JP2014200941A - Plate making apparatus - Google Patents

Abstract

An object of the present invention is to provide a stencil printing apparatus and a stencil printing apparatus capable of perforating a stencil paper with the same good quality regardless of the quality of the stencil paper without shortening the life of the apparatus. To do. A plate-making writing unit includes a thermal head in which heating elements are arranged, a platen roller that can nip a stencil sheet between the thermal head, a thermal head, and a platen roller. A plate making pressure applying mechanism 508 for applying a plate making pressure to the stencil sheet 23 and applying a plate making pressure to the stencil sheet 23, and a plate making pressure variable mechanism 508 for changing the plate making pressure by the plate making pressure applying mechanism 508. Yes. [Selection] Figure 4

Description

  The present invention relates to a plate making apparatus for making a plate by forming perforations in a heat-sensitive stencil sheet using a thermal head.

  Conventionally, as a plate making apparatus used for stencil printing, a thermal head in which a large number of heating elements are arrayed and a thermoplastic resin film (hereinafter also simply referred to as film) side of a heat sensitive stencil paper (hereinafter also simply referred to as stencil paper) In a state where the heating element is in pressure contact, the heating power is driven by supplying power for punching to each heating element based on image information, and the sub-scanning is orthogonal to the main scanning direction with the arrangement direction of the heating elements as the main scanning direction. There is known a technique in which a thermal head and a stencil sheet (master) are moved relative to each other in a direction to form perforations that carry image information for one sheet on the stencil sheet.

  When punching one pixel in such a plate making apparatus, a constant applied voltage calculated from the average resistance value of all the heating elements constituting the thermal head and the target power is continuously applied over a certain period of time. In general, the applied voltage output from the power supply circuit is set so as to achieve the target power.

  However, even if the applied voltage is set so as to achieve a predetermined target power, if the surface condition is deteriorated or deteriorated, such as the surface of the stencil sheet to be punched, the punching diameter will vary and the punching performance will be poor. As a result, image defects such as white spots occur in the printed matter.

  In addition, stencil paper is manufactured by pasting a film and a support (mainly Japanese paper) with an adhesive, but the perforation diameter varies even when the amount of adhesive applied is too large or when the amount applied varies. In addition, perforation performance is reduced.

  In other words, even if the applied voltage is set so as to achieve a predetermined target power, the quality of the stencil sheet, such as the unevenness of the surface of the stencil sheet, that is, the quality of the surface state (smoothness of the film surface) and the amount of adhesive applied, can There is a problem in that the diameter of the perforations varies depending on the factors that influence it.

  Furthermore, even when the target power is constant, that is, when the total amount of heat generated is constant, there is no variation in the perforation diameter in each quality state of the stencil paper, but there is a difference in perforation diameter between low quality and high quality. As a result, a difference in printing performance may occur.

  As countermeasures against these problems, Patent Document 1 proposes changing the punching voltage (see, for example, Patent Document 1).

Japanese Patent No. 3958535

  However, when the surface condition of the stencil sheet deteriorates and the surface irregularities become large and the film of the stencil sheet and the heating element of the TPH (thermal head) cannot be brought into close contact with each other, the voltage for punching the TPH as in Patent Document 1 is used. It is difficult to prevent the occurrence of perforation by simply changing. Therefore, in this case, in order to bring the TPH and the film (PET film) of the stencil sheet into close contact with the stencil sheet, the TPH is more strongly applied via the stencil sheet sandwiched between the TPH and the platen roller. It is necessary to press against the platen roller. For this reason, since the load to the mechanism which applies the pressure of a plate-making apparatus becomes large, the bad effect that an apparatus lifetime becomes short will arise.

  The present invention has been made in view of the above circumstances, and a stencil making apparatus capable of perforating stencil paper with the same good quality regardless of the quality of the stencil paper without shortening the device life. It is an issue to provide.

  In order to achieve the above object, the first feature of the plate making apparatus according to the present invention is that a thermal head in which heating elements are arranged, a platen roller capable of nipping a stencil sheet between the thermal head, And a plate making pressure applying means for applying a plate making pressure to the stencil sheet, and a plate making pressure changing means for changing the plate making pressure by the plate making pressure applying means. .

  The second feature of the plate making apparatus according to the present invention is that it comprises plate making pressure control means for controlling the plate making pressure by the plate making pressure variable means.

