Patent Application
20230140231
The present disclosure relates to a thermal print head and a thermal printer. The present disclosure also relates to a method for manufacturing a thermal print head.
Patent document 1 discloses a conventional thermal print head. The thermal print head includes a main substrate having a conductive layer and a resistive layer, and a circuit board having a driver IC mounted thereon. The resistive layer includes a plurality of heat generating parts arranged side by side in the main scanning direction. The conductive layer forms a conductive path for passing electrical current to the heat generating parts.
For printing by the thermal print head, electric current is passed to the resistive layer to cause the heat generating parts to generate heat. The heat is transferred to a print medium (e.g., a thermal recording paper), so that the color of the print medium changes to form an image.
One object of the present disclosure is to provide a thermal print head and a thermal printer having higher durability and reliability than conventional designs. Another object of the present disclosure is to provide a method for manufacturing such a thermal print head.
A first aspect of the present disclosure provides a thermal print head that includes: a substrate made of a single crystal semiconductor and including an obverse surface facing in one sense of a thickness direction; a resistive layer supported by the substrate and including a plurality of heat generating parts arranged side by side in a main scanning direction; and a wiring layer supported by the substrate and forming a conductive path to the plurality of heat generating parts. The wiring layer includes a conductive part and a heat generating sub-part for each of the plurality of heat generating parts, where the conductive part has a lower resistance value per unit length in a sub-scanning direction than the heat generating part, and where the heat generating sub-part has a resistance value per unit length in the sub-scanning direction that falls between the respective resistance values of the heat generating part and the conductive part. The substrate includes a ridge raised from the obverse surface and extending in the main scanning direction. The heat generating part, the heat generating sub-part and the conductive part are disposed on the ridge. The heat generating sub-part is located between the heat generating part and the conductive part in the sub-scanning direction.
A second aspect of the present disclosure provides a thermal printer that includes the thermal print head of the first aspect, and a platen directly opposite the thermal print head.
A third aspect of the present disclosure provides a method for manufacturing a thermal print heat, the method including: a substrate preparing step of preparing a substrate made of a single crystal semiconductor; a substrate processing step of processing the substrate to form an obverse surface facing in one sense of a thickness direction and a ridge that is raised from the obverse surface and extends in a main scanning direction; a resistive layer forming step of forming a resistive layer that is supported by the substrate and includes a plurality of heat generating parts arranged side by side in the main scanning direction; and a wiring layer forming step of forming a wiring layer that is supported by the substrate and forms a conductive path to the plurality of heat generating parts. The wiring layer includes a conductive part and a heat generating sub-part for each of the plurality of heat generating parts, where the conductive part has a lower resistance value per unit length in a sub-scanning direction than the heat generating part, and where the heat generating sub-part has a resistance value per unit length in the sub-scanning direction that falls between the respective resistance values of the heat generating part and the conductive part. The heat generating part, the heat generating sub-part and the conductive part are formed on the ridge. The heat generating sub-part is located between the heat generating part and the conductive part in the sub-scanning direction.
The present disclosure provides a thermal print head (and a thermal printer) having higher durability and reliability. Additionally, the present disclosure can provide a method for manufacturing a thermal print head having higher durability and reliability.
Embodiments of the present disclosure will be described below with reference to the drawings. In the following description, the same or slimier components are denoted by the same reference numerals, and a description of such a component is omitted.
The head substrate 1 supports the wiring layer 3 and the resistive layer 4. The head substrate 1 has a rectangular shape elongated in the main scanning direction x. In the following description, the thickness direction of the head substrate 1 is designated as a thickness direction z. The head substrate 1 is not limited to specific dimensions. In one example, the head substrate 1 measures 725 μm in thickness (a dimension in the thickness direction z), from 50 to 150 mm in the main scanning direction x, and from 2.0 to 5.0 mm in the sub-scanning direction y.
The head substrate 1 is made of a single crystal semiconductor, such as silicon (Si). As shown in
The head substrate 1 has a ridge 13. The ridge 13 is raised from the first obverse surface 11 in the thickness direction z and elongated in the main scanning direction x. In the illustrated example, the ridge 13 is offset in the sub-scanning direction y toward the downstream end of the head substrate 1. The ridge 13, which is a part of the head substrate 1, is made of the single crystal semiconductor, such as Si.
The ridge 13 has a top part 130, a pair of first slopes 131A and 131B, and a pair of second slopes 132A and 132B.
