JPH0858215A - Screen printing machine - Google Patents

Abstract

PURPOSE: To provide an inexpensive novel screen printing machine capable of obtaining a sharp printing image free from strike-through and fiber patterns and not wasting ink. CONSTITUTION: A master 8 composed of a thermoplastic resin film is perforated under heating by a thermal head 10 being a plate making means and wound around the outer peripheral surface of a plate cylinder 1 rotated around its rotary shaft 5 and ink is supplied to the perforated master from the inner peripheral surface of the plate cylinder 1 and printing paper 15 is pressed to the master 8 to bleed the ink from the perforations of the master to perform printing. In the screen printing machine, the outer peripheral surface of the plate cylinder 1 is formed from a mesh screen 23 having perforations smaller than those of the master.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stencil printing machine for printing by wrapping a master made of only a thermoplastic resin film perforated by a plate making means on a plate cylinder for printing.

[0002]

2. Description of the Related Art A stencil printing machine punches a master for heat-sensitive stencil by a heating element of a thermal head, and conveys the master to a porous support and a resin or metal mesh screen. It is wound around the outer peripheral surface of a cylindrical plate cylinder, and ink is supplied from the inner peripheral surface of the plate cylinder by an ink supply member, and the printing paper is continuously pressed against the master by pressing means such as a press roller, Printing is performed by allowing the ink to seep through the apertures of the plate cylinder, the mesh screen, and the perforations of the master.

As a plate cylinder of such a stencil printing machine,
As shown in Japanese Examined Patent Publication No. 63-59393,
It is well known that a plurality of mesh screens are wound around a porous support. The outermost mesh screen of this plate cylinder has a 250 mesh value (pitch = about 100 μm).
m), the wire diameter is about 40 μm, and the size of the opening through which the ink passes is about 60 to 70 μm square.

The heating element is set to a size of about 45 to 60 μm square and arranged at 400 dpi.
The size of the perforation formed in the master by the heating element is formed to be substantially the same as the size of the heating element.

The above-mentioned master is a laminated structure in which a very thin thermoplastic resin film of polyester or the like is laminated with synthetic fibers or Japanese paper as a porous and flexible support, or a mixture of Japanese paper and synthetic fibers. Has become.

The ink used in the stencil printing machine is
Generally used are oil-based inks that are difficult to evaporate or water-in-oil type (water is surrounded by oil) type emulsion inks. This is because if the stencil printing machine is left unused for a long time and printing is restarted, the ink on the plate cylinder support or mesh screen may evaporate or the ink may be absorbed by the master support. This is because the amount is reduced, and thereby a large amount of waste paper is not generated in order to obtain a good printed image.

[0007]

In the above-mentioned stencil printing machine, since Japanese paper or the like is used as the support of the master, the passage of the ink is obstructed at the portion where the fibers of the Japanese paper are entangled, and the ink is transferred to the printing paper. Instead, a fiber pattern appears on the solid part, or fine lines or the like are faintly generated, which is a so-called fiber grain defect. Also, if you release the used master,
There is a problem that the ink filled in the used master support is discarded and the ink is wasted.

In the stencil printing machine, as shown in FIG. 4, the ink 19 is applied to the opening 27a of the mesh screen 27 of the outermost layer of the plate cylinder, the support 28d of the master 28 and the film 2.
Printing is performed by allowing the surface of the printing paper 25 to exude into a swelled state (large amount) through the perforations 28c of 8a. Reference numeral 28b represents the fibers of the support 28d.

Therefore, when an oil-based ink that is hard to evaporate is used, the transferred ink penetrates into the inside of the printing paper, and it takes time for the transferred ink to be in a sufficiently dried state, and continuous printing is performed. In addition, if the next printing paper is ejected and stacked before the ink of the previous printing paper is dried, the ink of the previous printing paper will be transferred to the back side of the next printing paper, and a problem called offset will occur. . This set-off is particularly likely to occur in a solid portion having a large ink transfer amount.

Therefore, attempts have been made to reduce the fiber grain by thinning or completely eliminating the support of the master, which is the source of the fiber grain, and to reduce the waste ink.

However, since the opening of the mesh screen of the outermost layer of the conventional plate cylinder is formed to have substantially the same size as the size of the perforations formed in the master, the amount of ink transferred to the printing paper is reduced, and The effect of preventing the transfer could hardly be expected. Furthermore, when the master support is removed, the master directly contacts the mesh screen of the plate cylinder, so the master comes into contact with the convex portions of the mesh of the mesh screen and is abraded by friction when pressing the printing paper during printing. There is a problem in that the holes are opened and the printing paper becomes dirty. Further, if the opening of the mesh screen is made small, there is a problem that the manufacturing cost of the mesh screen becomes high.

