JP2007196656A - Thermal head and thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal head and a thermal printer capable of increasing the temperature rising / falling rate of a heating element of a head substrate and uniforming the temperature distribution in the plane direction.
SOLUTION: End portions 12 of common electrode wiring 6a and individual electrode wiring 6b, which are connected to the heat generating element 5, are connected from the heat generating element 5 in the center of the main scanning direction m to the sub scanning direction s. It has a shape such that the amount of heat transfer is larger than the amount of heat transfer at the end in the main scanning direction m. Specifically, the connecting end portion 12 has a flat portion 12a and an inclined portion 12b, and the shape in the plane direction including the main scanning direction m and the sub-scanning direction s is a quadrangular shape with corners arcuate. In addition, the shape of the cross section perpendicular to the main scanning direction m is a tapered shape.
[Selection] Figure 4

Description

  The present invention relates to a thermal head having a flexible wiring board, and a thermal printer including the thermal head and incorporated as a printer mechanism such as a word processor or a facsimile machine.

  Conventionally, a thermal printer having a thermal head has been used as a printer mechanism of a word processor, a facsimile machine or the like.

  In a conventional thermal head, for example, a plurality of heating elements and a plurality of circuit conductors arranged in a straight line are deposited on a rectangular ceramic substrate, and at least one end of these circuit conductors is attached to the upper surface of the ceramic substrate. A head substrate that is led out to one side and a plurality of circuit terminals are arranged in parallel in the lead-out portion, and a part is superposed on the head substrate along one side of the ceramic substrate in which the circuit terminals are arranged in parallel, and this overlapping portion And a flexible wiring board (hereinafter abbreviated as “FPC”) in which a plurality of wiring terminals electrically connected to the circuit terminals are arranged in parallel.

  The FPC is a wiring board for supplying external power, a print signal, and the like to a heating element on the head substrate. When a predetermined power is supplied to the heating element on the head substrate via the FPC, the FPC generates heat. The elements selectively generate Joule heat individually based on the print signal, and a predetermined print is formed on the recording medium.

  The circuit terminals and the wiring terminals are electrically connected by soldering or the like. In this case, first, the edge of the FPC on which the wiring terminals are arranged side by side is one side of the ceramic substrate on which the circuit terminals are arranged in parallel. And soldering is performed between the corresponding terminals, and the solder is heated and melted by a heater bar or the like.

  The circuit conductor on the head substrate includes a pair of electrodes connected to both ends of the heating element. The ends of these electrodes connected to the heating elements have a plan view shape narrower in the central region in the main scanning direction than the both end regions (see Patent Document 1), or the cross-sectional shape of the peripheral portion is formed in a tapered shape. I process it. By adopting such a shape, it is possible to reduce the amount of paper residue generated by reducing friction with the conveyed recording medium, and to suppress the generation of faults in the protective film covering the electrodes.

JP 2002-225325 A Japanese Patent Laid-Open No. 11-42802

  The main characteristics required for recent thermal printers are high resolution and high speed. In order to satisfy these requirements, it is necessary to increase the recording medium conveyance speed by increasing the heating rate and the cooling rate in the heating element of the head substrate, and the temperature distribution in the planar direction of the heating element. It is necessary to make the print dots clear by making the pattern uniform.

  In the prior art including Patent Documents 1 and 2, no electrode terminal shape for improving such characteristics has been proposed.

  An object of the present invention is to provide a thermal head and a thermal printer that can increase the temperature rise and fall rates of the heating elements of the head substrate and make the temperature distribution in the plane direction uniform.

The present invention relates to a thermal head having a heating element arranged side by side in the main scanning direction, and a pair of electrodes connected to both ends of the heating element and extending in the sub-scanning direction to generate heat.
The connection end of the electrode connected to the heating element has an amount of heat transfer from the heating element to the sub-scanning direction at the center in the main scanning direction of each heating element. It is a thermal head characterized by having a shape which becomes larger than the said heat-transfer amount in a part.