The top part 130 is where the distance from the first obverse surface 11 is largest within the ridge 13. The top part 130 may be a flat surface substantially parallel to the first obverse surface 11, for example. In view of the thickness direction z, the top part 130 has the shape of a long narrow rectangle extending in the main scanning direction x.
As shown in
As shown in
The first obverse surface 11 of the head substrate 1 has a (100) plane (by the Miller Indices). According to the manufacturing method described below, the angle α1 (see
As shown in
The resistive layer 4 is supported by the head substrate 1. As shown in
As shown in
The wiring layer 3 forms a conductive path for passing electric current to the heat generating parts 41. The wiring layer 3 is supported by the head substrate 1. As shown in
As shown in
As shown in
As shown in
The wiring layer 3 (the individual electrodes 31 and the common electrode 32) is composed of a first conductive layer 301 and a second conductive layer 302 stacked in the thickness direction z.
The first conductive layer 301 is disposed on the resistive layer 4. The first conductive layer 301 is made of a material having a resistivity that is lower than the resistive layer 4 and higher than the second conductive layer 302. Preferably, the first conductive layer 301 has an electrical resistivity from 10−6 to 10−7 Ωm, for example. Preferably, in addition, the first conductive layer 301 has a heat conductivity lower than 100 W/m, for example. The first conductive layer 301 may be made of titanium (Ti) in one example, and other suitable materials include Ta, Ga, Sn, PtIr, Pt, thallium (TI), vanadium (V) and Cr. The first conductive layer 301 can be formed by any suitable process, such as sputtering, CVD, and plating, depending on the material used. For example, when the material is Ti, the first conductive layer 301 can be formed by sputtering. The thickness of the first conductive layer 301 is not specifically limited. In one example, the thickness of the first conductive layer 301 is from 0.1 to 0.2 μm.
The second conductive layer 302 is disposed on the first conductive layer 301. The second conductive layer 302 covers a part of the first conductive layer 301. As such, a part of the first conductive layer 301 is exposed from the second conductive layer 302. The second conductive layer 302 is made of a material having a lower resistivity than the resistive layer 4 and the first conductive layer 301. Preferably, the second conductive layer 302 has an electrical resistivity of 10−7 Ωm or lower. In addition, the second conductive layer 302 is made of a material that is more heat conductive than the first conductive layer 301. Preferably, the second conductive layer 302 has a heat conductivity of 100 W/m or higher, for example. The second conductive layer 302 may be made of Cu in one example, and other suitable materials include alloys of Cu, Al, alloys of Al, Au, Ag, Ni and tungsten (W). The second conductive layer 302 can be formed by any suitable process, such as sputtering, CVD, and plating, selected depending on the material used. For example, when the material is Cu, the second conductive layer 302 can be formed by sputtering. When the material is Au, Ag or Ni, the second conductive layer 302 is typically formed by plating. In this case, the second conductive layer 302 may include a seed layer (of Cu, for example). The second conductive layer 302 is thicker than the first conductive layer 301. The thickness of the second conductive layer 302 depends on the material used, the magnitude of current passed to the wiring layer 3, and so on. In one example, the thickness of the second conductive layer 302 is from 0.5 to 5 μm.
The wiring layer 3 includes a pair of heat generating sub-parts 35A and 35B and a pair of conductive parts 36A and 36B for each heat generating part 41.
Each pair of heat generating sub-parts 35A and 35B are formed by the parts of the first conductive layer 301 exposed from the second conductive layer 302. In other words, the heat generating sub-parts 35A and 35B are the parts of the wiring layer 3 where the first conductive layer 301 is not covered with the second conductive layer 302. The heat generating sub-parts 35A and 35B in each pair are adjacent to the opposite ends of the corresponding heat generating part 41 in the sub-scanning direction y. The heat generating sub-part 35A is adjacent to the heat generating part 41 on the upstream side in the sub-scanning direction y, and the heat generating sub-part 35B is adjacent to the heat generating part 41 on the downstream side in the sub-scanning direction y. The heat generating sub-part 35A is an example of “upstream-side heat generating sub-part”, whereas the heat generating sub-part 35B an example of “downstream-side heat generating sub-part”.
The heat generating sub-part 35A is located on the top part 130. The opposite ends of the heat generating sub-part 35A in the sub-scanning direction y are both located on the top part 130. The heat generating sub-part 35B extends from the first slope 131B to the second slope 132B. The upstream end of the heat generating sub-part 35B in the sub-scanning direction y is located on the first slope 131B, and the downstream end of the heat generating sub-part 35B in the sub-scanning direction y is located on the second slope 132B.
