Thermal print head and method for manufacturing thermal print head

Abstract

To provide a thermal print head which improves durability.SOLUTION: A thermal print head 100 has a heat generation part 5. The thermal print head 100 includes a first protective film 4a and a second protective film 4b. The first protective film 4a covers the heat generation part 5. The second protective film 4b is formed on the first protective film 4a. In plan view of the first protective film 4a, the second protective film 4b overlaps the heat generation part 5. The second protective film 4b is a metal protective film containing at least any one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide and titanium aluminide.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a thermal print head and a method for manufacturing a thermal print head.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2022-78589 (Patent Document 1) discloses a thermal print head having a protective layer that covers a heating resistor. The material constituting the protective layer is glass.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] A thermal print head according to an aspect of the present disclosure has a heating portion. The thermal print head includes a first protective film and a second protective film. The first protective film covers the heating portion. The second protective film is formed on the first protective film. In a plan view of the first protective film, the second protective film overlaps the heating portion. The second protective film is a metal protective film containing at least one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminum nitride.

[0005] A method for manufacturing a thermal print head according to an aspect of the present disclosure includes a step of forming a first protective film and a step of forming a second protective film. The thermal print head has a heating portion. In the step of forming the second protective film, the second protective film is formed on the first protective film so as to overlap the heating portion in a plan view of the first protective film. The second protective film is a metal protective film containing at least one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminum nitride.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

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Figure 9

[0007] Embodiment 1. (Configuration of Thermal Print Head) FIG. 1 is a schematic plan view of the thermal print head 100 according to Embodiment 1. FIG. 2 is a schematic partial cross-sectional view of the thermal print head 100 taken along line II-II in FIG. 1. In FIG. 1, illustration of the first protective film 4a and the second protective film 4b is omitted.

[0008] The thermal print head 100 shown in FIGS. 1 and 2 includes an insulating substrate 1, a glaze layer 20, a wiring layer 30, a heat generating portion 5, a first protective film 4a, and a second protective film 4b.

[0009] As shown in FIG. 2, the insulating substrate 1 has a first surface 10a and a second surface 10b. The first surface 10a and the second surface 10b are end surfaces in the thickness direction of the insulating substrate 1. The second surface 10b is a surface on the opposite side of the first surface 10a. The shape of the insulating substrate 1 in plan view of the first surface 10a is, for example, rectangular. The direction perpendicular to the first surface 10a is defined as the z direction. The direction perpendicular to the z direction is defined as the x direction. The direction perpendicular to the x direction and the z direction is defined as the y direction. Plan view means the case of viewing from the side of the first surface 10a along the z direction of the first surface 10a. The x direction corresponds to the longitudinal direction of the insulating substrate 1 in plan view. As will be described later, the x direction is the direction in which the heat generating portion 5 extends. The y direction corresponds to the short-side direction of the insulating substrate 1 in plan view.

[0010] The insulating substrate 1 has a first side surface 10c and a second side surface 10d. Each of the first side surface 10c and the second side surface 10d is a surface connecting the first surface 10a and the second surface 10b. The second side surface 10d is a surface on the opposite side of the first side surface 10c.

[0011] The material constituting the insulating substrate 1 is, for example, ceramic. The material constituting the insulating substrate 1 may be a material mainly composed of ceramic such as alumina (Al2O3).

[0012] As shown in FIG. 2, the glaze layer 20 is connected to the first surface 10a. As shown in FIG. 1, the glaze layer 20 may be formed over the entire first surface 10a. The material constituting the glaze layer 20 is, for example, glass.

[0013] As shown in FIG. 2, the wiring layer 30 is connected to the glaze layer 20. As shown in FIG. 1, the wiring layer 30 has a main body portion 30a, a plurality of protruding portions 30b, and a plurality of individual electrode portions 31.

[0014] In a plan view of the first surface 10a, the shape of the main body portion 30a is, for example, rectangular. The main body portion 30a extends along the x direction. The main body portion 30a is on the side of the first side surface 10c in the y direction. That is, the distance between the main body portion 30a and the first side surface 10c in the y direction is smaller than the distance between the main body portion 30a and the second side surface 10d in the y direction. The protruding portions 30b protrude along the y direction from the side facing the second side surface 10d of the main body portion 30a. The plurality of protruding portions 30b are arranged at equal intervals along the x direction.

