JP6014335B2 - Thermal head system - Google Patents

Description

  The present invention relates to, for example, a thermal head that heats each heating resistance element by applying a voltage to a heating resistor in which a plurality of heating resistance elements are arranged, such as a plate making mechanism of a master for heat-sensitive stencil in a stencil printing apparatus. The present invention relates to a system for controlling the amount of heat generated by a heating resistor element provided.

Conventionally, in a stencil printing apparatus, there are mainly a rotary stencil printing apparatus and a simple press stencil printing apparatus using a thermosensitive stencil master. In these printing apparatuses, a thermosensitive stencil printing (thermosensitive stencil) master in which a thermoplastic resin film perforated by heat melting and a porous thin paper or the like as a support of this film are bonded together with an adhesive is used. Then, the master is heated by a thermal head and punched in correspondence with the image line portion of the print image, and the master is made from the master support side by pressing the master and the printing paper together. Printed ink is transferred to the printing paper through the holes formed in the film.

  Generally, a thermal head has a heating resistor in which a plurality of heating resistance elements are arranged in a line shape, and a desired printed image is printed on the master by selectively driving the heating resistance elements. It is configured to

By the way, in the thermal head, since the resistance values of the respective heating resistance elements are not all constant, there is a problem that the heat generation amount is distributed in the head, resulting in uneven image density and missing dots (no perforation). . In order to solve this problem, conventionally, it has been proposed to correct each heating resistor according to the variation in resistance value and drive it.

  For example, in the technique disclosed in Patent Document 1, the measurement means for measuring the resistance values of a plurality of heating resistance elements provided in the thermal head, and the amount of heat generated by each heating element based on the measured resistance values. And adjusting means for adjusting the energization time of each heating element so as to be substantially uniform. Thereby, the heat generation amount of each heat generating element of the thermal head becomes constant, and high-precision printing can be performed.

  However, the technique disclosed in Patent Document 1 described above requires means for measuring the resistance value of each heating resistor element and adjusting the energization time of each heating resistor element each time the thermal head is driven. In addition to the time required for pre-processing such as resistance value measurement, a means for measurement is required, which complicates the structure and control of the system.

JP 2001-232840 A

By the way, in printing in a recent stencil printing apparatus, there is a demand for printing on a larger paper than the conventional A3 size. For example, when printing on a paper larger than A3 size, it is possible to fold the paper in a double-folded manner and publish more information with characters of an appropriate size.

  Here, when printing on a paper having a size larger than the A3 size, it is necessary to make the thermal head larger in consideration of the plate making speed. In the case of a conventional A3 size thermal head, the number of elements of the thermal head is about 7200 elements. Conventionally, it is considered that the technique described in Patent Document 1 described above can be applied to measure the resistance value and control the heat generation amount.

  However, when a thermal head that prints A2 size paper, for example, as a size larger than the A3 size, the number of heating resistance elements of the thermal head is about 14400 elements, which is twice that of a conventional A3 size thermal head. . When the amount of heat generation is individually controlled for each of the large number of heat generating resistance elements of the thermal head, as described above, it takes time for pre-processing such as resistance value measurement, and a means for measurement is required. There is a problem that the system structure and control become complicated.

  Here, a conventional problem will be described with reference to FIG. First, the trimming process will be described with reference to FIG.

In general, the trimming process changes the resistance value of the heating resistor element by performing pulse energization multiple times on the heating resistor element in order to minimize structural deterioration due to pulse conduction to the heating resistor element. In this processing method, the resistance values of the respective heating resistance elements are made uniform. Further, it is normal that the further fine variation after being uniformized is covered by the drive control of the thermal head.

FIG. 10A shows a distribution of resistance values of an A3 size thermal head and an A2 size thermal head as an example of a longer size than the A3 size. In the A3 size head, by performing the above-described trimming process, the resistance value variation in the thermal head can be reduced to a predetermined error range. However, since the A2 size thermal head shown in FIG. 10A is twice as long as the A3 size and is longer, as shown by the solid line, there is originally a large variation in resistance value.

