JP4008986B2 - Plate making equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plate making apparatus which is used in a heat sensitive stencil printing apparatus or the like and performs plate making using a heat sensitive stencil master.
[0002]
[Prior art]
As a printing method using a heat-sensitive stencil master, digital heat-sensitive stencil printing has been conventionally known. In this printing, a master called a heat-sensitive stencil master is used, which is made by bonding a thin thermoplastic resin film with a thickness of about 1 to 8 μm to Japanese paper or synthetic fiber as a porous support, or a mixture of these. Laminated structure. An overcoat layer is provided on the surface of the thermoplastic resin film in order to prevent fusion to the surface of the thermal head and to prevent charging. An example of such a master is disclosed in Japanese Patent Laid-Open No. 4-265683.
In this digital thermal stencil printing, the master film surface is heated and punched by a heat generating part such as a thermal head on the basis of the image data of the original image converted into a digital signal, and then this is wound around a plate cylinder. Printing is performed by supplying ink from the inside of the plate cylinder, pressing the printing paper against the plate cylinder with a pressing member such as a press roller, and transferring the ink oozed from the master perforation through the plate cylinder opening to the printing paper. Has been done.
[0003]
By the way, in a master having a porous support made of Japanese paper or the like as described above, there are cases where fibers cross the perforated part due to unavoidable variations in the internal structure. Passing is hindered, and a so-called “fiber pattern” or the like in which a fiber pattern appears in a solid portion of an image occurs.
Further, in printing immediately after the plate making, since the ink must pass through Japanese paper or the like, the start-up of the image is poor, and the occurrence of “damaged paper” that has no use value as a printed material cannot be avoided.
[0004]
For this reason, attempts have been made to perform printing using a master having a thin porous support such as Japanese paper, which is the cause of the above problem, or a master made only of a thermoplastic resin film having no porous support. Yes.
When the master is composed only of the thermoplastic resin film, the problems caused by the porous support can be eliminated, but the strength of the master, so-called low power, is substantially borne by the porous support. In the master (including the thinned porous support), which is substantially composed only of the thermoplastic resin film, the thermal shrinkage characteristic of the thermoplastic resin becomes obvious, and the master shrinks (mainly shrinkage in the sub-scanning direction). In addition, when the thermoplastic resin film is melted, the thermoplastic resin film is welded to the surface of the thermal head, and the problem of sticking that cannot be conveyed at a normal intended distance is increased. For this reason, there is a problem that so-called plate-making wrinkles are generated or image size reproducibility is poor.
[0005]
In the solid image portion where adjacent dots are perforated, the shrinkage and sticking of the master are particularly large.
The reason is as follows.
Feeding in the sub-scanning direction of the master during plate making is performed by rotation of a platen roller that presses the master against the thermal head, and the conveying force is ensured by friction between the surface of the platen roller and the master.
If the friction force between the platen roller and the master is sufficient, the contraction and sticking of the master are suppressed as much as possible due to the constraint by the friction force, but if the solid ratio is high, the friction force between the platen roller and the master is insufficient. Further, the master slides with respect to the platen roller, that is, sticking occurs, and the master shrinkage due to the heat shrinkage characteristic of the thermoplastic resin described above also becomes severe, and as a result, the image dimension reproducibility is deteriorated.
As shown in FIG. 14, the master shrinkage ratio increases as the film perforation diameter (the diameter of the perforated portion of the thermoplastic resin film in the heat-sensitive stencil master) increases.
[0006]
As a solution to this problem, a heat-sensitive stencil making apparatus described in JP-A-8-90747 is known.
This thermal stencil plate making apparatus has a solid rate detecting means for detecting a “solid rate” that is a ratio of a heat generating portion that is actually energized out of all the heat generating portions of the thermal head. A threshold value is provided, and the rotation speed of the platen roller, that is, the plate-making speed is adjusted by making the detected solid rate correspond to the threshold value.
Specifically, when the solid rate is high, the plate making speed is decreased to reduce the diameter of the hole (the diameter of the hole). The reason is as follows.
When the master is perforated, the shrinkage stress of the thermoplastic resin acts in the direction of increasing the diameter of the perforated part, but when the plate making speed is slow, the shrinkage stress is restrained by the pressing force of the platen roller. The drilling diameter is smaller than the standard plate making speed due to the reduction of heat storage effect
.
