JPH06198833A - Plate making method for thermal stencil original plate - Google Patents

Abstract

PURPOSE:To obtain a thermal plate making method for a substrateless original film in which problems of an occurrence of sagging wrinkle on a plate film and a deterioration of a plate image accuracy are resolved in thermally making a plate out of a substrateless original film. CONSTITUTION:In a thermal plate making of a thermal stencil original film made of a single thermoplastic resin film by a thermal head with heating elements laterally arranged in a line, a perforation image made of independent holes are formed on the surface of the original film. At this time, in this plate making method for a thermal stencil original plate, a fixed tensile force (0.7-2.0kg/mm<2>) is applied to the film in the sub-scanning direction so that the perforation image part formed on the surface of the film can be expanded or contracted by a degree within + or -1% in the sub-scanning direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique in the field of digital stencil printing. More specifically, the present invention relates to a thermosensitive stencil printing original plate film (hereinafter referred to as a supportless original plate) which is composed of a thermoplastic resin film alone and has no support. Abbreviated as film).

[0002]

2. Description of the Related Art Conventionally, in digital stencil printing, a thermal head in which fine heating elements are arranged in a horizontal line is contacted with a thermoplastic resin film (hereinafter abbreviated as film) laminated on a support such as paper. Then, the heating element is energized in a pulsed manner to form a hole, and then the ink is exuded from the hole portion for printing. The thermal head used here is an electronic component that outputs an electric signal as heat. For example, thermal transfer printing that transfers an ink layer from an ink transfer ribbon or ink transfer sheet to paper, or printing in which the image receiving paper itself develops heat. It is widely used in printers and the like for performing.

By the way, when a film laminated on a support such as the above-mentioned paper is used as a stencil plate and the plate is thermally perforated by a thermal head to make a plate, the life of the thermal head is extremely long because the energy required for the plate making is large. There is a problem that it is very short. In order to solve this problem, a method of using a supportless original plate film as a stencil original plate has been proposed. In this method, since the substrate-less original film is thermally perforated, it is possible to perforate the original film with significantly less applied energy than the conventional method of thermally perforating the film laminated on the substrate, thus reducing the load on the thermal head. The thermal head life is increased. In addition, the use of the supportless original plate film has an advantage that image defects of solid black portions due to the pattern of the support, which occurs in a conventional original film having an ink permeable support, do not occur. However, in the case of using the supportless original plate film as described above, a new problem that the film shrinks when heat is applied by the thermal head occurs due to the absence of the support. The present inventors conducted various studies on this film shrinkage, and found that the plate-making film obtained by heat-perforating a supportless original plate film (heat-perforated film) had its heat-perforated part contracted in the longitudinal direction, It has been found that a slack wrinkle is generated on the film due to the shrinkage and the precision of the plate-making image is deteriorated due to the shrinkage.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the above-mentioned slack wrinkles that occur when a support-less original plate film is thermally prepressed and the problem of deterioration of plate-making image accuracy. It is an object of the present invention to provide a thermal plate making method for a film.

[0005]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, a heat-sensitive stencil plate film consisting of a thermoplastic resin film alone is thermally plate-made by a thermal head having a heating element arranged in a horizontal row, and a perforated image consisting of independent holes on the plate film surface. When forming the film, a constant tensile force is applied to the film in the sub-scanning direction so that the expansion / contraction ratio in the sub-scanning direction of the perforated image portion formed on the film surface is within ± 1%. A method of making a heat sensitive stencil original plate is provided. Here, the sub-scanning direction means a direction (longitudinal direction) perpendicular to the direction (main scanning direction) in which the heating elements are arranged in one horizontal line.

