Thermal print head, thermal printer and printer system

A thermal print head includes a heating resistor for forming images on a print target by generating heat, and a driver for controlling power supply to the heating resistor. The thermal print head also includes a storage unit and a controller. The storage unit stores print data inputted from outside. The controller causes a transfer action and a printing action to be repeated alternately, wherein the transfer action includes retrieving print data from the storage unit and transferring the retrieved print data to the driver, and the printing action includes causing the driver to retain the transferred print data and supplying power to portions of the heating resistor selected in accordance with the print data retained by the driver, so as to conduct printing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thermal print head, a thermal printer including the thermal print head, and a printer system including a plurality of thermal printers.

2. Related Art

There has been known a thermal print head or a thermal printer incorporating a thermal print head (see JP-A-No. 2005-186302, for example) that causes the heating resistor to selectively heat recording paper (such as thermosensitive paper) or thermal transfer ink ribbon, so that letters or images are to be printed.

FIG. 16is a block diagram of an example of the thermal printer including the conventional thermal print head. The thermal printer990shown therein includes the thermal print head999. The thermal print head999includes a substrate991, a heating resistor992, a driver IC993, and a connector994. On the substrate991, an elongated heating resistor992is provided. The thermal print head999is connected to a control unit995of the thermal printer990, via the connector994.

To the thermal print head999, a printing data signal, control signal, and power necessary for executing a printing action are transmitted from the control unit995through the connector994. The printing data signal and the control signal are transferred to the driver IC993through a wiring pattern996formed on the substrate991.

The control signal includes a clock signal, a latch signal and a strobe signal. The clock signal serves to establish synchronization when data to be printed is outputted to the driver IC993. The latch signal serves to output in parallel the printing data signal serially inputted, by an amount corresponding to one line of the image. The strobe signal serves for supplying power to the heating resistor992. Here, a printing mechanism such as a platen roller for activating the printing action is not shown in the thermal printer990shown inFIG. 16.

The thermal print head999is capable of producing a smooth printing action in the case of printing letters and characters containing relatively small data amount. On the other hand, in the case where the data to be printed is, for example, image data that contains gradations of light and intense of black color, the thermal print head999executes the following process.

To print the data corresponding to one line for example, the data is outputted to the driver IC993the times corresponding to the number of gradations of the image. When the number of gradations is 256 for example, the data for 255 times of printing per line (except for the gradation “0 (=white)”) is transferred from the control unit995to the thermal print head999. To be more detailed, the image data containing the data representing the dots of the gradation “1” and higher is inputted to a shift register (not shown) in the driver IC993, at a first transfer. Then the image data inputted to the shift register is retained by the latch signal. Then power is supplied according to the strobe signal to the portion of the heating resistor992to be heated, determined based on the image data, so that such portion is heated. Thus, the data corresponding to the dots of the gradation “1” and higher is printed on the recording paper.

Then the image data corresponding to the dots of the gradation “2” and higher is transferred, and the similar process is executed. In this case, the dots of the gradation “2” and higher are printed over the dots of the gradation “1”, which have been printed in the first printing process. Such data transfer is executed up to the image data corresponding to the dots of the gradation “255 (=black)”. The transfer action of the image data and the printing action on the recording paper are repeated 255 times respectively. With respect to the dots of the gradation “0 (=white)”, such printing process is not executed. The region on the recording paper corresponding to the dots that have remained unprinted during the printing process from the gradation “1” to the gradation “255” resultantly represents the white portion corresponding to the gradation “0”.

Thus, the thermal printer990including the thermal print head999has to repeat the transfer action of the image data and the printing action, for printing the image data containing the gradations. This leads to the drawback that the printing takes a long time.

It might be possible to increase the transfer rate of the image data between the control unit995of the thermal printer990and the thermal print head999, in order to print the image data at a higher speed. However, an excessively high transfer rate may provoke deformation of the waveform of the signals on respective signal lines between the control unit995of the thermal printer990and the thermal print head999, resulting in data deficiency. Besides, radiation may take place in the respective signal lines, which may disturb normal transfer of the signals between each other. Accordingly, a limitation is inevitably imposed on the transfer rate of the image data between the control unit995of the thermal printer990and the thermal print head999, and hence it is difficult to transfer the image data at a higher speed. Especially in the case of printing the image data containing an enormous data amount, the printing speed of the thermal print head999is subjected to such limitation. Also, the deformation of the waveform and the radiation appear more prominently, as the line length between the control unit995of the thermal printer990and the thermal print head999becomes longer. Therefore, the line length is also limited.

Meanwhile, recently an automatic identification system has come to be widely employed, for example for luggage management at an airport. The automatic identification system automatically takes up the data of the objects to be managed, by means including both hardware and software without depending on human power, and recognizes the data of the object. Specific examples of the automatic identification system include the one that utilizes a Radio Frequency IDentification (RFID) tag. The RFID tag includes a memory for recording the identification data, and a medium-side coil antenna for data transmission/reception by wireless communication, and letters or a barcode representing the identification data is printed on the outer surface of the RFID tag. To execute the data transmission/reception to and from the RFID tag, and the printing thereon, for example an RFID tag printer is employed (for example, JP-A No. 2003-132330).