When the plate making speed is high (in the case of the standard plate making speed), the speed at which the perforated part is released from the pressing force of the platen roller is fast, so the contraction stress acts sufficiently and the thermal head heat storage action increases. As a result, the diameter of the hole is increased.
[0007]
[Problems to be solved by the invention]
By the way, as in the technique described in Japanese Patent Laid-Open No. 8-90747, in the case of a technique for adjusting the plate-making speed by detecting the solid rate, which is the ratio of the heat generating portion that is actually energized among all the heat generating portions of the thermal head. In addition, since the density of the perforated portions is not related, a non-solid image in which the perforated portions are not adjacent is also included when viewed microscopically even at the same solid ratio. That is, a solid image and an image that is not so may be captured at the same solid rate.
If the solid ratio is the same but the solid image is not necessary, it is not necessary to adjust the plate-making speed, but if the plate-making speed is controlled here, the hole diameter becomes too small and the quality of the printed matter such as blurring of characters will be lost. In addition, the plate making speed is controlled to be slow, so that the plate making time becomes long.
[0008]
In this type of printing, the phenomenon of so-called “back-off”, in which the ink on the surface of the previous printing paper is transferred to the back side of the printing paper and causes stains, is a problem. If the boundary between them melts and continues, excessive transfer of ink to the printing paper occurs, which causes set-off.
[0009]
Therefore, the present invention can accurately adjust the plate-making speed corresponding to the image state, has good image size reproducibility, can suppress generation of plate-making wrinkles as much as possible, and can eliminate the problem of set-off, The purpose is to provide a plate making apparatus that can contribute to quality improvement.
[0010]
[Means for Solving the Problems]
In the present invention, in order to accurately recognize a solid image, the positional relationship between the drilled portions is grasped.
Specifically, in the invention of claim 1, the thermal head having a plurality of heat generating portions arranged in the main scanning direction is pressed and brought into contact with the thermal stencil master having at least a thermoplastic resin film, In a plate making apparatus that forms a dot-shaped plate-making image corresponding to image data of a document image on the heat-sensitive stencil master by being moved relatively in a sub-scanning direction orthogonal to the main scanning direction and heating the heat-generating part. The solid state is recognized by a matrix of image signals, and when there are a large number of solid images, a control means for controlling the plate making speed to be slow is provided.
[0011]
The invention described in claim 2 employs a configuration in which, in the configuration described in claim 1, the control means has a high-speed plate-making control mode for maintaining a normal plate-making speed over the entire plate-making.
[0012]
According to a third aspect of the present invention, in the configuration according to the first or second aspect, the thermal head temperature detecting means for detecting the temperature of the thermal head is provided, and the control means detects the thermal detected by the thermal head temperature detecting means. A configuration is adopted in which temperature control is performed to adjust the perforation energy supplied to the thermal head to a predetermined energy in accordance with the head temperature.
[0013]
According to a fourth aspect of the present invention, in the configuration of the first, second, or third aspect, the dimension of the heat generating portion of the thermal head in the main scanning direction is in the range of 30 to 95% of the heat generating portion pitch in the main scanning direction. And the dimension of the sub scanning direction of the said heat-emitting part is taken as the range of 30 to 95% of the sub scanning direction feed pitch of the said heat-sensitive stencil master.
[0014]
The invention according to claim 5 adopts the structure according to claim 1, 2, 3 or 4, wherein the thickness of the glaze layer of the thermal head is 60 μm or less.
[0015]
In the invention described in claim 6, in the structure described in claim 1, 2, 3, 4 or 5, the heat-sensitive stencil master is substantially composed of only a thermoplastic resin film.
[0016]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
First, the overall configuration of a thermal stencil printing apparatus to which the plate making apparatus according to the present invention is applied and its printing process will be briefly described with reference to FIG.
[0017]
Reference numeral 50 denotes an apparatus main body cabinet. A portion indicated by reference numeral 80 in the upper part of the apparatus main body cabinet 50 constitutes a document reading section, a portion indicated by reference numeral 90 below the plate making apparatus according to the present invention, and a portion indicated by reference numeral 100 on the left side thereof is porous. The printing drum portion in which the printing drum 101 is disposed, the portion indicated by the reference numeral 70 on the left of the printing drum portion, the portion indicated by the reference symbol 110 below the plate making apparatus 90 is the portion indicated by the reference numeral 120 below the feeding drum, and the printing drum 101 Indicates a printing part, and a portion denoted by reference numeral 130 in the lower left of the apparatus main body cabinet 50 indicates a paper discharge part.
