JP2023082293A - Thermal print head, and manufacturing method of thermal print head - Google Patents

Abstract

To provide a thermal print head and a manufacturing method of the thermal print head that improve printing efficiency.SOLUTION: A thermal print head A1 comprises: a head substrate 1; a resistor layer 4 which has a plurality of heating parts 41 arrayed in a main scanning direction x, and is supported on the head substrate 1; a wiring layer 3 which constitutes an electric conduction path to the plurality of heating parts 41, and is supported on the head substrate 1; and a protective layer 2 which covers the resistor layer 4 and the wiring layer 3. The protective layer 2 includes a first layer 21 containing a silicon element. A refraction factor of the first layer 21 is higher than a refraction factor of silicon nitride (Si3 N4) in which a silicon element and a nitrogen element are composed in a stoichiometric composition ratio, and equal to or less than a refraction factor of intrinsic silicon being an intrinsic semiconductor.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to thermal printheads and methods of manufacturing thermal printheads.

Patent Document 1 discloses an example of a conventional thermal printhead. The thermal printhead described in the same document includes a substrate (heat dissipation substrate), electrode wiring, heating resistors, and a protective layer (abrasion resistant protective layer). Electrode wiring and heating resistors are formed on the substrate. The electrode wiring is for energizing the heating resistor. The heating resistors are heat sources, and are arranged in a row at a predetermined pitch in the main scanning direction. A protective layer covers the electrode wiring and the heating resistor. The protective layer is made of silicon oxide (SiO ₂ ), for example. Such a thermal print head performs printing on a print medium by conducting heat generated by energizing a heating resistor to the print medium through a protective layer.

JP 2012-116131 A

Thermal print heads are required to efficiently transfer heat generated by heating resistors to a print medium to improve printing efficiency, for example, in order to save power.

The present disclosure has been conceived in view of the above circumstances, and an object thereof is to provide a thermal print head and a method for manufacturing a thermal print head that improve printing efficiency.

A thermal printhead provided by a first aspect of the present disclosure includes a substrate, a plurality of heat generating portions arranged in a main scanning direction, a resistor layer supported by the substrate, and the plurality of heat generating portions. and a wiring layer supported by the substrate, and a protective layer covering the resistor layer and the wiring layer, the protective layer comprising a first layer containing a silicon element, The refractive index of the first layer is higher than the refractive index of silicon nitride composed of silicon element and nitrogen element in a stoichiometric composition ratio, and is lower than the refractive index of intrinsic silicon, which is an intrinsic semiconductor.

A method for manufacturing a thermal printhead provided by the second aspect of the present disclosure includes a step of preparing a base material; forming a body layer; forming a wiring layer supported by the base material, forming a current path to the plurality of heat-generating portions; and forming a protective layer covering the resistor layer and the wiring layer. forming the protective layer includes forming a first layer containing a silicon element, and forming the first layer comprises ammonia (NH ₃ ) and silane (SiH ₄ ), and the ratio (NH ₃ /SiH ₄ ) of ammonia (NH ₃ ) and silane (SiH ₄ ) in the source gas is 0.1 or more and 4 or less.

According to the thermal print head of the present disclosure, it is possible to improve printing efficiency. Further, according to the method of manufacturing a thermal printhead of the present disclosure, it is possible to manufacture a thermal printhead with improved printing efficiency.

1 is a plan view showing a thermal print head according to an embodiment; FIG. FIG. 2 is an enlarged plan view of a part of the plan view shown in FIG. 3 is a partially enlarged cross-sectional view of a thermal printer having a thermal print head according to the embodiment, taken along line III-III of FIG. 1. FIG. FIG. 4 is a cross-sectional view of a main part, enlarging a part of the cross section shown in FIG. 3, and is a cross-sectional view taken along line IV-IV of FIG. FIG. 5 is an enlarged cross-sectional view of a part of FIG. 4 . FIG. 6 is a flow chart showing a method of manufacturing a thermal printhead according to the embodiment. FIG. 7 is a cross-sectional view of a main part showing one step of the method of manufacturing the thermal print head according to the embodiment. FIG. 8 is a cross-sectional view of a main part showing one step of the method of manufacturing the thermal print head according to the embodiment. FIG. 9 is an enlarged cross-sectional view of a main part showing one step of the method of manufacturing the thermal print head according to the embodiment. FIG. 10 is a cross-sectional view of essential parts showing one step of the method for manufacturing the thermal print head according to the embodiment. FIG. 11 is a cross-sectional view of essential parts showing one step of the method for manufacturing the thermal print head according to the embodiment. FIG. 12 is a cross-sectional view of essential parts showing one step of the method for manufacturing the thermal print head according to the embodiment. FIG. 13 is a cross-sectional view of a main part showing one step of the method of manufacturing the thermal print head according to the embodiment; FIG. 14 is an enlarged cross-sectional view of a main part showing one step of the method of manufacturing the thermal print head according to the embodiment. FIG. 15 is a cross-sectional view of a main part showing one step of the method for manufacturing the thermal print head according to the embodiment; FIG. 16 is a cross-sectional view of a main part showing one step of the method for manufacturing the thermal print head according to the embodiment; FIG. 17 is a graph showing the correlation between the mixing ratio of the raw material gases used in the film forming process in the first layer forming step and the refractive index of the formed first layer. FIG. 18 is a graph showing the correlation between the flow rate of silane, which is the raw material gas used in the film forming process of the first layer forming step, and the refractive index of the formed first layer. FIG. 19 is an enlarged cross-sectional view of a main part showing a thermal print head according to a modification. FIG. 20 is an enlarged plan view of essential parts showing a thermal print head according to a modification. FIG. 21 is an enlarged plan view of a main part showing a thermal print head according to a modification. FIG. 22 is a fragmentary cross-sectional view showing a thermal print head according to a modification.

Preferred embodiments of a thermal printhead and a method for manufacturing a thermal printhead of the present disclosure will be described below with reference to the drawings. Below, the same reference numerals are given to the same or similar components, and overlapping descriptions are omitted. The terms "first", "second", "third", etc. in this disclosure are used merely as labels and are not necessarily intended to impose a permutation of the objects.

In the present disclosure, "a certain entity A is formed on a certain entity B" and "a certain entity A is formed on (of) a certain entity B" mean "a certain entity A is directly formed in a certain thing B", and "a certain thing A is formed in a certain thing B while another thing is interposed between a certain thing A and a certain thing B" including. Similarly, unless otherwise specified, ``a certain entity A is placed on a certain entity B'' and ``a certain entity A is placed on (of) a certain entity B'' mean ``a certain entity A being placed directly on a certain thing B", and "a thing A being placed on a certain thing B with another thing interposed between something A and something B" include. Similarly, unless otherwise specified, ``an object A is located on (of) an object B'' means ``a certain object A is in contact with an object B, and an object A is located on an object B. Being located on (of)" and "something A is located on (something) B while another thing is interposed between something A and something B including "things". In addition, unless otherwise specified, ``a certain object A overlaps an object B when viewed in a certain direction'' means ``a certain object A overlaps all of an object B'', and ``a certain object A overlaps an object B.'' It includes "overlapping a part of a certain thing B".

1 to 5 show a thermal print head A1 according to an embodiment. The thermal printhead A1 includes a head substrate 1, a protective layer 2, a wiring layer 3, a resistor layer 4, a connection substrate 5, a plurality of wires 61, a plurality of driver ICs 7, a protective resin 78 and a heat dissipation member 8.

For convenience of explanation, the thickness direction of the head substrate 1 is referred to as "thickness direction z". In the following description, one of the thickness directions z may be referred to as upward and the other as downward. The descriptions such as "upper", "lower", "upper", "lower", "upper surface" and "lower surface" indicate the relative positional relationship of each part, part, etc. in the thickness direction z. , is not necessarily a term that defines the relationship with the direction of gravity. Moreover, "planar view" refers to the time when viewed in the thickness direction z. Further, the main scanning direction of the thermal print head A1 is called "main scanning direction x", and the sub-scanning direction of the thermal print head A1 is called "sub-scanning direction y".

