thermal printhead

Abstract

To provide a thermal print head which can protect an element.SOLUTION: A thermal print head according to an embodiment comprises: a heating resistor; a drive circuit which controls electric conduction of the heating resistor; input signal wiring and power supply wiring connected to the drive circuit; an input signal electrode which is electrically connected to the drive circuit via the input signal wiring; an output signal electrode which is electrically connected to the drive circuit; a power supply electrode which is electrically connected to the drive circuit via the power supply wiring; a ground electrode which is electrically connected to the drive circuit; and shield wiring which is electrically connected to the output signal electrode or the ground electrode. The shield wiring is arranged so as to be apart from the power supply wiring or the input signal wiring such that a current by electrostatic discharge applied to the power supply electrode or the input signal electrode can be conducted.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present embodiment relates to a thermal printhead. [Background technology]

[0002] Electrostatic discharge (ESD) is known to be a phenomenon that can damage semiconductor devices and large scale integrated circuits (LSIs). ESD often occurs when a statically charged conductor or a person approaches or touches an external terminal of a semiconductor device, and it is known that ESD current flows inside the LSI, causing fluctuations in the characteristics of elements within the LSI and damage to wiring. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-154870 Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, if ESD current flows into the LSI from an unprotected input terminal, it may destroy elements via the wiring inside the LSI.

[0005] The present disclosure provides a thermal printhead that can protect elements.

[0006] According to one aspect of this embodiment, there is provided a thermal printhead comprising a heating resistor, a drive circuit that controls current flow to the heating resistor, input signal wiring and power supply wiring connected to the drive circuit, an input signal electrode electrically connected to the drive circuit via the input signal wiring, an output signal electrode electrically connected to the drive circuit, a power supply electrode electrically connected to the drive circuit via the power supply wiring, a ground electrode electrically connected to the drive circuit, and a shield wiring electrically connected to the output signal electrode or the ground electrode, wherein the shield wiring is disposed at a distance from the power supply wiring or the input signal wiring so as to be able to conduct current caused by electrostatic discharge applied to the power supply electrode or the input signal electrode. [Effects of the Invention]

[0007] According to this embodiment, it is possible to provide a thermal printhead that can protect the elements. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a thermal printhead according to the first embodiment. [Figure 2] FIG. 2 is an equivalent circuit diagram showing the entire thermal printhead according to the first embodiment. [Figure 3] FIG. 3 is an enlarged view of the driving IC and its periphery shown in FIG. [Figure 4] FIG. 4 is an equivalent circuit diagram showing the entire thermal printhead according to the second embodiment. [Figure 5] FIG. 5 is an enlarged view of the driving IC and its periphery shown in FIG. [Figure 6] FIG. 6 is an equivalent circuit diagram showing the entire thermal printhead according to the third embodiment. [Figure 7] FIG. 7 is an enlarged view of the driving IC and its periphery shown in FIG. [Figure 8] FIG. 8 is an equivalent circuit diagram of the entire thermal printhead according to the fourth embodiment. [Figure 9] FIG. 9 is an enlarged view of the driving IC and its periphery shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Next, this embodiment will be described with reference to the drawings. In the drawings described below, identical or similar parts are designated by identical or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and planar dimensions of each component may differ from the actual relationship. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. Furthermore, it goes without saying that the drawings may include parts with different dimensional relationships and ratios.

[0010] Furthermore, the embodiments described below are merely examples of devices and methods for embodying the technical ideas, and do not specify the materials, shapes, structures, arrangements, etc. of the components. Various modifications can be made to the present embodiments within the scope of the claims.

[0011] [First embodiment] FIG. 1 is a schematic diagram showing an example of the configuration of a thermal printhead 10 according to the first embodiment.

[0012] 1, a thermal printhead 10 according to the first embodiment includes an insulating substrate 1, a first common wiring 2 formed on the insulating substrate 1, a heating resistor 3, a drive circuit 4, and a connector 5. The heating resistor 3 is electrically connected to the first common wiring 2. The drive circuit 4 is electrically connected to the first common wiring 2 and controls the current flowing through the heating resistor 3. The connector 5 is electrically connected to the drive circuit 4 via each external terminal and each electrode of the thermal printhead 10. In the following description, the current caused by ESD is also referred to as the ESD current.

[0013] The connector 5 has a first common VH1 electrode, a power supply VDD electrode, a first strobe signal STB1 electrode, a second strobe signal STB2 electrode, a data latch signal LAT electrode, a second common VH2 electrode, a serial data input signal DI electrode, a clock input signal CLK electrode, a phase signal M electrode, a first ground GND_IC electrode, and a second ground GND electrode. Here, the first ground GND_IC electrode is a ground electrode (local ground electrode) for the drive circuit 4. The second ground GND electrode is a general-purpose ground electrode (global ground electrode). Note that the second ground GND electrode may be electrically connected to the drive circuit 4.

