JP3585587B2 - Plate cylinder of stencil printing machine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plate cylinder of a stencil printing machine.
[0002]
[Prior art]
Prior art 1.
The stencil printing machine performs perforation and stencil making on the stencil paper by the heating element of the thermal head, conveys the stencil paper and winds it around the outer peripheral surface of the plate cylinder, and supplies ink from the inner peripheral surface of the plate cylinder by ink supply means. Then, the paper is continuously pressed against the stencil sheet by a pressing means such as a press roller, and the ink is exuded from the inner peripheral surface of the plate cylinder to the outer peripheral surface and the ink from the perforated portion of the stencil paper to perform printing.
[0003]
The plate cylinder of such a stencil printing apparatus has a cylindrical support in which a number of openings for passing ink from the inner peripheral surface are formed, and an ink is wound around the outer peripheral surface of the support, and the ink is applied to the stencil sheet. And a mesh screen extending to the Japanese paper layer.
[0004]
Conventional technology 2.
Japanese Patent Publication No. 63-59393 discloses that a plate cylinder is composed of a support cylinder having a large number of holes from the inside, an intermediate screen layer, and an outer surface screen layer which comes into contact with the stencil paper. A technique has been introduced in which the mesh value is gradually increased from the screen layer to the outer surface screen layer to reduce the flow path of the ink to prevent set-off.
[0005]
The outermost screen layer, which is the outermost layer of such a printing cylinder, is generally about 300 mesh (pitch = about 85 μm) and has a wire diameter of about 40 μm, and the size of the opening through which ink passes is limited. It is about 45 μm square.
[0006]
Prior art 3.
Japanese Utility Model Publication No. 59-229 discloses that a plate cylinder is made up of a rigid cylindrical body having a large number of holes from the inside, a synthetic resin layer of an open-cell structure, and a woven fabric to prevent printing unevenness. Technology is introduced. In this synthetic resin layer, a thin partition wall formed by foaming a resin is formed.
[0007]
Conventional technology 4.
The present application discloses a technology in which a plate cylinder is formed from a support having an opening formed therein from the inside thereof and a porous sheet wound around the outer peripheral surface of the support, thereby reducing the amount of ink transferred to the paper. It has been proposed by the same applicant as the applicant (Japanese Patent Application No. 7-96952). In this porous sheet, an ink passage is formed such that the ink that has flowed in from the hole on the ink inflow side shifts at least once with respect to one perpendicular line that has fallen on the support and flows out from the hole on the ink outflow side. ing.
[0008]
[Problems to be solved by the invention]
In the prior art 1, when printing is performed continuously, the ink sucked from the support is absorbed by the stencil sheet into the paper before the ink is sufficiently diffused by the screen. There is a problem that the resulting image density unevenness can occur. In addition, when the average ink adhesion amount is increased to raise the solid image density to a certain level, at the peak of the image density, the ink is excessively supplied, and the dry ink stains the back surface of the next sheet. There is also a problem that transfer occurs.
[0009]
In the prior art 2, since the opening of the outermost mesh screen is formed to have substantially the same size as the perforations formed in the stencil paper, there is no effect of restricting the flow of ink, and set-off is almost prevented. There is a problem that can not be.
[0010]
In the prior art 3, since the synthetic resin layer is disposed on the cylindrical body having the rigid structure, the synthetic resin layer is deformed and crushed by repeated pressure from the press roller during printing. This collapse is due to permanent compression strain, and is a characteristic that is almost impossible to recover. Therefore, prior art 3 has a problem that the life of the plate cylinder is short.
[0011]
In the prior art 4, the ink passage of the porous sheet is such that the ink that has flowed in from the hole on the ink inflow side shifts at least once with respect to one perpendicular line lowered to the support and flows out from the hole on the ink outflow side. Therefore, there is a problem that the ink is not sufficiently diffused and density unevenness occurs in the image.
[0012]
Accordingly, the present invention has been made in order to solve the above-described problems, and it is an object of the present invention to provide a plate cylinder of a stencil printing apparatus capable of obtaining an image without density unevenness and without set-off. I do.