However, the RFID tag printer has to be equipped with the antenna for data transmission/reception and a driver IC therefor, in addition to the thermal print head engaged in the printing function. Especially in the case where the antenna is located distant from the RFID tag, the print target, the reliability of the data transmission/reception may be degraded.

SUMMARY OF THE INVENTION

The present invention has been proposed under the foregoing situation, with an object to provide a thermal print head capable of printing image data at a high speed even when, for example, the image data contains gradations, a thermal printer including such thermal print head, and a printer system.

Another object of the present invention is to provide a thermal print head and a thermal printer with a wireless communication function, that can be made smaller in dimensions and that can improve reliability and speed of data transmission/reception.

A first aspect of the present invention provides a thermal print head comprising: a heating resistor that generates heat for forming an image on a print target; a driver that controls power supply to the heating resistor; a storage unit that stores print data inputted from outside; and a main controller that causes a transfer action and a printing action to be alternately repeated, where the transfer action includes retrieving print data from the storage unit and transferring the retrieved print data to the driver, and the printing action includes causing the driver to retain the transferred print data and supplying power to portions of the heating resistor selected in accordance with the print data retained by the driver, so as to conduct printing.

In a preferred embodiment of the present invention, the thermal print head comprises: a substrate on which the heating resistor is formed; and an intermediate conductor mounted on the substrate, where the controller comprises a control chip removably supported by the intermediate conductor.

In a preferred embodiment of the present invention, the substrate is provided with a wiring pattern including a signal line for the print data disposed between the control chip and the driver. The wiring pattern further includes a signal line for a control signal to supply power to the heating resistor.

In a preferred embodiment of the present invention, the substrate is connected with a signal line for transferring a signal to be inputted to the control chip, where the signal line is an I2C signal line for executing serial transfer of the signal.

In a preferred embodiment of the present invention, the thermal print head further comprises an additional intermediate conductor mounted on the substrate, where the storage unit comprises a memory chip removably supported by the additional intermediate conductor.

In a preferred embodiment of the present invention, the thermal print head further comprises a data transmitter/receiver that executes data transmission/reception by wireless communication with respect to the print target, where the print target is provided with a target-side coil antenna and a memory.

In a preferred embodiment of the present invention, the data transmitter/receiver includes an apparatus-side coil antenna.

In a preferred embodiment of the present invention, the data transmitter/receiver further includes a driver IC for the apparatus-side coil antenna.

In a preferred embodiment of the present invention, the data transmitter/receiver is capable of executing data transmission/reception to and from the print target, which is constituted as a Radio Frequency IDentification (RFID) tag.

In a preferred embodiment of the present invention, the thermal print head further comprises a substrate, and a plurality of heating resistors aligned on the substrate, where the apparatus-side coil antenna is mounted on the substrate.

In a preferred embodiment of the present invention, the apparatus-side coil antenna is located on a face of the substrate on which the plurality of heating resistors are provided.

In a preferred embodiment of the present invention, the thermal print head further comprises a magnetic sheet containing a magnetic material.

In a preferred embodiment of the present invention, the magnetic material is ferrite.

In a preferred embodiment of the present invention, the magnetic sheet is located on a face of the substrate opposite to a face on which the apparatus-side coil antenna is provided.

In a preferred embodiment of the present invention, the thermal print head further comprises a cover that covers the driver IC, where the cover is formed with an opening through which the apparatus-side coil antenna is exposed as viewed in a thicknesswise direction of the substrate.

In a preferred embodiment of the present invention, in a main scanning direction, the opening is smaller in size than the print target.

A second aspect of the present invention provides a thermal printer with a wireless communication function. This thermal printer comprises the thermal print head according to the first aspect of the present invention, so that both printing on the print target and data transmission/reception to and from the print target can be executed.

A third aspect of the present invention provides a thermal printer comprising: the thermal print head according to the first aspect of the present invention; an action controller that transmits the print data to the thermal print head and causes the thermal print head to execute printing; and a signal line for serially transferring the print data from the action controller to the main controller.

The fourth aspect of the present invention provides a printer system comprising: a plurality of thermal printers each including the thermal print head according to the first aspect of the present invention; a control unit that transmits the print data to a designated thermal printer among the plurality of thermal printers and causes the designated thermal printer to execute printing; and a signal line that connects the control unit and the plurality of thermal printers in a bus configuration, for serial transfer of the print data.

Other features and advantages of the present invention will become more apparent through the detailed description given hereunder referring to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1depicts a thermal print head according to a first embodiment of the present invention, andFIG. 2is a block diagram of a thermal printer including the thermal print head. The thermal print head11and the thermal printer16are configured to print letters and images on recording paper such as thermosensitive paper or other kinds of recording medium (“print target”). The thermal print head11according to this embodiment includes a substrate20, a heat dissipater23, a heating resistor30, a driver IC41, a control chip42, a quartz oscillator43, a memory chip44and a connector64.

