JP4969600B2 - Thermal print head - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal print head used in a printing apparatus such as a thermal printer, and more particularly to a thermal print head that facilitates high-speed and low-cost operation in image formation of a printer or the like and good halftone recording. .

  The thermal print head is an output device that uses the heat generated by the heat generating portion to form an image made up of characters or the like by, for example, an ink ribbon thermal transfer method or a thermal recording method. It is widely used in recording devices such as barcode printers, weighing machines, digital plate-making machines, video printers, imagers, and seal printers. Generally, a thermal print head has a structure in which a resistor substrate portion provided with the heat generating portion and a drive circuit substrate portion mounted with a drive IC are arranged on one main surface of a heat dissipation substrate.

Here, an example of a conventional thermal print head will be described with reference to FIGS. FIG. 12 is a top view of a partially cut out part thereof, and FIG. 13 is a cross-sectional view in the direction (sub-scanning direction) in which the recording medium is viewed in the direction of arrows Z ₅ -Z ₅ in FIG. A conventional thermal print head has a structure that extends to a required length along a direction (main scanning direction) orthogonal to the sub-scanning direction, and a large number of heat generating portions are arranged in a line in the main scanning direction. ing.

  As shown in FIGS. 12 and 13, in the thermal print head, for example, a resistor substrate portion 102 </ b> A and a drive circuit substrate portion 102 </ b> B are provided adjacent to each other on the main surface of the heat dissipation substrate 101. In the resistor substrate portion 102A, the support substrate 103 is adhered on the main surface of the heat dissipation substrate 101, and the glaze layer 104 serving as a heat retaining layer extends on the support substrate 103 in the main scanning direction of the head so as to be integrated. Is provided.

  Then, the heating resistor 105 is formed so as to cover the surface of the glaze layer 104, and the common electrode 106 a and the individual electrode 106 b are arranged on the heating resistor 105 to face each other with the gap G interposed therebetween. Here, the pair of electrodes 106 including the common electrode 106 a and the individual electrodes 106 b are layered on the heating resistor 105 to be electrically connected. The heating resistor exposed in the gap G becomes the heating portion 107.

  As shown in the figure, the pair of electrodes 106 which are energization electrodes of the heat generating portion 107 and the heat generating portion 107 form one heat generating element, and have a required pitch (dpi: dots / inch) in the main scanning direction of the thermal print head. The heating element array is formed in one row. Further, the edge portion of the first electrode 106b is exposed and is entirely covered with the protective layer 108 for bonding wire connection described later.

  On the other hand, the drive circuit board portion 102B includes a drive circuit board 109 and the like attached to the heat dissipation board 101, a circuit pattern (not shown) and the like are formed on the surface of the board, and a drive IC 110 and the like are mounted. A bonding wire W is used to electrically connect the energizing electrode of the resistor substrate portion 102A and the drive IC 110 of the drive circuit substrate portion 102B and between the drive IC 110 and the circuit pattern of the drive circuit substrate portion 102B. It is connected. These bonding wires W and the driving IC 110 are hermetically sealed by a sealing material 111 made of, for example, an epoxy resin.

  In image formation on a recording medium using the thermal print head, a thermal recording paper, a thermal transfer ink ribbon, or the like (not shown) is sandwiched between a protective layer 108 on a heating portion 107 area and a so-called platen roller, Step conveyance is performed at a predetermined speed in the sub-scanning direction. Then, the ink ribbon or the thermal paper is heated by the heat generating portion 107 that generates heat by energizing the rectangular pulse voltage, and printing or overcoat processing is performed by the heat. In the operation of such a thermal printer, the heat generated by the heat generating portion 107 receives moderate heat storage and heat dissipation by the glaze layer 104. The protective layer 108 is slidably contacted with thermal paper or the like without interruption.

  A thermal print head having the above-described configuration is described in Patent Document 1 and the like.

JP 2005-262828 A

  Normally, in the printing operation of a thermal printer, when printing is performed by one heat generating element, the heat generation causes the temperature of the heat generating portion and the surrounding glaze layer 104 to rise and store heat. Then, in the next printing following the printing of one heating element, if the heat generation in the heat generating part or the adjacent heat generating part remains insufficient, the printing point breakage deteriorates and blurring of image quality in the sub-scanning direction becomes obvious. And become visible. For this reason, in order to increase the speed of the thermal printer operation, particularly high thermal history control of the glaze layer 104 is essential. For example, it is required to control the printing operation after step conveyance with high accuracy based on the heat history of how much each heating element in one row generates heat before step conveyance. The drive circuit and control circuit including the drive IC 110 are required to have high performance, and the increase in cost is inevitable.

  Further, when the speed of the thermal printer is increased, uneven conveyance in printing tends to occur due to high-speed step conveyance in the sub-scanning direction such as thermal recording paper and thermal transfer ink ribbon. Therefore, it is essential to increase the capacity and performance of the transport step motor and the like, and it is necessary to increase the size of the control mechanism and power supply. For this reason, it is difficult to reduce the cost, size and weight of the thermal printer.

  Further, in the step conveyance, the protective layer 108 receives the sliding contact of the thermal paper or the like without interruption. For this reason, in order to increase the speed of the thermal printer operation, the protective layer on the heat generating portion sandwiched between the platen roller is easily worn and the life of the thermal print head is shortened.

  In addition, for example, in a facsimile apparatus or an apparatus for printing a color photograph such as a print club (trade name) or business print (such as a kiosk terminal), control of gradation or tone of image formation is also pursued.

  The present invention has been made in view of the above-described circumstances, and simply solves the above-described problems caused by the speeding up of image formation, speeding up the operation of the printing apparatus such as a thermal printer, and reducing the speed thereof. It is an object of the present invention to provide a thermal print head that can be easily reduced in cost, can express gradation with one dot, and can record a good halftone image.

In order to achieve the above object, a thermal print head according to the present invention includes a support substrate, a heat insulating layer formed of an insulator formed on the surface of the support substrate, and a heating resistor formed on the heat insulating layer. A plurality of heat generating portions, a first electrode that energizes the heat generating portions and is electrically connected to the heat generating resistor to define a region, and is electrically connected to the heat generating resistor at a central portion of the one region. Printing apparatus comprising a pair of electrodes composed of a second electrode and a protective layer formed on the heat generating portion and the pair of electrodes, and performing a printing process or an overcoat process after the printing process on a recording medium in thermal print heads for use in, the annular portion consists projecting from the annular portion in a predetermined position of the first electrode layer electrodes is disposed on the surface of the insulation layer between the electrode layer is the covering the electrode layer Through the first insulating layer, the first insulator layer and the same plane to form the first insulating layer, the heating resistor formed on a surface of the first insulator layer The annular portion of the first electrode is electrically connected to the lower surface side of the heating resistor to define the one region to form the heating portion, and the second electrode is The second insulating portion has a columnar portion, and the columnar portion penetrates the second insulator layer covering the heating resistor and is electrically connected to a central portion of the heating portion on the upper surface side of the heating resistor. It is arranged on the surface of the body layer, and the heat generating part is arranged in a two-dimensional array on the heat insulating layer.