[0013]
[Means for Solving the Problems]
According to the first aspect of the present invention, in the plate cylinder of the stencil printing apparatus in which stencil paper is wound on the outer peripheral surface, ink is supplied from the inner peripheral surface, and rotates in a fixed direction, a large number of openings for passing the ink are formed. And a diffusion layer made of a non-woven fabric having fibers having a fiber diameter of 100 μm or less, having holes of non-uniform shape and spacing arranged on the outer peripheral surface of the support, and diffusing the ink. A screen disposed outside the diffusion layer, wherein the average diameter and spacing of the holes in the diffusion layer are smaller than that of the opening and smaller than that of the screen .
[0014]
According to a second aspect of the present invention, in the plate cylinder of the stencil printing apparatus according to the first aspect, a porous resin layer is provided so as to overlap the diffusion layer.
[0015]
According to a third aspect of the present invention, in the plate cylinder of the stencil printing apparatus according to the second aspect , the resin layer is disposed so as to be in contact with the screen .
[0016]
According to a fourth aspect of the present invention, in the plate cylinder of the stencil printing apparatus according to the second or third aspect , the resin layer has heat shrinkability.
[0017]
According to a fifth aspect of the present invention, in the plate cylinder of the stencil printing machine according to the first, second, third or fourth aspect , the aperture ratio o (%) of the diffusion layer and the thickness t (μm) have the following relationship. It is characterized by being in a region that satisfies .
[0018]
20 ≦ o ≦ 80, and 0 <t ≦ 300, and 0 <t ≦ 50 + 5 × o
[0024]
【Example】
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a plate cylinder. As shown in FIGS. 1 and 2, the plate cylinder 1 is disposed on a cylindrical support 21, a diffusion layer 22 for diffusing ink, and a diffusion layer 22 for diffusing ink. Screen 23, and a screen 24 further disposed outside the screen 23. The plate cylinder 1 is rotatably supported around a central axis 5 also serving as an ink pipe described later, and is rotated in a fixed direction by a motor.
[0025]
The support 21 is formed of stainless steel in a cylindrical shape, the thickness thereof is set to 0.2 mm, and has a clamp means 31 for clamping the leading end of the stencil sheet 8 on the outer peripheral surface. The support body 21 is provided with a large number of openings 21a for allowing ink to pass therethrough, except for the clamp means 31 and its peripheral part and both side edges. The diameter of the opening 21a is set to 0.25 mm, and the pitch is set to 1.2 mm.
[0026]
The diffusion layer 22 is formed by pressurizing and heating particles of synthetic resin, for example, particles of polymer polyethylene (having a diameter of several tens of μm), and the surface is shown in FIG. 3A and the cross section is shown in FIG. 3B. Has an open cell structure. In the diffusion layer 22, holes having an uneven shape and an interval of 10 to several tens μm are formed. As described above, by taking the synthetic resin particles under pressure and heat to form an open-cell structure, compared to the case where the open-cell structure is formed by foaming, the resin is much stronger against external force and the durability is increased.
[0027]
The inventor conducted an experiment in which the aperture ratio o and the thickness t of the diffusion layer 22 were changed to obtain a range in which a good image could be obtained. Using a VT3820 Ricoh test device, the pressing force of the press roller 16 was increased or decreased by about 50% from the standard 12 kgf, and the diameter and pitch of the opening 21a of the support 21 were also increased or decreased by about 50%. The aperture ratio o was changed. The result is shown in FIG.
[0028]
In a region X where the aperture ratio o (%) and the thickness t (μm) satisfy the relationship of 20 ≦ o ≦ 80, 0 <t ≦ 300, and 0 <t ≦ 50 + 5 × o, a good image is obtained. Obtained. In the region Y where the opening ratio o is smaller than 20% and the thickness t is thicker, the amount of ink attached is small, the image density is low, and it takes time to start up. On the other hand, in the region Z where the opening ratio o is 80% or more, Image density unevenness occurred.
[0029]
Therefore, the thickness of the diffusion layer 22 is preferably 300 μm or less, and preferably 50 μm or less from the stand-up speed of the device. Of course, the preferred thickness varies depending on the ink used and the like, but in this example, a W / O emulsion ink VT-II manufactured by Ricoh Co., Ltd. was used.
[0030]
The screens 23 and 24 are formed in a mesh shape by using a metal or a foamed resin. The mesh value of the screen 23 is set to 355 mesh, and the mesh value of the screen 24 is set to 300 mesh. In addition, as the screens 23 and 24, a screen made of a nonwoven fabric or the like may be used in addition to the mesh screen.