[0018]
Next, the operation of this heat-sensitive stencil printing apparatus will be described below, including its detailed configuration.
[0019]
First, a document 60 having an image to be printed is placed on a document placing table (not shown) arranged at the top of the document reading unit 80, and a plate making start key (not shown) is pressed. Along with the pressing of the plate making start key, a plate removing process is first executed. That is, in this state, the used heat-sensitive stencil master 61b used in the previous printing remains attached to the outer peripheral surface of the printing drum 101 of the printing drum unit 100.
[0020]
First, when the printing drum 101 rotates counterclockwise and the rear end of the used heat-sensitive stencil master 61b on the outer peripheral surface of the printing drum 101 approaches the plate release roller pair 71a, 71b, the roller pair 71a, 71b While rotating, the rear end of the used heat-sensitive stencil master 61b is scooped up by one of the discharge plate peeling rollers 71b, and the discharge plate roller pair 73a, 73b and the discharge plate peeling roller pair disposed on the left side of the discharge plate peeling roller pair 71a, 71b. While being conveyed in the direction of the arrow Y1 by the pair of ejected conveying belts 72a and 72b spanned between 71a and 71b, it is ejected into the ejected box 74, and the used heat-sensitive stencil master 61b is pulled from the outer peripheral surface of the printing drum 101. It is peeled off and the plate removal process is completed. At this time, the printing drum 101 continues to rotate counterclockwise. The used heat-sensitive stencil master 61 b that has been peeled and discharged is then compressed inside the discharge plate box 74 by the compression plate 75.
[0021]
In parallel with the plate removal process, the document reading unit 80 reads the document. That is, the document 60 placed on a document placing table (not shown) is transported in the directions of arrows Y2 to Y3 by the rotation of the separation roller 81, the pair of front document transport rollers 82a and 82b, and the pair of rear document transport rollers 83a and 83b. It is used for exposure reading. At this time, when there are a large number of documents 60, only the lowermost document is conveyed by the action of the separating blade 84. The rear document transport roller 83a is driven to rotate by a document transport roller motor 83A, and the front document transport roller 82a is passed through a timing belt (not shown) spanned between the transport rollers 83a and 82a. The rollers 82b and 83b are driven to rotate, respectively. When reading the image of the original 60, the reflected light from the surface of the original 60 illuminated by the fluorescent lamp 86 while being conveyed on the contact glass 85 is reflected by a mirror 87 and passed through a lens 88 from a CCD (photoelectric conversion element) or the like. This is performed by entering the image sensor 89. That is, the document 60 is read by a known “reduction-type document reading method”, and the document 60 from which the image has been read is discharged onto the document tray 80A. The electrical signal photoelectrically converted by the image sensor 89 is input to the analog / digital (A / D) converter 20 (FIG. 1) in the apparatus body cabinet 50 and converted into a digital image signal.
[0022]
On the other hand, in parallel with this image reading operation, plate making and plate feeding processes are performed based on the digital signalized image information. That is, the heat-sensitive stencil master 61 set in a predetermined part of the plate-making apparatus 90 is pulled out from a roll state wound in a roll shape, and a platen roller 92 pressing the heat-sensitive stencil master 61 against the thermal head 30; By the rotation of the pair of feed rollers 93a and 93b, the feed rollers are intermittently conveyed to the downstream side of the conveyance path. With respect to the heat-sensitive stencil master 61 transported in this way, a large number of minute heat generating portions arranged in a line in the main scanning direction of the thermal head 30 are sent from the A / D conversion unit 20 to a digital image. The thermoplastic resin film of the heat-sensitive stencil master 61 that selectively generates heat in response to the signal and is in contact with the generated heat generating portion is melt-pierced. In this way, image information is written as a perforation pattern by position-selective melt perforation of the heat-sensitive stencil master 61 according to the image information.