Each pair of conductive parts 36A and 36B is formed by the first conductive layer 301 and the second conductive layer 302. In other words, the conductive parts 36A and 36B are the parts of the wiring layer 3 where the second conductive layer 302 is stacked on the first conductive layer 301. The conductive parts 36A and 36B in each pair are respectively located on the sides of the heat generating sub-part 35A and 35B away from the corresponding heat generating part 41. The conductive part 36A is adjacent to the heat generating sub-part 35A on the upstream side in the sub-scanning direction y, and the conductive part 36B is adjacent to the heat generating sub-part 35B on the downstream side in the sub-scanning direction y. The conductive part 36A is an example of “upstream side conductive part”, whereas the conductive part 36B is an example of “downstream conductive part”.
The conductive part 36A extends from the top part 130 along the first slope 131A and the second slope 132A to reach a part of the first obverse surface 11 located upstream from the ridge 13 in the sub-scanning direction y. The downstream end of the conductive part 36A in the sub-scanning direction y is located on the top part 130. The conductive part 36B extends from the second slope 132B to a part of the first obverse surface 11 located downstream from the ridge 13 in the sub-scanning direction y. The upstream end of the conductive part 36B in the sub-scanning direction y is located on the second slope 132B.
Since the first conductive layer 301, the second conductive layer 302 and the resistive layer 4 have the resistance values satisfying the relation described above, the resistance value of the conductive parts 36A and 36B per unit length in the sub-scanning direction is lower than that of the heat generating parts 41. In addition, the resistance value of the heat generating sub-parts 35A and 35B per unit length in the sub-scanning direction falls between the resistance value of the heat generating part 41 and the resistance value of the conductive parts 36A and 36B. Consequently, when electric current is passed to each heat generating part 41, the amount of heat generated by each of the heat generating sub-parts 35A and 35B is smaller than the amount of heat generated by the heat generating part 41 and greater than the amount heat generated by each of the conductive parts 36A and 36B. For example, under the energization condition where the heat generating part 41 generates heat of around 300° C., each of the heat generating sub-parts 35A and 35B will generate heat of around 150 to 200° C.
The protective layer 2 covers and protects the wiring layer 3 and the resistive layer 4. The protective layer 2 is made of an insulating material. For example, the protective layer 2 may be made of silicon nitride (SiN), and other examples of the insulating material include silicon oxide (SiO2), silicon carbide (SiC) aluminum nitride (AlN). The protective layer 2 may be composed of a single layer or two or more layers containing the insulating material. The thickness of the protective layer 2 is not specifically limited. In one example, the thickness of the protective layer 2 is from 0.1 to 10 μm.
The protective layer 2 has a plurality of pad openings 21 as shown in
As shown in
The driver ICs 7 are mounted on the second obverse surface 51 of the connecting substrate 5 and selectively energize the heat generating parts 41. The driver ICs 7 are connected to the individual electrodes 31 with the wires 61. The driver ICs 7 controls energization of the heat generating parts 41 according to an external command signal provided to the thermal print head A1 through the connecting substrate 5. The driver ICs 7 are connected to the wiring pattern (not shown) of the connecting substrate 5 with a plurality of wires 62. The driver ICs 7 are provided as many as necessary for the number of heat generating parts 41.
The driver ICs 7 and the wires 61 and 62 are covered with the protective resin 78. The protective resin 78 is made of an insulating resin, which may be black. The protective resin 78 extends from the head substrate 1 to the connecting substrate 5.
The connector 59 connects the thermal print head A1 to the thermal printer Pr. The connector 59 is attached to the connecting substrate 5 and connected to the wiring pattern (not shown) of the connecting substrate 5.
The heat dissipating member 8 supports the head substrate 1 and the connecting substrate 5 and dissipates heat from the heat generating parts 41 to the outside via the head substrate 1. The heat dissipating member 8 may be a block of metal, such as A1. The heat dissipating member 8 has a first support surface 81 and a second support surface 82. The first support surface 81 and the second support surface 82 face upward in the thickness direction z and are arranged side by side in the sub-scanning direction y. The first support surface 81 is bonded to the first reverse surface 12 of the head substrate 1. The second support surface 82 is bonded to the second reverse surface 52 of the connecting substrate 5.
