JPH05345402A - Serigraph preparation device - Google Patents

Abstract

PURPOSE:To provide a serigraph preparation device which can make perforations of holes of specially accurate sizes to bore through a heat shrinkable film, using a thermal print head of the device. CONSTITUTION:A platen 11 is constituted with substrate 20 and two cylindrical members 21a and 21b furnished therewith. When heating medium 16 of a thermal head 10 is brought into contact with the platen 11 via a film 12, a space 23 is created in the platen 11, causing the film 12 to sag into the space 23, reducing the contact area with the film 12, and an accurate dotted hole (perforation) is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stencil making device for forming perforations (dot holes) in a heat-shrinkable film with a thermal print head (hereinafter referred to as a thermal head).

[0002]

2. Description of the Related Art FIG. 6A is a schematic block diagram of a stencil making apparatus using a conventional thermal head. A conventional stencil making device sends a heat-shrinkable film 1 supplied from a feed reel (not shown) between a thermal head 2 and a platen 3,
While the heat-shrinkable film 1 is conveyed while being sandwiched between the thermal head 2 and the platen 3, heat is generated based on the print data of the thermal head 2 to punch an image in the heat-shrinkable film 1. That is, the heat-shrinkable film 1 is a stretched film, has a property of returning to a state before being stretched when the temperature reaches a so-called glass transition point, and the position opened by the heat of the thermal head 2 is A hole is suddenly expanded in the center to form a dot hole (perforation) of a predetermined size. The heat generated by the thermal head 2 is in accordance with the print data as described above, and the perforations described above are sequentially formed as the heat-shrinkable film 1 moves, and the heat-shrinkable film 1 as a whole follows the print data. Dot holes are formed.

The heat-shrinkable film 1 used in the stencil making apparatus described above is as shown in FIGS. 6 (b) and 6 (c) (note that FIG. 6 (c) is shown in FIG. (b) is an AA enlarged cross-sectional view), and a porous support 4 such as a mesh, Japanese paper, or a non-woven fabric is attached to the lower surface of the film material 1 ′ with an adhesive 5. The reason why the heat-shrinkable film 1 is formed in this manner is to increase the strength of the heat-shrinkable film 1.

[0004]

However, when using the heat-shrinkable film having the porous support 4 adhered to the lower surface as described above, incomplete dot holes may be formed. FIGS. 7A and 7B are diagrams for explaining this.
Reference numeral 7 shown in FIG. 3B is a protective film formed on the lower surface of the thermal head 2, and 8 is a lubricant coated on the upper surface of the heat-shrinkable film 1.

The cause of the formation of incomplete dot holes in the heat-shrinkable film 1 is due to the adhesive 5 used for attaching the porous support 4. That is, the adhesive 5 hinders the expansion of the holes. For example, the dot hole 6 in FIG.
As shown in a, when the adhesive 5 does not exist at the position heated by the thermal head 2, the holes opened by the heat of the thermal head 2 are accurately spread to a predetermined size due to the property of the heat-shrinkable film 1 described above. One dot hole is formed. However, when the adhesive 5 is present at a position heated by the thermal head 2 like the dot hole 6b shown in the figure, the expansion of the opening is blocked by the adhesive 5 and the hole becomes an incomplete hole. When printing is performed using the heat-shrinkable film 1 in which a large number of such incomplete dot holes 6b are formed, the ink does not sufficiently pass through the perforated portions, resulting in a so-called grain-like image, and the print quality deteriorates. .. This becomes more remarkable as an image having a higher resolution is obtained, and the print quality is significantly deteriorated even at a resolution of, for example, about 200 dpi.

On the other hand, in order to solve the above problems, it has been proposed to use a heat-shrinkable film on which the porous support 4 is not attached. However, when the porous support 4 is not used, the frictional force between the film material 1 and the platen 3 becomes large. The porous support 4 also has a role of reducing the frictional force between the film material 1 and the platen 3, and when the porous support 4 is not formed on the film material 1, as shown in FIG. The problem occurs. That is, at the point P of the heat-shrinkable film 1 located immediately below the thermal head 2, when an opening is formed by the heat of the thermal head 2, a force F that expands this hole acts due to contraction, but P that contacts the platen 3 At the point ', the frictional force F in the opposite direction to the force F acts due to the pressure contact force between the heat shrinkable film 1 and the platen 3. Therefore, the holes formed in the heat-shrinkable film 1 cannot be expanded to the size of a predetermined dot hole, and as a result, incomplete holes are formed as in the case described above.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a stencil making apparatus capable of forming dot holes having an accurate size.

[0008]

In order to achieve the above object, the present invention comprises a heating head, a stretched thermoplastic film, and a platen, which are arranged in this order, and the heating head is used to perforate the thermoplastic film to prepare a printing stencil. In the stencil making device,
The dot shape in the main scanning direction of the heating head is smaller than the dot pitch of the image to be formed, and the dot shape in the sub-scanning direction is set to be smaller than the dot pitch of the image to be formed, almost similarly to the main scanning direction. The platen is provided with driving means for relatively moving the thermoplastic film, and the platen is provided with a concave groove at a position where the heating head abuts.