[0031]
If the hole diameter and the interval of the diffusion layer 22 are larger than those of the opening 21a, the ink passes through the diffusion layer 22 or the diffusion layer 22 has an uneven shape and irregular intervals, so that the ink is not diffused. If the value of the distance between the holes of the diffusion layer 22 and the value of the distance between the openings of the screen 23 are too close, moire, which is an interference phenomenon, appears, and the unevenness of the image density is rather increased. Further, when the hole diameter and the interval of the diffusion layer 22 are larger than the opening diameter and the interval of the screen 23, the effect of suppressing the rapid movement of the ink is inferior to that of the screen 23, and the excessive movement of the ink from the opening 21 a of the support 21. Can not be prevented enough. Therefore, the average diameter of the holes in the diffusion layer 22 is set to 30 μm and the aperture ratio is set to 30%, and is smaller than the opening diameter and interval of the openings 21 a and smaller than that of the screen 23.
[0032]
The clamp means 31 is provided on a stage 6 made of a magnetic material provided along the generatrix on the outer peripheral surface of the support body 21 and at a portion opposed to the stage 6 and is rotatably supported by a clamper shaft 7a. 6 and a clamper 7 having a magnet attached to a surface facing the same.
[0033]
Inside the plate cylinder 1, an ink roller 2 for supplying ink to the inner peripheral surface of the support 21 and an ink pool 4 are formed between the ink roller 2 and the ink roller 2 with a slight gap therebetween. A doctor roller 3 and a central shaft 5 for supplying ink to the ink reservoir 4 are arranged. The ink is pressure-fed from an ink pack disposed at an appropriate position by an ink pump, and is supplied to the ink reservoir 4 through a supply hole 5 a of the central shaft 5.
[0034]
A press roller 16 for pressing a sheet 15 against the plate cylinder 1 and a paper sheet between the outer peripheral surface of the plate cylinder 1 and the press roller 16 at a predetermined timing are provided in the vicinity of the lower portion of the outer peripheral surface of the plate cylinder 1 facing the ink roller 2. A pair of registration rollers 14 for feeding the sheet 15 are disposed.
[0035]
The operation of the stencil printing apparatus configured as described above will be briefly described.
In FIG. 1, a stencil sheet 8 having been made a stencil has its leading end sandwiched between a stage 6 and a clamper 7, and is wound around the outer peripheral surface of a plate cylinder 1. In this state, the plate cylinder 1 is rotated in the fixed direction, and one sheet of paper 15 is fed to the registration roller pair 14, and the screen 24 is rotated by the registration roller pair 14 at a predetermined timing synchronized with the rotation of the plate cylinder 1. A sheet 15 is inserted between the stencil sheet 8 wound around the outer peripheral surface of the sheet and the press roller 16.
[0036]
At this time, the ink roller 2 also rotates in the same direction as the rotation direction of the plate cylinder 1. The ink in the ink reservoir 4 is attached to the surface of the ink roller 2 by the rotation of the ink roller 2, and the amount thereof is regulated when passing through the gap between the ink roller 2 and the doctor roller 3. Supplied to
[0037]
The ink supplied to the inner peripheral surface of the support 21 is supplied to the opening 21a by the further rotation of the ink roller 2 as shown in FIG. 2, and diffuses from the opening 21a as shown by the arrow in FIG. Diffusion into the layer 22 is performed in the circumferential direction of the diffusion layer 22 by holes having uneven shapes and intervals. Further, the ink passes through the screen 23 and the screen 24 and is supplied to the surface where the stencil sheet 8 and the screen 24 come into contact.
[0038]
The press roller 16 that has been separated from the outer peripheral surface of the plate cylinder 1 moves upward, and the paper 15 is pressed against the stencil sheet 8 wound around the outer peripheral surface of the screen 24 of the rotating plate cylinder 1, thereby forming a stencil. From the perforations in the base paper 8, the ink is transferred to the surface of the paper 15 and printed.
[0039]
According to this example, the high viscosity resistance of the ink and the fact that the holes of the diffusion layer 22 have an uneven shape and spacing are combined, so that a large pressing force is instantaneously applied to the plate cylinder 1 by the press roller 16 during printing. Even if it is applied, the ink is not rapidly pushed out of the plate cylinder 1, so that the image density unevenness caused by the opening 21 a of the support 21 can be suppressed. The viscous resistance of the ink does not become a large resistance to a slow ink flow, but is a level at which the supply amount of the ink is slightly reduced. Even if the supply amount of ink decreases, the decrease in supply amount of ink can be recovered by adjusting the printing conditions, for example, by increasing the pressing force of the press roller 16 and adjusting the opening 21a.