Next, an example of a method for manufacturing the thermal print head A1 is described below with reference to
First, a material substrate 1K is prepared as shown in
Next, the first obverse surface 11K is covered with a mask layer and then anisotropically etched using KOH, for example. This provides the material substrate 1K with a ridge 13K as shown in
Next, the mask layer is removed, followed by anisotropic etching using KOH, for example. Processing the material substrate 1K in this way provides a head substrate 1 having a first obverse surface 11, a first reverse surface 12 and a ridge 13 as shown in
Subsequently, an insulating layer 19 is formed as shown in
Subsequently, a resistive film 4K is formed as shown in
Subsequently, a wiring film 3K is formed as shown in
Subsequently, as shown in
Next, a protective layer 2 is formed. The protective layer 2 is formed by, for example CVD to deposit SiN on the insulating layer 19, the wiring layer 3 (the first conductive layer 301 and the second conductive layer 302) and the resistive layer 4. A plurality of pad openings 21 are formed by removing parts of the protective layer 2 by etching, for example. Subsequently, the head substrate 1 (
Subsequently, the head substrate 1 is subjected to assembling steps. The assembling steps may include attaching the head substrate 1 and a connecting substrate 5 to a heat dissipating member 8, mounting driver ICs 7 to the connecting substrate 5, and bonding a plurality of wires 61 and 62, and forming a protective resin 78. Then, the thermal print head A1 is completed as described above.
The thermal print head A1 described above has the following advantages.
According to the thermal print head A1, each of the heat generating sub-parts 35A and 35B is located between a heat generating part 41 and a conductive part 36A or 36B. When electric current is supplied, the temperature of the heat generating sub-parts 35A and 35B rises to a temperature lower than the temperature of the heat generating parts 41 and higher than the temperature of the conductive parts 36A and 36B. Consequently, the temperature gradient in the sub-scanning direction y is reduced, as compared with the case where the heat generating parts 41 are immediately adjacent to the conductive parts 36A and 36B. In the case where the heat generating parts 41 are immediately adjacent to the conductive parts 36A and 36B, the temperature difference around their boundaries can induce the thermal stress that would cause a break. In contrast, the thermal print head A1 is configured to prevent damage or breakage resulting from thermal stress, so that durability and reliability of the thermal print head A1 can be improved. In particular, providing a pair of heat generating sub-parts 35A and 35B at the opposite ends of each heat generating part 41 in the sub-scanning direction y is effective in reducing the temperature gradient and thus for improving reliability and durability.
According to the thermal print head A1, each heat generating parts 41 has a heat generating sub-part 35A on the upstream side in the sub-scanning direction y. Thus, a print medium fed in the sub-scanning direction y is first heated by the heat generating sub-parts 35A and then by the heat generating parts 41 that is elevated to a higher temperature. Although the heat generating sub-parts 35A generate higher-temperature heat than the conductive parts 36A, the temperature is about 150 to 200° C. under the energization conditions where the heat generating parts 41 generates heat of about 300° C. The temperature of this level is not enough to clearly change the color of thermal paper with standard sensitivity, considering the length of time (which is short) taken for the thermal paper to pass over the heat generating sub-parts 35A in the sub-scanning direction y. Yet, the thermal paper having been heated in advance by the heat generating sub-parts 35A undergoes change of color more promptly and clearly upon heating by the heat generating parts 41. This serves to improve print quality and print speed. In addition, the temperature of the heat generating parts 41 required for causing the color of a print medium to change can be lower than the temperature required when the heat generating sub-parts 35A are not present. The thermal print head A1 of this embodiment can therefore enhance energy efficiency, reduce the temperature gradient described above, reduce power consumption, and improve durability and reliability. This means that the energy load is not concentrated on the heat generating parts 41 but distributed to the heat generating sub-parts 35A. Consequently, degradation or deterioration of the heat generating parts 41 is reduced. In addition, since the temperature gradient described above is reduced, the thermal print head A1 can improve durability and reliability without decreasing printing efficiency. The thermal print head A1 can therefore achieve energy saving and longevity.
According to the thermal print head A1, the first conductive layer 301 is made of a material with lower thermally conductivity than the second conductive layer 302. This means that the heat generating sub-parts 35A can block the transfer of heat from the heat generating parts 41 to the conductive part 36A. Consequently, loss of heat generated by the heat generating parts 41 is reduced, so that energy efficiency and thermal response of the thermal print head A1 can be improved.
