JP2002029021A - Plate making method for master for thermal screen printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of sagging or wrinkles generated in a master for thermal screen printing and the deterioration of the dimensional accuracy of a plate making image at the time of thermal plate making of the master. SOLUTION: In subjecting the master for thermal screen printing comprising an at least stretched thermoplastic resin film to perforation recording by a thermal head or laser, the tension applied to the master from a perforated part in a master advance direction and/or a rear direction is controlled corresponding to an image state performing perforation recording.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to heat-sensitive stencil printing, and more particularly to a method for thermally making a heat-sensitive stencil master having a stretched thermoplastic resin film.

[0002]

2. Description of the Related Art Conventionally, in heat-sensitive stencil printing, a thermal head having fine heating elements is brought into contact with a thermoplastic resin film laminated on a support such as porous thin paper, and the heating elements are pulsed to energize the film. After the holes are formed, the ink is leached from the holes to perform printing.

As a support such as the above-mentioned porous thin paper, a mixture of hemp fiber, synthetic fiber, wood fiber and the like is actually used, and a thermoplastic resin film is bonded on this with an adhesive. Make a master from the pasted master,
When subjected to printing, there are the following problems. (1) A large amount of adhesive accumulates in the form of a bird's web in a portion where the film is in contact with the portion where the fiber overlaps, making it difficult for the thermal head to pierce that portion. In addition, the portion hinders the passage of ink, and printing unevenness occurs. (2) The fibers themselves impede the passage of ink, causing printing unevenness. (3) Porous thin paper or the like is expensive, and loss due to lamination is large, so that the master becomes expensive and resources are consumed. (4) When the printed papers overlap, a set-off occurs in which the ink adheres to the back surface of the paper overlaid thereon.

Several masters have been proposed in consideration of these points. For example, JP-A-3-193445 discloses an ink-permeable support (porous layer) using ultrafine fibers having a fineness of 1 denier or less. According to this, the problems (2) and (4) are solved,
Problems (1) and (3) remain. Japanese Patent Application Laid-Open No. 62-198459 discloses a method of forming a heat-resistant resin pattern having a substantially closed shape on a film by using a printing method such as gravure, offset, or flexo. However, it is difficult to print a pattern having a line width of 50 μm or less with the current printing technology, and even if it is possible, the productivity is low and the cost is high. Moreover, in general, when the line width is 30 μm or more, the heat-resistant resin hinders perforation by the thermal head, and printing unevenness occurs.

However, Japanese Patent Application Laid-Open No. 54-33117 discloses a master that does not use a support and consists essentially of a film.
The problems (2) and (3) are solved, but on the other hand, a new problem is caused. One of them is 10 films
When the thickness is less than μm, the stiffness
s) is weak, making transport difficult.

As a solution to this problem, Japanese Patent Publication No. 5-70595
Japanese Patent Application Laid-Open Publication No. H11-163873 discloses that the film is wound around the peripheral wall of the plate cylinder of the stencil printing machine without being cut, and the entire film rotates together with the rotation of the plate cylinder during printing. However, in this method, since the film and the plate discharging unit rotate with the rotation of the plate cylinder during printing, the rotational moment increases, and the deviation from the rotation axis of the center of gravity is large. There is a problem that it must be increased. Another is that when the film has a thickness of 5 μm or more, its thermal sensitivity is reduced, and it is difficult to perform perforation by a thermal head.

As means for solving these problems, Japanese Patent Laid-Open No.
Japanese Patent Application No. 0-24667 discloses a master in which a fluid containing a resin, a good solvent thereof, and a poor solvent is applied to a film and dried to form a porous film. During the drying process, the resin is deposited due to the relative increase of the poor solvent due to the evaporation of the good solvent and the concentration of the liquid during the drying process, and the resin is dried to form a porous film consisting of a three-dimensional network structure on the film. Is done. Certainly, according to this master, an effect superior to the masters known so far can be obtained. Also, JP-A-11-2
Japanese Patent No. 35885 discloses a master in which a fluid mainly composed of a W / O (water-in-oil) emulsion is applied onto a film and dried to form a porous film. This master also has many advantages over the conventional master.

However, all masters, in particular, a master having an ink-permeable support (porous layer) using ultrafine fibers, a master having a porous layer formed by coating, and a master consisting essentially of a film without a support are used. In the case of thermal plate making, there is a problem of sagging wrinkles occurring at a boundary between a perforated portion and a non-perforated portion of a prepressed master and a problem of contraction of a prepress image. The problem is hemp fiber, synthetic fiber,
This also occurs in masters that use porous thin paper mixed with wood fibers etc. as a support, but because the porous thin paper support gives the master a high stiffness, the degree is only reduced, When the image size system became required, it could not be ignored. In particular, in the case of a master consisting essentially of a film, the problem became remarkable.