[0023]
The front end of the pre-pressed heat-sensitive stencil master 61a in which image information is written is sent out toward the outer peripheral side of the printing drum 101 by a pair of plate feeding rollers 94a and 94b, and the traveling direction is changed downward by a guide member (not shown). Then, it hangs down toward the expanded master clamper 102 (shown in phantom) of the printing drum 101 in the plate feeding position state shown in the figure. At this time, the used heat-sensitive stencil master 61b has already been removed from the printing drum 101 by the plate discharging process.
[0024]
Then, when the leading end of the plate-making heat-sensitive stencil master 61a is clamped by the master clamper 102 at a fixed timing, the printing drum 101 rotates on the outer peripheral surface while rotating in the direction A (clockwise direction) in the figure. The stencil master 61a is gradually wound. The rear end portion of the plate-making heat-sensitive stencil master 61a is cut into a fixed length by the cutter 95 after the plate-making is completed.
[0025]
When one plate-made heat-sensitive stencil master 61a is wound around the outer peripheral surface of the printing drum 101, the plate-making and plate-feeding steps are finished, and the printing step is started. First, the uppermost one of the printing papers 62 stacked on the paper feed tray 51 is sent in the direction of arrow Y4 toward the feed roller pair 113a, 113b by the paper feed roller 111 and the separation roller pair 112a, 112b. Further, the feed roller pair 113a, 113b is sent to the printing pressure unit 120 at a predetermined timing synchronized with the rotation of the printing drum 101. When the fed printing paper 62 comes between the printing drum 101 and the press roller 103, the press roller 103 that has been separated below the outer peripheral surface of the printing drum 101 is moved upward, whereby the printing drum 101. It is pressed by the pre-pressed heat-sensitive stencil master 61a wound around the outer peripheral surface. In this way, ink oozes out from the perforated portion of the printing drum 101 and the perforated pattern portion (not shown) of the pre-printed heat-sensitive stencil master 61a, and the oozed ink is transferred to the surface of the printing paper 62 to produce a printed image. As a result, an ink image is formed.
[0026]
At this time, on the inner peripheral side of the printing drum 101, ink is supplied from the ink supply pipe 104 to the ink reservoir 107 formed between the ink roller 105 and the doctor roller 106, and is in the same direction as the rotation direction of the printing drum 101. Ink is supplied to the inner peripheral side of the printing drum 101 by the ink roller 105 that is in contact with the inner peripheral surface while rotating in synchronization with the rotation speed of the printing drum 101. The ink is a W / O type emulsion ink.
[0027]
The printing paper 62 on which a printing image is formed in the printing pressure unit 120 is peeled off from the printing drum 101 by the paper discharge peeling claw 114 and sucked by the suction fan 118, while the suction paper discharge inlet roller 115 and the suction paper discharge outlet roller. By the rotation of the conveyor belt 117 stretched around 116 in the counterclockwise direction, the conveyor belt 117 is conveyed toward the sheet discharge unit 130 as indicated by an arrow Y5 and sequentially discharged and stacked on the sheet discharge table 52. In this way, so-called trial printing is completed.
[0028]
Next, when the number of prints is set with a numeric keypad (not shown) and a print start key (not shown) is pressed, the steps of paper feeding, printing, and paper discharge are repeated for the set number of prints in the same process as the above-described trial printing. All the processes of stencil printing are completed.
[0029]
Next, the plate making apparatus 90 will be described in detail with reference to FIG. 1 which is a control block diagram. As shown in FIG. 1, a plate making apparatus 90 having a plate feeding function has a control means 24 composed of a microcomputer. The control means 24 controls the stepping motor 26 that rotationally drives the thermal head 30 and the platen roller 92.
The image signal converted into a digital signal by the A / D conversion unit 20 is input to the image processing unit 22, and the image signal processed by the image processing unit 22 is input to the control unit 24. The image signal input to the control means 24 may not be read by the CCD but may be from a contact sensor or the like.
[0030]
The image signal input to the control means 24 is used for heat history control, common drop correction control, and various signal controls to the thermal head 30 that are already known.
The control means 24 forms a 48 × 48 dot matrix based on the input image signal, and recognizes that the matrix is solid when the entire matrix is to be drilled. Then, solid image state data such as how much the solid state is in the main scanning direction and the sub-scanning direction and how close the solid state is is created. The ROM (not shown) as a part of the control means 24 stores optimum relation data between the solid image state and the plate making speed obtained in advance by experiments or the like. The control means 24 stores the optimum relation data in the ROM. The optimum plate making speed is determined by applying the solid image state data extracted based on the image signal and created based on the image signal.