According to the thermal print head A1, the ridge 13 is composed of the top part 130, the first slopes 131A and 131B, and the second slopes 132A and 132B, where the first slopes 131A, 131B and the second slopes 132A, 132B are arranged in the sub-scanning directions y, with the top part 130 located in the middle. Thus, the ridge 13 has a configuration that slopes in two stages with respect to the top part 130 (the first obverse surface 11). With this configuration, the first slopes 131A and 131B can be inclined at a smaller angle α1 relative to the top part 130, which is preferable for improving print quality. A smaller angle α1 is also preferable for reducing wear of the protective layer 2 caused by a print medium passing over the protective layer 2. The thermal print head A1 can therefore improve print quality and longevity.
According to the thermal print head A1, the heat generating parts 41 are located on the first slope 131B. Consequently, the platen roller 91 can be arranged such that the center of contact 910 (see
According to the thermal print head A1, each heat generating part 41 extends from the first slope 131B to the top part 130. This arrangement allows for misalignment of the platen roller 91 in the sub-scanning direction y without degrading print quality.
According to the thermal print head A1, the heat generating sub-parts 35A are located on the top part 130 but not on the first slope 131A. In a configuration different from the thermal print head A1, the heat generating sub-parts 35 may be disposed to extend from the top part 130 to the first slope 131A. Such a configuration aims to allow for misalignment of the platen roller 91 in the sub-scanning direction y. With recent improvements in manufacturing accuracy, however, the possibility is minimized that the center of contact 910 deviates to a position upstream from the top part 130 even if the platen roller 91 is misaligned in the sub-scanning direction y. In addition, the heat generating sub-parts 35A do not contribute much to printing, and energy loss increases with the size of heat generating sub-parts 35A. That is, the thermal print head A1 is configured to reduce energy loss and prevent the reduction of printing efficiency resulting from the energy loss, as compared with the configuration in which the heat generating sub-parts 35A extend from the top part 130 to the first slope 131A. In other words, the thermal print head A1 is provided with the heat generating sub-parts 35A to reduce the temperature gradient, and yet the size (formation areas) of the heat generating sub-parts 35A is arranged to reduce or minimize reduction of printing efficiency resulting from energy loss.
According to the thermal print head A1, since the common electrode 32 is located on the downstream side of the heat generating parts 41 in the sub-scanning direction y, the individual electrodes 31 are located on the upstream side separately from the common electrode 32. As such, the pitch of the individual electrodes 31 in the main scanning direction x can be reduced to increase he printing resolution.
According to one example of the thermal print head A1, the first conductive layer 301 is made of Ti, and the second conductive layer 302 is made of Cu. This means that the resistance value per unit length in the sub-scanning direction y is higher at the heat generating sub-parts 35A and 35B where the first conductive layer 301 is not covered with the second conductive layer 302 than at the conductive parts 36A and 36B where the first conductive layer 301 and the second conductive layer 302 are stacked. In addition, the first conductive layer 301 is thinner than the second conductive layer 302, and thus the cross section of the wiring layer 3 is smaller at the heat generating sub-parts 35A and 35B than at the conductive parts 36A and 36B. This also contribute to the configuration that the resistance value per unit length in the sub-scanning direction y is higher at the heat generating sub-parts 35A and 35B than at the conductive parts 36A and 36B.
The thermal print head B1 includes the ridge 13 along the downstream edge of the head substrate 1 in the sub-scanning direction y. That is, no part of the first obverse surface 11 is located downstream from the ridge 13 in the sub-scanning direction y. Thus, the wiring layer 3 of this embodiment is arranged as shown in
As shown in
As shown in
With reference to
According to the arrangement described above, one common electrode 32 forms two adjacent conductive paths. Each of the two conductive paths includes, in order of connection, the common electrode 32, i.e., one branching part 325 and one of two strip parts 324), a first heat generating part 41, a relay electrode 33 and a second heat generating part 41 adjacent to the first heat generating part 41, and an individual electrode 31. Energizing one individual electrode 31 will energize the two heat generating parts 41 that are adjacent to each other in the main scanning direction and electrically connected between the one individual electrode 31 and a common electrode 32. Such two adjacent heat generating parts 41 correspond to one dot on a print medium.