The thermal print head A1 is incorporated in a thermal printer Pr (see FIG. 3) that prints on a print medium (not shown). The thermal printer Pr includes a thermal printhead A1 and a platen roller 91. As shown in FIG. A platen roller 91 faces the thermal print head A1. A print medium is sandwiched between the thermal print head A1 and a platen roller 91 and transported in the sub-scanning direction y by the platen roller 91 . Such print media include, for example, thermal paper for creating barcode stickers and receipts. A flat rubber platen may be used instead of the platen roller 91 . The platen includes an arcuate portion of cylindrical rubber having a large radius of curvature when viewed in cross section. In this disclosure, the term "platen" includes both platen rollers 91 and flat platens.

A head substrate 1 supports a wiring layer 3 and a resistor layer 4 . The head substrate 1 has an elongated rectangular shape whose longitudinal direction is the main scanning direction x. Head substrate 1 includes base material 10 and insulating layer 19 .

Base material 10 is made of a single crystal semiconductor, and the single crystal semiconductor is, for example, silicon (Si). The substrate 10 has a first major surface 11 and a first back surface 12, as shown in FIGS. The first main surface 11 and the first back surface 12 are separated in the thickness direction z and face opposite sides in the thickness direction z. The wiring layer 3 and the resistor layer 4 are provided on the first main surface 11 side in the thickness direction z.

The base material 10 has protrusions 13 . As shown in FIGS. 4 and 5, the convex portion 13 protrudes from the first main surface 11 in the thickness direction z and extends long in the main scanning direction x. In the illustrated example, the convex portion 13 is arranged on the downstream side of the base material 10 in the sub-scanning direction y. Since the convex portion 13 is a part of the base material 10, it is made of silicon (Si), which is a single crystal semiconductor. As shown in FIG. 5, the convex portion 13 has a top portion 130, a pair of first inclined portions 131A and 131B, and a pair of second inclined portions 132A and 132B.

The apex 130 is a portion of the protrusion 13 that is the longest in the thickness direction z from the first main surface 11 . The top portion 130 is, for example, a surface substantially parallel to the first main surface 11 . The top portion 130 has an elongated rectangular shape elongated in the main scanning direction x when viewed in the thickness direction z.

The pair of first inclined portions 131A and 131B are connected to both sides of the top portion 130 in the sub-scanning direction y, as shown in FIG. The first inclined portion 131A is connected to the top portion 130 from the upstream side in the sub-scanning direction y. The first inclined portion 131B connects to the top portion 130 from the downstream side in the sub-scanning direction y. As shown in FIG. 5, each of the pair of first inclined portions 131A and 131B is inclined at an angle α1 with respect to the first main surface 11 (inclined at a first inclination angle α1). Each of the pair of first inclined portions 131A and 131B is an elongated rectangular plane elongated in the main scanning direction x when viewed in the thickness direction z. The convex portion 13 may have inclined portions (not shown) connected to the pair of first inclined portions 131A and 131B and adjacent to both ends of the top portion 130 in the main scanning direction x.

As shown in FIG. 5, the pair of second inclined portions 132A and 132B are connected to the pair of first inclined portions 131A and 131B from the side opposite to the top portion 130 in the sub-scanning direction y. The second inclined portion 132A is sandwiched between the first inclined portion 131A and the first main surface 11 in the sub-scanning direction y. The second inclined portion 132A connects to the first inclined portion 131A from the upstream side in the sub-scanning direction y, and connects to the first main surface 11 from the downstream side in the sub-scanning direction y. The second inclined portion 132B is sandwiched between the first inclined portion 131B and the first main surface 11 in the sub-scanning direction y. The second inclined portion 132B connects to the first inclined portion 131B from the downstream side in the sub-scanning direction y, and connects to the first main surface 11 from the upstream side in the sub-scanning direction y. As shown in FIG. 5, each of the pair of second inclined portions 132A and 132B is inclined at an angle α2 with respect to the first main surface 11 (inclined at a second inclination angle α2). Angle α2 is greater than angle α1. Each of the pair of second inclined portions 132A and 132B is an elongated rectangular plane elongated in the main scanning direction x when viewed in the thickness direction z. The pair of second inclined portions 132A and 132B are connected to the first main surface 11 respectively. The convex portion 13 may have inclined portions (not shown) connected to the pair of second inclined portions 132A and 132B and positioned outward in the main scanning direction x on both ends of the top portion 130 in the main scanning direction x. .

In the base material 10, the first main surface 11 is the (100) plane. In the convex portion 13 formed by the manufacturing method described below, the inclination angle α1 (see FIG. 5) of each of the first inclined portions 131A and 131B with respect to the first main surface 11 is, for example, 30.1 degrees. The inclination angle α2 (see FIG. 5) of each second inclined portion 132A, 132B with respect to 11 is, for example, 54.7 degrees.

The size of the head substrate 1 is not particularly limited, but an example is as follows. The thickness (dimension in thickness direction z) is 725 μm. This thickness is the dimension along the thickness direction z from the first back surface 12 to the top portion 130 . The z-dimension in the thickness direction of the convex portion 13 is 150 μm or more and 300 μm or less, and is 175 μm in one example. The x dimension in the main scanning direction is 50 mm or more and 150 mm or less. The y dimension in the sub-scanning direction is 2.0 mm or more and 5.0 mm or less.

The insulating layer 19 covers the first major surface 11 and the protrusions 13, as shown in FIGS. The insulating layer 19 is provided to more reliably insulate the first main surface 11 side of the base material 10 . The insulating layer 19 is made of an insulating material, and as the insulating material, for example, SiO ₂ (TEOS-SiO ₂ ), which is formed using TEOS (tetraethyl orthosilicate) as a raw material gas, is employed. Instead of TEOS-SiO ₂ , for example, silicon oxide or silicon nitride deposited by other methods may be employed. Although the thickness of the insulating layer 19 is not particularly limited, an example thereof is 5 μm or more and 15 μm or less (preferably 5 μm or more and 10 μm or less).

The resistor layer 4 is supported by the head substrate 1 and, as shown in FIGS. 4 and 5, supported by the substrate 10 via the insulating layer 19 . The resistor layer 4 has a plurality of heat generating portions 41 . For convenience of understanding, in FIG.

The plurality of heat generating units 41 locally heat the print medium by selectively energizing each of them. Each heat generating portion 41 is a region of the resistor layer 4 exposed from the wiring layer 3 . The plurality of heat generating portions 41 are arranged along the main scanning direction x and are separated from each other in the main scanning direction x. The shape of each heat generating portion 41 is not particularly limited, and is, for example, a rectangular shape with the sub-scanning direction y as the longitudinal direction when viewed in the thickness direction z. The resistor layer 4 is made of a material having higher resistance than the wiring layer 3 . TaN, for example, is used as a constituent material of the resistor layer 4, but instead of TaN, TaSiO ₂ , TiON, PolySi, Ta ₂ O ₅ , RuO ₂ , RuTiO, TaSiN, or the like may be used. The method of forming the resistor layer 4 is not particularly limited, but may be formed by, for example, a sputtering method, a CVD (Chemical Vapor Deposition) method, plating, or the like, and may be appropriately selected depending on the constituent materials employed. For example, when the constituent material of the resistor layer 4 is TaN, the resistor layer 4 is formed by a sputtering method. Although the thickness of the resistor layer 4 is not particularly limited, an example thereof is 0.02 μm or more and 0.1 μm or less (preferably about 0.08 μm).

Each heat generating portion 41 is arranged on the convex portion 13 . In the example shown in FIG. 5, each heat generating portion 41 is formed across the top portion 130 from the first inclined portion 131B. The upstream edge in the sub-scanning direction y of each heat generating portion 41 is positioned on the top portion 130, and the downstream edge in the sub-scanning direction y of each heat generating portion 41 is positioned on the first inclined portion 131B. Each heat generating portion 41 is not limited to the example shown in FIG. 5 as long as it is arranged on the convex portion 13 .

The wiring layer 3 constitutes a current-carrying path for energizing the plurality of heat-generating portions 41 . The wiring layer 3 is supported by the head substrate 1 and laminated on the resistor layer 4 as shown in FIGS. 4 and 5 in this embodiment.

The wiring layer 3 has a common electrode 31, a plurality of individual electrodes 32 and a plurality of relay electrodes 33, as shown in FIGS.