[0014] 2 is an equivalent circuit diagram of the entire thermal printhead 10 according to the first embodiment. FIG. 3 is an enlarged view of the driving IC 4 and its periphery shown in FIG.

[0015] The internal structure and wiring of the substrate of the thermal printhead 10 according to the first embodiment will be described with reference to FIGS. 2 and 3. FIG.

[0016] As shown in Figures 2 and 3, the thermal printhead 10 includes resistors R1 to R128, which are an example of the heating resistor 3; a drive circuit 4 that controls the current flow through the resistors R1 to R128; input signal wiring (13 to 15, 17 to 19) and power supply wiring (11A, 11B) connected to the drive circuit 4; input signal electrodes (STB1, STB2, LAT, DI, CLK, M) electrically connected to the drive circuit 4 via the input signal wiring (13 to 15, 17 to 19); a first common VH1 electrode, which is an example of an output signal electrode electrically connected to the drive circuit 4; a power supply VDD electrode, which is electrically connected to the drive circuit 4 via the power supply wiring (11A, 11B); a first ground GND_IC electrode, which is an example of a ground electrode electrically connected to the drive circuit 4; and shield wiring (20A, 20B) electrically connected to the first common VH1 electrode. 2 and 3, the first common VH1 electrode may be electrically connected to a first common wiring 2, which is an example of an output signal wiring. The second common VH2 electrode, which is an example of an output signal electrode, may be electrically connected via a second common wiring 16, which is an example of an output signal wiring. The first ground GND_IC electrode may be electrically connected via a ground wiring 12. In the following description, the resistors R1 to R128 are collectively referred to as a heating resistor 3. The drive circuit 4 is also referred to as a drive IC (drive integrated circuit) 4. Here, as an example, the resistors R1 to R128, which are the heating resistor 3, have been described as being 128 in number, but the number of resistors is not limited to a plurality such as 128, and may be, for example, one.

[0017] 2 and 3, one end of each of the resistors R1 to R128 is electrically connected to the first common VH1 electrode of the thermal printhead 10 via the first common wiring 2. The other end of each of the resistors R1 to R128 is electrically connected to each of the driver output terminals DO1 to DO128 of the driving IC 4.

[0018] The power supply VDD terminal of the driving IC 4 is electrically connected via power supply wiring (11A, 11B) to the power supply VDD electrode of the thermal printhead 10. Note that either one of the power supply wirings (11A, 11B) may be disposed.

[0019] The first ground GND_IC terminal of the driver IC 4 is electrically connected to the first ground GND_IC electrode of the thermal printhead 10 via a ground wiring 12 .

[0020] The first strobe signal STB1 terminal of the driving IC 4 is electrically connected to the first strobe signal STB1 electrode of the thermal printhead 10 via the input signal wiring 13. The first strobe signal STB1 is a signal that controls the time for which the resistors R1 to R64 are heated, for example.

[0021] The second strobe signal STB2 terminal of the driver IC 4 is electrically connected to the second strobe signal STB2 electrode of the thermal printhead 10 via the input signal wiring 14. The second strobe signal STB2 is a signal that controls the time for which the resistors R65 to R128 are heated, for example.

[0022] The data latch signal LAT terminal of the driver IC 4 is electrically connected to the data latch signal LAT electrode of the thermal printhead 10 via the input signal wiring 15. The data latch signal LAT is, for example, an input signal that controls data reading from a shift register or holding of the immediately preceding data.

[0023] The second common electrode terminals VH2_A to VH2_H of the driving IC 4 are electrically connected to the second common electrode VH2 of the thermal printhead 10 via a second common wiring 16, which is an example of an output signal wiring. In order to minimize the influence of wiring resistance inside the driving IC 4, the second common electrode terminals VH2_A to VH2_H of the driving IC 4 may be arranged in plurality facing each of the driver output terminals DO1 to DO128.

[0024] The serial data input signal DI terminal of the driving IC 4 is electrically connected to the serial data input signal DI electrode of the thermal printhead 10 via the input signal wiring 17. The serial data input signal is a serial data signal of the shift register that is input to the driving IC 4.

[0025] The clock input signal CLK terminal of the driver IC 4 is electrically connected to the clock input signal CLK electrode of the thermal printhead 10 via the input signal wiring 18 .