As shown in
Similarly to the thermal print head A1, the thermal print head B1 includes the heat generating sub-parts 35A and 35B each of which is located between a heat generating part 41 and a conductive part 36A or 36B. Consequently, the temperature gradient in the sub-scanning direction y is reduced, as compared within the case where the heat generating parts 41 are immediately adjacent to the conductive parts 36A and 36B. Similarly to the first embodiment, the thermal print head B1 can therefore improve durability and reliability.
According to the thermal print head B1, no part of the first obverse surface 11 is located downstream from the ridge 13 in the sub-scanning direction y. With this configuration, the downstream part of the head substrate 1 in the sub-scanning direction y can be shorter. Consequently, the possibility is reduced that a print medium being transported makes contact with a part of the head substrate 1 that is downstream from the ridge 13 in the sub-scanning direction y. This means that a print medium P1 can be fed through a straight path as shown in
According to the second embodiment, no part of the first obverse surface 11 is located downstream from the ridge 13 in the sub-scanning direction y. However, the present disclosure is not limited to this. In one variation, the first obverse surface 11 may have a relatively small part located downstream from the ridge 13 in the sub-scanning direction y, as compared with the thermal print head A1.
As shown in
In the method for manufacturing the thermal print head C1, the resistive layer 4 is formed after the wiring layer 3. Specifically, the method for manufacturing the thermal print head A1 is modified such that the step of forming the insulating layer 19 (see
Similarly to the thermal print head A1, the thermal print head C1 includes the heat generating sub-parts 35A and 35B each of which is located between a heat generating part 41 and a conductive part 36A or 36B. Consequently, the temperature gradient in the sub-scanning direction y is reduced, as compared with the case where the heat generating parts 41 are immediately adjacent to the conductive parts 36A and 36B. Similarly to the first embodiment, the thermal print head C1 can therefore improve durability and reliability.
According to the thermal print head C1, the wiring layer 3 (the first conductive layer 301 and the second conductive layer 302) and the resistive layer 4 are stacked on the insulating layer 19 in the stated order. That is, in the method for manufacturing the thermal print head C1, the resistive layer 4 is formed after the wiring layer 3 is formed on the insulating layer 19. In the method for manufacturing the thermal print head A1, the resistive film 4K, the first conductive film 301K and the second conductive film 302K are deposited in the stated order, and then parts of the first conductive film 301K and the second conductive film 302K are removed by etching, for example. Since the etching of the resistive film 4K, the first conductive film 301K and the second conductive film 302K is sequentially performed after all of these films are deposited, the transportation work between the deposition apparatus and the etching apparatus is reduced. However, when each of the first conductive film 301K and the second conductive film 302K is etched, the resistive film 4K is also placed in the environment for the etching. The resistive film 4K may be damaged, depending on the material of the resistive film 4K or the process used for etching each of the first conductive film 301K and the second conductive film 302K. In contrast, according to the thermal print head C1, the resistive film 4K (the resistive layer 4) is formed after the first conductive layer 301 and the second conductive layer 302 are processed (in the first partial removal step and the second partial removal step) and thus without a risk of damaging the resistive film 4K. The present embodiment can therefore reduce the risk of damaging the resistive layer 4 (the heat generating parts 41) during processing.
According to the third embodiment, the first conductive layer 301 and the second conductive layer 302 may be stacked in reverse of the order described above.
As shown in
The thermal print head C2 can achieve the same advantages as the thermal print head C1.
According to the thermal print heads C1 and C2 shown in
The thermal print heads C1 and C2 may also be modified such that no part of the first obverse surface 11 is located downstream from the ridge 13 in the sub-scanning direction y as in the second embodiment (
As shown in
A method for manufacturing the thermal print head D1 includes, in sequence, the resistive film deposition step, the resistive film partial removal step, the first deposition step, the first partial removal step, the second deposition step and the second partial removal step. Through these steps, the resistive layer 4 and the wiring layer 3 (the first conductive layer 301 and the second conductive layer 302) are sequentially formed. In other words, the wiring layer forming step is performed after the resistive film deposition step. In this way, as shown in
Similarly to the thermal print head A1, the thermal print head D1 includes the heat generating sub-parts 35A and 35B each of which is located between a heat generating part 41 and a conductive part 36A or 36B. Consequently, the temperature gradient in the sub-scanning direction y is reduced, as compared with the case where the heat generating parts 41 are immediately adjacent to the conductive parts 36A and 36B. Similarly to the first embodiment, the thermal print head D1 can therefore improve durability and reliability.