The film used as the original plate in the present invention may be a general thermoplastic resin film formed by an extrusion method, a casting method or the like, and may be a polyester type, nylon type, polyolefin type, polystyrene type, vinyl chloride type, Acrylic acid derivative-based, ethylene-vinyl alcohol-based, polycarbonate-based homopolymers or copolymers are preferable raw materials. Of these, polyester-based copolymers are particularly preferable, and various polyesters in which different polycarboxylic acids and / or different polyols are present in the component are preferable. Further, even among nylon-based polymers, copolymerized nylon obtained by copolymerizing two or more types of homonylon is particularly preferable. In the present invention, any film that shrinks to some extent when heated at 100 ° C. for 10 minutes can be used, but the preferable range of the heat shrinkage ratio may be appropriately determined in consideration of plate making conditions. The preferred film used for the original plate is a film having a high perforation sensitivity, and therefore, the thermoplastic resin of the film material should have a crystallinity of 15% or less, and more preferably a substantially amorphous level of thermoplasticity. It is a resin. As described above, one of the reasons why the copolymer system containing different compounds as the polyester or nylon polymer is preferable,
This is because the copolymer system is more difficult to crystallize. The thickness of the original film is 0.5 to 20 μm, preferably 1.5.
It is preferably 10 μm.

The above original film may be provided with a heat fusion preventing layer on the surface of the film in order to prevent heat fusion to the heating element of the thermal head. Examples of the heat fusion inhibitor used for this purpose include fatty acid metal salts, phosphoric acid ester type surfactants, fluid lubricants such as silicone oil, and fluorine compounds having a perfluoroalkyl group. Further, the coating amount of the heat fusion inhibitor is 0.001 to
2.000 g / m ² , preferably 0.005 to 1.000
It is g / m ² . Further, in order to prevent transport defects and the like due to static electricity, an original film having an antistatic agent coated on the film surface can be used. The antistatic agent used for this purpose may be a general antistatic agent such as polyalkylene oxide, ester, amine, metal salt of organic sulfonic acid, carboxylate salt, quaternary ammonium salt and alkyl phosphate ester. The coating amount is 0.001 to 2.
0 g / m ^2, preferably from 0.01 to 0.5 g / m ^2.
The antistatic agent may be applied by a usual method. It is also possible to impart an antistatic effect by adding an antistatic agent to the film. Antistatic agents added for this purpose include organic sulfonic acid metal salts, polyalkylene oxides and quaternary compounds. Ammonium salts are preferred.

In the thermal plate-making method of the present invention, the above-mentioned film alone is used as it is as an original plate, and this plate is thermally plate-made by a thermal head having a heating element arranged in a horizontal line, and the original film surface is provided with independent pores. In forming the perforated image, a constant tensile force is applied in the sub-scanning direction, that is, the longitudinal direction of the original film, and the expansion / contraction ratio of the thermal perforated image portion in the sub-scanning direction is maintained within ± 1%. As a method of giving a tensile force to the original film, when the original film heat-pressed with a platen roll on the thermal head,
If it is a method that can give a constant tensile force in the longitudinal direction,
Although any method can be adopted, it is preferable to apply a tensile force so as to apply a tensile force by pulling the original film in the plate-making front direction (the traveling direction of the film). Further, an original film pressed by a platen roll on the thermal head, a direction opposite to the traveling direction of the original plate,
That is, it is possible to maintain the degree of expansion / contraction within the range of ± 1% by pulling the plate in the backward direction, but in this case, the platen roll may hinder the forward feeding of the original film. It is not so preferable because there are many. However, it is a preferable method to apply a weak tensile force to the rear direction at the same time as the front direction.

In the present invention, the tensile force per cross-sectional area applied to the original film in the traveling direction is 0.7 to
It is preferable to specify in the range of ² kg / mm ² . When the tensile force is smaller than this range, horizontal wrinkles occur in the perforated image portion formed on the original film and the peripheral portion thereof, and distortion occurs in the perforated image, and the perforated image faithful to the original image (plate making image) Will not be obtained. On the other hand, when the tensile force is larger than the above range, the original film is made in a stretched state. And after plate making, the dimensions of the perforated image area formed by the thermal perforation are not heat-fixed in the expanded state and do not return to the original state, while other non-perforated areas are film elastic. Return to the size close to the original size. Therefore, the plate-making film (perforated film) obtained has slack in the heat-punched portion, and that portion becomes a slack wrinkle. In the present invention, with respect to the original film, along with the tensile force in the front direction, it is preferable to give a tensile force in the rear direction, the tensile force in the rear direction in this case is 0.5 kg / mm ² or less. Is preferred. If the pulling force in the backward direction is large, it becomes difficult to feed the original plate as the platen roller is driven during plate making, and development such as slipping of the platen roller on the original film occurs. According to the present invention, by applying a tensile force to the original film as described above,
It is possible to obtain a plate-making film having a perforated image with good dimensional accuracy, which is free from slack wrinkles, while maintaining the expansion / contraction ratio of the thermal perforation image hole portion within ± 1%.