The substrate20serves as the case of the thermal print head11, and is constituted of a heating function unit21and a circuit board22in this embodiment. Unlike this embodiment, the substrate20may be constituted of a single material.

The heating function unit21is made of an insulating material such as a ceramic, and formed in a rectangular shape, for example. On a front face211of the heating function unit21, the heating resistor30and the driver IC41are mounted. In a region close to an edge of a side of the front face211, a partial glaze214is provided. The partial glaze214extends in a main scanning direction, and protrudes in a direction of the normal of the front face211.

The circuit board22is a printed circuit board constituted of, for example, a glass epoxy resin. On a front face221of the circuit board22, the control chip42, the quartz oscillator43, and the memory chip44are mounted.

On the front face211of the heating function unit21and the front face221of the circuit board22, wiring60is provided. The wiring60includes a plurality of individual electrodes61, a common electrode62, a common line63, and a signal line67. As shown inFIG. 4, the common electrode62is constituted of an elongated strip-shaped portion extending in the main scanning direction and a plurality of branch portions extending in a comb teeth shape in a sub scanning direction. The individual electrodes61have the respective tip portion alternately aligned with respect to the branch portions, in the main scanning direction. As shown inFIG. 1the common line63is connected to the common electrode62, and extends to the connector64. The individual electrodes61, the common electrode62, and the common line63may be formed, for example, by thick film printing of a resinate Au paste, followed by sintering.

The heat dissipater23is a thick rectangular plate, for example made of aluminum. As shown inFIG. 1, the heat dissipater23is stuck to a back face212of the heating function unit21and a back face222of the circuit board22.

The heating resistor30is made of a resistance material such as ruthenium oxide, and provided in a strip-shape on the partial glaze214. As shown inFIG. 4, the heating resistor30is located so as to run over the branch portions of the common electrode62and the tip portion of the individual electrodes61. When a current runs between the common electrode62and one of the individual electrodes61, the heating resistor30is partially heated in a region defined by the branch portions and the tip portion. Such region will be referred to as a heating portion31. The heating resistor30constitutes a plurality of heating portions31aligned in the main scanning direction. The heating resistor30may be formed, for example, by thick film printing of a ruthenium oxide paste, followed by sintering. Also, the heating resistor30is covered with a cover layer (not shown), for example made of glass.

The driver IC41serves to selectively supply power to the heating resistor30through the individual electrodes61. To the driver IC41, printing data signals and control signals necessary for a printing action is inputted from the control chip42. The control signal includes a clock signal, a latch signal, and a strobe signal.

The control chip42is constituted of a CPU, and capable of converting image data inputted via the connector64into gradation pattern data, and storing the converted gradation pattern data in the memory chip44. Here, the image data consists, for example, of a group of numerals representing the gradation of each dot. On the other hand, the gradation pattern data consists of numeric columns each having equivalent values to the number of dots per line, and the number of such columns is equivalent to the number of printing times corresponding to a maximal number of gradations. In the respective numeric column, the numeral corresponding to a dot to be printed is 1, and the numeral corresponding to a dot not to be printed is 0, for each printing action. In this embodiment, the control chip42is located adjacent to the memory chip44. Such configuration allows shortening the path for the data transfer.

In this embodiment, the gradation pattern data is subjected to what is known as thermal history control. The thermal history control serves to control the energy to be supplied to a minute portion of the heating resistor30, taking into account the immediately precedent thermal history and influence of an adjacent minute portion of the heating resistor30that has been heated. The process of the thermal history control is executed by the control chip42.

The control chip42also retrieves the gradation pattern data from the memory chip44based on a printing command from an action control unit161(to be described later) of the thermal printer16, and outputs the gradation pattern data and the control signal to the driver IC41.

The control chip42is implemented on the circuit board22via an IC socket421. The IC socket421is directly mounted on the circuit board22, so as to removably support the control chip42. As shown inFIG. 3, the IC socket421includes a plurality of signal terminals424and a plurality of terminal insertion holes423. The number of the signal terminals424is the same as that of the signal terminals422of the control chip42. The terminal insertion holes423are each electrically connected to the respective signal terminal424.

The quartz oscillator43generates a clock signal of 30 to 40 MHz for example, and provides a reference clock signal to the control chip42. The clock signal serves to establish synchronization when data to be printed (“print data”) is outputted to the driver IC41.

Between the driver IC41and the control chip42, the signal line67is provided. The signal line67constitutes a data signal line, a clock signal line, a latch signal line and a strobe signal line. In other words, the signal line67constitutes a signal line similar to the respective signal line996provided between the connector994and the driver IC993of the conventional thermal print head999(FIG. 16), between the control chip42and the driver IC41.

The memory chip44stores the gradation pattern data converted by the control chip42from the image data. The storage and retrieval of the gradation pattern data in and from the memory chip44is controlled by the control chip42. The memory chip44is, as the control chip42, implemented on the circuit board22via the IC socket441.

