JP5802032B2 - Thermal print head - Google Patents

Description

  The present invention relates to a thermal print head used as an image recording device.

  The thermal print head is an output device that heats a plurality of resistors arranged in a heat generating area and forms images such as characters and figures on the thermal recording medium by the heat (see, for example, Patent Document 1). This thermal print head is widely used in recording devices such as barcode printers, digital plate-making machines, video printers, imagers, and seal printers.

As shown in FIG. 7, the thermal print head generally includes a heat radiating plate, and a head substrate 130 and a circuit substrate 140 that are bonded onto the heat radiating plate. The head substrate 130 has, for example, a support substrate made of ceramics such as Al ₂ O ₃ (alumina) and a glaze layer formed on the upper surface of the support substrate. On the upper surface of the glaze layer, there are formed a plurality of heating resistor portions extending in the sub-scanning direction 72 and arranged at intervals in the main scanning direction 71, and electrodes are formed at both ends of each heating resistor portion. These constitute a heating element.

  On the other hand, a connection circuit is formed on the circuit board 140. In addition, a driving IC having a switching function capable of controlling the heat generating element is mounted on the upper surface of the circuit board 140. The driving IC is connected to the electrode of the heat generating element and the connection circuit via, for example, a bonding wire. The driving IC and the bonding wire are sealed by a sealing body 156 made of an epoxy resin applied and formed on the upper surface of the head substrate 130 and the upper surface of the circuit substrate 140.

  A thermal printer using such a thermal print head includes a platen roller. The platen roller is disposed so that its side surface is in contact with a heat generating region (a strip-shaped region in which a plurality of heat generating resistance portions are arranged) 138 with the main scanning direction 71 as an axis, and is provided to be rotatable about the shaft. . The thermal printer moves the thermal recording medium in the sub-scanning direction 72 perpendicular to the main scanning direction while pressing the thermal recording medium inserted between the platen roller and the heating area against the heating area 138 by the rotation of the platen roller. Let As the heat-sensitive recording medium moves, a desired image is formed by selectively generating heat from the plurality of heating resistance portions.

JP 2009-6638 A

  In order to seal the driving IC and the bonding wire, an epoxy resin is applied and kept at a high temperature of about 100 ° C., for example, and subjected to heat treatment for several hours. In this high temperature state, the polymers of the epoxy resin are crosslinked and thermally cured. The head substrate 130 and the circuit substrate 140 are thermally expanded when the temperature is raised from room temperature (room temperature) to a high temperature state. Then, the head substrate 130 and the circuit substrate 140 are thermally contracted to return to the original temperature when the temperature is lowered to the room temperature after the thermosetting.

  However, the circuit board 140 has a larger coefficient of thermal expansion than the head board 130. Therefore, the contraction force of the circuit board 140 is applied to the sealing portion of the head substrate 130 (the portion of the head substrate 130 near the circuit board 140) through the cured sealing body 156, and as shown in FIG. The head substrate 130 is curved. As a result, the heat generating region 138 formed on the head substrate 130 is curved, the amount of curvature (d) increases, and uniform contact with the platen roller is hindered, so that the image quality is lowered.

  In order to prevent the contraction force of the circuit board 140 from being transmitted to the sealing portion of the head substrate 130, a thermal print head using a thermosetting resin, which is a soft sealing material such as silicon resin, as the sealing body 156. It has been known. However, when such a soft resin is used, the bonding wire may be broken due to an external impact or the like, which causes a problem in durability. On the other hand, such a durability problem does not occur in the epoxy resin that is a hard sealing material.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to use a hard sealing material such as an epoxy-based resin as a sealing body and to suppress bending of the head substrate.

In order to achieve the above object, a thermal print head according to the present invention has a radiator plate, a support substrate made of ceramics, and a glaze layer laminated on the upper surface of the support substrate, and is placed on the upper surface of the radiator plate. A head substrate having a plurality of heating elements arranged in the main scanning direction on the upper surface of the glaze layer; and a head substrate adjacent to the head substrate in the sub-scanning direction. A circuit board on which a connection circuit is formed; a control element mounted on the upper surface of the circuit board and electrically connected to the heating element and the connection circuit; and an upper surface of the head substrate near the circuit board; the head substrate side of the upper surface of the circuit board, and, in a thermal print head provided with the a sealing body made of epoxy resin covering the said control element, a ceramic plate Serial placed on the upper surface of the heat radiating plate extending in the main scanning direction so as to be adjacent to the head substrate and the sub-scanning direction, the circuit board, the control element is disposed, the ceramic plate on the upper surface of the ceramic plate a flexible substrate on which the first connection circuit is both edges in the main scanning direction is divided into a plurality of the disposed to protrude outward from both edges of the flexible substrate and the main scanning direction is formed, before Symbol radiating plate And a rigid substrate on which a second connection circuit is formed which is disposed at a position away from the head substrate and electrically connected to the first connection circuit. Features.