[0009]

The mechanism of the problem of the sagging wrinkles and the problem of the shrinkage of the plate image are as follows. The film has latent stress because it is biaxially stretched to provide thermal sensitivity. At around 60 ° C., this stress becomes apparent in the stretched film and contraction starts.
The temperature around the hot-perforated portion of the film becomes 60 ° C. to 90 ° C., stress is generated, and the mechanical balance between the near-perforated portion and the non-perforated portion is lost, resulting in a dimensional deviation. This is sagging wrinkles.

At present, tension is applied in the traveling direction and / or backward direction of the master in order to reduce the slack wrinkles. However, when the tension is released, the portion near the thermal perforation contracts due to the stress that has become apparent. As a result, the dimension becomes shorter than that of the non-perforated portion, so that the non-perforated portion has sagging wrinkles. When a larger tension is applied, the portion near the hot perforation becomes elongated when the tension is released, and the dimension becomes longer than the non-perforated portion, and sag wrinkles occur in the portion near the hot perforation. Although there is a tension that does not cause slack wrinkles, the tension varies depending on the size of the perforated portion, particularly the image length in the width direction of the master, that is, the scanning direction of the thermal head, and has not been able to be dealt with until now.
The above is an example where the thermal head is used as a heat source for convenience, but the same applies to laser light.

Further, when the master is pierced by the thermal head, a fusion occurs between the two, that is, a stick is generated, and the running of the master is hindered. Therefore, the printed image is short and short. This also applies a stick prevention agent such as silicone oil on the film, and further applies tension in the moving direction and / or backward direction of the master,
The stick force changes depending on the image length in the scanning direction (width direction) of the thermal head, and it has not been possible to respond sufficiently until now.

When the support is a durable support such as a porous thin paper or a nonwoven fabric, these have suppressed the deformation of the film to some extent. However, from the viewpoints of image quality improvement and resource saving, etc., as described above, the support is composed of "extremely fine fibers having a fineness of 1 denier or less", "porous film by coating", and "substantially only a film not using the support". Master"
In this case, the stiffness and strength have been changed in a direction of decreasing strength, and deformation such as sagging wrinkles has become more and more likely to occur.

In order to solve the problem of sagging wrinkles and shrinkage, Japanese Patent Application Laid-Open No. Hei 6-198833 discloses that
It was proposed that a constant tension be applied to the film at the time of plate making in the direction of travel. According to this, the perforation width of the perforated portion (in the direction perpendicular to the direction of movement of the master), that is, effective under the condition that the image width is constant, but when the perforated width of the perforated portion changes, slack wrinkles occur. Could not be prevented. Further, Japanese Patent No. 2856632 proposes a plate making apparatus having a pressing roller for pressing a master immediately after plate making against a platen roller. This countermeasure was effective to some extent in plate making with a small plate making area or with no solid image. Of course, a film without stretching is unlikely to cause sagging wrinkles, but has low thermal sensitivity and is not practical.

The present invention has been made in view of the above background, and an object of the present invention is to provide a master plate making method which solves the problem of sagging wrinkles and the problem of shrinkage of a plate made image caused by a stick when the master is made by heat. Aim.

[0015]

Means for Solving the Problems The present inventors have studied the above problems, and found that, when the stretched master is pierced by heat, the tension applied to the master in the advancing direction and / or the rearward direction of the master from the perforated portion. It has been found that it is important to control the size of the hole according to the state of the image to be pierced.

That is, according to the present invention, first, when a heat sensitive stencil printing master made of at least a stretched thermoplastic resin film is punched and recorded by a thermal head or a laser, the master travel direction and / or from the punched portion.
Alternatively, there is provided a method of making a master for thermosensitive stencil printing, wherein the tension applied to the master in the backward direction is controlled according to the state of the image to be punched and recorded. As mentioned above,
When performing perforation recording, by applying tension to the master by controlling the tension applied in the master advancing direction and / or backward direction from the perforated portion in accordance with the state of the image to be perforated, a platemaking master with less slack wrinkles can be obtained. . The “image state to be punched and recorded” includes the density, area, shape, position, etc. of the image, but in particular, the thermal signal applied by the thermal head or laser in the master width direction in one line scan at a certain point in time. The number of dots.