In this case, since the resistance value varies greatly with respect to the A2 size thermal head, even if trimming is performed, the error range is as shown by the broken line of the A2 size thermal head in FIG. growing. Further, if it is intended to be within the same error range as the A3 size thermal head, it is necessary to make the trimming amount significantly larger than the trimming amount of the A3 size thermal head to make the resistance value of each heating resistor element uniform. . In this case, the degree of structural deterioration increases due to an increase in the trimming amount, and a heat generating resistive element that deteriorates in durability is generated, and there is a concern about the influence on the life of the thermal head. Note that this method of trimming the A2 size thermal head once has a manufacturing problem that requires a device dedicated to the A2 size thermal head, unlike the trimming process of the A3 size thermal head.

  Further, as shown in FIG. 10 (b), a long-sized head has a conventional A3 size as one unit, and the left side in the drawing direction is the head front side and the right side is the head rear side. It is also conceivable to perform control to divide from each position, perform trimming processing for each, acquire the respective average resistance values, and correct the heat generation time. Further, as described above, in order to trim the A2 size thermal head once, there is a manufacturing problem that requires a dedicated device. Therefore, there is a method of performing the trimming process for each A3 size thermal head. This is a simple and efficient trimming technique. As shown in FIG. 10B, when the average resistance value is taken with the A3 size as one group, the error of the average resistance value is reduced by a predetermined threshold (for example, the resistance value) in each A3 size group by trimming processing. The difference can be within 5%).

However, in this case, a problem occurs in the central portion of the A2 thermal head where the head front side and the head rear side are adjacent. As described above, each average resistance value can be stored at a predetermined threshold value in the unit of A3 size. However, in the central portion of the circled portion shown in FIG. 10B, which is the size of the A3 size, the value may deviate greatly from the respective average resistance value. There is a possibility that the difference is more than twice the range (resistance difference of ± 10% or more).

In this case, in the central portion of the thermal head, the right end portion in the drawing direction on the head front side has a resistance value larger than the average resistance value, and the diameter of the punched hole on the stencil sheet becomes small, and the left end portion in the drawing direction on the head rear side has The resistance value is small and the perforated diameter for the stencil sheet is large. As a result, a step in the heat generation resistance value locally occurs at the center of the thermal head, resulting in density unevenness in image quality. This is a phenomenon that occurs when the resistance value between the adjacent heating elements becomes more than a threshold value and deviates extremely in the central portion, and is a problem derived from the earnest study by the present inventors. .

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resistance value of a heating resistance element when the thermal head is driven in an apparatus including a thermal head having a plurality of heating resistance elements arranged in a line. Image quality is improved by controlling the difference in resistance value at the center of the thermal head without the need to perform measurements such as measurement of current and complicated energization control, and without reducing the durability due to an increase in the trimming amount. It is an object of the present invention to provide a thermal head system that can be used.

(1)
A thermal head system that drives a thermal head that generates heat from a heating resistor in which a plurality of heating resistance elements are arranged in a line,
The heating resistor is divided into M pieces (M is a natural number of 2 or more) in the extending direction of the line, and each unit group is constituted by a predetermined number of the heating resistor elements,
An average resistance value when each of the unit group and a plurality of heating resistor elements adjacent to the unit group is heated is stored.
A correction data storage unit that is calculated based on the average resistance value and stores correction data of each heat generation time of the unit group and a plurality of heating resistor elements adjacent to the unit group;
Based on the correction data stored in the correction data storage unit, a heating time control unit that controls the unit group and a plurality of heating resistor elements adjacent to the unit group, respectively.
A thermal head system comprising:

(2)
The unit group is further divided into N pieces (N is a natural number of 2 or more) in the extending direction of the line, and unit blocks each constituted by a predetermined number of the heating resistor elements,
An average resistance value when each of the unit groups and the unit blocks adjacent between the unit groups is heated is stored, calculated based on the average resistance value, and each of the unit group and the adjacent unit blocks A correction data storage unit for storing correction data of the heat generation time of
Based on the correction data stored in the correction data storage unit, a heating time control unit that controls the unit group and unit blocks adjacent to each other between the unit groups, and
The thermal head system according to claim 1, further comprising:

As an effect corresponding to the first feature in the present invention, the resistance value of a plurality of heating resistor elements adjacent to each other in each unit group without increasing the trimming amount more than specified, that is, without deteriorating the durability. Therefore, it is possible to suppress image density unevenness due to variations in the image quality. This is particularly effective when the resistance values within the unit group vary relatively.

