Thermal printhead and method for manufacturing thermal printhead

Abstract

The invention provides a thermal print head and a thermal print head manufacturing method capable of suppressing occurrence of defects in a wiring layer. The thermal printhead includes: a substrate; a glaze layer disposed on the substrate; a wiring layer disposed on the glaze layer; and a protective layer disposed on the glaze layer so as to cover the wiring layer. At least one of a constituent material of the protective layer and a constituent material of the glaze layer is glass to which a constituent material of the wiring layer is added.

Description

Technical Field

[0001] The invention relates to a thermal print head and a method for manufacturing the thermal print head. Background Art

[0002] A thermal print head is described in Japanese Patent Publication No. 2023-115544 (Patent Document 1). The thermal print head described in Patent Document 1 has a substrate, a glaze layer, wiring, and a protective film. The substrate has a main surface. The glaze layer is arranged on the main surface of the substrate. The wiring is arranged on the glaze layer. The protective film is arranged on the glaze layer in a manner covering the wiring. The constituent material of the glaze layer and the constituent material of the protective film contain glass. The constituent material of the wiring is a metal material. Summary of the invention

[0003] During the manufacturing process of the thermal print head described in Patent Document 1, the metal material constituting the wiring diffuses into the glaze layer and the protective film. As a result, in the thermal print head described in Patent Document 1, the wiring may be damaged or disconnected.

[0004] The thermal print head of the present invention comprises a substrate, a glaze layer disposed on the substrate, a wiring layer disposed on the glaze layer, and a protective layer disposed on the glaze layer to cover the wiring. At least one of the constituent materials of the protective layer and the constituent materials of the glaze layer is glass to which the constituent material of the wiring layer is added. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 is a top view of the thermal print head 100 .

[0006] Figure 2 yes Figure 1 The cross-sectional view of I-II in FIG.

[0007] Figure 3 yes Figure 1 Cross-sectional view of III-III in FIG.

[0008] Figure 4 1 is a process diagram showing a method for manufacturing the thermal print head 100 .

[0009] Figure 5 It is a cross-sectional view for explaining the glaze layer forming step S2.

[0010] Figure 6 It is a cross-sectional view for explaining the metal layer forming step S3.

[0011] Figure 7 It is a cross-sectional view explaining the patterning step S4.

[0012] Figure 8 It is a cross-sectional view for explaining the heating element forming step S5.

[0013] Fig. 9 It is a cross-sectional view for explaining the protective layer forming step S6.

[0014] Fig.10 is a cross-sectional view of the thermal print head 200 . DETAILED DESCRIPTION

[0015] The details of the embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and repeated descriptions will not be repeated. The thermal print head of the embodiment is set to a thermal print head 100.

[0016] Next, the structure of the thermal print head 100 will be described.

[0017] Figure 1 FIG. 1 is a top view of the thermal print head 100. Figure 1 In the figure, the protective layer 50 is omitted. Figure 2 yes Figure 1 The cross-sectional view of II-II in FIG. Figure 3 yes Figure 1 The cross-sectional view of III-III in FIG. Figure 1 to Figure 3 As shown, the thermal print head 100 includes a substrate 10 , a glaze layer 20 , a wiring layer 30 , a heating element 40 , and a protective layer 50 .

[0018] The substrate 10 has a main surface 10a and a main surface 10b. The main surface 10b is the opposite surface of the main surface 10a. The main surface 10a and the main surface 10b are end surfaces in the thickness direction of the substrate 10. The main component of the constituent material of the substrate 10 is, for example, aluminum oxide (Al 2 O 3 ) and other ceramics. The main component is a component that accounts for more than 50% by mass in the constituent material.

[0019] The glaze layer 20 is disposed on the substrate 10. The glaze layer 20 is disposed on the main surface 10a. The main component of the constituent material of the glaze layer 20 is glass. The wiring layer 30 is disposed on the glaze layer 20. The wiring layer 30 has a common electrode 31 and a plurality of individual electrodes 32.