  With the configuration of the present invention, the curvature of the head substrate can be suppressed. In addition, stable image quality can be easily achieved in image formation using the thermal print head.

1 is a partially cutaway perspective view of a thermal print head according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. The top view with which it uses for description of the division | segmentation of the flexible substrate which comprises the circuit board in a thermal print head same as the above. FIG. 4 is an explanatory cross-sectional view corresponding to the cross-sectional view taken along the line IV-IV in FIG. The graph which shows the distortion amount of the subscanning direction of the composite board (flexible substrate / ceramics board) with which it uses for description of the effect of the thermal print head concerning embodiment of this invention. The graph which shows the amount of curvature of the perpendicular | vertical direction of the head board | substrate used for description of the effect of the thermal print head concerning embodiment of this invention. FIG. 6 is a schematic top view of a conventional thermal print head.

  A thermal print head according to an embodiment of the present invention will be described with reference to FIGS. Hereinafter, parts that are the same or similar to each other are denoted by common reference numerals, and redundant description is partially omitted. However, the drawings are schematic and ratios of dimensions and the like are different from actual ones.

  The thermal print head 10 includes a heat sink 20, a head substrate 30, a circuit substrate 40, and a driving IC 50 as its main parts. Here, the head substrate 30 and the circuit substrate 40 adjacent to each other are mounted on the main surface of the heat sink 20 with the adhesive layer 21 interposed therebetween. The circuit board 40 includes a flexible board 41 including a first flexible board 41 a and a second flexible board 41 b that are divided into two in the main scanning direction 71, and a rigid board 43. And these flexible substrates 41 are affixed to the heat sink 20 via the ceramic plate 60 which is affixed on the ceramic plate 60 and adhere | attached on the heat sink 20.

  A driving IC 50 as a control element is mounted on the flexible substrate 41 and hermetically sealed by a sealing body 56 made of, for example, an epoxy resin that is a hard sealing material. The sealing body 56 is provided across the flexible substrate 41 and the head substrate 30.

  The heat sink 20 is made of a metal such as aluminum or stainless steel and has a strip shape extending in the main scanning direction 71. The adhesive layer 21 is made of a double-sided adhesive tape or a soft thermosetting resin adhesive such as silicon resin.

The head substrate 30 extends in the main scanning direction 71 and is mounted on the heat sink 20. The head substrate 30 has a support substrate 31 and a glaze layer 32. The support substrate 31 is made of an insulating material having heat resistance, and is made of ceramics such as alumina. In addition, SiN, SiC, quartz, AlN, or fine ceramics containing Si, Al, O, N, or the like may be used. The glaze layer 32 is made of, for example, a glass film made of SiO ₂ or a resin film, and is laminated on the support substrate 31.

  On the upper surface of the glaze layer 32, a plurality of heating resistors 33 are formed that extend in the sub-scanning direction 72 in which the print medium runs perpendicular to the main scanning direction and are arranged at intervals in the main scanning direction 71. Yes. An individual electrode 34 and a common electrode 36 are disposed on the heating resistor 33 so as to face each other with a gap G therebetween. Here, the pair of electrodes including the individual electrode 34 and the common electrode 36 are layered on the heating resistor 33 and are electrically connected. The heating resistor 33 exposed in the gap G becomes the heating resistor portion 37. The heat generating resistor portion 37 constitutes one heat generating element together with a pair of electrodes serving as energization electrodes, and is arranged in a strip shape at a required pitch (dpi: dots / inch) in the main scanning direction 71 to form a heat generating region 38. As will be described later, the individual electrode 34 is electrically connected to the driving IC 50 via a bonding wire 52.

