JP3477022B2 - Thermal head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a thermal head incorporated as a printer mechanism of a word processor, a facsimile or the like. In recent years, attempts have been made to make the surface of a thermal head in contact with a recording medium as flat as possible in order to perform thermal recording on a hard recording medium such as a plastic card which is difficult to bend. I have. In such a conventional thermal head, for example, as shown in FIG. 3, a hole 11a is provided in an insulating substrate 11 having a heating resistor 13 and a conductive layer 14, and a heating resistor is provided in the hole 11a. 13 has a structure in which a driver IC 15 for controlling heat generation is embedded.
By embedding 5 in the hole 11a of the insulating substrate 11, there is no longer a large protruding portion on the surface of the thermal head, so that printing is performed on a hard recording medium P such as a plastic card which is difficult to bend. Even in the case of performing this, a flat path in which the recording medium P is conveyed onto the heating resistor 13 in a substantially flat shape becomes possible. In the thermal head described above, a resin material 16 for fixing the driver IC 15 is filled between the hole wall surface of the insulating substrate 11 and the driver IC side surface, and the conductive material is passed through the upper surface of the resin material 16. The heating resistor 13 and the like are electrically connected to the driver IC 15 via the conductive layer 14 by extending the layer 14 over the terminal electrode 15a on the upper surface of the driver IC. When printing is performed by using the above-described thermal head, for example, the ink ribbon and the recording medium P are conveyed to the heating resistor 13 via the driver IC 15 while the driver IC 15 is being driven. And heat is applied to the heating resistor 13 to selectively cause the heating resistor 13 to individually generate Joule heat, and the generated heat heats and melts the ink of the ink ribbon, and this is heated using an external platen or the like. An image is formed on the recording medium P by pressing and transferring to the recording medium P side. However, according to such a conventional thermal head, the upper surface of the driver IC 15 embedded in the hole 11a of the insulating substrate 11 has
An electric circuit such as a terminal electrode 15a and a switching transistor is provided. Therefore, when a hard recording medium P such as a plastic card is conveyed along the surface of the thermal head at the time of printing, the recording medium P or the like is moved between the upper surface of the driver IC 15 and the hard recording medium P by the action of static electricity or the like. The attached large dust is bitten, and the pressing of the dust has a disadvantage that the electric circuit such as the terminal electrode 15a of the driver IC 15 and the switching transistor is damaged. In the above-mentioned conventional thermal head, a resin material 16 for fixing the driver IC 15 is used.
Is formed of a soft resin such as a silicone resin, when large dust attached to the ink ribbon or the recording medium P is caught between the upper surface of the driver IC 15 and the recording medium P, the resin material 16 becomes dusty. The conductive layer 14 deposited on the resin material 16 may be severely deformed by the pressing, and may be disconnected. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has a hole provided in an insulating substrate having a heating resistor and a conductive layer. causes embedded driver IC having a terminal electrode, a thermal head formed by electrically connected by extending the conductive layer on the terminal electrode of the dry <br/> bar IC, hole of the insulating substrate A hard resin is filled between the inner wall surface and the driver IC side surface, and the driver IC is fixed with the hard resin, and the upper surface of the driver IC is more elastic than the hard resin.
It is characterized by being covered with a soft resin which is easily deformed . Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a plan view showing an embodiment of the thermal head of the present invention, and FIG. 2 is a cross-sectional view taken along the line XX of FIG. 1, wherein 1 is an insulating substrate, 1 a is a hole, 3 is a heating resistor,
4c is a conductive layer, 5 is a driver IC, 6 is a hard resin,
7 is a soft resin. The insulating substrate 1 has a thickness of 0.5 to 1.5 mm.
And a plurality of holes 1a are provided on the upper surface thereof. The insulating substrate 1 supports a heating resistor 3 and conductive layers 4a to 4c, which will be described later, on its upper surface, and a driver IC 5, which will be described later, is buried in the hole 1a. An effect is provided to prevent the recording medium P from protruding more than the upper surface, thereby enabling a flat pass of the recording medium P. When the insulating substrate 1 is formed of, for example, alumina ceramics, an organic solvent suitable for a ceramic raw material powder such as alumina, silica, magnesia, etc.
A solvent is added and mixed to form a slurry, and a ceramic green sheet is formed by adopting a conventionally known doctor blade method, calender roll method, or the like.