Each of the plurality of relay electrodes 33 includes two strip-shaped portions 331 and a connecting portion 332, as shown in FIG. The two strip-shaped portions 331 are strip-shaped extending in the sub-scanning direction y. The two band-shaped portions 331 are spaced apart in the main scanning direction x while being arranged substantially parallel to each other. Each of the two belt-shaped portions 331 is connected to the adjacent exothermic portion 41 . In the example shown in FIG. 2, each of the two band-shaped portions 331 is connected to each heat generating portion 41 from the downstream side in the sub-scanning direction y. Each dimension in the main scanning direction x of the two band-shaped portions 331 is substantially the same. The connecting portion 332 is positioned downstream in the sub-scanning direction y from the two band-shaped portions 331 . The connecting portion 332 connects to each of the two belt-shaped portions 331 . The connecting portion 332 has a strip shape extending in the main scanning direction x. The plurality of relay electrodes 33 are arranged at equal pitches in the main scanning direction x. Each of the plurality of relay electrodes 33 has a U shape with an opening directed upstream in the sub-scanning direction y, and corners bent at right angles. Each of the plurality of relay electrodes 33 is positioned downstream of the plurality of heat generating portions 41 in the sub-scanning direction y.

The common electrode 31 includes a plurality of straight portions 311, a plurality of branch portions 312, a plurality of strip portions 313 and a connecting portion 314, as shown in FIG. Each of the plurality of orthogonal portions 311 has a strip shape extending in the sub-scanning direction y. The plurality of orthogonal portions 311 are arranged at equal pitches in the sub-scanning direction y. A branching portion 312 and two belt-shaped portions 313 are provided on each tip side (downstream side in the sub-scanning direction y) of the plurality of orthogonal portions 311 . The two belt-shaped portions 313 are connected to adjacent heat generating portions 41 respectively. In the example shown in FIG. 2, each of the two band-shaped portions 313 is connected to the heat generating portion 41 from the upstream side in the sub-scanning direction y. The dimension of each band-shaped portion 313 in the main scanning direction x is substantially the same as the dimension of each band-shaped portion 331 in the main scanning direction x. Moreover, each band-shaped portion 313 overlaps each band-shaped portion 331 when viewed in the sub-scanning direction y. A plurality of branch portions 312 are connected to the tip of each straight portion 311 respectively. The straight portions 311 are connected to the ends of the plurality of branch portions 312 opposite to the ends connected to the two strip portions 313 in the sub-scanning direction y. Each of the two band-shaped portions 313 is connected to the heat generating portion 41 from the upstream side in the sub-scanning direction y. The connecting portion 314 is positioned on the base end side (upstream side in the sub-scanning direction y) of the plurality of orthogonal portions 311 and extends along the main scanning direction x. A plurality of direct portions 311 are connected to the connecting portion 314 respectively. The connecting portion 314 is connected to the connector 59 via the wire 61 and wiring of the connection board 5, and is applied with a driving voltage.

Each of the individual electrodes 32 has a reverse polarity with respect to the common electrode 31 . As shown in FIG. 2, the plurality of individual electrodes 32 are spaced apart in the main scanning direction x. Each of the plurality of individual electrodes 32 includes a band-shaped portion 321 and a pad portion 322, as shown in FIG. In each individual electrode 32 , the strip-shaped portion 321 has a strip-like shape extending in the sub-scanning direction y and is positioned upstream of the heat-generating portion 41 in the sub-scanning direction y. In the example shown in FIG. 2, the belt-shaped portion 321 is connected to the heat generating portion 41 on the tip side (downstream side in the sub-scanning direction y). The dimension of the belt-like portion 321 in the main scanning direction x is substantially the same as the dimension of each belt-like portion 331 in the main scanning direction x. In addition, the end portion of the band-shaped portion 321 on the downstream side in the sub-scanning direction y overlaps the band-shaped portion 331 when viewed in the sub-scanning direction y. In each individual electrode 32 , the pad portion 322 is provided at the upstream end portion of the strip portion 321 in the sub-scanning direction y. The pad section 322 is connected to one of the output pads 72 (described later) of the plurality of driver ICs 7 via the wire 61 .

In the thermal print head A1, each straight portion 311 of the common electrode 31 is sandwiched between strip portions 321 of two individual electrodes 32, as shown in FIG. The heat-generating portion 41 to which one of the two strip-shaped portions 331 of each relay electrode 33 is connected is connected to the common electrode 31, and the heat-generating portion 41 to which the other of the two strip-shaped portions 331 of the relay electrode 33 is connected is , to one of the plurality of individual electrodes 32 . Therefore, when each individual electrode 32 is energized, current flows through the heat generating portion 41 connected thereto and the heat generating portion 41 connected to the heat generating portion 41 via the relay electrode 33, and these heat generating portions 41 Fever. That is, the two heat generating portions 41 generate heat at the same time. In the thermal print head A1, when each heat generating portion 41 is energized, current flows through each heat generating portion 41 along the sub-scanning direction y.

As shown in FIGS. 5 and 6, the wiring layer 3 (common electrode 31, a plurality of individual electrodes 32 and a plurality of relay electrodes 33) is composed of a first conductor layer 301 and a second conductor layer laminated in the thickness direction z. 302.

The first conductor layer 301 is formed on the resistor layer 4, as shown in FIGS. The first conductor layer 301 is made of a material whose resistance per unit length in the sub-scanning direction y is lower than that of the resistor layer 4 and higher than that of the second conductor layer 302 . For example, the electrical conductivity of the first conductor layer 301 is, for example, 10 ^-6 to 10 ^-7 Ωm. Ti (titanium), for example, is used as a constituent material of the first conductor layer 301, but instead of Ti, Ta, Ga, Sn, PtIr, Pt, Tl (thallium), V (vanadium), Cr, or the like may be used. may be adopted. The method of forming the first conductor layer 301 is not particularly limited, but may be formed by, for example, a sputtering method, a CVD method, or plating, and may be appropriately selected depending on the constituent material employed. For example, when the constituent material of the first conductor layer 301 is Ti, the first conductor layer 301 is formed by a sputtering method. Although the thickness of the first conductor layer 301 is not particularly limited, an example thereof is 0.1 μm or more and 0.2 μm or less.

The second conductor layer 302 is formed on the first conductor layer 301, as shown in FIGS. The second conductor layer 302 partially covers the first conductor layer 301 . Therefore, the first conductor layer 301 has a portion exposed from the second conductor layer 302 . The second conductor layer 302 is made of a material whose resistance value per unit length in the sub-scanning direction y is lower than those of the resistor layer 4 and the first conductor layer 301 . For example, the electrical resistivity of the second conductor layer 302 is 10 ⁻⁷ Ωm or less. Preferably, the second conductor layer 302 is made of a material with higher thermal conductivity than the first conductor layer 301 . Cu alloy, Al, Al alloy, Au, Ag, Ni, W (tungsten), or the like may be used instead of Cu, for example, as the constituent material of the second conductor layer 302 . The method of forming the second conductor layer 302 is not particularly limited, but may be formed by, for example, a sputtering method, a CVD method, or plating, and may be appropriately selected depending on the constituent material employed. For example, when the constituent material of the second conductor layer 302 is Cu, the second conductor layer 302 is formed by a sputtering method. When the constituent material of the second conductor layer 302 is Au, Ag, or Ni, it is generally formed by plating. In this case, the second conductor layer 302 includes a seed layer (eg, Cu). You can stay. The second conductor layer 302 is thicker than the first conductor layer 301 . The thickness of the second conductor layer 302 depends on the material used, the value of the current flowing through the wiring layer 3, and the like. An example of the thickness of the second conductor layer 302 is 0.5 μm or more and 5 μm or less.

In the thermal print head A1, as can be understood from FIGS. 2 and 5, each strip-shaped portion 313 (common electrode 31), each strip-shaped portion 321 (each individual electrode 32), and each strip-shaped portion 331 (each relay electrode 33 ) connected to each heat generating portion 41 is constituted by the first conductor layer 301 exposed from the second conductor layer 302 . That is, each strip-shaped portion 313 (common electrode 31), each strip-shaped portion 321 (each individual electrode 32), and each strip-shaped portion 331 (each relay electrode 33) is a portion constituted only by the first conductor layer 301. and a portion where the first conductor layer 301 and the second conductor layer 302 are laminated. Unlike this configuration, the portion connected to each heat generating portion 41 may have a configuration in which the second conductor layer 302 is laminated on the first conductor layer 301 . That is, each strip-shaped portion 313 (common electrode 31), each strip-shaped portion 321 (each individual electrode 32), and each strip-shaped portion 331 (each relay electrode 33) are formed on the first conductor layer 301 in the entire formation range. and the second conductor layer 302 are laminated.

