JP3126874B2 - Thermal print head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head,
In particular, the present invention relates to a structure of a thermal head adapted to printing by thermal transfer and color printing.

[0002]

2. Description of the Related Art Conventionally, printers for OA equipment such as facsimile machines, printers for ticket vending machines, label printers, etc.
Thermal print heads that form necessary image information by selectively applying heat to a heat-sensitive medium are widely used. Generally, a thermal print head is formed by a method of forming a heating resistor layer, an electrode layer, or the like, on a substrate or a glass glaze layer, through a process such as sputtering, into a thin film type thermal print head, and a screen printing method. It is broadly classified into a thick film type thermal print head formed through a process such as baking.

A conventional thermal print head will be described by taking a thick film type as an example. As shown in FIG. 6, as shown in FIG. 6, an insulating substrate 21 made of ceramic or the like and a heat storage body formed on the surface of the insulating substrate 21 are used. Glass glaze layer 22 and a common electrode 23 formed on the glass glaze layer 22 in a comb shape
And a plurality of individual electrodes 24 formed corresponding to the common electrode
A heating resistor layer 25 formed so as to cross over the tips of the common and individual electrodes;
And a driving IC 26 for selectively applying a required voltage to each individual electrode 24 in order to selectively generate heat between the four heating resistors 25, that is, the heating regions.
Each individual electrode 24 is electrically connected to a correspondingly mounted driving IC by a conductive wire 27 such as gold.

In the thick-film type thermal print head constructed as described above, it is necessary to selectively use each of the individual electrodes 24 via a driving IC while keeping the common electrode 23 at a constant potential. By applying the voltage of
Each heating area is selectively energized, and an image is formed on the heat-sensitive medium 29 pressed and moved by the platen roller 28 by heating.

On the other hand, a thin film type thermal print head is
Except that a plurality of heating resistor layers are formed in a band shape on a glaze layer formed on an insulating substrate, and common and individual electrodes are provided on each heating resistor layer in opposition, a thick film type is used. A configuration similar to that of the first embodiment is adopted.

[0006]

In recent years, with the improvement of the technology of the thermal print head, its spread has been expanded, and various uses in the area of color printing have been studied. In recent years, in the field of thermal print heads, research for forming images in color has been actively conducted. In color image formation, since so-called solid printing is relatively frequently used, higher printing efficiency is required as compared with normal printing, so it is required to supply a larger amount of current to the common electrode. You. For this reason, in a thermal print head for color printing, it is required that the width of the common connection portion of the common electrode be sufficiently large.

However, in the above-described structure of the conventional thermal print head, in order to form the common connection portion of the common electrode 23 to have a width capable of supplying a sufficient amount of current for forming a color image, a heating resistor is required. Body 25 and insulating substrate 2
It is necessary to provide a sufficient space between the common electrode 23 and the side surface on the adjacent side, and use this space to form a common connection portion of the common electrode 23. For this reason, it is difficult to reduce the size of the entire insulating substrate in the width direction by a certain amount or more.

In the conventional thermal print head, the heating resistor layer 25 and the electrode layers 23, 24, 24 are almost entirely formed on the surface of the insulating substrate 21 by using the above-mentioned thin film technique or thin film technique. In addition, since the protective layer and the like are formed, the fact that the insulative substrate itself cannot be downsized cannot sufficiently satisfy the demand for reduction in manufacturing cost. Furthermore, in the case of color printing, when providing a plurality of thermal print heads for each color for printing of magenta, cyan, yellow, etc., in order to increase the printing efficiency of each thermal print head, the heat-sensitive medium must be electrically insulating. A heat-generating area is provided at a fixed angle to the top surface of the substrate to increase the contact resistance with the heat-sensitive medium and to improve the flexibility of arranging each thermal print head on a single platen roller, simplifying the entire device. In addition, it is necessary to consider a small-sized configuration.