[0020] The common electrode 31 includes a strip-shaped portion 31a and a plurality of protrusions 31b. The strip-shaped portion 31a extends along the first direction DR1 when viewed from above. The view from above refers to the state of observing the thermal print head 100 along the normal direction of the main surface 10a. When viewed from above, the protrusion 31b protrudes from the strip-shaped portion 31a along the second direction DR2. The second direction DR2 is a direction perpendicular to the first direction DR1. More specifically, the protrusion 31b protrudes from the side of the strip-shaped portion 31a extending along the first direction DR1. The plurality of protrusions 31b are arranged at intervals along the first direction DR1.

[0021] In a plan view, a plurality of individual electrodes 32 are arranged at intervals along the first direction DR1. The individual electrode 32 has a front end 32a at one end and a bonding pad 32b at the other end. The front end 32a extends along the second direction DR2 in a plan view. The protrusions 31b and the front end 32a are alternately arranged at intervals along the first direction DR1 in a plan view.

[0022] The main component of the constituent material of the wiring layer 30 is a metal material. As a specific example of the metal material constituting the wiring layer 30, silver (Ag) can be cited. The wiring layer 30 is formed, for example, by a sintered body containing a plurality of silver particles. However, the constituent material of the wiring layer 30 is not limited thereto. The main component of the constituent material of the wiring layer 30 may be copper (Cu) or gold (Au).

[0023] The thickness of the wiring layer 30 is set to thickness T. The thickness T is preferably 1.5 μm or less. The narrowest portion of the portion of the wiring layer 30 covered by the protective layer 50 is set to be the narrowest portion. The width of the wiring layer 30 at the narrowest portion is, for example, 20 μm or less. The width of the wiring layer 30 at the narrowest portion may also be 15 μm or less. In addition, the narrowest portion is, for example, located at the front end portion 32a.

[0024] The heating element 40 extends along the first direction DR1 when viewed from above. The heating element 40 is arranged on the glaze layer 20 so as to overlap with the protrusion 31b and the front end portion 32a. Thus, the protrusion 31b and the front end portion 32a adjacent in the first direction DR1 are electrically connected to each other. The heating element 40 is made of, for example, ruthenium oxide (RuO 2 ) is formed by sintering of particles.

[0025] The protective layer 50 is arranged on the glaze layer 20 in a manner covering the wiring layer 30 and the heating element 40. However, the bonding pad 32b is exposed from the protective layer 50. The main component of the constituent material of the protective layer 50 is glass. The constituent material of the wiring layer 30 (silver in the above example) is added to the constituent material of the protective layer 50. For example, particles containing the constituent material of the wiring layer 30 are dispersed in the protective layer 50. In addition, the constituent material of the wiring layer 30 can also be dissolved in the glass contained in the protective layer 50.

[0026] When the constituent material of the wiring layer 30 is dissolved in the glass contained in the protective layer 50, the content of the constituent material of the wiring layer 30 in the glass is preferably 4% by mass or more and preferably 25% by mass or less. The content of the constituent material of the wiring layer 30 in the glass contained in the protective layer 50 is measured using an elemental analysis device (SEM-EDX) at a position where the distance from the interface between the wiring layer 30 and the protective layer 50 is a predetermined value in the thickness direction of the protective layer 50. The predetermined value is, for example, 2 μm when the thickness of the protective layer 50 is 4 μm, and 5 μm when the thickness of the protective layer 50 is 8 μm.