The thermal head used in the present invention is
The heating elements are arranged in a horizontal row. As such a thermal head, any one can be used as long as it can thermally form independent holes on the original film surface,
In the case of the present invention, regarding the dimension of the heating elements, the length in the main scanning direction is 15 to 75% of the pitch between the heating elements, preferably 15
It is preferable to use a thermal head in which the length in the sub-scanning direction is 15 to 75%, preferably 15 to 55% of the pitch between the heating elements in the range of ˜50%. A plate-making film obtained by using a thermal head in which such a heating element is specified to have a specific size is produced from the plate-making film when printing a black solid image or a loop image such as a circle (○) in the plate-making image. Even when there is a perforated image that easily falls out,
There is an advantage of giving a printed image without missing of those images. Further, when the original film is heat-perforated using a thermal head in which the dimensions of the heating element are specified in a specific range, the ratio of the perforated area formed in the plate-making film to the total area of the plate-making film becomes low, and There is also an advantage that the overall heat shrinkage of the plate-making film (heat-perforated film) used can be prevented. Further, the density of the heating elements of the thermal head (the number of existing heating elements per unit length) is preferably 12 dots / inch or more.

Next, Tables 1 and 2 show the relationship between the plate making conditions of the original film and the condition of the obtained plate making film, and the relationship between the plate making film and the quality of the printed matter obtained using the plate making film. Shown in. All of the data shown in Table 1 and Table 2 are shown in FIG.
The present invention relates to a plate-making film obtained by using the plate-making device having the structure shown in. Table 1 shows the results when an original film having a width of 260 mm was used, and Table 2 shows a width of 210 m.
The result when the original film of m is used is shown.

[0012]

[Table 1]

[0013]

[Table 2]

From Tables 1 and 2, in order to suppress the occurrence of wrinkles due to the sagging phenomenon, the expansion / contraction ratio in the sub-scanning direction that occurs during thermal plate making should be within a range of ± 1.00%. Desirably, it has been found that such an expansion / contraction ratio does not cause any particular problem in the image appearing on the printed matter. Further, the value of the pulling force (front load in Tables 1 and 2) in the plate-making front direction of the original film necessary for this is 0.7 to 2.0 kg / m.
in the range of m ^2, front tension than this range is too small, transverse wrinkles may occur in the portion and its peripheral portion of the thermal plate making image, contraction image in the sub-scanning direction is recognized that somewhat occur. On the other hand, if the front pulling force is larger than the above range, the sub-scanning direction is stretched due to the pulling force, and the portion that has been thermally perforated is thermally fixed in the stretched state, but not thermally perforated. In the part, it shrinks due to the elasticity of the film and returns to the original state, causing slack in the heat-punched part,
Wrinkles occur in this portion and the length of the image in the sub-scanning direction also increases (see Experiment 17).

Further, according to the detailed study by the present inventors,
By pulling the supportless original plate film backward at the time of thermal plate making with a force of 0.5 kg / mm ² or less together with the forward pulling force, the shrinkage suppressing effect in the sub-scanning direction is further improved, and the plantain roller described above. It was found that it is possible to obtain a plate-making film that faithfully reproduces the original without causing problems such as slipping on the original film, and thus causing no problem of connecting the heat-punched holes. . In this case, the rear pulling force is 0.5 kg
/ Mm ² exceeds the above-mentioned slip (Experiment 30
It was confirmed that the perforations formed on the film were continuously opened in the sub-scanning direction due to the poor feeding of the original plate.

The thermal plate-making method according to the present invention may be carried out by an apparatus in which a device for applying a forward pulling force or a forward pulling force and a backward pulling force is added to an ordinary heat-sensitive stencil plate making printing apparatus, and these pulling force loads are applied to tension rolls. Etc. can be used. Further, in this case, the appropriate pulling force varies depending on the heat shrinkage rate of the film, the thickness of the film, etc. Therefore, it is desirable to use a tension roll having a variable pulling force value.