On the other hand, in so-called thermal transfer (sublimation type, wax type, resin type, etc.) using a transfer film in monochrome printing, in order to obtain good image quality, wax or resin on the transfer film is applied to a printing medium. Immediately after the transfer, the film must be peeled off from the transfer film, and for that purpose, the angle between the printing medium immediately after printing and the transfer film must be made large.

Accordingly, it is an object of the present invention to provide a thermal print head which can obtain a sufficiently high printing efficiency and has an improved degree of arrangement even when used for thermal transfer or color image formation. It is in.

[0011]

According to the present invention, there is provided, according to the present invention, a substantially flat flat portion on a surface and the flat portion.
A head substrate on which a glaze layer having a higher protruding portion is formed, a common electrode having a common connection portion formed on the head substrate and connected in common, and an individual electrode formed corresponding to the common electrode A heating resistor formed between the corresponding common and individual electrodes and on each of the convex portions of the glaze layer such that a heating region is provided, and a driving IC electrically connected to the individual electrodes; And the heating area has a common center line on the head substrate.
A thermal print head formed so as to extend to a position closer to the end face of the head substrate than the top line of the convex portion of the nozzle layer and higher than the upper surface of the driving IC. You.

[0012]

The heating area has a common center line extending to a position closer to the end face of the head substrate than the top line on the surface of the glaze layer with respect to the surface of the head substrate and higher than the upper surface of the driving IC. Therefore, it is easy to set the contact angle of the heat-sensitive medium that is brought into contact with and moved on each of the heat-generating regions to, for example, 0-30 °. The concentration of pressure can be sufficiently improved,
High printing efficiency can be obtained while driving IC
, The wires connected to them and the protective film covering them can be provided in a sufficiently low positional relationship with respect to the heat generating region. Therefore, when applied to color printing, the degree of freedom of arrangement when a plurality of thermal print heads are provided on a single platen roller can be greatly improved, and the overall configuration of the apparatus can be simplified and downsized. When applied to thermal transfer printing, the angle between the print medium immediately after transfer and the transfer film can be made large, so that wax, resin, etc. were transferred onto the print medium by heating. Immediately after the transfer film is heated, the transfer film can be separated from the print medium, and an image of good quality can be formed.

[0013] The thermal print head is further mounted on the circuit board together with the driving IC by using an electrically insulating circuit board having an electric wiring pattern formed of a conductive material on the surface. By mounting, the main parts such as the common and individual electrodes and the heating resistor can be made compact on the head substrate, and the thermal print head can be further reduced in size.

The glaze layer is formed of a flat portion which is substantially flat with respect to the upper surface of the head substrate and a convex portion which rises higher than the flat portion, so that the heat generating region can be driven. ICs, wires connected to them, protective films covering them, and the like can be provided at lower relative positions.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a thermal print head according to the present invention will be described in detail with reference to FIGS. As shown in FIG. 1, the thermal print head according to the present embodiment has a head substrate 1 on which a heating resistor is formed on the upper surface, and a circuit pattern of a conductor on the surface for mounting the head substrate 1 together with a driving IC 2. This is a thin-film thermal print head composed of the circuit board 3 formed. On the lower surface of the circuit board 3, a heat radiating plate 4 made of a metal having good thermal conductivity such as aluminum is mounted.

As shown in detail in FIG. 2, the head substrate 1 includes a head substrate 5 made of ceramic or the like, a glass glaze layer 6 as a heat storage formed on the upper surface of the head substrate 5, and a thin film on the glaze layer. It comprises a plurality of resistor films 7 formed in a strip shape, and a common electrode 8 and an individual electrode 9 formed on the resistor film 7 by a conductor in an opposing pattern.

