Thermal print head

Abstract

To provide a thermal print head that is lower in cost, has improved wear resistance to a print medium, and is capable of preventing the sticking of the print medium.SOLUTION: A thermal print head 1 includes a heat generating resistor 40, a wiring layer 15 that is connected to the heat generating resistor 40, and a protective layer 45 that covers the heat generating resistor 40 and the wiring layer 15. The protective layer 45 is an insulating layer to which diamond particles are added.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to thermal printheads. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2000-153630 (Patent Document 1) discloses a thermal printhead including a ceramic substrate, a glaze layer, a common electrode, a plurality of individual electrodes, a heating resistor, and a protective layer. The protective layer covers the common electrode, the plurality of individual electrodes, and the heating resistor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-153630 A [Summary]

[0004] An object of the present disclosure is to provide a thermal printhead that is lower in cost, has improved resistance to wear on the print medium, and can prevent the print medium from sticking.

[0005] The thermal printhead of the present disclosure includes a heating resistor, a wiring layer connected to the heating resistor, and a protective layer that covers the heating resistor and the wiring layer. The protective layer is an insulating layer to which diamond particles are added. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic partially enlarged plan view of a thermal printhead according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic enlarged partial cross-sectional view of the thermal printhead according to the embodiment taken along the cross-sectional line II-II shown in FIG. [Diagram 3] FIG. 3 is a schematic enlarged partial cross-sectional view of the thermal printhead according to the embodiment taken along the cross-sectional line III-III shown in FIG. [Figure 4]4 is a flowchart showing a method for manufacturing a thermal printhead according to an embodiment.

[0007] The details of the embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference numerals, and the description thereof will not be repeated. At least some of the configurations of the embodiments described below may be arbitrarily combined.

[0008] A thermal printhead 1 according to an embodiment of the present disclosure will be described with reference to Figures 1 to 3. The thermal printhead 1 includes a substrate 10, a glaze layer 12, a wiring layer 15, a heating resistor 40, and a protective layer 45.

[0009] The substrate 10 has a main surface 11. The longitudinal direction of the substrate 10 in a plan view of the main surface 11 is the X direction. The X direction is the main scanning direction. The lateral direction of the substrate 10 in a plan view of the main surface 11 is the Y direction. The Y direction is the sub-scanning direction. The thickness direction of the substrate 10, which is perpendicular to the X and Y directions, is the Z direction. The main surface 11 is an end face of the substrate 10 in the thickness direction (Z direction). The substrate 10 is made of an insulating material such as alumina (Al2O3). The substrate 10 is made of, for example, ceramic.

[0010] The glaze layer 12 is disposed on the main surface 11 of the substrate 10. The glaze layer 12 can accumulate heat generated from the heating resistor 40. The glaze layer 12 is formed of an insulating material such as glass.

[0011] The wiring layer 15 is disposed on the glaze layer 12. The wiring layer 15 is formed of a conductive material such as silver (Ag) or gold (Au). The wiring layer 15 includes a common electrode 20 and a plurality of individual electrodes 30. The common electrode 20 and the plurality of individual electrodes 30 are connected to a heating resistor 40.

[0012] Specifically, the common electrode 20 includes a connecting portion 21 and a plurality of strip portions 22. The connecting portion 21 extends along the X direction, and the longitudinal direction of the connecting portion 21 is the X direction. The connecting portion 21 is spaced apart from the heating resistor 40 in the Y direction. Each of the plurality of strip portions 22 extends from a side of the connecting portion 21 facing the heating resistor 40 toward the heating resistor 40. The longitudinal direction of each of the plurality of strip portions 22 is, for example, the Y direction. The plurality of strip portions 22 are arranged at intervals along the X direction.

[0013] Each of the strip-shaped portions 22 includes an extension portion 23 and a base portion 24. The base portion 24 is spaced apart from the heating resistor 40 in the Y direction. The base portion 24 is connected to the extension portion 23 and the connecting portion 21. The extension portion 23 extends from an end portion of the base portion 24 that is proximal to the heating resistor 40 toward the heating resistor 40. The longitudinal direction of the extension portion 23 is, for example, the Y direction. The extension portion 23 is in contact with the heating resistor 40.