  Here, the head substrate 30 is formed as follows, for example. For example, an elongated support substrate 31 having a plate thickness of about 0.5 mm to 1.0 mm made of alumina ceramics is prepared, and a glaze layer 32 made of glass is fused and fired on the upper surface thereof. Next, a resistor layer and a conductor layer are sequentially laminated on the entire upper surface of the glaze layer 32 by a thin film forming apparatus such as a sputtering apparatus. Thereafter, the conductor layer and the resistor layer are processed into a shape pattern of the heating resistor portion 37 by a photoengraving process. Subsequently, the conductor layer in the gap G is removed by etching to form predetermined individual electrodes 34 and common electrodes 36. Further, a protective layer 39 that covers the individual electrode 34, the common electrode 36, and the heating resistor portion 37 is formed, and an opening is formed in the protective layer 39 above the connection portion of the individual electrode 34 with the bonding wire 52.

Here, the resistor layer is made of, for example, TaSiO, NbSiO, TaSiNO, or TiSiCO based electric resistor material. The conductor layer is composed mainly of metal such as Al, Cu, or AlCu alloy, for example. The protective layer 39 is made of an insulating material having a hard and dense thermal conductivity such as a SiO ₂ film, a SiN film, a SiON film, or a SiC film. Here, when at least Si and carbon are contained in the outermost surface of the protective layer 39, the thermal conductivity becomes high, which is preferable. This protective layer 39 covers at least the pair of electrodes and the heat generating region 38 of the heat generating element array, and protects against wear due to pressure contact or sliding contact of the recording medium, and corrosion due to contact with moisture contained in the atmosphere. Have

  As described above, the circuit board 40 includes the flexible board 41 including the first flexible board 41 a and the second flexible board 41 b, the rigid board 43, and the ceramic plate 60 that adheres to the flexible board 41. The first flexible substrate 41 a and the second flexible substrate 41 b are arranged on the main surface of the heat sink 20 so as to be adjacent to the head substrate 30 in the sub-scanning direction 72, and in the main scanning direction 71 in parallel with the head substrate 30. It is arranged. A first connection circuit 42 is formed on the first flexible substrate 41a and the second flexible substrate 41b.

  These flexible substrates 41 are thin and flexible printed substrates using, for example, polyimide or the like as an insulator base material, and are formed to have a thickness of 20 μm to 400 μm, for example. A required number of driving ICs 50 are mounted along the main scanning direction 71 on the upper surface of the flexible substrate 41 divided into two, which is close to the head substrate 30. The driving IC 50 is a control element having a switching function capable of controlling the heating element. It is electrically connected to the individual electrode 34 via the bonding wire 52. Further, the driving IC 50 is electrically connected to the first connection circuit 42 via the bonding wire 64.

  The driving IC 50 and the bonding wires 52 and 54 are sealed by a sealing body 56 made of an epoxy resin. The sealing body 56 seals the driving IC 50 and the bonding wires 52 and 54 to the upper surface of the head substrate 30 near the flexible substrate 41 and the upper surface of the flexible substrate 41 near the head substrate 30. The sealing body 56 is formed at a predetermined position through application of an epoxy resin coating liquid which is a thermosetting resin and thermal curing by heat treatment at about 100 ° C. for several hours.

  The first flexible substrate 41a and the second flexible substrate 41b are attached to the ceramic plate 60 by, for example, an epoxy thermosetting adhesive sheet 62. The ceramic plate 60 is preferably made of, for example, alumina ceramic or the like and made of the same material as the support substrate 31. Here, the region where the ceramic plate 60 is attached is preferably larger than the region covered with the sealing body 56 on the upper surface of the flexible substrate 41. For bonding the flexible substrate 41 and the ceramic plate 60, a thermosetting resin adhesive such as a soft silicone resin or a double-sided adhesive tape may be used.

  The flexible substrate 41 is bonded to the ceramic plate 60 in various forms to form a composite plate. This will be described with reference to the example shown in FIG. As shown in FIG. 3A, the flexible substrate 41 divided into a first flexible substrate 41 a and a second flexible substrate 41 b is attached to one ceramic plate 60. This ceramic plate is made of, for example, alumina ceramics similar to the support substrate 31 and has a thickness of, for example, about 0.1 mm to 1.0 mm.