As shown in
The thermal print head D1 is a variation of the thermal print head A1 having the resistive layer 4 and the first conductive layer 301 disposed more locally. Such a modification may also be made to other configurations. For example, the thermal print heads C1 and C2 may be modified such that the resistive layer 4a and the first conductive layer 301 are disposed locally.
As shown in
The thermal print heads D1 to D3 may also be modified such that no part of the first obverse surface 11 is located downstream of the ridge 13 in the sub-scanning direction y as in the second embodiment (
As shown in
The conductive layer 300 may be made of Cu as with the second conductive layer 302. As shown in
Similarly to the thermal print head A1, the thermal print head E1 includes the heat generating sub-parts 35A and 35B each of which is located between a heat generating part 41 and a conductive part 36A or 36B. Thus, the temperature gradient in the sub-scanning direction y is reduced, as compared with the case where the heat generating parts 41 are immediately adjacent to the conductive parts 36A and 36B. Similarly to the first embodiment, the thermal print head E1 can therefore improve durability and reliability.
According the fifth embodiment, the heat generating sub-parts 35A and 35B (i.e., the thinner parts 300b) are rectangular as viewed in the thickness direction z. However, the shape of the heat generating sub-parts 35A and 35B is not limited to a rectangle. In one variation, patterning may be applied to the thinner parts 300b.
The method for manufacturing a thermal print head, a thermal printer and a thermal print head according to the present disclosure is not limited to the foregoing embodiments. Further, the specific configuration of each part of the thermal print head, the thermal printer and the thermal print head according to the present disclosure may be modified in design in many ways. The present disclosure includes the configurations described in the following clauses.
Clause 1.
A thermal print head comprising:
a substrate made of a single crystal semiconductor and including an obverse surface facing in one sense of a thickness direction;
a resistive layer supported by the substrate and including a plurality of heat generating parts arranged side by side in a main scanning direction; and
a wiring layer supported by the substrate and forming a conductive path to the plurality of heat generating parts,
wherein the wiring layer includes a conductive part and a heat generating sub-part for each of the plurality of heat generating parts, the conductive part having a lower resistance value per unit length in a sub-scanning direction than the heat generating part, the heat generating sub-part having a resistance value per unit length in the sub-scanning direction that falls between the respective resistance values of the heat generating part and the conductive part,
the substrate includes a ridge raised from the obverse surface and extending in the main scanning direction,
the heat generating part, the heat generating sub-part and the conductive part are disposed on the ridge, and
the heat generating sub-part is located between the heat generating part and the conductive part in the sub-scanning direction.
Clause 2.
The thermal print head according to clause 1,
wherein the ridge includes a top part that is most distant from the obverse surface, an upstream-side first slope connected to the top part on an upstream side in the sub-scanning direction, and a downstream-side first slope connected to the top part on a downstream side in the sub-scanning direction,
the upstream-side first slope and the downstream-side first slope are inclined to the obverse surface at a first inclination angle, and
the heat generating part extends from the downstream-side first slope to the top part.
Clause 3.
The thermal print head according to clause 2,
wherein the ridge includes an upstream-side second slope connected to the upstream-side first slope on an opposite side from the top part in the sub-scanning direction, and a downstream-side second slope connected to the downstream-side first slope on an opposite side from the top part in the sub-scanning direction,
the upstream-side second slope and the downstream-side second slope are inclined to the obverse surface at a second inclination angle, and
the second inclination angle is greater than the first inclination angle.
Clause 4.
The thermal print head according to clause 3, wherein the heat generating sub-part includes an upstream-side heat generating sub-part located upstream from the heat generating part in the sub-scanning direction, and a downstream-side heat generating sub-part located downstream from the heat generating part in the sub-scanning direction.
Clause 5.
The thermal print head according to clause 4, wherein the conductive part includes an upstream-side conductive part adjacent to the upstream-side heat generating sub-part on an opposite side from the heat generating part in the sub-scanning direction, and a downstream-side conductive part adjacent to the downstream-side heat generating sub-part on an opposite side from the heat generating part in the sub-scanning direction.
Clause 6.
The thermal print head according to clause 5, wherein the upstream-side heat generating sub-part is disposed on the top part.
Clause 7.
The thermal print head according to clause 6, wherein the upstream-side conductive part extends from the top part along the upstream-side first slope and the upstream-side second slope to reach the obverse surface.
Clause 8.