[0015] One end of the individual electrode portion 31 in the y direction is closer to the first side surface 10c than the other end of the individual electrode portion 31 in the y direction. The individual electrode portion 31 has a tip portion 31a at one end in the y direction. The tip portion 31a extends along the y direction. The protruding portions 30b and the tip portions 31a are alternately arranged with a space therebetween in the x direction. The individual electrode portion 31 has a pad 31b at the other end in the y direction. The thermal print head 100 is electrically connected to a driver IC (not shown) at the pad 31b.

[0016] The material constituting the wiring layer 30 is, for example, a material having conductivity. Specifically, the material constituting the wiring layer 30 is a metal material. The material constituting the wiring layer 30 may be, for example, gold (Au).

[0017] As shown in FIG. 2, the heat generating portion 5 is formed so as to be connected to the individual electrode portion 31. The heat generating portion 5 extends along the x direction. A part of the heat generating portion 5 overlaps the protruding portion 30b and the tip portion 31a.

[0018] The heat generating portion 5 has, for example, glass and a plurality of conductive particles mixed in the glass. The conductive particles are formed of, for example, ruthenium oxide (RuO2).

[0019] A voltage is selectively applied to the individual electrode portion 31 by the driver IC. As a result, a current flows through the portion of the heat generating portion 5 that electrically connects the tip portion 31a of the individual electrode portion 31 to which the voltage is applied and the protruding portion 30b adjacent thereto. As a result, the heat generating portion 5 generates heat. Due to this heat generation, printing on the paper in contact with the heat generating portion 5 is performed.

[0020] As shown in FIG. 2, the first protective film 4a is formed over the entire glaze layer 20. That is, the first protective film 4a covers the wiring layer 30 and the heat generating portion 5. The material constituting the first protective film 4a is, for example, glass. The pad 31b may be exposed from the first protective film 4a.

[0021] As shown in FIG. 2, the second protective film 4b is formed on the first protective film 4a. From a different perspective, the second protective film 4b is directly connected to the first protective film 4a. In a plan view of the first protective film 4a, the second protective film 4b is arranged so as to overlap the heat generating portion 5. That is, the second protective film 4b extends along the x direction (not shown). The second protective film 4b may be formed over the entire first protective film 4a. The material constituting the second protective film 4b is a metal protective film containing any one of silver, gold, palladium, nickel, copper, and aluminum. The metal protective film is formed by baking a metal paste containing any one of silver, gold, palladium, nickel, copper, and aluminum.

[0022] Here, the feature of the thermal print head 100 according to the first embodiment is that the material constituting the second protective film 4b contains at least any one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminate. Since the second protective film 4b contains at least any one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminate, the durability of the thermal print head 100 is improved.

[0023] In order to improve the durability of the protective film covering the heat generating portion 5, a silicon carbide (SiC) film may be formed on the first protective film 4a, but the silicon carbide film is formed by sputtering. Therefore, a vacuum apparatus is required to form the silicon carbide film, and the manufacturing cost of the thermal print head 100 increases.

[0024] As will be described later, in the thermal print head 100 according to the first embodiment, the metal protective film is formed by baking a mixed paste. The mixed paste is a metal paste in which at least any one of the high-hardness fillers such as diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminate is added to the above-described metal paste. Therefore, the manufacturing cost of the thermal print head 100 with improved durability can be reduced.

[0025] In the second protective film 4b, the above-described high-hardness filler may be dispersedly arranged in the metal film as a base material. Further, a plurality of high-hardness fillers may be exposed on the surface of the second protective film 4b (the surface on the opposite side of the back surface in contact with the first protective film 4a in the second protective film 4b). Since the high-hardness filler is exposed on the surface of the second protective film 4b, the durability of the second protective film 4b can be surely improved. The content rate of the high-hardness filler in the second protective film 4b may be, for example, 10% by volume or more and 70% by volume or less. The content rate of the high-hardness filler may be 20% by volume or more, and may be 30% by volume or more. The content rate of the high-hardness filler may be 60% by volume or less, and may be 50% by volume or less.

[0026] The material constituting the second protective film 4b may be either copper or aluminum. A metal paste containing copper or aluminum can be obtained at a lower cost than a metal paste containing silver or gold. In this way, the manufacturing cost of the thermal print head 100 with improved durability can be further reduced.

