301. If the hardness is less than 15°, it will be impossible to form a thin ink film (3 to 15 μm) suitable for printing. On the other hand, if the hardness exceeds 70', not only will it be impossible to obtain a stable ink film, but it will also be difficult to form a normal ink film on the plate surface. This is because the ink transfer becomes impossible.A more preferable value for this hardness is 25°.
~50°.

Next, the doctor blade 18 is composed of a rigid upper holding member 182 and a rigid lower holding member 183, which hold the thin plate member 181 by sandwiching it from above and below, leaving the tip part. Member 18
The ink forming roller 12 is disposed such that its tip end is in contact with the outer circumferential surface of the ink forming roller 12. The thin plate member 181 has a thickness of, for example, 0.
Constructed of 1~0°8# Swedish steel. Further, the amount of protrusion 11 of the tip of the thin plate member 181 from the upper holding member 182 and the amount of protrusion a from the lower holding member 183 are determined when the doctor blade 18 is attached to the ink forming roller 12 when forming an ink thin film, as shown in FIG. When the ink application roller 12 is rotated in the direction of the arrow while being pressed by the thin plate member 181 as the roller 12 rotates,
The dimensions are set such that even if the tip of the roller is subjected to a force that causes the tip to bend and deform in the tangential direction of the roller outer circumferential surface, substantially no bending deformation occurs. As an example of preferable dimensional values for the amount of protrusion, the spear is 1.9 aw, and the a is 0.58.

At the tip of the thin plate member 181, the ink introduction side front edge 181c located at the intersection of the upper surface 181a and the front end surface 181b is curved with a radius of curvature of dimension R, and the lower surface 181d and the front end The angle formed with the surface 181b is substantially 90 degrees, and the ink outlet side leading edge 181e located at the portion where these two surfaces intersect is similarly finished with a curved surface having a radius of curvature of the 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 1, and the ink form roller 12
The elasticity of the doctor blade 18 of the inking roller 12
It changes depending on the relative speed to the ink, the viscosity of the ink 26, etc., and an appropriate value may be selected within the above range of 30 μm or more.

- For 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 the ink from dripping from the thin plate member 181, the radius of curvature r of the ink outlet side leading edge 181e is
It is necessary to set it 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. When set to tiles, the peeling force is more stable than in the above case, so it is possible to prevent ink pooling from occurring even with more types of ink.

Below, 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 and experiment of back dripping Results (1) Comparative example 1 (a) Principle First, as shown in FIG. Angle where the angle θ is smaller than 90 degrees (for example, 45 degrees)
A case will be considered in which the ink film 26a is formed using a doctor blade set to . In this case, the ink forming roller is an ink forming roller 1 having a two-layer structure shown in FIG.
2 is used.

Ink outlet side front edge 18 of doctor blade thin plate member 181
The velocity distribution of the ink 26 at the position P1 close to 1q is
As shown in FIG. 6(b), the roller surface speed V at the boundary of the ink form roller 12. approximately equal to the thin plate member 18
The velocity approaches zero as it approaches the 1 side. On the other hand, the ink 26 at position P2 immediately after the formation of the ink film 26a
The velocity distribution of is the roller surface velocity V. is equal to Therefore, the ink flowing along the boundary surface of the thin plate member 181 has a velocity of from zero to ■ near the leading edge 1810 on the ink outlet side. It accelerates while changing direction. 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
This means that it is oxidized at the boundary surface of 1. However, as shown in FIG. 6, when the clearance angle θ at the tip of the thin plate member 181 is set small, the leading edge 181
Since the ink velocity changes slowly in the vicinity of q, the force F
The position where the ink becomes large enough to cause ink peeling moves toward 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 the peeling point. In this way, the ink 26 remaining near the ink outlet side front edge 181g of the thin plate member 181 is removed from the tapered surface 181f of the thin plate member 181.
Since the ink has a velocity component V along the line, it is gradually pushed out and an ink pool S as shown in FIG. 6(b) is generated.

This ink puddle S grows with the passage of operating time, and eventually the own 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 cause the ink 26 and the thin plate member The adhesive force of the ink 181 or the breaking stress of the ink 26 becomes greater, and the ink 26 falls from the thin plate member 181.