Thereafter, the ceramic green sheet is manufactured by punching the ceramic green sheet into a predetermined shape and firing at a high temperature. Thereafter, the upper surface of the obtained insulating substrate 1 is irradiated with a laser having a predetermined intensity, and a part thereof is melted and scattered. Or a part of the insulating substrate 1 is cut to form the hole 1a. On the upper surface of such an insulating substrate 1,
Partial glaze layer 2 having a mountain-like cross section and a plurality of heating resistors 3
And conductive layers 4a to 4c of a predetermined pattern are respectively applied. The partial glaze layer 2 is made of a material having a low thermal conductivity such as glass. A plurality of heating resistors 3 attached near the top of the glaze layer 2 are projected upward to press the recording medium P or the like. And effectively accumulates the heat generated by the heat generating resistor 3 to an appropriate temperature to maintain the thermal response characteristic of the thermal head satisfactorily. The heating resistor 3 is formed of the partial glaze layer 2.
Are arranged and arranged near the top of each of them, and each of them is formed of an electric resistance material such as tantalum nitride, so that when external power is applied through conductive layers 4a and 4b described later, Joule heat is generated. When printing is performed using, for example, an ink ribbon, the ink has a function of generating heat to a predetermined temperature required for melting the ink, for example, a temperature of 150 to 250 ° C. The conductive layers 4a to 4c are connected to one end of the heating resistor 3 and serve as a common electrode.
A conductive layer 4b as an individual electrode connecting the other end of the heating resistor 3 to the terminal electrode 5a of the driver IC 5, and a conductive layer 4c as a control signal line for supplying a print signal or the like to the driver IC 5, The conductive layers 4a and 4b function to apply external power to the heating resistor 3, and the conductive layer 4c controls an external printing signal and the like for a driver IC.
5 is supplied. The partial glaze layer 2 is formed by printing and applying a glass paste obtained by adding and mixing an appropriate organic solvent and an organic solvent to a predetermined glass powder by a conventionally known screen printing or the like. About 1000 ° C. to 1200
The heating resistor 3 and the conductive layer 4 are attached and formed in a band shape on the upper surface of the insulating substrate 1 by baking at a temperature of
a to 4c are deposited and arranged in a predetermined thickness and a predetermined pattern by employing a conventionally known thin film forming technique such as a sputtering method and a photolithography technique. A plurality of driver ICs 5 are individually embedded in the plurality of holes 1a provided in the insulating substrate 1. The driver IC 5 has a plurality of terminal electrodes 5a on its upper surface which are electrically connected to the conductive layers 4b and 4c.
And an electric circuit such as a switching transistor are formed, respectively. When an external printing signal or the like is supplied through the conductive layer 4c or the like, the conductive layers 4a, 4a,
4b of the power applied to the heating resistor 3 via the
Off is controlled. The space between the hole wall surface of the insulating substrate 1 and the side surface of the driver IC 5 is filled with a hard resin 6.
It is covered with a soft resin 7 that is more easily deformed elastically. The hard resin 6 is prepared, for example, by mixing an epoxy resin, a polyimide resin and a polyetheramide at a predetermined ratio, and adding an alumina filler having an average particle size of about 25 μm at a content of 50 to 80% by weight. The driver IC 5 is firmly fixed at a predetermined position in the hole 1a, and the upper surface of the hard resin 6 is
Positioning at approximately the same height as the upper surface of C5 has the effect of facilitating the formation of conductive layers 4b and 4c deposited thereon as a good continuous film. On the other hand, the soft resin 7 is made of an epoxy resin or a polyimide resin containing no alumina filler or the like, and the soft resin 7 is easily elastically deformed. When transported along the surface of the thermal head,
Between the upper surface of the driver IC 5 and the hard recording medium P,
Even if large dust adhering to the recording medium P or the like is caught by the action of static electricity or the like, the soft resin 7 itself absorbs the external force due to the pressing of the dust by being elastically deformed or shaved. The terminal electrode 5a on the upper surface of the driver IC and the electric circuit can be effectively prevented from being damaged, and the reliability of the thermal head can be improved. Further, since the hard resin 6 is filled between the hole wall surface of the insulating substrate 1 and the side surface of the driver IC, as described above, even if the soft resin 7 is deformed, Is hardly deformed, and the conductive layers 4b and 4c interposed therebetween can be maintained in a good state. Therefore, the disconnection of the conductive layers 4b and 4c is effectively prevented, and the reliability of the thermal head is also improved. The hard resin 6 has an average particle size of 25 μm.