  With the configuration of the present invention, it is easy to increase the operation speed and reduce the cost of image formation of a printing apparatus such as a thermal printer. Moreover, gradation can be expressed for each dot, and a good halftone image can be recorded.

Is a diagram showing the resistor substrate portion heating part of the thermal print head according to the first embodiment are arranged in the present invention, (a) shows the partial top view, (b) is Z ₁ in (a) - enlarged sectional view of the Z ₁ arrow. Sectional drawing according to manufacturing process which shows an example of the manufacturing method of the thermal print head concerning the 1st Embodiment of this invention. Sectional drawing according to manufacturing process which shows the manufacturing process of the thermal print head following FIG. The conceptual diagram with which it uses for description of the gradation expression of one heat generating element of the thermal print head concerning embodiment of this invention. Is a diagram showing a second embodiment resistor substrate portion heating part of the thermal print head are arranged according to the embodiment of the present invention, (a) is a partial top view, (b) is Z ₂ in (a) - enlarged sectional view of the Z ₂ arrow. Sectional drawing according to manufacturing process which shows an example of the manufacturing method of the thermal print head concerning the 2nd Embodiment of this invention. 3 is a diagram showing a resistor substrate portion heating unit are arranged in the thermal print head according to the embodiment of, (a) shows the partial top view of the present invention, (b) is Z ₃ of (a) - Z3 is an enlarged sectional view taken in the direction of arrow ₃ . Sectional drawing according to manufacturing process which shows an example of the manufacturing method of the thermal print head concerning the 3rd Embodiment of this invention. 4 is a diagram heat generating portion indicates the resistor substrate portions arranged thermal print head according to the embodiment of, (a) shows the partial top view of the present invention, (b) is Z ₄ of (a) - Z is an enlarged sectional view taken in the direction of arrow ₄ . Sectional drawing according to manufacturing process which shows an example of the manufacturing method of the thermal print head concerning the 4th Embodiment of this invention. The top view which shows the modification of the electrode structure in the thermal print head concerning embodiment of this invention. The partially cut-out top view which extracted a part of thermal print head in a prior art. Enlarged sectional view of the _Z 5 -Z ₅ arrow in FIG.

Several preferred embodiments of the present invention will be described below with reference to the drawings. Here, parts that are the same or similar to each other are denoted by common reference numerals, and a duplicate description is partially omitted. However, the drawings are schematic and ratios of dimensions and the like are different from actual ones.
(First embodiment)
A thermal print head according to a first embodiment of the present invention will be described with reference to FIG. Here, FIG. 1 is a view showing an example of a resistor substrate portion of the thermal print head according to the present embodiment, where (a) is a partial top view, and (b) is an enlarged view of the Z ₁ -Z ₁ arrow. It is sectional drawing.

  As shown in FIG. 1, a support substrate 11 having good heat resistance and thermal conductivity, such as ceramics, is stuck on the main surface of the heat dissipation substrate in the same manner as described in the prior art, and a heat insulating layer is formed on the upper surface. A glaze layer 12 is provided. A common electrode 13 is formed on the surface of the glaze layer 12. Here, the common electrode 13 has a single-layer electrode layer having a predetermined width as shown by the broken line in FIG. 1A, and is arranged to extend in the X direction which is the main scanning direction of the thermal print head. Yes.

  A heating resistor 15 made of, for example, a cermet having a planar circular shape is disposed on the first interlayer insulating layer 14 formed so as to cover the electrode layer of the common electrode 13, and the column-shaped, for example, columnar common electrode end portion 13a is formed. The electrode layer protrudes from the predetermined portion of the electrode layer so as to penetrate the first interlayer insulating layer 14 and the heating resistor 15. The central portion of the heating resistor 15 is electrically connected to the common electrode 13 through the common electrode end portion 13a. In addition, the individual electrode 16 is disposed on the first interlayer insulating layer 14, and, for example, an annular individual electrode end portion 16 a is electrically connected to the peripheral end surface of the heating resistor 15. The heating resistor 15 serves as a heat generating portion with the edge of the common electrode end portion 13a and the edge of the individual electrode end portion 16a as the edges of the energizing electrode.

  The heat generating resistor 15 serving as the heat generating portion described above, and the common electrode 13 and the individual electrode 16 which are a pair of electrodes for energization constitute one heat generating element. In this heat generating element, in the heat generating resistor 15, for example, the heat generating resistor 15 in contact with the common electrode end portion 13a is energized from the side wall side of the through hole to the end face side of the heat generating resistor 15 in contact with the individual electrode end portion 16a to generate heat. Occurs. In this embodiment, the individual electrode 16 is the first electrode of the pair of electrodes, and the common electrode 13 is the second electrode.

  Such heating elements are arranged at a required dpi in the X direction of the main scanning direction of the thermal print head to form a first column heating element array. Further, a plurality of such heating element arrays are arranged in parallel at a predetermined interval in the Y direction in the sub-scanning direction of the thermal print head. In this way, the heat generating portions of the heat generating elements are arranged in a plurality of rows in a line in the main scanning direction. FIG. 1 (a) shows a case where the first to fourth heating element arrays are formed in four rows in order from the front in the Y direction. It is appropriately set according to the operation speed of the printer, the heat storage / heat radiation characteristics of the glaze layer 12, and the like. Further, the arrangement of the heating element arrays may be slightly shifted in the X direction between columns.

  In the same manner as described in the prior art, the individual electrode pad portion 16b which is the electrode lead end portion of the individual electrode 16 is exposed and covered entirely with the protective layer 17 for bonding wire connection. Although not shown in FIG. 1A, the individual electrode pad portion 16b is wire-bonded to the drive IC 18.

In the thermal print head, the support substrate 11 is a substrate made of an insulating material having heat resistance, and is made of Si (silicon), quartz, SiC (silicon carbide) or the like in addition to alumina ceramics. The glaze layer 12 is an insulator film made of an insulator material having a surface smoothness and having an action of appropriate heat storage and heat dissipation of heat generated by the heating resistor 15. Examples of the glaze layer 12 include a SiO ₂ film (silicon oxide film), a SiON film (silicon oxynitride film), and a SiN film (silicon nitride film).

  The heating resistor 15 is made of, for example, a cermet film or a semiconductor film, which is a TaSiO, TaSiNO, NbSiO, TiSiCO based electric resistor material. The common electrode 13 and the individual electrode 16 are preferably as low in resistance as possible, and are composed mainly of metal such as Al (aluminum), Cu (copper), or AlCu alloy. The common electrode end portion 13 a may be made of the same metal material as the common electrode 13.