[0027] The material constituting the second protective film 4b may be aluminum. In this way, aluminum is oxidized and alumina is formed on the second protective film 4b. As a result, the durability of the thermal print head 100 is further improved.

[0028] The Vickers hardness of the second protective film 4b may be, for example, 500 HV or more. The Vickers hardness of the second protective film 4b may be, for example, 1000 HV or more. In this way, a thermal print head 100 with improved durability can be obtained.

[0029] The material constituting the second protective film 4b may be confirmed by any method. For example, the material constituting the second protective film 4b may be measured by energy dispersive X-ray analysis.

[0030] Increasing the content of the high-hardness filler deteriorates the surface roughness of the second protective film 4b. Therefore, a third protective film may be further formed on the second protective film 4b. The third protective film is formed by baking a metal paste that does not contain a filler. In this way, the second protective film 4b with deteriorated surface roughness can be covered with the third protective film.

[0031] (Method for manufacturing a thermal print head) Hereinafter, a method for manufacturing the thermal print head 100 will be described. FIG. 3 is a flowchart in the method for manufacturing the thermal print head 100 according to the first embodiment. FIGS. 4 to 9 are schematic partial cross-sectional views showing one step in the method for manufacturing the thermal print head 100 according to the first embodiment.

[0032] As shown in FIG. 4, in the method for manufacturing the thermal print head 100, first, a step (S1) of preparing the insulating substrate 1 is performed. In this step (S1), as shown in FIG. 4, the insulating substrate 1 is prepared.

[0033] Next, a step (S2) of forming the glaze layer 20 is performed. In this step (S2), as shown in FIG. 5, the glaze layer 20 is formed on the first surface 10a. Specifically, a paste containing glass is applied onto the first surface 10a. Next, the applied paste is heated. As a result, the solvent in the paste evaporates and the glass in the paste is bonded to each other, thereby forming the glaze layer 20.

[0034] Next, a step (S3) of forming the wiring layer 30 is performed. In this step (S3), as shown in FIG. 6, the wiring layer 30 is formed on the glaze layer 20. The wiring layer 30 is formed by applying a resinate paste containing the material constituting the wiring layer 30 onto the glaze layer 20 and firing the resinate paste. However, the method for forming the wiring layer 30 is not limited thereto.

[0035] Next, the step of patterning the wiring layer 30 (S4) is performed. In this step (S4), as shown in FIG. 7, by patterning the wiring layer 30, the main body portion 30a, the plurality of protruding portions 30b, and the plurality of individual electrode portions 31 are formed. First, a resist is applied on the wiring layer 30 (not shown). The resist is applied, for example, using a roll coater. Next, the resist applied on the wiring layer 30 is exposed. The exposure is performed, for example, by partially irradiating the resist with UV (Ultra Violet) light using a glass mask. The resist in the portion irradiated with the UV light is altered. Next, a resist pattern is formed by dissolving and removing the portion of the resist altered by the exposure. Next, by etching the wiring layer 30 using the resist pattern as a mask, the main body portion 30a, the plurality of protruding portions 30b, and the plurality of individual electrode portions 31 (see FIG. 1) are formed. Note that the resist pattern is removed after the etching of the wiring layer 30.

[0036] Next, the step of forming the heat generating portion 5 (S5) is performed. In this step (S5), as shown in FIG. 8, the heat generating portion 5 is formed. First, a conductive paste containing glass and ruthenium oxide particles is applied on the wiring layer 30. Next, the applied conductive paste is fired.

[0037] Next, the step of forming the first protective film 4a (S6) is performed. In this step (S6), as shown in FIG. 9, the first protective film 4a covering the glaze layer 20, the wiring layer 30, and the heat generating portion 5 is formed.

[0038] Next, the step of forming the second protective film 4b (S7) is performed. The step of forming the second protective film 4b (S7) includes a step of applying a mixed paste on the first protective film 4a (S7a) and a step of firing the mixed paste (S7b).

[0039] First, a step of applying a mixed paste (S7a) is performed. The mixed paste is applied onto the first protective film 4a so as to overlap the heat generating portion 5 in a plan view of the first protective film 4a. The mixed paste may be composed of a metal paste and a high-hardness filler. The metal paste contains any one of silver, gold, palladium, nickel, copper, and aluminum. The high-hardness filler is at least any one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminum nitride. That is, the mixed paste may be a paste mainly composed of a metal paste added with the high-hardness filler as described above. The high-hardness filler may be added to the metal paste using a dispersant.