[0014] The width of the extension portion 23 is smaller than the width of the base portion 24. In the present embodiment, the width of the extension portion 23 means the length of the extension portion 23 in the short direction (X direction) of the extension portion 23 in a plan view of the main surface 11 of the substrate 10. The width of the base portion 24 means the length of the base portion 24 in the longitudinal direction (X direction) of the heating resistor 40 in a plan view of the main surface 11 of the substrate 10. The width of the base portion 24 is the width of an end portion of the base portion 24 that is proximal to the extension portion 23.

[0015] The individual electrodes 30 are arranged at intervals along the X direction. Each of the individual electrodes 30 includes a base portion 32, an extension portion 31, and a pad 33.

[0016] The base 32 is spaced apart from the heating resistor 40 in the Y direction. The base 32 is connected to the extension 31 and the pad 33. The extension 31 extends from an end of the base 32 proximal to the heating resistor 40 toward the heating resistor 40. The longitudinal direction of the extension 31 is, for example, the Y direction. The extension 31 is disposed between two adjacent extensions 23. That is, the extensions 23 and the extensions 31 are arranged alternately in the X direction. The extension 31 is in contact with the heating resistor 40.

[0017] The width of the extension portion 31 is smaller than the width of the base portion 32. In this embodiment, the width of the extension portion 31 means the length of the extension portion 31 in the short direction (X direction) of the extension portion 31 in a plan view of the main surface 11 of the substrate 10. The width of the base portion 32 means the length of the base portion 32 in the longitudinal direction (X direction) of the heating resistor 40 in a plan view of the main surface 11 of the substrate 10. The width of the base portion 32 is the width of an end portion of the base portion 32 proximal to the extension portion 31.

[0018] A conductive wire (not shown) is bonded to the pad 33, which is connected to a terminal of a driver IC (not shown).

[0019] In a plan view of the main surface 11 of the substrate 10, the heating resistor 40 is disposed between the connecting portion 21 of the common electrode 20 and the base portions 32 of the individual electrodes 30. The heating resistor 40 extends along the X direction, and the longitudinal direction of the heating resistor 40 is the X direction. The heating resistor 40 is disposed on the extension portions 23, 31 and the glaze layer 12. In a plan view of the main surface 11 of the substrate 10, the heating resistor 40 overlaps the extension portions 23, 31. The heating resistor 40 is formed of a material (e.g., ruthenium oxide) having a higher resistivity than the material constituting the wiring layer 15.

[0020] The heating resistor 40 includes a plurality of heating portions 41. In a plan view of the main surface 11 of the substrate 10, each of the plurality of heating portions 41 is a portion of the heating resistor 40 sandwiched between the extension portion 23 of the common electrode 20 and the extension portion 31 of the individual electrode 30.

[0021] A common potential (e.g., ground potential) is applied to the common electrode 20. A potential is applied to each of the individual electrodes 30 from a driver IC (not shown). This causes a current to flow through a heat generating portion 41 located between the extension portion 31 of the individual electrode 30 to which the potential is applied and the extension portion 23 of the common electrode 20 adjacent thereto, causing the heat generating portion 41 to generate heat. The heat from the heat generating portion 41 is transferred to a print medium such as thermal paper, and printing is performed on the print medium.

[0022] The protective layer 45 covers the wiring layer 15, the heating resistor 40, and the glaze layer 12. The protective layer 45 protects the heating resistor 40 and the like from wear, corrosion, oxidation, and the like. The protective layer 45 is an insulating layer to which diamond particles are added. For example, the protective layer 45 is a glass layer to which diamond particles are added. The diamond particles are, for example, industrial diamond powder. The thickness of the protective layer 45 is, for example, 1 μm or more and 10 μm or less.