Further, even when two A3 size thermal heads are connected to produce an A2 size thermal head, the same phenomenon occurs, so that the implementation method is also effective.

The effect corresponding to the second feature of the present invention is that the trimming amount is not increased more than specified, that is, the durability is not deteriorated, and the resistance value of adjacent unit blocks in each unit group varies. Image density unevenness can be suppressed. This is particularly effective when the resistance value in the block is relatively uniform.

FIG. 1 is an overall view showing a stencil printing apparatus. FIG. 2A is a plan view showing the thermal head unit according to this embodiment, and FIG. 2B is a side view showing the thermal head unit of FIG. FIG. 3A is a plan view schematically showing the thermal head, and FIG. 3B is a cross-sectional view taken along line XX in FIG. FIG. 4 is a block diagram illustrating a mechanism related to heat generation amount control according to the present embodiment. FIG. 5 is a diagram showing variation in resistance value of the thermal head according to the present embodiment. FIG. 6 is a diagram showing heat generation duty ratio control of each heat generation resistive element according to the present embodiment. FIG. 7 is a diagram showing heat pulse control of each heat generating resistive element according to the present embodiment. FIG. 8 is a process diagram showing a method for manufacturing a thermal head according to the present embodiment. FIG. 9 is a diagram showing perforation variation between the example according to the present embodiment and the comparative example. FIG. 10 is a diagram illustrating a problem of the related art.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, a case where the thermal head system and the thermal head heat generation control method of the present invention are applied to a plate making mechanism of a thermal stencil master in a stencil printing apparatus will be described as an example. In the present embodiment, the case where the present invention is applied to a master plate-making mechanism will be described, but the present invention is not limited to this, for example, a thermal recording apparatus, a thermal transfer recording apparatus, etc. The present invention can be applied to all devices in which a voltage is applied to a heating resistor in which heating resistors are arranged to cause each heating resistor to generate heat.

(Overall configuration of stencil printing machine)
FIG. 1 is a schematic cross-sectional view showing the internal configuration of the stencil printing apparatus 1 according to this embodiment. In FIG. 1, the stencil printing apparatus 1 controls a document reading mechanism 2, a plate making mechanism 3, a printing mechanism 4, a paper feeding mechanism 5, a paper discharging mechanism 6, a plate discharging mechanism 7, and each of these mechanisms. The control unit 8 is schematically configured.

  The printing mechanism 4 includes a plate cylinder 16 and a press roll 17, and the plate cylinder 16 and the press roll 17 are provided so as to be rotatable with parts of their outer peripheral surfaces being substantially close to each other. A base paper clamp portion 18 is provided on the outer peripheral surface of the plate cylinder 16, and the base paper clamp portion 18 grips the leading end of the stencil base paper. Further, a squeegee roll 47 of an outer press mechanism is provided on the inner peripheral surface of the plate cylinder 16 at a position facing the press roll 17. Further, an opening surface (effective marking surface) in which numerous holes are formed is formed on the outer peripheral surface of the plate cylinder 16, and ink is supplied from the inside of the plate cylinder 16 to the outside through this opening surface. The stencil paper is wound around the outer peripheral surface, and the ink is supplied to the outside only from the perforated surface of the stencil paper among the ink supplied between the opening of the outer peripheral surface and the stencil paper. .

  The paper feeding mechanism 5 includes a paper feeding base 23 on which a plurality of printing papers 22 as printing media are stacked, a scraper 24 that presses the printing paper 22 at the uppermost position from the paper feeding base 23, and a downstream of the scraper 24. The pickup roll 25 is disposed and is located in a state of being substantially close to each other, and the guide roll 27 and the timing roll 28 are disposed downstream of the pickup roll 25 and are located in a state of being substantially close to each other. The printing paper fed from the paper feed tray 23 is pulled out by the scraper 24 and sent out to the pickup roll 25. The paper discharge mechanism 6 includes a paper stripping claw 32 that strips the printed printing paper 22 from the plate cylinder 16, a paper transporting mechanism 33 that transports the stripped printing paper 22, and transported by the paper transporting mechanism 33. And a stacker unit 34 on which the printed printing paper 22 is placed in a stacked state.

