JP2018187852A - Thermal print head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to control a calorific value with high accuracy in a thermal print head without addition of a driver IC.SOLUTION: A thermal print head comprises: a substrate; plural first heat elements which are arranged on the substrate at intervals in a main-scanning direction; a folding electrode which connects first ends of a pair of first heat elements adjacent to the plural first heat elements; a first common electrode which is connected to a second end of one first heat element among the pair of first heat elements, which is not connected to the folding electrode; an individual electrode which is connected to a second end of the other first heat element among the pair of heat elements, which is not connected to the folding electrode; and plural second heat elements which are arranged on the substrate at intervals in the main-scanning direction. Each of the plural second heat elements has one end which is connected to the folding electrode, and the other end which is connected to a second common electrode.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermal print head used in a printer.

  2. Description of the Related Art Conventionally, printers are known that include a thermal print head in which a plurality of heating resistors are arranged and a platen roller disposed so as to face the thermal print head. Such a printer is configured to print on a print medium by pressing a thermal print head against the print medium conveyed on the platen roller. There are a method of pressing the thermal print head from above the ink ribbon and a method of printing directly by the thermal print head by using a heat-sensitive printing medium.

  A conventional thermal print head is known in which two heating resistors are provided corresponding to each of a plurality of dots included in one line (for example, Patent Documents 1 and 2). For example, according to the thermal print head of Cited Document 1, the amount of heat generated by two heating resistors is adjusted so as not to cause sticking.

JP 2002-370398 A JP 2008-126513 A

  In the thermal print head described in Patent Document 1, the amount of heat generation is adjusted by independently applying a voltage to the heat generating portion and the second heat generating portion, but the heat generating portion and the second heat generating portion are the same. They are arranged close to the line (for example, see the heat generating portion 14 and the second heat generating portion 15 in FIG. 2). Therefore, even when the voltage application to one of the heat generation parts is turned off, the heat generation of the other heat generation part may heat the one heat generation part with the voltage application turned off to an extent that can be printed. Therefore, it is difficult to control the calorific value with high accuracy.

  The thermal print head described in Patent Document 2 is configured to provide two heating resistor rows on one line and perform independent driving for each heating resistor row. In such a configuration, although it is possible to control the heat generation amount with high accuracy, two independent driver ICs are required for each heating resistor array, so that the thermal print head becomes expensive.

  SUMMARY OF THE INVENTION An object of the present invention is to make it possible to control a heat generation amount with high accuracy without adding a driver IC in a thermal print head.

An aspect of the present invention provides:
A substrate,
A plurality of first heating resistors arranged at intervals in the main scanning direction on the substrate;
A folded electrode that connects first ends of a pair of first heating resistors adjacent to each other of the plurality of first heating resistors;
A first common electrode connected to a second end of one of the pair of first heating resistors that is not connected to the folded electrode of the first heating resistor;
An individual electrode connected to a second end of the other first heating resistor of the pair of first heating resistors that is not connected to the folded electrode;
A plurality of second heating resistors arranged at intervals in the main scanning direction on the substrate;
With
Each of the plurality of second heating resistors has a first end connected to the folded electrode and a second end connected to the second common electrode.
It is a thermal print head.

  According to an aspect of the present invention, in a thermal print head, it is possible to control the amount of heat generation with high accuracy without adding a driver IC.

It is a top view of the thermal print head concerning an embodiment. It is a figure which shows the equivalent circuit of the thermal print head which concerns on embodiment. It is a timing chart which shows operation of a thermal print head concerning an embodiment.

(1) Configuration of Thermal Print Head According to Embodiment Hereinafter, a thermal print head according to an embodiment of the present invention will be described.
FIG. 1 is a plan view of a thermal print head 1 according to the embodiment. As shown in FIG. 1, in the thermal print head 1 of the present embodiment, a plurality of heating resistors (a plurality of first heating resistors and a plurality of second heatings described later) are spaced apart on the substrate ST in the main scanning direction. Including resistors.) Arranged in a line. Here, the main scanning direction (direction D1 in FIG. 1) means a direction orthogonal to the conveyance direction of the print medium. The sub-scanning direction (direction D2 in FIG. 1) is the same direction as the conveyance direction of the print medium. In the printer using the thermal print head 1 of the present embodiment, selection on each line is performed by selectively generating heat from a plurality of heating resistors arranged in the main scanning direction while transporting the print medium in the sub scanning direction. A dot (point) is formed at the position.

