JP2020032607A - Thermal head and thermal printer - Google Patents

Abstract

To provide a thermal head which enhances abrasion resistance of an outermost surface and improves reliability of a protective film, and a thermal printer using the same.SOLUTION: A thermal head X1 includes a substrate 7, a heating part 9, electrodes 17, 19, and a protective layer 25. The heating part 9 is positioned on the substrate 7. The electrodes 17, 19 are positioned above the substrate 7, and are connected to the heating part 9. The first protective layer 25a partially covers the heating part 9 and the electrodes 17, 19. The second protective layer 25b is positioned on the first protective layer 25a. The first protective layer 25a contains first crystal particles. The second protective layer 25b contains second crystal particles, and an average crystal grain size of the second crystal particle is larger than an average crystal grain size of the first crystal particle.SELECTED DRAWING: Figure 4

Description

  The present disclosure relates to a thermal head and a thermal printer.

  Conventionally, various thermal heads have been proposed as printing devices such as facsimile machines and video printers. For example, a substrate, a heating unit located on the substrate, an electrode located on the substrate, connected to the heating unit, a first protective layer covering a part of the heating unit and the electrode, And a second protective layer located on the first protective layer (see Patent Document 1).

Japanese Utility Model Publication No. 8-1155

  A thermal head according to an embodiment of the present disclosure includes a substrate, a heating unit, an electrode, a first protective layer, and a second protective layer. The heating section is located on the substrate. The electrodes are located on the substrate and are connected to the heat generating part. The first protective layer covers a part of the heating part and the electrode. The second protective layer is located on the first protective layer. The first protective layer includes first crystal grains. The average crystal particle size of the second crystal particles including the second crystal particles is larger than the average crystal particle size of the first crystal particles.

  A thermal printer according to an embodiment of the present disclosure includes the thermal head described above, a transport mechanism that transports a recording medium onto the heat generating unit, and a platen roller that presses the recording medium.

FIG. 1 is an exploded perspective view schematically showing a thermal head according to the first embodiment. FIG. 2 is a plan view schematically showing the thermal head shown in FIG. FIG. 3 is a sectional view taken along line III-III of FIG. FIG. 4 is an enlarged sectional view showing the vicinity of the protective layer of the thermal head shown in FIG. FIG. 5 is a schematic diagram illustrating the thermal printer according to the first embodiment.

  In order to improve the reliability of a protective layer, a conventional thermal head includes a first protective layer that covers a part of a heating portion and an electrode, and a second protective layer that is located on the first protective layer. It has been known. Recently, further improvement in the reliability of the protective layer is required.

  The thermal head of the present disclosure can improve the reliability of the protective layer. Hereinafter, the thermal head of the present disclosure and a thermal printer using the same will be described in detail.

<First embodiment>
The thermal head X1 will be described with reference to FIGS. FIG. 1 schematically shows the configuration of the thermal head X1. FIG. 2 shows the protective layer 25, the covering layer 27, and the sealing member 12 by dashed lines, and the covering member 29 by dashed lines. FIG. 3 is a sectional view taken along line III-III of FIG. 3, the layer structure of the protective layer 25 is omitted. FIG. 4 shows an enlarged view of the vicinity of the protective layer 25 of the thermal head X1.

  The thermal head X1 includes a head base 3, a connector 31, a sealing member 12, a heat sink 1, and an adhesive member 14. In addition, the connector 31, the sealing member 12, the heat sink 1, and the adhesive member 14 do not necessarily have to be provided.

  The heat radiating plate 1 radiates excess heat of the head base 3. The head base 3 is placed on the heat sink 1 via an adhesive member 14. The head substrate 3 prints on the recording medium P (see FIG. 5) when a voltage is applied from the outside. The bonding member 14 bonds the head base 3 and the heat sink 1. The connector 31 electrically connects the head base 3 to the outside. The connector 31 has the connector pins 8 and the housing 10. The sealing member 12 joins the connector 31 and the head base 3.

  The heat sink 1 has a rectangular parallelepiped shape. The heat radiating plate 1 is made of, for example, a metal material such as copper, iron, or aluminum, and radiates heat that does not contribute to printing, out of the heat generated in the heat generating portion 9 of the head base 3.