[0027] <Modification>

[0028] In the above, an example in which the constituent material of the wiring layer 30 is added to the protective layer 50 is described, but the constituent material of the wiring layer 30 may be added to the glaze layer 20, or may be added to both the protective layer 50 and the glaze layer 20. When the constituent material of the wiring layer 30 is added to the glaze layer 20, the constituent material of the wiring layer 30 may be added as particles dispersed in the glaze layer 20, or may be added in the form of being dissolved in the glass constituting the glaze layer 20. When the constituent material of the wiring layer 30 is added to the glaze layer 20 in the form of being dissolved in the glass, the content of the constituent material of the wiring layer 30 in the glass is preferably 4% by mass or more and preferably 25% by mass or less. The content of the constituent material of the wiring layer 30 in the glass contained in the glaze layer 20 is measured using an elemental analyzer at a position at a predetermined distance from the interface between the wiring layer 30 and the glaze layer 20 in the thickness direction of the glaze layer 20. The predetermined value is, for example, 50 μm when the thickness of the glaze layer 20 is 100 μm, and 100 μm when the thickness of the glaze layer 20 is 200 μm.

[0029] (Method of Manufacturing Thermal Print Head 100)

[0030] Next, a method for manufacturing the thermal print head 100 will be described.

[0031] Figure 4 1 is a process diagram showing a method for manufacturing the thermal print head 100. Figure 4 As shown, the method for manufacturing the thermal print head 100 includes a preparation step S1 , a glaze layer forming step S2 , a metal layer forming step S3 , a patterning step S4 , a heating element forming step S5 , a protective layer forming step S6 , and a singulation step S7 .

[0032] The glaze layer forming step S2 is performed after the preparation step S1. The metal layer forming step S3 is performed after the glaze layer forming step S2. The patterning step S4 is performed after the metal layer forming step S3. The heating element forming step S5 is performed after the patterning step S4. The protective layer forming step S6 is performed after the heating element forming step S5. The singulation step S7 is performed after the protective layer forming step S6.

[0033] In the preparation step S1 , the substrate 10 is prepared. Figure 5 2 is a cross-sectional view illustrating the glaze layer forming step S2. Figure 5As shown, in the glaze layer forming step S2, the glaze layer 20 is formed on the main surface 10a. The glaze layer 20 is formed by applying a paste containing glass on the main surface 10a and sintering the applied paste. In addition, in the case where the constituent material of the wiring layer 30 is added to the glaze layer 20 as particles, the particles formed by the constituent material of the wiring layer 30 are mixed with the above-mentioned paste. In addition, in the case where the constituent material of the wiring layer 30 is added to the glaze layer 20 in the form of being dissolved in glass, the constituent material of the wiring layer 30 is dissolved in the glass contained in the above-mentioned paste in advance.

[0034] Figure 6 2 is a cross-sectional view illustrating the metal layer forming step S3. Figure 6 As shown, in the metal layer forming step S3, the metal layer 33 is formed on the glaze layer 20. The metal layer 33 is formed by applying a paste containing particles formed of a constituent material of the wiring layer 30 on the glaze layer 20 and sintering the applied paste. Figure 7 is a cross-sectional view illustrating the patterning step S4. Figure 7 As shown, in the patterning step S4, the wiring layer 30 is formed by patterning the metal layer 33. The metal layer 33 is patterned by etching using a resist pattern formed on the metal layer 33 as a mask. The resist pattern is formed by applying a photoresist on the metal layer 33 and exposing and developing the applied photoresist.

[0035] Figure 8 2 is a cross-sectional view illustrating the heating element forming step S5. Figure 8 As shown, in the heating element forming step S5, the heating element 40 is formed on the glaze layer 20 so as to overlap the protrusion 31b and the front end 32a and extend along the first direction DR1 in a plan view. The heating element 40 is formed by applying a paste containing ruthenium oxide particles and sintering the applied paste.

[0036] Fig. 9 2 is a cross-sectional view illustrating the protective layer forming step S6. Fig. 9 As shown, in the protective layer forming step S6, a protective layer 50 is formed. The protective layer 50 is formed by applying a paste containing glass on the glaze layer 20 in a manner covering the wiring layer 30 and the heating element 40, and sintering the applied paste. In addition, in the case where the constituent material of the wiring layer 30 is added to the protective layer 50 as particles, the particles formed by the constituent material of the wiring layer 30 are mixed into the above-mentioned paste. In addition, in the case where the constituent material of the wiring layer 30 is added to the protective layer 50 in the form of being dissolved in glass, the constituent material of the wiring layer 30 is dissolved in the glass contained in the above-mentioned paste in advance.