  The evacuation mechanism 7 is configured to peel the stencil sheet 15 guided from the stencil sheet 15 guided from the stencil sheet belt 16 guided from the stencil sheet belt 16 by guiding the front end of the stencil sheet 15 released from the stencil sheet clamp portion 18 of the stencil sheet 16. The stencil sheet 36 collected by the stencil sheet 36, the anti-contamination guide 38 that prevents the stencil sheet 15 from coming into contact with the stencil sheet roller 36, and the stencil sheet 15 collected by the stencil sheet 36 are stored. And a discharge box 37.

  The document reading mechanism 2 is a mechanism such as a scanner that optically reads a document with a lens, a CCD, or the like and outputs it as an electrical signal. The read information is processed based on a predetermined command (enlargement, reduction, etc.) and sent to the plate making mechanism 3. In the present embodiment, the image data is read by the document reading mechanism 2, but the printer driver in the personal computer connected to the stencil printing apparatus 1 via a LAN (Local Area Network) or the stencil printing apparatus 1 is connected. A form in which image data is acquired from a USB (Universal Serial Bus) memory may be employed.

The plate making mechanism 3 performs plate making on the long base paper 10 based on the electrical signal read by the document reading mechanism 2, and is disposed downstream in the transport direction of the long base paper 10 wound on a roll. The thermal head unit 12, a platen roller 13 disposed opposite to the thermal head unit 12, and a base paper cutter 14 disposed downstream in the transport direction of the long base paper 10.

(Configuration of thermal head)
2A is a plan view showing the thermal head unit 12 to which the thermal head 70 is attached, and FIG. 2B is a side view showing the thermal head unit 12 of FIG. As shown in FIGS. 2A and 2B, the thermal head unit 12 includes a substrate 20. An aluminum heat sink 121 and a connector 122 are attached to the lower surface side of the substrate 20. An IC cover 123 is attached to the upper surface side of the substrate 20 by a nut 124. A thermal head 70 is formed on the substrate 20.

  FIG. 3A is a plan view schematically showing the thermal head 70, and FIG. 3B is an XX cross-sectional view of FIG. As shown in FIGS. 3A and 3B, the thermal head 70 has an insulating substrate body 56 made of alumina ceramic as a base, and the upper surface of the substrate body is covered with a glaze 57. Yes.

  A resistor 55 is provided above the glaze 57. A heating resistor 72 is provided above the resistor 55. The heating resistor 72 is configured by arranging a large number of heating resistance elements 721 to 72n made of thin films in a line shape in the main scanning direction at a predetermined interval. In the present embodiment, as shown in FIG. 3C, about 14400 heating resistance elements 721 to 72n are arranged. The heating resistance elements 721 to 72n are arranged at predetermined intervals in the length direction (main scanning direction) of the thermal head 70, and a voltage is selectively applied to individually control the heat generation. The conductive layers 64a and 64b are made of metal such as silver (Ag), gold (Au), copper (Cu), nickel (Ni), tungsten (W), aluminum (Al), platinum (Pt), or the main component thereof. Or a laminate of these metals and alloys.

  Further, on both sides of the heating resistor 72 in the sub-scanning direction, conductive layers 64a and 64b made of aluminum or the like are on the glaze 57 and the resistor 55 so as to be electrically connected to the heating resistor elements 721 to 72n, respectively. It is formed into a film. Further, in the thermal head 70, a protective layer 58 is formed so as to cover the heating resistor 72 and the conductive layers 64a and 64b in a lump. Further, common electrode portions 66 and 66 are disposed at both ends of the heating resistor 72.

(Heat generation time control mechanism)
FIG. 4 is a block diagram illustrating a mechanism related to drive control. The “module” used in the description refers to a functional unit that is configured by hardware such as an apparatus or device, software having the function, or a combination thereof, and achieves a predetermined operation. .