The thermal print head 1 shown in FIG. 1 includes a pair of first heating resistor group R1 and second heating resistor group R2. The pair of first heating resistor groups R1 includes first heating resistors R11_1,..., R11_n and first heating resistors R12_1,. The second heating resistor group R2 includes second heating resistors R2_1,..., R2_n.
The thermal print head 1 is configured so that n dots can be printed in one line. For example, a pair of first heating resistors R11_1 and R12_1 and a second heating resistor R2_1 are provided corresponding to the first dot. A pair of first heating resistors R11_2 and R12_2 and a second heating resistor R2_2 are provided corresponding to the second dot. Similarly, a pair of first heating resistors R11_n and R12_n and a second heating resistor R2_n are provided corresponding to the nth dot.

  The pair of first heating resistor groups R1 is provided for printing one line, and the second heating resistor group R2 is provided for controlling the amount of heat generated before or after printing for one line. ing.

  In the following description, one end of the heating resistor is referred to as a first end, and the other end of the heating resistor is referred to as a second end. That is, the first end and the second end mean opposite ends.

  Focusing on the electrode pattern of FIG. 1, the first end of one first heating resistor R11_1,..., R11_n and the first end of the other first heating resistor R12_1,. The individual electrodes E2_1,..., E2_n are connected to each other. The folded electrode corresponds to an intermediate node of the pair of first heating resistors. In the following description, the individual electrodes E2_1,..., E2_n are appropriately referred to as folded electrodes.

The second ends of the first heating resistors R11_1,..., R11_n (that is, the ends opposite to the first ends and not connected to the return electrode) are all applied with the first voltage VP. 1 is connected to the common electrode pattern 3.
The second ends of the other first heating resistors R12_1,..., R12_n (that is, the ends opposite to the first ends and not connected to the folded electrodes) are connected to the individual electrodes E1_1,. Has been.
The first voltage VP is provided to generate heat by flowing a current through the pair of first heating resistor groups R1 during printing.

  The driver IC (Integrated Circuit) 2 has individual terminals Out_1, ..., Out_n. The individual terminals and the individual electrodes E1_1,..., E1_n are electrically connected by bonding wires BW_1,.

Referring further to FIG. 1, a second heating resistor is formed on the opposite side of the first heating resistor across the folded electrodes E2_1,..., E2_n. That is, the first ends of the second heating resistors R2_1,..., R2_n are connected to the folded electrodes E2_1,. The second ends of the second heating resistors R2_1,..., R2_n are all connected to the second common electrode pattern 4 to which the second voltage VH is applied.
The second voltage VH is provided to control the amount of heat generated by causing a current to flow through the second heating resistor group R2 before or after printing.

Although the internal configuration of the driver IC 2 will be described later, the driver IC 2 receives the pair of first heating resistors and the first via the individual terminals Out_1,..., Out_n according to a strobe signal (not shown in FIG. 1). 2 is a driving circuit for generating heat by selectively passing a current through the heating resistor.
The first voltage VP of the first common electrode pattern 3 and the second voltage VH of the second common electrode pattern 4 are, for example, from an external printer circuit board (not shown) via a connector or a flexible cable (not shown). Input to the thermal print head 1.

  In the thermal print head 1 shown in FIG. 1, the heating resistor and the electrode having a predetermined pattern can be formed by using a known technique. For example, a substrate ST made of alumina, silicon, or the like is prepared, a glaze layer is formed thereon, and a heating resistor and an electrode are formed on the glaze layer. Then, it is possible for those skilled in the art who have seen the present disclosure to pattern the heating resistor and the electrode so as to have the shape shown in FIG. 1 by using a photolithography technique.

(2) Circuit Configuration and Operation of Thermal Printhead According to Embodiment Next, the circuit configuration and operation of the thermal printhead 1 according to the present embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a diagram showing an equivalent circuit of the thermal print head 1 according to the present embodiment. 4 is a timing chart showing an operation example of the thermal print head 1 according to the present embodiment.

First, the circuit configuration of the thermal print head 1 will be described with reference to FIG. As shown in FIG. 2, the driver IC 2 includes at least a shift register (S / R) 21 and a latch circuit (L) 22 for temporarily storing print data DATA for one line, a gate circuit group 23, Inverter 24 is included.
The driver IC 2 operates in accordance with the print data DATA, the clock signal CLK, the latch signal LATCH, and the strobe signal STB. These data and signals are supplied from, for example, an external printer circuit board (not shown) to a connector not shown. Alternatively, it is input to the thermal print head 1 via a flexible cable.

  Print data DATA for one line is input to and held in the shift register 21 in synchronization with the clock signal CLK. The print data DATA is composed of a bit string having a high level in the case of “printing” and a low level in the case of “non-printing”. The latch circuit 22 is connected to the shift register 21 in parallel, and each bit data on the shift register 21 is transferred and held simultaneously in parallel. Data transfer timing from the shift register 21 to the latch circuit 22 is controlled by a latch signal LATCH.