[0026] The phase signal M terminal of the driver IC 4 is electrically connected to the phase signal M electrode of the thermal printhead 10 via the input signal wiring 19. The phase signal M is a signal that indicates the phase of the voltage between the first common VH1 electrode and the second common VH2 electrode.

[0027] The input signal electrodes (STB1, STB2, LAT, DI, CLK, M) include a first strobe signal STB1 electrode, a second strobe signal STB2 electrode, a data latch signal LAT electrode, a serial data input signal DI electrode, a clock input signal CLK electrode, and a phase signal M electrode.

[0028] One of the shielding wirings (20A, 20B) is electrically connected to the first common VH1 electrode via the first common wiring 2, which is an example of an output signal wiring. The other of the shielding wirings (20A, 20B) is left unconnected. That is, the other of the shielding wirings (20A, 20B) is a wiring for inducing ESD current, and since the ESD current flows to one of the first common VH1 electrodes, no element is connected to its end. That is, the shielding wirings (20A, 20B) conduct the ESD current (30A, 30B) from the power supply VDD electrode or each signal input electrode (STB1, STB2, LAT, DI, CLK, M) of the connector 5 via the power supply wirings (11A, 11B) or the input signal wirings (13-15, 17-19), thereby preventing damage to other elements.

[0029] 3, the shield wiring (20A, 20B) is arranged at a distance from the power supply wiring (11A, 11B) so as to be able to conduct the ESD current applied to the power supply VDD electrode. Note that the shield wiring (20A, 20B) may also be arranged at a distance from the input signal wiring (13-15, 17-19) so as to be able to conduct the ESD current applied to each signal input electrode (STB1, STB2, LAT, DI, CLK, M).

[0030] In this specification, "electrically connected" includes a connection via "something that has some kind of electrical action." Here, "something that has some kind of electrical action" is not particularly limited as long as it allows electrical signals to be transmitted and received between the connected objects. For example, "something that has some kind of electrical action" includes electrodes, wiring, switching elements, resistive elements, inductors, capacitive elements, and other elements with various functions.

[0031] (ESD current path) As shown in FIG. 3, around the driving IC 4, the wirings of the driver output terminals DO1 to DO128 of the driving IC 4, the second common electrode terminals VH2_A to VH2_H, the first ground electrode terminal GND_IC, and the power supply terminal VDD are densely arranged.

[0032] In addition, around the driving IC 4, the wiring for the first strobe signal STB1 terminal, the second strobe signal STB2 terminal, the data latch signal LAT terminal, the serial data input signal DI terminal, the clock signal CLK terminal, and the phase signal M terminal of the driving IC 4 are densely arranged.

[0033] Generally, the wiring around each resistor in the thermal printhead 10 is covered with a glass overcoat layer, preventing external ESD current from reaching the wiring. However, no glass layer is provided around or directly below the driver IC 4. Furthermore, no glass layer is provided on the connector 5 of the thermal printhead 10. Therefore, ESD current applied from unprotected electrodes is likely to flow through the wiring around the driver IC 4 inside the thermal printhead 10.

[0034] Specifically, as shown in Figure 3, for example, when an ESD current (30A, 30B) flows through the power supply VDD electrodes of the thermal printhead 10, the ESD current (30A, 30B) flows from the power supply VDD electrodes to the first common VH1 electrode via the power supply wiring (11A, 11B), the shield wiring (20A, 20B), and the first common wiring 2. The terminal arrangement of the driving IC is not limited, and the power supply VDD terminal and each signal input electrode may be arranged differently. Furthermore, even when an ESD current flows through each signal input electrode, the shield wiring may be arranged in a position where the ESD current can easily flow from each signal input electrode.

[0035] As described above, according to the first embodiment, even if an ESD current is conducted to the electrodes of the connector, the elements can be protected by the shield wiring.

[0036] [Second embodiment] A thermal printhead 10A according to a second embodiment will be described with reference to the drawings. Fig. 4 is an equivalent circuit diagram showing the entire thermal printhead 10A according to the second embodiment. Fig. 5 is an enlarged view of the periphery of the driving IC 4 shown in Fig. 4.

[0037] 4 and 5, the thermal printhead 10A according to the second embodiment has a different connection destination for the shield wiring (21A, 21B). In the thermal printhead 10 according to the first embodiment, the shield wiring (20A, 20B) is electrically connected to a first common VH1 electrode, whereas in the thermal printhead 10A according to the second embodiment, the shield wiring (21A, 21B) is electrically connected to a first ground GND_IC electrode, which is an example of a ground electrode.