  As shown in FIG. 4, the control unit 8 is a module relating to drive control of the heating resistor elements 721 to 72n, and includes a label correction value storage unit 9, a correction data storage unit 84, a power supply control circuit 86, and a heating time control unit. 81 and the drive circuit 30 are provided. The control unit 8 receives a signal from an external device connected to an external interface (not shown) and an operation signal based on a user operation from the operation panel 80.

  The control unit 8 is configured to be able to individually control the heating resistance elements 721 to 72n of the heating resistor 72 for each unit. Each unit is composed of one section among the plurality of heating resistance elements 721 to 72n divided in the line arrangement direction, and has a predetermined number of heating resistance elements. In the present embodiment, the thermal head 70 is configured to have an average resistance value as two groups in units of the head front side and the head rear side. Further, the thermal head 70 is configured as four blocks on the head front side and the head rear side, and has an average resistance value.

  The heat generation time control unit 81 is realized by, for example, an arithmetic processing device that executes various arithmetic processes such as a CPU. Here, when the thermal head 70 is driven during the plate-making operation, the correction data is stored in the correction data storage unit 84. The heating resistor elements 721 to 72n function as modules that generate heat during the heat generation time corresponding to the read correction data. In the present embodiment, the heat generation time control unit 81 adjusts the heat generation time of the thermal head by controlling the heat generation time and the heat generation duty ratio for the heat generation resistance elements 721 to 72n, and the heat generation time of each of the heat generation resistance elements 721 to 72n. To change. As the adjustment of the heat generation time, the heat generation energy may be changed by controlling the voltage in addition to the control of the heat generation time. Here, the heat generation time is a time required for the heat generating resistive element of the thermal head to perforate, and includes a time during which the heat generating resistive element is off. Further, the heat generation duty ratio is a ratio indicating the ratio of the off time in one cycle of the heat generation time.

  The heat generation time control unit 81 is connected to a correction data storage unit 84, and correction data is stored in the correction data storage unit 84. Here, the correction data is stored in units of groups on the head front side and the head rear side of the thermal head based on the respective average resistance values. Further, the correction data is stored for each unit block obtained by dividing the A2 size thermal head into four parts each on the front side and the rear side. In addition, the correction data for each group on the head front side or the head rear side of the thermal head and the correction data for each unit block are supplied from the label correction value storage unit 9 via the operation panel 80 for each unit group or block. Created based on the label value. The label correction value storage unit 9 stores an average resistance value of the heating resistance elements 721 to 72n belonging to each unit group and each block as a label value. The label value of each unit group (the average resistance value of the heating resistor elements 721 to 72n belonging to each unit group) and the label value of each unit block (the average resistance value of the heating resistor elements 721 to 72n belonging to each unit block) are It is created based on the resistance values of the respective heating resistance elements 721 to 72n measured by an external resistance value measuring device (not shown) at the time of manufacturing the head 70.

  The power supply control circuit 86 is configured to control the power supply mechanism (1) 88 and the power supply mechanism (2) 89 connected to the thermal head 70 in the plate making mechanism 3 of the present embodiment. In this embodiment, since the thermal head 70 is an A2 type long head, it is controlled by using two power supplies on the head front side and the head rear side as the A3 size. In the present embodiment, based on the correction data from the correction data storage unit 84, the head front side and the head rear side are controlled using the respective power supplies, thereby making the A3 size group unit equivalent to the conventional size. It is configured to be controllable.

(Creation of correction data)
Next, the creation of correction data at the time of manufacturing the above-described thermal head will be described with reference to FIG. First, it is assumed that the heating resistance elements 721 to 72n according to the present embodiment are groups on the head front side and the head rear side as shown in FIG.

In this embodiment, as an example, the thermal head is adapted to print a long size A2 size paper, and the number of elements of the thermal head is about 14400 elements. Controlling the amount of heat generated individually for this large number of elements requires time for preprocessing such as resistance measurement and requires measurement means, and the structure and control of the system. There is a problem that becomes complicated.

Further, when the resistance values of all the heating resistance elements 721 to 72n are made to coincide with a certain average resistance value by increasing or decreasing the trimming amount, the heating resistance elements 721 to 72n having a larger trimming amount have a smaller trimming amount. As compared with ˜72n, there arises a problem that the degree of structural deterioration is increased and the life is shortened.