From the above, the relief angle θ formed by the ink outlet side 181f and the tangent to the outer circumferential surface of the applicator roller is 80 to 10
The angle is preferably 0 degrees, more preferably 85 to 95 degrees, and most preferably substantially 90 degrees. If the clearance angle θ is set outside the above range, it will not be possible to obtain a thin plate member in which the thickness d and radius of curvature r of the thin plate member 181 are stable in the width direction due to manufacturing reasons. n% of the ink is not obtained.

(b) Comparative Experiment Example 1 First, as the ink application roller 12, a rigid core 0121 (
Using a metal round bar with a diameter of 20 m (Fig. 5), a soft cushion rubber layer with a rubber hardness of 20' was provided as the inner layer 122, and after its outer diameter was set to 50 m, a layer was placed on top of it. A rubber layer with a rubber hardness of 30° is used as the outer layer 123.
Outer diameter 6 Q rt formed by rolling with a thickness of mm
a, a two-layer rubber roller with a length of 418# was used. The surface of this roller is finished to be as smooth as possible, and the roundness is 0.02 and the runout relative to the reference axis is 0.02, which is highly accurate.

On the other hand, the doctor blade is a thin plate member 18 in FIG.
1 is made of Swedish steel, the distance 1t between the upper surface 181a and the ink outlet side leading edge 181q is 0.15 m, and the upper surface 18
The distance between 1a and the lower surface 181d, that is, the plate thickness d, is 0.8
Set to mm. In addition, the protrusion amount 1 of the tip of the thin plate member 181 from the upper holding member 182 is set to 1.9 mm, the protruding suspension a from the upper holding member 183 is set to 0.5 m (inflexible support), and the clearance angle is 0. Set the angle to 45 degrees. Further, the radius of curvature R of the leading edge 181C on the ink introduction side of the thin plate member 181 is set to 50 μm, and the radius of curvature r of the leading edge 1810 on the ink leading side is set to 10 μm.

Offset printing II (V
Printing experiments were conducted using S-1000 (manufactured by Toshi Engineering-1G-■). The ink 26 used was
Standard ink for waterless lithography (viscosity 500-3,000
0 poise), and the color used was indigo. Print speed is 4.5
001. The ink adhesion at that time was P and H [The number of rotations of the roller 12 was 192 R:P,H.

When printing under the above conditions, 2,000 to 40 consecutive
After printing 00 sheets, an ink pool S occurred and fell.

(2) Comparative Example 2 (a) Principle As shown in FIG. is set to a value larger than 20 μm, for example, 40 μm. In this case, as in Comparative Example 1, a two-layer roller is used as the ink deposition roller 12.

The radius of curvature r of the leading edge on the ink outlet side is 20μ as described above.
If the size is larger than m, the deformation of the ink forming U roller 12 that occurs during the formation of the ink film will recover along the surface of the thin plate member 181 with a curve as shown in FIG. The velocity distribution of the flow of the ink 26 at the tip 21 of the thin plate member 181 is V such that the roller boundary surface is approximately equal to the roller circumferential speed, as in Comparative Example 1 above. , and the thin plate member 1
The velocity Vn at the boundary surface decreases as it approaches 81.
approaches zero. On the other hand, the velocity distribution at the 12 points where the ink film 26a has been formed, immediately after passing the leading edge on the ink outlet side, is entirely equal to the roller surface velocity V□. Therefore, in this case as well, the ink flowing along the boundary surface of the thin plate member 181 is located at J5 near the 21st point f, and the velocity changes from zero to V.
It is accelerated while changing direction to □, and a force ``that tends to peel off the ink 26 from the surface of the thin plate member 181'' is generated.

However, if the radius of curvature r of the leading edge of the ink outlet side of the thin plate member 181 is set large, the speed change in the vicinity of point 21 becomes gradual, and the force F becomes large enough to cause ink peeling. As in the case of Comparative Example 1, the position where the paper is removed moves toward the lower right of the figure. As a result, as in the case of Comparative Example 1, the ink remaining on the thin plate member 181 is The ink puddle S is generated by being gradually pushed out by the velocity component (2) along the surface, and as the ink puddle S grows over a long period of operation, it will fall.

(b) Comparative Experiment Example 2 The thin plate member 181 was 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 were set to 40 μm, respectively, and the relief angle θ was set to 90°, and The plate thickness d is set to 0.15 am. Other conditions are
When the ink film 26a was formed using all the same settings as in Comparative Experiment Example 1, an ink pool S was generated and dropped before the number of continuous prints reached 2000 sheets.