  According to the present invention, the connection end portion has a cross-sectional area perpendicular to the sub-scanning direction of the connection end portion, and the cross-sectional area increases as the distance from the heating element increases in the sub-scanning direction. The ratio of the change in the cross-sectional area is such that the end portion is smaller than the central portion.

  According to the present invention, the connecting end portion has a quadrangular shape in which a planar portion including the main scanning direction and the sub-scanning direction has an arcuate corner portion, and a cross-sectional shape perpendicular to the main scanning direction. Has a tapered shape.

  According to the present invention, the connection end portion includes a flat portion having a square shape in which the corner portion has an arcuate shape and an inclined portion having the tapered shape, and the inclined portion has an arithmetic mean surface roughness of the flat portion. The arithmetic average surface roughness is larger.

  Further, the present invention is characterized in that the connection boundary line between the electrode and the heat generating element at the connection end is an uneven shape in which a large number of protrusions and recesses are arranged.

The present invention also relates to a thermal head in which a plurality of heating elements arranged in the main scanning direction and a pair of electrodes for energizing the heating elements are formed on a substrate.
The connection end portion of each electrode connected to the heating element has a center portion in the main scanning direction extending toward the centroid of the heating element as compared to both end portions. Head.

  Further, according to the present invention, the temperature gradient from the centroid to the outside of the heat generating element is between the centroid and the central portion in the main scanning direction of the connecting end portion, and the main scanning of the centroid and the connecting end portion. The distance between both ends in the direction is smaller.

  Further, the present invention is characterized in that the connection end portion of each electrode has a convex arc shape on the heating element side in a plan view.

The present invention also includes the above thermal head,
Conveying means for conveying the recording medium onto the heating element of the thermal head;
A thermal printer comprising: a driving unit that is electrically connected to the connection terminal of the thermal head and selectively generates heat from the heating element.

  According to the present invention, the heating elements arranged in the main scanning direction orthogonal to the conveyance direction of the recording medium, and connected to both ends of the heating element to generate heat, the recording medium conveyance direction And a pair of electrodes extending in the sub-scanning direction parallel to the thermal head.

  The connection end of the electrode connected to the heating element has an amount of heat transfer from the heating element to the sub-scanning direction at the center in the main scanning direction of each heating element. It has a shape that is greater than the amount of heat transfer at the part.

  When the heating element is driven, Joule heat is generated more in the central part (heat spot) of the heating element than in the surrounding area, and is then conducted radially from there to the entire heating area corresponding to the printed dots. Becomes hot. Since the electrode acts as a heat conductor, the amount of heat transfer from the heating element to the sub-scanning direction is increased at the center in the main scanning direction where the distance between the heat spot and the electrode is short, and the distance between the heat spot and the electrode is long. By reducing the amount of heat transfer from the heating element to the sub-scanning direction at the end in the main scanning direction, the temperature distribution of the entire heating region can be made uniform. As a result, the print dots become clear and the print quality is improved.

  According to the invention, the connection end portion is formed such that a cross-sectional area of the connection end portion in the sub-scanning direction becomes wider as the distance from the heating element in the sub-scanning direction further increases. The ratio of the change in the cross-sectional area with respect to the distance from the heating element is formed so that the end portion is smaller than the central portion. When Joule heat generated in the heating element is conducted through the electrode, the cross-sectional area of the electrode in the sub-scanning direction affects the heat transfer resistance, and the heat transfer resistance is smaller as the cross-sectional area is larger. Heat generation so that the temperature distribution of the entire heat generation region becomes uniform by making the ratio of the change in the cross-sectional area with respect to the distance from the heat generating element at the end of the connection end in the main scanning direction smaller than that at the center. The amount of heat transfer from the element in the sub-scanning direction can be controlled.

  According to the invention, the connecting end portion has a planar shape (planar shape) including the main scanning direction and the sub-scanning direction, and has a square shape with corners arcuate, and the main scanning direction. The cross-sectional shape perpendicular to the direction has a tapered shape. Thereby, the amount of heat transfer from the heating element in the sub-scanning direction can be controlled to a more suitable amount.