[0037] In the singulation step S7, the substrate 10, the glaze layer 20, and the protective layer 50 are cut to obtain a plurality of thermal print heads 100. Figure 1 to Figure 3 The structure of the thermal print head 100 is shown.

[0038] (Effect of thermal print head 100)

[0039] Next, the effects of the thermal print head 100 will be described.

[0040] The thermal print head of the comparative example is referred to as a thermal print head 200 . Fig.10 2 is a cross-sectional view of the thermal print head 200. Fig.10 As shown, the thermal print head 200 has a glaze layer 21 instead of the glaze layer 20 and a protective layer 51 instead of the protective layer 50. The constituent material of the wiring layer 30 is not added to the glaze layer 21 and the protective layer 51. The structure of the thermal print head 200 is the same as that of the thermal print head 100 except for these points.

[0041] When the glass-containing paste is sintered to form the protective layer 51, the constituent material of the wiring layer 30 diffuses into the protective layer 51. Similarly, by heating when forming the metal layer 33 and heating when forming the protective layer 51, the constituent material of the wiring layer 30 diffuses into the glaze layer 21. As a result of the above diffusion, defects may occur in the wiring layer 30 (see Fig.10 The part surrounded by the dotted line in ).

[0042] From the viewpoint of being able to effectively utilize the heat generated by the heating element 40, the thickness T is sometimes reduced, but if the thickness T is reduced (for example, the thickness T is 1.5 μm or less), the wiring layer 30 is easily damaged, and the wiring layer 30 is sometimes disconnected. In addition, in order to reduce the manufacturing cost, the constituent material of the wiring layer 30 is sometimes switched from gold to silver, but since silver diffuses into glass more easily than gold, when silver is used as the constituent material of the wiring layer 30, the wiring layer 30 is easily damaged.

[0043] The thermal print head 100 is also heated to form the protective layer 50. However, since the constituent material of the wiring layer 30 is added to the protective layer 50, the concentration gradient of the constituent material of the wiring layer 30 between the wiring layer 30 and the protective layer 50 becomes smaller, and thus, the constituent material of the wiring layer 30 is not easy to diffuse from the wiring layer 30 to the protective layer 50, and the wiring layer 30 is not easy to be damaged. Similarly, if the constituent material of the wiring layer 30 is also added to the glaze layer 20, the diffusion of the constituent material of the wiring layer 30 to the glaze layer 20 is also suppressed, and as a result, the wiring layer 30 is further difficult to be damaged.

[0044] When the constituent material of the wiring layer 30 contains silver or copper, the manufacturing cost of the thermal print head 100 can be reduced compared to the case where the constituent material of the wiring layer 30 contains gold. In addition, when the constituent material of the wiring layer 30 is silver, the diffusion of the constituent material of the wiring layer 30 into the protective layer 50 or the glaze layer 20 becomes significant, but in the thermal print head 100, even if the constituent material of the wiring layer 30 is silver, the diffusion into the protective layer 50 or the glaze layer 20 can be sufficiently suppressed. In addition, when the thickness T is 1.5 μm or less, the heat dissipation from the heating element 40 via the wiring layer 30 is suppressed, but the wiring layer 30 is easily broken. In the thermal print head 100, even if the thickness T is 1.5 μm or less, the wiring layer 30 can be suppressed from breaking.

[0045] If the content of the constituent material of the wiring layer 30 in the glass contained in the protective layer 50 or the glaze layer 20 is too small, the effect of suppressing the diffusion of the constituent material of the wiring layer 30 becomes insufficient. Therefore, by setting the content of the constituent material of the wiring layer 30 in the glass contained in the protective layer 50 or the glaze layer 20 to 4% by mass or more, the diffusion of the constituent material of the wiring layer 30 can be more reliably suppressed. If the content of the constituent material of the wiring layer 30 in the glass contained in the protective layer 50 or the glaze layer 20 is too large, the protective layer 50 or the glaze layer 20 exhibits conductivity, and there is a possibility that the original function of the protective layer 50 or the glaze layer 20 cannot be exerted. Therefore, by setting it to 25% by mass or less, the electrical insulation of the protective layer 50 or the glaze layer 20 can be more reliably ensured.