[0031]
The control means 24 drives the stepping motor 26 and the thermal head 30 to obtain the determined plate making speed. As a result, the heat-sensitive stencil master 61 is melt-drilled while being fed at a plate-making speed with good image size reproducibility.
In this embodiment, the plate-making speed is set to two levels of normal 1.5 ms / line and 3.0 ms / line when there are many solid images, and four 48 × 48 dot matrices are arranged in the main scanning direction. When 32 or more are adjacent in the sub-scanning direction, the plate making speed is reduced from 1.5 ms / line to 3.0 ms / line by the control means 24.
The stepping motor 26 as the plate making speed adjusting means may be another motor. In addition, the plate making speed is not limited to two stages, and may be set in multiple stages, for example, 16 stages. The matrix may be set finely such as 24 × 24 dots, not 48 × 48 dots, or may be set coarsely.
[0032]
In this embodiment, the original image is read, the solid image is recognized based on this, the plate making speed is determined, and then the plate making is performed at the determined plate making speed, but the solid image state is read while reading the original image. May be recognized to determine the plate-making speed.
Further, in this embodiment, a large number of heat generating parts arranged in the main scanning direction of the thermal head 30 are divided into two blocks and driven for each block, and solid image recognition by the matrix and plate making speed based on the recognition are performed. Is also determined for each block.
Even when the thermal head 30 is driven for each block, the solid image recognition and the plate making speed may be determined in total.
[0033]
Next, the effect when the plate making speed is lowered will be described with reference to FIGS. FIG. 3 shows the surface temperature distribution of the thermal head 30 corresponding to the heat generating portion 32 when the plate making speed is 1.5 ms / line (normal case) and 3.0 ms / line (slow case). Is.
The shape of the perforated portion when the plate making speed is 3.0 ms / line is shown in FIG. ₁ The shape of the perforated part when the plate making is performed at a plate making speed of 1.5 ms / line is h shown in FIG. ₂ It is.
From this, it can be seen that the diameter of the perforated portion can be reduced by lowering the plate making speed. The reason is that, as described above, when the plate making speed is low, the contraction stress of the master is restrained by the pressing force of the platen roller 92. In addition to this, as shown in FIG. This is because the transition of the peak temperature of the heat generating portion 32 in the thermal head 30 during continuous printing differs depending on whether the platemaking speed is fast (1.5 ms / line) or slow (3.0 ms / line). That is, when the plate making speed is high, the heat storage action on the glaze layer 36 of the thermal head 30 to be described later increases, which acts to increase the diameter of the perforations.
[0034]
As described above, if the solid state is recognized with high accuracy in a matrix and the plate making speed is slowed down when there are many solid images, the problems pointed out in the prior art can be eliminated, and high-precision image quality can be eliminated. Can be obtained.
Also, by reducing the diameter of the perforated part in the solid part, the boundary of the perforated part becomes fine without melting and connecting (independence of the perforated part), so the amount of ink transferred to the printing paper is also suppressed and the problem of set-off Will be resolved at the same time.
[0035]
Here, when there are many solid images, the control for slowing the plate making speed to 3.0 ms / line is referred to as “high-precision image quality control mode”. In addition to this high-precision image quality control mode, the control means 24 in the present embodiment has a “high-speed plate-making control mode” in which plate-making is performed at a normal plate-making speed (1.5 ms / line) throughout the plate-making (invoiced). Item 2) When there is no instruction from the operator, the high speed plate making control mode is executed as the standard mode.
The high-accuracy image quality control mode is executed only when the high-accuracy image quality setting key 28 provided on the operation panel 25 shown in FIG. 1 is pressed. In such a case, the high-accuracy image quality display lamp 29 (LED) is turned on. It is like that.
[0036]
A single control method in which all plate making is performed in the high-accuracy image quality control mode may be used. However, if the operator can select as described above, image size reproducibility can be achieved in the case of multicolor printing or color printing. It is possible to prevent the generation of wasted time in plate-making work by using the high-precision image quality control mode that is good and has little set-off, and in other cases, the high-speed plate-making control mode is intended to shorten the plate-making time. A highly practical plate-making apparatus can be obtained.
