JPS61196663A - Thermal print head - Google Patents

Abstract

PURPOSE:To facilitate the production, by reducing the number of drive elements by arranging them one by one each group of adjacent m (m>=) pieces of plural heating resistor elements arranged in rows on the substrates and making a pattern connected to a drive element large. CONSTITUTION:The heating resistor elements R1, R2, R3, ... to electrically drive the heating resistor elements is reduced by half compared with the conventional one. Therefore, if the driver ICs of same degree of integration are used, the number of ICs comes to be enough by half. As the result, first the cost lowers. Then, the bonding number of selective electrodes 10-1, 10-2, 10-3, ...and the IC chips becomes 1/2, the manhour is reduced, and the productivity is also improved. Since the pitch Lpe of the selective electrodes 10-a, 10-2, 10-3, ... is two times the pitch Lpr of the heating resistor elements R1, R2, R3, ..., the selective electrode patterns requiring the fine working are enough with the coarse ones.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a thermal print head used in printers, facsimile machines, and the like.

(Prior Art) A partial plan view of a conventional edge-type thermal print head is shown in FIG. 7, a cross-sectional view taken along the line A-B in FIG. 8, and an equivalent circuit diagram in FIG. 9.

A plurality of heating resistor elements R+, R are provided on the ceramic substrate 1.
2, R3, . . . are arranged in a row, one end of each heating resistor element R+, R2, R3t . . . is connected to the common electrode 3, and each heating resistor element Element R
+, R2, lR3, . . . separate selection electrodes 4-1.4-2.4-3. ... is connected.

The common electrode 3 has heating resistor elements R1, R2, R3°...
A power source Vhd is applied to heat the .

Each selection electrode 4-1.4-2.4-3. ······teeth,
Wiring 5-1.5-2.5-3. . . , driver transistors D+ and D? as drive elements, respectively. , D3. ······It is connected to the. Driver transistors D+, D=, D3.

. . . are integrated circuits (hereinafter referred to as I'C), and these driver transistors DI, D2゜D
3. An IC chip containing a predetermined number of . has been done.

However, such a thermal print head has the following problems.

(1) Heating resistor elements R1, R2, R3,...
Driver transistors D+, D2. D3゜... is the heating resistor element Rly R2g R3
Since this is required for each H..., a large number of driver ICs occupying a large area are required, which greatly increases the cost of the thermal print head. For example, the cost of the driver IC accounted for more than 50% of the direct material cost.

(2) Since many driver ICs are used, the number of wires such as wire bonding or tape carrier bonding that connects the bonding pad on the IC chip and the selection electrode of the heat generating resistor element increases, resulting in poor yield and cost. It was becoming more expensive and its reliability was also getting worse.

(3) As is clear from FIG. 7, in order to provide a driver for each heating resistor element, the selection electrode 4-1゜4-2.4-
3. . . ., the arrangement pitch Lpe is equal to the pitch Lpr of the heating resistor elements, and fine patterning is required. For example, in order to obtain a print quality of 8 dots/mm, Lpe=125 μm, and such a fine pattern is applied to the selective electrodes 4-1°4-2.4-3.・・・
--(7) Since the pattern is arranged over a length Le (usually 1000 μm or more), pattern defects are likely to occur during manufacturing due to dust, etc., causing a decrease in yield. Also, 10
Wiring 5-1.5-2.5-. with a pitch of 0 to 125 μm.
3. . . . is not technically easy to provide, and also poses a reliability problem.

(4) Wiring connected to IC chip 5-1.5-2.5
-3. The limit for producing ・・・・・・ with good yield is 10
It is 0 μm. Therefore, it has not been easy to elastically design and manufacture a thermal print head with high printing quality of 10 dots/mm or more.

(Objective) An object of the present invention is to reduce the number of drive elements and increase the size of patterns connected to the drive elements in a thermal print head, thereby making it easier to produce and reducing costs.

(Structure) The thermal print head of the present invention includes a plurality of heat generating resistor elements arranged in a row on a substrate, and is mounted as an integrated circuit, and m (m≧2) adjacent heat generating resistor elements are mounted. A drive element is arranged in each group, and is commonly connected to one end of each heating resistor element in the group, and a common electrode is commonly connected to one end of each heating resistor element in each group. and a switching element provided on each common electrode, and is configured to heat a predetermined heat generating resistor element by supplying electricity by selecting these drive elements and switching elements.