Secondly, in the method for making a master for heat-sensitive stencil printing described in the first aspect, the image state to be punched and recorded is applied to the master in the width direction of the master by one line scan by a thermal head or laser. A method of making a master for thermosensitive stencil printing, characterized by the number of dots of a signal, is provided. "Image state for punch recording" described in the first
Among them, the number of dots of the heat signal applied in the width direction of the master in one line scan by the thermal head or laser determines the generation of the sag wrinkle. Therefore, by controlling the tension in accordance with the number of dots by the heat signal, the occurrence of sagging wrinkles can be effectively suppressed.

Thirdly, in the method for making a master for thermosensitive stencil printing described in the first aspect, the state of the image to be punched and recorded is the size (width × length) of the solid black of the document. A method for making a master for thermosensitive stencil printing is provided. The “image state to be punched and recorded” has a large effect on the occurrence of sagging wrinkles in the case of a document including a solid black image. Therefore, by detecting the size of the solid black and controlling the tension, the sagging wrinkles can be clearly reduced.

Fourthly, in the method for making a master for heat-sensitive stencil printing described in the first aspect, the tension applied to the master in addition to the state of the image to be punched and recorded or in accordance with the ambient temperature at the time of recording alone. Provided is a method for making a master for heat-sensitive stencil printing, which is characterized by controlling. The sagging wrinkles, looseness, and plate making image shrinkage change according to the “image state to be punched and recorded”.
It changes depending on humidity, plate making energy and the like. It is an effective method to detect these conditions in addition to the state of the image to be perforated and to control the tension applied to the master, and it is particularly effective to add a temperature condition during recording.

Fifth, in the plate making method of a thermosensitive stencil printing master made of at least a stretched thermoplastic resin film, the master is arranged in front of and behind the perforated part via a perforated part consisting of a thermal head and a platen roller. A device that can press the master consisting of two rollers and a pressure bolt, sandwiches the master between the rollers, rotates the roller at a surface speed higher than the transport speed of the master, and controls the roller pressing force according to the punching width A method for making a master for heat-sensitive stencil printing is provided. As a method of applying tension to the master, as described above, the master is sandwiched between two rollers, and the torque for driving the rollers is controlled according to the perforation width, that is, the rollers are rotated at a speed slightly higher than the transport speed of the master. By controlling the pressing force of the two rollers according to the perforation width, it is easy to obtain a plate-making master with less slack and wrinkles.

[0021]

Embodiments of the present invention will be described below. As the image state to be perforated as described above, the number of dots of the heat signal applied in the master width direction in one line scan at a certain point in time by the thermal head or the laser is mentioned. The number may be counted, or other substitute characteristics, such as power consumption, may be measured. If there is an image in the entire width direction, the number of dots of the heat signal applied in the master width direction becomes maximum. When this number is large, there are many places where the shrinkage stress of the film appears, and the stick force is large. Therefore, it is necessary to increase the tension in the master traveling direction.

When tension is applied to the master in the traveling direction and / or the rear direction of the master, the tension is cut at the thermal head / platen portion, and the master is divided into a front portion (traveling direction) and a rear portion. The magnitude of each tension is determined experimentally, but is larger at the front, specifically, 0.7 to 3k.
g / mm ² , that of the rear part is not more than 0.5 kg / mm ² .

When the shrinkage stress of the biaxially stretched polyester film having a thickness of 2 μm was measured, the shrinkage started at about 60 ° C. and showed a maximum shrinkage stress of 0.5 kg / mm ² at about 90 ° C. If the tension in the forward direction is made equal to the full-width contraction stress, the tension contracts when the tension is released, and the balance with the non-perforated portion is lost, resulting in slack wrinkles. Therefore, it is necessary to control the tension within a range larger than the full width shrinkage stress so that when the tension is released and contracted, the length becomes the same as that of the non-perforated portion. Since the stick force is naturally proportional to the perforation width, if the tension is controlled in accordance with the perforation width, it is possible to prevent plate-making shrinkage by the stick.

There is no particular limitation on the method of applying tension to the master. For example, as described above, the master is sandwiched between two rollers, and the rollers are rotated at a surface speed slightly higher than the transport speed of the master, so that the two A method of controlling the roller pressing force according to the perforation width is an effective method. As the perforation width, the number of dots of the heat signal may be counted, or other characteristics, such as power consumption and the size of a signal when capturing an image, may be measured. The operator may naturally control the tension applied to the master while viewing the image.

FIG. 1 shows an example of a method of sandwiching the above-mentioned master between two rollers. In FIG. 1, reference numeral 1 denotes a plate making apparatus for a heat-sensitive stencil master. The master 2a unwound from the master roll 2 passes between the two rolls 10a and 10b of the rear tension applying device 10 and is perforated in the perforating section 3 in accordance with an image signal.
The sheet is transported by the transport device 30 through the space between a and 20b. Pressing bolts 10c are mounted on both ends of the rear tension applying device 10, and the operator operates the
Of the master is controlled by controlling the tension of the master with the perforated portion 3. 10b has a driving device (not shown) for rotating it. The same applies to the front tension applying device 20. FIG. 2 shows the tension control part of FIG.