[0040] The mixed paste may be composed of a metal paste and a high-hardness paste. Specifically, the metal paste contains aluminum. The high-hardness paste is a paste containing diamond particles. That is, the mixed paste may be a paste in which the high-hardness paste is mixed with the metal paste as the main component as described above. In this way, the mixed paste can be prepared without the need for a dispersant. As a result, a thermal print head 100 with improved durability can be easily obtained.

[0041] Next, a step of firing the mixed paste (S7b) is performed. By firing the mixed paste, a second protective film 4b is formed on the first protective film 4a.

[0042] In this way, the thermal print head 100 with improved durability shown in FIGS. 1 and 2 can be obtained. Also, since the second protective film 4b can be formed by firing the mixed paste without the need for large equipment such as a vacuum device, a thermal print head 100 with improved durability can be easily obtained.

[0043] (Function and Effect) The thermal print head 100 according to the present disclosure has a heat generating portion 5. The thermal print head 100 includes a first protective film 4a and a second protective film 4b. The first protective film 4a covers the heat generating portion 5. The second protective film 4b is formed on the first protective film 4a. In a plan view of the first protective film 4a, the second protective film 4b overlaps the heat generating portion 5. The second protective film 4b is a metal protective film containing at least any one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminide.

[0044] In this way, a thermal print head 100 with improved durability can be obtained. Also, since a large-scale facility such as a vacuum device is not required and the second protective film 4b can be formed by firing a mixed paste, a thermal print head 100 with improved durability can be easily obtained.

[0045] In the thermal print head 100, the material constituting the metal protective film contains any one of silver, gold, palladium, nickel, copper, and aluminum.

[0046] In this way, a thermal print head 100 with improved durability can be obtained. Also, since a large-scale facility such as a vacuum device is not required and the second protective film 4b can be formed by firing a mixed paste, a thermal print head 100 with improved durability can be easily obtained.

[0047] In the thermal print head 100, the Vickers hardness of the second protective film 4b is 500 HV or more.

[0048] In this way, a thermal print head 100 with improved durability can be obtained.

[0049] In the thermal print head 100, the Vickers hardness of the second protective film 4b is 1000 HV or more.

[0050] By doing so, a thermal print head 100 with improved durability can be obtained.

[0051] In the thermal print head 100, the second protective film 4b is directly connected to the first protective film 4a.

[0052] By doing so, the heat generating portion 5 is protected by the second protective film 4b via the first protective film 4a.

[0053] The method for manufacturing the thermal print head 100 according to the present disclosure includes a step (S6) of forming the first protective film 4a and a step (S7) of forming the second protective film 4b. The thermal print head 100 has a heat generating portion 5. In the step (S7) of forming the second protective film 4b, the second protective film 4b is formed on the first protective film 4a so as to overlap the heat generating portion 5 in a plan view of the first protective film 4a. The second protective film 4b is a metal protective film containing at least one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminum nitride.

[0054] By doing so, a thermal print head 100 with improved durability can be obtained. Further, since a large-scale facility such as a vacuum device is not required and the second protective film 4b can be formed by firing the mixed paste, a thermal print head 100 with improved durability can be easily obtained.

[0055] In the method for manufacturing the thermal print head 100, the step (S7) of forming the second protective film 4b includes a step (S7a) of applying a mixed paste on the first protective film 4a and a step (S7b) of firing the mixed paste.

[0056] By doing so, a thermal print head 100 with improved durability can be obtained. Further, since a large-scale facility such as a vacuum device is not required and the second protective film 4b can be formed by firing the mixed paste, a thermal print head 100 with improved durability can be easily obtained.

[0057] In the method for manufacturing the thermal print head 100 described above, the mixed paste includes a metal paste and a high-hardness filler. The metal paste includes any one of silver, gold, palladium, nickel, copper, and aluminum. The high-hardness filler is at least any one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminate.

[0058] In this way, a thermal print head 100 with improved durability can be obtained. Also, since a large-scale facility such as a vacuum device is not required and the second protective film 4b can be formed by firing the mixed paste, a thermal print head 100 with easily improved durability can be obtained.