The connector64serves for electrical connection between the thermal print head11and the thermal printer16. In this embodiment, a power supply line162and a signal line163are connected to the connector64. The power supply line162serves to supply power to the thermal print head11. The signal line163is a signal line formed in accordance with the Inter-Integrated Circuit (I2C) (hereinafter, “I2C signal line163”), which enables serial communication of data.

The I2C signal line163includes the data signal line through which the data signal is transferred, and the clock signal line through which the clock signal synchronized with the data signal (different from the clock signal generated by the quartz oscillator43). The I2C signal line163is capable of serially transfer the data based on a predetermined data format, at a transfer rate of, for instance, 3.4 Mbps. In this embodiment, the image data is transferred through the I2C signal line163, from the action control unit161of the thermal printer16to the thermal print head11. Since the I2C signal line163is capable of transferring the data based on a predetermined data format, the data based on a command can also be transferred. For example, a command for start the printing is transferred from the action control unit161of the thermal printer16to the control chip42.

The thermal printer16includes the thermal print head11, and also the action control unit161, a motor control unit164, and a printing mechanism165. The action control unit161serves to control various actions according to inputs by a user through an operating unit (not shown). The action control unit161can, for example, transfer the image data inputted from outside of the thermal printer16, to the thermal print head11, and control the motor control unit164for executing the printing action. The action control unit161can also detect running out of the thermosensitive paper and announce abnormality of the apparatus.

The printing mechanism165of the thermal printer16includes, though not shown, a platen roller that presses the thermosensitive paper against the thermal print head11, a feed roller and a takeup roller of the thermosensitive paper, and a plurality of driving motors that drives these rollers. The driving motors are driven under the control of the action control unit161. In the case where the thermal printer16executes the thermal transfer printing on the ink ribbon, the printing mechanism165also includes a feed roller and a takeup roller of the ink ribbon, and a driving motor that drives these rollers.

Operation of the thermal print head11will now be described, referring to the flowchart shown inFIG. 5and the timing chart shown inFIGS. 6 and 7. The flowchart ofFIG. 5primarily represents the controlling action of the control chip42, but also includes some actions of the thermal printer16.

When the thermal printer16is powered on, power is supplied to the thermal print head11. Then when a printing action is started by, for example, manipulation through an operating unit which is not shown (S1), the image data is transferred from the action control unit161of the thermal printer16to the control chip42(S2). The image data contains the data of all the lines to be printed on the recording paper. In this embodiment, as stated above, the action control unit161of the thermal printer16and the thermal print head11are connected via the I2C signal line163based on the I2C specification. Accordingly, the image data is transferred at a high printing speed (for example, 3.4 Mbps) in synchronization with the predetermined clock signal, as shown inFIG. 6.

The control chip42executes the thermal history control upon receipt of the image data transferred from the thermal printer16, and generates the gradation pattern data corresponding to, for example, 256 gradations (S3). The control chip42then sequentially stores the generated gradation pattern data in the memory chip44(S4). Thus, the data stored in the memory chip44is made up as the gradation pattern data subjected to the thermal history control.

Then a printing command for printing one line is transferred from the thermal printer16to the control chip42(S5), and the printing process for that one line is executed (S6). In this case, the control chip42retrieves the gradation pattern data from the memory chip44, and outputs the gradation pattern data to the driver IC41through the data signal line included in the signal line67. To be more detailed, the data for the same number of printing actions as the number of gradations of the image is outputted to the driver IC41. For example, in the case where the number of gradations is 256, the data for printing 255 times per line (except for the gradation “0 (=white)”) is transferred from the control chip42to the driver IC41.

First, the gradation pattern data containing the data representing the dots of the gradation “1” and higher is inputted to a shift register (not shown) in the driver IC41. Then as shown inFIG. 7, the gradation pattern data, inputted to the shift register at the timing that the latch signal enters the low level from the high level, is retained by the latch signal which is not shown. Then power is supplied to the minute portion of the heating resistor30to be heated, determined based on the gradation pattern data, in a period where the strobe signal enters the low level. Thus, the heating resistor30is selectively heated, and the data corresponding to the dots of the gradation “1” and higher is printed on the recording paper.

The subsequent gradation pattern data containing the data corresponding to the dots of the gradation “2” and higher is transferred to the shift register, in the period where the power is supplied to the heating resistor30for printing the dots of the gradation “1” and higher. Then the same process as above is executed, so that the data corresponding to the dots of the gradation “2” and higher is printed. In this case, the dots of the gradation “2” and higher are printed over the dots of the gradation “1”, which have been printed in the first printing process. Such data transfer and printing action are repeated up to the gradation pattern data corresponding to the dots of the gradation “255 (=black)”. With respect to the dots of the gradation “0 (=white)”, such printing process is not executed while the gradation pattern data corresponding to the gradation “1” to “255” is printed, and the region on the recording paper corresponding to the dots that have remained unprinted during the printing process from the gradation “1” to the gradation “255” resultantly represents the white portion corresponding to the gradation “0”.