[0017]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples.

[Experimental Device] As an experimental device for carrying out the present invention, the device shown in FIG. 1 was produced. This device is
Ricoh's thermal stencil printing machine Preport VT-25
00 is a modification of the plate making device. In FIG. 1, 1 is a platen roll, 2 is a thermal head, 3 is a front tensile load weight, 4 is a rear tensile load weight, 5 is a clamp member, 6 is a roll, 7 is a support-less film, and L is The arrow indicates the plate making direction. As shown in FIG. 1, in the present experimental apparatus, there is a support-less film 7 on the heating element of the thermal head 2, and the platen roll 1 presses this against the thermal head 2. Further, in this apparatus, the clamp members 5 are attached to both ends of the support-less film having an appropriate size, and the clamp members 5 are attached as shown in FIG.
A weight is attached to the center of the film so that a pulling force is applied uniformly in the width direction of the film 7. As the clamp member 5, one having the same length as the width of the support-less film 7 was used, and the clamp member 5 was attached so as to be fastened in the entire width direction of the film 7. In addition to the above, in order to support the film 7 as shown in FIG.
However, since the central axis of the roll is supported by a ball bearing, there is no risk that the roll 6 will apply a load to the film 7.

[Evaluation Method] The heat-sensitive stencil original film was thermally preprinted by the apparatus shown in FIG. 1 and observed with a microscope, and the distance between the center points of a large number of holes independently perforated as black solid portions was 2
The measurement was performed for 0 dots, and from this result, the expansion / contraction rate of the perforated image forming the solid black portion was determined by the following formula. Expansion / contraction ratio (%) = (l−L) / L × 100 L: standard dimension value, distance between upper dot center point and lower dot center point for 20 dots of heating elements arranged in a line 1: measurement The distance between the center point of the upper end hole and the center point of the lower end hole of the 20 independent holes that are formed in the plate making film by the 20 dots of the heating element and are arranged in a vertical line. ) Wrap around the printing drum of Ricoh's thermal stencil printer Preport VT-2500 and print at a printing speed of 90 sheets / min, and visually check whether wrinkles have formed on the image of the printed matter, especially on the black solid portion. I observed. Further, the plate-making film was also examined visually for the occurrence of sagging wrinkles, and if wrinkles were observed, it was examined whether the wrinkles disappeared by pulling the film.
In addition to the above, with respect to the printed matter obtained by the above method, the optical density of the black solid portion was measured by an RD-914 densitometer manufactured by Macbeth Co., and the sharpness of the printed matter printed by the original plate thermally processed by the method of the present invention. Etc.

Example 1 A heat-sensitive stencil printing plate precursor having a thickness of 3.0 μm and a width of 210 m
m polyethylene terephthalate (PET) film, 0.01 g / m ² of silicone oil SF-8422 manufactured by Toray Dow Corning as an anti-fusing agent, and Elegan 264A (No. 4) manufactured by NOF CORPORATION as an antistatic agent. 0.01 g / m ² of a primary ammonium salt-based antistatic agent was applied. The heating element length in the main scanning direction is 31 μm and the pitch between heating elements is 62.5 μm, and the heating element length and the heating element pitch in the sub-scanning direction are 34.2 μm and 6 respectively.
The printing original plate was perforated with the apparatus shown in FIG. 1 by using a thin film type thermal head of 16 μm / mm having a thickness of 2.5 μm as a heat source and applying energy of 0.036 mj / dot. During plate making, the plate making front direction (the sub-scanning direction of the thermal head)
A front load of 0.71 Kg / m with a load of 450 g applied to
m ² and the rearward load is 0.16 Kg /
A load of 100 g was applied so as to become mm ² . Note that these loads are the weight of the weight itself plus the weight of the clamp member. When the plate-making film produced as described above was observed with a microscope, it was found that the perforated portion was elongated by 0.18% in the sub-scanning direction due to thermal plate making. This result means that the dimensional reproducibility of the image is extremely high in this embodiment. Also, according to the result of visual observation of the plate-making film, slack wrinkles that were almost negligible were recognized, but these wrinkles disappeared when lightly pulled. The black solid portion optical density of the printed matter printed with this plate-making film was 0.98, and the image could be printed clearly. No fine line indicating the presence of wrinkles was observed in the printed matter, and the quality of the printed matter was excellent.