  According to the invention, the connection end portion includes a flat portion having a square shape in which the corner portion has an arcuate shape and an inclined portion having the tapered shape. By increasing the arithmetic average surface roughness of the inclined portion to the arithmetic average surface roughness of the flat portion, the adhesion between the heating element and the protective film provided on the electrode is improved, and the protective film is prevented from peeling. can do.

  According to the present invention, the connection boundary line between the electrode and the heat generating element at the connection end has an uneven shape in which a large number of protrusions and recesses are arranged. Thereby, the heat transfer resistance of the connection boundary part of the said electrode and the said heat generating element can be made small.

  According to the invention, there is provided a thermal head in which a plurality of heating elements arranged in the main scanning direction and a pair of electrodes for energizing the heating elements are formed on a substrate.

  The connection end portion of each electrode connected to the heat generating element has a shape in which the central portion in the main scanning direction extends toward the centroid of the heat generating element as compared with the both end portions.

  Since the electrode acts as a heat conductor, the amount of heat transfer from the heating element to the sub-scanning direction is increased at the center in the main scanning direction where the distance between the heat spot and the electrode is short, and the distance between the heat spot and the electrode is long. By reducing the amount of heat transfer from the heat generating element at the end in the main scanning direction to the sub scanning direction, the temperature distribution of the entire heat generating region can be made uniform. As a result, the print dots become clear and the print quality is improved.

  Further, according to the present invention, the temperature gradient from the centroid to the outside of the heating element is greater between the centroid and the central portion in the main scanning direction of the connection end than between the centroid and the connection end. The distance between both ends in the main scanning direction is smaller.

  According to the present invention, the connection end portion of each electrode has a circular arc shape that is convex toward the heating element in a plan view.

  As a result, the amount of heat transfer from the heating element in the sub-scanning direction can be controlled so that the temperature distribution in the entire heating region is uniform.

  According to the invention, the heat-sensitive recording medium is transported onto the head substrate of the thermal head by the transporting means, and printing is performed by selectively causing the heating elements of the thermal head to generate heat. Thereby, a thermal printer with high printing quality can be provided.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a plan view of a thermal head 1 according to an embodiment of the present invention, and FIG. 2 is an XX cross-sectional view of the thermal head 1 shown in FIG.

  The thermal head 1 includes a head substrate 2 and a flexible wiring substrate (FPC) 3 that is a flexible substrate.

  FIG. 3 is a plan view of the head substrate 2. The head substrate 2 has a substantially square shape, and a plurality of heating elements 5 are disposed on the upper surface of the ceramic substrate 4 by applying a heating resistor material or an electrode material in a predetermined pattern. A plurality of circuit terminals 7 that are electrically connected via the conductor 6 are arranged in parallel.

  The ceramic substrate 4 is made of, for example, a ceramic material such as alumina ceramics, and functions as a support base material for supporting the heating element 5, the circuit conductor 6, the driver IC (Integrated Circuit) 8, and the like. A detailed manufacturing method of the head substrate 2 will be described later.

  A manufacturing process in the case where the ceramic substrate 4 is made of alumina ceramic will be briefly described. First, a ceramic green sheet is obtained by adding and mixing an appropriate organic solvent and solvent to a ceramic raw material powder such as alumina, silica, magnesia, etc., and making it into a mud by adopting a conventionally known doctor blade method, calendar roll method, etc. Get. The obtained ceramic green sheet is punched into a predetermined shape (for example, substantially square shape) and then fired at a high temperature.

  The heating elements 5 are arranged at a predetermined pitch (for example, 62.5 μm) along the main scanning direction m at the time of printing, each of which is Ta-Si-O, Ti-Si-O, Since it is made of an electric resistance material such as Ti-C-Si-O, when power is supplied from the outside through the circuit conductor 6 and the wiring conductor of the FPC 3 described later, Joule heat is generated and This is a predetermined temperature required to form a print on the recording medium.