The control chip42then decides whether all the lines of the recording paper have been printed (S7). In the negative case (S7: NO), the process returns to the step S5and the printing command for printing the next line is transferred. In the case where it is decided at the step S7that all the lines have been printed (S7: YES), the printing action is finished.

The thermal print head11and the thermal printer16provide the following advantageous effects.

In this embodiment, the control chip42and the memory chip44are mounted on the thermal print head11. Such structure allows transferring the gradation pattern data, a conversion of the image data, and the control signal such as the clock signal, from the control chip42to the driver IC41through the signal line67. Accordingly, the gradation pattern data and the clock signal can be transferred to the driver IC41at a higher speed, compared with the conventional way that the gradation pattern data and the clock signal are transferred through the signal line connecting the thermal printer990and the thermal print head999. Consequently, the printing speed can be significantly increased, without suffering data deficiency and impact of the signal radiation.

The action control unit161of the thermal printer16and the thermal print head11are connected via the I2C signal line163formed in accordance with the I2C specification, which is widely applicable. Such configuration facilitates the connection, for example, between the thermal print head11and the thermal printer16, and expands the applicability of the thermal print head11.

In this embodiment, also, the control chip42and the memory chip44are mounted on the circuit board22via the IC socket421,441. In the case, for example, where the heating resistor30of the thermal print head11deteriorates after years of use, it would be appropriate to replace the thermal print head11as a whole. In this case, the original control chip42can be continuously utilized with the new thermal print head, by removing it from the IC socket421and mounting it on the IC socket of the new thermal print head. Thus, employing the IC socket421leads to reduction in cost. Likewise, the memory chip44, which is also mounted on the IC socket441, can also contribute to reducing the cost.

The thermal print head11and the thermal printer16according to this embodiment are also applicable in such case where both image data and character data (or 2 gradation data such as a barcode) are to be printed on a single recording paper70.

Such case will be described hereunder with reference to a plurality of recording papers70, on which an image region71where the image data is to be printed and a character region72where the character data is to be printed are both defined, for example as shown inFIG. 8. In the case where both the image data and the character data are to be printed, the action control unit161of the thermal printer16collectively transfers the image data and the character data to the control chip42of the thermal print head11. To be more detailed, the action control unit161transfers, upon receipt of the data to be printed on the recording paper70from outside, the image data and the character data collectively, to the control chip42through the I2C signal line163.

The control chip42generates the gradation pattern data from the image data transferred from the action control unit161, and stores the gradation pattern data in the memory chip44. The control chip42also stores the character data in the memory chip44. At this moment, the control chip42stores position information of the image region71and the character region72, together with the foregoing data.

Once the printing command is transferred from the action control unit161to the control chip42, the printing process for the first one line is executed. Here, in the case where both the image data and the character data are included in the first line (uppermost line) as shown on the recording paper70ofFIG. 8, the control chip42retrieves the gradation pattern data, corresponding to the image data for the first line in the image region71, from the memory chip44. The control chip42also retrieves the character data for the first line in the character region72. The control chip42outputs those data to the driver IC41, and in the case, for example, where the gradation pattern data represents 256 gradations, the printing process is executed 255 times as described above. On the other hand, with respect to the character data, the printing process is not executed for the data “0 (=white)”, but executed 255 times for the data “255 (=black)”.

Through such steps, the image data and the character data for the first line of the image region71and the character region72are respectively printed. Thereafter the gradation pattern data and the character data for each line are sequentially outputted, from the second line to the final line, to the driver IC41, so that the printing is executed on the entire region of the recording paper70.

To print the image data and the character data on the second sheet of the recording paper70, the control chip42compares the image data and the character data to be printed on the second recording paper70, transferred from the action control unit161, with the image data and the character data for the first recording paper70. In the case, for example, where the image data is the same, the image data (gradation pattern data) already stored in the memory chip44is retrieved, for reutilization for the printing process on the second recording paper70. Also, in the case where only a portion of the character data (for example, date, address, and the like) is different, the character data corresponding to the common portion is retrieved from the memory chip44for reutilization. Then only the character data corresponding to the different portion is newly stored in the memory chip44, for retrieval when executing the printing process. With respect to the third and subsequent sheets of the recording paper70, the printing process is executed in the same way.

On the recording paper70on which the printing is executed by the thermal printer16, the layout of the image region71and the character region72is often fixed or patternized. Accordingly, reutilizing the common portion of the image data and the character data as above allows skipping the generation of the gradation pattern data of the common portion and storage thereof in the memory chip44. Such arrangement therefore contributes to increasing the printing speed and simplifying the printing process. This advantage can be prominently enjoyed with the image data, since the image data contains an enormous data amount.

Further, the thermal printer16may be incorporated, for example, in a label printing machine that prints logistic labels. The label printing machine is capable of printing a plurality of types of labels. The label printing machine is designed so as to automatically replace the recording papers according to different types of labels. Employing the thermal printer16according to this embodiment contributes to reducing a total printing time, as described hereunder.