Protective layer 2 protects wiring layer 3 and resistor layer 4 . The protective layer 2 covers the wiring layer 3 and the resistor layer 4, as shown in FIGS. 1 and 2, the protective layer 2 is omitted. The protective layer 2 is the surface layer of the thermal print head A1. Protective layer 2 includes a first layer 21 and a second layer 22 .

The first layer 21 is the lower layer of the protective layer 2 . The first layer 21 is arranged closer to the head substrate 1 , the wiring layer 3 and the resistor layer 4 than the second layer 22 is. A first layer 21 covers the insulating layer 19 , the wiring layer 3 and the resistor layer 4 . The composition of the first layer 21 contains silicon element. The refractive index of the first layer 21 is higher than that _of silicon nitride ( _Si3N4 ) composed of silicon element and nitrogen element in a stoichiometric composition ratio, and is lower than that of intrinsic silicon (Si), which is an intrinsic semiconductor. . This silicon nitride (Si ₃ N ₄ ) is composed of silicon element and nitrogen element stoichiometrically in an ideal ratio, and is hereinafter referred to as "intrinsic silicon nitride". In intrinsic silicon nitride (Si ₃ N ₄ ), the stoichiometric composition ratio of nitrogen (N)/silicon (Si) is 1.33 (≈4/3). The refractive index of the first layer 21 of the present disclosure is, for example, 2.05 or more and 3.882 or less (preferably 2.2 or more and 3.882 or less). All numerical examples of refractive indices in this disclosure are for light with a wavelength of 632.8 nm. In the present embodiment, the first layer 21 is a compound of silicon element and nitrogen element, and contains more silicon element than the aforementioned intrinsic silicon nitride (Si ₃ N ₄ ). Hereinafter, a silicon nitride containing more silicon elements than intrinsic silicon nitride (Si ₃ N ₄ ) is referred to as a “silicon-rich nitride”. In the silicon-rich nitride, the stoichiometric composition ratio of nitrogen (N)/silicon (Si) is greater than 1.33 (≈4/3). In this embodiment, the first layer 21 is made of silicon-rich nitride, for example. Intrinsic silicon (Si) has a refractive index of 3.882, and in this configuration where the first layer 21 is a silicon-rich nitride, the refractive index of the first layer 21 is (2.05 or greater)3. Smaller than 882. In an example different from this embodiment, the first layer 21 may be made of intrinsic silicon. In this case, the refractive index of the first layer 21 is 3.882. The dimension of the first layer 21 in the thickness direction z is, for example, 1 μm or more and 10 μm or less (preferably 3.2 μm).

The second layer 22 is the upper layer in the protective layer 2 . A second layer 22 covers the first layer 21 . In the thermal print head A1, the print medium is pressed against the second layer 22 by the platen roller 91, as shown in FIG. The composition of second layer 22 is, for example, silicon carbide (SiC). The dimension of the second layer 22 in the thickness direction z is, for example, 1 μm or more and 10 μm or less (preferably 4.0 μm).

The protective layer 2 has a plurality of pad openings 29 as shown in FIG. Each pad opening 29 penetrates the protective layer 2 (the first layer 21 and the second layer 22) in the thickness direction z. Each of the plurality of pad openings 29 exposes the pad portion 322 of each individual electrode 32 . Unlike the illustrated example, a plurality of pad openings 29 may be filled with a conductive material. In this case, a plating layer may be formed on this conductive material. The structure of this plating layer is not particularly limited, but as an example, Ni, Pd (palladium), and Au are laminated in this order from the surface of the conductive material.

The connection board 5 is arranged on the upstream side in the sub-scanning direction y with respect to the head board 1, as shown in FIGS. The connection board 5 is, for example, a PCB board, and each driver IC 7 and a connector 59 (described later) are mounted thereon. The shape of the connection board 5 is not particularly limited, but in the present embodiment, the connection board 5 has a rectangular shape whose longitudinal direction is the main scanning direction x. The connection substrate 5 has a second main surface 51 and a second rear surface 52, as shown in FIG. The second main surface 51 faces the same side as the first main surface 11 of the substrate 10 , and the second rear surface 52 faces the same side as the first rear surface 12 of the substrate 10 . In the present embodiment, the second main surface 51 is positioned below the first main surface 11 in the thickness direction z in the figure.

A plurality of control electrodes 55 are formed on the connection substrate 5 as shown in FIG. Each control electrode 55 is arranged on the second main surface 51 and is arranged upstream of the driver IC 7 in the sub-scanning direction y. Each control electrode 55 extends along the sub-scanning direction y. Each control electrode 55 is connected to one of input pads 71 (described later) of the driver IC 7 via a wire 61 and connected to a connector 59 via wiring of the connection substrate 5 .

Each of the plurality of driver ICs 7 is for supplying a current individually to the heat generating portions 41 to generate heat in order to selectively drive the plurality of heat generating portions 41 . The number of driver ICs 7 is appropriately changed according to the number of heat generating portions 41 . The energization control of each driver IC 7 follows a command signal input from outside the thermal print head A 1 via the connector 59 , the wiring of the connection substrate 5 and the control electrode 55 . Each driver IC 7 is mounted on the second main surface 51 of the connection substrate 5 and connected to the plurality of individual electrodes 32 and the plurality of control electrodes 55 via a plurality of wires 61 .

A plurality of input pads 71 and a plurality of output pads 72 are arranged on the upper surface of each driver IC 7, as shown in FIG. A plurality of input pads 71 are terminals to which various signals for controlling each driver IC 7 are input. The plurality of input pads 71 are arranged on the upper surface of each driver IC 7 near the end on the upstream side in the sub-scanning direction y. Each input pad 71 is connected to each control electrode 55 via each wire 61 . The plurality of output pads 72 are terminals through which a current for driving the heating portion 41 flows. The plurality of output pads 72 are arranged on the upper surface of each driver IC 7 near the end on the downstream side in the sub-scanning direction y. Each output pad 72 is connected to the pad portion 322 of each individual electrode 32 via each wire 61 .

A protective resin 78 covers the plurality of driver ICs 7 and the plurality of wires 61 . The protective resin 78 is made of, for example, an insulating resin and is black, for example. The protective resin 78 is formed across the head substrate 1 and the connection substrate 5, as shown in FIGS.

A connector 59 is used to connect the thermal print head A1 to the thermal printer Pr. The connector 59 is attached to the connection substrate 5 and connected to the input pads 71 of the driver IC 7 via the wiring pattern (not shown) of the connection substrate 5 and the control electrodes 55 .

The heat radiating member 8 supports the head substrate 1 and the connection substrate 5 and is for radiating part of the heat generated by the plurality of heat generating portions 41 to the outside through the head substrate 1 . The heat radiating member 8 is a block-shaped member made of metal such as Al (aluminum). The heat dissipation member 8 has a first support surface 81 and a second support surface 82, as shown in FIG. Each of the first support surface 81 and the second support surface 82 faces upward in the thickness direction z. The first support surface 81 is located downstream of the second support surface 82 in the sub-scanning direction y. As shown in FIG. 3 , the first rear surface 12 of the base material 10 is bonded to the first support surface 81 , and the second rear surface 52 of the connection board 5 is bonded to the second support surface 82 .

Next, an example of a method for manufacturing the thermal print head A1 will be described with reference to FIGS. 6 to 16. FIG. FIG. 6 is a flow chart showing an example of a method for manufacturing the thermal print head A1. 7, 8, 10 to 13, 15 and 16 are cross-sectional views of essential parts showing one step of the method of manufacturing the thermal print head A1, and correspond to FIG. 9 and 14 are enlarged cross-sectional views of essential parts showing one step of the method of manufacturing the thermal print head A1, and correspond to the cross-section of FIG.

As shown in FIG. 6, the method for manufacturing the thermal printhead A1 includes a substrate preparation step S11, a substrate processing step S12, an insulating layer forming step S13, a resistor film forming step S14, a wiring film forming step S15, and a removing step S16. , a protective layer forming step S17, a singulation step S181, and an assembly step S182.