Therefore, the present invention has been made in order to solve the above-mentioned problems, and it is possible to obtain a clear printed image without set-off and no fiber, and at the same time, at a low cost and without waste of ink. An object of the present invention is to provide a stencil printer.

[0013]

According to a first aspect of the present invention, a master made of a thermoplastic resin film is heat-punched by a plate making means and wound around an outer peripheral surface of a plate cylinder rotating around a rotation center axis. , In the stencil printing apparatus that supplies ink from the inner peripheral surface of the plate cylinder, presses the printing paper against the master to exude ink from the perforations of the master for printing, and the outer peripheral surface of the plate cylinder is more than the perforation. It is characterized in that it is formed of a mesh screen having a small opening.

According to a second aspect of the present invention, in the stencil printing apparatus according to the first aspect, at least a surface of the mesh screen that comes into contact with the master is smoothed and its thickness is made uniform. To do.

[0015]

In the invention according to claim 1, since the opening of the mesh screen is made smaller than the perforation of the master,
The amount of ink that oozes out from the openings of the mesh screen and the perforations of the master is reduced to a small amount, and is transferred to the printing paper.

According to the second aspect of the present invention, since the master is wound around the mesh screen having a smoothed surface in contact with the master and a uniform thickness, the contact area between the mesh screen and the master becomes large. Wear of the master due to printing paper is reduced.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 is a plate cylinder, reference numeral 30 is a plate making apparatus, and reference numeral 40 is an ink supply apparatus.

As shown in FIGS. 1 and 3, the plate cylinder 1 has a porous cylindrical support layer 21 forming an inner peripheral surface and an ink holding member wound around the outer peripheral surface of the support layer 21. It has a three-layer structure of a layer 22 and a mesh screen 23 forming the outer peripheral surface of the plate cylinder 1. The plate cylinder 1 is rotatably supported around a rotation center shaft 5 which also serves as an ink pipe, which will be described later.
It is rotated by a motor (not shown).

The support layer 21 is formed of a metal such as stainless steel in a cylindrical shape, and has a clamp means 31 for clamping the tip portion of the master 8 made of only a thermoplastic resin film on the outer peripheral surface thereof. The support layer 21 is provided with a large number of openings 21a for allowing ink to pass therethrough except for the clamping means 31 and its peripheral portion and both side edge portions.

The ink holding layer 22 is formed of a metal mesh mesh screen or foamed resin, and holds and passes ink. In this example, the ink holding layer 2
Although only one layer 2 is provided, a plurality of layers may be provided.

As shown in FIG. 2, the mesh screen 23 is provided with a square opening 23a for allowing ink to pass therethrough similarly to the above-mentioned support layer 21. The length of one side A of the opening 23a is smaller than that of the perforations 8c formed in the master 8 by the plate making apparatus 30 described later.
It is set to 5 μm. Also, the mesh screen 2
The wire diameter C of 3 is set to 5 μm.

The mesh screen 23 has an opening 23a formed by etching a thin plate material having a uniform thickness and at least one surface of which is smooth, for example, a copper plate or a stainless plate.
Is formed and is wound around the outer peripheral surface of the ink holding layer 22 with the smooth surface facing outward. Further, as the mesh screen 23, a thin plate material having an opening 23 a and having a uniform thickness and at least one surface of which is smooth may be produced by electroforming, and this may be used for the mesh screen 23.

A suitable thickness of the plate material is about several μm to 30 μm, but it is preferable that the thickness is as thin as possible within a range in which there is no extreme decrease in strength. Thus, when the opening 23a is formed by etching or electroforming, the mesh screen 23
Will reduce the manufacturing cost.

In this example, the shape of the opening 23a is square, but it may be circular, hexagonal or polygonal.

The clamp means 31 is a stage 6 made of a magnetic material and provided along the generatrix of the outer peripheral surface of the support layer 21.
The clamper 7 is disposed at a portion facing the stage 6, is rotatably supported by the clamper shaft 7a, and has a magnet attached to the surface facing the stage 6.

Inside the plate cylinder 1, an ink roller 2 for supplying ink to the inner peripheral surface of the support layer 21, and an ink roller 2
The ink roller 2 is arranged in parallel with a slight gap between
A doctor roller 3 that forms an ink reservoir 4 between
A rotation center shaft 5 for supplying ink to the ink reservoir 4 is arranged. The ink roller 2 and the doctor roller 3 are rotatably supported by side plates (not shown) fixed to the rotation center shaft 5.