  The head base 3 has a rectangular shape in a plan view, and the members constituting the thermal head X1 are arranged on the substrate 7. The head base 3 has a function of printing on the recording medium P in accordance with an electric signal supplied from the outside.

  The components constituting the head base 3, the sealing member 12, the adhesive member 14, and the connector 31 will be described with reference to FIGS.

  The head base 3 includes a substrate 7, a heat storage layer 13, an electric resistance layer 15, a common electrode 17, an individual electrode 19, a first connection electrode 21, a connection terminal 2, a conductive member 23, a driving IC ( An integrated circuit (11), a covering member 29, a protective layer 25, and a covering layer 27 are provided. Note that all of these members do not necessarily have to be provided. Further, the head base 3 may include other members. The protection layer 25 is a general term for a first protection layer 25a and a second protection layer 25b described later.

  The substrate 7 is arranged on the heat sink 1 and has a rectangular shape in plan view. The substrate 7 has a first surface 7f, a second surface 7g, and a side surface 7e. The first surface 7f has a first long side 7a, a second long side 7b, a first short side 7c, and a second short side 7d. Each member constituting the head base 3 is arranged on the first surface 7f. The second surface 7g is located on the opposite side of the first surface 7f. The second surface 7g is located on the heat sink 1 side, and is joined to the heat sink 1 via the adhesive member 14. The side surface 7e connects the first surface 7f and the second surface 7g, and is located on the second long side 7b side.

  The substrate 7 is formed of, for example, an electrically insulating material such as alumina ceramics or a semiconductor material such as single crystal silicon.

  The heat storage layer 13 is located on the first surface 7f of the substrate 7. The heat storage layer 13 protrudes upward from the first surface 7f. In other words, the heat storage layer 13 protrudes in a direction away from the first surface 7f of the substrate 7.

  The heat storage layer 13 is arranged adjacent to the first long side 7a of the substrate 7, and extends along the main scanning direction. Since the cross section of the heat storage layer 13 is substantially semi-elliptical, the protective layer 25 formed on the heat generating portion 9 is in good contact with the recording medium P to be printed. The height of the heat storage layer 13 from the first surface 7f of the substrate 7 is, for example, 30 to 60 μm.

  The heat storage layer 13 is formed of glass having low thermal conductivity, and temporarily stores a part of the heat generated in the heat generating unit 9. Therefore, the time required to raise the temperature of the heat generating portion 9 can be shortened, and the thermal response characteristics of the thermal head X1 can be improved.

  The heat storage layer 13 is formed by, for example, applying a predetermined glass paste obtained by mixing a suitable organic solvent to glass powder on the first surface 7f of the substrate 7 by screen printing or the like, and baking this.

  The electric resistance layer 15 is located on the upper surface of the heat storage layer 13, and the common electrode 17, the individual electrode 19, the first connection electrode 21, and the second connection electrode 26 are formed on the electric resistance layer 15. An exposed region where the electric resistance layer 15 is exposed is formed between the common electrode 17 and the individual electrode 19. The exposed regions of the electric resistance layer 15 are arranged in a row on the heat storage layer 13 as shown in FIG. 2, and each exposed region constitutes the heat generating portion 9.

  Note that the electric resistance layer 15 does not necessarily need to be located between the various electrodes and the heat storage layer 13. For example, the electric resistance layer 15 is electrically connected to the common electrode 17 and the individual electrode 19. 19 may be located only.

  The plurality of heat generating portions 9 are simplified in FIG. 2 for convenience of description, but are arranged at a density of, for example, 100 dpi to 2400 dpi (dot per inch). The electric resistance layer 15 is formed of a material having a relatively high electric resistance such as, for example, TaN, TaSiO, TaSiNO, TiSiO, TiSiCO, or NbSiO. Therefore, when a voltage is applied to the heat generating portion 9, the heat generating portion 9 generates heat by Joule heat.