FIG. 9is a flowchart showing an example of the printing action executed by the label printing machine. By the label printing machine, for example a first printing action for a predetermined label is executed (S11). Once an instruction to replace the label to be printed is inputted (S12), the label printing machine automatically replaces the recording paper according to such instruction, with the one to be used for printing the next label (S13).

At this moment, in parallel with the replacing action (S13), the printing data necessary for printing the next label is transferred from the label printing machine to the thermal printer16(S14). In the thermal printer16the printing data is transferred to the thermal print head11, and stored in the memory chip44(S15). Upon completion of the replacement of the recording paper, a second printing action for the next label is started (S16).

In the case where the thermal printer16is incorporated in the label printing machine, the replacement of the recording paper, the data transfer to the thermal print head11, and the data processing in the thermal print head11are executed at the same time. Thus, since the printing of the next label is immediately started when the next recording paper is set, waste of time between the printing actions can be minimized, which contributes to reducing the total printing time.

FIGS. 10 to 16depict other embodiments of the present invention. In these drawings, the constituents same as or similar to those of the foregoing embodiment are given the same numeral.

FIG. 10is a block diagram of a printer system constituted of a plurality of thermal printers each including a thermal print head according to a second embodiment of the present invention. In the printer system18, the plurality of thermal printers17is connected to the control unit182through the I2C signal line163, so as to make data communication.

To be more detailed, the printer system18includes, as shown inFIG. 10, a control unit182connected to a personal computer181for example, and the plurality of thermal printers17connected to the control unit182in a bus configuration through the I2C signal line163. In the printer system18, for example the control unit182may serve as the master device, and the plurality of thermal printers17as the slave device.

The control unit182includes for example a microcomputer, and integrally controls the printing action of the thermal printers17connected thereto through the I2C signal line163. The control unit182includes an integral action control unit (not shown), which corresponds to the action control unit161of the thermal printer16shown inFIG. 2.

The thermal printer17includes a thermal print head12as shown inFIG. 11. The thermal print head12has generally the same structure as that of the thermal print head11. The thermal printer17is without the action control unit161shown inFIG. 2. In the thermal printer17, the I2C signal line163from the control unit182is directly connected to the control chip42of the thermal print head12via the connector64or another connector which are not shown. To the control chip42, the motor control unit164and a control unit (not shown) are connected, which is the difference from the thermal print head11.

Thus, in the printer system18, the control unit182transmits the data to be printed to the respective thermal printers17through the I2C signal line163. The control unit182also transmits the motor control signal for controlling the motor control unit164in a form of a command signal, to thereby control the printing action of the respective thermal printers17.

In the communication according to the I2C specification, the control unit182and the plurality of thermal printers17can be operated under the relationship of the master device and the slave devices, as stated above. For example, various data such as image data and specific command signal can be transmitted in a predetermined data format, from the master device to the slave device by designating the address. In the case, for example, where a user wants to output an image picked up by a scanner (not shown) to one of the thermal printers17through the personal computer181, the user can operate the personal computer181so as to transmit the image data that ahs been picked up to the control unit182. The control unit182transmits the image data received from the personal computer181to the thermal printer17selected by the user, through the I2C signal line163. The selected thermal printer17stores the transmitted image data directly in the memory chip44of the thermal print head12.

Then the control unit182transmits the printing command to the selected thermal printer17through the I2C signal line163. The control chip42of the thermal print head12transmits, upon receipt of the printing command, the motor control signal to the motor control unit164. Further, the control chip42outputs the image data and the control signal (clock signal, latch signal, and strobe signal) to the driver IC41, to thereby start the printing action. In this case, the control signal (clock signal, latch signal, and strobe signal) is outputted to the driver IC41through the signal line67, and therefore high-speed printing can be executed.

Constituting thus the printer system18by means of the I2C signal line163allows integrally controlling the printing action of the plurality of thermal printers17with a single control unit182. Also, an enormous amount of data can be transmitted to the thermal print head12of the respective thermal printers17directly and at a high speed, through the I2C signal line163. Accordingly, the respective thermal printers17can execute high-speed printing despite that the data contains enormous image data. Further, the exclusion of the action control unit161from the thermal printers17contributes to simplifying the internal configuration.

Naturally, the thermal printer16(including the action control unit161) shown inFIG. 2may be connected to the control unit182through the I2C signal line163, in place of the thermal printer17shown inFIG. 11. Alternatively, the thermal printer16and the thermal printer17may be mixedly connected to the control unit182, in the printer system18.

FIGS. 12 and 13illustrate a thermal print head according to a third embodiment of the present invention. The thermal print head13according to this embodiment is different from that of the foregoing embodiments in including a coil antenna51, a magnetic sheet52, a driver IC45, a connector65, and a cover80. The thermal print head13can be incorporated for example in a Radio Frequency IDentification (RFID) tag printer through the connector64,65as will be subsequently described, for executing the printing on an RFID tag sheet70, corresponding to the recording paper70, and data transmission/reception to and from the RFID tag sheet70. Here, an encapsulating resin49shown inFIG. 13is omitted inFIG. 12.