Examples will be specifically described below.

FIG. 1 is a partial plan view showing one embodiment, FIG. 2 is a sectional view taken along line CD in FIG. 1, and FIG. 3 is an equivalent circuit diagram.

(2) is a ceramic substrate similar to the conventional one, preferably having a glaze layer formed on the surface as a heat insulating layer. Heating resistor elements R1, R2, R3, . . . are also arranged in rows on the ceramic substrate 1, similar to those shown in FIG.

The heating resistor elements R+, R2, R3,...
They are grouped by two adjacent items. For example, the heating resistor elements R1 and R2, R3 and R4, and R et al.
-3, . . . are connected, and each selection electrode 10-1.
10-2.10-3. Wiring 5 for each
-1.5-2.5-3. . . , driver transistors D+, D2 . D3
．． ...... are connected one by one. Also, heating resistor elements R1, R2, R3,.

. . . At the other end, the first common electrode 11-1 is connected to the heating resistor elements R+, R3, R5, . Power supply terminal Vhd+ by transistor SW1
Electric power is supplied from the heating resistor elements R2 and R in the even numbered rows.
4, R6, . . . are connected to the second common electrode 11-2, and power is supplied from the power supply terminal Vhd2 by the switching transistor SW2 as a switching element.

As shown in FIG. 2, the common electrode 11-2 of the heating resistor elements in the even-numbered columns is patterned at the same time as the common electrode 11-1 of the heating resistor elements in the odd-numbered columns.
-2a, and a second layer portion 1l-2b which uses the protective film 6 as a full-layer insulating film and connects to the first layer portion 1l-2a through a through hole 12 formed in the protective film 6. It consists of

In order to print the l line using this embodiment, first turn on the switching transistor SW1 and turn off SW2 to select a predetermined driver transistor, then turn off the switching transistor SW1 and turn on SW2 to select the predetermined driver transistor. Select driver transistor. In this way, the l-line heating resistor elements R1, R2,
Printing of one line is completed by dividing R3, . . . into odd-numbered columns and even-numbered columns and driving them twice.

In this embodiment, the heating resistor elements R+, R2, R3, . . . shown in FIG. 1 and the heating resistor elements R1, R2, R3, .
. . . are arranged in the same number and at the same pitch, the following difference will occur.

(1) In this embodiment, a driver D drives the heating resistor element by energizing it.1. D2, D3.・・・・・・ is the 7th number
This is halved compared to the case shown in the figure. Therefore, if driver ICs with the same degree of integration are used, the number of ICs can be reduced by half. As a result, costs will first be reduced. And selection electrode 10-1.10-2.10-3.・・・・・・
Since the number of bonding between ... and the C chip is reduced to 1/2, the number of man-hours is reduced, productivity is improved, and costs are further reduced from this point of view as well.

(2) In this embodiment, the selection electrode 10-1.10-2.1
0-3. The pitch Lpe of... is 2 of the pitch Lpr of the heating resistor elements R+, R2, R3,...
Because it is doubled, it is usually 10 to 20 mm long L.
The selective electrode pattern, which previously required fine processing, can now be made coarse, reducing pattern defects due to foreign matter such as dust or scratches during processing, improving yields and lowering costs.

(3) The processing precision of the selected electrode pitch is limited by the wire bonding machine precision (100 to 125 μm) and the outer bonding machine precision (80 to 100 μm), so the conventional edge type is 10 dots/mm (at this time Lpe = 10 If a thermal print head with a resolution and print quality of 20 dots/mm can be achieved in this embodiment, if the selected electrode pitch is the same as the conventional one, a resolution and print quality of 20 dots/mm can be achieved.

FIG. 4 is a partial plan view showing the second embodiment, and FIG. 5 is an equivalent circuit diagram thereof.

A strip-shaped heating resistor thin film 20 is formed on the ceramic substrate 1, and common electrodes 22-1, 22-2, 22-3, .・・・・・・
and selection electrode 21-1.21-2°21-3.・・・・・・
- The stripes are formed alternately from opposite directions so as to cross the band-shaped heating resistor thin film 2o.