[0059] In the method for manufacturing the thermal print head 100 described above, the mixed paste includes a metal paste and a high-hardness paste. The metal paste includes aluminum. The high-hardness paste includes diamond.

[0060] In this way, the mixed paste can be prepared without the need for a dispersant. As a result, a thermal print head 100 with easily improved durability can be obtained.

[0061] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. As long as there is no contradiction, at least two of the embodiments disclosed this time may be combined. The basic scope of the present disclosure is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

[0062] The present disclosure includes the following aspects. (Appendix 1) A thermal print head having a heat generating portion, a first protective film covering the heat generating portion, and a second protective film formed on the first protective film. In a plan view of the first protective film, the second protective film overlaps the heat generating portion. The second protective film is a metal protective film containing at least one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminum nitride, and is a thermal print head. (Appendix 2) The material constituting the metal protective film includes any one of silver, gold, palladium, nickel, copper, and aluminum, and is the thermal print head according to Appendix 1. (Appendix 3) The Vickers hardness of the second protective film is 500 HV or more, and is the thermal print head according to Appendix 1 or Appendix 2. (Appendix 4) The Vickers hardness of the second protective film is 1000 HV or more, and is the thermal print head according to Appendix 3. (Appendix 5) The second protective film is directly connected to the first protective film, and is the thermal print head according to any one of Appendices 1 to 4. (Appendix 6) A method for manufacturing a thermal print head having a heat generating portion, A step of forming a first protective film, And a step of forming a second protective film, In the step of forming the second protective film, The second protective film is formed on the first protective film so as to overlap the heat generating portion in a plan view of the first protective film, The second protective film is a metal protective film containing at least one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminum nitride, and is a method for manufacturing a thermal print head. (Appendix 7) The step of forming the second protective film is A step of applying a mixed paste on the first protective film, And a step of firing the mixed paste, and is a method for manufacturing a thermal print head according to Appendix 6. (Appendix 8) The method for manufacturing a thermal print head according to Supplementary Note 7, wherein the mixed paste includes a metal paste containing any one of silver, gold, palladium, nickel, copper, and aluminum, and a high-hardness filler that is at least any one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminide. (Supplementary Note 9) The method for manufacturing a thermal print head according to Supplementary Note 7, wherein the mixed paste includes a metal paste containing aluminum and a high-hardness paste containing diamond.

Explanation of Reference Signs

[0063] 1 Insulating substrate, 4a First protective film, 4b Second protective film, 5 Heating portion, 10a First surface, 10b Second surface, 10c First side surface, 10d Second side surface, 20 Glaze layer, 30 Wiring layer, 30a Main body portion, 30b Protruding portion, 31 Individual electrode portion, 31a Tip portion, 31b Pad, 100 Thermal print head.

Claims

1. A thermal print head having a heat generating portion, comprising: a first protective film covering the heat generating portion; a second protective film formed on the first protective film, wherein in a plan view of the first protective film, the second protective film overlaps the heat generating portion; and the second protective film is a metal protective film containing at least one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminum nitride.

2. The thermal print head according to claim 1, wherein the material constituting the metal protective film contains any one of silver, gold, palladium, nickel, copper, and aluminum.

3. The thermal print head according to claim 1 or claim 2, wherein the Vickers hardness of the second protective film is 500 HV or more.

4. The thermal print head according to claim 3, wherein the Vickers hardness of the second protective film is 1000 HV or more.

5. The thermal print head according to claim 1 or claim 2, wherein the second protective film is directly connected to the first protective film.

6. A method for manufacturing a thermal print head having a heat generating portion, comprising: a step of forming a first protective film; a step of forming a second protective film, wherein in the step of forming the second protective film, the second protective film is formed on the first protective film so as to overlap the heat generating portion in a plan view of the first protective film; and the second protective film is a metal protective film containing at least one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminum nitride.

7. The step of forming the second protective film includes a step of applying a mixed paste on the first protective film and a step of firing the mixed paste.

8. The method for manufacturing a thermal print head according to claim 7, wherein the mixed paste contains a metal paste containing any one of silver, gold, palladium, nickel, copper, and aluminum and a high-hardness filler that is at least one of diamond, boron nitride, alumina, silicon carbide, tungsten carbide, and titanium aluminum nitride.

9. The method for manufacturing a thermal print head according to claim 7, wherein the mixed paste includes a metal paste containing aluminum and a high-hardness paste containing diamond.

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