  The circuit conductor 6 is a signal wiring for supplying external power, a printing signal, and the like to the heating element 5 and the driver IC 8, and is made of a metal such as Al (aluminum) or Cu (copper), for example. One end of the upper surface is electrically connected to a wiring conductor of the FPC 3 described later.

  In the present embodiment, the plurality of circuit conductors 6 include a common electrode wiring 6a connected in common to all the heat generating elements 5, each heat generating element 5, and an output terminal of the driver IC 8 corresponding to each heat generating element 5. Are composed of an individual electrode wiring 6b for connecting the signal IC 6 and a signal wiring 6c connected to the input terminal of the driver IC 8. The common electrode wiring 6a and the individual electrode wiring 6b are a pair of electrodes extending in the sub-scanning direction s at the time of printing. The common electrode wiring 6a and the individual electrode wiring 6b are connected to both ends of the heating element 5 to apply power to the heating element 5. The wiring 6c serves to supply an external print signal, clock signal, latch signal, strobe signal, etc. to the driver IC 8.

  Among the circuit conductors 6, one end of the common electrode wiring 6a and the signal wiring 6c is led out to one end of the upper surface of the ceramic substrate 4, and the circuit terminal 7 is connected to each leading portion of the common electrode wiring 6a and the signal wiring 6c. Is provided. The individual electrode wiring 6b is formed between each heat generating element 5 and each driver IC 8, and is not led out to the one end portion on the upper surface of the ceramic substrate 4.

  The heating element 5 and the circuit conductor 6 as described above are provided with a predetermined wiring pattern on the upper surface of the ceramic substrate 4 by employing a conventionally well-known thin film forming method, specifically, a sputtering method, a photolithography method, an etching method, or the like. And it is deposited and formed so as to have a predetermined wiring thickness.

  The driver IC 8 includes a plurality of output terminals and input terminals, a driving circuit such as a switching element, a logic circuit such as an AND gate, a latch circuit, and a shift register on the mounting surface facing the ceramic substrate 4. The power supply to the heating element 5 is individually controlled based on the print signal inputted from the input terminal.

  The output terminal of the driver IC 8 is electrically connected to the corresponding individual electrode wiring 6b, and the input terminal is electrically connected to the corresponding signal wiring 6c via a conductive adhesive such as solder.

  The FPC 3 sandwiches a wiring conductor 9 made of a metal such as copper between a base film 3a made of polyimide resin having a thickness of 10 to 35 μm and a cover film 3b, for example, and a portion where the FPC 3 and the ceramic substrate 4 overlap each other. Wiring terminals 10 are arranged in parallel at one end of the derived wiring conductor 9, and the FPC 3 and the head substrate 2 are electrically connected by soldering these wiring terminals 10 to the corresponding circuit terminals 7. Connected.

  By connecting the FPC 3 to a printer head drive circuit of a printed wiring board provided in a thermal printer main body (not shown), power, a print signal, etc. from the printer head drive circuit are supplied to the heating element 5 and the driver IC 8 of the head substrate 2. be able to. The connection terminal 11 for connecting to the printed wiring board is configured by exposing the end of the wiring conductor 9 opposite to the wiring terminal 10 and is connected to the connector of the printer head driving circuit.

  Solder bonding between the wiring terminal 10 of the FPC 3 and the circuit terminal 7 of the head substrate 2 is performed by first connecting the end portion of the FPC 3 where the wiring terminal 10 is arranged side by side along one side of the ceramic substrate 2 where the circuit terminal 7 is arranged side by side. The soldering is performed between the corresponding wiring terminal 10 and the circuit terminal 7, and the solder is heated and melted by a heater bar or the like and then cooled and fixed.

  In this way, the thermal head 1 supplies external power, a printing signal, and the like to the heating element 5 and the driver IC 8 via the wiring conductor 9 of the FPC 3 and the circuit conductor 6 of the head substrate 2, and the heating element 5 is supplied to the driver. As the IC 8 is driven, Joule heat is selectively generated individually. The generated heat is conducted to a recording medium such as thermal paper, and a predetermined print is formed on the recording medium, thereby functioning as a thermal printer.