The gate circuit group 23 includes NAND gate circuits 23_1, 23_2,..., 23_n corresponding to the first to nth dots of one line, respectively. An inverted signal of strobe signal STB (output signal of inverter 24) is supplied to one input terminal of each gate circuit, and the other input terminal of each gate circuit is connected to the output of latch circuit 22.
Each gate circuit of the gate circuit group 23 takes the logical product of the corresponding print data DATA and the inverted signal of the strobe signal STB, inverts the result, and outputs the result. The output terminal of each gate circuit of the gate circuit group 23 is connected to the individual terminals Out_1 to Out_n of the driver IC 2.

  Therefore, while the strobe signal STB is at the low level, the logical level of the individual terminals Out_1 to Out_n is the output level of the latch circuit 22 inverted. For example, when the output level of the latch circuit 22 is a high level indicating “printing”, the level of the corresponding individual terminal is a low level (for example, a ground level with a voltage value), and thus the first voltage VP or the second voltage VH. If an effective voltage is set, current flows toward the individual terminal. Conversely, when the output level of the latch circuit 22 is a low level indicating “non-printing”, the level of the corresponding individual terminal is the same as the voltage set to the first voltage VP and the second voltage VH (for example, Therefore, even if an effective voltage is set as the first voltage VP or the second voltage VH, no current flows toward the individual terminal.

  Although not shown, the second common electrode pattern 4 includes a second common electrode pattern 4 so that a current flowing from the first voltage VP does not flow into the second common electrode pattern 4 when an effective voltage is applied as the first voltage VP. It is preferable that a diode for preventing backflow is connected or that the circuit is electrically interrupted. Similarly, in order to prevent a current flowing from the second voltage VH from flowing into the first common electrode pattern 3 when an effective voltage is applied as the second voltage VH, the first common electrode pattern 3 has a backflow prevention function. It is preferable that the diode is connected or that the circuit is electrically cut off.

Next, the operation of the thermal print head 1 will be described with reference to FIG. FIG. 3 illustrates the signal levels of print data DATA, clock signal CLK, latch signal LATCH, strobe signal STB, first voltage VP, and second voltage VH over time when printing one line. Is.
The operation example shown in FIG. 3 shows an operation in the case where heat is generated by the second voltage VH after printing by the first voltage VP in a one-line printing cycle from time T0 to time T4.

  The print data DATA for one line given to the driver IC 2 immediately before time T0 is sequentially input and stored in the shift register 21 in synchronization with the timing of the clock signal CLK. When the latch signal LATCH becomes low level at time T 0, the print data DATA for one line is transferred from the shift register 21 to the latch circuit 22 and held in the latch circuit 22. Note that immediately before time T0, the strobe signal STB is at a high level, and the first voltage VP and the second voltage VH are 0V.

Next, between time T0 and time T1, the strobe signal STB is set to the low level, and the first voltage VP is set to the voltage V1. Accordingly, a pair of first heating resistors R11_x and R12_x (x: 1 to n) provided between the first common electrode pattern 3 and the individual terminals of the driver IC 2 are energized, and printing is performed. Note that the period from time T0 to time T1 is an example of the first period.
The strobe signal STB is returned to the high level from time T1 to time T2 when printing is completed, and the first voltage VP is set to 0V. Therefore, from time T1 to time T2, no heating resistor is energized and no heat is generated.

As shown in FIG. 3, until the time T2, data DATA for heat generation by the second voltage VH is sequentially input and stored in the shift register 21 in synchronization with the timing of the clock signal CLK. When the latch signal LATCH becomes low level again at time T2, the data DATA for one line is transferred from the shift register 21 to the latch circuit 22 and held in the latch circuit 22.
Here, since the data DATA held in the latch circuit 22 at time T2 is not print data, the content of the data may be set as appropriate. The data may be the same data as the print data DATA held in the latch circuit 22 at time T0, or may be set as appropriate according to the purpose.

Next, between time T2 and time T3, the strobe signal STB is set to the low level, and the second voltage VH is set to the voltage V2. Thereby, the second heating resistor R2_x and the first heating resistor R12_x (x: 1 to n) provided between the second common electrode pattern 4 and the individual terminals of the driver IC 2 are energized to generate heat. Note that the period from time T2 to time T3 is an example of the second period.
From time T3 to time T4, the strobe signal STB is returned to the high level, and the second voltage VH is set to 0V. Therefore, neither heating resistor is energized from time T3 to time T4.
Here, as shown in FIG. 3, the print data DATA for printing the next one line is given to the driver IC 2 immediately before time T4, and sequentially to the shift register 21 in synchronization with the timing of the clock signal CLK. It is input and stored.
The printing cycle for one line described above is repeated.

