Thermal printing head

Abstract

The invention provides a thermal print head. The thermal printing head comprises a heating resistor body; a wiring layer connected to the heating resistor; and a protective layer covering the heating resistor and the wiring layer. And the protective layer is an insulating layer added with diamond particles. According to the present invention, it is possible to provide a thermal print head which is lower in cost, can improve wear resistance with respect to a print medium, and can prevent adhesion of the print medium.

Description

Technical Field

[0001] The invention relates to a thermal print head. Background Art

[0002] Japanese Patent Application Laid-Open No. 2000-153630 discloses a thermal print head including a ceramic substrate, a glaze layer, a common electrode, a plurality of independent electrodes, a heating resistor, and a protective layer. The protective layer covers the common electrode, the plurality of independent electrodes, and the heating resistor. Summary of the invention

[0003] An object of the present invention is to provide a thermal print head which is low-cost, has improved abrasion resistance to print media, and can prevent print media from sticking.

[0004] The thermal print head of the present invention comprises: a heating resistor; a wiring layer connected to the heating resistor; and a protective layer covering the heating resistor and the wiring layer. The protective layer is an insulating layer to which diamond particles are added.

[0005] The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when read with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a schematic partially enlarged plan view of the thermal print head according to the embodiment.

[0007] Figure 2 A thermal print head according to an embodiment of the present invention Figure 1 A schematic partial enlarged cross-sectional view taken along the section line II-II is shown.

[0008] Figure 3 A thermal print head according to an embodiment of the present invention Figure 1 A schematic partial enlarged cross-sectional view along the section line III-III is shown.

[0009] Figure 4 This is a diagram showing a flow chart of a method for manufacturing a thermal print head according to an embodiment. DETAILED DESCRIPTION

[0010] The details of the embodiments of the present invention are described based on the drawings. In addition, the same reference numerals are used for the same or corresponding parts in the following drawings, and their description is not repeated. The structures of at least a part of the embodiments described below can also be combined arbitrarily.

[0011] Reference Figures 1 to 3 The thermal print head 1 according to the embodiment of the present invention is described below. The thermal print head 1 includes a substrate 10 , a glaze layer 12 , a wiring layer 15 , a heating resistor 40 , and a protective layer 45 .

[0012] The substrate 10 has a main surface 11. The long side direction of the substrate 10 when looking down on the main surface 11 is set to the X direction. The X direction is the main scanning direction. The short side direction of the substrate 10 when looking down on the main surface 11 is set to the Y direction. The Y direction is the sub-scanning direction. The thickness direction of the substrate 10 perpendicular to the X direction and the Y direction is set to the Z direction. The main surface 11 is an end surface in the thickness direction (Z direction) of the substrate 10. The substrate 10 is formed of an insulating material such as aluminum oxide (Al2O3). The substrate 10 is formed of ceramics, for example.

[0013] The glaze layer 12 is disposed on the main surface 11 of the substrate 10. The glaze layer 12 can store heat generated from the heating resistor 40. The glaze layer 12 is formed of an insulating material such as glass.

[0014] 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.

[0015] 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 length direction of the connecting portion 21 is the X direction. The connecting portion 21 is separated from the heating resistor 40 in the Y direction. The plurality of strip portions 22 extend toward the heating resistor 40 from the side of the connecting portion 21 opposite to the heating resistor 40. The length 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.

[0016] The plurality of strip-shaped portions 22 each include an extension portion 23 and a base portion 24. The base portion 24 is separated 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 close to the heating resistor 40 toward the heating resistor 40. The length direction of the extension portion 23 is, for example, the Y direction. The extension portion 23 is in contact with the heating resistor 40.

[0017] 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 refers to the length of the extension portion 23 in the short side direction (X direction) of the extension portion 23 when looking down at the main surface 11 of the substrate 10. The width of the base portion 24 refers to the length of the base portion 24 in the length direction (X direction) of the heating resistor 40 when looking down at the main surface 11 of the substrate 10. The width of the base portion 24 is the width of the end portion of the base portion 24 that is close to the extension portion 23.

[0018] The plurality of independent electrodes 30 are arranged at intervals along the X direction. The plurality of independent electrodes 30 include a base portion 32 , an extension portion 31 , and a pad 33 , respectively.

[0019] The base 32 is separated 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 the end of the base 32 close to the heating resistor 40 toward the heating resistor 40. The length direction of the extension 31 is, for example, the Y direction. The extension 31 is arranged between two adjacent extensions 23. That is, the extension 23 and the extension 31 are arranged alternately in the X direction. The extension 31 is in contact with the heating resistor 40.

[0020] The width of the extension portion 31 is smaller than the width of the base portion 32. In the present embodiment, the width of the extension portion 31 refers to the length of the extension portion 31 in the short side direction (X direction) of the extension portion 31 when looking down at the main surface 11 of the substrate 10. The width of the base portion 32 refers to the length of the base portion 32 in the longitudinal direction (X direction) of the heating resistor 40 when looking down at the main surface 11 of the substrate 10. The width of the base portion 32 is the width of the end portion of the base portion 32 close to the extension portion 31.