FIG. 4 is an enlarged perspective view of the heat generating element 5 portion of the head substrate 2.
In the present embodiment, the end portion of the common electrode wiring 6a and the individual electrode wiring 6b and the end portion (hereinafter referred to as “connection end portion”) 12 connected to the heat generating element 5 is the central portion in the main scanning direction m. The heat transfer amount from the heating element 5 in the sub-scanning direction s has a shape that is larger than the heat transfer amount at the end in the main scanning direction m.

  When the heat generating element 5 is driven, Joule heat is generated more in the central portion (heat spot) 5a of the heat generating element 5 as compared with the periphery thereof. Therefore, the heat spot of the heat generating element tends to become the highest temperature, and from there As heat is conducted radially to the surroundings, the entire heat generating area corresponding to the print dots is in a high temperature state. Since the common electrode wiring 6a and the individual electrode wiring 6b act as heat conductors, the heat spot from the heating element 5 in the center of the main scanning direction m where the distance between the heat spot and the common electrode wiring 6a and the individual electrode wiring 6b is close to the sub scanning direction. The amount of heat transfer to s is increased, and the amount of heat transfer from the heating element 5 to the sub-scanning direction s at the end in the main scanning direction m where the distance between the heat spot and the common electrode wiring 6a and the individual electrode wiring 6b is long is reduced. As a result, the temperature distribution of the entire heat generating region can be made uniform. As a result, it is possible to increase the temperature increase / decrease rate and make the temperature distribution in the heat generation region uniform, so that the print speed is increased, the print dots become clear, and the print quality is improved.

  Specifically, the cross-sectional area of the cross section perpendicular to the sub-scanning direction s of the connection end portion increases as the distance from the heating element 5 increases in the sub-scanning direction s. The shape is such that the end is smaller than the center.

  In the present invention, when the wiring width of each electrode 6 in the main scanning direction m is L, the regions where the distance from one end of each electrode 6 is 0L to 0.2L and 0.8L to 1L are defined as ends. The region where the distance is more than 0.2L and less than 0.8L is referred to as the central portion.

  When Joule heat generated in the heating element is conducted through the common electrode wiring 6a and the individual electrode wiring 6b, the cross-sectional area of the common electrode wiring 6a and the individual electrode wiring 6b in the sub-scanning direction s affects the heat transfer resistance and The larger the area, the smaller the heat transfer resistance. The ratio of the change in cross-sectional area with respect to the distance from the heating element 5 at the end portion in the sub-scanning direction of the connecting end portion 12 (hereinafter referred to as “end portion change rate”) is the cross-sectional area with respect to the distance from the heating element 5 in the central portion. The amount of heat transfer from the heating element 5 in the sub-scanning direction s is controlled so that the temperature distribution of the entire heating region becomes uniform by making it smaller than the rate of change (hereinafter referred to as “central portion change rate”). be able to.

  Further, the connecting end portion 12 has a flat portion 12a and an inclined portion 12b, and as shown in FIG. 5A, the shape in the plane direction including the main scanning direction m and the sub scanning direction s is a corner portion. Is an arcuate quadrangular shape, and as shown in FIG. 5B, the shape of the cross section perpendicular to the main scanning direction m is a tapered shape. By doing so, the amount of heat transfer from the heating element 5 in the sub-scanning direction s can be controlled to a more suitable amount.

  As shown in FIG. 4, it can be said that each connecting end portion 12 has a central portion in the main scanning direction extending toward the centroid of the heating element 5 as compared with both end portions.

  In such a case, the temperature gradient from the centroid to the outside of the heat generating element 5 is larger between the centroid and the central portion of the connection end 12 in the main scanning direction m than the center of the connection end 12. The distance between both ends in the scanning direction m is smaller. The connection end 12 has a circular arc shape that is convex toward the heat generating element 5 in plan view.

  As a result, it is possible to increase the temperature increase / decrease rate and make the temperature distribution in the heat generation region uniform, so that the print speed is increased, the print dots become clear, and the print quality is improved.

