JP2000127332A - Apparatus and method for plate-making for stencil printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain good resolution without breaking a fine letter in the case of printing an image of a small letter size on a sheet having good water absorbency. SOLUTION: A thermal head 8 has a plurality of heating elements corresponding to an image of image data and forms punched holes of a predetermined diameter on a stencil base sheet by heating the elements. When an operating unit 1 selects a fine letter mode, a history pattern detecting means 4 detects a pixel disposed at a profile of the image of the data, and variably controls an applying time of a voltage to corresponding element so as to reduce the diameter of the hole of the pixel. First and second pulses outputted from first and second pulse generators 5, 6 have different applying times of voltages, switched by a selector 7 based on the control of the means 4 and supplied to the head 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stencil printing machine for printing a stencil sheet by thermal stencil printing using a thermal head, and more particularly to a stencil printing machine using fine prints of an image or fine prints having good water absorption. The present invention relates to a stencil making machine and a stencil making machine capable of eliminating crush.

[0002]

2. Description of the Related Art A stencil making machine for a stencil printing machine applies a perforation pattern corresponding to a document image to a stencil sheet. There are various plate making methods, and a thermal plate making using a linear thermal head (hereinafter, referred to as TPH) is widely used. This TPH
Will be described. The TPH has a large number of heating elements extending in the width direction (main scanning direction) of the roll-shaped stencil sheet, and heats the heating element corresponding to an image to form perforations in the stencil sheet. Then, while feeding the roll-shaped stencil sheet in the sub-scanning direction orthogonal to the main scanning direction,
By repeating the heat generation, a perforation pattern corresponding to the document image is applied to the stencil sheet.

When viewed finely, an image on a stencil sheet is formed by punching a plurality of dots. In each part of the image, a plurality of dots are perforated in the main scanning and sub-scanning directions. For example, it is composed of dots located at the contours of the character and internal dots located between the contours.

In stencil making of a stencil sheet by TPH, when perforating the upper part and both ends of a continuous black portion such as characters and solids, it is colder than when perforating the inside of black. Therefore, if the contour energy (except for the lower part) of the character and the internal perforation energy are the same, the perforation diameter will differ.

FIG. 6 is a diagram showing a state of conventional heat history control. FIG. 7A is a timing chart showing a pulse width applied to the heating element of the TPH, and FIG. 7B is a diagram showing a printing state of a solid portion of an image. Conventionally, the voltage application time (first pulse) of the black contour portion is lengthened and the inside of the black portion (second pulse) is shortened so that the perforation diameter of the contour portion (referred to as a solid contour portion) and the inner (solid inside) are reduced. Control is performed so that the perforation diameter is constant (same). This thermal history control of TPH is generally well known.

[0006]

The ink of the stencil printing machine has such characteristics that it easily passes through the perforations of the stencil sheet, and penetrates the printing paper and is fixed by evaporation of water. Therefore, the ink that has passed through the perforations of the stencil sheet becomes wider than the diameter of the perforated portion. Therefore, the finer the character, the easier it is to absorb the paper, such as a postcard, a postcard, or the like. The heat history control is performed to sharpen the contour. However, in the case of a paper having good permeability such as a postcard or a post-paper, the ink bleeds at the contour portion with a normal perforation diameter.

FIG. 7 is a view showing a state in which the fine characters are crushed. FIG. 1A shows a perforated state of a stencil sheet when a predetermined image (in the illustrated example, the character "") is subjected to the thermal history control, and FIG. The printed state is shown. As shown in FIG. 3A, the image is perforated with a constant perforation diameter by the above-described thermal history control. Then, in the printing state after the plate making, as shown in FIG. 3B, the character of the “ta” is particularly difficult to identify due to the spread of the ink due to the collapse of the inside.

As described above, when the above-mentioned thermal history control is performed, when printing is performed on a sheet having good absorbency using a document having many characters with small character sizes, the gap between the lines is destroyed and the resolution is reduced. The problem of worsening is likely to occur

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended for a stencil printing machine capable of obtaining good resolution without crushing fine characters when an image having a small character size is printed on paper having good water absorbency. It is an object to provide a plate making apparatus and method.