[Base material preparation step S11]
First, as shown in FIG. 7, a base material 10K is prepared. The base material 10K is made of a single crystal semiconductor and is, for example, part of a Si wafer. A single Si wafer includes a plurality of substrates 10K. In the following figures, one substrate 10K (head substrate 1), which is part of the Si wafer and corresponds to one thermal print head A1, is illustrated. Although the thickness of the base material 10K (in other words, the thickness of the Si wafer) is not particularly limited, it is, for example, about 725 μm in this embodiment. As shown in FIG. 7, the base material 10K has a main surface 11K and a back surface 12K facing opposite sides. The main surface 11K is the (100) plane.

[Base material processing step S12]
Next, as shown in FIGS. 8 and 9, the base material 10K is processed to form the projections 13 on the base material 10K. In the base material processing step S12, etching is performed twice.

In the first etching, after the main surface 11K is covered with a predetermined mask layer, anisotropic etching is performed using KOH (potassium hydroxide), for example. Although TMAH (tetramethylammonium hydroxide) may be used instead of KOH as a chemical for this anisotropic etching, the processing speed (etching speed) is faster when KOH is used. After that, the mask layer is removed. As a result, as shown in FIG. 8, a convex portion 13K is formed on the base material 10K. The convex portion 13K protrudes from the main surface 11K and extends long in the main scanning direction x. The convex portion 13K has a top portion 130K and a pair of inclined portions 132K. The top portion 130K is a plane parallel to the main surface 11K and is the same (100) plane as the main surface 11K. The top portion 130K is the portion that was covered with the mask layer. The pair of inclined portions 132K are located on both sides of the top portion 130K in the sub-scanning direction y, and are interposed between the top portion 130K and the main surface 11K. Each of the pair of inclined portions 132K is a plane inclined with respect to the top portion 130K and the main surface 11K. The angle formed by each of the pair of inclined portions 132K, the main surface 11K and the top portion 130K is 54.7 degrees.

The second etching is anisotropic etching using TMAH, for example. The chemical used in this anisotropic etching may be KOH instead of TMAH, but the surface formed by etching (for example, a pair of first inclined portions 131A and 131B described later) is smoother when TMAH is used. become a good side. As a result of this anisotropic etching, the base material 10K becomes the base material 10 having the first principal surface 11, the first back surface 12, and the projections 13, as shown in FIG. The convex portion 13 has a top portion 130, a pair of first inclined portions 131A and 131B, and a pair of second inclined portions 132A and 132B. The top portion 130 is the portion that was the top portion 130K, and the pair of second inclined portions 132A and 132B are the portions that were the pair of inclined portions 132K. The pair of first inclined portions 131A and 131B are portions where the boundary between the top portion 130K and the pair of inclined portions 132K is etched by TMAH. The angle α1 (see FIG. 9) of each of the first inclined portions 131A and 131B with respect to the first main surface 11 is 30.1 degrees, and the angle α2 of each of the second inclined portions 132A and 132B with respect to the first main surface 11 (see FIG. 9) is 54.7 degrees.

[Insulating layer forming step S13]
Next, as shown in FIG. 10, an insulating layer 19 is formed. The insulating layer 19 is formed by depositing SiO ₂ formed using TEOS as a source gas on the substrate 10 using, for example, CVD. The method for forming the insulating layer 19 is not limited to this. The formed insulating layer 19 covers the entire surface of the first main surface 11 and the protrusions 13 . Thus, the head substrate 1 including the base material 10 and the insulating layer 19 is formed.

[Resistor Film Forming Step S14]
Next, as shown in FIG. 11, a resistor film 4K is formed. In the resistor film forming step S14, a TaN thin film is formed on the insulating layer 19 by sputtering, for example. The method of forming the resistor film 4K is not limited to this. The resistor film 4K is formed so as to cover substantially the entire surface of the insulating layer 19. As shown in FIG.

[Wiring film forming step S15]
Next, as shown in FIGS. 12 and 13, a wiring film 3K is formed. The wiring film forming step S15 includes a first film forming process S151 and a second film forming process S152.

In the first film forming process S151, as shown in FIG. 12, a first conductor film 301K is formed on the resistor film 4K. The first conductor film 301K is formed by sputtering, for example. The first conductor film 301K is a thin film made of Ti, for example. At this time, the first conductor film 301K covers substantially the entire surface of the resistor film 4K.

In the second film forming process S152, as shown in FIG. 13, the second conductor film 302K is formed on the first conductor film 301K. The second conductor film 302K is formed by, for example, plating or sputtering. The second conductor film 302K is made of Cu, for example. At this time, the second conductor film 302K covers substantially the entire surface of the first conductor film 301K.

[Removal step S16]
Next, the second conductor film 302K, the first conductor film 301K and the resistor film 4K are partially removed as appropriate to form the wiring layer 3 and the resistor layer 4 as shown in FIG. As shown in FIG. 6, the removal step S16 has a first partial removal process S161, a second partial removal process S162, and a third partial removal process S163.

In the first partial removal process S161, the second conductor film 302K is partially removed. In the second partial removal process S162, the first conductor film 301K is partially removed. In the third partial removal process S163, partial removal of the resistor film 4K is performed. The first partial removal processing S161, the second partial removal processing S162, and the third partial removal processing S163 are each performed by etching, for example. The second conductor layer 302 is formed by the first partial removal process S161, the first conductor layer 301 is formed by the second partial removal process S162, and the resistor layer 4 is formed by the third partial removal process S163. . The third partial removal process S163 may be performed before the first partial removal process S161 and the second partial removal process S162. The formed first conductor layer 301 and second conductor layer 302 constitute the wiring layer 3 , and the wiring layer 3 has a common electrode 31 , a plurality of individual electrodes 32 and a plurality of relay electrodes 33 . The formed resistor layer 4 has a plurality of heat generating portions 41 and is divided into each heat generating portion 41 .

[Protective layer forming step S17]
Next, protective layer 2 is formed to cover wiring layer 3 and resistor layer 4 . As shown in FIG. 6, the protective layer forming step S17 includes a first layer forming step S171, a second layer forming step S172, and a partial removal step S173.

In the first layer forming step S171, as shown in FIG. 15, the first layer 21 is formed over the entire upper surface of the substrate 10 in the thickness direction z. In the first layer forming step S171, a film forming process is performed using a raw material gas containing ammonia ( _NH3 ) and silane ( _SiH4 ). The film forming process is plasma CVD, for example. The aforementioned source gas has a ratio (NH ₃ /SiH ₄ ) between ammonia (NH ₃ ) and silane (SiH ₄ ) of 0.1 or more and 4 or less. The ratio (NH ₃ /SiH ₄ ) between ammonia (NH ₃ ) and silane (SiH ₄ ) in the raw material gas is sometimes referred to as "mixing ratio". In addition to ammonia (NH ₃ ) and silane (SiH ₄ ), the raw material gas also contains nitrogen (N ₂ ). Also, the temperature of the film forming chamber of the plasma CVD apparatus is 320° C. or higher and 420° C. or lower (for example, 400° C.). Through such a film forming process, a silicon-rich nitride having a refractive index higher than that of intrinsic silicon nitride and lower than that of intrinsic silicon is formed as the first layer 21 . The film forming process performed in the first layer forming step S171 may be thermal CVD instead of plasma CVD.

In the second layer forming step S172, as shown in FIG. 16, the second layer 22 covering the first layer 21 is formed. In the second layer forming step S172, a silicon carbide (SiC) thin film is deposited on the first layer 21 by sputtering, for example. Formation of the second layer 22 is not limited to sputtering.

In the partial removal step S173, the first layer 21 and the second layer 22 are partially removed to form the pad opening 29 penetrating the first layer 21 and the second layer 22 in the thickness direction z. In the partial removal step S173, for example, after lithography patterning is applied to the first layer 21 and the second layer 22, a part of the first layer 21 and the second layer 22 is removed. The removal is performed, for example, by reactive ion etching. As a result, portions of the individual electrodes 32 (pad portions 322 ) are exposed from the pad openings 29 . Note that in the formation of the first layer 21 in the first layer forming step S171 and the formation of the second layer 22 in the second layer forming step S172, these forming ranges are adjusted, and when the pad opening 29 is formed, , the partial removal step S173 may not be performed.