The ink is pressure-fed by an ink pump from an ink pack arranged at an appropriate position, and the rotation center shaft 5
The ink is supplied to the ink reservoir 4 through the supply hole 5a. here,
The ink roller 2, the doctor roller 3, and the rotation center shaft 5 form an ink supply device 40.

A press roller 16 for pressing the printing paper 15 against the plate cylinder 1 is provided in the lower vicinity of the outer peripheral surface of the plate cylinder 1 facing the ink roller 2, and an outer peripheral surface of the plate cylinder 1 and the press roller 16 are provided.
A pair of registration rollers 14 that feed the printing paper 15 at a predetermined timing are provided between the registration roller 14 and the registration roller 14.

The plate making apparatus 30 is composed of a thermoplastic resin film, and has a master supporting means 8a for supporting the master 8 wound in a roll shape on a roll core 8b so that the master 8 can be paid out.
A platen roller 9 for transporting the platen, a thermal head 10 as a plate making means provided so as to be able to come into contact with and separate from the platen roller 9, and a pair of transport rollers 11 provided downstream of the platen roller 9 for transporting the master 8. Conveyor roller pair 11
A pair of upper and lower cutter members 12a and 12b provided on the downstream side of the master 8 for cutting the master 8 and the clamp means 31 for clamping the master 8.
It is mainly composed of a guide plate 13 for guiding toward.

The platen roller 9 has its shaft rotatably supported and is rotationally driven at a predetermined peripheral speed by a stepping motor (not shown) to convey the master 8 while pressing it against the thermal head 10.

The thermal head 10 has a plurality of heating elements arranged in a row in the width direction of the master 8, and is provided so as to be able to come in contact with and separate from the platen roller 9 by a well-known contact-separation mechanism (not shown). . The heating element is 50 μm
It is set to the size of the corner and arranged at 400 dpi. The thermal head 10 selectively heats and punches the master 8 based on a digital image signal which is processed and sent by an A / D conversion unit and a plate making control unit of a document reading unit which reads a document (not shown) to form a punched image. Have a function.

The perforations 8c formed in the master 8 by the thermal head 10 are substantially square as shown in FIG. 2, and the energy applied to the thermal head 10 is set so that the length B of one side thereof is about 50 μm. Has been done.

The conveying roller pair 11 is rotationally driven through a torque limiter by a stepping motor that rotationally drives the platen roller 9, and its peripheral speed is set to be slightly higher than the peripheral speed of the platen roller 9. . This helps to prevent the master 8 from wrinkling by applying a predetermined tension to the master 8 between the platen roller 9 and the conveying roller pair 11.

Thermal head 10, platen roller 9,
The width of the transport roller pair 11 is set to be at least the same as the width of the master 8.

The operation of the stencil printing machine configured as described above will be described. When a document is set on the document reading unit and the start button is pressed, the plate cylinder 1 rotates, and the used master is separated from the outer peripheral surface of the plate cylinder 1 by a plate discharge device (not shown) and discarded. After that, plate cylinder 1
1, as shown in FIG. 1, the clamp means 31 is stopped at a predetermined position substantially right above, and the clamper shaft 7a is rotated by the opening / closing means (not shown) of the clamper 7 to open the clamper 7 and wait for plate feeding. It becomes a state.

By driving a stepping motor (not shown), the platen roller 9 starts to rotate, and the master 8 is conveyed while being fed out from the master supporting means 8a.

On the other hand, the heating element of the thermal head 10 is selectively heated by the digital image signal processed and sent by the A / D converter and the plate-making controller (both not shown), and the master 8 displays an image. Depending on the information, it starts to be selectively heat-drilled.

Next, the master 8 moves to the platen roller 9,
The guide plate 13 is transported by the rotation of the transport roller pair 11.
After passing above, the leading end of the master 8 is delivered toward the clamping means 31 which is opened in the plate feeding standby state. When the number of steps of the stepping motor reaches a certain set value,
It is determined that the tip of the plate-made master 8 has reached between the clamper 7 and the stage 6, the clamper shaft 7a is rotated by an opening / closing means (not shown), the clamper 7 is closed, and the plate-made master 8 The tip is held between the stage 6 and the clamper 7.

Simultaneously with this clamping operation, the plate cylinder 1 is rotated in the clockwise direction at the same peripheral speed as the conveying roller pair 11, and the plate-made master 8 is wound on the outer peripheral surface of the mesh screen 23 of the plate cylinder 1. .