  Here, the separation distance between the first flexible board 41a and the second flexible board 41b in the main scanning direction 71 is appropriately determined depending on the length of the flexible board 41 in the main scanning direction 71 or the width in the sub-scanning direction 72. It is decided. In addition, both edge ends of the flexible substrate 41 and the ceramic plate 60 in the main scanning direction 71 and their tips in the sub-scanning direction 72 are substantially at the same position. However, the width of the ceramic plate 60 is smaller than the width of the flexible substrate 41 as indicated by a broken line in the figure.

  In FIG. 3 (b), the flexible substrate 41 that is divided into three, that is, the first flexible substrate 41 a, the second flexible substrate 41 b, and the third flexible substrate 41 c is attached to the upper surface of one ceramic plate 60. . Alternatively, there is a difference in the positions of both edge ends of the flexible substrate 41 and the ceramic plate 60 in the main scanning direction 71, and both edge ends of the ceramic plate 60 protrude outward from both edge ends of the flexible substrate 41. Other aspects are the same as those described with reference to FIG.

  FIG. 3C shows a case where the ceramic plate 60 is also divided into two parts. That is, the 1st ceramic board 60a is affixed on the lower surface of the 1st flexible substrate 41a. Similarly, the 2nd ceramic board 60b is affixed on the lower surface of the 2nd flexible substrate 41b. The other aspects are as described with reference to FIG.

  In addition, there are various modifications for bonding the flexible substrate 41 and the ceramic plate 60. Here, the division of the flexible substrate 41 or the ceramic plate 60 may be more than three. The number of divisions is appropriately determined in consideration of the length of the thermal print head in the main scanning direction 71 and the like. Further, the flexible substrate 41 is not equally divided like the first flexible substrate 41a and the second flexible substrate 41b, for example, and the length in the main scanning direction 71 may be different.

  On the other hand, the rigid substrate 43 is disposed on the upper surface side of the heat dissipation plate 20 and away from the head substrate 30, and extends in the main scanning direction 71 in parallel with the head substrate 30. That is, the head substrate 30, the flexible substrate 41, and the rigid substrate 43 are disposed in the sub-scanning direction 72 in this order on the upper surface side of the heat sink 20. The rigid substrate 43 is an inflexible printed substrate using, for example, a glass epoxy resin or the like as an insulator base material. The rigid substrate 43 is formed to a thickness of 0.4 mm to 2.0 mm, for example.

  A second connection circuit 44 is formed on the rigid substrate 43, and the second connection circuit 44 is connected to the first connection circuit 42 of the flexible substrate 41. Here, at the end of the flexible substrate 41 away from the head substrate 30 and the end of the rigid substrate 43 near the head substrate 30, the terminal portion of the first connection circuit 42 and the second connection circuit 44 are respectively provided. A terminal portion is formed, and the terminal portion of the first connection circuit 42 and the terminal portion of the second connection circuit 44 are connected by solder, an anisotropic conductive film, or the like. In this embodiment, As shown in FIG. 2, they are connected by solder 45.

  Further, connectors 46 and 47 are attached to the rigid board 43. The driving power and the control signal are sent to the driving IC 50 via the connectors 46 and 47, the second connection circuit 44, and the first connection circuit 42.

  Next, an assembly process in manufacturing the thermal print head 10 will be schematically described. For example, as shown in FIG. 3A, the first flexible substrate 41a and the second flexible substrate 41b on which the first connection circuit 42 is formed are attached to the ceramic plate 60 by the epoxy thermosetting adhesive sheet 62. Prepare the attached ones. Then, for example, a bare chip driving IC 50 is mounted and mounted on a predetermined region near the head substrate 30 on the upper surface of the flexible substrate 41.

  Then, the head substrate 30 having the required number of the heating elements formed as described above is bonded to the upper surface of the heat radiating plate 20 via an adhesive layer 21 made of, for example, a double-sided adhesive tape with good thermal conductivity. Further, the ceramic plate 60 to which the flexible substrate 41 is attached and the rigid substrate 43 are bonded to the upper surface of the heat sink 20 via the adhesive layer 21 made of, for example, a silicon resin adhesive. In this way, the head substrate 30 and the circuit board 40 are juxtaposed on the upper surface of the heat sink 20. The head substrate 30 and the flexible substrate 41 are abutted so that both edges in the sub-scanning direction 72 maintain linearity. In the circuit board 40, the first connection circuit 42 of the flexible board 41 is electrically connected to the second connection circuit 44 of the rigid board 43 by, for example, solder 45.