  The common electrode 17 includes main wiring portions 17a and 17d, a sub wiring portion 17b, and a lead portion 17c. The common electrode 17 electrically connects the plurality of heat generating portions 9 and the connector 31. The main wiring portion 17a extends along the first long side 7a of the substrate 7. The sub wiring portion 17b extends along each of the first short side 7c and the second short side 7d of the substrate 7. The lead portions 17c individually extend from the main wiring portion 17a toward the respective heat generating portions 9. The main wiring portion 17d extends along the second long side 7b of the substrate 7.

  The plurality of individual electrodes 19 electrically connect the heating section 9 and the driving IC 11. Further, the plurality of heat generating units 9 are divided into a plurality of groups, and the heat generating units 9 of each group and the driving ICs 11 arranged corresponding to each group are electrically connected by the individual electrodes 19.

  The plurality of first connection electrodes 21 electrically connect the drive IC 11 and the connector 31. The plurality of first connection electrodes 21 connected to each drive IC 11 are configured by a plurality of wirings having different functions.

  The plurality of second connection electrodes 26 electrically connect adjacent drive ICs 11. The plurality of second connection electrodes 26 are configured by a plurality of wirings having different functions.

  The common electrode 17, the individual electrode 19, the first connection electrode 21, and the second connection electrode 26 are formed of a conductive material. For example, any one of aluminum, gold, silver, and copper is used. Of these metals or their alloys.

  The plurality of connection terminals 2 are arranged on the second long side 7b side of the first surface 7f in order to connect the common electrode 17 and the first connection electrode 21 to the FPC 5. The connection terminals 2 are arranged corresponding to connector pins 8 of a connector 31 described later.

  A conductive member 23 is provided on each connection terminal 2. Examples of the conductive member 23 include solder and ACP (Anisotropic Conductive Paste). Note that a plating layer of Ni, Au, or Pd may be disposed between the conductive member 23 and the connection terminal 2.

  The various electrodes constituting the head base 3 are formed by sequentially laminating a metal material layer such as Al, Au, or Ni on the heat storage layer 13 by a thin film forming technique such as a sputtering method. Form. Next, the laminate can be formed by processing the laminate into a predetermined pattern using a technique such as photoetching. The various electrodes constituting the head base 3 can be simultaneously formed by the same process.

  As shown in FIG. 2, the drive ICs 11 are arranged corresponding to each group of the plurality of heat generating units 9. The drive IC 11 is connected to the individual electrodes 19 and the first connection electrodes 21. The drive IC 11 has a function of controlling the energization state of each heating unit 9. As the driving IC 11, a switching IC can be used.

  The protection layer 25 covers a part of the heat generating portion 9, the common electrode 17 and the individual electrode 19. The protective layer 25 protects the covered area from corrosion due to adhesion of moisture or the like contained in the air or abrasion due to contact with the recording medium P to be printed.

  The coating layer 27 is disposed on the substrate 7 so as to partially cover the common electrode 17, the individual electrodes 19, the first connection electrodes 21, and the second connection electrodes 26. The coating layer 27 is for protecting the coated region from oxidation due to contact with the air or corrosion due to adhesion of moisture or the like contained in the air. The coating layer 27 can be formed of a resin material such as an epoxy resin, a polyimide resin, or a silicone resin.

  The drive IC 11 is connected to the individual electrode 19, the first connection electrode 21, and the second connection electrode 26 and is sealed by a covering member 29 made of a resin such as an epoxy resin or a silicone resin. The covering member 29 is arranged so as to extend in the main scanning direction, and integrally seals the plurality of drive ICs 11.

  The connector 31 has a plurality of connector pins 8 and a housing 10 that houses the plurality of connector pins 8. The plurality of connector pins 8 have a first end and a second end. A first end is exposed to the outside of the housing 10, and a second end is housed inside the housing 10 and is drawn out. The first end of the connector pin 8 is electrically connected to the connection terminal 2 of the head base 3. Thereby, the connector 31 is electrically connected to various electrodes of the head base 3.

  The sealing member 12 has a first sealing member 12a and a second sealing member 12b. The first sealing member 12a is located on the first surface 7f of the substrate 7. The first sealing member 12a seals the connector pins 8 and various electrodes. The second sealing member 12b is located on the second surface 7g of the substrate 7. The second sealing member 12b is arranged to seal a contact portion between the connector pin 8 and the substrate 7.