Comparative Example 1 Thermal plate making was tried in exactly the same manner as in Example 1 except that no forward load was applied during plate making (the backward load was made the same as in Example 1). When the film thus heat-pressed was observed under a microscope, it was found that the hole-punched portion was contracted by 2.19% in the sub-scanning direction by the heat-pressing. That is, in this comparative example, since the front load was 0, only perforated images with low original reproducibility were obtained. When the perforated film in this case was visually observed, a large number of lateral wrinkles were observed, and these lateral wrinkles did not disappear even when pulled strongly. Further, in the printed matter obtained by using this plate-making film, the image was printed as clearly as in Example 1, but a large number of fine lines (fine lines based on wrinkles on the plate-making film) were printed on the printed image. Occurred, and it was not true to the original image.

Comparative Example 2 The thickness of the original plate used was 2.1 μm, and the front load was 2.
900g front load to achieve 04Kg / mm ²
(Including clamp weight), rear load is 0.23 Kg
The PET film was heat-perforated in exactly the same manner as in Example 1 except that the rear load was set to 100 g (including the clamp weight) in order to set the thickness to / mm ² . When the film thus heat-pressed was observed with a microscope, it was found that the punched portion was elongated by 2.30% in the sub-scanning direction due to the heat-pressing, and in this case also, the reproducibility of the original was poor. Further, when the perforated film was visually observed, the occurrence of slack wrinkles was recognized, but these wrinkles were such that they disappeared when strongly pulled. However, when printing was performed using this film, the image was clearly printed, but fine lines due to wrinkles on the film were generated on the image, and the printed image faithfully reflected the original image. I couldn't say.

Comparative Example 3 The same PET film as in Comparative Example 2 was used as an original plate, and 3
A front load of 00g and a rear load of 500g are applied, the front load is 0.68Kg / mm ² , and the rear load is 1.13K.
It was set to g / mm ² . Example 1 other than the points described above
In this case, the plate was made by the same method as the above, and the platen roll slipped during plate making due to the large rear load, and the original plate could not be sent as the platen roll was driven. According to the result of microscopic observation of the obtained perforated film, the holes formed in this film were continuously opened in the sub-scanning direction. The shrinkage of the perforated portion in the sub-scanning direction was 0.96%. In addition, when visually observing this plate-making film, horizontal wrinkles were generated in this film, but these horizontal wrinkles disappeared when strongly pulled. The printed matter obtained by using this plate-making film, although fine lines due to wrinkles on the film were not observed, the image is blurred in places due to the continuous opening described above, and the printed matter faithful to the original image is I couldn't get it.

[0024]

According to the heat-sensitive stencil plate making method of the present invention, it is possible to obtain a high-quality plate-making film for heat-sensitive stencil which is free from slack wrinkles and has excellent dimensional accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of an experimental apparatus for plate making used in Examples.

[Fig. 2]

FIG. 1 is a front view showing a load-bearing portion in the experimental apparatus shown in FIG.

[Explanation of symbols]

 1: Platen roll 2: Thermal head 3: Front tensile force load weight 4: Rear tensile force load weight 5: Clamping member 6: Roll 7: Supportless film

Claims (3)

[Claims] 1. A heat-sensitive stencil original film composed of a single thermoplastic resin film is thermally plate-made by a thermal head having a heating element arranged in a horizontal row to form a perforated image having independent holes on the surface of the original film. At that time, the expansion / contraction ratio in the sub-scanning direction of the perforated image portion formed on the film surface is ±
A method for making a heat-sensitive stencil original plate, which comprises applying a constant tensile force to the film in the sub-scanning direction so as to be within 1%. 2. The tensile force is applied in the plate making front direction of the original film, and the value is 0.7 to 2.0 kg / mm.
^2. The method for making a heat-sensitive stencil original plate according to claim 1, which is in the range of ² . 3. The plate-making method for a heat-sensitive stencil according to claim 2, wherein the tensile force is also applied in the plate-making rearward direction of the original plate film, and the value is 0.5 kg / mm ² or less.