  Then, all the individual electrodes 34 of the heating element array are electrically connected to the bonding pads on the output side of the driving IC 50 by bonding wires 52 made of, for example, Al wires or Au wires. Further, the bonding pad on the input side of the driving IC 50 is electrically connected to the first connection circuit 42 of the flexible substrate 41 by the bonding wire 54.

  Next, in a normal temperature state such as room temperature, for example, an epoxy liquid thermosetting resin is applied to the driving IC 50, the bonding wires 52 and 54, and connection portions thereof using a syringe or the like. Then, the heat sink 20 on which the head substrate 30 and the circuit substrate 40 are juxtaposed is heated to a high temperature state such as about 100 ° C. as described above, and is thermally cured by a heat treatment for several hours, so that a hard epoxy resin is used. A sealing body 56 is formed. In the above temperature rise and high temperature states, the ceramic plates 60 to which the metal heat sink 20, the head substrate 30, and the resin flexible substrate 41 are attached have different coefficients of thermal expansion. However, these thermal expansion coefficient differences are absorbed by the adhesive layer 21 described above. Thereafter, the temperature is lowered to room temperature, and the thermal print head 10 of the present embodiment is completed.

  The effects of the thermal print head 10 according to the present embodiment will be described with reference to FIGS. FIG. 4 is an explanatory cross-sectional view for explaining the bending of the head substrate in the vertical direction 73. Here, the vertical direction 73 is a direction perpendicular to the upper surface of the head substrate 30, and is a direction orthogonal to the main scanning direction 71 and the sub-scanning direction 72. FIG. 5 is a graph showing the amount of distortion in the sub-scanning direction of a composite plate (head substrate / ceramic plate) used for explaining the effects of the thermal print head according to the embodiment of the present invention. FIG. 6 is a graph showing the amount of bending in the vertical direction of the head substrate for explaining the effect of the thermal print head according to the embodiment of the present invention.

  In the conventional general thermal print head described with reference to FIG. 7, if the sealing body 156 made of a hard sealing material such as an epoxy resin is formed, the difference in thermal expansion coefficient between the head substrate 130 and the circuit substrate 140. Thus, the head substrate 130 is curved in a convex shape in the sub-scanning direction 72 when the driving IC or the like is sealed.

  On the other hand, in this embodiment, the flexible substrate 41 divided into a plurality is bonded to the ceramic plate 60.

  Here, the head substrate 30 includes a support substrate 31 made of ceramics and a glaze layer 32 made of a glass film thinner than the support substrate 31. Therefore, the thermal expansion coefficient of the head substrate 30 is close to that of the support substrate 31 as a whole. On the other hand, in this embodiment, the divided flexible flexible substrate 41 is bonded to the ceramic plate 60 to form a composite plate. Therefore, the thermal expansion coefficient of the composite board of the flexible substrate 41 approaches the thermal expansion coefficient of the head substrate 30 as a whole.

  As a result, the thermal print head according to the present embodiment can reduce the curvature of the head substrate 30 in the sub-scanning direction 72 that occurs when the driving IC 50 and the like are sealed, as compared with the conventional thermal print head. The bending amount (d) is comparable to the case where the sealing body 56 is formed of a soft sealing material such as a silicon resin instead of a hard sealing material such as an epoxy resin.

  In addition, by configuring the ceramic plate 60 with the same material as the support substrate 31 (for example, alumina ceramic), the difference in thermal expansion coefficient can be further reduced, and the curvature of the head substrate 30 is greatly reduced. Further, when the ceramic plate 60 is made larger than the area covered with the sealing body 56 on the upper surface of the flexible substrate 41, the curvature of the head substrate 30 can be further reduced.

  By the way, if the circuit board is composed only of a flexible board, the connector is not fixed, and it is difficult to attach the thermal print head to the printer. Moreover, since the flexible substrate is expensive, the thermal print head is also expensive.

  On the other hand, in the present embodiment, since the circuit board 40 is constituted by the flexible board 41 and the rigid board 43, the connectors 46 and 47 are fixed, and the work of attaching the thermal print head to the printer is easy. Further, by using a rigid substrate 43 that is less expensive than the flexible substrate 41, the amount of the flexible substrate 41 used can be reduced, and the cost of the thermal print head 10 can be suppressed.