(3) Example Hereinafter, the case where a specific resistance value is applied in the above-described embodiment will be described.
For example, the pair of first heating resistors R11_x and R12_x (x: 1 to n) is 400Ω (total 800Ω), and the second heating resistors R2_x (x: 1 to n) are 1200Ω. In FIG. 3, it is assumed that V1 and V2 are each 24V.
In this case, if the internal loss is ignored, the power consumption when performing printing is 0.72 W in total for the pair of first heating resistors R11_1 and R12_1, for example. On the other hand, when heat is generated by the second voltage VH, the power consumption of the second heating resistor R2_1 is 0.27W, and the power consumption of the first heating resistor R12_1 is 0.09W.
In this setting example, the power consumption when controlling the amount of heat generated by the second voltage VH can be made lower than the power consumption when printing is performed by the first voltage VP (that is, the power consumption is such that printing is not performed). It can be set). The ratio between the power consumption when printing and the power consumption when controlling the amount of heat generation (that is, when heat is generated by the second voltage VH) is the resistance of the pair of first heating resistor and second heating resistor. It is possible to set a desired value by adjusting the value.

According to the configuration of the thermal print head 1 of the present embodiment, by appropriately setting the resistance value of each heating resistor, the amount of heat generated when heat is generated by the second voltage VH is increased to a level that allows printing. It is possible to set to the target calorific value without any problem. The target heat generation amount may be set as appropriate. For example, an effective heat generation amount for preventing sticking after printing can be set.
Further, in the thermal print head 1 of the present embodiment, not only the resistance value of the heating resistor described above but also the value of the second voltage VH and / or the length of the strobe signal STB (low level in FIG. 3). The calorific value can be controlled by adjusting the period.

  As described above, in the thermal print head 1 according to this embodiment, the pair of first heating resistors are connected between the first voltage for printing and the driver IC by the folded electrodes, and the second voltage for heating is used. The second heating resistor is provided between the electrode and the folded electrode. Furthermore, one end of the first heating resistor that is not directly electrically connected to the driver IC among the pair of first heating resistors is connected to the first common electrode pattern, and one end of the second heating resistor is connected to the second common electrode. It was comprised so that it might connect with an electrode pattern. Therefore, by adjusting the resistance values of the pair of first heating resistor and second heating resistor without increasing the number of driver ICs, the target amount of heat generation can be realized with high accuracy.

As mentioned above, although one embodiment of the thermal print head of the present invention was described in detail, the present invention is not limited to the above embodiment. The above-described embodiment can be variously improved and changed without departing from the gist of the present invention.
For example, in the operation example shown in FIG. 3, the case where heat is generated by the second voltage VH after printing in the printing cycle of one line has been described, but the present invention is not limited thereto. In one line printing cycle, heat may be generated by the second voltage VH before printing (preheating).

1 ... Thermal print head 2 ... Driver IC
DESCRIPTION OF SYMBOLS 21 ... Shift register 22 ... Latch circuit 23 ... Gate circuit group 23_1 to 23_n ... Gate circuit (NAND gate)
24 ... Inverter 3 ... First common electrode pattern 4 ... Second common electrode pattern ST ... Substrate R1 ... First heating resistor group R11_1-R11_n ... First heating resistor R12_1-R12_n ... First heating resistor R2 ... Second Heating resistor group R2_1 to R2_n ... second heating resistor E1_1 to E1_n ... individual electrode E2_1 to E2_n ... individual electrode (folded electrode)
Out_1 to Out_n ... individual terminals BW_1 to BW_n ... bonding wires VP ... first voltage VH ... second voltage

Claims (2)

A substrate,
A plurality of first heating resistors arranged at intervals in the main scanning direction on the substrate;
A folded electrode that connects first ends of a pair of first heating resistors adjacent to each other of the plurality of first heating resistors;
A first common electrode connected to a second end of one of the pair of first heating resistors that is not connected to the folded electrode of the first heating resistor;
An individual electrode connected to a second end of the other first heating resistor of the pair of first heating resistors that is not connected to the folded electrode;
A plurality of second heating resistors arranged at intervals in the main scanning direction on the substrate;
With
Each of the plurality of second heating resistors has a first end connected to the folded electrode and a second end connected to the second common electrode.
Thermal print head. In a one-line printing cycle, a first period in which a printing voltage is applied to the first common electrode, and a second period in which a voltage is applied to the second common electrode, which is set subsequent to the first period. Have
The thermal print head according to claim 1.

Images