(3) Comparative Example 3 (a) Principle As shown in FIG. A case will be considered in which the protrusion fjkl and a at the ink forming roller 12 are set to a size that allows the tip of the thin plate member 181 to have flexibility in the tangential direction of the outer peripheral surface of the roller as the ink form roller 12 rotates. In this case as well, a two-layer roller is used as the ink forming roller 12.

Now, in FIGS. 8(b) and 8(c), 1: Distance a from the upper holding member 182 to the tip of the thin plate member 181: Distance from the lower holding member 183 to the tip of the thin plate member 181 b: j! -a E: Young's modulus of the thin plate member 181 ■: Moment of inertia of the thin plate member 181 W: When defined as the force applied to the tip of the thin plate member 181, the maximum deflection y at the tip of the thin plate member 181 is expressed by the following formula. expressed.

Here, as a specific example, when comparing the deflections of the following two examples, [Example 1] 1=1.9. When a=0.5, y1=0.13 (W/ET) [Example 2]! =1.9. When a = 1.5, V2 = 1, 35 (W/ E I ), that is, a
When the value of is 1.5 thickness, the deflection My is 10.5 times that of 0.5a+m (y2/y1 = 10.5)
It also becomes. 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 about 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 form roller 12 and the flow of ink when such a deflection occurs is shown in FIG. can. Under this condition,
In the ink velocity distribution at 21 points just before ink film formation, the roller surface boundary position is ■. The largest value is V at the boundary surface of the tip of the thin plate member. is almost zero. At this time, the velocity distribution (from vo to V.) gradually changes due to the reverse wedge-shaped ink flow until it reaches position P1. As a result, the tensile force F in the ink is generated earlier than in the case where there is no deflection. Although this force F is not strong enough to peel off the ink 26 from the front end surface 181b of the thin plate member 181 at once, it causes breakage at a weak portion in the ink.

As a result of these irregular breaks in the ink,
The ink left behind on the thin plate member 181 side is removed from the thin plate member 18.
The particles are gradually deposited due to the velocity component (2) along the surface of the thin plate member 1 and the wetting of the lower surface 181d of the thin plate member.

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 the flexible support method, the front end surface 181b of the thin plate member 181 is tangential to the outer circumferential surface of the ink form roller 12 in comparison experiment example 1.
Since an inclined surface corresponding to the relief angle θ is formed, the same problem as in Comparison Experiment Example 1 occurs.

A similar phenomenon also occurs when the thin plate member 181 is mounted (pull) in an orientation facing diagonally downward.

(b) Comparative Experiment 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 protrusion amount 1 of the tip of the member 181 is 1
．． 9mm, a was set to 1°5#. 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-tree 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 of the present application (a) Principle As shown in FIG. The protrusion amount 1 and a at the tip are determined by ink deposition (j
A case will be considered in which the size is set such that the tip end of the thin plate member has substantially no flexibility in the tangential direction of the outer circumferential surface of the roller as the roller 12 rotates. The specific values of the protrusion amounts l and a are, for example, j as in Example 1 above.
! = 1.9 m, 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 11 points immediately before the leading edge 181e on the ink outlet side is fastest at the roller boundary surface. , which becomes almost zero at the latest at the boundary surface 181b of the thin plate member 181 (V, armature O). Also, the ink speed at 22 points immediately after the ink film is formed is the roller surface speed■
. is equal to

Therefore, the speed near P1 is ■. The ink flow for ≠O is
From the flow parallel to the roller surface and the front end surface 181b of the thin plate member, the speed rapidly increases toward the roller 12 side, that is, in the direction F, and the roller surface speed V. becomes. That is, the ink near the boundary surface of the thin plate member at 11 points has a velocity V. It accelerates while changing direction. 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 greater than the interfacial tension J between the ink and the surface of the thin plate member, the ink will smear at the blade interface. However, if the thin plate member 181 satisfies r≦20 μm and is not deflected downward, the speed change as described above near P1 occurs rapidly and instantaneously.

Therefore, the force F also increases rapidly, so that the force F overcomes the interfacial tension on the surface of the thin plate member, and the leading edge 18 on the ink outlet side
Stable delamination occurs at 1e. 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, when the ink forming roller 12 having a two-layer structure in which the outer layer 123 is harder than the inner layer 122 is used as the ink forming roller, a rubber roller that reduces the clearance angle of the thin plate member tip surface 181b with respect to the roller surface is used. Since the swelling deformation of the ink is reduced, the above-mentioned peeling occurs more stably, and ink pooling becomes less likely to occur.