  Alternatively, the common electrode end portion 13a may be a high melting point such as Mo (molybdenum), W (tungsten), Ti (titanium), Cr (chromium), Ta (tantalum), Co (cobalt), Ni (nickel), etc. It may be made of metal or a refractory metal silicide thereof, or a conductive nitride of a refractory metal. Such a metal material can sufficiently cope with the case where the common electrode end portion 13a becomes high temperature due to current concentration during energization. Further, ruthenium (Ru), iridium (Ir), etc., which are conductive, can also be suitably used. With such a metal material, even if the common electrode end 13a is oxidized in the manufacturing process of the thermal print head, the electrical connection with the heating resistor 15 is guaranteed.

The first interlayer insulating layer 14 is made of an insulating material such as a SiO ₂ film, a SiON film, or a SiN film formed by, for example, a chemical vapor deposition (CVD) method or a sputtering method. Here, the first interlayer insulating layer 14 may be made of the same insulator material as the glaze layer 12.

Further, the protective layer 17 is made of a hard and dense insulating material such as a SiO ₂ film, a SiN film, a SiON film, or a SiC film. Here, when at least Si and carbon (C) are contained in the outermost surface of the protective layer 17, the thermal conductivity becomes high, which is preferable. The protective layer 17 has a function of covering the heating element arrays arranged in a plurality of rows and protecting the recording medium from abrasion due to pressure contact or sliding contact, and corrosion due to contact with moisture contained in the atmosphere.

  In the above-described thermal print head, the case of a so-called FG (Flat Glaze) structure in which the entire glaze layer 12 is flat has been described. The glaze layer 12 may have a so-called PEG structure in which a part thereof is formed by partial etching and has a raised portion. Or, conversely, the flat portion may have a PG structure formed in a band shape in the main scanning direction of the thermal print head.

  In the thermal print head, the common electrode end portion 13a or the individual electrode end portion 16a may be formed so as to be electrically connected even on the upper surface of the heating resistor 15. The common electrode 13 may be electrically connected so that some part of the columnar end portion 13 a is in contact with the center position of the heating resistor 15. The same applies to other embodiments described below.

  Next, an example of a method for manufacturing the thermal print head according to the first embodiment will be described with reference to FIGS. FIG. 2 is a cross-sectional view of the main manufacturing process when the resistor substrate portion of the thermal print head is cut out, and FIG. 3 is a cross-sectional view by manufacturing process showing the manufacturing process of the thermal print head following FIG.

First, an elongated support substrate 11 made of alumina and having a width of about several mm in the sub-scanning direction and a plate thickness of 0.5 mm to 1 mm is prepared. Then, as shown in FIG. 2 (a), a glass paste obtained by adding and mixing an appropriate organic solvent and solvent to the glass powder of SiO ₂ is applied and formed on the support substrate 11 and fired at an appropriate temperature. For example, the glaze layer 12 having a thickness of about 50 to 200 μm is formed.

Then, an electrode film such as an Al film or an AlCu alloy film having a film thickness of about 0.1 μm to 1 μm is formed on the surface of the glaze layer 12 by, for example, a sputtering method using a shadow mask to form a single electrode layer 13 is formed. Subsequently, the common electrode 13 is covered by a sputtering method to form, for example, a SiO ₂ film having a film thickness of about 0.5 μm to ₂ μm to form a first interlayer insulating layer 14.

  Next, a resist mask 20 having an opening pattern 19 is formed on the first interlayer insulating layer 14 by a known photolithography technique. Then, the first opening 21 having a diameter of, for example, about 2 μm to 20 μm is formed in the first interlayer insulating layer 14 by etching using the resist mask 20. Thereafter, as shown in FIG. 2B, the resist mask 20 is removed with a chemical solution or the like. Here, the first opening 21 formed by photolithography and etching (hereinafter referred to as a photoengraving process) as described above may be formed in a structure having an appropriate shape such as a circle or a polygon. .

  Next, as shown in FIG. 2C, a metal film 22 such as the same Al film or AlCu alloy film as the common electrode 13 is deposited on the entire surface so as to fill the first opening 21 by sputtering. Subsequently, the metal film 22 on the first interlayer insulating layer 14 is polished and removed by a chemical mechanical polishing (CMP) method using the first interlayer insulating layer 14 as a polishing stopper. In this way, as shown in FIG. 2D, the metal film 22 is embedded in the first opening 21 and electrically connected to the common electrode 13, and the common electrode end 13a having a diameter of about 2 μm to 20 μm is formed. It is formed.

  Next, as shown in FIG. 3A, a resistor made of a cermet material having a film thickness of about 0.1 μm to 1.0 μm on the first interlayer insulating layer 14 and the common electrode end 13a by, for example, sputtering. A film 23 is formed. Then, as shown in FIG. 3B, the resistor film 23 is patterned by a photoengraving process, and a planar circular heating resistor having a through hole 24 in the center and a diameter of, for example, about 20 μm to 150 μm. Form body 15.

  Next, a CMP method similar to that described in FIGS. 2C and 2D is used in combination, and the common electrode 13 is formed on the entire surface so as to be embedded between the through-hole 24 and the heating resistor 15 by a sputtering method. A metal film 25 such as the same Al film or AlCu alloy film is formed. Here, the surface of the heating resistor 15 is treated so that no electrode film remains. Then, the metal film 25 is patterned by a photoengraving process. In this way, the individual electrode 16 having the annular individual electrode end portion 16a that is electrically connected to the peripheral end face of the thermal resistor 15 shown in FIG. 3D is the first electrode as described in FIG. Arranged on the interlayer insulating layer 14. The metal film 25 embedded in the through hole 24 extends the above-described common electrode end portion 13a upward.

  Thereafter, the protective layer 17 described in FIG. 1 is formed by a sputtering method. Here, the protective layer 17 is deposited to a thickness of about 2 μm to 10 μm, for example. As described above, the resistor substrate portion of the thermal print head according to the present embodiment as described with reference to FIG. 1 is easily manufactured.

  As another manufacturing method of the thermal print head described above, for example, an electrode film 22 that fills the first opening 21 and adheres to the resist mask 20 in the state shown in FIG. Here, a film forming method that does not cover the side wall of the resist mask 21 is employed. As such a film forming method, for example, collimated sputtering or long throw sputtering, which is directional sputtering in the vertical direction, may be used. After such film formation, the resist mask 20 is removed in a chemical solution to remove the electrode film 22 on the resist mask 20 together. In this way, the common electrode end portion 13a may be formed in the first opening 21 by a so-called lift-off method. Further, the metal film 25 described with reference to FIG. 3C can also be easily formed by the lift-off method similar to that described above.