[0010]

According to the present invention, in order to achieve the above object, a thermal head having a plurality of heating elements is used, and the stencil sheet is perforated by the heat generated by the heating elements. In the stencil making machine for forming a stencil printing machine,
Among the pixels forming the image data, the pixels located inside the image and the pixels located at the outline of the image are respectively detected, and the perforation diameter of the pixels of the outline is smaller than the perforation diameter of the pixels inside. In this case, a means for variably controlling the energy applied to each heating element is provided.

In addition, as described in claim 2, the apparatus may be provided with means for detecting the internal pixels and the pixels of the outline based on the thermal history of each heating element of the thermal head.

According to a third aspect of the present invention, as means for variably controlling the energy applied to the heating element, a pulse voltage generating means for variably supplying a voltage application time to the heating element is provided. Is also good.

According to a fourth aspect of the present invention, the variable control of the applied energy can be executed when the temperature is equal to or higher than a predetermined temperature set in advance based on the temperature characteristics of the ink used for printing.

According to a fifth aspect of the present invention, there is provided a thermal head having a plurality of heating elements for forming perforations in a stencil sheet by the heat generated by the heating elements, and forming image data based on the heat history of each of the heating elements. Pixels located inside the image and pixels located at the outline of the image are detected,
A history pattern detection unit that controls switching of applied energy to each heating element so that a perforation diameter of a contour portion of the image is smaller than a perforation diameter of a pixel inside the image, and a reference is made to pixels inside the image. A second energy generating means for generating an applied energy for piercing with a predetermined piercing diameter, and generating an applied energy for piercing a pixel at the contour of the image with a smaller piercing diameter than the reference piercing diameter. A heating element of the thermal head corresponding to one of the applied energies output from the first or second energy generating means based on switching control of the first energy generating means and the history pattern detecting means. And a selector for switching the supply to the power supply.

[0015] The history pattern detecting means may be provided with an operation section for setting whether or not to control the applied energy to the heating element.

According to a seventh aspect of the present invention, there is provided a plate making method for a stencil printing machine that uses a thermal head having a plurality of heating elements to form perforations in a stencil sheet by the heat generated by the heating elements. Among the pixels forming the image data, the pixels located inside the image and the pixels located at the outline of the image are respectively detected, and the perforation diameter of the pixels of the outline is smaller than the perforation diameter of the pixels inside. In this case, the applied energy to each heating element is variably controlled.

According to the above configuration, the history pattern detecting means 4 detects a pixel at the contour of the image and reduces the energy applied to the heating element of the corresponding thermal head 8 so that the perforation diameter of this pixel becomes smaller than the others. Variable control. This allows
Even when a fine-text document is printed on a sheet of water-absorbent paper, the amount of ink passing through the perforations is suppressed, and the outline of the image can be clearly displayed without the occurrence of fine-text collapse.

[0018]

FIG. 1 is a block diagram showing a circuit configuration of a stencil printing machine of the present invention. Operation unit 1
Is provided on a panel of a stencil printing machine, and performs various operations and settings for stencil making and printing operations. This operation unit 1
Is provided with a fine character key for setting a fine character mode, which will be described later, so as to be selectable from, for example, a displayed menu screen.
The control means 2 is constituted by a CPU, and controls the stencil printing operation based on the operation settings of the operation unit 1. In this printing operation, the printing operation is controlled in a set mode, that is, one of the above-described thermal history control (normal mode) and the fine print mode.

The image processing section 3 converts the image data of the document read from an external input or via a scanner of the apparatus into one.
A predetermined image processing is performed line by line and output. The history pattern detection unit 4 patterns input image data based on history control (details will be described later) corresponding to the set mode, and outputs a corresponding switching signal to the selector 7. The history pattern detection unit 4 includes a storage unit (not shown) that stores a past heat generation state for each pixel. The history pattern detection unit 4 according to this embodiment performs
The line portion is stored in the storage unit while being constantly updated.

The selector 7 receives a first pulse generating circuit 5 based on the switching signal output from the history pattern detecting means 4.
And the second pulse output from the second pulse generation circuit 6 is selected and output to the TPH 8. The TPH 8 is constituted by a thermal head, and is constituted by a plurality of heating elements arranged in the width (main scanning) direction of the stencil sheet. Then, a heating element corresponding to each dot of the image data is heated based on one of the selected first and second pulses, and the stencil sheet is subjected to thermal plate making line by line.