[0037]
Next, the superiority of the solid state recognition method using the matrix in this embodiment will be described.
As in the prior art described in Japanese Patent Application Laid-Open No. 8-90747, when the processing is performed with a solid rate that is the ratio of the number of heat generating parts that are actually energized in the total number of heat generating parts, the density of the perforated portions is not related. %, The solid image 10 shown in FIG. 6A and the stripe image 12 shown in FIG. 7A can be grasped together. In the case of the solid image 10, when viewed microscopically, as shown in FIG. 6B, the perforated portion h is in the adjacent perforated state, and in the case of the stripe image 12, when viewed microscopically, FIG. As shown in (b), the perforated points h are present in a perforated state at intervals of one dot. To explain with an easy-to-understand example, if there is a thermal head that can print 10 dots, it is the difference between one that has 5 dots perforated continuously and one that has 5 dots drilled at 1-dot intervals. In both cases, the print rate is 50% with 5/10 dots.
Master shrinkage and sticking due to heat shrinkage characteristics of the thermoplastic resin film become intense when perforated with adjacent dots such as the solid image 10, and in such a case, as shown in FIG. Thus, a plate making wrinkle 10a is generated. Therefore, in such a case, it is necessary to slow down the plate making speed.
[0038]
On the other hand, in the punched state such as the stripe image 12, the master contraction and sticking do not actually occur, and even if they occur, it is a level that does not cause a problem in use. Even in such a perforated state, as long as the printing rate of 50% has been recognized, the conventional technology performs control to reduce the plate making speed in the same manner as the solid image 10. In such a case, the influence of adjacent dots is small, the diameter of the punched portion becomes too small, and in the worst case, the punched state becomes unperforated, and the quality of the printed matter is significantly lowered. In addition, the plate making time becomes longer due to unnecessary deceleration control.
[0039]
Next, the thermal head 30 will be described in detail.
In this embodiment, the thermal head 30 is a flat type, and the heat generating portion is a rectangular type. In addition, the thermal head 30 may be a partial glaze type or an end face type, and the heat generating part may be a heat concentrated type.
As shown in FIG. 9, the dimension of the heat generating part 32 is such that the dimension x in the main scanning direction of the heat generating part 32 is less than the pitch p (63.5 μm in this embodiment) of the heat generating part 32 in the main scanning direction. If the dimension y of the heat generating portion 32 in the sub-scanning direction is set to be equal to or smaller than the pitch p of the heat generating portion 32, the drilling portion of the heat-sensitive stencil master 61 can be miniaturized and made independent.
[0040]
The dimension x in the main scanning direction of the heat generating part 32 is set to 95% or less of the pitch p between the heat generating parts 32 in the main scanning direction, and the dimension y in the sub scanning direction is 95 of the feed pitch in the sub scanning direction of the heat sensitive stencil master 61. If it is less than or equal to%, refinement and independence of the perforated part is further improved.
Further, the dimension x in the main scanning direction of the heat generating part 32 is set in a range of 30 to 95% of the pitch p of the heat generating parts 32 in the main scanning direction, and the dimension y in the sub scanning direction is set in the sub scanning direction of the heat-sensitive stencil master 61. If it is in the range of 30 to 95% of the feed pitch (Claim 4), the refinement and independence of the perforated part is further improved, and it is particularly effective for the above-mentioned problems of image size reproducibility and set-off. .
[0041]
The dimension x in the main scanning direction of the heat generating part 32 is less than 30% of the pitch p of the heat generating part 32 in the main scanning direction, or the dimension y in the sub scanning direction of the heat generating part 32 is 30 of the feed pitch in the sub scanning direction of the master. If it is less than%, the perforation diameter is too small, or perforation failure occurs, resulting in poor solid filling in the printed image.
Further, the dimension x in the main scanning direction of the heat generating part 32 exceeds 95% of the pitch p of the heat generating part 32 in the main scanning direction, or the dimension y in the sub scanning direction of the heat generating part 32 is the feed pitch of the master in the sub scanning direction. If it exceeds 95%, the perforation diameter is too large and it is difficult to obtain the independence of the perforations, resulting in poor image size reproducibility or an increase in the amount of ink transferred to the printing paper.