  The formation of the common electrode end portion 13a using the lift-off method described above is performed by using a refractory metal having a higher hardness than that of an Al-based metal film, a refractory metal silicide thereof, or a conductive nitride of a refractory metal. It is suitable for use.

  In image formation on a recording medium using the thermal print head of the above embodiment, the recording medium is brought into contact with the surface of the thermal print head, and a required pulse voltage is applied to each of a plurality of two-dimensionally arranged heating elements. Applied. In this thermal print head, the required number of heat generating portions simultaneously generate heat to form an image.

  When performing this simultaneous printing operation, a certain heat radiation time is taken after this simultaneous printing operation. This is to ensure sufficient heat dissipation of the heat generating portions and the glaze layer 12 that have generated a large amount of heat. After that, for example, when the thermal print head heads up from the platen roller, the contact state due to the clamping pressure with the platen roller is released. Then, the recording medium or the like is conveyed by a predetermined distance corresponding to a plurality of rows of heating element arrays in the sub-scanning direction. In this way, image formation and conveyance of printing or overcoat processing are repeated. In this case, a certain heat dissipation time is required when the recording medium is transported, but the entire printing operation is speeded up because the simultaneous printing operation is performed.

  Alternatively, in the image formation on the recording medium using the thermal print head, the thermal recording paper, the thermal transfer ink ribbon, etc. are arranged in a plurality of rows in the main scanning direction of the head and the protective layer 17 on the heat generating portion and the platen roller It is pinched between. Then, after a required heat generating portion on one column of the first row heating element array, for example, in the sub-scanning direction in the sub-scanning direction generates heat and prints, the next second row heating element array prints. In this way, the first column heating element array to the fourth column heating element array are sequentially printed in the sub-scanning direction. Here, the order of printing of the plurality of rows of heating element arrays can be determined as appropriate.

  Then, after the printing operation is performed in the all-row heating element array in the sub-scanning direction, the clamping state with the platen roller is released or the pressing force is reduced, for example, by head-up of the thermal print head. . Then, the recording medium or the like is conveyed by a predetermined distance corresponding to a plurality of rows of heating element arrays in the sub-scanning direction. In this way, image formation and conveyance of printing or overcoat processing are repeated.

  Next, gradation expression in image formation using the thermal print head of this embodiment will be described with reference to FIG. FIG. 4 is a conceptual diagram for explaining gradation expression of one heating element of the thermal print head according to the embodiment of the present invention. Here, the current distribution in the heat generating portion when a voltage is applied between the first electrode of the pair of electrodes energized in the heat generating portion of the heat generating element and the second electrode is shown. In the figure, the arrow is the current density i vector. However, this figure shows an example in which the individual electrode end portion 16a has an annular shape and a planar circular common electrode end portion 13a is disposed at the center thereof.

  In the thermal print head according to the present invention, the current distribution in the heat generating portion is biased due to the unique structure of the heat generating element. For example, in the printing of the heating element as described in the first embodiment, a current flows radially from the common electrode end portion 13a toward the individual electrode end portion 16a as shown in FIG. For this reason, the current density has a biased current distribution in which the vicinity of the common electrode end portion 13a is large, and the current density decreases as the distance from the common electrode end portion 16a approaches the individual electrode end portion 16a.

  Hereinafter, a general description of the bias of the current distribution will be given. Here, it is assumed that the resistance value of the heating resistor 15 does not change due to heat generation. Further, the heating resistor 15 is a thin film, and its thickness is ignored, and it is regarded as two-dimensional.

  Considering a state in which a constant voltage is applied to the common electrode end portion 13a and the individual electrode end portion 16a based on the above assumption, the current distribution in the heat generating portion is a steady current field. In a steady current field, an electric field based on a change in magnetic flux density with time is not generated. Moreover, there is no temporal change in charge. Therefore, the current density i satisfies the formula (1) from the law of charge conservation.

divi = 0 (1)
Further, when the conductivity σ and the electric field E are set according to Ohm's law, the equation (2) is established.
i = σE (2)
And (3) Formula is materialized from (1) Formula and (2) Formula. In addition, since an electric field based on a change in magnetic flux density with time is not generated, the electric field E is expressed by the equation (4) where φ is a potential distributed in the heat generating portion.
divE = 0 (3)
E = -gradφ (4)
Then, by substituting equation (4) into equation (3), a second-order variable differential equation of equation (5) is obtained.
∂ ² φ / ∂x ² + ∂ ² φ / ∂y ² = 0 (5)

  Then, by numerically analyzing the equation (5) using the boundary element method, the potential φ distributed in the heat generating portion can be obtained. Further, the electric field distribution in the heat generating portion can be obtained from the numerical calculation using the potential φ and the equation (4), and the current distribution in the heat generating portion can be calculated from the numerical calculation using the equation (2).

If the energy density En generated by the current in the heat generating part is assumed, the energy density En is expressed by the equation (6).
En = i · E = σE ² (6)
This energy density En is the heat generation energy at the point where the heat generation portion is present.

  From the above general description, it can be seen that in the thermal print head of the present invention, the current distribution has a high current density on the end portion side of the second electrode disposed in the central portion of the heat generating portion. Similarly, the heat generation energy at a point where the heat generating portion is present also increases on the end portion side of the second electrode. However, a part of the heat generated by the heat generation energy is lost due to heat conduction through the second electrode, heat radiation from the surface of the heat generating portion, and the like. Further, thermal diffusion occurs in the heat generating portion, and the amount of heat generated increases from the end of the second electrode to the end of the first electrode with time in the heat generating portion. For this reason, for example, when the applied voltage is a rectangular pulse voltage, the heat generation range having a required heat generation amount is, for example, from the range indicated by A of the heat generating portion in FIG. 4 as the pulse width (application time) increases. It extends to the range indicated by B and further to the range indicated by C.

  By the way, in order to form dots by melting / sublimating and transferring the ink of the ink ribbon to the recording medium, a required amount of heat generation of a certain amount or more is required. Accordingly, when the pulse width is small and the total heat generation energy is small, dots are formed in the heat generating portion by heat generation in the range indicated by A in FIG. 4 for example, and as the pulse width becomes longer, B and C are shown in the same figure. Dots are formed by heat generation in the range. As described above, in the thermal print head of the present invention, for example, by changing the pulse width, it is possible to easily perform printing with different dot areas in the heat generating portion of one heat generating element. Here, if the dot area increases, the density increases visually. As a result, gradation can be expressed in units of one dot. Similarly, even when the recording medium is a thermal recording type such as thermal paper, gradation expression for each dot can be performed in image formation.