  The common electrode wiring 6a and the individual electrode wiring 6b and the common electrode wiring 6a and the individual electrode wiring 6b at the portion where the heat generating element 5 is connected, and the boundary line between the heat generating element 5 are arranged in a number of convex portions and concave portions. It has an uneven shape. Thereby, the heat transfer resistance in the boundary part of the connection end part 12 and the heat generating element 5 can be made small.

  Further, according to the present invention, the arithmetic average surface roughness in the flat portion 12a of the connection end portion 12 (measured in accordance with the recommended values of JIS B0601-1994 and JIS B0633-2001, the same shall apply hereinafter) Ra1 from the inclined portion 12b. The arithmetic average surface roughness Ra2 is increased.

  The preferable range of Ra1 is 10 to 200 mm, and the preferable range of Ra2 is 50 to 400 mm. Further, the ratio Ra1: Ra2 between Ra1 and Ra2 is preferably, for example, Ra1: Ra2 = 2: 3 to 1:10.

  Since the head substrate 2 is in direct contact with a recording medium P (see FIG. 7) described later, a protective film 23 (see FIG. 6C) described later is provided on the heating element 5, the common electrode wiring 6a, and the individual electrode wiring 6b. In the region where the protective film 23 is formed, the portion surrounded by the connection end 12 and the heat generating element 5 becomes a concave portion, so that the protective film 23 is easily peeled off. As described above, by increasing the arithmetic average surface roughness Ra2 in the inclined portion 12b rather than the arithmetic average surface roughness Ra1 in the flat portion 12a, the adhesion with the protective film in the inclined portion 12b is improved, The peeling of the protective film can be suppressed.

  In order to obtain the boundary line shape and the desired surface roughness as described above, the head substrate 2 is manufactured by the following manufacturing process.

6A, 6B, and 6C are diagrams illustrating a manufacturing process of the head substrate 2. FIG.
First, the ceramic substrate 4 is prepared as described above, and as shown in FIG. 6A (a), a laminated body in which the resistive thin film 20 and the metal thin film 21 are sequentially laminated is formed on the upper surface.

  The resistance thin film 20 and the metal thin film 21 are formed by applying a thin film forming technique such as sputtering or vacuum deposition and sequentially depositing an electric resistance material such as TaSiO and a metal material such as Al on the upper surface of the ceramic substrate 4. The

  The thickness of the resistive thin film 20 is set to 0.01 μm to 0.2 μm, for example, and the thickness of the metal thin film 21 is set to 0.3 μm to 2.5 μm, for example.

  Next, a photolithographic technique is used to deposit and form a photoresist 22 made of a photosensitive resin over the entire top surface of the laminate, and then the photoresist 22 is processed into a predetermined shape as shown in FIG. 6A (b). To do.

  As the photosensitive resin constituting the photoresist 22, for example, a positive type photosensitive resin in which a portion irradiated with ultraviolet light is altered and removed in an exposure / development process is used. As a method for depositing the photosensitive resin having such characteristics, there is a method in which a liquid photosensitive resin is applied to the upper surface of the metal thin film 21 by a spin coating method or a roll coating method and dried. The applied photosensitive resin is exposed and developed using a photomask having a predetermined pattern corresponding to the shape of the heating element 5, the common electrode wiring 6a, and the individual electrode wiring 6b, thereby forming a photoresist 22 having a predetermined shape.

  In this exposure process, the ultraviolet light applied to the photosensitive resin through the above-described photomask exposes the reverse pattern of the heating element 5, the common electrode wiring 6a, and the individual electrode wiring 6b, and develops it. The shape of the photoresist 22 corresponds to the pattern of the heating element 5, the common electrode wiring 6a, and the individual electrode wiring 6b.

  As shown in FIG. 6B (c), a well-known etching technique is employed, and the resistive thin film 20 and the metal thin film 21 where the photoresist 22 does not exist are continuously removed using the photoresist 22 as an etching mask.