  The effects described above have an integrated structure in which the flexible substrate 41 is not divided, and the other effects are exhibited in substantially the same manner even when it is the same as that described in the present embodiment. Regarding the invention in which the circuit board 40 having a structure in which the flexible board 41 is not divided is applied to the thermal print head, a patent application has already been filed in Japanese Patent Application No. 2009-222365 by the applicant of the present application. The thermal print head 10 of this embodiment can further reduce the curvature of the head substrate 30 in the direction perpendicular to the main scanning direction 71 and the sub-scanning direction 72 by dividing the flexible substrate 41. That is, as shown in FIG. 4, the bending amount dz is reduced in the bending that occurs in the vertical direction 73 of the head substrate 30 that adheres to the upper surface of the heat sink 20.

  FIG. 5 shows a result of examining distortion caused by deformation of the flexible substrate 41 in the composite plate in which the flexible substrate 41 and the ceramics plate 60 are bonded as described in FIG. 3A, for example. Here, the horizontal axis in FIG. 5 indicates the effective print recording length (the length of the heat generating area 38 in the main scanning direction 71), and the vertical axis in FIG. 5 indicates the warping deformation in the sub-scanning direction 72 of the composite plate. As shown. In this amount of distortion, a positive value represents a shape that is convex in the sub-scanning direction 72, and a negative value represents a shape that is concave.

  In FIG. 5, in this embodiment, as shown in FIG. 3A, the flexible substrate 41 is divided into a first flexible substrate 41a and a second flexible substrate 41b. The width of the flexible substrate 41 in the sub-scanning direction 72 is 7 mm. On the other hand, in Comparative Example 1, Comparative Example 2, and Comparative Example 3, the flexible substrate 41 has an integral structure without division, and the width in the sub-scanning direction 72 is 7 mm, 20 mm, and 40 mm, respectively. Here, in this embodiment and the comparative example, the material of the flexible substrate 41 and the shape and dimensions of the ceramic plate 60 are the same.

  As shown in FIG. 5, in the comparative example in which the flexible substrate 41 is not divided, when the effective print recording length increases, a concave warp occurs in the sub-scanning direction 72 of the flexible substrate 41 in the composite plate. In particular, when the effective print recording length is, for example, 10 inches or more, the amount of distortion increases rapidly. The concave warpage becomes prominent when the width of the flexible substrate 41 in the sub-scanning direction 72 is reduced. However, when the width becomes as large as 40 mm, the warp becomes extremely small since it does not depend on the effective print recording length. On the other hand, in this embodiment, the warpage of the composite plate in the sub-scanning direction 72 is small as in the case of the comparative example 3, and hardly depends on the effective print recording length.

  Then, after the sealing body 56 is formed on the upper surface of the flexible substrate 41, as shown in FIG. 6, in the case of this embodiment, the vertical curvature of the head substrate 30 is smaller than that in the first comparative example. . Here, the horizontal axis of FIG. 6 indicates the effective print recording length, and the vertical axis of FIG. 6 indicates the amount of bending (dz) of the head substrate 30 in the vertical direction 73. In Comparative Example 1 shown in FIG. 6, the amount of bending increases rapidly as the effective print recording length increases. On the other hand, in this embodiment, the increase in the amount of bending becomes saturated. Here, when the effective print recording length is up to about 6 inches, the amount of bending in the present embodiment and the comparative example 1 is substantially the same. It is suppressed.

  In the present embodiment, the reason for the effect of suppressing the bending in the vertical direction is presumed as follows. As described in the assembly process in the manufacture of the thermal print head, when the head substrate 30 and the composite plate (flexible substrate 41 / ceramic plate 60) are juxtaposed and bonded to the upper surface of the heat sink 20, the head substrate 30 and the composite plate Are abutted so that both edges in the sub-scanning direction 72 maintain linearity. However, as described with reference to FIG. 5, due to the concave warp of the composite plate accompanying the deformation strain of the flexible substrate 41, a gap corresponding to the strain amount is formed between the head substrate 30. Therefore, when the sealing body 56 is formed, an inflow of the resin in which the epoxy resin reaches the main surface of the heat sink 20 from the flexible substrate 41 through the gap is generated. And in the thermosetting, the resin which flowed in hardens | cures and a vertical curve generate | occur | produces.

  In the present embodiment, the flexible substrate 41 is divided into the first flexible substrate 41a and the second flexible substrate 41b, so that the gap is reduced, and the vertical curvature of the head substrate 30 is suppressed. .