Selection electrode 21-1.21-2.21-3.・・・・・・
and common electrode 22-1.22-2.22-3.・・・・・・
The portion of the heat generating resistor thin film 20 sandwiched between the heat generating resistor elements rl, r2 . r3. It becomes... In this case, heating resistor elements rl, r2. r3. . . . are not arranged in the order of data, but as shown in the figure, rl, r2 . r4. r3. r5. r6. r8゜r7.
...They are arranged in rows. Among the common electrodes, odd-numbered column common electrodes 22-1.22-3. . . . are integrated by the electrode 23, and the common electrodes 22-2 in even-numbered columns
．． 22-4. . . . are integrated by an electrode 24. Even-numbered rows of common electrodes 22-2.22-4. ...
... and the electrodes 24 are connected through through holes 25 provided in a protective film (not shown), as in FIG. Odd numbered rows of common electrodes 22-1, 22-3.・・・・・・
... are connected from the power supply terminal Vhd+ via the switching transistor SW1 to the heating resistor elements rl, r3 . r
5. . . . and the even-numbered rows of common electrodes 2
2-2.22-4. . . . are connected from the power supply terminal Vhd2 through the switching transistor SW2 to the heating resistor elements r2゜r4. r6. Supply power to...

According to this embodiment, the number of through holes 25 is only 172 compared to the embodiment shown in FIG. 1, so that in addition to the effect of the embodiment shown in FIG. 1, the manufacturing yield can be improved. Further, in this embodiment, since the heating resistor thin film 20 is not separated for each element, there is an advantage that the yield can be improved even if the pattern accuracy is poor.

FIG. 6 shows an equivalent circuit of still another embodiment. The heat generating resistor elements R+, R2, R3, . (for example, DI). Also,
The common electrode is also divided into three parts indicated by symbols 30-1 to 30-3, and the first heating resistor elements R1 and R4 of each group
, R7, . . . are connected from the power supply terminal Vhd+ to the first common electrode 30 by switching transistor SWl
-1, and the second heating resistor elements R2, R5, . . . of each group are supplied with power terminal Vh.
Power is supplied from the switching transistor SW2 from the switching transistor SW2 through the second common electrode 30-2, and the switching transistor is supplied from the power supply terminal Vhd3 to the third heating resistor elements R3, R6, . . . of each group. SW3
are connected so that power is supplied via the third common electrode 30-3.

According to this embodiment, compared to a conventional thermal print head having the same number of heating resistor elements at the same pitch, the number of drivers is reduced to 1/3, and the selection electrode pitch (Lp
e) will be tripled. Therefore, raw material costs are reduced, yields are improved, and reliability is further improved.

It is also possible to further increase the number of divisions. The optimum number of divisions may be set after considering the overall cost and quality, including the external port=11- path.

Note that the driver transistors D+, D2. D3゜...
. . . are made into ICs as in the past, and mounted on a ceramic substrate, printed wiring board, or support plate by the tape carrier method or wire bonding method.

Further, as the switching element, in addition to the illustrated transistor, a thyristor or the like can be used. It is preferable that the switching element is also mounted on a ceramic substrate or a printed wiring board.

(Effect) According to this invention, the heating resistor elements are grouped,
The common electrode is divided and the drive element is shared. As a result, (1) the number of drive elements is reduced and costs are reduced;

(2) Since the selection electrode pattern is rough, the number of bonding is reduced when producing the same printing quality as before, improving yield and reliability.

(3) If the same selection electrode pitch as the conventional one is adopted,
Heat generating resistor elements can be arranged at higher density, achieving a thermal print head with high printing quality.

[Brief explanation of drawings]

FIG. 1 is a partial plan view showing one embodiment of the present invention, FIG. 2 is a sectional view taken along the line CD in FIG. 1, FIG. 3 is an equivalent circuit diagram of the same embodiment, and FIG. FIG. 5 is an equivalent circuit diagram of the same embodiment; FIG. 6 is an equivalent circuit diagram of another embodiment; FIG. 7 is a partial plan view of a conventional thermal print head; Figure 8 is a sectional view taken along line A-B in Figure 7;
FIG. 9 is an equivalent circuit diagram of the conventional example. I; ceramic substrate,

Claims (1)

[Claims] (1) A plurality of heat generating resistor elements arranged in a row on a substrate, and one heat generating resistor element for each group of m (m≧2) adjacent heat generating resistor elements mounted as an integrated circuit. a drive element which is arranged in common and connected to one end of each heat generating resistor element in each group; a common electrode which is commonly connected to one end of each heat generating resistor element in each group; and a drive element provided in each common electrode. A thermal print head, comprising: a switching element having a heat generating resistor element selected from the drive element and the switching element;