A varnish such as an epoxy resin containing about 80% by weight of an alumina filler in an insulating substrate 1 using a dispenser or the like.
Between the hole wall surface and the side surface of the driver IC 5, which is filled by thermosetting at a temperature of about 150 ° C. The soft resin 7 is a varnish such as an epoxy resin containing no alumina filler or the like. Is formed by applying a known method such as screen printing so as to cover the holes 1a of the insulating substrate 1, and thermally curing the same at a temperature of about 150 ° C. At this time, the distance between the hole wall surface of the insulating substrate 1 and the side surface of the driver IC 5 is 200 to 6
If it is kept at 00 μm, bubbles are hardly generated between the hole wall surface and the IC side surface when the hard resin 6 is filled,
Further, the occurrence of misalignment due to shrinkage during the condensation polymerization is reduced. Therefore, the distance between the hole wall surface of the insulating substrate 1 and the side surface of the driver IC 5 is preferably maintained at 200 to 600 μm. Thus, in the above-described thermal head of the present invention, for example, the ink ribbon and the recording medium P are conveyed along the surface of the thermal head (onto the heat generating resistor 3 via the driver IC 5) while the ink ribbon and the recording medium P are conveyed. Upon driving, power is applied to the heat generating resistors 3 via the conductive layers 4a and 4b, and the heat generating resistors 3 are individually and selectively joule-heated, and the generated heat heats and melts the ink of the ink ribbon. This is pressed and transferred to the recording medium P using an external platen or the like to form an image on the recording medium P, thereby functioning as a thermal head. It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the scope of the present invention.
If the surface roughness is set in the range of 2,000 to 40,000 mm in center line average roughness Ra, the dust is efficiently captured by the unevenness of the surface. It will be effectively prevented. In the above embodiment, a part of the heating resistor 3 and the conductive layers 4a to 4c may be covered with a wear-resistant layer formed of silicon nitride or the like. By doing so, it is possible to prevent the heating resistor 3 and the like from being worn by sliding contact of the recording medium P and the like, and to prevent the heating resistor 3 and the like from being corroded by contact with moisture contained in the atmosphere. According to the thermal head of the present invention, the space between the hole wall surface of the insulating substrate and the side of the driver IC is filled with a hard resin, and the driver IC is fixed with the hard resin. Since the upper surface of the IC is covered with a soft resin that is more easily deformed elastically than the hard resin, when a hard recording medium such as a plastic card is conveyed along the surface of the thermal head at the time of printing, the upper surface of the driver IC is hardened. Even if large dust adhering to a recording medium or the like is bitten by the action of static electricity or the like between the recording medium and the soft resin, the soft resin itself is elastically deformed or scraped, so that the external force due to the pressing of the dust is generated. Absorbs
This effectively prevents the terminal electrodes and the electric circuit on the upper surface of the driver IC from being damaged, and improves the reliability of the thermal head. According to the thermal head of the present invention, since the space between the hole wall surface of the insulating substrate and the side surface of the driver IC is filled with the hard resin, even if the soft resin is deformed as described above, The hard resin is hardly deformed, and the conductive layer interposed therebetween can be maintained in a good state. Therefore, the disconnection of the conductive layer is effectively prevented, which also improves the reliability of the thermal head.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing one embodiment of a thermal head according to the present invention. FIG. 2 is a sectional view taken along line XX of FIG. FIG. 3 is a sectional view of a conventional thermal head. [Description of Signs] 1 ... Insulating substrate 1a ... Hole 3 ... Heating resistors 4b, 4c ... Conductivity Layer 5 Driver IC 6 Hard resin 7 Soft resin

Claims (1)

(57) Claims 1. An insulating substrate having a heating resistor and a conductive layer is provided with a hole, and a driver IC having a terminal electrode on the upper surface is embedded in the hole , and the driver IC is provided with the hole. of a thermal head comprising electrically connected by extending the conductive layer on the terminal electrode, filled with hard resin between the hole wall and the driver IC side surface of the insulating substrate, the rigid resin is fixed <br/> driver IC in the hard resin the driver IC top
A thermal head characterized in that it is covered with a soft resin that is more easily deformed elastically .