[0040]
Next, the inventor performs printing using the plate cylinder 1 provided with the diffusion layer 22 and the plate cylinder without the diffusion layer (hereinafter, referred to as a conventional plate cylinder), and the position on the paper 15 and the ink absorption of the paper 15. The relationship with quantity was investigated. The result is shown in FIG. The curve α represents the case of the plate cylinder 1, and the curve β represents the case of the conventional plate cylinder. As can be seen from the figure, in the conventional plate cylinder, the ink coming out of the opening did not diffuse to the peripheral surface of the plate cylinder, and the ink absorption amount of the paper in the opening corresponding portion was excessive. In the case of the plate cylinder 1, the unevenness of the ink absorption amount of the paper 15 was reduced.
[0041]
The inventor further prints using the plate cylinder 1 and the conventional plate cylinder, examines the relationship between the set-off rank and the ink absorption amount of the paper 15, and shows the results in a graph shown in FIG. expressed. Point α1 is for the plate cylinder 1 and point β1 is for the conventional plate cylinder. The period from the point α1 to the point β1 indicates a decrease in the peak of the ink absorption amount due to the addition of the diffusion layer 22. As shown in the figure, when the diffusion layer 22 is provided, the peak of the unevenness of the image density is suppressed, and the absorption of excess ink by the paper 15 at the peak is reduced, and the set-off is eliminated.
[0042]
The inventor further performed printing using the plate cylinder 1 and a conventional plate cylinder, and examined the relationship between the image density and the ink absorption amount of the paper 15. The results are shown in FIGS. 7a and 7b.
[0043]
7A shows the case of the conventional plate cylinder, FIG. 7B shows the case of the plate cylinder 1, and shows the density unevenness of the image between points AA ′, and the point A1 shows the average image density (measured value). , Points BB ′ represent uneven image density, and point B1 represents an average image density (measured value). As can be seen from the figure, since the image density unevenness is reduced, if the average ink absorption amount is the same, the image density of the portion corresponding to the uneven valley (non-opening corresponding portion) increases, and the average image density increases. . Further, the synergistic effect of increasing the image density and reducing the unevenness of the image density improves the uniformity of the entire image, so that a moist and calm image can be obtained.
[0044]
FIG. 8 shows a second embodiment of the present invention. This embodiment is different from the above-described first embodiment only in that the diffusion layer 33 is formed from a porous resin layer 32b and Japanese paper 32a.
[0045]
The diffusion layer 33 is formed by attaching a 50 μm thick Japanese paper 32 a to a resin layer 32 b made of, for example, a heat-shrinkable polyethylene terephthalate film having a thickness of 2 μm, and piercing the resin layer 32 b with a 400 dpi thermal writing head. It is formed. A known material may be laminated on the surface of the resin layer 32b to protect the thermal writing head. The diameter and interval of the perforations are set smaller than that of the opening 21a and smaller than that of the screen 23. As described above, when the resin layer 32b is thermally contracted, various desired perforation patterns can be easily formed by perforating with the thermal writing head. FIG. 9a shows the Japanese paper 32a of the diffusion layer 33, and FIG. 9b shows the perforated resin layer 32b. This resin layer 32b is a support for the Japanese paper 32a.
[0046]
The perforations in the resin layer 32b provide resistance to the passage of ink, and diffuse the ink in the circumferential direction of the diffusion layer 33. Also, a nonwoven fabric in which fibers are randomly entangled may be used instead of the Japanese paper 32a.
[0047]
The diffusion layer 33 also has an aperture ratio o (%) and a thickness t (μm) of 20 ≦ o ≦ 80, 0 <t ≦ 300, and 0 <t ≦ 300, similarly to the diffusion layer 22 of the above-described embodiment. It is formed so as to satisfy the relationship of 0 <t ≦ 50 + 5 × o.
[0048]
Although the nonwoven fabric and the Japanese paper 32a are very thin, the movement of the ink along the fiber and the amount of the ink attached to the fiber surface are large due to the long fiber and the interfacial tension of the ink. Works well. Of course, the resin layer 32b may be omitted, and only the Japanese paper 32a or only the non-woven fabric may be used.