The first pulse output from the first pulse generating circuit 5 is set so as to supply an applied energy necessary for forming a solid contour portion. The first pulse is
A predetermined voltage is set to be applied for a predetermined time. Second
The second pulse output from the pulse generation circuit 6 is set to the applied energy (voltage application time) required to form a hole in the solid.

The application time of the voltage of the first pulse output from the first pulse generation circuit 5 differs between the normal mode and the fine mode. In the normal mode described above, assuming that the voltage application time in the second pulse generation circuit 6 is a reference value (100%), a time period (125%) longer than the voltage application time in the second pulse generation circuit 6 is set. ing. In the fine print mode, a time (105%) slightly longer than the reference value (100%) is set.

FIG. 2 is a diagram showing output states of the first pulse and the second pulse. FIG. 3A is a timing chart showing pulse widths output from the pulse generation circuits 5 and 6. As shown in this figure, the application time of the voltage of the first pulse is the application time (125%) in the normal mode.
And the application time of the second pulse generation circuit 6 (1
00%) within a longer period.

An example of the solid portion of the image shown in FIG. The solid portion is composed of a solid portion of 3 × 3 pixels (dots) and is adjacent to one pixel with a white pixel therebetween, as shown in FIG. In this case, the first pulse is used for the solid outline, and the second pulse is used for the inside of the solid. In the figure, the difference in the size of the black pixel indicates that these are different pulses.

It should be noted that the image data is subjected to plate making by sequentially performing main scanning one line at a time from the top. Pixels located one line before (a side in the sub-scanning direction, the upper part of the drawing) a pixel to be made, and It is determined which of the first pulse and the second pulse is applied to the pixel based on the state of the three pixels of the left and right pixels. That is, in the example shown in FIG. 3B, when all the three pixels on the front side in the sub-scanning direction one line are black, the heating pixel is controlled by the second pulse, and the heating pixel is located on the front side in the sub-scanning direction of the heating pixel. When any of the three pixels one line before is white, the heat generation of this heat generation pixel is controlled by the first pulse.

FIG. 3 is a flowchart showing the mode switching operation by the control means 2. When the small character key is selected on the operation unit 1 (S1-YES), the control unit 2 determines that the mode is the small character mode. Then, the application time of the voltage in the first pulse output from the first pulse generation circuit 5 is set to the value (105%) in the fine character mode (S2). On the other hand, when the fine character key is not selected (S1-NO), the control unit 2 determines that the normal mode is set, and sets the application time of the voltage of the first pulse to the value in the normal mode (125%) (S1).
3). After the setting, the stencil making operation of the stencil sheet by the TPH 8 is enabled (S4).

FIG. 4 is a flowchart showing the control contents of the history pattern detecting means 4 in the fine print mode. At this time, in the first pulse generation circuit 5, the application time of the voltage is set to 105% corresponding to the fine character mode. At the time of plate making (T1), the image processing unit 3 inputs a document image line by line. The image in one main scanning line is separated by the image processing unit 3 into a heating pixel (black) or a non-heating pixel (white). Also,
The TPH 8 has heating elements corresponding to these pixels along the width direction of the stencil sheet (for one line of the image data). Then, the heat generating element in the heat generating pixel portion generates heat to form a hole in the stencil sheet.

At this time, the input one-line image data is further detected as a target pixel for each pixel, and the heat generation is controlled based on the past heat generation state (history) of the target pixel. If a certain pixel of interest is a heat-generating pixel (black) (T2-YES), the heat generation amount of this pixel of interest is determined based on the past heat generation history of this pixel of interest (black).
Control.

For example, one of three pixels (dots) consisting of a pixel one line before the target pixel (black) in the sub-scanning direction and both pixels adjacent in the main scanning direction is a non-heat-generating pixel (white). In this case (T3-YES), it is determined that the heating element is cold, and the heating element corresponding to the pixel of interest (black) is set to the first.
Plate making is performed using a pulse (T4). Specifically, the history pattern detecting means 4 controls the selector 7 to select the first pulse, and causes the TPH 8 to generate heat with the voltage application time of 105% output from the first pulse generation circuit 5.