  This etching is performed by immersing the laminated body in a strong acid-based etching solution capable of etching both the resistance thin film 20 and the metal thin film 21, and eroding and removing the portion where the photoresist 22 is not present with the etching solution. . As a result, the resistance thin film 20 and the metal thin film 21 are patterned along the outer shapes of the heating element 5, the common electrode wiring 6a, and the individual electrode wiring 6b.

  Next, as shown in FIG. 6B (d), the photoresist 22 remaining on the laminate is further exposed and developed into a pattern of the heating element 5, and the photoresist 22 is formed as shown in FIG. 6C (e). A photoresist 22a having a predetermined shape corresponding to the pattern of the light emitting element 5 is formed.

  In this exposure process, a photomask corresponding to the pattern of the heating element 5 is used, and in the subsequent etching process, the pattern of the photoresist 22a obtained using this photomask is used as an etching mask, so that metal A part of the thin film pattern is etched away.

  The etching mask in this step is formed so that the portions to be the connection end portions 12 of the common electrode wiring 6a and the individual electrode wiring 6b have the shape as described above.

  That is, the long side of the etching mask is such that the shape (planar view shape) in the planar direction including the main scanning direction and the sub-scanning direction of the heating element of the connection end portion 12 is a square shape with corners arcuate. One slit hole having a plurality of shapes similar to the arc shape is formed in the portion.

  Then, a heating element is formed by contacting a surface of the metal thin film pattern exposed by the above-described exposure / development with a strong acid type etching solution different from the previous etching solution to remove a part of the metal thin film pattern. A portion of the resistive thin film pattern is exposed to form a plurality of heating element elements 5, and the metal thin film pattern is separated into the common electrode wiring 6a and the individual electrode wiring 6b on both sides of the exposed portion. . Here, in order to have a taper shape, it is necessary that the photosensitive characteristics of the photoresist be maintained at the same level as in the first exposure process described above in the process of exposing the pattern of the second heating element. Important, it is achieved by temperature control of the photoresist material. Specifically, it is necessary to set the temperature during resist baking (drying) to 80 to 130 ° C. Furthermore, the taper shape can be controlled by optimizing the exposure energy and the etching solution in this step.

  At the same time, by using two or more strongly acidic materials such as hydrochloric acid, acetic acid, hydrofluoric acid, nitric acid and sulfuric acid as the etching solution in this step, the arithmetic average surface roughness in the flat portion 12a of the connection end 12 is obtained. The arithmetic mean surface roughness Ra2 in the inclined portion 12b is made larger than Ra1, and the boundary lines between the common electrode wiring 6a and the individual electrode wiring 6b and the heating element 5 are arranged in a number of convex and concave portions. It can be formed into a shape. This is due to the change in the degree of surface tension of the photoresist.

Further, a driver IC 8 or the like is mounted, and a protective film 23 is formed so as to cover the entire ceramic substrate 4 as shown in FIG. 6C (f). The protective film 23 is made of an inorganic material having excellent wear resistance and corrosion resistance, such as silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), and sialon (Si—Al—O—N). 5. The common electrode wiring 6a and the individual electrode wiring 6b are well protected from corrosion due to contact with moisture contained in the atmosphere and wear due to sliding contact of the recording medium.

  The protective film 23 is formed by, for example, employing a sputtering method and depositing the inorganic material with a thickness of 3 μm to 10 μm so as to cover the entire ceramic substrate 4.

  The thermal head 1 is obtained by bonding the head substrate 2 obtained in the above-described process to a separately manufactured FPC 3.

  FIG. 7 is a schematic diagram illustrating a configuration of a thermal printer 100 including the thermal head 1.

  The thermal printer 100 is provided with a platen roller R1, a transport roller R2, and the like as transport means for transporting the recording medium P onto the heat generating element 5 of the thermal head 1.

  The platen roller R1 is a cylindrical member in which a butadiene rubber or the like is wound around a shaft core made of a metal such as SUS to a thickness of about 3 mm to 15 mm, and is rotatably supported above the heating element 5 of the thermal head 1. The rotation causes the recording medium P to be conveyed in a direction perpendicular to the direction in which the heating elements 5 are arranged.