  As shown in FIG. 5, when the trimming process is performed on the head front side and the head rear side, that is, the internal resistance value varies with respect to the average resistance value in the group of blocks 1 to 4 and the group of blocks 5 to 8. Is within 5% of the error range, the resistance value between the block 4 and the block 5 may be up to 10% error by accumulating each error by 5% in some cases. There is a possibility. In this case, if an adjacent pixel or block has an error of 10%, an image defect due to image density unevenness or perforation failure occurs.

  Therefore, in order to solve the above problem, the correction method based on the correction data based on the label value in the present embodiment is as follows. First, on the head front side and the head rear side of the thermal head 70, an average resistance value is calculated for each group. In this embodiment, a reference heat generation energy is set in order to create correction data. Further, for the average resistance value of the blocks 4 and 5 which are the central part in the longitudinal direction of the thermal head, a value in which the resistance value measured in the manufacturing process of the thermal head is labeled is input. Here, it is determined whether or not the error range of the average resistance value in the blocks 4 and 5 is less than ± 2.5%. If the error range of the average resistance value is ± 2.5% or more, control for adjusting the heat generation time is performed to adjust the heat generation time for the thermal head. In the present embodiment, a value for adjusting the heat generation time is converted in advance with a predetermined resistance value width and stored as a label value. Further, the average resistance value and the average resistance values of the blocks 4 and 5 are stored as label values on the head front side and the head rear side. Based on the stored correction data, drive control of the thermal head 70 is performed. When the error range of the average resistance value is less than ± 2.5%, the reference control is performed.

Here, an example will be described in which data for correcting the heat generation time of the thermal head is created using specific data in addition to the method described above in the present embodiment. The average resistance value on the head front side is 3800Ω, and the average resistance value on the head rear side is 4300Ω. In this embodiment, the average resistance value of the block 4 is 3900Ω, and the average resistance value of the block 5 is 4100Ω. In this embodiment, when the perforation is performed with the standard plate-making power of 0.0687 W / dot and the standard plate-making time: 380 μs, the head front block 4 is generally small and the head rear block 5 is generally As a result, the difference in perforation at the center of the thermal head becomes remarkable, and density unevenness occurs. In this embodiment, as shown in FIG. 6, the block 4 applies a resistance value of about + 5% and a time of 400 μs (time 5), and the block 5 has a resistance value of about −5% and a time of 360 μs. Apply (time 1). That is, the heat generation time is adjusted so that the difference between the average resistance value of the blocks 4 and 5 and the overall average resistance value is less than ± 2.5%. In this embodiment, as shown in FIG. 6, the correction data storage unit 84 stores the heat generation duty ratio of times 1 to 5 depending on the variation of the average resistance value. In the present embodiment, the chopping control is performed based on the heat generation duty ratio. However, as shown in FIG. 7, control based on the heat generation pulse width may be performed.

  In the present embodiment, the control is performed according to the average value of the boundary portion of the central portion for each block. However, paying attention to the heating resistance element of the thermal head in this block, a plurality of adjacent central portions are arranged. You may comprise so that it may correct | amend based on the average resistance value of a heating resistive element. In this case, control with correction data can be performed on the minimum necessary heating resistance element in the central portion. In this embodiment, the A2 size thermal head 70 is configured to have an average resistance value on the head front side and the head rear side, but is further divided into blocks at the center of the thermal head. May be.

  Next, referring to the process diagram of FIG. 8, from the manufacture of the thermal head 70 including the heat generation control of the heating resistance elements 721 to 72n for each unit group and for each unit block using the correction data determined in the above-described procedure. The procedure up to driving will be described.

  As shown in the figure, first, in the glaze substrate manufacturing process in step S101, a glaze 57 is formed on the substrate body 56 by screen printing or the like. At this time, the heating resistor element 57a is formed in a line shape on the upper surface of the glaze 57.

Next, the resistor 55 and the heating resistor 72 are formed on the glaze 57 in the heating resistor element film forming process of step S102. The heating resistor 72 is formed by using a thin film forming technique such as vacuum deposition or sputtering, for example.