[Singulation step S181]
Next, the substrate 10 is appropriately divided into each head substrate 1 . It should be noted that if the substrate 10 corresponding to one head substrate 1 has been prepared in the substrate preparation step S11, the singulation step S181 may not be performed. For the singulation step S181, laser dicing, blade dicing, or the like is selected according to the material of the substrate 10, for example. In this embodiment, the singulation step S181 is performed by blade dicing.

[Assembly step S182]
Thereafter, the head substrate 1 and the connection substrate 5 are attached to the heat dissipation member 8, the driver IC 7 is mounted, the plurality of wires 61 are bonded, and the protective resin 78 is formed. Through the steps shown in FIG. 6, the thermal print head A1 shown in FIGS. 1 to 5 is manufactured.

The method for manufacturing the thermal print head A1 described above is an example, and the present invention is not limited to this. For example, in the first layer forming step S171, an example of forming the first layer 21 made of silicon-rich nitride has been described, but unlike this example, the first layer 21 made of intrinsic silicon is formed. good too. A film of intrinsic silicon in this case may be formed using a well-known film forming technique.

The functions and effects of the thermal print head A1 and the method for manufacturing the thermal print head A1 are as follows.

The thermal print head A1 includes a protective layer 2 that covers the wiring layer 3 and the resistor layer 4 (the plurality of heat generating portions 41). The protective layer 2 includes a first layer 21 containing elemental silicon. The refractive index of the first layer 21 is higher than the refractive index of intrinsic silicon nitride (silicon nitride Si ₃ N ₄ composed of silicon element and nitrogen element in a stoichiometric composition ratio). is less than or equal to the refractive index of In the thermal print head described in Patent Document 1, the wear-resistant protective layer corresponding to the protective layer 2 of the thermal print head A1 of the present disclosure is made of silicon oxide (SiO ₂ ), for example. The refractive index of this silicon oxide (SiO ₂ ) is smaller than that of intrinsic silicon nitride. That is, the refractive index of the first layer 21 of the thermal printhead A1 is higher than that of intrinsic silicon nitride ( _Si3N4 ), and the refractive index of silicon oxide ( _SiO2 ) is higher than that of intrinsic silicon nitride ( _Si3N4 ). Si ₃ N ₄ ). Therefore, the refractive index of the first layer 21 is higher than that of silicon oxide (SiO ₂ ). According to research by the inventor of the present application, it was found that there is a correlation between the refractive index and the thermal conductivity, and that the thermal conductivity increases as the refractive index increases. For example, silicon oxide (SiO ₂ ) has a thermal conductivity of 1.38 W/mK, intrinsic silicon nitride (Si ₃ N ₄ ) has a thermal conductivity of 27 W/mK, and intrinsic silicon (Si) has a thermal conductivity of 27 W/mK. The thermal conductivity of is 168 W/mK, so there is a correlation that the larger the refractive index, the larger the thermal conductivity. Therefore, the first layer 21 of the present disclosure has a higher thermal conductivity than when composed of silicon oxide (SiO ₂ ). As a result, in the thermal print head A1, the thermal conductivity of the first layer 21 is higher than that of the conventional thermal print head (described in Patent Document 1), so that the heat generated by each heat generating portion 41 is efficiently transferred to the print medium. can be transmitted to That is, the thermal print head A1 can improve the printing efficiency.

In the thermal print head A1, the refractive index of the first layer 21 is 2.05 or more and 3.882 or less. The refractive index of intrinsic silicon nitride (Si ₃ N ₄ ) is, for example, 2.023, and the refractive index of intrinsic silicon (Si) is, for example, 3.882. The refractive index of silicon oxide (SiO ₂ ) is, for example, 1.457. Therefore, by setting the refractive index of the first layer 21 within the above numerical range, the refractive index of the first layer 21 is higher than the refractive index of intrinsic silicon nitride and equal to or lower than the refractive index of intrinsic silicon. That is, the thermal print head A1 can improve the thermal conductivity of the first layer 21 by setting the refractive index of the first layer 21 to 2.05 or more and 3.882 or less. As a result, the thermal print head A1 can efficiently transmit the heat generated by each heat generating portion 41 to the print medium, thereby improving the printing efficiency.

In the thermal print head A1, the first layer 21 is a compound of silicon element and nitrogen element, and contains more silicon element than intrinsic silicon nitride (Si ₃ N ₄ ). That is, the first layer 21 is composed of silicon-rich nitride. According to research by the inventors of the present application, it was found that the refractive index increases as the content of silicon in silicon nitride increases. Therefore, in the thermal print head A1, by forming the first layer 21 of silicon-rich nitride, the refractive index can be made larger than that of intrinsic silicon nitride (Si ₃ N ₄ ). It has a higher thermal conductivity than silicon nitride (Si ₃ N ₄ ). That is, the thermal print head A1 can improve the thermal conductivity of the first layer 21 more than when _the first layer 21 is made of intrinsic silicon nitride ( _Si3N4 ). As a result, the thermal print head A1 can efficiently transfer the heat generated by the heat generating portions 41 to the print medium, thereby improving the printing efficiency.

In thermal printhead A1, the first layer 21 is composed of silicon-rich nitride. Since the refractive index of intrinsic silicon (Si) is 3.882, in this configuration, the refractive index of the first layer 21 is (2.05 or more) less than 3.882. In the thermal print head A1, even if the first layer 21 is composed of intrinsic silicon and the refractive index of the first layer 21 is 3.882, the thermal conductivity of the first layer 21 is improved as described above, and the printing efficiency is improved. can be improved. Silicon-rich nitrides, on the other hand, are more moisture tolerant than intrinsic silicon (Si). That is, the thermal print head A1 can improve the moisture resistance by forming the first layer 21 of silicon-rich nitride, compared to the case where the first layer 21 is formed of intrinsic silicon (Si). As a result, the thermal print head A1 can improve the humidity resistance while improving the printing efficiency.

In the thermal printhead A1, the protective layer 2 further comprises a second layer 22 covering the first layer 21. As shown in FIG. The second layer 22 is made of silicon carbide (SiC), for example. The second layer 22 made of silicon carbide has a higher thermal conductivity and a higher Vickers hardness than the first layer 21 made of silicon nitride. Therefore, the thermal print head A1 can effectively suppress abrasion of the protective layer 2 due to transport of the print medium while improving printing efficiency.

The method for manufacturing the thermal print head A1 includes a step of forming the protective layer 2 (protective layer forming step S17). The protective layer forming step S17 includes a step of forming the first layer 21 containing silicon element. In the step of forming the first layer 21, a raw material gas containing ammonia (NH ₃ ) and silane (SiH ₄ ) is used. A film formation process to be used is performed. In the raw material gas used in this film forming process, the ratio (NH ₃ /SiH ₄ ) between ammonia (NH ₃ ) and silane (SiH ₄ ) is 0.1 or more and 4 or less. In such a manufacturing method, as the first layer 21 of _the protective layer 2, a silicon-rich nitride having a higher content of silicon element than intrinsic silicon nitride ( _Si3N4 ) is formed. Therefore, according to the method for manufacturing the thermal print head A1, the first layer 21 made of silicon-rich nitride can be formed, so that the thermal conductivity of the first layer 21 is improved as described above. That is, the method for manufacturing the thermal print head A1 can manufacture the thermal print head A1 with improved printing efficiency.

Further, the refractive index of the first layer 21 to be formed has the correlation shown in FIG. 17, for example, with respect to the ratio (mixing ratio) of ammonia (NH ₃ ) and silane (SiH ₄ ). In the graph shown in FIG. 17, the horizontal axis represents the mixing ratio, and the vertical axis represents the refractive index. As shown in FIG _. 17, the refractive index of the first layer ₂₁ changes according to the mixing ratio. becomes smaller. That is, the greater the amount of silane (SiH ₄ ) relative to the amount of ammonia (NH ₃ ), the greater the refractive index of the silicon nitride formed. Based on the correlation shown in FIG. 17, the ratio (NH ₃ /SiH ₄ ) between ammonia (NH ₃ ) and silane (SiH ₄ ) in the raw material gas in the film forming process of the first layer forming step S171 is determined. is 0.1 or more and 4 or less, the refractive index of the first layer 21 (silicon-rich nitride) can be made greater than the refractive index of intrinsic silicon nitride and less than or equal to that of intrinsic silicon. Therefore, the method for manufacturing the thermal print head A1 can manufacture the thermal print head A1 with improved printing efficiency.