Next, the film used for the master of the present invention may be a biaxially oriented film such as vinyl chloride, vinyl chloride-vinylidene chloride copolymer, polypropylene, polyester, etc. Those that have been used are preferably used. The thickness of the film is 0.5 to 10 μm, preferably 1.0 to 5.0 μm. If it is less than 0.5 μm, it is too thin to apply the resin liquid, and if it exceeds 10 μm, it becomes difficult to perforate with a thermal head.

Also in the master of the present invention, a stick prevention layer for preventing stick with a thermal head can be provided on the opposite surface of the film on which the porous film is formed.
In this case, as the stick preventing agent to be used, a silicone-based release agent, a fluorine-based release agent, a phosphate ester-based surfactant, and the like generally used in a conventional master for stencil printing can be used. An antistatic agent for preventing generation of static electricity may be added.

[0028]

Next, the present invention will be described in more detail by way of examples. However, the present invention is not limited by the following examples. In the examples, all parts are parts by weight.

[Experimental Apparatus] The apparatus shown in FIG. 3 was used as an experimental apparatus for carrying out the present invention. This is a modified version of the plate making device of Ricoh's thermosensitive stencil printing machine Preport VT-2500 (JP-A-6-198883).
Reference). In FIG. 3, 41 is a platen roll,
42 is a thermal head, 43 is a weight for front tension load, 4
Reference numeral 4 denotes a rear tension load weight, 45 denotes a clamp member, 46 denotes a roll, 47 denotes a master, and an arrow L denotes a plate making direction. As shown in FIG. 3, in this experimental apparatus, a master 47 is provided on a heating element of a thermal head 42,
Presses against the thermal head 42. Further, in this apparatus, a clamp member 45 is attached to both ends of a master having an appropriate size, and a weight is attached to the center of the clamp member 45 as shown in FIG. 4 so that tension is uniformly applied in the width direction of the master. is there. The clamp member 45 having the same length as the width of the master 47 is used.
Was mounted so as to be tightened in the entire width direction. In addition to the above, rolls 46 are attached before and after the thermal head to support the master 47 as shown in FIG. 3, but since the center axis of the roll is supported by ball bearings, a load is applied to the master 47 by the roll 46. There is no danger.

[Evaluation method]Percentage of perforated image  With the apparatus shown in FIG. 3, two types of black solid (width 1
0cm x length 10cm, width 20cm x length 20cm)
Used at ambient temperature of 10 ° C, 20 ° C and 30 ° C, before
Heat-stencil master with different weights
Observed between the centers of a number of independently drilled holes as solid black
The distance was measured for 20 dots.
The expansion and contraction rate of the perforated image that forms the
Was. Dots for 10 cm and 20 cm printing
And measured as the printing rate (%) in the main scanning direction. Expansion / contraction ratio = (ML) / L × 100 L: 20 dots of heating elements arranged in a vertical line with standard dimensions
The distance between the center point of the top dot and the center point of the bottom dot of the minute
The center of the upper end of the 20 independent holes formed in a vertical line
Distance between point and center point of lower end hole Print ratio in main scanning direction (%) Length of one line: 280 mm, number of dots: 4409 do
t For 10 cm printing: 1543 dots (35%) For 20 cm printing: 3130 dots (71%)Sagging wrinkles  In addition, the presence of sagging wrinkles in the plate making film
Was visually examined. ○ "No occurrence", "Slight"
Δ, “Abundant” was evaluated as ×.

[Use Master] Sample A: Biaxially stretched polyester film, 2 μm in thickness, 260 mm in width, coated with a known silicone-based stick inhibitor on one side. No support. Sample B: The following liquid was prepared. Polyvinyl butyral (BHS manufactured by Sekisui Chemical Co., Ltd.) 2.0 parts Ethyl acetate 30.0 parts Sorbitan monooleate (Sorbon S80 manufactured by Toho Chemical Co., Ltd.) 0.15 parts Talc 0.5 part The above components are dissolved and dispersed, and water is dispersed therein. While stirring 15 parts
It was added slowly to obtain a cloudy emulsion coating solution.
This was applied onto the polyester film of Sample A by drying with a wire bar so as to have an adhesion amount of 7.0 g / m ² to form a porous film. On the opposite side of the film from the side where the porous film was formed, the same silicone-based stick inhibitor as in A above was applied to obtain a master. Using the obtained master samples of A and B, tension was applied depending on the number of dots, the size of solid black, and the ambient temperature, and the effects on the expansion and contraction rate of the image and the sagging wrinkles were tested. Table 1 shows the results.