The RFID tag sheet, an example of the recording paper70for the thermal print head13will hereunder be described. The recording paper70is constituted as the RFID tag sheet, including for example a base paper74and a plurality of RFID tags75arranged thereon. The RFID tags75each include a memory, a target-side coil antenna, a printing sheet, and an adhesive sheet (all not shown), and are employed as a tag for luggage management at an airport, for example. The memory electronically stores identification data, such as the identification data for handling the luggage. The target-side coil antenna serves for data transmission/reception to and from the thermal print head13by wireless communication. The printing sheet is employed for printing a letter, symbol, barcode and the like corresponding to the identification data, and is made of a resin sheet or paper strip containing a thermosensitive coloring particle. The adhesive sheet is used to stick the RFID tag75to the luggage. For the data transmission/reception by wireless communication with the RFID tag75, for example a frequency of 13.56 MHz is assigned by the Radio Law. The wireless communication in this frequency band is made according to what is known as electromagnetic induction. To execute the printing on the recording paper70thus configured and the data transmission/reception with the RFID tag75, the thermal print head13is configured as described hereunder.

The front face211of the heating function unit21includes a slanted portion213located close to an edge of a side thereof. Because of the presence of the slanted portion213, the RFID tag sheet, acting as the recording paper70, is placed with an inclination with respect to the thermal print head13, as shown inFIG. 13.

On the slanted portion213, the partial glaze214is provided. The heating resistor30is located on the partial glaze214. To effectively conduct the heat from the plurality of heating resistors30to the recording paper70, for example a platen roller192may be employed for pressing the recording paper70against the heating resistor30.

The driver IC41is covered with the encapsulating resin49, for protection from an impact and electromagnetic shielding.

The coil antenna51and the driver IC45constitute the data transmitter/receiver according to the present invention, and is located on the front face221of the circuit board22. The coil antenna51is constituted of Cu for example, and formed through depositing a Cu layer on the front face221and patterning the Cu layer by etching or the like. When a current is supplied to the coil antenna51, an electromagnetic field90is generated as shown inFIG. 13, according to the direction and magnitude of the current. In this embodiment, the driver IC45is located outside the coil antenna51as shown inFIG. 12. In the wiring connecting the coil antenna51and the driver IC45, a path extending from inside the coil antenna51to the driver IC45is insulated from the coil antenna51via an insulating layer (not shown). Otherwise, a through hole may be formed to thereby secure such path on the back face222of the substrate22. Providing the path on the back face222is advantageous for enhancing the effect of the electromagnetic field90to the object.

The magnetic sheet52serves to suppress the electromagnetic field90generated by the coil antenna51from unduly expanding downward according to the orientation ofFIG. 13. The magnetic sheet52may be a resin sheet containing for example ferrite powder serving as a magnetic material, and is provided on the back face222of the circuit board22in this embodiment. The magnetic sheet52has relatively high magnetic permeability but suffers relatively small electrical loss. Accordingly, the electromagnetic field90selectively passes through the magnetic sheet52, and undesired heating in the magnetic sheet52can be suppressed. Examples of such magnetic sheet52include Flexield (registered trademark) manufactured by TDK Corporation.

As is apparent fromFIG. 13, in this embodiment the heat dissipater23is deviated to the left in the sub scanning direction from the coil antenna51, in other words located so as not to overlap with the coil antenna51when viewed thicknesswise of the heating function unit21and the circuit board22.

The cover80covers the whole of the control chip42, the quartz oscillator43, and the memory chip44, and a portion of the driver IC41, and is constituted of a conductive resin containing a mixture of a black resin and carbon graphite. The cover80includes an upper portion81and a lower portion82. The upper portion81and the lower portion82hold the circuit board22therebetween. In other words, the cover80is attached to the circuit board22. As shown inFIGS. 12 and 13, the cover80includes a plurality of openings83. In this embodiment, the openings83are aligned in the main scanning direction. The dimension of the openings83in the main scanning direction is smaller than a width (dimension in main scanning direction) of the recording paper70.

FIG. 14is a block diagram of the RFID tag printer including the thermal print head13. The RFID tag printer19includes the thermal print head13, the action control unit161, the motor control unit164, and the printing mechanism165. To the driver IC45, the identification data is transmitted from the action control unit161via the connector65. The driver IC45includes a circuit formed therein that controls the generation of the electromagnetic field90by the coil antenna51, according to the identification data. The driver IC45adjusts the electromagnetic field90to the foregoing frequency of 13.56 MHz. The driver IC45may also have a processing function for receiving the identification data recorded on the recording paper70, in addition to the transmission of the identification data. The receiving function can also be executed by wireless communication, according to the electromagnetic induction method utilizing the electromagnetic field90.

Hereunder, description will be given on the printing process on the recording paper70and the data transmission/reception with the recording paper70executed by the RFID tag printer19.