  In the above-described method, the area of the dots is changed by changing the energization time of the heating portion of one heating element. However, the area change can be performed by other methods such as changing the level of the applied voltage. It is also possible to make it. Actually, there is a temporal change in the current of the heat generating part during the transition time of the rise and fall of the rectangular pulse voltage, and there is a slight deviation from the result of the numerical analysis as described above. However, the area of the dots can be set freely by the above numerical analysis, and the gradation expression can be adjusted.

  In the image formation described above, the polarity of the voltage applied between the first electrode and the second electrode of the pair of electrodes is reversed, for example, from the individual electrode end 16a toward the common electrode end 13a. Even when current flows, the same can be done. Even in this case, the current density has a biased current distribution that is large in the vicinity of the common electrode end portion 13a and decreases as the distance from the common electrode end portion 13a approaches the individual electrode end portion 16a.

  In this way, favorable halftone recording control is facilitated by the gradation expression for each dot using the thermal print head of the present invention. In particular, when the end portion of the first electrode energizing the heat generating portion is annular as in the first embodiment, and the end portion of the second electrode is located at the center thereof, FIG. As shown, the area of the dots can be changed concentrically, and halftone recording with extremely high image quality can be performed.

  Further, in the thermal print head of the present embodiment, the end portion of the first electrode that surrounds the heat generating portion of each heat generating element suppresses the heat accumulation of the glaze layer through heat dissipation by the heat conduction. For this reason, the influence of the heat generation energy between the heat generating parts of adjacent heat generating elements is reduced, and the area control of each dot described above becomes easy.

  In the first embodiment, the heating element arrays arranged in one row in the main scanning direction of the thermal print head are arranged in a plurality of rows in the sub-scanning direction, and a plurality of these heating portions are arranged in a line in the main scanning direction. Will be arranged in columns. Then, a plurality of rows of heating element arrays of the thermal print head are sequentially printed. With such a printing operation, the heat generating portion of the heating element array in one column that has performed the printing operation can sufficiently dissipate heat during the printing operation of the heating element array in the other column. Alternatively, even when all the rows of heat generating element arrays perform the printing operation at the same time and a certain heat radiating time is provided thereafter, it is possible to sufficiently radiate heat from the heat generating portions of the all heat generating element arrays. In this way, the thermal history control as described in the prior art is completely unnecessary, and the high performance of the drive circuit and control circuit required in the prior art is not necessary.

  Further, the common electrode 13 of the heat generating element has an electrode layer on the glaze layer 12, and has a structure in which heat dissipation after the printing operation can be efficiently performed by the electrode layer. For this reason, in speeding up the thermal printer operation, the phenomenon that the glaze layer 12 gradually accumulates heat and rises in time with the printing operation can be easily suppressed.

  In the above embodiment, the recording medium or the like is transported after the printing operation of the plurality of heating element arrays in the sub-scanning direction is released or the pressing force is reduced with the platen roller of the thermal print head. Can be done. In addition, there is no conveyance unevenness in the print that was likely to occur in the prior art, and it is not necessary to increase the capacity and performance of the conveyance step motor or the like. For this reason, it is not necessary to increase the size of the control mechanism and power source of the thermal printer, which is required in the prior art. At the same time, the wear of the protective layer on the heat generating portion of the thermal print head due to the sliding contact of thermal paper or the like in the step conveyance as in the prior art is reduced, and the life of the thermal print head can be extended.

  In this way, the thermal print head of the present embodiment enables high-speed printing, low cost, small size and light weight of the thermal printer, and good halftone recording by gradation expression for each dot in image formation. Become.

(Second Embodiment)
Next, a thermal print head according to a second embodiment of the present invention will be described with reference to FIG. Here, FIG. 5 is a view showing an example of the resistor substrate portion of the thermal print head according to the present embodiment, where (a) is a partial top view, and (b) is an enlarged view of the Z ₂ -Z ₂ arrow. It is sectional drawing.

  As shown in FIG. 5, the glaze layer 12 is provided on the support substrate 11 in the same manner as described in the first embodiment, and the glaze layer 12 is deposited on the surface of the glaze layer 12. The electrode 13 is formed as a single electrode layer. Then, for example, a planar circular heating resistor 15 is disposed on the common electrode 13 via the first interlayer insulating layer 14, and the common electrode end portion 13 a electrically connected to the lower surface side at the center of the heating resistor 15. Is projected at a predetermined position of the electrode layer. Further, the individual electrode 16 is disposed on the first interlayer insulating layer 14, and for example, an annular individual electrode end 16 a is electrically connected to the upper surface side of the outer peripheral portion of the heating resistor 15. As in the first embodiment, the planar circular heating resistor 15 serves as a heating portion.

  The heating resistor 15 described above and the common electrode 13 and the individual electrode 16 which are the energization electrodes constitute one heating element. In this heating element, unlike the structure of the first embodiment, for example, the outer peripheral portion of the heating resistor 15 in contact with the individual electrode end portion 16a from the lower surface side of the central portion of the heating resistor 15 in contact with the common electrode end portion 13a. Heat is generated by energizing the upper surface of the plate.

  As described in the first embodiment, the heating elements are arranged in the X direction of the thermal print head to form a heating element array. Such a heating element array is arranged in a plurality of rows in the Y of the thermal print head. They are arranged in parallel in the direction at a predetermined interval. In this way, the heat generating portions of the respective heat generating elements are arranged in a plurality of rows, for example, in a line shape in the main scanning direction. FIG. 5A shows a case where the first to fourth heating element arrays are formed in four rows in order from the front in the Y direction. The number of columns and columns in the two-dimensional array of the heating element arrays are shown. The interval is appropriately set according to the operating speed of the thermal printer, the heat storage / heat dissipation characteristics of the glaze layer 12, and the like.

  Then, as described in the first embodiment, the individual electrode pad portion 16b which is the electrode lead end portion of the individual electrode 16 is exposed and is entirely covered with the protective layer 17 for bonding wire connection.

  In the thermal print head of the second embodiment, the support substrate 11, the glaze layer 12, the common electrode 13, the common electrode end portion 13a, the first interlayer insulating layer 14, the heating resistor 15, the individual electrode 16 and the protective layer 17 are: It is comprised with the material similar to having demonstrated in 1st Embodiment.

  Further, in the thermal print head, the individual electrode end portion 16 a may be formed to be electrically connected to the upper surface and the peripheral end surface of the outer peripheral portion of the heating resistor 15.

  Next, an example of the manufacturing method of the thermal print head concerning 2nd Embodiment is demonstrated with reference to FIG. 2 and FIG. FIG. 6 is a cross-sectional view by main manufacturing process when the resistor substrate portion of the thermal print head is cut out, and is a cross-sectional view by manufacturing process showing the manufacturing process of the thermal print head following FIG.