  Then. In the annealing process (heating process) in step S103, the entire heating resistor is heated. By this annealing treatment, the local crystal distortion generated in the heating resistor 72 during the manufacturing process is eliminated, and the crystal structure of the heating element in the entire heating resistor 72 is enhanced, so that the film structure of the heating resistor elements 721 to 72n is increased. Is stabilized.

  Next, in the electrode layer film forming process in step S104, a conductive layer 64 having a desired thickness is formed on the entire surface of the heating resistor 72. The conductive layer 64 may be formed by a thin film forming technique such as sputtering, or may be formed by a screen printing method.

Next, in a photolithography and etching process in step S105, patterning is performed by photolithography and etching to remove the conductive layer 64 in a desired region. More specifically, the conductive layer 64 is removed so that the thermal heads 70 are formed in the longitudinal direction of the thermal head 70 and arranged at predetermined intervals, and the heating resistors 72 are exposed. Through this step, the conductive layer 64 is electrically separated into the first conductive layer 64a on the common electrode portion 66 side and the second conductive layer 64b on the opposite side. Next, in the protective film forming step of step S106, the protective layer 58 is formed as the uppermost layer.

Next, in the trimming process in step S108, trimming is performed in order to adjust the resistance value of each manufactured heating resistor 72. In this trimming process, the resistance values of the heating resistor elements 721 to 72n are changed by performing pulse energization a plurality of times between the conductive layers 64a and 64b for the heating resistor elements 721 to 72n constituting each pixel. The resistance value of the heating resistor 72 at the dot is adjusted to a desired resistance value. In this embodiment, in this step S108, the degree of variation in the resistance value may be reduced within a desired range on the head front side and the head rear side of the thermal head.

  Next, in step 109, the resistance value of the heating resistor 72 is measured, and in step 110, the average resistance value for each unit group and for each unit block in the front and rear heads is calculated. In the present embodiment, there are about 14400 heating resistance elements 721 to 72n, which can be divided into two and set as the head front side and the head rear side. Further, each of these thermal heads is divided into four equal parts to form unit blocks. In the unit block, the equal number of the heating resistance elements 721 to 72n is not limited to four and is arbitrary. In particular, for unit blocks, it is preferable to calculate an average resistance value of unit blocks adjacent to each other between groups.

  Next, in the correction data creation step of step 111, based on the calculated resistance value, correction data for energization control at the time of recording is created for each unit group and for each unit block by the procedure described above.

  Thereafter, the created correction data is stored in the correction data storage unit 84 through the label correction value storage unit 9 of the control unit 8.

(Prepress operation)
Next, the plate making operation in the stencil printing apparatus 1 having the above configuration will be described.

  First, in the plate making mechanism 3, the long base paper 10 is conveyed by the rotation of the platen roller 13 and the base paper feed roller, and sent out to the thermal head unit 12. In the thermal head unit 12, the heat generating resistive elements 721 to 72 n of the thermal head 70 selectively generate heat based on the image information read by the document reading mechanism 2, thereby performing heat-sensitive perforation on the long base paper 10 and stencil. The base paper 15 is made.

  At this time, when the thermal head 70 is driven, the correction data is read from the correction data storage unit 84 based on the resistance value measured by the label correction value storage unit 9, and the correction data read by the heat generation time control unit 81 is read out. The heat generation time is adjusted so as to become the heat generation time according to the above, the drive circuit 30 is controlled, and the heat generating resistance elements 721 to 72n are heated.

  The heat generation time control unit 81 analyzes the image data read by the document reading mechanism 2 and punches in correspondence with the image line portion of the print image so that the heat generation energy corresponding to the dots of each pixel is obtained. The heat generation time for each pixel is calculated. At this time, referring to the correction data, the heat generation time is expanded or contracted according to the resistance value of each of the heat generation resistance elements 721 to 72n. More specifically, the unit block and the unit are set so that the label correction value storage unit 9 eliminates image unevenness in the state of the central portion of the thermal head based on the resistance value measured in the manufacturing process. The heat generation time of each heating resistance element 721 to 72n is corrected in a group.