(b-i) Experimental example 1 of the present invention In FIG.
The radius of curvature γ of the thin plate member 181 was set to 15 μm, and the amount of protrusion a at the tip of the thin plate member 181 was set to 0.5#. The ink used was a standard ink for waterless lithography (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 Example 3 shown in FIG. When the ink film 26a was formed under these conditions, the thin plate member 181 showed 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 having a diameter of about 1 to 2 # adhered to the leading edge 181e on the ink outlet side. After that, even after printing about 4,000 sheets, the growth of the indigo ink puddle was small, and there was no fear of it falling. Furthermore, with regard to the grass-colored and brown inks, which are extremely susceptible to the formation of ink puddles among inks, there were cases where ink puddles were observed to grow after 4,000 sheets, but it did not reach the point of falling and was not a problem for practical use. Ta.

(b-2) Experimental Example 2 of the Present Application In FIG.
The radius of curvature γ of 1e was set to 10μ side, and all other settings were set equal to those in Experimental Example 1 of the present application.

When the ink film 26a was formed under these conditions, a thin rod-shaped ink with a diameter of 1 m 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, almost no growth was observed, and even when 6,000 to 8,000 sheets were continuously printed, there was no fear of the sheets falling off. Continuous 6 for grass color and brown
Although it grew to a diameter of about 2# after 000 to 8000 sheets, it did not fall to the point of falling, and there was no problem in practical use.

(11-3) Experimental example 3 of the present invention In FIG.
The radius of curvature γ of 81e was set to 6 μm, and all other settings were the same as in Experimental Example 1 of the present application.

When the ink H1J 26a was formed under these conditions, the amount of ink pooling on the lower surface of the thin plate member 181 tended to decrease compared to the case of Experimental Example 2 of the present invention. Specifically, after continuous printing of 2000 sheets, a thin rod-shaped ink with a diameter of 1 or less is partially attached to the leading edge 181e of the ink outlet side, but after that, ink of indigo and grass color is printed 6000 to 8000 times.
No ink pool growth was observed even after printing. As for the brown color, although it was observed that the size gradually grew to about 2 mm in diameter after 6,000 to 8,000 sheets, there was no fear of the sheet falling and there was no problem in practical use.

(1)-4) Experimental example 4 of the present invention In FIG.
The radius of curvature γ of 81e was set to 4 μm, and all other settings were the same as in Experimental Example 1 of the present application. 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 was further reduced compared to the case of Experimental Example 3 of the present invention.

In other words, after continuous printing of 2000 sheets, a thin rod-shaped ink with a diameter of 1 # or less partially adheres to the leading edge 181e on the ink outlet side, but after that, 6000 to 8000 sheets of ink of each color are printed.
No growth of ink pools was observed even after printing.

(b-5) Experimental example 5 of the present invention In FIG.
The radius of curvature γ of 81e was set to 1 μm, and all other settings were the same as in Experimental Example 1 of the present application.

When the ink film 26a was formed under such conditions, the same results as in Experimental Example 4 of the present application were obtained regarding the ink pooling on the lower surface of the thin plate member 181. In other words, in continuous printing of 2000 sheets, the ink bar with a diameter of 1 s or less is transferred to the front edge 181 on the ink outlet side.
However, no ink pool growth was observed even after printing 6,000 to 8,000 sheets of ink for each color.

Furthermore, a trial 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, but the experiment was abandoned because the stability of the radius of curvature γ over the entire length could not be obtained.

' (cl Wj Deciding factor for upper limit of plate thickness of plate member 181 Here, the upper limit of plate thickness d of thin plate member 181 will be considered.

As shown in FIG. 10(a), 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, the radius of curvature R of the front edge of the thin plate member 181 on the ink introduction side
is set to a constant value, the thin plate member 18
When the plate thickness d of 1 is set large, the thin plate member 181
The height H of the flat portion at the tip becomes larger, and as shown in FIG. 10(b), the region of "high" pressure corresponding to the "flat portion 1" becomes wider. As a result, the thin plate member 181
The force exerted on the roller 12 increases, and the roller 12
deformation increases, and the thickness of the ink film 26a increases. By the way, the appropriate film thickness for ink FJ26a is 3.
~15μTrL), the radius of curvature R of the ink introduction side front edge 181e of the thin plate member 181 should be made small, or
Alternatively, it is necessary to increase the amount by which the thin plate member 181 is pushed into the roller 12. However, the radius of curvature R is 3
If it is set to 0 μm or less, there will be a problem that the roller surface will be damaged by the leading edge on the ink introduction side. Further, if the thin plate member 181 is pushed in by more than 0.6 mm, 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.
#, R2O, 03m.