  The sealing member 12 is arranged so that the connection terminals 2 and the first ends of the connector pins 8 are not exposed to the outside. For example, an epoxy-based thermosetting resin, an ultraviolet-curable resin, or visible light is used. It can be formed of a curable resin. Note that the first sealing member 12a and the second sealing member 12b may be formed of the same material. Further, the first sealing member 12a and the second sealing member 12b may be formed of different materials.

  The adhesive member 14 is disposed on the heat sink 1 and joins the second surface 7 g of the head base 3 to the heat sink 1. Examples of the adhesive member 14 include a double-sided tape or a resinous adhesive.

  The protective layer 25 will be described in detail with reference to FIG.

  The protection layer 25 includes a first protection layer 25a and a second protection layer 25b. The first protective layer 25a is located on the substrate 7. More specifically, the first protective layer 25a covers the entire area of the heat generating portion 9. Further, the first protective layer 25a covers a part of the electrode as shown in FIG. More specifically, the first protective layer 25a covers the entire area of the main wiring portion 17a, a part of the sub-wiring portion 17b on the first long side 7a side, and the entire area of the lead portion 17c. The layer 25a covers a part of the individual electrode 19 on the heating section 9 side.

Examples of the first protective layer 25a include TiN, TiON, TiCrN, TiAlON, and the like. When TiN is used as the first protective layer 25a, for example, it can be set to contain 40 to 60 atomic% of Ti and 40 to 60 atomic% of N. The first protective layer 25a is, for example, ^SiN, SiON, SiO 2, SiAlON, or in SiC. Hereinafter, a description will be given based on an example in which the first protective layer 25a is formed of TiN.

  The first protective layer 25a includes first crystal grains. In this example, the first crystal particles are TiN. The average crystal grain size of the first crystal grains is, for example, 80 to 240 nm. The standard deviation of the average crystal grain size of the first crystal grains is, for example, 73 to 120 nm.

  The thickness of the first protective layer 25a can be set to 2 to 6 μm. By setting the thickness of the first protective layer 25a to 2 μm or more, the adhesion between the heat generating portion 9 and the electrode is improved. Further, by setting the thickness of the first protective layer 25a to 6 μm or less, the heat of the heat generating portion 9 is easily transmitted to the recording medium P, and the thermal efficiency of the thermal head X1 is improved.

  The arithmetic surface roughness Ra of the first protective layer 25a is, for example, 30.0 nm or less. Thereby, adhesion with the second protective layer 25b provided on the first protective layer 25a is improved.

  The second protective layer 25b may be formed of the same material as the first protective layer 25a. That is, when the first protective layer 25a is formed of TiN, the second protective layer 25b may also be formed of TiN. Further, the second protective layer 25b may be formed of a material different from that of the first protective layer 25a. Hereinafter, a description will be given based on an example in which the second protective layer 25b is also formed of TiN.

  Second protective layer 25b includes second crystal grains. In this example, the second crystal particles are TiN. The average crystal grain size of the second crystal grains is, for example, 240 to 720 nm. The standard deviation of the average crystal grain size of the second crystal grains is, for example, 220 to 360 nm.

  The thickness of the second protective layer 25b can be set to 2 to 6 μm. By setting the thickness of the second protective layer 25b to 2 μm or more, wear resistance is improved. Further, by setting the thickness of the second protective layer 25b to 6 μm or less, the heat of the heat generating portion 9 is easily transmitted to the recording medium P, and the thermal efficiency of the thermal head X1 is improved. The second protective layer 25b corresponds to the outermost layer and is in contact with the recording medium P.

The arithmetic surface roughness Ra of the second protective layer 25b is, for example, 67.7 nm or less. Thereby, the contact area between the second protective layer 25b and the recording medium P can be reduced, and therefore, the frictional force generated between the second protective layer 25b and the recording medium P can be reduced. As a result, the wear resistance of the second protective layer 25b can be improved.

  In the thermal head X1, the average crystal grain size of the second crystal grains is larger than the average crystal grain size of the first crystal grains. Therefore, the reliability of the protective layer 25 is improved. Hereinafter, the details will be described.