  Then, the heat generation time control unit 81 transmits a signal to the drive circuit 30, heats the thermal head 70 according to the corrected heat generation time, performs punching corresponding to the image line portion of the print image, and performs plate making. At the time of printing driving, the front end of the stencil sheet 15 is clamped by the stencil clamping unit 18 of the plate cylinder 16, and the stencil sheet 15 is rotated by rotating the plate cylinder 16 in this clamped state. Wrap around the outer peripheral surface. Then, the printing paper 22 is pressed between the squeegee roll 47 and the press roll 17 together with the plate cylinder 16 and the stencil paper 15, and ink is transferred from the perforated portion of the stencil paper 15 to the printing paper 22 to print an image.

  Here, with reference to FIG. 9, in this embodiment, the comparison of the image of the center part of the thermal head 70 is demonstrated separately in the case where the control of this embodiment is performed and the case where it is not performed. In FIG. 9, the center line which shows a center part is shown with a broken line. 9A in which the control of the present embodiment is performed, the perforation variation in the central portion of the thermal head 70 is relatively reduced as compared with FIG. 9B in which the control of the present invention is not performed. I understand that. Further, enlarged views are shown in FIGS. 9 (c) and 9 (d). In this embodiment, it can be seen that the variation is significantly reduced.

As described above, according to this embodiment, it is possible to suppress image density unevenness due to variations in resistance value without increasing the trimming amount beyond a predetermined level, that is, without deteriorating durability. Further, in the present embodiment, the hardware configuration is not complicated, and the blurring in the image and the durability described above can be suppressed.

DESCRIPTION OF SYMBOLS 1 Stencil printing apparatus 2 Document reading mechanism 3 Plate making mechanism 4 Printing mechanism 5 Paper feed mechanism 6 Paper discharge mechanism 7 Paper discharge mechanism 8 Control part 9 Label correction value memory | storage part 10 Long length base paper 12 Thermal head unit 13 Platen roller 14 Base paper cutter 16 Plate cylinder 17 Press roll 18 Base paper clamp section 20 Substrate 22 Printing paper 23 Paper feed tray 24 Scraper 25 Pickup roll 27 Guide roll 28 Timing roll 30 Drive circuit 32 Paper stripping claw 33 Paper transport mechanism 34 Stacker section 35 Discharge guide belt 36 Discharge plate Roller 37 Discharge box 38 Contamination prevention guide 47 Squeegee roll 55 Resistor 56 Substrate body 57 Glaze 58 Protective layer 64a, 64b Conductive layer 66 Common electrode portion 70 Thermal head 72 Heating resistor 721-72n Heating resistor element 80 Operation panel 81 Heating time Control unit 83 Part interface 84 correction data storage unit 86 the power control circuit 88 power supply (1)
89 Power supply mechanism (2)
121 Aluminum heat sink 123 IC cover 124 Nut 122 Connector

Claims (3)

A thermal head system that drives a thermal head that generates heat from a heating resistor in which a plurality of heating resistance elements are arranged in a line,
The heating resistor is divided into M pieces (M is a natural number of 2 or more) in the extending direction of the line, and each unit group is constituted by a predetermined number of the heating resistor elements,
Average resistance value storage means for storing an average resistance value when each of the unit group and a plurality of heating resistance elements adjacent to the unit group are heated, respectively ;
On the basis of the average resistance value, and the correction data calculation means for calculating correction data for each of the heating energy of a plurality of heating elements adjacent the unit group and the group of units,
A correction data storage unit for storing the correction data;
Based on the correction data stored in the correction data storage unit, a heating energy control unit that controls each of the unit group and a plurality of heating resistor elements adjacent to the unit group, and
A thermal head system comprising: The unit group is further divided into N pieces (N is a natural number of 2 or more) in the extending direction of the line, and unit blocks each constituted by a predetermined number of the heating resistor elements,
Average resistance value storage means for storing average resistance values when the unit groups and unit blocks adjacent to each other between the unit groups are heated, respectively ;
On the basis of the average resistance value, and the correction data calculation means for calculating correction data for each of the heating energy of the group of units and the adjacent unit blocks,
A correction data storage unit for storing the correction data;
Based on the correction data stored in the correction data storage unit, a heating energy control unit that controls the unit group and unit blocks adjacent to each other between the unit groups,
The thermal head system according to claim 1, further comprising: The thermal head system according to claim 1, wherein the thermal head includes a power supply mechanism for each group.