  A third feature of the plate making apparatus according to the present invention is that it comprises a detecting means for detecting the quality of the stencil sheet, and the plate making pressure control means controls the plate making pressure based on a signal received from the detecting means. is there.

  According to the first feature of the plate-making apparatus according to the present invention, plate-making pressure variable means is provided, and the plate-making pressure is increased when quality deterioration such as surface irregularities of the stencil sheet is generated, and if not, the plate-making pressure is increased. Since it is possible to perform as usual, it is possible to provide a plate making apparatus capable of performing perforation with the same good quality on the stencil sheet regardless of the quality of the stencil sheet without shortening the life of the apparatus. .

  According to the 2nd characteristic of the plate-making apparatus which concerns on this invention, it can be set as the structure which a user does not need to change plate-making pressure manually.

  According to the third feature of the plate making apparatus according to the present invention, since the plate making pressure is controlled in accordance with the detected quality of the stencil sheet, perforation with a good quality equivalent to that of the stencil sheet is possible regardless of the quality of the stencil sheet. Can be reliably performed for each stencil sheet.

1 is a side sectional view showing a configuration of a stencil printing apparatus to which a plate making apparatus according to an embodiment of the present invention is applied. It is the top view which showed the outline | summary of the operation panel provided in the upper surface of the stencil printing apparatus shown in FIG. It is a side view explaining a plate making pressure variable mechanism in the plate making apparatus of one embodiment of the present invention. It is a perspective view explaining the composition which generates turning power in the plate making pressure variable mechanism in the plate making device of one embodiment of the present invention. It is a circuit diagram which shows the detail of the thermal head which comprises the plate-making apparatus of one Embodiment of this invention. FIG. 2 is a block diagram showing an outline centering on a control circuit system of a plate-making writing unit of a stencil printing apparatus in an embodiment of the present invention. It is a flowchart figure which shows operation | movement of a stencil printing apparatus in one Embodiment of this invention. FIG. 6 is a graph showing an example of the relationship between the glossiness of a stencil sheet and the nip pressure by a thermal head in an embodiment of the present invention. FIGS. 9 (a) and 9 (b) are respectively a stencil printing apparatus according to an embodiment of the present invention, and are a normal stencil sheet (high quality base paper) and a stencil sheet (low quality base paper) having a large degree of surface irregularities. FIG. FIGS. 10 (a) and 10 (b) are examples of perforating a normal stencil sheet (high-quality base paper) and a stencil sheet (low-quality base paper) having a large degree of surface irregularities with a conventional stencil printing apparatus, respectively. FIG.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, the same or similar components as those already described are denoted by the same or similar reference numerals, and detailed description thereof is omitted as appropriate.

  In addition, it should be noted that the drawings are schematic and the dimensional ratios and the like are different from actual ones. Therefore, specific dimensional ratios and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The following embodiments are exemplifications for embodying the technical idea of the present invention, and the embodiments of the present invention are described below in terms of the material, shape, structure, arrangement, etc. of the components. It is not something specific. The embodiments of the present invention can be implemented with various modifications without departing from the scope of the invention. Further, in the following description, any size base paper can be applied as the stencil base paper.

(overall structure)
FIG. 1 is a side sectional view showing a configuration of a stencil printing apparatus to which a plate making apparatus according to an embodiment of the present invention (hereinafter referred to as this embodiment) is applied, and FIG. 2 is an operation panel provided on the upper surface of the stencil printing apparatus. It is the top view which showed the outline | summary. The stencil printing apparatus 1 of the present embodiment uses a thermal head 21 as an output head for plate making, and includes a plate making reading unit 10, a plate making writing unit (plate making device) 20, a cutter unit 30, and a printing unit 40. Has been.

  The plate-making reading unit 10 receives a document setting table 12 for setting a document 13 as a copy, a document sensor 17 for detecting the document 13 set on the document setting table 12, and a detection signal from the document sensor 17. A pair of document conveying rollers 14 that are rotationally driven by a reading motor 18, a contact-type line image sensor 11 that optically reads an image of the conveyed document 13 and converts it into an electrical signal, and the line image sensor 11 reads the image. The document discharge roller pair 15 is rotated by a reading motor 18 including a stepping motor for discharging the document 13 to the document discharge tray 19. A document IN sensor 16 that determines the start of processing of the plate-making writing unit 20 described later by detecting the conveyed document 13 is provided in the downstream portion of the document conveying roller pair 14.