[0021] Conductive wires (not shown) connected to terminals of a driver IC (not shown) are bonded to the pads 33 .

[0022] When looking down at the main surface 11 of the substrate 10, the heating resistor 40 is arranged between the connecting portion 21 of the common electrode 20 and the base 32 of the plurality of independent electrodes 30. The heating resistor 40 extends along the X direction, and the long side direction of the heating resistor 40 is the X direction. The heating resistor 40 is arranged on the extension portions 23, 31 and the glaze layer 12. When looking down at the main surface 11 of the substrate 10, the heating resistor 40 overlaps with the extension portions 23, 31. The heating resistor 40 is formed of a material having a higher resistivity than the material constituting the wiring layer 15 (for example, ruthenium oxide).

[0023] The heating resistor 40 includes a plurality of heating portions 41 . The plurality of heating portions 41 are portions of the heating resistor 40 sandwiched between the extending portion 23 of the common electrode 20 and the extending portion 31 of the individual electrode 30 in a plan view of the main surface 11 of the substrate 10 .

[0024] A common potential (for example, a ground potential) is applied to the common electrode 20. A potential is applied to each of the plurality of independent electrodes 30 from a driver IC (not shown). As a result, a current flows through the heat generating portion 41 between the extension portion 31 of the independent electrode 30 to which the potential is applied and the extension portion 23 of the common electrode 20 located next thereto, and the heat generating portion 41 generates heat. The heat from the heat generating portion 41 is transferred to a printing medium such as thermal paper, and printing is performed on the printing medium.

[0025] 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 or oxidation. 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, not less than 1 μm and not more than 10 μm.

[0026] The median diameter of diamond particles (D 50 ) is 0.5 times or less of the thickness of the protective layer 45. The median particle size of the diamond particles may be 0.4 times or less of the thickness of the protective layer 45, 0.3 times or less of the thickness of the protective layer 45, or 0.2 times or less of the thickness of the protective layer 45. The median particle size is the central value of the particle size distribution obtained by the particle size analysis shown in Japanese Industrial Standard (JIS) 8825:2022. The median particle size (D 50 ) is, for example, 0.1 μm or more. The median diameter of the diamond particles (D 50 ) can be 0.3 μm or more. The median diameter of the diamond particles (D 50 ) is, for example, 1.5 μm or less. The median diameter of the diamond particles (D 50 ) can be less than 1.2 μm.

[0027] The ratio of the diamond particles in the protective layer 45 is, for example, 1 volume % or more and 90 volume % or less. The protective layer 45 is provided with an opening (not shown), and the pad 33 is exposed from the opening of the protective layer 45 .

[0028] Reference Figure 4 , an example of a method for manufacturing the thermal print head 1 of the present embodiment will be described.

[0029] The glaze layer 12 is formed on the main surface 11 of the substrate 10 (S1). Specifically, a paste containing glass is applied to the main surface 11 of the substrate 10 by screen printing or the like. The glaze layer 12 is formed by drying and firing the paste.

[0030] 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 .

[0031] Specifically, a metal layer (not shown) is formed on the glaze layer 12. The metal layer is applied to the glaze layer 12 by, for example, screen printing, a paste containing a material constituting the metal layer, such as a resin ester paste containing silver particles. The paste is fired. In this way, the metal layer is formed. Next, the metal layer is patterned by a photolithography 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 to the metal layer and exposing and developing the applied photosensitive resin material. The resist pattern has an opening. The metal layer is exposed from the opening of the resist pattern. Using the resist pattern as a mask, the portion of the metal layer exposed from the resist pattern is etched. In this way, the metal layer is patterned to become the wiring layer 15.

[0032] The heating resistor 40 is formed (S3). For example, a paste containing materials constituting the heating resistor 40 (eg, glass and ruthenium oxide particles) is applied to the extensions 23 and 31 and the glaze layer 12. The paste is fired. In this way, the heating resistor 40 is formed.

[0033] A protective layer 45 (S4) is formed. For example, a paste containing glass, diamond particles and a resin adhesive is applied to 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 adhesive. The pre-firing temperature is about 450°C. The pre-firing time is about 30 minutes. The paste from which the resin adhesive has been removed is formally fired. The formal firing temperature is, for example, above 800°C and below 880°C. The formal firing time is, for example, above 3 minutes and below 15 minutes. The formal firing time is short, so even if the formal firing atmosphere is air, the weight reduction of the diamond particles caused by the combustion of the diamond particles during the formal firing can be reduced. By setting the formal firing atmosphere to a nitrogen atmosphere, the combustion of the diamond particles during the formal firing can be prevented, thereby further reducing the weight reduction of the diamond particles. In this way, a protective layer 45 is formed.