[0023] The median diameter (D50) of the diamond particles is 0.5 times or less than the thickness of the protective layer 45. The median diameter of the diamond particles may be 0.4 times or less than the thickness of the protective layer 45, may be 0.3 times or less than the thickness of the protective layer 45, or may be 0.2 times or less than the thickness of the protective layer 45. The median diameter is the median value of the particle size distribution obtained by the particle size analysis shown in Japanese Industrial Standards (JIS) 8825:2022. The median diameter (D50) of the diamond particles is, for example, 0.1 μm or more. The median diameter (D50) of the diamond particles may be 0.3 μm or more. The median diameter (D50) of the diamond particles is, for example, 1.5 μm or less. The median diameter (D50) of the diamond particles may be 1.2 μm or less.

[0024] The ratio of diamond particles in the protective layer 45 is, for example, 1 volume % or more and 90 volume % or less. The protective layer 45 has an opening (not shown) and the pad 33 is exposed from the opening of the protective layer 45.

[0025] An example of a method for manufacturing the thermal printhead 1 of the present embodiment will be described with reference to FIG.

[0026] A glaze layer 12 is formed on a main surface 11 of a substrate 10 (S1). Specifically, a paste containing glass is applied onto the main surface 11 of the substrate 10 by screen printing or the like. The paste is dried and fired to form the glaze layer 12.

[0027] The wiring layer 15 is formed on the glaze layer 12 (S2). The wiring layer 15 includes a common electrode 20 and a plurality of individual electrodes 30.

[0028] Specifically, a metal layer (not shown) is formed on the glaze layer 12. For example, a paste containing a material for forming the metal layer, such as a resinate paste containing silver particles, is applied onto the glaze layer 12 by screen printing or the like. The paste is fired. Thus, the metal layer is formed. Then, the metal layer is patterned by a lithography process to form the wiring layer 15. For example, a resist pattern is formed on the metal layer. The resist pattern is formed by applying a photosensitive resin material onto the metal layer and exposing and developing the applied photosensitive resin material. The resist pattern has openings. The metal layer is exposed from the openings of the resist pattern. The resist pattern is used as a mask to etch the parts of the metal layer that are exposed from the resist pattern. Thus, the metal layer is patterned to become the wiring layer 15.

[0029] The heating resistor 40 is formed (S3). For example, a paste containing materials (e.g., glass and ruthenium oxide particles) constituting the heating resistor 40 is applied onto the extensions 23, 31 and the glaze layer 12. The paste is fired. In this manner, the heating resistor 40 is formed.

[0030] A protective layer 45 is formed (S4). For example, a paste containing glass, diamond particles, and a resin binder is applied onto the wiring layer 15, the heating resistor 40, and the glaze layer 12 by screen printing or using a dispenser. The paste is dried. The paste is pre-fired to remove the resin binder. The pre-fire temperature is about 450°C. The pre-fire time is about 30 minutes. The paste from which the resin binder has been removed is then fired. The pre-fire temperature is, for example, 800°C or higher and 880°C or lower. The pre-fire time is, for example, 3 minutes or higher and 15 minutes or lower. Since the firing time is short, even if the firing atmosphere is air, the weight loss of the diamond particles due to the combustion of the diamond particles during firing can be reduced. By setting the firing atmosphere to a nitrogen atmosphere, the combustion of the diamond particles during firing can be prevented, and the weight loss of the diamond particles can be further reduced. In this way, the protective layer 45 is formed.

[0031] The laminate including the substrate 10, the glaze layer 12, the wiring layer 15, the heating resistor 40, and the protective layer 45 is singulated. For example, the laminate is cut by irradiating the laminate with a laser beam. The laminate is singulated into a plurality of thermal printheads 1. In this manner, the thermal printheads 1 are obtained.

[0032] In another modification of this embodiment, the extensions 23 and 31 may extend in a direction oblique to the longitudinal direction of the heating resistor 40.

[0033] The effects of the thermal printhead 1 of this embodiment will be described.

[0034] The thermal printhead 1 of this embodiment includes a heating resistor 40, a wiring layer 15 connected to the heating resistor 40, and a protective layer 45 that covers the heating resistor 40 and the wiring layer 15. The protective layer 45 is an insulating layer to which diamond particles are added.