  The stencil writing unit 20 is a film of a stencil sheet (master) 23 fed from a stencil sheet roll 22 and a thermal head 21 (see FIG. 5) composed of four head blocks 21a to 21d each having a plurality of heating elements 21Z. A platen roller 24 that is rotationally driven by a writing motor 25 that conveys the surface side while being pressed against the thermal head 21 and a stencil sheet 23 made by the thermal head 21 are described later. And a base paper transport roller pair 26 that is rotationally driven by a writing motor 25 that transports the paper toward the clamp portion 32. The platen roller 24, the writing motor 25, and the base paper conveying roller pair 26 constitute sub scanning means of the stencil printing apparatus of this embodiment.

  A master surface sensor as a stencil sheet information acquisition means for optically automatically detecting the surface state of the stencil sheet 23 on the film surface side between the stencil sheet roll 22 and the platen roller 24 (thermal head 21) of the stencil writing unit 20. (Glossiness meter) 300 is provided.

  The cutter unit 30 includes a cutter 31 that cuts the stencil sheet 23 when the stencil sheet 23 made by the thermal head 21 reaches a predetermined length wound around the drum 33.

  The printing unit 40 includes a drum 33 including an ink supply unit that supplies a predetermined amount of ink to the inner surface of the ink reservoir 48 formed between the doctor roller 46 and the squeegee roller 47, and printing stacked on the paper feed table 44. A pickup roller 46 that picks up and conveys the printing paper 43 from the sheet stack one by one, a timing roller 42 that sends the printing paper 43 conveyed from the pickup roller 46 at a predetermined timing, and a conveyance path 41 from the timing roller 42. The press roller 35 that presses the printing paper 43 sent to the outer periphery of the drum 33, the separation claw 39 for peeling the printed printing paper 43 from the drum 33, and the printing paper 43 peeled from the drum 33. And a paper discharge tray 49 on which paper is stacked.

  On the outer peripheral surface of the drum 33, there is provided a clamp portion 32 for clamping the leading end portion of the stencil sheet 23 that has been made and conveyed by the thermal head 21. After completion of the clamping, the stencil sheet 23 that has been subjected to the pre-making process is wound around the outer peripheral surface of the drum 33 as the drum 33 is rotated by the main motor 34.

  On the upper surface of the stencil printing apparatus, as shown in FIG. 2, an operation panel 400 having a display panel 401 made of an LCD or the like and an operation key group 402 is provided. It is configured such that any key of the operation key group 402 can be operated while referring to various information displayed.

  The operation key group 402 is provided in a normal stencil printing apparatus such as a plate making start key, a printing start key, a printing mode setting key, a numeric keypad 402a used for inputting the number of prints, a reset key, a job emergency stop key, and the like. Has operation keys.

(Prepressing pressure with thermal head)
FIG. 3 is a side view illustrating the plate making pressure variable mechanism of the plate making / writing unit 20 of the present embodiment. FIG. 4 is a perspective view illustrating a configuration for generating rotational force in the plate making pressure variable mechanism of the plate making / writing unit 20. The plate-making writing unit 20 nips the thermal head 21 and the platen roller 24 to apply a plate-making pressure to the stencil sheet 23, and a plate-making pressure variable that makes the plate-making pressure variable by the plate-making pressure applying mechanism 508 variable. And a mechanism 510. The plate making / writing unit 20 can adjust the size of the perforations formed on the stencil sheet 23 by controlling the plate making pressure by the plate making pressure variable mechanism 510 by a plate making pressure control circuit 180 described later. .

  In the present embodiment, as shown in FIGS. 3 and 4, a casing 512 incorporated in the plate making / writing section 20 and a thermal head holding section 514 attached to the casing 512 are provided. The thermal head holding portion 514 is pivotally fixed around a rotation shaft 518 provided on the casing 512, and the thermal head 21 is driven by the rotational force of the thermal head holding portion 514 generated around the rotation shaft 518. Presses the platen roller 24.