In the method for manufacturing the thermal printhead A1, in the film forming process of the first layer forming step S171, the flow rate of silane (SiH ₄ ) is higher than the flow rate when forming the intrinsic silicon nitride (Si ₃ N ₄ ). . According to this configuration, a silicon-rich nitride can be formed as the first layer 21, and the refractive index can be improved. The refractive index of the formed first layer 21 has the correlation shown in FIG. 18, for example, with respect to the flow rate of silane (SiH ₄ ) in the film forming process of the first layer forming step S171. Note that FIG. 18 shows the correlation when the flow rate of ammonia (NH ₃ ) is 4000 sccm. In the graph shown in FIG. 18, the horizontal axis represents the flow rate of silane (SiH ₄ ), and the vertical axis represents the refractive index. As shown in FIG. 18, as the flow rate of silane (SiH ₄ ) increases, the refractive index of the first layer 21 increases. This is because the higher the flow rate of silane (SiH ₄ ), the higher the content of silicon element in the formed first layer 21 (silicon-rich nitride). Therefore, in the film forming process of the first layer forming step S171, the flow rate of silane (SiH ₄ ) is set higher than the flow rate for forming the intrinsic silicon nitride (Si ₃ N ₄ ), thereby forming The thermal conductivity can be improved by increasing the refractive index of silicon nitride (first layer 21). That is, the method for manufacturing the thermal print head A1 can manufacture the thermal print head A1 with improved printing efficiency.

In the thermal print head A1 of the above embodiment, even if the convex portion 13 does not have the pair of first inclined portions 131A and 131B, and has the top portion 130 and the pair of second inclined portions 132A and 132B, good. In this case, the top portion 130 and the pair of second inclined portions 132A and 132B are in direct contact with each other. Further, in the thermal print head A1 of the above embodiment, the substrate 10 does not have to have the protrusions 13 .

In the thermal printhead A1 of the above-described embodiment, the protective layer 2 may not include the second layer 22 and may be composed only of the first layer 21 as shown in FIG. 19, for example. FIG. 19 is a fragmentary cross-sectional view showing a thermal printhead in a modified example, showing an example in which the protective layer 2 does not include the second layer 22 . In the thermal print head shown in FIG. 19, similarly to the thermal print head A1, the heat generated by each heat generating portion 41 can be efficiently transferred to the print medium, and the printing efficiency can be improved. However, as described above, the protective layer 2 preferably has the second layer 22 formed on the first layer 21 in order to suppress abrasion of the protective layer 2 .

In the thermal print head A1 of the above embodiment, the configuration of the wiring layer 3 is not limited to the illustrated example. 20 and 21 are respectively enlarged plan views of the main part of the thermal printhead according to the modification, showing an example in which the wiring layer 3 has a different structure.

FIG. 20 shows an example of a thermal print head according to a modification, and the enlarged plan view of the essential part of FIG. 20 corresponds to FIG. In the modification shown in FIG. 20, the wiring layer 3 has a common electrode 31 and a plurality of individual electrodes 32 like the wiring layer 3 of the thermal print head A1, but unlike the wiring layer 3 of the thermal print head A1, a plurality of does not have any relay electrode 33.

In the example shown in FIG. 20 , the common electrode 31 includes a plurality of band-shaped portions 313 , connecting portions 314 and detour portions 315 . The connecting portion 314 is arranged near the edge of the head substrate 1 on the downstream side in the sub-scanning direction y. The connecting portion 314 has a belt-like shape extending in the main scanning direction x. The plurality of belt-like portions 313 each extend in the sub-scanning direction y from the connecting portion 314 toward each heat generating portion 41 . The plurality of band-shaped portions 313 are arranged at equal pitches in the main scanning direction x. The detour portion 315 extends in the sub-scanning direction y from one end of the connecting portion 314 in the main scanning direction x.

In the example shown in FIG. 20, each heat generating portion 41 is sandwiched between each strip-shaped portion 313 of the common electrode 31 and the strip-shaped portion 321 of each individual electrode 32 in the sub-scanning direction y. Each band-shaped portion 321 is connected to each heat-generating portion 41 from the upstream side in the sub-scanning direction y, and each band-shaped portion 313 is connected to each heat-generating portion 41 from the downstream side in the sub-scanning direction y.

FIG. 21 shows another example of the thermal printhead according to the modification. In the example shown in FIG. 21, the wiring layer 3 has a common electrode 31 and a plurality of individual electrodes 32, but does not have a plurality of relay electrodes 33, as in the modification shown in FIG.

In the example shown in FIG. 21, each band-shaped portion 313 and each band-shaped portion 321 are alternately arranged along the main scanning direction x. The resistor layer 4 is formed in a strip shape extending in the main scanning direction x so as to overlap the strip portions 313 and the strip portions 321 . In such a configuration, as shown in FIG. 21, when viewed in the thickness direction z, each heat generating portion 41 is a region sandwiched between each band-shaped portion 313 and each band-shaped portion 321 in the main scanning direction x.

In addition, in the example shown in FIG. 21, the resistor layer 4 is arranged below the wiring layer 3 in the thickness direction z in the portion where the wiring layer 3 and the resistor layer 4 overlap when viewed in the thickness direction z. . Unlike this configuration, the resistor layer 4 may be arranged above the wiring layer 3 in the thickness direction z.

The thermal print heads shown in FIGS. 20 and 21 also have the same effect as the thermal print head A1. Therefore, in the thermal print head of the present disclosure, as can be understood from the modified examples shown in FIGS. 20 and 21, the configuration of the wiring layer 3 can be appropriately changed according to the specifications of the thermal print head.

In the thermal print head A1 of the above embodiment, the substrate 10 is not limited to being made of a single crystal semiconductor, and may be made of ceramics, for example. FIG. 22 is a fragmentary cross-sectional view showing a thermal printhead according to a modification, showing an example in which the base material 10 is made of ceramics. Although the protective layer 2 includes only the first layer 21 in the example shown in FIG. 22, it may be configured to include the first layer 21 and the second layer 22 similarly to the thermal print head A1. In the example shown in FIG. 22, the resistor layer 4 is arranged above the wiring layer 3 in the thickness direction z in the portion where the wiring layer 3 and the resistor layer 4 overlap when viewed in the thickness direction z.

In the example shown in FIG. 22, head substrate 1 includes substrate 10 and glaze layer 15 . The base material 10 is made of ceramics, as described above. As the ceramics, those having relatively high thermal conductivity such as AlN (aluminum nitride) and Al ₂ O ₃ (alumina) can be used. The glaze layer 15 is formed on the first major surface 11 of the substrate 10 . The glaze layer 15 is made of a glass material such as amorphous glass. As shown in FIG. 22, glaze layer 15 includes partial glaze 151 and glass layer 152 . Unlike the example shown in FIG. 22, the glaze layer 15 may be composed of only the partial glaze 151 without including the glass layer 152 . Alternatively, the head substrate 1 may not include the glaze layer 15 .

The partial glaze 151 extends long in the main scanning direction x. The partial glaze 151 bulges in the thickness direction z when viewed in the main scanning direction x. As shown in FIG. 22, the partial glaze 151 has an arcuate cross section (yz cross section) taken along a plane perpendicular to the main scanning direction x. The partial glaze 151 is provided in order to make it easier to press a heat-generating portion (heat-generating portion 41, which will be described later) of the resistor layer 4 against a print medium. Further, the partial glaze 151 is provided as a heat storage layer that stores heat from the heat generating portion 41 . The partial glaze 151 has a dimension (maximum dimension) in the thickness direction z larger than that of the glass layer 152 . The glass layer 152 is formed adjacent to the partial glaze 151 and has a flat upper surface. The glass layer 152 partially overlaps the partial glaze 151 .

The thermal print head shown in FIG. 22 also has the same effect as the thermal print head A1. Therefore, in the thermal printhead of the present disclosure, as can be understood from the modification shown in FIG. 22, the configuration of the head substrate 1 can be appropriately changed according to the specifications of the thermal printhead.