(d) The lower limit of the thickness d of the thin plate member 181 will be considered in the element method for determining the lower limit of the plate thickness of the thin plate member 181. 11th
As shown in FIG. 11(a), when the thickness d of the thin plate member 181 is set small, the thin plate member 181
The range of the high-pressure part extending to the tip of the roller 81 is reduced, the pressure exerted on the roller 12 is reduced, and the roller deformation is also reduced, and as a result, the thickness of the ink film 26a becomes thinner. Under these circumstances, the appropriate ink film thickness (3 to 15 μm)
), it is necessary to increase the radius of curvature R or to reduce 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 is the plate thickness d
There is a limit to setting the radius of curvature R to a large value because the plate thickness d cannot be set larger, and the plate thickness d is set to be smaller here. On the other hand, in the latter case, in order to obtain a uniform film thickness along the roller axis direction, a predetermined amount (for example, 0
If the pushing amount is too small, the tip shape of the thin plate member 181 along the roller axis direction and the roller surface shape will affect the roller axis -, jl.
It cures in one direction, making it impossible to form a substantially uniform ink film. 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≦051#.

(5) Example 2 (a) Principle A case will be considered in which a single layer rubber roller 27 is used as shown in FIG. 12 instead of the two layer rubber roller 12 shown in FIG. 9. 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 using the single-layer rubber roller 27, the thin plate member 181
In response to the suppression of the tip, the deformation of the rubber roller concentrates locally, and a bump-like bulge deformation occurs near the ink introduction side leading edge 181c. Similarly, near the leading edge 181e on the ink outlet side (
As shown in the figure, bulging deformation can also be seen in the pressure release area. Therefore, the relative angle between the front edge of the lower surface 181d of the thin plate member 181 and the surface of the rubber roller 27, that is, the clearance angle in FIG.
It is smaller than in case 2 (see FIG. 9). As a result, for the same reason as explained using FIG. 6, the peeling point moves 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 point is reached, fractures occur in the ink due to non-uniformity of the ink, and ink pools occur.

The ink 26 thus remaining on the thin plate member 181 has a velocity component V along the thin plate member 181, so 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 Example 1 of the present application shown in FIG. 9, that is, the tip of the thin plate member 181 is held substantially inflexible, In addition, since the radius of curvature r of the ink outlet side ftLIR 181e is set to 20 μm or less, the growth rate of the ink pool S is suppressed to be considerably lower than that of each of the above comparative examples 1°2.3.

(b) Experimental Example 6 of the present invention In place of the two-layer rubber roller 512 shown in FIG. 9, a single-layer rubber roller 27 is used as shown in FIG. All settings are the same as in Experimental Example 2. When a thin ink film is formed under these conditions, a small linear ink rod with a diameter of about 1 # is attached after 2,000 continuous prints, and then continues to grow to form an ink reservoir.

Then, it grows to such an extent that 6,000 to 8,000 sheets fall in a row.

The experimental results of Comparative Experimental Examples 1 to 3 and Experimental 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, with "non" indicating a non-flexible supporting method and "possible" indicating a flexible supporting method.

θ; ; Angle (II
) R; radius of curvature of the leading edge of the thin plate member 181 on the ink introduction side (μ
TrL) r; radius of curvature (μ
m) N: Number of rubber coating layers (layers) of the ink form roller. Also, the criteria for determining the results are as follows.

X: The ink pool falls within 30 minutes after starting printing.

Δ: The ink puddle may fall within the same 60 minutes.

○: Slight growth of ink pool is observed within 1 to 2 hours, but it does not lead to falling.

◎: The ink pool does not grow even after the same time period has passed.

Note that the number of sheets printed corresponding to a printing time of 30 minutes by the inking device used in the comparative example and the example of the present application was approximately 2,300 sheets.

(Left below) As is clear from the table above, 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 clearance angle θ is 90°, and the radius of curvature r is 20 μm or less. It can be seen that if 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, if the radius of curvature r of the thin plate member 181 is set to 10 μm or less, the effect of preventing back sagging becomes higher;
Continuous operation for 2 hours is possible. Furthermore, the radius of curvature r is set to 5
When the thickness is set to ˜095 μm, stable printing without sagging on the back side for a long time can be achieved even with many types of ink.