  The common electrode end portion 13 a electrically connected to the common electrode 13 is formed at a predetermined position of the first interlayer insulating layer 14 in the structure shown in FIG. 2D as described in the first embodiment. Thereafter, as shown in FIG. 6A, the resistor film 23 and the metal film 26 are laminated by, for example, sputtering so as to cover the first interlayer insulating layer 14 and the common electrode end portion 13a. Here, the resistor film 23 is made of, for example, a cermet material having a film thickness of about 0.05 μm, and the metal film 26 is made of, for example, an Al film, an AlCu alloy film, or the like having a film thickness of about 0.5 μm. Then, the metal film 26 and the resistor film 23 are patterned by a photoengraving process.

  In this way, as shown in FIG. 6B, the heating resistor 15 and the individual electrode 16 having a multilayered structure are formed. Here, the heating resistor 15 has a planar circular region having a diameter of, for example, about 50 μm to 150 μm with the common electrode end portion 13a as a central portion. Further, since the heating resistor 15 has the same pattern as that of the individual electrode 16, the heating resistor 15 is disposed so as to be layered on the electrode lead wiring portion of the individual electrode 16 and the lower portion of the individual electrode pad portion 16b.

  Next, as shown in FIG. 6C, the individual electrode 16 in the planar circular region of the heating resistor 15 is patterned by a photo-engraving process, and the individual electrode end portion 16a is formed on the outer periphery thereof. . The surface of the heating resistor 15 exposed here is treated so that no metal film remains. In this way, the heat generating portion of the heat generating resistor 15 has the individual electrode end portion 16a connected on the upper surface side of the outer periphery of the planar circular region of the heat generating resistor 15, and the common electrode end on the lower surface side of the central portion. The part 13a is formed in a connected structure.

  Thereafter, the protective layer 17 is formed by the sputtering method in the same manner as in the first embodiment. As described above, the resistor substrate portion of the thermal print head according to the present embodiment as described with reference to FIG. 5 is easily manufactured.

  Note that image formation on a recording medium using the thermal print head of the second embodiment is performed in the same manner as described in the first embodiment. In the above-described thermal print head, as described in the first embodiment, the glaze layer 12 has an FG structure, a PEG structure, or a PG structure. One heating element may have a 2-bit structure.

  In the second embodiment, the same effects as those described in the first embodiment are achieved, and high image quality in image formation is maintained, and the thermal printer can be increased in speed, cost, size, and weight. Become. Further, in the second embodiment, the manufacturing process of the thermal print head is simplified and the number of processes is reduced as compared with the case of the first embodiment. For this reason, the manufacturing yield of the thermal print head is improved and the manufacturing cost can be easily reduced.

(Third embodiment)
Next, a thermal print head according to a third embodiment of the present invention will be described with reference to FIG. Here, FIG. 7 is a view showing an example of the resistor substrate portion of the thermal print head according to the present embodiment, where (a) is a partial top view, and (b) is an enlarged view of the Z ₃ -Z ₃ arrow. It is sectional drawing.

  As shown in FIG. 7, the glaze layer 12 is provided on the support substrate 11 in the same manner as described in the first embodiment, and the glaze layer 12 is deposited on the surface of the glaze layer 12. The electrode 13 has a single electrode layer. Then, the first interlayer insulating layer 14 and one heating resistor 15 are laminated on the electrode layer, and the common electrode end portion 13a penetrating the first interlayer insulating layer 14 protrudes from the electrode layer, for example, in an annular shape. The heating resistor 15 is electrically connected to the lower surface side.

  Then, a second interlayer insulating layer 27 is formed on the heating resistor 15, and the individual electrode end portion 16 a penetrates through the second interlayer insulating layer 27 located at the center of the annular common electrode end portion 13 a. Then, it is electrically connected to the upper surface side of the heating resistor 15. In addition, an electrode lead wiring portion integral with the individual electrode end portion 16a is disposed on the second interlayer insulating layer 27 to constitute the individual electrode 16, and the end portion is an individual electrode pad portion 16b. In this way, one region of the heating resistor 15 defined by the annular common electrode end portion 13a becomes one heating portion.

  The heat generating portion, the common electrode 13 having the annular common electrode end portion 13a serving as the energization electrode, and the individual electrode 16 having the individual electrode end portion 16a constitute one heat generating element. In this heating element, unlike the structure of the second embodiment, for example, the heating resistor located at the center of the annular ring from the common electrode end 13a that contacts the annular shape on the lower surface side of the heating resistor 15 of one layer. The individual electrode ends 16a that are in contact with each other on the upper surface side of the 15 are energized to generate heat. In the third embodiment, the common electrode 13 is the first electrode of the energization electrode, and the individual electrode 16 is the second electrode.

  As described in the first embodiment, the heating elements described above are arranged in the X direction of the thermal print head to form a heating element array. Such a heating element array is arranged in a plurality of rows of the thermal print head. They are arranged in parallel in the Y direction at a predetermined interval. In this way, the heat generating portions of the heat generating elements are two-dimensionally arranged, for example, arranged in a plurality of rows in a line in the main scanning direction. Further, as described in the first embodiment, the individual electrode pad portion 16b which is the electrode lead end portion of the individual electrode 16 is exposed and is entirely covered with the protective layer 17 for bonding wire connection.

  In the thermal print head of the third embodiment, the support substrate 11, the glaze layer 12, the common electrode 13, the common electrode end 13a, the first interlayer insulating layer 14, the heating resistor 15, the individual electrode 16 and the protective layer 17 are The material is the same as that described in the first embodiment. The second interlayer insulating layer 27 is made of an insulating material similar to that of the first interlayer insulating layer 14.

  Next, an example of a method for manufacturing a thermal print head according to the third embodiment will be described with reference to FIG. FIG. 8 is a cross-sectional view of each main manufacturing process when the resistor substrate portion of the thermal print head is cut out.

In the same manner as described in the second embodiment, an annular common electrode end portion 13 a electrically connected to the common electrode 13 is projected at a predetermined position of the first interlayer insulating layer 14. Then, as shown in FIG. 8A, the heating resistor 15 and the second interlayer insulating layer 27 are stacked by, for example, sputtering so as to cover the first interlayer insulating layer 14 and the common electrode end 13a. To do. Here, the single heating resistor 15 having a predetermined width in the X direction of the thermal print head is formed by sputtering a cermet material having a film thickness of, for example, about 0.05 μm through a shadow mask. The second interlayer insulating layer 27 is a SiO ₂ film having a film thickness of about 0.5 μm to ₂ μm, for example.