  According to the above configuration, the second crystal particles having a relatively large particle size are located in the second protective layer 25b that comes into contact with the recording medium. As a result, the contact area per unit area between the grain boundary and the recording medium P is reduced, and the frictional force generated in the second protective layer 25b is reduced. Therefore, the second protective layer 25b is less likely to be worn, and the wear resistance of the protective layer 25 can be improved.

  Further, in the first protective layer 25a that covers the heat generating portion 9 and a part of the electrode, the first crystal particles having a relatively small particle size are located. As a result, the first crystal grains easily enter the fine concave portions formed on the surfaces of the heat generating portion 9 and the electrode, and the adhesion between the first protective layer 25a and the heat generating portion 9 and the electrode is improved. Thereby, the adhesion of the protective layer 25 is improved. From the above, the reliability of the protective layer 25 can be improved.

  Further, the average crystal grain size of the second crystal grains may be 240 to 720 nm. Thereby, the contact area per unit area between the grain boundary and the recording medium is further reduced, and the wear resistance of the second protective layer 25b is improved. Therefore, the reliability of the protective layer 25 is improved.

  Further, the average crystal grain size of the first crystal grains may be 80 to 240 nm. This makes it easier for the first crystal grains to enter fine concave portions formed on the surfaces of the heat generating portion 9 and the electrode, and the adhesion of the first protective layer 25a is improved. Therefore, the reliability of the protective layer 25 is improved.

  Further, the standard deviation of the average crystal particle diameter of the second crystal particles may be larger than the standard deviation of the average crystal particle diameter of the first crystal particles. Thereby, the reliability of the protective layer 25 is improved. This will be described in detail below.

  According to the above configuration, the second crystal grains of various sizes are located in the second protective layer 25b that comes into contact with the recording medium P. As a result, the second crystal particles having a large particle diameter support the recording medium P, and the second crystal particles having a small particle diameter can make the second protective layer 25b dense. That is, the second protective layer 25b is mainly composed of the second crystal particles having a large particle diameter, and the second crystal particles having a small particle diameter are located between the particles of the second crystal particles having a large particle diameter. The second protective layer 25b can be made dense. Therefore, the wear resistance of the second protective layer 25b is improved.

  When the standard deviation of the average crystal grain size of the first crystal grains is smaller than the standard deviation of the average crystal grain size of the second crystal grains, the heat generation portion 9 and the first protective layer 25a that covers a part of the electrode are formed. The first crystal particles having relatively uniform particle diameters are located. As a result, the first crystal particles easily enter into the fine recesses formed on the surfaces of the heat generating portion 9 and the electrode, and the adhesion of the first protective layer 25a is improved. From the above, the reliability of the protective layer 25 can be improved.

The average crystal grain size of the second crystal grains can be confirmed, for example, by the following method. First, the surface of the second protective layer 25b is scanned with a scanning electron microscope (SEM: Scanning Electron).
(Microscope). Subsequently, the second crystal particles are marked from the photographed surface photograph, image analysis is performed, and the particle size data of the second crystal particles is measured. In this specification, the average crystal grain size means a median diameter (d50). The standard deviation of the average crystal grain size can be calculated based on the crystal grain size data.

  The average crystal grain size of the first crystal grains is determined by removing the second protective layer 25b by polishing or cutting, exposing the first protective layer 25a, and exposing the exposed surface of the first protective layer 25a using SEM. Shoot. Hereinafter, the description is omitted because it is the same as the second crystal particle.

  Further, the value of the thickness of the second protective layer 25b may be larger than the value of the thickness of the first protective layer 25a. Thereby, the abrasion resistance of the protective layer 25 is improved due to the large thickness of the second protective layer 25b in contact with the recording medium P. Further, since the thickness of the first protective layer 25a is small, the heat of the heat generating portion 9 can be efficiently transferred to the second protective layer 25b, and the thermal efficiency of the thermal head X1 can be improved.