[0032]

[Table 1]

In the above table, No. 2 and No. Comparing FIG. 8, the expansion / contraction ratio is changed from + 0.83% to −1.04 only when the size of the original black solid is different (printing ratio is 35% to 71%).
% And sagging wrinkles have changed from ○ to ×. This is N
o. In No. 9, the expansion ratio was-
0.04%, sagging wrinkles changed to ○. No. 1
The same can be said for 0, 11, and 12. No. 2,
In 3 and 4, the influence of temperature is seen.

[0034]

As described above, according to the first aspect of the present invention, when a heat sensitive stencil printing master made of at least a stretched thermoplastic resin film is recorded by a thermal head or a laser, it depends on the state of the image to be recorded. This method controls the tension applied to the master in the master advancing direction and / or the rearward direction from the perforated portion. According to this method, even if the image condition for perforated recording changes, the plate making master has less slack wrinkles by changing the tension. Can be obtained. Further, if a proper tension is applied, slack wrinkles and plate-making image shrinkage can be solved.

According to a second aspect of the present invention, the number of dots of a heat signal applied in the width direction of the master in one line scan by a thermal head or a laser is given as the image state to be punched and recorded. By controlling the tension depending on the number, the generation of sagging wrinkles can be effectively suppressed.

According to a third aspect of the present invention, the size of the solid black (width × length) of the document is cited as the image state for punch recording. That is, in the case of a document including a solid black image, the size of the solid black greatly affects the generation of sagging wrinkles. By controlling the tension with the size of the solid black, the sagging wrinkles can be clearly reduced.

According to a fourth aspect of the present invention, the tension applied to the master in accordance with the ambient temperature at the time of recording is controlled in addition to or independently of the state of the image to be recorded by punching. Wrinkles can be effectively suppressed.

According to a fifth aspect of the present invention, as a method of applying tension to the master, the master is sandwiched between two rollers, and the rollers are rotated at a speed slightly higher than the transport speed of the master to reduce the pressing force of the two rollers. Control is performed in accordance with the perforation width. According to this method, a plate-making master with less slack and wrinkles can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a side view showing an example of a device for applying tension to a master.

FIG. 2 is a perspective view showing a tension control portion of the apparatus of FIG.

FIG. 3 is a view schematically showing a plate making apparatus used in an example.

FIG. 4 is a front view showing a load application part in the plate making apparatus of FIG. 3;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 plate making device 2 master roll 2 a fed-out master 3 perforated portion 10 rear tension applying device 10 a, 10 b, 20 a, 20 b roll 10 c, 20 c pressurizing bolt 20 front tension applying device 30 transport device 41 platen roll 42 thermal head 43 forward tension Load weight 44 Back tension load weight 45 Clamp member 46 Roll 47 Master

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tetsuo Tanaka 3-10-4 Fuyodai, Mishima-shi, Shizuoka F-term (reference) 2H084 AA13 AA14 AE05 AE06 AE07 AE07 AE08 CC09

Claims (5)

[Claims] When a thermal stencil printing master made of at least a stretched thermoplastic resin film is punched and recorded by a thermal head or a laser, a tension applied to the master in a master advancing direction and / or a rearward direction from a punched portion is punched and recorded. A method for making a master for thermosensitive stencil printing, characterized in that the master is controlled according to the state of the image to be printed. 2. The method according to claim 1, wherein the image state of the stencil printing master is a thermal signal dot applied in the width direction of the master by one line scan by a thermal head or laser. A method of making a master for thermosensitive stencil printing, characterized in that the number is a number. 3. The stencil printing method according to claim 1, wherein the state of the image to be pierced and recorded is the size (width × length) of the solid black of the document. Plate making method for master. 4. The method for making a master for heat-sensitive stencil printing according to claim 1, further comprising:
A method of making a master for heat-sensitive stencil printing, further comprising controlling a tension applied to the master according to an ambient temperature during recording. 5. A method for making a thermosensitive stencil master made of at least a stretched thermoplastic resin film, wherein two dies are disposed in front of and behind a pierced portion via a pierced portion formed by a thermal head and a platen roller. The master is sandwiched between the rollers by a device that can press the master consisting of the roller and the pressure bolt, and the roller is rotated at a surface speed higher than the transport speed of the master, and the roller pressing force is controlled according to the punching width. A method for making a master for thermosensitive stencil printing, characterized by the following.