[0038] In the second embodiment, the points common to the first embodiment (e.g., the first common wiring 2, the heating resistor 3, the driving IC 4, the power supply VDD electrode, the first ground GND_IC electrode, each input signal electrode, the first common VH1 electrode, and the second common VH2 electrode) are referred to in the first embodiment, and the following describes the points of difference.

[0039] As shown in Figures 4 and 5, one side of the shield wiring (21A, 21B) is electrically connected to the first ground GND_IC electrode. The other side of the shield wiring (21A, 21B) is left unconnected. That is, the other side of the shield wiring (21A, 21B) is a wiring for inducing ESD current, and since the ESD current flows to the first ground GND_IC electrode, no element is connected to its end. That is, the shield wiring (21A, 21B) conducts the ESD current (31A, 31B) from the power supply VDD electrode or each signal input electrode (STB1, STB2, LAT, DI, CLK, M) of the connector 5 via the power supply wiring (11A, 11B) or the input signal wiring (13-15, 17-19), thereby preventing damage to other elements.

[0040] (ESD current path) Specifically, as shown in Figure 5, if an ESD current (31A, 31B) is conducted to the power supply VDD electrodes of the thermal printhead 10A, the ESD current (31A, 31B) flows from the power supply VDD electrodes to the power supply wiring (11A, 11B), the shield wiring (21A, 21B), and the first ground GND_IC electrode. The terminal layout of the driver IC 4 is not limited to this, and the layout of the power supply VDD terminal and each signal input electrode may be different. Furthermore, even if an ESD current flows to each signal input electrode, the shield wiring may be located in a position where the ESD current can easily flow from each signal input electrode.

[0041] As described above, according to the second embodiment, even if an ESD current is applied to the electrodes of the connector, the elements can be protected by the shield wiring.

[0042] [Third embodiment] A thermal printhead 10B according to a third embodiment will be described with reference to the drawings. Fig. 6 is an equivalent circuit diagram showing the entire thermal printhead 10B according to the third embodiment. Fig. 7 is an enlarged view of the periphery of the driving IC 4 shown in Fig. 6.

[0043] 6 and 7, the thermal printhead 10B according to the third embodiment has a different connection destination for the shield wiring (22A, 22B). In the thermal printhead 10A according to the second embodiment, the shield wiring (21A, 21B) is electrically connected to the first ground GND_IC electrode, whereas in the thermal printhead 10B according to the third embodiment, the shield wiring (22A, 22B) is electrically connected to a second common VH2 electrode, which is an example of an output signal electrode.

[0044] In the third embodiment, the points common to the second embodiment (e.g., the first common wiring 2, the heating resistor 3, the driving IC 4, the power supply VDD electrode, the first ground GND_IC electrode, each input signal electrode, the first common VH1 electrode, and the second common VH2 electrode) are referred to in the second embodiment, and the differences will be explained below.

[0045] As shown in FIGS. 6 and 7, one of the shield wirings (22A, 22B) is electrically connected to the second common VH2 electrode. The other of the shield wirings (22A, 22B) is left unconnected. That is, the other of the shield wirings (22A, 22B) is a wiring for inducing ESD current, and since the ESD current flows to one of the second common VH2 electrodes, no element is connected to its end. That is, the shield wirings (22A, 22B) conduct the ESD current (32A, 32B) that flows from the power supply VDD electrode or each signal input electrode (STB1, STB2, LAT, DI, CLK, M) of the connector 5 via the power supply wirings (11A, 11B) or input signal wirings (13-15, 17-19), thereby preventing damage to other elements.

[0046] (ESD current path) Specifically, as shown in Figure 7, if an ESD current (32A, 32B) flows through the power supply VDD electrodes of the thermal printhead 10B, the ESD current (32A, 32B) will be conducted from the power supply VDD electrodes to the power supply wiring (11A, 11B), the shield wiring (22A, 22B), and the second common VH2 electrode. The terminal layout of the driver IC 4 is not limited to this, and the power supply VDD terminal and each signal input electrode may be arranged differently. Furthermore, even if an ESD current flows through each signal input electrode, the shield wiring may be arranged in a position that makes it easier for the ESD current to be conducted from each signal input electrode.

[0047] As described above, according to the third embodiment, even if an ESD current is applied to the electrodes of the connector, the elements can be protected by the shield wiring.

[0048] [Fourth embodiment] A thermal printhead 10C according to a fourth embodiment will be described with reference to the drawings. Fig. 8 is an equivalent circuit diagram showing the entire thermal printhead 10C according to the fourth embodiment. Fig. 9 is an enlarged view of the periphery of the driving IC 4 shown in Fig. 8.