From this viewpoint, in this embodiment, the dimension x in the main scanning direction of the heat generating portion 32 is 20 μm (31%), and the dimension y in the sub-scanning direction is 30 μm (47%).
[0042]
FIG. 10 is a sectional view of the periphery of the heat generating portion 32 of the thermal head 30 in this embodiment.
In FIG. 10, reference numeral 33 denotes a protective film layer, 34 denotes an aluminum electrode, 35 denotes a heating resistor layer, 36 denotes a glaze layer, 37 denotes a ceramic substrate, and 38 denotes an aluminum heat sink.
In a known facsimile or the like using a thermal head, the glaze layer 36 is used as a heat insulating layer so that the heat generated in the heat generating part of the thermal head does not escape downward, and the thickness thereof is about 65 μm or more.
On the other hand, in the present embodiment, in order to reduce the heat storage action in the glaze layer 36, the thickness of the glaze layer 36 is set to 60 μm or less, preferably 20 to 60 μm (based on experimental data). It is set to 40 μm (Claim 5). This is because the thinning of the glaze layer 36 is very effective for obtaining the fine and independent perforated state described above.
[0043]
Next, an embodiment corresponding to claim 3 will be described with reference to FIGS. The same parts as those in the above embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.
In the present embodiment, as shown in FIG. 11, the plate making apparatus 90 has a thermistor 15 as a thermal head temperature detecting means. In FIG. 11, reference numeral 13 denotes an aluminum heat radiation support plate, 14 denotes a thermal head substrate, and 16 denotes a conductive film portion, that is, a linear heat generating portion accommodating portion.
The temperature detection location of the thermal head 30 is preferably close to the surface portion of the heat generating portion, for example, the surface portion in the center of the heat generating portion surrounded by the electrodes, but detection at that portion is impossible with the current technology. In this case, the temperature is detected on the thermal head substrate 14 here. The location of the thermistor 15 is not limited to the location on the thermal head substrate 14 and may be provided inside the aluminum heat radiation support plate 13.
The temperature detected by the thermistor 15 is output to the control means 24 as shown in FIG. A ROM (not shown) in the control means 24 stores optimum relationship data between the temperature and the energization pulse width obtained in advance by experiments or the like. The control means 24 extracts this data from the ROM and outputs it from the thermistor 15. An optimum energization pulse width is determined by applying the output temperature. The control means 24 supplies the drilling energy to the thermal head 30 via the power supply (not shown) with the energization pulse width.
[0044]
FIG. 13 shows the perforation energy supplied from the control means 24 to the thermal head 30 in terms of energization pulse width. As already known thermal history control and common drop correction control, the second energization pulse width 17 is set to 40 to 95% of the first energization pulse width 16.
[0045]
The control means 24 of the plate making apparatus in this embodiment also performs “temperature control” by detecting the temperature of the thermal head 30 when performing the above-described high-precision image quality control mode and high-speed plate making control mode. When there is no instruction from the operator, the high speed plate making control mode is executed as the standard mode.
The temperature control is executed in the above-described two control modes, and a control mode that immediately responds to the type of printing, the work status, and the work environment is selected from the two control modes.
Although the perforation energy is adjusted by changing the energization pulse width, the perforation energy may be adjusted by changing the value of the current flowing through each heat generating part of the thermal head 30 or the voltage value applied to the heat generating part.
[0046]
Further, the heat-sensitive stencil master 61 in each of the above embodiments may be substantially composed only of a thermoplastic resin film (claim 6).
[0047]
【The invention's effect】
According to the first aspect of the present invention, since the solid state of the original image is recognized using a matrix and the plate-making speed is reduced when there are many solid images, the solid state can be accurately recognized, The perforated portion of the solid image portion can be made independent and fine, thereby suppressing the master shrinkage and preventing the generation of the plate making wrinkles and obtaining the good reproducibility of the image size. .
At the same time, since the diameter of the perforated portion can be reduced, excessive transfer of the ink to the printing paper can be suppressed and set-off can be prevented.
[0048]
According to the invention described in claim 2, in addition to the high-precision image quality control mode of claim 1, in addition to the effect of claim 1, in addition to the effects of claim 1, the quality of the printed matter is improved. Accordingly, waste of plate making time can be eliminated by properly using the control mode.