  In the present embodiment, a motor 520 attached to the casing 512 and capable of rotating in both forward and reverse directions, a hooking member 522 that is screw-engaged with the rotating shaft 520a of the motor 520, the hooking member 522, and the casing 512. The tension coil spring 526 is provided around the spring locking portion 524 (see FIG. 4).

  With this configuration, when the tension force of the tension coil spring 526 acts on the spring locking portion 524, the turning force acts on the thermal head holding portion 514. Further, the hooking member 522 moves forward and backward along the axial direction of the rotating shaft 520a by the rotation (forward direction, reverse direction) of the rotating shaft 520a of the motor 520, so that the tensile force generated in the tension coil spring 526 is adjusted. It has become. Therefore, in this embodiment, the hook member 522, the spring locking portion 524, and the tension coil spring 526 constitute the plate making pressure applying mechanism 508, and the motor 520 and the rotating shaft 520a constitute the plate making pressure variable mechanism 510.

(Thermal head heat generation and perforation)
FIG. 5 is a circuit diagram showing details of the thermal head 21, and FIG. 6 is a block diagram showing an outline centering on a control circuit system of the plate-making writing unit 20 of the stencil printing apparatus having the above-described configuration.

  As shown in FIG. 5, the thermal head 21 has 4096 heating elements 21Z, and is divided into four blocks (21a to 21d) for each 1024 heating elements 21Z in order to reduce power consumption. Thus, each block is driven to generate heat in a time-sharing manner by the head control circuit 100 (1 to 4096 in FIG. 5 are heating element numbers corresponding to pixels).

  As shown in FIG. 6, a system circuit microcomputer 410 that controls the entire apparatus is provided in a control circuit system that performs stencil printing on the stencil sheet 23 using the thermal head 21. The microcomputer 410 includes a power supply circuit 140, A head controller 100 having a head control signal generation circuit 160, a print data generation circuit 170, and a plate making pressure control circuit 180, an operation panel 400, a plate making reading unit 10, and a motor controller 28 that rotationally drives the writing motor 25. And the master surface sensor 300 are connected. The system control microcomputer 410 outputs command signals C1,..., C7 for controlling the power supply circuit 140 and the like.

  When the document 13 is set on the document table 12 and the front end of the document 13 is brought into contact with the document conveying roller pair 14, the document sensor 17 detects the document 13 and displays on the display panel 401 that the plate making operation is possible.

  When the plate making start key is depressed while the printing paper 43 of a predetermined size is set on the paper feed tray 44, the size of the printing paper 43 is detected by a copy size detection means (not shown) and the display panel 401 displays the size. The information is displayed, and the document conveying roller pair 14 is rotated by driving the reading motor 18 to start document feeding. Subsequently, when the document IN sensor 16 detects that the document 13 has been conveyed, and then feeds the document 13 by a predetermined length, the stencil sheet 23 is conveyed by driving the platen roller 24, and the stencil sheet feed starts.

  Simultaneously with the start of feeding of the base paper, the image of the original 13 having a predetermined size is optically read by the original 13 by the line image sensor 11 of the plate making reading unit 10. The multi-value data obtained by reading the document 13 is input to an image processing circuit (not shown), converted to binary data, and then input to the print data generation circuit 170 of the head control circuit 100, and based on a command from the system control microcomputer 410. The serial-format print data DAT1 to DAT4 output to the blocks 21a to 21d of the thermal head 21 are output toward the thermal head 21.

  In parallel with this image reading, in the head control signal generation circuit 160, clocks CLK1 to CLK4 for outputting the print data DAT1 to DAT4 to each heating element 21Z based on a command of the system control microcomputer 410, serial format Latch signals / LAT1 to 4 for converting the print data DAT1 to DAT4 into parallel signals and holding them, and heat generation signals (enable signal, strobe signal / STB) / ENL1 applied to each heat generating element 21Z of each block of the thermal head 21 -4 are generated and these various control signals are output to the thermal head 21.

  The thermal head 21 is provided with an output circuit 72 as shown in FIG. The output circuit 72 uses the four signals, print data DAT1 to DAT4, latch signals / LAT1 to 4, enable signals / ENL1 to 4, and clocks CLK1 to 4, which are input from the head control circuit 100, to generate the thermal head 21. The heating elements 21Z of the respective divided blocks are driven to generate heat in a time-sharing manner.