[0034] The laminated body including the substrate 10, the glaze layer 12, the wiring layer 15, the heating resistor 40 and the protective layer 45 is singulated (S5). For example, the laminated body is irradiated with a laser to cut the laminated body. The laminated body is singulated into a plurality of thermal print heads 1. In this way, the thermal print head 1 is obtained.

[0035] In another modified example of the present embodiment, the extending portions 23 and 31 may extend in an oblique direction with respect to the longitudinal direction of the heating resistor 40 .

[0036] The effects of the thermal print head 1 of this embodiment will be described.

[0037] The thermal print head 1 of the present embodiment includes a heating resistor 40, a wiring layer 15 connected to the heating resistor 40, and a protective layer 45 covering the heating resistor 40 and the wiring layer 15. The protective layer 45 is an insulating layer to which diamond particles are added.

[0038] The protective layer 45 includes diamond particles, so the hardness of the protective layer 45 is improved. The wear resistance of the protective layer 45 to the printing medium such as thermal paper is improved. In addition, since the protective layer 45 includes diamond particles, the contact of the printing medium with respect to the protective layer 45 becomes smoother, and the printing medium can be prevented from adhering to the protective layer 45.

[0039] In the comparative example in which the protective layer is formed of diamond-like carbon (DLC) as a whole, the material cost of the protective layer is high. In addition, the protective layer formed of diamond-like carbon (DLC) needs to be formed using a more expensive manufacturing method such as a chemical vapor deposition method (CVD) method. In contrast, in the present 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 diamond particles, the material cost of the protective layer 45 is reduced. In addition, the protective layer 45 can be formed using a more expensive manufacturing method such as screen printing or coating using a dispenser. Therefore, the cost of the thermal print head 1 of the present embodiment becomes lower.

[0040] When the thermal print head 1 is in operation, the temperature of the portion of the protective layer 45 located on the heating resistor 40 usually reaches about 300° C., and sometimes temporarily reaches about 700° C. However, diamond particles do not decompose even at such high temperatures and can withstand such high temperatures.

[0041] In the thermal print head 1 of the present embodiment, the median diameter of the diamond particles is 0.5 times or less the thickness of the protective layer 45 .

[0042] Therefore, it is possible to prevent the surface of the protective layer 45 from being roughened. The contact of the printing medium with the protective layer 45 becomes smoother, and the printing quality is improved.

[0043] In the thermal print head 1 of the present embodiment, the ratio of the diamond particles in the protective layer 45 is 1 volume % or more and 50 volume % or less.

[0044] Since the proportion of diamond particles in the protective layer 45 is 1% by volume or more, the wear resistance of the protective layer 45 relative to the printing medium is improved, and the printing medium can be more reliably prevented from adhering to the protective layer 45. Since the proportion of diamond particles in the protective layer 45 is 1% by volume or more and 90% by volume or less, it is possible to prevent the surface of the protective layer 45 from being roughened. The contact of the printing medium with the protective layer 45 becomes smoother, and the printing quality is improved.

[0045] In the thermal print head 1 of the present embodiment, the diamond particles are industrial diamond powder.

[0046] Therefore, for example, the cost of the protective layer 45 can be significantly reduced compared to the case where the protective layer 45 is formed of diamond-like carbon (DLC). It is possible to suppress an increase in the cost of the thermal print head 1.

[0047] Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

[0048] (Note 1)

[0049] A thermal print head, comprising: a heating resistor;

[0050] a wiring layer connected to the heating resistor; and

[0051] a protective layer covering the heating resistor and the wiring layer,

[0052] The protective layer is an insulating layer to which diamond particles are added.

[0053] (Note 2)

[0054] The thermal print head according to Supplementary Note 1, wherein the median particle size of the diamond particles is less than or equal to 0.5 times the thickness of the protective layer.

[0055] (Note 3)

[0056] The thermal print head according to Supplementary Note 1 or 2, wherein the proportion of the diamond particles in the protective layer is 1 volume % or more and 90 volume % or less.

[0057] (Note 4)

[0058] The thermal print head as described in any one of Supplementary Notes 1 to 3, wherein the diamond particles are industrial diamond powder.

[0059] The embodiments disclosed this time should be considered to be illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A thermal print head, characterized in that: include: Heating resistor; A wiring layer connected to the heating resistor; and a protective layer covering the heating resistor and the wiring layer, The protective layer is an insulating layer to which diamond particles are added.

2. The thermal print head according to claim 1, wherein: The median particle size of the diamond particles is less than 0.5 times the thickness of the protective layer.

3. The thermal print head according to claim 1 or 2, characterized in that: The ratio of the diamond particles in the protective layer is 1 volume % or more and 90 volume % or less.

4. The thermal print head according to any one of claims 1 to 3, characterized in that: The diamond particles are industrial diamond powder.

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