At T3, the target pixel (black)
If there is no non-heat-generating pixel (white) in the three dots of the previous line (T3-NO), it is determined that the heat-generating element is in a heat-generating state, and the heat-generating element corresponding to the pixel of interest (black) is determined to be the second. Plate making is performed using a pulse (T5). More specifically, the history pattern detecting means 4 controls the selector 7 to select the second pulse and switches the TPH 8 with the voltage application time of 100% (reference value) output from the second pulse generating circuit 6. Generate heat.

On the other hand, if the pixel of interest is a non-heat-generating pixel (white) at T2 (T2-NO), the heating element corresponding to this pixel of interest does not generate heat and is not perforated. That is,
The history pattern detecting means 4 does not select any of the first and second pulses for the selector 7 and selects the T corresponding to the pixel of interest.
Do not generate heat from the heating element of PH8.

Next, in the one line of image data, the pixel of interest is moved to the next pixel (T7). When the prepress for one line in the main scanning is completed, the prepress for the next second line is executed. Stencil making for the second and subsequent lines is performed by moving the stencil sheet or TPH8 in the vertical direction of the stencil sheet by the distance of one line (sub-scan). Then, when the main scanning and the sub-scanning of the input image data are completed (for example, plate making for one stencil sheet) (T8-YES), the plate making operation is finished.

FIG. 5 is a diagram showing an image obtained in the fine print mode. FIG. 1A is a diagram illustrating a perforated state of a stencil sheet, and FIG. 2B is a diagram illustrating a printing state (image state after passing ink). As shown in FIG. 3A, the outline of the character is perforated by a first pulse, and the inside is perforated by a second pulse. Due to heat generation during the reference voltage application time (100%) using the second pulse, the inside of the solid is pierced with a predetermined diameter (portion having a large diameter in the figure).

In contrast, the first in the solid outline portion
The pulse voltage application time (105%) is slightly longer than that of the second pulse, but is slightly smaller than the diameter of the perforation in the second pulse because the heating element is in a cold state immediately before. It is perforated. Thus, the solid outline is
In each case, since the holes are perforated with a smaller diameter than the inside, the amount of ink ejected from this contour portion is suppressed as shown in FIG. .

In the plate making in the fine print mode, in particular,
The operator selects and executes the operation on the operation unit 1 in a state in which fine characters are likely to be crushed, such as when a document with many fine characters, a font with a small size is frequently used, or a sheet with good absorbency is used. In the case of printing a document in which fine characters are not lost, for example, in the case of a document that does not include extremely fine characters (fine characters), plate making and printing may be performed in the normal mode.

The stencil making apparatus of the present invention is provided, for example, inside a stencil printing machine, and has a configuration in which a stencil sheet made by stencil is automatically applied to a plate cylinder of the printing machine to enable printing. In a stencil printing machine incorporating such a stencil making device, the stencil making mechanism and the printing mechanism operate under the same environment (for example, temperature and humidity).

Here, the ink (eg, emulsion ink) used at the time of printing has a predetermined temperature characteristic. That is, when the temperature is as low as 10 degrees or less, the permeability to the printing paper decreases. In such a low-temperature environment, printing using the stencil sheet made in the fine print mode causes a reduction in quality. At the time of this low temperature, it is desirable that the plate making and printing can be performed only in the normal mode.

Therefore, the stencil printing machine may be provided with a temperature sensor so that the fine print mode cannot be selected on the menu screen displayed on the operation unit 1 when a low temperature is detected. At the same time, a configuration may be adopted in which guidance indicating that selection is not possible is displayed on the menu screen of the operation unit 1. Also, even when the plate making device and the printing device are installed separately and separately,
When printing is performed immediately after plate making, similar conditions occur. In this configuration, a temperature sensor may be provided in the plate making apparatus so that plate making can be performed only in the normal mode when the temperature is low.

In the above-described embodiment, the normal mode and the fine print mode are switched by operating the operation unit 1. When each mode is set, the plate making device executes the corresponding heat generation control on the entire surface of the original. Configuration. Not limited to this,
The entire original may be perforated by the heat generation control in the normal mode, and only the area including the fine character may be perforated by the heat generation control in the fine character mode. Specifically, a configuration may be employed in which a range of a small character area is designated and input to the image processing unit 3 or a configuration in which the image processing unit 3 recognizes an image of a small character area in a document.