  Further, the surface of the platen roller R1 is in contact with the head substrate 2 with the recording medium P interposed therebetween, and the recording medium P is pressed against the heating element 5 in the contact area.

  On the other hand, the outer periphery of the transport roller R2 is formed of metal, rubber, or the like, and is provided separately from the thermal head 1 on the upstream side and the downstream side in the transport direction of the recording medium P. The transport roller R2 and the platen The roller R1 constitutes a conveying means and supports the traveling of the recording medium P.

  Simultaneously with the conveyance, the thermal head driving means 101 selectively causes Joule heating of the plurality of heating elements 5 as the driver IC 8 is driven, and the heat is transmitted to the recording medium P to form a predetermined print. .

1 is a plan view of a thermal head 1 according to an embodiment of the present invention. 2 is an XX cross-sectional view of the thermal head 1. FIG. 3 is a plan view of a head substrate 2. FIG. FIG. 3 is an enlarged perspective view of a heating element 5 portion of the head substrate 2. It is a figure which shows the shape of the connection end part. FIG. 5 is a diagram illustrating a manufacturing process of the head substrate 2. FIG. 5 is a diagram illustrating a manufacturing process of the head substrate 2. FIG. 5 is a diagram illustrating a manufacturing process of the head substrate 2. 1 is a schematic diagram illustrating a configuration of a thermal printer 100 including a thermal head 1.

Explanation of symbols

1 Thermal head 2 Head substrate 3 FPC
4 Ceramic substrate 5 Heating element 6 Circuit conductor 7 Circuit terminal 8 Driver IC
DESCRIPTION OF SYMBOLS 9 Wiring conductor 10 Wiring terminal 11 Connection terminal 12 Connection end part 100 Thermal printer 101 Thermal head drive means

Claims (9)

In a thermal head having a heating element arranged side by side in the main scanning direction, and a pair of electrodes connected to both ends of the heating element to generate heat, and extending in the sub-scanning direction,
The connection end of the electrode connected to the heating element has an amount of heat transfer from the heating element to the sub-scanning direction at the center in the main scanning direction of each heating element. A thermal head having a shape that is greater than the amount of heat transfer in the section.   The connection end portion has a cross-sectional area perpendicular to the sub-scanning direction of the connection end portion that increases with distance from the heating element in the sub-scanning direction, and changes in the cross-sectional area with respect to the distance from the heating element. The thermal head according to claim 1, wherein the ratio is such that the end portion is smaller than the central portion.   The connecting end portion has a shape in a plane direction including the main scanning direction and the sub-scanning direction, a corner portion has a quadrangular shape having an arc shape, and a cross-sectional shape perpendicular to the main scanning direction has a tapered shape. The thermal head according to claim 1 or 2, wherein   The connection end portion includes a flat portion having a square shape with the corners arcuate and an inclined portion having the tapered shape, and the arithmetic average surface roughness of the inclined portion is higher than the arithmetic average surface roughness of the flat portion. 4. The thermal head according to claim 3, wherein is larger.   5. The thermal head according to claim 3, wherein a connection boundary line between the electrode and the heat generating element at the connection end has an uneven shape in which a plurality of protrusions and recesses are arranged. In a thermal head in which a plurality of heating elements arranged in the main scanning direction and a pair of electrodes for energizing the heating elements are formed on a substrate,
The connection end portion of each electrode connected to the heating element has a center portion in the main scanning direction extending toward the centroid of the heating element as compared to both end portions. head.   The temperature gradient from the centroid to the outside of the heat generating element is greater between the centroid and the center of the connection end in the main scanning direction than between the centroid and both ends of the connection end in the main scanning direction. The thermal head according to claim 6, wherein the distance between is smaller.   8. The thermal head according to claim 6, wherein the connection end portion of each electrode has a circular arc shape convex toward the heat generating element in a plan view. The thermal head according to any one of claims 1 to 8,
Conveying means for conveying the recording medium onto the heating element of the thermal head;
A thermal printer comprising: a driving unit that is electrically connected to the connection terminal of the thermal head and selectively generates heat from the heating element.

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