  Furthermore, the second protective layer 25b has a configuration in which heat conduction is easier than that of the first protective layer 25a because the average crystal grain size is larger than that of the first protective layer 25a. That is, the second protective layer 25b has a large average crystal grain size, crystals are grown in the thickness direction of the protective layer 25, and heat conduction is easy. Therefore, even if the thickness of the second protective layer 25b increases, heat can be efficiently transmitted to the recording medium P.

  The thicknesses of the first protective layer 25a and the second protective layer 25b are measured from the cut surface of the thermal head X1 cut in the thickness direction.

  Further, the value of the calculated surface roughness of the second protective layer 25b may be larger than the value of the arithmetic surface roughness of the first protective layer 25a. Thereby, in the second protective layer 25b that comes into contact with the recording medium P, the value of the arithmetic surface roughness is large, so that the contact area between the second protective layer 25b and the recording medium P is reduced. As a result, so-called sticking that the recording medium P sticks to the second protective layer 25b is less likely to occur.

  Further, in the first protective layer 25a that covers a part of the heat generating portion 9 and the electrode, the contact area between the heat generating portion 9 and the electrode and the first protective layer 25a increases because the arithmetic surface roughness value is small. Thus, the adhesion of the protective layer 25 is improved.

  In addition, the arithmetic surface roughness Ra is measured using an atomic force microscope (AFM: Atomic Force Microscope). Further, a contact type or non-contact type surface roughness meter may be used.

  The protective layer 25 can be formed by arc plasma ion plating or hollow cathode ion plating.

  The control of the average crystal grain size of the first crystal particles and the second crystal particles can be controlled, for example, by the following method. For example, when the protective layer 25 is formed by the arc plasma ion plating method, the absolute value of the substrate bias voltage applied when the second protective layer 25b is formed may be smaller than when the first protective layer 25a is formed. I just need. Further, the film forming pressure at the time of forming the second protective layer 25b may be set higher than that at the time of forming the first protective layer 25a. The temperature at the time of forming the second protective layer 25b may be higher than that at the time of forming the first protective layer 25a.

  Next, a thermal printer Z1 having a thermal head X1 will be described with reference to FIG.

The thermal printer Z1 of the present embodiment includes the above-described thermal head X1, the transport mechanism 40, a platen roller 50, a power supply device 60, and a control device 70. The thermal head X1 is mounted on a mounting surface 80a of a mounting member 80 disposed on a housing (not shown) of the thermal printer Z1. The thermal head X1 is attached to the attachment member 80 along a main scanning direction which is a direction orthogonal to the transport direction S.

  The transport mechanism 40 includes a drive unit (not shown) and transport rollers 43, 45, 47, and 49. The transport mechanism 40 transports the recording medium P such as thermal paper, image receiving paper or the like onto which ink is transferred in the direction of arrow S in FIG. 5 and places the recording medium P on the protective layer 25 located on the plurality of heat generating portions 9 of the thermal head X1. It is for carrying. The drive unit has a function of driving the transport rollers 43, 45, 47, and 49, and may use, for example, a motor. The transport rollers 43, 45, 47 and 49 cover, for example, cylindrical shafts 43a, 45a, 47a and 49a made of metal such as stainless steel with elastic members 43b, 45b, 47b and 49b made of butadiene rubber or the like. Can be configured. When the recording medium P is an image receiving paper to which ink is transferred, an ink film (not shown) is transported together with the recording medium P between the recording medium P and the heating section 9 of the thermal head X1.

  The platen roller 50 has a function of pressing the recording medium P onto the protective layer 25 located on the heating section 9 of the thermal head X1. The platen roller 50 is disposed so as to extend along a direction orthogonal to the transport direction S, and both ends are supported and fixed so that the platen roller 50 can rotate while pressing the recording medium P on the heat generating unit 9. The platen roller 50 can be configured by, for example, covering a cylindrical shaft body 50a made of metal such as stainless steel with an elastic member 50b made of butadiene rubber or the like.

  The power supply device 60 has a function of supplying a current for causing the heating section 9 of the thermal head X1 to generate heat and a current for operating the drive IC 11 as described above. The control device 70 has a function of supplying a control signal for controlling the operation of the drive IC 11 to the drive IC 11 in order to selectively heat the heat generating portion 9 of the thermal head X1 as described above.