[0035] Since the protective layer 45 contains diamond particles, the hardness of the protective layer 45 is improved. The abrasion resistance of the protective layer 45 against a print medium such as thermal paper is improved. In addition, since the protective layer 45 contains diamond particles, the contact of the print medium with the protective layer 45 becomes smoother, and the print medium can be prevented from sticking to the protective layer 45.

[0036] In the comparative example in which the entire protective layer is made of diamond-like carbon (DLC), the material cost of the protective layer is high. In addition, the protective layer made of diamond-like carbon (DLC) needs to be formed using a more expensive manufacturing method such as a chemical vapor deposition (CVD) method. In contrast, in this embodiment, the protective layer 45 is an insulating layer to which diamond particles are added. Since only a part of the protective layer 45 is made of diamond particles, the material cost of the protective layer 45 is reduced. In addition, the protective layer 45 can be formed using a less expensive manufacturing method such as screen printing or application using a dispenser. Therefore, the cost of the thermal printhead 1 of this embodiment is lower.

[0037] During operation of the thermal printhead 1, the temperature of the portion of the protective layer 45 located on the heating resistor 40 typically reaches approximately 300° C., and may temporarily reach approximately 700° C. However, the diamond particles do not decompose even at such high temperatures and can withstand such high temperatures.

[0038] In the thermal printhead 1 of this embodiment, the median diameter of the diamond particles is 0.5 times the thickness of the protective layer 45 or less.

[0039] This can prevent roughening of the surface of the protective layer 45. The contact of the print medium with the protective layer 45 becomes smoother, improving print quality.

[0040] In the thermal printhead 1 of the present embodiment, the proportion of diamond particles in the protective layer 45 is not less than 1% by volume and not more than 50% by volume.

[0041] Since the proportion of diamond particles in protective layer 45 is 1% by volume or more, the abrasion resistance of protective layer 45 against the print medium is improved, and the print medium can be more reliably prevented from sticking to protective layer 45. Since the proportion of diamond particles in protective layer 45 is 1% by volume or more and 90% by volume or less, surface roughening of protective layer 45 can be prevented. Contact of the print medium with protective layer 45 becomes smoother, improving print quality.

[0042] In the thermal printhead 1 of this embodiment, the diamond particles are industrial diamond powder.

[0043] Therefore, the cost of the protective layer 45 is significantly reduced compared to when the protective layer 45 is made of diamond-like carbon (DLC), for example. An increase in the cost of the thermal printhead 1 can be suppressed.

[0044] Various aspects of the present disclosure are summarized below as appendices. (Appendix 1) A heating resistor; A wiring layer connected to the heating resistor; a protective layer covering the heating resistor and the wiring layer, A thermal printhead, wherein the protective layer is an insulating layer doped with diamond particles. (Appendix 2) 2. The thermal printhead of claim 1, wherein the median diameter of the diamond particles is less than or equal to 0.5 times the thickness of the protective layer. (Appendix 3) 3. The thermal printhead of claim 1, wherein the proportion of the diamond particles in the protective layer is 1% by volume or more and 90% by volume or less. (Appendix 4) 4. A thermal printhead as described in any one of claims 1 to 3, wherein the diamond particles are industrial diamond powder.

[0045] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0046] 1 thermal print head, 10 substrate, 11 main surface, 12 glaze layer, 15 wiring layer, 20 common electrode, 21 connecting portion, 22 strip portion, 23, 31 extension portion, 24, 32 base portion, 30 individual electrode, 33 pad, 40 heating resistor, 41 heating portion, 45 protective layer.

Claims

1. A heating resistor; A wiring layer connected to the heating resistor; a protective layer covering the heating resistor and the wiring layer, A thermal printhead, wherein the protective layer is an insulating layer doped with diamond particles.

2. 2. The thermal printhead according to claim 1, wherein the median diameter of the diamond particles is equal to or less than 0.5 times the thickness of the protective layer.

3. The thermal printhead according to claim 1 , wherein the ratio of the diamond particles in the protective layer is 1% by volume or more and 90% by volume or less.

4. A thermal printhead according to claim 1 , wherein the diamond particles are industrial diamond powder.

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