  As described above, the thermal print head according to the present embodiment suppresses bending of the head substrate in the sub-scanning direction 72 and the vertical direction 73. For this reason, in image formation, the thermal recording medium can be brought into uniform contact with the heat generation area 38 of the head substrate 30 by pressing the platen roller. Then, stable and high-quality image formation is facilitated. Further, even when the nip width of the platen roller is narrowed, high quality printed images can be recorded.

  For convenience, the description has been made using the terms “upper surface” and “lower surface”. The “upper surface” and the “lower surface” mean that they are in a relationship of front and back, and do not mean spatial top and bottom.

  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.

  In the thermal print head 10 of the above-described embodiment, the driving IC 50 may be mounted on the head substrate 30 instead of the flexible substrate 41 in the thermal print head.

  Further, the electrical connection of the driving IC 50 to the heat generating element or the circuit board may be performed by, for example, flip chip bonding using ball bumps in addition to wire bonding.

  Further, the support substrate 31, the rigid substrate 43, and the ceramic plate 60 may be bonded to the heat radiating plate 20 using the same material or different adhesives.

  Further, the thermal print head 10 of the present embodiment shows a structure in which one dot is printed by one heating element, but this is an example in which two dots can be printed by one heating element. May be. In this case, for example, image formation using an ink ribbon and high-speed overcoat processing can be performed.

  In the thermal print head 10 of the present embodiment, a case of a so-called FG (Flat Glaze) structure in which the glaze layer 32 is flat has been described. Here, the glaze layer 32 may be partially etched (PE) so as to have a so-called PEG structure in which a region where the heating resistor portion 37 is formed is partially raised. Alternatively, the glaze layer 32 may have a so-called PG structure including only the raised portion.

  Finally, it should be noted that the present invention can be similarly applied to the case where the sealing body 56 is made of a thermosetting polyimide resin.

  DESCRIPTION OF SYMBOLS 10 ... Thermal print head, 20 ... Heat sink, 21 ... Adhesive layer, 30 ... Head substrate, 31 ... Support substrate, 32 ... Glaze layer, 33 ... Heating resistor, 34 ... Individual electrode, 36 ... Common electrode, 37 ... Heat generation Resistor 38, heat generating region, 39 ... protective layer, 40 ... circuit board, 41 ... flexible board (41a, 41b), 41a ... first flexible board, 41b ... second flexible board, 42 ... first connection Circuit, 43 ... Rigid substrate, 44 ... Second connection circuit, 45 ... Solder, 46, 47 ... Connector, 50 ... Driving IC, 52, 54 ... Bonding wire, 56 ... Sealing body, 60 ... Ceramic plate (60a) 60b), 60a ... first ceramic plate, 60b ... second ceramic plate, 62 ... adhesive sheet, 71 ... main scanning direction, 72 ... sub-scanning direction, 73 ... vertical direction, G ... Chance

Claims (2)

A heat sink,
A plurality of heating elements, each having a support substrate made of ceramics and a glaze layer laminated on the upper surface of the support substrate, are placed on the upper surface of the heat sink and arranged in the main scanning direction on the upper surface of the glaze layer. A formed head substrate;
A circuit board mounted on the upper surface of the heat sink so as to be adjacent to the head substrate in the sub-scanning direction, and a connection circuit is formed;
A control element mounted on the upper surface of the circuit board and electrically connected to the heating element and the connection circuit;
An upper surface of the head substrate near the circuit substrate, an upper surface of the circuit substrate near the head substrate, and a sealing body made of an epoxy resin covering the control element;
In the thermal print head equipped with
A ceramic plate extends in the main scanning direction so as to be adjacent to the head substrate in the sub-scanning direction and is placed on the upper surface of the heat radiating plate,
The circuit board is
The control element is disposed, and both edges of the ceramic plate in the main scanning direction are arranged on the upper surface of the ceramic plate so as to protrude outward from both edges of the flexible substrate and are divided into a plurality of parts in the main scanning direction. A flexible substrate on which a connection circuit of 1 is formed ;
Are arranged on the upper surface side of the front Symbol radiating plate spaced apart from the head substrate, have a, a rigid substrate in which the second connection circuit is formed electrically connected to said first connection circuit A thermal print head characterized by   The thermal print head according to claim 1, wherein the ceramic plate is also divided into a plurality of parts in the main scanning direction.

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