[0009]

EXAMPLES An example of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of the stencil making apparatus of this embodiment, and FIG. 2 is a perspective view of a platen used in the stencil making apparatus. In both figures, the stencil making device 9 includes a thermal head 10 as a heating head and a platen 1.
1. A film material 12 as a thermoplastic film. A film feed roll as a driving means for moving the film material 12 in the direction of arrow B is arranged at a position not shown. Thermal head 10 and platen 1
1 is in contact with a predetermined pressure, and the film material 12 is in the above direction by the film feed roll in the direction of the arrow B (sub scanning direction).
Sent to. The film material 12 is made of vinylidene chloride, polyester or the like, and moves between the printing surface of the thermal head 10 (the lower surface in the figure) and the platen roll 11 while receiving a predetermined pressure contact force. A dot hole forming process is performed on the surface 12.

The thermal head 10 has an aluminum base 13
And a ceramic base 14, a glaze 15, a heating element 16, and a protective film 17 are sequentially laminated. A lubricant 18 is coated on the upper surface of the film material 12. The lubricant 18 is formed by applying grease of about 1 μm, silicone oil, or the like, and reduces the friction when the lower surface of the thermal head 10 and the film material 12 rub while pressing. The heating element 16 is composed of a resistance member, and is supplied with a current according to print data output from the control circuit via an electrode (not shown). FIG. 3 is a diagram illustrating a detailed configuration of the heating element 16 provided in the thermal head 10 described above. The heating element 16 is composed of a resistance member that is long in the main scanning direction, and an electrode is connected to the heating element 16. As shown in the figure, this electrode is specifically composed of a common electrode 25 and a segment electrode 26, and the common electrode 25 and the segment electrode 26 are alternately connected to the heating element 16. The segment electrode 26 is connected to a control circuit (not shown), and a signal (current) according to print data is supplied from this control circuit. The other end of the common electrode 25 is connected to a common ground. The width L of the common electrode 25 is wider than that of the segment electrode 26, and the distance L ′ between the common electrodes 25 adjacent to each other is the diameter (diameter) of the dot hole formed in the main scanning direction. The width L ″ of the heating element 16 described above is formed so as to match the diameter of the dot hole formed in the sub-scanning direction. For example, the width L ″ is smaller than the dot pitch, and is preferably set to 60%. . It should be noted that the heating element 16 shown in FIG. 3 is arranged long in the direction perpendicular to the paper surface of FIG. 1 (main scanning direction) when corresponding to FIG. The lower surface of 10 projects.

On the other hand, the platen 11 has a structure in which two rod-shaped columnar members 21a and 21b are adhered to the upper peripheral surface of a cylindrical substrate 20 with an elastic adhesive 22. The base body 20 is made of metal or the like and is attached to the fixed shaft of the apparatus body. As shown in FIG. 2, the columnar members 21a and 21b are arranged in parallel with each other in the axial direction of the base body 20 and have a smooth peripheral surface. The heating element 16 is disposed immediately above the position where the columnar members 21a and 21b are in circumferential contact with each other. Therefore, the thermal head 10 and the columnar member 2
When the film material 12 is fed between the 1a and 21b, the film material 12 is transferred to the upper peripheral surface Pa of the cylindrical members 21a and 21b.
A space portion 23 is formed in a region surrounded by the columnar members 21 a and 21 b and the film material 12 while being in contact with Pb. According to the above-described structure, the space 23 is located directly below the heating element 16 and directly below the projecting portion of the thermal head 10.

Next, by the stencil making device having the above-mentioned structure,
A process of forming dot holes in the film material 12 according to the print data and printing an image on the recording paper using the film material 12 will be described.

First, the film material 12 is fed to the thermal head 10 and the platen 11 by a film feed roll (not shown).
When sent to the punching position D between the (cylindrical members 21a, 21b), the print data for one line is output to a control circuit (not shown) at a corresponding timing. The control circuit outputs an output (current) according to the supplied print data to the heating element 16 via the segment electrode 26. For example, in FIG. 3, a signal (current) is applied to the segment electrode 26 _n according to the print data.
Is supplied, the current flowing from the segment electrode 26 _n to the heating element 16 flows to the ground via the common electrodes 25 _n and 25 _n −1. Therefore, at this time, the area 16 '
Portion (hereinafter referred to as heat generating portion) generates heat, and this heat is transmitted to the film material 12 immediately below via the protective film 18. Therefore,
The portion of the film material 12 at the corresponding position is heated to the glass transition temperature, and the film material 12 at the above position abruptly contracts to return to the original state as described above. Spread widely. At this time, the space 23 is formed immediately below the position where the heating element 16 is arranged, and the film material 12 is formed in the space 2 as shown in FIG.
It bends to the 3 side, and the pressure contact force to the film material 12 is weakened.
Therefore, unlike the conventional case, the pressure contact force from the platen 11 does not hinder the expansion of the holes formed in the film material 12. That is, by constructing the platen 11 and the like as in the present embodiment, the force F ′ (conventional example in FIG. 8) that inhibits the expansion of the perforations formed in the film material can be eliminated. Therefore, the holes formed in the film material 12 are enlarged to form dot holes having a predetermined size (for example, dot holes having a diameter smaller than the dot pitch in the main scanning direction). Such holes are successively formed immediately below the heating element 16 to which electric current is supplied, and first, dot holes corresponding to the print data of one line are formed in the film material 12.