[0049]
According to the third aspect of the present invention, in addition to the two control modes of the second aspect, the temperature control based on the temperature of the thermal head is further performed. Since control such as plate-making wrinkle control can be performed, it is possible to achieve control that responds quickly to changes in the working environment and the like.
[0050]
According to the invention described in claim 4, since the dimension of the heat generating portion of the thermal head is defined within a practically effective range, the accuracy of independence and miniaturization of the drilled portion can be further improved. The effect of 1 can be further enhanced.
[0051]
According to the invention described in claim 5, since the thickness of the glaze layer of the thermal head is limited to be thin, the adverse effect on the perforated state due to heat storage in the glaze layer can be suppressed, and the effect of claim 1 can be further enhanced. .
[0052]
According to the sixth aspect of the present invention, since the heat-sensitive stencil master is substantially composed only of the thermoplastic resin film, the effect of the first aspect can be obtained without causing the so-called fiber phenomenon.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a control configuration of a plate making apparatus according to an embodiment of the present invention.
FIG. 2 is an overall schematic diagram of a thermal stencil printing apparatus to which a plate making apparatus according to an embodiment of the present invention is applied.
FIG. 3 is a graph showing the surface temperature distribution of the thermal head when the plate making speed is slow and when it is not slow.
FIGS. 4A and 4B are diagrams showing the shape of a perforated portion in a solid portion, where FIG. 4A shows a case where the plate-making speed is slowed down, and FIG.
FIG. 5 is a graph showing the transition of the peak temperature of the heat generating part of the thermal head when the plate making speed is slow and when it is not slow.
6A and 6B are diagrams showing a perforated image, in which FIG. 6A is a solid part, and FIG.
7A and 7B are diagrams showing a perforated image, in which FIG. 7A is a stripe image, and FIG.
FIG. 8 is a diagram illustrating a state in which plate-making wrinkles are generated in a solid image.
FIG. 9 is a plan view of a heat generating portion of the thermal head.
FIG. 10 is a cross-sectional view of a main part of the thermal head.
FIG. 11 is a side view showing the location of the thermistor that detects the temperature of the thermal head.
FIG. 12 is a block diagram illustrating a control configuration of a plate making apparatus according to another embodiment.
FIG. 13 is a diagram showing energization pulse widths adjusted by thermal history control and common drop correction control.
FIG. 14 is a graph showing a relationship between a film perforation diameter and a master shrinkage rate.
[Explanation of symbols]
15 Thermistor as thermal head temperature detection means
24 Control means
32 Heating part
36 glaze layer
61 heat-sensitive stencil master

Claims (6)

A thermal head having at least a thermoplastic resin film is pressed and brought into contact with a thermal head having a large number of heating portions arranged in the main scanning direction, and is relatively in the sub-scanning direction perpendicular to the main scanning direction. In a plate making apparatus that forms a dot-shaped plate-making image corresponding to image data of a document image on the heat-sensitive stencil master by moving and heating the heating unit,
A plate making apparatus comprising a control means for recognizing a solid state of a document image by a matrix of image signals and controlling so as to reduce a plate making speed when there are many solid images. The plate making apparatus according to claim 1,
A plate making apparatus, wherein the control means has a high speed plate making control mode for maintaining a normal plate making speed over the whole plate making. In the plate-making printing apparatus according to claim 1 or 2,
A thermal head temperature detecting means for detecting the temperature of the thermal head;
The plate making apparatus, wherein the control means performs temperature control for adjusting the perforation energy supplied to the thermal head to a predetermined energy in accordance with the thermal head temperature detected by the thermal head temperature detecting means. In the plate making apparatus according to claim 1, 2, or 3,
The size of the heat generating portion of the thermal head in the main scanning direction is in the range of 30 to 95% of the pitch of the heat generating portion in the main scanning direction, and the size of the heat generating portion in the sub-scanning direction is that of the heat sensitive stencil master. A plate making apparatus characterized by being in the range of 30 to 95% of the feed pitch in the sub-scanning direction. In the plate making apparatus according to claim 1, 2, 3, or 4,
A plate making apparatus, wherein the thickness of the glaze layer of the thermal head is 60 μm or less. In the plate making apparatus according to claim 1, 2, 3, 4 or 5,
A plate-making apparatus, wherein the heat-sensitive stencil master consists essentially of a thermoplastic resin film.

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