In the above-described embodiment, the TPH 8 is configured to perform the main scanning of the image data line by line, but may be configured to perform the main scanning of the image data line by line.
The same past thermal history control for each heating element can also prevent the fine print from being broken.

[0041]

According to the present invention, in the fine print mode, the image of the original to be made is read, the contour of the image is detected, and the diameter of the perforation is smaller than the diameter of the perforation inside the image. Thus, the energy applied to the corresponding heating element is variably controlled. Since the perforation diameter of the outline portion of the image can be perforated to be small, the discharge amount of the ink passing through the perforation can be suppressed, and the fine print can be prevented, and a printed matter with good resolution can be obtained. This effect of preventing fine-character crushing is provided for both images containing fine characters and when the paper has good water absorbency, especially when printing images containing many fine characters on paper having good water absorbency. Is effective.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a stencil making machine for a stencil printing machine according to the present invention.

FIG. 2 is a diagram showing pulses applied to a thermal head.

FIG. 3 is a flowchart showing a mode switching operation by a control unit.

FIG. 4 is a flowchart showing control contents in a fine print mode.

FIG. 5 is a view showing an image obtained in a fine print mode.

FIG. 6 is a diagram showing a state of conventional heat history control.

FIG. 7 is a diagram showing a state in which a fine character is collapsed.

[Description of Signs] 1 ... operation unit, 2 ... control unit, 3 ... image processing unit, 4 ... history pattern detection unit, 5 ... first pulse generation circuit, 6 ... second
Pulse generating circuit, 7 ... selector, 8 ... thermal head.

Claims (7)

[Claims] 1. A stencil printing machine in which a thermal head having a plurality of heating elements is used to form perforations in a stencil sheet by the heat generated by the heating elements. And the pixels located in the outline of the image are detected, and the energy applied to each heating element is variably controlled so that the diameter of the holes in the outline becomes smaller than the diameter of the pixels in the interior. A stencil making machine for a stencil printing machine, comprising: 2. The stencil printing machine according to claim 1, further comprising means for detecting the internal pixels and the contour pixels based on the thermal history of each heating element of the thermal head. 3. A pulse voltage generating means for variably controlling the energy applied to the heating element, comprising a pulse voltage generating means for variably supplying a voltage application time to the heating element.
Or a stencil making machine for a stencil printing machine according to 2. 4. The stencil making machine for a stencil printing machine according to claim 1, wherein the variable control of the applied energy is executable when the temperature is equal to or higher than a predetermined temperature set in advance based on a temperature characteristic of ink used for printing. apparatus. 5. A thermal head having a plurality of heating elements and forming perforations in a stencil sheet by the heat generation of the heating elements, and an inner part of an image among pixels forming image data based on a heat history of each of the heating elements. And the pixels located at the outline of the image are detected, and the energy applied to each heating element is set such that the diameter of the perforations of the outline of the image is smaller than the diameter of the perforations of the pixels inside the image. History pattern detecting means for controlling switching, a second energy generating means for generating an applied energy for perforating a pixel inside the image with a predetermined perforation diameter as a reference, and a pixel at a contour portion of the image. First energy generating means for generating applied energy for perforating a hole with a smaller diameter than the reference hole diameter, based on switching control of the history pattern detecting means, Stencil printing machine plate making apparatus characterized by comprising a selector to switch to supply to the heating element of the corresponding thermal head either of the applied energy that is output from the second energy generating means. 6. The stencil printing machine according to claim 5, wherein the history pattern detecting means includes an operation section for setting whether or not to control the applied energy to the heating element. 7. A stencil printing machine making method using a thermal head having a plurality of heating elements and forming perforations in a stencil sheet by the heat generated by the heating elements, wherein the stencil sheet is positioned inside an image among pixels forming image data. And the pixels located at the outline of the image are detected, and the energy applied to each heating element is variably controlled so that the diameter of the perforations of the pixels of the outline is smaller than the diameter of the perforations of the internal pixels. A stencil making method for a stencil printing machine.