  That is, serial-format print data DAT1 to 4 input to the thermal head 21 are converted into parallel data by a 1024-bit serial input shift register 75 and held in a latch 76 by latch signals / LAT1 to 4 issued at a predetermined timing. Is done. A predetermined applied voltage Vh supplied from the power supply circuit 140 is applied to one end of each heating element 21Z, and the logical product of the input enable signals / ENL1 to 4 and the data held in the latch 76 generates heat. By inputting to the other end of the element 21Z, the heat generating element 21Z is driven to generate heat at a desired timing.

  As described above, based on the data obtained by reading the original 13, the formation of a punched image on the stencil sheet 23, that is, the plate making, is performed, and then the stencil sheet feed is stopped when a predetermined platen feed amount is fed. Then, when the document 13 is discharged, the document feeding is stopped, and the stencil sheet 23 having been subjected to the plate making is conveyed by a certain amount by the document conveying roller pair 26, and one end thereof is fixed at the clamp portion 32. The stencil sheet 23 is wound around the outer peripheral surface of the drum 33 by rotating the drum 33, wound by a predetermined amount, and then cut by the cutter 31. As a result, the stencil sheet 23 is completely wound around the outer peripheral surface of the drum 33, and the printing operation standby state is entered.

  Next, when the number of prints is input using the numeric keypad 402a, the data is displayed on the display panel 401. When the print start key is depressed in this state, the printing paper 43 is conveyed to the timing roller 42 one by one by the pickup roller 46, and after waiting for the primary standby, the timing roller 42 is driven at a predetermined timing with the rotation of the drum 33. It is sent to the conveyance path 41. The printing paper 43 fed into the conveyance path 41 is pressed against the outer peripheral surface of the drum 33 by the press roller 35 and the ink that has passed through the perforated image formed on the stencil sheet 23 is transferred for printing. The printed printing paper 43 is peeled off from the outer peripheral surface of the drum 33 by the separation claw 39, conveyed in the direction of the arrow Z, and discharged to the paper discharge tray 49.

  In the stencil printing apparatus, several types of stencil sheets having different quality (different prices) can be mounted. Here, when the factor which worsens the unevenness | corrugation degree (smoothness of a film surface) of the base paper surface which is one of the causes of the variation in a punching diameter, the following things were found.

  First, a stencil sheet is manufactured by laminating a film and a support such as Japanese paper with an adhesive, but they are laminated together with a certain tension so as not to cause wrinkles. At this time, if both the elastic moduli are the same, a base paper having a high (smooth) surface smoothness can be produced. Conversely, if the elastic moduli are different, the surface smoothness is low.

  Secondly, the base paper is laminated and wound up into a roll shape, and the roll is wound into a roll shape so that it overlaps with the pressure of Japanese paper on the film surface. As a result, the irregularities of the Japanese paper are reflected on the film surface, and the smoothness of the surface of the film surface is lowered overall. The degree of smoothness at this time also varies depending on the density and material of the Japanese paper.

  For example, if one kind of film and several kinds of Japanese paper are used, a base paper having a good surface condition (good smoothness) or a bad base paper is produced according to the elastic modulus, density, and material difference of the Japanese paper. . In reality, none of the three elements of elastic modulus, density, and material is good or bad Japanese paper, but the base paper with high gloss (reflectance), that is, good smoothness is of high quality. High price and low gloss are low quality and low price.

  On the other hand, when the smoothness of the surface of the stencil sheet is lowered, even if the stencil sheet is pressed against the thermal head at normal pressure, there is a microscopic relationship between one heating element (resistor) of the thermal head and the film surface of the stencil sheet. Since a part with poor adhesion comes out, the heat generation energy of the heating element does not easily reach the film surface of the base paper in this part and the perforation quality is lowered.

  Therefore, in the present embodiment, the plate making pressure of the stencil sheet 23 may be adjusted based on a flowchart as shown in FIG. That is, first, the gloss level (reflectance) of the stencil sheet 23 is detected by the master surface sensor 300 (S1). The glossiness corresponds to the unevenness of the surface of the stencil sheet 23.