[0049]
If the diameter of the fiber of the Japanese paper 32a is large, the mesh of the screen 23 is continuously closed, and the supply amount of the ink becomes uneven, and a white spot-like abnormality appears in the image. Therefore, the diameter of the fiber of the Japanese paper 32a is 100 μm. It is set as follows.
[0050]
The diffusion layer 33 is disposed such that the resin layer 33b is in contact with the screen 23. By arranging the resin layer 32b in this way, the unevenness of the image density is further reduced. However, as described above, the resin layer 32b having a perforation smaller than the mesh of the screen 23 is provided outside the Japanese paper 32a. Therefore, it is considered that the ink is stored in the Japanese paper 32a and diffused. On the other hand, when the Japanese paper 32a is disposed so as to be in contact with the screen 23, the ink of the Japanese paper 32a is easily moved to the screen 23, and the effect of ink diffusion and ink regulation is slightly reduced in an image.
[0051]
【The invention's effect】
In the present invention, the ink supplied from the inner peripheral surface of the support passes through the opening of the support, is diffused in the circumferential direction by the diffusion layer disposed on the outer peripheral surface of the support, and is disposed outside the diffusion layer. Moving from the screen to the stencil sheet, the unevenness of ink absorption is reduced, the peak of uneven image density is suppressed, the excess ink is absorbed by the paper at the peak is reduced, and the set-off is improved. .
[Brief description of the drawings]
FIG. 1 is a sectional view of a stencil printing machine to which a plate cylinder according to a first embodiment of the present invention is applied.
FIG. 2 is a partially enlarged sectional view of a plate cylinder of the stencil printing machine shown in FIG.
3A is a micrograph of the surface of the diffusion layer shown in FIG. 2, and FIG. 3B is a micrograph of a cross section of the diffusion layer.
FIG. 4 is a graph showing a relationship between a thickness of a diffusion layer and an aperture ratio.
FIG. 5 is a graph showing a relationship between an ink absorption amount of a sheet and a position on the sheet.
FIG. 6 is a graph showing a relationship between a set-off rank and an ink absorption amount of a sheet.
FIG. 7A is a graph showing the relationship between image density and the amount of ink absorbed by a sheet when a conventional plate cylinder is used, and FIG. 7B is a graph showing image density and ink absorption by a sheet when a plate cylinder having a diffusion layer is used. It is a graph which shows the relationship with quantity.
FIG. 8 is a partial sectional view of a plate cylinder showing a second embodiment of the present invention.
9A is a photomicrograph of Japanese paper of the diffusion layer shown in FIG. 8, and FIG. 9B is a photomicrograph of a resin layer of the diffusion layer shown in FIG.
[Explanation of symbols]
Reference Signs List 1 plate cylinder 2 ink roller 3 doctor roller 5 center shaft 6 stage 7 clamper 8 stencil sheet 14 registration roller pair 15 paper 16 press roller 21 supports 22, 32 diffusion layers 23, 24 screen 31 clamp means 21a opening

Claims (5)

In the plate cylinder of the stencil printing apparatus, the stencil paper is wound on the outer peripheral surface, the ink is supplied from the inner peripheral surface, and the stencil printing machine rotates in a fixed direction.
A support having a large number of openings through which the ink passes,
A diffusion layer made of a nonwoven fabric having fibers with a fiber diameter of 100 μm or less, having holes of non-uniform shape and intervals arranged on the outer peripheral surface of the support, and diffusing the ink;
A screen arranged outside the diffusion layer,
The plate cylinder of a stencil printing machine, wherein the average diameter and spacing of the holes in the diffusion layer are smaller than that of the openings and smaller than that of the screen . The plate cylinder of the stencil printing machine according to claim 1 ,
A plate cylinder of a stencil printing machine, wherein a porous resin layer is provided on the diffusion layer. The plate cylinder of the stencil printing machine according to claim 2 ,
A plate cylinder of a stencil printing machine, wherein the resin layer is arranged so as to be in contact with the screen . The plate cylinder of the stencil printing apparatus according to claim 2 or 3 ,
A plate cylinder of a stencil printing machine, wherein the resin layer has heat shrinkability. The plate cylinder of the stencil printing apparatus according to claim 1, 2, 3, or 4 ,
A plate cylinder of a stencil printing machine, wherein the aperture ratio o (%) and the thickness t (μm) of the diffusion layer are in a region satisfying the following relationship.
20 ≦ o ≦ 80, and 0 <t ≦ 300, and 0 <t ≦ 50 + 5 × o

Images