JPH0213912B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a structural improvement of a thermal head that prints desired visible information on a recording medium by selectively generating heat from a plurality of heating elements.

(b) Background of the technology A thermal head has a large number of heating elements formed on the surface of an electrically insulating substrate using electrical resistance. , various symbols, characters, and images consisting of a combination of multiple dots can be printed on a recording medium such as thermal paper.

FIG. 1 is a circuit diagram showing an example of the configuration of the thermal head, in which a large number of heating element elements 1 are divided into a plurality of groups each having a fixed number (m in the figure), and X wiring x ₁ to xm
is each element 1 of the same group and reverse current prevention diode 2
The Y wirings y ₁ to ym connect the elements 1 of the same arrangement order in each element group.
Therefore, when voltage is applied to wires x ₁ and y ₂ , the current becomes y ₂
→x ₁ allows each element 1 to selectively generate heat, such that the heating element 1' generates heat.

(c) Prior art and problems In general, thermal heads with the circuit configuration described above have a large number of heating elements and their matrix wiring formed all at once on a glazed alumina substrate and are equipped with diodes, so they cannot be used on a normal wiring board. Forming the heating element and matrix wiring all at once is relatively more expensive than mounting diodes, and it is difficult to reduce costs because it is not possible to take out many thermal heads from one glazed alumina substrate. There were some shortcomings.

Since printers using thermal heads have advantages such as low noise and maintenance-free properties, they are effective not only for business and office use but also for home appliances such as hard copies of television images, and have no problems with the above-mentioned drawbacks. Improvement was strongly desired.

(d) Object of the invention The object of the invention is to eliminate the above-mentioned problems and provide an inexpensive thermal head.

(e) Structure of the Invention The above object is to provide a thin sub-board with a large number of heating elements formed on one side, and a main board on which wiring for connecting the heating elements is formed, The electrodes of the heating element and the wiring on the parent board are connected by pads so that the other side faces outward and one side on which the heating element is formed faces the parent board with a predetermined spacing therebetween. This is achieved by the unique structure of the thermal head.

(f) Embodiments of the Invention The structure of a thermal head according to the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic diagram showing a cross section of a thermal head according to an embodiment of the present invention.
1 is constructed by mounting a child substrate 13 on which a large number of heating element elements are formed on a parent substrate 12 on which wiring for connecting heating element elements is formed and diodes (2 in FIG. 1) are mounted.

The parent board 12 includes a board (for example, a metal board) 14 for ensuring mechanical strength, and a wiring board (for example, a glass epoxy board) 15 having electrical insulation properties.
A crossover wiring layer (first
Wiring y ₁ to ym) 18 in the figure, and multiple conductor layers 1
A diode 22 mounting wiring layer (wirings x ₁ to xm in FIG. 1) 21 is formed of a diode 9 and an insulating layer 20. The other child board 13 is a thin board (for example, about 100 μm thick) that has electrical insulation and wear resistance.
A resistive layer 24 and a pair of opposing electrodes 2 of the resistive layer 24 are disposed on one surface (lower surface in the figure) of the glass plate) 23.
A large number of heating element elements (see _FIG . The element 1) is formed. The child board 13 has the other side of the substrate 23 made of a thin glass plate or the like facing outward, and one surface on which the heating element is formed faces the parent board 12 at a predetermined distance. The mother board 1 is bonded with a heat-resistant/insulating adhesive (e.g., heat-resistant polyimide resin or heat-resistant inorganic adhesive) 30 so as to
It is mounted on the surface of 2. However, since the plurality of pads 27 and the conductor 16 facing them and the plurality of pads 28 and the conductor 19 facing them are respectively connected by means such as crimping or soldering prior to the mounting, thermal The head 11 has a circuit configuration as shown in FIG.

Note that in FIG. 2, the diode 22 is one in which a plurality of diode elements are housed in one package, and the recording medium (not shown) is the sub-board 13.
Since it comes into contact with the outer surface of the substrate 23 made of a thin glass plate or the like, the wear resistance is improved. Furthermore, there is a cavity on the thermal head 11 between the wiring board 15 and the protective layer 29 of the heating element, and an insulating heat-resistant adhesive (such as a heat-resistant polyimide resin material) is injected into the cavity. By filling the above-mentioned conditions, it is possible to reinforce the daughter board 13, which has a weak mechanical strength, and, as a heat storage layer, it is possible to save energy when the heating element generates heat.

In the thermal head 11 configured in this manner, the width of the daughter board 13, that is, the length in the longitudinal direction of the resistance layers 24 formed in large numbers in parallel, can be approximately 3 mm, so as shown in FIG. Board 23
(Fig. 2) A large thin substrate 31 that can be divided into
Array 3 of heating elements 32 consisting of resistive layer 24 etc.
By simultaneously forming 30 rows of PCBs 13 and dividing them, 30 sub-boards 13 can be produced extremely efficiently and at low cost.

(g) Effects of the Invention As explained above, according to the present invention, the heating element is formed on an expensive substrate, and the connection wiring of the element and the reverse current prevention diode are formed or mounted on an ordinary substrate. This and the fact that it has become possible to produce a large number of substrates on which the heating elements are formed have a great effect in making it possible to supply inexpensive thermal heads.

[Brief explanation of drawings]

FIG. 1 is an example of a circuit of a thermal head, FIG. 2 is a schematic cross-sectional view showing the main structure of a thermal head according to an embodiment of the present invention, and FIG. 3 is an explanation of a method for mass producing the daughter board shown in FIG. 2. FIG. In the figure, 1 and 32 are heating element elements, 1
1 is a thermal head, 12 is a parent board, 13 is a daughter board, and 18 and 21 are wiring layers.

Claims (1)

[Claims] 1 Comprising a thin sub-board 13 with a large number of heating elements formed on one side, a main board 12 with wirings 16 and 19 for connecting the heating elements, and the other side of the sub-board 13. The electrodes 25 and 2 of the heating element are arranged so that the electrodes 25 and 2 of the heating element face outward and one surface on which the heating element is formed faces the parent substrate 12 at a predetermined distance.
6 and the wirings 16 and 19 on the main board 12 by pad 2.
A structure of a thermal head characterized by having 7 and 28 connections.