First, the identification data corresponding to the respective RFID tags75is transmitted from an external personal computer (not shown) to the action control unit161. Then the recording paper70is delivered according to the instruction from the action control unit161. During the delivery of the recording paper70, tracking of the RFID tag75is executed with an approximation sensor or the like.

When the RFID tag75reaches an upper position of the thermal print head13, the action control unit161transmits instructions to the thermal print head13so as to execute the printing process S1to S7of the flowchart shown inFIG. 15. The process S1to S7is the same as that described referring toFIG. 5. Through such printing process, the letter, symbol, barcode and the like corresponding to the identification data are printed on theRFID tag75.

When the printing process is completed, the action control unit161transmits an instruction to the thermal print head13, so as to start the data transmission/reception between the thermal print head13and the RFID tag75(S8). By this step the electromagnetic field90is generated by the coil antenna51, so that the wireless communication based on the electromagnetic induction is made with the RFID tag75. From the electromagnetic field90, power supply for activating the RFID tag75and transmission of the identification data are simultaneously executed to the RFID tag75. Accordingly, the identification data corresponding to the respective RFID tag75is recorded on the relevant RFID tag75. In the case where the thermal print head13or the RFID tag printer19has the data receiving function, the identification data recorded on the RFID tag75is received through the coil antenna51of the thermal print head13, immediately after the transmission of the identification data. In this case, for example, the action control unit161can check whether the identification data recorded on the RFID tag75is correct. Here, the data transmission/reception (S8) may be executed after the completion of the steps S1to S7, or in parallel therewith.

Thereafter, the RFID tag75is discharged out of the RFID tag printer19. The RFID tag75, printed and bearing the identification data recorded thereon, is removed by the user from the base paper and stuck to an object of management such as a luggage. The luggage with the RFID tag75stuck thereto can be easily controlled using an RFID tag reader or the like, at the departing airport, in the aircraft, the arriving airport, and so forth.

According to this embodiment, both the printing and the data transmission can be executed by utilizing the thermal print head13alone. Such configuration eliminates the need to employ, for example, a coil antenna for the purpose of data transmission/reception, in addition to the thermal print head13. This enables reducing the dimensions of the RFID tag printer19.

Providing the coil antenna51on the circuit board22allows reducing the dimensions of the thermal print head13itself. This is advantageous for reducing the dimensions of the RFID tag printer19. Also, the structure according to this embodiment prevents interference between the coil antenna51and the platen roller192.

Also, providing the coil antenna51in the thermal print head13allows locating the coil antenna51at a position sufficiently close to the RFID tag75. Here, the thermal print head13is configured to execute the printing on the RFID tag75, the print target, in contact therewith. Accordingly, locating the coil antenna51in the thermal print head13facilitates locating the coil antenna51close to the RFID tag75. Locating the coil antenna51closer to the RFID tag75can make the RFID tag75pass through a region in the electromagnetic field90where the magnetic field is more intense. Such configuration allows minimizing a failure that the magnetic field intensity acting on the RFID tag75falls below a minimum working intensity of magnetic field specified for the RFID tag75. Also, higher intensity of the magnetic field is advantageous for increasing the reliability and speed of the data transmission/reception based on the electromagnetic induction. In particular, locating the coil antenna51on the front face221of the circuit board22enables the coil antenna51to directly confront the RFID tag75.

The magnetic sheet52suppresses the electromagnetic field90from unduly expanding downward according to the orientation ofFIG. 13. Such structure can increase the magnetic field intensity of the portion of the electromagnetic field90extending upward inFIG. 13, and hence contributes to further increasing the reliability and speed of the data transmission/reception with the RFID tag75.

Forming the opening83on the cover80allows preventing the electromagnetic field90from being unduly weakened by the cover80. This also contributes to increasing the reliability and speed of the data transmission/reception with the RFID tag75. Making the dimension of the opening83in the main scanning direction smaller than the width (dimension in main scanning direction) of the recording paper70minimizes the risk that the recording paper70is accidentally caught by the opening83.

The thermal print head, the thermal printer, and the printer system according to the present invention are not limited to the foregoing embodiments. Specific structure of the constituents of the thermal print head, the thermal printer, and the printer system according to the present invention may be modified in various manners.

For example, although the I2C specification is adopted for transmission of the image data between the thermal print head11and the thermal printer16in the embodiments, for example a Low Voltage Differential Signaling (LVDS) or another serial communication method that is relatively inexpensive and fast may be adopted instead. The LVDS provides the advantage of suppressing power consumption in the high-speed communication by utilizing a relatively low voltage, and also suppressing a noise because of utilizing the differential signal.

Further, although the embodiment exemplifies the case where the thermal print head prints the image data in monochrome, the thermal print head according to the present invention may also be utilized for printing the image data in colors. More particularly, the thermal print head according to the present invention can be suitably employed for printing the gradations of yellow, magenta, and cyan. Alternatively, the thermal print head according to the present invention may be utilized for two-color printing, where the heating resistor is heated at different temperatures to thereby print two colors (such as red and black, or blue and black).