(6) Reference Experimental Example In FIG. 9, the radius of curvature R of the ink introduction side front edge 181e of the doctor blade material plate member 181 is 20 um and 30 um.
Various doctor blades having a diameter of 50 μm, 75 μm, and 100 μm were prepared, and printing was carried out with all other conditions set the same as in Experimental Example 1 of the present application described using FIG.

FIG. 13 shows the density index obtained by measuring the density of the solid portion of the printed matter printed under the above conditions using a reflection densitometer (Bretag densitometer) using a blue two-filter.

As shown in FIG. 1, the pushing amount ΔP(,w) of the doctor blade, which is an index on the horizontal axis in FIG. It represents the distance that the ink form roller 12 has moved in the approximate radial direction (in other words, the distance that it has been pushed). The value of the pushing amount Δρ may be appropriately selected depending on the dimensions and physical properties of the ink forming roller 12, the usage conditions of the ink 26, etc., but in this experimental example, it was set to 0°2 to 0.5 Irwn. Pushing amount Δp is 0.2m
If the pushing amount Δp exceeds 0.5 mm, the ink film thickness tends to become unstable due to the influence of variations in the precision and assembly precision of each component that makes up the inking device.On the other hand, if the pushing amount Δp exceeds 0.5 mm, This is because not only the driving energy becomes excessive, but also problems such as heating of the ink forming roller 12 occur.

As is clear from Fig. 13, the curvature of each half is 3.
8 - It can be seen that the larger the value of R is, the darker the edge damage during pushing with respect to the diameter R is, and the smaller the value of R is, the lighter the edge is. In this experiment, the solid density on printed matter using high-quality paper as the printing material fell within a range showing a standard density index of 1.0 to 1.4, and the pushing amount Δp ranged from 0.2 to 1.4. The radius of curvature R, which shows a curve that can realize almost the entire region specified by the range of 0.5#, was 50 μm and 75 μm. radius of curvature R
When R is 30 μm, the printing density becomes lighter over the entire area, making it difficult to obtain a high density. Conversely, when the radius of curvature R is 100 μm, the printing density becomes darker over the entire area, making it difficult to obtain a low density. However, in printing that accepts these tendencies, even a case where the radius of curvature R is 30 μm or 100 μm can be used satisfactorily. On the other hand, when the radius of curvature R was 20 LITrL, 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, the present invention can be widely applied to an inking device for general printing presses such as letterpress printing and lithographic printing. It can also be widely applied to a so-called coating device that forms a shape.

<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 made of a material having substantially no flexibility in the tangential direction of the outer peripheral surface of the coating roller. The front edge of the thin plate member on the ink outlet side at the tip thereof is bent to have a radius of curvature of 20 μm.
Since the settings are as follows, it is possible to prevent the coating liquid from dripping from the doctor blade even after long-term operation.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of essential parts of an inking device according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view of an offset printing press equipped with the above-mentioned inking device, and FIG. 3 is a schematic cross-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, Fig. 10 is an explanatory diagram when the thickness of the doctor blade thin plate member is set large, and Fig. 11 is an explanatory diagram of the doctor blade thin plate member. FIG. 12 is an explanatory diagram of Example 2 of the present application, FIG. 13 is a characteristic diagram showing the relationship between the doctor blade pushing amount and the Bretag anti-tA concentration meter index, and FIG. 14 is an explanatory diagram when the plate thickness is set small. FIG. 15 is a sectional view of another conventional example. 12... Ink @ number propeller 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 Swamp 1 11"1 N □Tsu 10□ Fig. 11(b) (a) Fig. 12

Claims (3)

[Claims] (1) A coating roller having an elastic surface, and a doctor blade that is arranged to be able to move back and forth in the approximate radial direction of the coating roller with respect to the outer circumferential surface of the coating roller and adjust the thickness of the coating film formed on the roller outer circumferential surface. In the coating device, the doctor blade includes 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 inflexible in a tangential direction to the outer circumferential surface of the coating roller. 1. A coating device comprising: a holding member for holding the thin plate member in a state in which the thin plate member has a front edge on the ink outlet side at the tip end thereof curved to have a radius of curvature of 20 μm or less. (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.