  Next, as shown in FIG. 8B, a second opening 28 having a diameter of about 5 μm to 20 μm, for example, reaching the upper surface of the heating resistor 15 is provided at a predetermined position of the second interlayer insulating layer 27 by a photoengraving process. . Here, the predetermined portion is located at the center of the annular common electrode end 13a. Then, a metal film made of, for example, an Al film having a thickness of about 0.5 μm, an AlCu alloy film, or the like is formed to cover the second interlayer insulating layer 27 and fill the second opening 28. Thereafter, as shown in FIG. 8C, the metal film is patterned by a known photoengraving process to form individual electrodes 16 having individual electrode end portions 16a.

  In this way, in the heat generating portion of the heat generating resistor 15, the annular common electrode end portion 13a is connected to the lower surface side of the single layer heat generating resistor 15, and the individual electrode end portion 16a is positioned at the center portion of the annular shape. The heating resistor 15 is connected to the upper surface side. Thereafter, the protective layer 17 is formed by the sputtering method in the same manner as in the first embodiment. As described above, the resistor substrate portion of the thermal print head according to the present embodiment as described with reference to FIG. 7 is easily manufactured.

  Note that image formation on a recording medium using the thermal print head of the third embodiment is performed in the same manner as described in the first embodiment. In the above-described thermal print head, as described in the first embodiment, the glaze layer 12 has an FG structure, a PEG structure, or a PG structure. One heating element may have a 2-bit structure.

  In the third embodiment, the same effects as those described in the first embodiment can be obtained, and high image quality can be maintained in image formation, and the thermal printer can be increased in speed, cost, size, and weight. Become. Further, in the third embodiment, since the patterning process of the heating resistor 15 using the photo-engraving process can be reduced, the manufacturing process of the thermal print head is further simplified as compared with the second embodiment. The Further, the manufacturing yield of the thermal print head is improved and the manufacturing cost can be further reduced.

(Fourth embodiment)
Next, a thermal print head according to a fourth embodiment of the present invention will be described with reference to FIG. Here, FIG. 9 is a view showing an example of the resistor substrate portion of the thermal print head according to the present embodiment, (a) is a partial top view, and (b) is an enlarged view of the Z ₄ -Z ₄ arrow. It is sectional drawing.

  As shown in FIG. 9, the glaze layer 12 is provided on the support substrate 11 in the same manner as described in the first embodiment. A third interlayer insulating layer 29 is formed on the surface of the glaze layer 12, and individual electrode end portions 16 a are formed so as to be embedded in the third interlayer insulating layer 29. Here, the individual electrode end portion 16a is similarly embedded in the third interlayer insulating layer 29 to become the individual electrode 16 including the electrode lead wiring portion, and the other end portion is the individual electrode pad portion 16b.

  The individual electrode end portion 16 a is formed in a columnar shape in the fourth interlayer insulating layer 30 formed on the third interlayer insulating layer 29, and is a single layer of heat generated on the surface of the fourth interlayer insulating layer 30. The resistor 15 is electrically connected to the lower surface side. A common electrode 13 having an electrode opening 31 is electrically connected to the upper surface side of the heating resistor 15. Here, the planar shape of the electrode opening 31 is circular, for example, and the center thereof is located at the individual electrode end portion 16a. Thus, the region of the heating resistor 15 defined so as to be exposed at the electrode opening 31 becomes one heating portion.

  The heat generating portion, the common electrode 13 having the electrode opening 31 serving as the energizing electrode, and the individual electrode 16 having the individual electrode end portion 16a constitute one heat generating element. In this heating element, for example, the common electrode 13 in contact with the upper surface side of the heating resistor 15 of one layer is energized to the individual electrode end portion 16a in contact with the lower surface side of the heating resistor 15 located at the center of the electrode opening 31 to generate heat. Will occur. In the fourth embodiment, the common electrode 13 is the first electrode of the energization electrode, and the individual electrode 16 is the second electrode.

  As described in the first embodiment, the heating elements described above are arranged in the X direction of the thermal print head to form a heating element array. Such a heating element array is arranged in a plurality of rows of the thermal print head. They are arranged in parallel in the Y direction at a predetermined interval. In this way, the heat generating portions of the heat generating elements are two-dimensionally arranged, for example, arranged in a plurality of rows in a line in the main scanning direction. Further, as described in the first embodiment, the individual electrode pad portion 16b which is the electrode lead end portion of the individual electrode 16 is exposed and is entirely covered with the protective layer 17 for bonding wire connection.

  In the thermal print head of the fourth embodiment, the support substrate 11, the glaze layer 12, the common electrode 13, the common electrode end 13a, the first interlayer insulating layer 14, the heating resistor 15, the individual electrode 16 and the protective layer 17 are The material is the same as that described in the first embodiment. The third interlayer insulating layer 29 and the fourth interlayer insulating layer 30 are made of an insulating material similar to that of the first interlayer insulating layer 14.

  Next, an example of a method for manufacturing a thermal print head according to the fourth embodiment will be described with reference to FIG. FIG. 10 is a cross-sectional view showing main manufacturing steps when the resistor substrate portion of the thermal print head is cut out.

  As shown in FIG. 10A, a third interlayer insulating layer 29 having a thickness of about 0.5 μm is formed on the surface of the glaze layer 12 by sputtering, for example. Then, a groove having the pattern of the individual electrode 16 is formed in the third interlayer insulating layer 29 by a photo-engraving process, and this groove is filled with Al or an AlCu alloy. The filling of the metal can be easily performed by the same method as described in FIGS. 2C and 2D in the first embodiment. In this manner, the individual electrode 16 having the individual electrode end portion 16a, the wiring portion, and the individual electrode pad portion 16b is disposed on the glaze layer 12.

  Next, as shown in FIG. 10B, a fourth interlayer insulating layer 30 having a thickness of about 0.5 μm is formed on the third interlayer insulating layer 29 and the individual electrode 16 by sputtering using a shadow mask, for example. Then, the third opening 32 reaching the individual electrode end portion 16a is formed. Then, as shown in FIG. 10C, the third opening 32 is again filled with Al or an AlCu alloy by the same method as described in FIGS. The extreme portion 16a penetrates the fourth interlayer insulating layer 30 and is exposed on the surface.

  Next, as shown in FIG. 10C, a cermet material having a film thickness of about 0.05 μm is formed by sputtering using, for example, a shadow mask so as to cover the fourth interlayer insulating layer 30 and the individual electrode end portions 16a. To form a heating resistor 15. Further, a metal film made of, for example, an Al film or an AlCu alloy film having a film thickness of about 0.5 μm is formed on the heating resistor 15. Then, this metal film is patterned by a photoengraving process to form a common electrode 13 having an electrode opening 31 as shown in FIG. Here, the electrode opening 31 is formed in a circular shape whose central portion is substantially located at the individual electrode end portion 16a and whose diameter is, for example, about 50 μm to 150 μm. In this way, the common electrode 13 is electrically connected on the upper surface side of the heating resistor 15 of one layer, and the individual electrode end portion 16a is electrically connected on the lower surface side of the heating resistor 15 located at the center of the electrode opening 31. A heat generating part of the structure is formed.