  Based on the signal value S1 of the light receiving element 302 obtained by this detection (may be data after A / D conversion), an appropriate plate making pressure to the stencil sheet 23 is determined (S2). For example, as shown in FIG. 8, the lower the glossiness of the stencil sheet 23 is, the higher the platemaking pressure (nip pressure) by the thermal head 21 is increased. In determining the plate making pressure, for example, the system control microcomputer 410 may have a correspondence table between the signal value S1 and an appropriate plate making pressure in advance, and the decision may be made based on this correspondence table.

  Then, the system control microcomputer 410 operates the motor 520 to apply a predetermined turning force around the rotation shaft 518 to the thermal head holding unit 514 so that the stencil sheet 23 is pressed with the determined plate-making pressure. The rotation speed or rotation angle of the motor 520 is set. As a result, the thermal head 21 is pressed toward the platen roller 24, and the determined plate-making pressure is obtained (S3). Then, the stencil sheet 23 is made with this plate making pressure, and then printing is performed (S4).

  If there is a next original 13, the process returns to step 11 (S1) to perform the same processing as above (S5-YES). If there is no next original 13, the process is terminated (S5-NO).

  As described above, according to the apparatus having the above configuration, if the surface state of the stencil sheet 23 is automatically detected by the master surface sensor 300 and the plate making pressure is automatically set, a certain level of punching quality can be obtained regardless of the surface state of the stencil sheet 23. Maintaining can be done reliably. As a result, for example, since the heat generation energy can be sufficiently transmitted even to the stencil sheet 23 whose surface irregularities are severely deteriorated by increasing the plate-making pressure, the same perforation as in the case of using a high-quality stencil sheet It is possible to perform plate making that can reduce image defects such as white spots as much as possible.

  Further, since the plate-making pressure control circuit 180 (plate-making pressure control means) is provided, a configuration in which the user does not have to manually change the plate-making pressure can be achieved.

  In the above embodiment, the surface state of the stencil sheet 23 is automatically detected by the master surface sensor 300 and the platemaking pressure is automatically set. However, manual setting by the user can also be performed. For example, when an automatic detection sensor is not provided, the user may determine the surface state of the stencil sheet 23 and set the plate making pressure. Since the surface deterioration of the stencil sheet 23 directly affects the image quality degradation of the printed image, the quality of the surface state of the stencil sheet 23 is indirectly determined from the print result of the trial printing or the like when the user performs manual setting. By determining the above, information regarding the quality of the stencil sheet 23 may be acquired.

  Further, since the stencil pressure is controlled in accordance with the quality of the stencil sheet 23 detected by the master surface sensor 300, each stencil sheet 23 is punched with the same good quality regardless of the quality of the stencil sheet 23. This can be performed reliably for each stencil sheet.

  In addition, the stencil sheet wound up in a roll shape cannot be wound well unless a strong tension is applied at the beginning of winding. The smoothness of the surface becomes worse. That is, not only the type of the base paper is different, but also the smoothness changes within one base paper, in other words, the surface smoothness of the stencil paper wound up in a roll shape deteriorates with time. . In this case, if the surface state of the stencil sheet 23 is detected by the master surface sensor 300 every time the document 13 is supplied, it is possible to cope with a change in the surface quality over time of one sheet.

  In this case, if the surface state is detected for each main scanning of punching, it is possible to cope with a change in the smoothness of the stencil sheet during the punching process for one original.

  The master surface sensor 300 detects the degree of unevenness on the surface of the stencil sheet (quality of the stencil sheet) at any timing for each roll of the stencil sheet, for each original sheet, or for each main scanning of punching. You may go. Needless to say, the more the opportunities for detection, the finer the perforation quality and print quality can be adjusted.

  Further, in the above embodiment, the stencil sheet 23 is based on the signal value S1 of the light receiving element 302 representing the glossiness (reflectance) of the stencil sheet 23 detected by the master surface sensor 300 corresponding to the smoothness of the surface of the stencil sheet 23. An appropriate plate-making pressure is determined, but the present invention is not limited to this. When the signal value S1 is compared with the reference value and the reflectance is high, the surface state of the stencil sheet 23 is high quality and the reflectance is low. It is good also as a two-stage adjustment which judges that it is low quality and switches plate-making pressure according to the result. Thereby, control of plate-making pressure can be made simpler.

  Further, the plate making pressure may be set in advance in the system control microcomputer 410 according to the type of the stencil sheet 23. Thereby, the control by the plate making pressure control circuit 180 can be simplified. In addition, the master surface sensor 300 can be used to eliminate the need to measure surface irregularities.