  The thermal printer Z1 presses the recording medium P onto the heat generating portion 9 of the thermal head X1 with the platen roller 50, and conveys the recording medium P onto the heat generating portion 9 with the conveying mechanism 40. By causing the heat generating section 9 to selectively generate heat, predetermined printing is performed on the recording medium P. When the recording medium P is an image receiving paper or the like, printing on the recording medium P is performed by thermally transferring the ink of an ink film (not shown) conveyed together with the recording medium P onto the recording medium P.

  Note that cut paper may be used as the recording medium P. Each time the cut paper is conveyed, the rear end of the cut paper is beaten to the second protective layer 25b. However, in the thermal head X1, the average crystal grain size of the second crystal particles is equal to the first crystal size. Since it is larger than the average crystal grain size of the particles, the wear resistance of the second protective layer 25b is improved. Therefore, the reliability of the protective layer 25 is improved, and a thermal printer Z1 with improved reliability can be obtained.

  As described above, the thermal head according to the present disclosure is not limited to the above embodiment, and various changes can be made without departing from the gist of the thermal head. For example, although a thin film head having a thin heating portion 9 in which the electric resistance layer 15 is formed by a thin film is illustrated, the invention is not limited to this. A thick film head having a large heating portion 9 in which the electric resistance layer 15 is formed of a thick film after patterning various electrodes may be used.

  Further, although the flat head in which the heat generating portion 9 is formed on the first surface 7f of the substrate 7 has been described as an example, an end surface head in which the heat generating portion 9 is located on the end surface of the substrate 7 may be used.

  Further, the heat generating portion 9 may be formed by forming the common electrode 17 and the individual electrode 19 on the heat storage layer 13 and forming the electric resistance layer 15 only in a region between the common electrode 17 and the individual electrode 19. .

  Further, the sealing member 12 may be formed of the same material as the covering member 29 that covers the drive IC 11. In this case, when the covering member 29 is printed, printing may also be performed on the region where the sealing member 12 is formed, so that the covering member 29 and the sealing member 12 may be simultaneously formed.

  Although the example in which the connector 31 is directly connected to the substrate 7 has been described, a flexible printed circuit (FPC: Flexible printed circuits) may be connected to the substrate 7.

X1 Thermal head Z1 Thermal printer 1 Heat sink 3 Head base 7 Substrate 9 Heating section 11 Drive IC
DESCRIPTION OF SYMBOLS 12 Sealing member 13 Thermal storage layer 14 Adhesive member 15 Electric resistance layer 17 Common electrode 19 Individual electrode 21 First connection electrode 25 Protective layer
25a first protective layer 25b second protective layer 26 second connection electrode 27 coating layer 31 connector

Claims (8)

Board and
A heating unit located on the substrate,
An electrode located on the substrate and connected to the heat generating portion;
A first protective layer covering a part of the heating unit and the electrode;
A second protective layer located on the first protective layer,
The first protective layer includes first crystal grains,
The second protective layer includes second crystal grains,
A thermal head, wherein the average crystal particle diameter of the second crystal particles is larger than the average crystal particle diameter of the first crystal particles.   2. The thermal head according to claim 1, wherein an average crystal grain size of the second crystal grains is 240 nm to 720 nm. 3.   The thermal head according to claim 2, wherein the first crystal particles have an average crystal particle size of 80 nm to 240 nm.   The thermal head according to any one of claims 1 to 3, wherein a standard deviation of an average crystal grain size of the second crystal particles is larger than a standard deviation of an average crystal grain size of the first crystal particles.   The thermal head according to claim 1, wherein a value of the thickness of the second protective layer is larger than a value of the thickness of the first protective layer.   The thermal head according to claim 1, wherein a value of a calculated surface roughness of the second protective layer is larger than a value of an arithmetic surface roughness of the first protective layer. A thermal head according to any one of claims 1 to 6,
A transport mechanism for transporting the recording medium onto the heating unit,
A thermal printer, comprising: a platen roller that presses the recording medium. The thermal printer according to claim 7, wherein the recording medium is a cut sheet.

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