When the plate-making master 8 is wound around the mesh screen 23 of the plate cylinder 1 for a predetermined length, the plate cylinder 1, the transport roller pair 11, and the platen roller 9 stop rotating. Simultaneously with this stopping operation, the cutter members 12a, 12
The master 8 is disconnected by b. Then, the plate cylinder 1 is rotated in the clockwise direction again, and the rear end (not shown) of the cut master 8 is pulled out from the plate-making device 30.
Plated master 8 on the outer surface of the mesh screen 23
Is completely wound up.

After the plate-making master 8 is wound around the outer peripheral surface of the mesh screen 23 of the plate cylinder 1, the plate cylinder 1 is rotated in the clockwise direction, and is fed by a sheet feeding device (not shown).
A sheet of printing paper 15 is fed to the pair of registration rollers 14,
The printing paper 15 is inserted between the press roller 16 and the plate-making master 8 wound around the outer peripheral surface of the mesh screen 23 at a predetermined timing synchronized with the rotation of the plate cylinder 1 by the registration roller pair 14.

At this time, the ink roller 2 also rotates in the same direction as the plate cylinder 1 rotates. The ink in the ink fountain 4
The ink is attached to the surface of the ink roller 2 by the rotation of the ink roller 2, the amount of which is regulated when passing through the gap between the ink roller 2 and the doctor roller 3, and is supplied to the inner peripheral surface of the support layer 21.

The ink supplied to the inner peripheral surface of the support layer 21 is further rotated by the ink roller 2 so that the openings 21a of the support layer 21, the ink holding layer 22, and the mesh screen 2 are formed.
After passing through the opening 23a of No. 3, the master 8 and the mesh screen 23 are supplied to the contact surface.

Then, the press roller 16 separated from the outer peripheral surface of the plate cylinder 1 moves upward, and the printing paper is printed on the master plate 8 which has been preliminarily wound around the outer peripheral surface of the mesh screen 23 of the rotating plate cylinder 1. By pressing 15, the ink 18 is transferred from the perforations 8c of the plate-made master 8 to the surface of the printing paper 15 for printing as shown in FIG. Then, the printed printing paper 15 is peeled off from the outer peripheral surface of the plate cylinder 1 by a peeling claw (not shown), and is discharged to a discharge tray (not shown).
6 is separated from the plate cylinder 1 and returns to the initial state, and enters the print standby state. Next, by the same operation as the above operation, a predetermined number of prints are sequentially and continuously performed.

[0045]

According to the first aspect of the present invention, since the openings of the mesh screen are made smaller than the perforations of the master, the amount of ink that oozes out from the openings of the mesh screen and the perforations of the master is reduced. The amount of ink that has become small and transferred to printing paper is quickly dried by permeation, which significantly reduces set-off. Further, by using the master made of only the thermoplastic resin film, the amount of the ink attached to the master and discarded is reduced, and the fiber grain can be prevented.

According to the invention of claim 2, in addition to the effect obtained by the invention of claim 1, the master is wound on a mesh screen having a smoothed surface in contact with the master and a uniform thickness. Since it is mounted, the contact area between the mesh screen and the master is increased, the abrasion of the master due to the printing paper is reduced, and the damage of the master is reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a stencil printing machine showing an embodiment of the present invention.

FIG. 2 is an enlarged plan view of a mesh screen of the stencil printing apparatus shown in FIG.

FIG. 3 is a diagram illustrating the transfer of ink during printing by the stencil printing apparatus shown in FIG.

FIG. 4 is a diagram illustrating ink transfer during printing by a conventional stencil printing apparatus.

[Explanation of symbols]

 1 plate cylinder 2 ink roller 3 doctor roller 5 rotation center shaft 6 stage 7 clamper 8 master 9 platen roller 10 thermal head as plate making means 11 transport roller pair 14 registration roller pair 15 printing paper 16 press roller 21 support layer 22 ink holding layer 23 mesh screen 30 plate making device 31 clamping means

Claims (2)

[Claims] 1. A master comprising a thermoplastic resin film,
The plate is heated and perforated by the plate making means, wound around the outer peripheral surface of the plate cylinder rotating around the central axis of rotation, ink is supplied from the inner peripheral surface of the plate cylinder, and the printing paper is pressed against the master to apply the ink to the master. In the stencil printing apparatus for printing by exuding from the perforations, the outer peripheral surface of the plate cylinder is formed of a mesh screen having openings smaller than the perforations. 2. The stencil printing apparatus according to claim 1, wherein at least a surface of the mesh screen which is in contact with the master is smoothed and the thickness thereof is uniform.