  Further, the stencil pressure may be set in the system control microcomputer 410 in advance according to the date of manufacture of the stencil sheet 23. Thereby, similarly, the control by the plate making pressure control circuit 180 can be simplified. In addition, the master surface sensor 300 can be used to eliminate the need to measure surface irregularities.

  Further, the plate making pressure may be set in advance in the system control microcomputer 410 in accordance with the smoothness of the stencil sheet 23. Thereby, similarly, the control by the plate making pressure control circuit 180 can be simplified. In addition, the master surface sensor 300 can be used to eliminate the need to measure surface irregularities.

  Further, in the above embodiment, the smoothness of the film surface as one aspect of the quality of the stencil sheet, in other words, unevenness has been a problem, but the factors that influence the quality of the stencil sheet that cause the variation in perforation diameter are It is not necessarily limited to the smoothness of the film surface. For example, as described above, in the stencil sheet manufacturing process, the film and the support are bonded together with an adhesive, but the perforation diameter may vary depending on the amount of adhesive applied. There are two types of changes in the amount of adhesive applied, one depending on the density (type) of Japanese paper and the other in the manufacturing process. The smaller the coating amount, the better the perforation quality, that is, the variation in the perforation diameter decreases. The larger the application amount, the more difficult the hole is opened, and the variation in the perforation diameter increases. Further, if the coating amount itself varies, naturally, the perforation diameter varies. On the other hand, the light transmittance of the stencil sheet changes according to an increase or decrease in the amount of adhesive applied, which is an aspect of the quality of the stencil sheet. Therefore, by detecting this light transmittance using an optical detection means such as a photosensor and performing the same control as described above according to the detection result, the perforation quality can be homogenized.

  In other words, in the above-described embodiment, the master surface sensor 300 detects unevenness on the surface of the stencil sheet 23 and controls the plate-making pressure in accordance with the unevenness. By controlling the plate making pressure according to the characteristics (quality) of the stencil sheet, which affects the diameter of the stencil when the perforation is formed with the head 21, the same good quality as the stencil sheet regardless of the quality of the stencil sheet It is possible to perform the perforation without shortening the life of the apparatus.

<Examination example>
An example (Example) in which the stencil printing apparatus 1 having the above-described configuration is made into a normal stencil sheet (high quality base paper) and a stencil sheet (low quality base paper) having a large degree of surface irregularity is shown in FIG. Shown in a) and (b). In addition, for comparison, an example (conventional example) in which a conventional stencil printing apparatus made a plate on a normal stencil sheet (high quality base paper) and a stencil sheet (low quality base paper) having a large degree of surface irregularity, They are shown in FIGS. 10 (a) and (b), respectively.

  In the examples, there is no variation in the perforation diameters, whether it is a normal stencil paper (high quality base paper) or a deteriorated stencil paper (low quality base paper) with a large degree of surface irregularities.

  On the other hand, in the conventional example, when a regular stencil sheet (high-quality stencil sheet) is perforated, a substantially uniform perforation diameter is formed. When the quality base paper is perforated, the perforation diameter varies as shown in FIG.

1 Stencil Printing Device 20 Plate Making Writing Unit (Plate Making Device)
21 Thermal Head 21Z Heating Element 23 Stencil Sheet 24 Platen Roller 180 Plate Making Pressure Control Circuit (plate making pressure control means)
300 Master surface sensor (detection means)
508 Plate making pressure applying mechanism (plate making pressure applying means)
510 Plate making pressure variable mechanism (plate making pressure variable means)

Claims (3)

A thermal head in which heating elements are arranged;
A platen roller capable of nipping a stencil sheet with the thermal head;
A plate-making pressure applying unit that nips the thermal head and the platen roller and applies plate-making pressure to the stencil sheet;
Plate making pressure variable means for making the plate making pressure variable by the plate making pressure applying means;
A plate making apparatus characterized by comprising:   2. The plate making apparatus according to claim 1, further comprising a plate making pressure control means for controlling the plate making pressure by the plate making pressure varying means. A detection means for detecting the quality of the stencil sheet,
3. The plate making apparatus according to claim 2, wherein the plate making pressure control means controls the plate making pressure based on a signal received from the detection means.

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