The thermal print head according to any one of clauses 5 to 7, wherein the downstream-side heat generating sub-part extends from the downstream-side second slope to the downstream-side first slope.
Clause 9.
The thermal print head according to clause 8, wherein the downstream-side conductive part is disposed on the downstream-side second slope.
Clause 10.
The thermal print head according to any one of clauses 1 to 9,
wherein the wiring layer and the resistive layer overlap with each other at least in part as viewed in the thickness direction, and
each of the plurality of heat generating parts is formed by a part of the resistive layer not overlapping with the wiring layer as viewed in the thickness direction.
Clause 11.
The thermal print head according to clause 10,
wherein the wiring layer includes a first conductive layer and a second conductive layer stacked in the thickness direction,
the conductive part is formed by a part where the second conductive layer is present, and
the heat generating sub-part is formed by a part of the first conductive layer not overlapping with the second conductive layer as viewed in the thickness direction.
Clause 12.
The thermal print head according to clause 11,
wherein the resistive layer is disposed on the substrate,
the first conductive layer is disposed on the resistive layer such that a part of the resistive layer remains exposed, and
the second conductive layer is disposed on the first conductive layer such that a part of the first conductive layer remains exposed.
Clause 13.
The thermal print head according to clause 11,
wherein the first conductive layer is disposed on the substrate,
the second conductive layer is disposed on the first conductive layer such that a part of the first conductive layer remains exposed, and
the resistive layer is disposed on the substrate and at least overlaps with the part of the first conductive layer exposed from the second conductive layer as viewed in the thickness direction.
Clause 14.
The thermal print head according to any one of clauses 11 to 13, wherein the first conductive layer is thinner than the second conductive layer.
Clause 15.
The thermal print head according to any one of clauses 11 to 14, wherein the first conductive layer is made of a material having a lower heat conductivity than that of the second conductive layer.
Clause 16.
The thermal print head according to clause 10,
wherein the wiring layer includes a thicker part and a thinner part having mutually different dimensions in the thickness direction,
the heat generating sub-part is formed by the thinner part, and
the conductive part is formed by the thicker part.
Clause 17.
The thermal print head according to clause 16, wherein the thinner part is patterned as viewed in the thickness direction.
Clause 18.
The thermal print head according to any one of clauses 1 to 17, wherein the single crystal semiconductor is Si.
Clause 19.
A thermal printer comprising:
the thermal print head according to any one of clauses 1 to 18; and
a platen directly opposite the thermal print head.
Clause 20.
A method for manufacturing a thermal print head, comprising:
a substrate preparing step of preparing a substrate made of a single crystal semiconductor;
a substrate processing step of processing the substrate to form an obverse surface facing in one sense of a thickness direction and a ridge that is raised from the obverse surface and extends in a main scanning direction;
a resistive layer forming step of forming a resistive layer that is supported by the substrate and includes a plurality of heat generating parts arranged side by side in the main scanning direction; and
a wiring layer forming step of forming a wiring layer that is supported by the substrate and forms a conductive path to the plurality of heat generating parts,
wherein the wiring layer includes a conductive part and a heat generating sub-part for each of the plurality of heat generating parts, the conductive part having a lower resistance value per unit length in a sub-scanning direction than the heat generating part, the heat generating sub-part having a resistance value per unit length in the sub-scanning direction that falls between the respective resistance values of the heat generating part and the conductive part,
the heat generating part, the heat generating sub-part and the conductive part are formed on the ridge, and
the heat generating sub-part is located between the heat generating part and the conductive part in the sub-scanning direction.
Clause 21.
The method according to clause 20,
wherein the resistive layer forming step includes a resistive film deposition step of depositing a resistive film,
the wiring layer forming step includes a first deposition step of depositing a first conductive film, a first partial removal step of removing a part of the first conductive film to form a first conductive layer, and a second deposition step of depositing a second conductive film, and a second partial removal step of removing a part of the second conductive film to form a second conductive layer,
the first conductive layer and the second conductive layer are stacked in the thickness direction,
the conductive part is formed by a part where the second conductive layer is present, and
the heat generating sub-part is formed by a part of the first conductive layer not overlapping with the second conductive layer as viewed in the thickness direction.
Clause 22.
The method according to clause 21, wherein the resistive film deposition step is performed before the wiring layer forming step.
Clause 23.
The method according to clause 21, wherein the resistive film deposition step is performed after the wiring layer forming step.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-069149 | Apr 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/012824 | 3/26/2021 | WO |