  Thereafter, the protective layer 17 is formed by the sputtering method in the same manner as in the first embodiment. As described above, the resistor substrate portion of the thermal print head according to the present embodiment as described with reference to FIG. 9 is easily manufactured.

  Image formation on a recording medium using the thermal print head of the fourth embodiment is performed in the same manner as described in the first embodiment. In the above-described thermal print head, as described in the first embodiment, the glaze layer 12 has an FG structure, a PEG structure, or a PG structure. One heating element may have a 2-bit structure.

  In the fourth embodiment, the same effects as those described in the third embodiment can be obtained, and high image quality can be maintained in image formation, and the thermal printer can be increased in speed, cost, size, and weight. Become.

  Next, some modifications of the present embodiment will be described. The first electrode in the first to third embodiments describes a case where the end portion 13a or 16a has an annular shape. Here, various modifications can be made to the electrode end. The individual electrode end portion 16a in the first and second embodiments or the common electrode end portion 13a in the third embodiment has a regular hexagonal shape as shown in FIG. can do. In addition, a regular polygonal shape such as a regular tetragon, a regular pentagon, or a regular octagon may be used. Further, in the case of the common electrode end portion 13a in the third embodiment, a densely arranged honeycomb structure as shown in FIG. 11B, for example, can be used instead of the annular shape. The regular hexagonal shape of the honeycomb structure may be a regular polygonal structure such as a regular tetragon, a regular pentagon, or a regular octagon.

  Then, instead of the planar circular shape of the electrode opening 31 of the common electrode 13 in the fourth embodiment, a regular polygon such as a regular hexagon as shown in FIG. Alternatively, in this case, a honeycomb structure as shown in FIG. 11B or a regular hexagonal shape such as a regular tetragon, a regular pentagon, or a regular octagon may be employed.

  In addition, when the electrode ends 13a and 16a of the second electrode described in the first to fourth embodiments are provided in a columnar shape at predetermined positions of the interlayer insulating layer, a polygonal column is used instead of the column. Can do.

  Further, when the columnar electrode end portions 13a and 16a are formed, a resistor having an appropriate resistance value or a conductor having a small thermal conductivity is formed in the tip region electrically connected to the heat generating portion of the heat generating element. It may be. By disposing such a resistor or the like, the dissipation of the calorific value due to the heat conduction at the end can be moderately suppressed and adjusted.

  In the first to fourth embodiments, one individual electrode 16 is provided for each heating element, and the individual electrode pad 16b is taken out. However, as the image formation becomes more precise and the heating elements become finer, it becomes impossible to dispose all the individual electrodes 16. In this case, the individual electrodes 16 may be reduced and shared between the heating elements in the Y direction of the thermal print head. However, in the sharing of the individual electrodes 16 as described above, it is necessary to form the common electrodes 13 so as to be separated from each other between the plurality of heating element arrays corresponding to the sharing.

  In the description of the heat generating element or the heat generating portion of the above embodiment, the common electrode 13 including the common electrode end portion 13a and the individual electrode 16 including the individual electrode end portion 16a sandwich the heat generating resistor 15 therebetween. It is formed to have a multilayer structure. Here, other various modifications of the structure are possible. For example, the individual electrode end portion 16 a in the second embodiment or the common electrode 13 in the fourth embodiment can be formed in a multilayer structure that is located below the heating resistor 15. Alternatively, the individual electrode 16 and the individual electrode end portion 16a in the fourth embodiment can be formed so as to be located in the upper layer of the heating resistor 15.

  In any case, in the thermal print head, the first electrode of the pair of electrodes energized to the heat generating portion is electrically connected to the heat generating resistor 15 to define one region to form a heat generating portion. The second electrode of the pair of electrodes is electrically connected to the heating resistor 15 at the central portion of the heating portion. Here, the central portion of the heat generating portion is inside one region defined by the first electrode. For example, as described in the embodiment, when one region defined by the first electrode is a circle, a regular polygon, or an ellipse, the second electrode has a geometry of the one region. The shape is at least in contact with the center position of the geometrical figure.

  Further, when the defined area is a general graphic surrounded by a closed curve, the central portion is related to, for example, the center of gravity of the geometric graphic. In this case, the second electrode is at least in contact with the barycentric position of the geometric figure in the one region.

  Although the preferred embodiments of the present invention have been described above, the above-described embodiments do not limit the present invention. Those skilled in the art can make various modifications and changes in specific embodiments without departing from the technical idea and technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 11 ... Support substrate, 12 ... Glaze layer, 13 ... Common electrode, 13a ... Common electrode edge part, 14 ... 1st interlayer insulation layer, 15 ... Heat generating resistor, 16 ... Individual electrode, 16a ... Individual electrode edge part, 16b ... Individual electrode pad portion, 17 ... protective layer, 18 ... driving IC, 19 ... opening pattern, 20 ... resist mask, 21 ... first opening, 22, 25, 26 ... metal film, 27 ... second interlayer insulating layer, 28 ... 2nd opening, 29 ... 3rd interlayer insulation layer, 30 ... 4th interlayer insulation layer, 31 ... Electrode opening, 32 ... 3rd opening

Claims (3)

A support substrate; a heat insulating layer made of an insulator formed on the surface of the support substrate; a plurality of heat generating parts made of a heat generating resistor formed on the heat insulating layer; A pair of electrodes comprising a first electrode that is electrically connected to the body and defines a region and a second electrode that is electrically connected to the heating resistor at a central portion of the region; In a thermal print head used in a printing apparatus that includes a protective layer formed on the pair of electrodes and performs a printing process or an overcoat process after the printing process on a recording medium,
First that the annular part consists of a projecting from the annular portion at a predetermined position of the first electrode layer electrodes is disposed on the surface of the insulation layer between the electrode layer covers the electrode layer the insulating layer through, to form the first insulator layer and the same plane in the first insulator layer,
The heating resistor is formed on the surface of the first insulator layer, and the annular portion of the first electrode is electrically connected to the lower surface side of the heating resistor to define the one region. To form the heating part,
The second electrode has a columnar portion, and the columnar portion passes through a second insulator layer covering the heating resistor and is electrically connected to a central portion of the heating portion on the upper surface side of the heating resistor. , Disposed on the surface of the second insulator layer,
The thermal print head, wherein the heat generating portion is two-dimensionally arranged on the heat retaining layer. 2. The thermal print head according to claim 1, wherein the heat generating units are arranged in a plurality of rows in a line shape in a direction perpendicular to a conveyance direction of the recording medium.   The planar shape of the one region is a circle or a regular polygon, and the second electrode is disposed at least at the center position of the circle or the regular polygon. Thermal print head.

Images