[0049] 8 and 9, the thermal printhead 10C according to the fourth embodiment has a different connection destination for the shield wiring (23A, 23B). In the thermal printhead 10B according to the third embodiment, the shield wiring (22A, 22B) is electrically connected to a second common VH2 electrode, whereas in the thermal printhead 10C according to the fourth embodiment, the shield wiring (23A, 23B) is electrically connected to a second ground GND electrode, which is an example of a ground electrode.

[0050] In the fourth embodiment, the points common to the third embodiment (e.g., the first common wiring 2, the heating resistor 3, the driving IC 4, the power supply VDD electrode, the first ground GND_IC electrode, each input signal electrode, the first common VH1 electrode, and the second common VH2 electrode) are referred to in the third embodiment, and the differences will be explained below.

[0051] As shown in FIGS. 8 and 9, one side of the shield wiring (23A, 23B) is electrically connected to a second ground GND electrode, which is an example of a ground electrode. The other side of the shield wiring (23A, 23B) is left unconnected. That is, the other side of the shield wiring (23A, 23B) is a wiring for inducing ESD current, and since the ESD current flows to the second ground GND electrode on one side, no element is connected to its end. That is, the shield wiring (23A, 23B) conducts the ESD current (33A, 33B) from the power supply VDD electrode or each signal input electrode (STB1, STB2, LAT, DI, CLK, M) of the connector 5 via the power supply wiring (11A, 11B) or the input signal wiring (13-15, 17-19), thereby preventing damage to other elements.

[0052] (ESD current path) Specifically, as shown in Figure 9, if an ESD current (33A, 33B) flows through the power supply VDD electrodes of the thermal printhead 10C, the ESD current (33A, 33B) will flow from the power supply VDD electrodes to the power supply wiring (11A, 11B), the shield wiring (23A, 23B), and the second ground GND electrode. The terminal layout of the driver IC 4 is not limited to this, and the power supply VDD terminal and each signal input electrode may be arranged differently. Furthermore, even if an ESD current flows through each signal input electrode, the shield wiring may be arranged in a position where the ESD current can easily flow from each signal input electrode.

[0053] As described above, according to the fourth embodiment, even if an ESD current is applied to the electrodes of the connector, the elements can be protected by the shield wiring.

[0054] (Other embodiments) As described above, one embodiment has been described, but the descriptions and drawings that form part of the disclosure are illustrative and should not be understood as limiting. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure. Thus, the present embodiment includes various embodiments not described herein. [Explanation of symbols]

[0055] 2 First common wiring 3 Heating resistor 4. Drive circuit 10 Thermal printhead 11A, 11B power wiring 12 Ground wiring 13, 14, 15, 17, 18, 19 Input signal wiring 16 Second common wiring 20A, 20B, 21A, 21B, 22A, 22B, 23A, 23B Shielded wiring 30A, 30B, 31A, 31B, 32A, 32B, 33A, 33B ESD current R1~R128 resistors STB1 First strobe signal STB2 Second strobe signal LAT Data latch signal DI Serial data input signal CLK Clock input signal M phase signal

Claims

1. A heating resistor; a drive circuit for controlling the energization of the heating resistor; an input signal wiring and a power supply wiring connected to the drive circuit; an input signal electrode electrically connected to the drive circuit via the input signal wiring; an output signal electrode electrically connected to the drive circuit; a power supply electrode electrically connected to the drive circuit via the power supply wiring; a ground electrode electrically connected to the drive circuit; a shield wiring electrically connected to the output signal electrode or the ground electrode; Equipped with The shield wiring is a thermal printhead arranged at a distance from the power supply wiring or the input signal wiring so as to be able to conduct a current caused by electrostatic discharge applied to the power supply electrode or the input signal electrode;

2. The input signal electrode is 2. The thermal printhead of claim 1, comprising a first strobe signal electrode, a second strobe signal electrode, a data latch signal electrode, a serial data input signal electrode, a clock input signal electrode, and a phase signal electrode.

3. The output signal electrode is 3. The thermal printhead according to claim 1, wherein the first common electrode is a first common electrode.

4. The output signal electrode is 3. The thermal printhead according to claim 1, wherein the second common electrode is a second common electrode.

5. The ground electrode is 3. The thermal printhead according to claim 1, wherein the first electrode is a ground electrode.

6. The ground electrode is 3. The thermal printhead according to claim 1, wherein the second electrode is a ground electrode.

7. The shield wiring is 7. The thermal printhead according to claim 1, wherein one end electrically connected to said output signal electrode or said ground electrode and the other end opposite to said one end are unconnected.

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