The thermal printhead and the method of manufacturing the thermal printhead according to the present disclosure are not limited to the above-described embodiments. The specific configuration of each part of the thermal print head of the present disclosure and the specific processing of each step of the method of manufacturing the thermal print head of the present disclosure can be designed and changed in various ways. For example, the thermal printhead and thermal printhead manufacturing method of the present disclosure include embodiments relating to the following notes.
[Appendix 1]
a substrate;
a resistor layer having a plurality of heat generating portions arranged in the main scanning direction and supported by the substrate;
a wiring layer that constitutes a current path to the plurality of heat generating parts and is supported by the substrate;
a protective layer covering the resistor layer and the wiring layer;
with
The protective layer includes a first layer containing silicon element,
The refractive index of the first layer is higher than the refractive index of silicon nitride composed of silicon element and nitrogen element in a stoichiometric composition ratio, and is lower than or equal to the refractive index of intrinsic silicon, which is an intrinsic semiconductor. Thermal printing. head.
[Appendix 2]
The thermal printhead according to appendix 1, wherein the first layer has a refractive index of 2.05 or more and 3.882 or less.
[Appendix 3]
3. The thermal printhead of Claim 2, wherein the refractive index of the first layer is less than 3.882.
[Appendix 4]
3. The thermal printhead according to appendix 3, wherein the first layer is a compound of elemental silicon and elemental nitrogen, and the content of silicon element is higher than that of silicon nitride having the stoichiometric composition ratio.
[Appendix 5]
5. The thermal printhead according to any one of Appendices 1 to 4, wherein the protective layer further includes a second layer covering the first layer.
[Appendix 6]
6. The thermal printhead of clause 5, wherein the second layer is silicon carbide.
[Appendix 7]
7. The thermal printhead according to any one of appendices 1 to 6, wherein the substrate includes a base material composed of a single crystal semiconductor.
[Appendix 8]
8. The thermal printhead of Claim 7, wherein the substrate further comprises an insulating layer sandwiched between the substrate and the resistor layer.
[Appendix 9]
The resistor layer is formed on the insulating layer while exposing a portion of the insulating layer,
The wiring layer is formed on the resistor layer while exposing the plurality of heat generating portions,
9. The thermal printhead according to appendix 8, wherein the protective layer is formed on the wiring layer.
[Appendix 10]
The wiring layer comprises: a first conductor layer laminated on the resistor layer while exposing a part of the resistor layer; a laminated second conductor layer;
the second conductor layer has a resistance value per unit length in the sub-scanning direction that is lower than that of each of the plurality of heat generating portions;
9. The thermal printhead according to appendix 9, wherein the first conductor layer has a resistance value per unit length in the sub-scanning direction between each of the plurality of heat generating portions and the second conductor layer.
[Appendix 11]
The constituent material of the first conductor layer contains Ti,
11. The thermal printhead according to appendix 10, wherein the constituent material of the second conductor layer contains Cu.
[Appendix 12]
the base material has a main surface facing the resistor layer and a convex portion projecting from the main surface and extending in the main scanning direction;
12. The thermal printhead according to any one of appendices 7 to 11, wherein each of the plurality of heat generating portions is formed on the convex portion.
[Appendix 13]
13. The thermal printhead according to any one of appendices 7 to 12, wherein the single crystal semiconductor is silicon.
[Appendix 14]
preparing a substrate;
a step of forming a resistor layer having a plurality of heat generating portions arranged in the main scanning direction and supported by the substrate;
A step of forming a wiring layer supported by the base material by configuring an energization path to the plurality of heat generating parts;
forming a protective layer covering the resistor layer and the wiring layer;
including
forming the protective layer includes forming a first layer containing silicon element;
In the step of forming the first layer, a film formation process is performed using a raw material gas containing ammonia (NH ₃ ) and silane (SiH ₄ ),
A method for manufacturing a thermal print head, wherein a ratio (NH ₃ /SiH ₄ ) of ammonia (NH ₃ ) and silane (SiH ₄ ) in the raw material gas is 0.1 or more and 4 or less.
[Appendix 15]
15. The method of manufacturing a thermal print head according to appendix 14, wherein the film forming process is performed by plasma CVD.

Pr: Thermal printer A1: Thermal print head 1: Head substrate 10, 10K: Base material 11: First main surface 11K: Main surface 12: First back surface 12K: Back surface 13, 13K: Convex portions 130, 130K: Top portion 131A, 131B: first inclined portions 132A, 132B: second inclined portion 132K: inclined portion 15: glaze layer 151: partial glaze 152: glass layer 19: insulating layer 2: protective layer 21: first layer 22: second layer 29: Pad opening 3 : Wiring layer 3K : Wiring film 301 : First conductor layer 301K : First conductor film 302 : Second conductor layer 302K : Second conductor film 31 : Common electrode 311 : Straight part 312 : Branch part 313 : Strip shape Part 314 : Connection part 315 : Detour part 32 : Individual electrode 321 : Strip part 322 : Pad part 33 : Relay electrode 331 : Strip part 332 : Connection part 4 : Resistor layer 4K : Resistor film 41 : Heat generating part 5 : Connection Substrate 51 : Second Main Surface 52 : Second Rear Surface 55 : Control Electrode 59 : Connector 61 : Wire 7 : Driver IC
71 : Input pad 72 : Output pad 78 : Protective resin 8 : Heat dissipation member 81 : First support surface 82 : Second support surface 91 : Platen roller

Claims (15)

a substrate;
a resistor layer having a plurality of heat generating portions arranged in the main scanning direction and supported by the substrate;
a wiring layer that constitutes a current path to the plurality of heat generating parts and is supported by the substrate;
a protective layer covering the resistor layer and the wiring layer;
with
The protective layer includes a first layer containing silicon element,
The refractive index of the first layer is higher than the refractive index of silicon nitride composed of silicon element and nitrogen element in a stoichiometric composition ratio, and is lower than or equal to the refractive index of intrinsic silicon, which is an intrinsic semiconductor.
thermal print head. The refractive index of the first layer is 2.05 or more and 3.882 or less.
A thermal printhead according to claim 1 . the refractive index of the first layer is less than 3.882;
3. A thermal printhead according to claim 2. The first layer is a compound of silicon element and nitrogen element, and has a higher content ratio of silicon element than silicon nitride composed of the stoichiometric composition ratio.
A thermal printhead according to claim 3. The protective layer further comprises a second layer covering the first layer,
The thermal printhead according to any one of claims 1 to 4. wherein the second layer is silicon carbide;
A thermal printhead according to claim 5. The substrate includes a base material composed of a single crystal semiconductor,
A thermal printhead according to any one of claims 1 to 6. The substrate further includes an insulating layer sandwiched between the base material and the resistor layer,
A thermal printhead according to claim 7 . The resistor layer is formed on the insulating layer while exposing a portion of the insulating layer,
The wiring layer is formed on the resistor layer while exposing the plurality of heat generating portions,
wherein the protective layer is formed on the wiring layer;
A thermal printhead according to claim 8 . The wiring layer comprises: a first conductor layer laminated on the resistor layer while exposing a part of the resistor layer; a laminated second conductor layer;
the second conductor layer has a resistance value per unit length in the sub-scanning direction that is lower than that of each of the plurality of heat generating portions;
The first conductor layer has a resistance value per unit length in the sub-scanning direction between each of the plurality of heat generating portions and the second conductor layer.
A thermal printhead according to claim 9 . The constituent material of the first conductor layer contains Ti,
The constituent material of the second conductor layer contains Cu,
A thermal printhead according to claim 10 . the base material has a main surface facing the resistor layer and a convex portion projecting from the main surface and extending in the main scanning direction;
Each of the plurality of heat generating portions is formed on the convex portion,
A thermal printhead according to any one of claims 7 to 11. wherein the single crystal semiconductor is silicon;
A thermal printhead according to any one of claims 7 to 12. preparing a substrate;
a step of forming a resistor layer having a plurality of heat generating portions arranged in the main scanning direction and supported by the substrate;
A step of forming a wiring layer supported by the base material by configuring an energization path to the plurality of heat generating parts;
forming a protective layer covering the resistor layer and the wiring layer;
including
forming the protective layer includes forming a first layer containing silicon element;
In the step of forming the first layer, a film formation process is performed using a raw material gas containing ammonia (NH ₃ ) and silane (SiH ₄ ),
A ratio (NH ₃ /SiH ₄ ) between ammonia (NH ₃ ) and silane (SiH ₄ ) in the raw material gas is 0.1 or more and 4 or less.
A method for manufacturing a thermal printhead. The film formation process is performed by plasma CVD,
15. The method of manufacturing a thermal printhead according to claim 14.

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