After that, as the film material 12 moves in the direction of arrow B (sub-scanning direction) by the rotation of the film feed roll, the above-described dot hole forming process is repeated.
At this time, the moving speed of the film feed roll is controlled so that the diameter of the formed dot holes is smaller than the pitch of the dot holes. Such a punching process is performed, and the punching position D
The film material 12 that has passed through is a state in which dot holes according to the print data are entirely formed.

FIG. 4 shows the film material 12 as described above.
It is a figure which shows the state of the dot hole formed in. However, the figure shows an example in which all of the print data is, for example, "1", that is, when all the signals are signals that form dot holes. Even if all the print data are "1" as shown in the figure, the diameter p'of the dot holes in both the main scanning direction and the sub scanning direction is made smaller than the dot pitch p, and as shown in the figure, adjacent holes are formed. There is no single, independent one
One dot hole can be formed.

Further, in the stencil making device 9 of this embodiment, the space 23 is formed immediately below the heating element 16, so that heat is not directly transferred to the base body 20 (platen 11). Therefore, the space 23 plays a role as a heat insulating material, and the thermal head 1
Prevents the heat of 0 from being taken to the platen 11.

The film material 12 thus formed with the dot holes is further fed to the printing position by the rotation of the film feed roll, and ink printing according to the dot holes of the film material 12 is recorded by, for example, an ink roll or the like. Do on paper. That is, the dot holes according to the print data are formed in the film material 12, and the ink applied to, for example, the upper surface of the film material 12 is printed on the recording paper through the dot holes to form a transfer image on the recording paper. ..

In the present embodiment, the two columnar members 21a and 21b are arranged to form the space 23 directly below the heating element 16, but the present invention is not limited to this structure and is directly below the heating element 16. Any structure may be used as long as a concave groove is formed in the.

For example, FIG. 5 shows the substrate 2 directly below the heating element 16.
0 is provided with the groove 24 directly. Even if the groove 24 is directly provided in the base body 20 which constitutes the platen 11 as described above, when the hole opened at one point of the film material 12 is enlarged by the heat generation of the heating element 16 as in the above-described embodiment, the groove 24 is formed. As shown in the figure, the film material 12 is bent toward the groove 24 side, the pressure contact force to the film material 12 is weakened, and it does not hinder the expansion of the hole formed in the film material 12. Therefore, the stencil making apparatus having the configuration shown in FIG. 3 can accurately form the dot holes of a predetermined size.

[0020]

As described in detail above, according to the present invention, the groove is formed in the platen portion located directly below the heating head, so that the contact pressure between the film material and the platen can be reduced. It is possible to form dot holes having a predetermined shape in the film material.

The present invention also has a heat insulating effect due to the space formed on the peripheral surface of the platen, so that the heat generated in the thermal head is not taken away by the platen, and the dot holes can be formed with extremely small electric power (extremely small energy). Can be formed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a thermal head and a platen that constitute a stencil making apparatus according to an embodiment.

FIG. 2 is a perspective view of a platen that constitutes the stencil making apparatus of one embodiment.

FIG. 3 is a diagram illustrating a configuration of a heating element and electrodes in a thermal head.

FIG. 4 is a diagram illustrating a state of dot holes when print data is all “1”.

FIG. 5 is a diagram illustrating a modified example of the stencil making device of the embodiment.

FIG. 6 is a diagram illustrating a stencil making device of a conventional example.

FIG. 7 is a diagram illustrating a problem of a conventional stencil making device.

FIG. 8 is a diagram illustrating a problem of a conventional stencil making device.

[Explanation of symbols]

 9 Stencil making device 10 Thermal head 11 Platen 12 Film material 13 Aluminum base 14 Ceramic base 15 Glaze 16 Heating element 17 Protective film 18 Lubricant 20 Base 21a, 21b Cylindrical member 22 Adhesive 23 Space part 24 Groove

Claims (1)

[Claims] 1. A stencil making device in which a heating head, a stretched thermoplastic film, and a platen are arranged in this order, and a heating stencil is placed on the thermoplastic film to create a stencil for printing. The dot shape in the direction is smaller than the dot pitch of the image to be formed, and the dot shape in the sub-scanning direction is set to be smaller than the dot pitch of the image to be formed in the same manner as the main scanning direction. A stencil making apparatus comprising: a driving unit for moving the platen, wherein the platen is provided with a concave groove at a position where the heating head abuts.