[0046] (Note)

[0047] The embodiments of the present invention include the following structures.

[0048] <Additional Note 1>

[0049] A thermal print head, comprising:

[0050] substrate;

[0051] a glaze layer disposed on the substrate;

[0052] a wiring layer disposed on the glaze layer; and

[0053] a protective layer disposed on the glaze layer so as to cover the wiring layer,

[0054] At least one of the constituent material of the protective layer and the constituent material of the glaze layer is glass to which the constituent material of the wiring layer is added.

[0055] <Note 2>

[0056] The thermal print head according to Supplement 1, wherein:

[0057] The constituent material of the protective layer is glass to which the constituent material of the wiring layer is added.

[0058] <Addendum 3>

[0059] The thermal print head according to Supplement 2, wherein:

[0060] In the protective layer, particles including a constituent material of the wiring layer are dispersed in glass.

[0061] <Addendum 4>

[0062] The thermal print head according to Supplement 2, wherein:

[0063] In the protective layer, a constituent material of the wiring layer is dissolved in glass, and a concentration of the constituent material of the wiring layer in the glass is 4 mass % or more.

[0064] <Addendum 5>

[0065] The thermal print head according to any one of Supplementary Notes 1 to 4, wherein:

[0066] The wiring layer has a thickness of 1.5 μm or less.

[0067] <Addendum 6>

[0068] The thermal print head according to any one of Supplementary Notes 1 to 5, wherein:

[0069] The wiring layer is made of silver.

[0070] <Addendum 7>

[0071] The thermal print head according to any one of Supplementary Notes 1 to 5, wherein:

[0072] The wiring layer is made of copper.

[0073] <Addendum 8>

[0074] A method for manufacturing a thermal print head, comprising:

[0075] A process for preparing a substrate;

[0076] forming a glaze layer on the substrate;

[0077] forming a wiring layer on the glaze layer; and

[0078] forming a protective layer on the glaze layer so as to cover the wiring layer,

[0079] At least one of the constituent material of the protective layer and the constituent material of the glaze layer is glass to which the constituent material of the wiring layer is added.

[0080] The embodiments of the present invention have been described above, but 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, 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: substrate; a glaze layer disposed on the substrate; a wiring layer disposed on the glaze layer; and a protective layer disposed on the glaze layer so as to cover the wiring layer, At least one of the constituent material of the protective layer and the constituent material of the glaze layer is glass to which the constituent material of the wiring layer is added.

2. The thermal print head according to claim 1, characterized in that: The constituent material of the protective layer is glass to which the constituent material of the wiring layer is added.

3. The thermal print head according to claim 2, characterized in that: In the protective layer, particles including a constituent material of the wiring layer are dispersed in glass.

4. The thermal print head according to claim 2, characterized in that: In the protective layer, a constituent material of the wiring layer is dissolved in glass, and a concentration of the constituent material of the wiring layer in the glass is 4 mass % or more.

5. The thermal print head according to any one of claims 1 to 4, characterized in that: The wiring layer has a thickness of 1.5 μm or less.

6. The thermal print head according to any one of claims 1 to 5, characterized in that: The wiring layer is made of silver.

7. The thermal print head according to any one of claims 1 to 5, characterized in that: The wiring layer is made of copper.

8. A method for manufacturing a thermal print head, characterized in that: include: A process for preparing a substrate; forming a glaze layer on the substrate; forming a wiring layer on the glaze layer; and forming a protective layer on the glaze layer so as to cover the wiring layer, At least one of the constituent material of the protective layer and the constituent material of the glaze layer is glass to which the constituent material of the wiring layer is added.

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