The glaze layer 6 has a flat portion 6a whose surface extends substantially parallel to the surface of the head substrate 5, and a flat portion 6a.
and a convex portion 6b which rises higher than a. As shown in FIG. 3A, a common electrode 8 is formed on the glaze layer 6 at a constant pitch via the resistor film 7 on the glaze layer 6 on the side surface 14 on the close side of the head base 5. While being formed toward the top of the portion 6b, a plurality of individual electrodes 9 are formed at the same pitch as the common electrode 8 and also toward the top of the convex portion 6b so as to face these. The resistive film 7 between the common electrode 8 and the individual electrode 9 facing each other.
Constitutes a so-called heat generating region 11,
In the heat generating region 11 of the present embodiment, the common center line 12 extending between the common and individual electrodes 8 and 9 is a top line on the surface of the convex portion of the glaze layer (the portion that rises highest with respect to the surface of the head substrate 5). The connecting line 13 extends closer to the side surface 14 of the head base 5. As described above, the common center line 12 of the heat generating region 11 is set to the top line 1 of the glaze layer convex portion.
3, the contact angle of the heat-sensitive medium contacted and moved on each of the heat generating areas 11 can be set to, for example, a range of 0 to 30 °. On these common and individual electrodes 8, 9 and the resistor film 7, a protective film 1 for covering and protecting them is further provided.
6 is formed so as to expose the common electrode 8 at the end opposite to the heating resistor. It is to be noted that the convex portion 6b of the glaze layer 6 may be formed so that its thickness is reduced in an arc shape in a cross-sectional view toward the side surface 14 of the base member 5 without raising the convex portion 6b to the surface of the flat portion 6b. In that case, the heat generating region 11 is provided on the glaze layer inclined in the arc shape, while the top line 13 is defined as extending on the boundary between the flat portion 6a and the surface of the arc-shaped convex portion 6b. Is done.

FIG. 3B is a view similar to FIG. 3A when the present invention is applied to a thick-film type thermal print head. As is clear from FIG. The common center line 12 is also the top line 1 of the convex portion 6a of the glaze layer 6.
3 is provided close to the side surface 14 of the head base 5. Referring to FIG. 2 again, a metal layer 17 made of a conductive metal such as Al is formed on each side surface and bottom surface of the head base 5 so as to be electrically connected to the common electrode 8. Since the metal layer 17 is formed over the side and bottom surfaces of the head base 5 in a state of being electrically connected to the common electrode 8 as described above, the common connection of the common electrode 8 is substantially performed when the thermal print head is used. Acts as a part. Since the head base 5 of this embodiment is covered with the conductive metal layer 17 covering the side and bottom surfaces thereof,
By using a conductive adhesive containing silver particles or the like, electrical connection can be easily made on the circuit pattern of the circuit board 3 as shown in FIG. The mounting on the circuit board 3 can be performed by soldering, for example, by applying Ni plating on an Al metal film instead of the conductive adhesive.

In this embodiment, only the tip of the common electrode 8 (excluding the commonly connected common connection portion) is formed on the head base 5 and the common connection portion is provided on the side and bottom surfaces. 4A and 4B, the whole or a part of the common connection portion is formed on the surface of the head substrate 5 together with the tip as shown in FIGS. 4A and 4B. Of course it is possible. In FIG. 3, FIG.
Parts or elements that are the same as or similar to those in FIG. 3A and FIG. 3B are indicated by the same numbers.

Further, the metal layer 17 is formed so as to cover both the side and back surfaces of the head base 5, but instead, it is formed only on the side of the head base 5, and the metal film 17 on the side is formed.
May be connected to the circuit pattern of the circuit board 3. The head substrate 1 configured as described above is mounted on the circuit board 3 together with the driving IC 2, and the driving IC 2 thus mounted is placed between the corresponding individual electrode 9 of the head substrate 1. Wire bonding and necessary wiring processing are performed by a conductive wire such as gold, and further,
A protective film 18 for covering and protecting these driving ICs 2 and circuit patterns is provided.

In the thermal print head according to the present embodiment, the heat generating area 1 provided on the head substrate 1 is thus provided.
A common center line 12 is provided closer to the adjacent side surface 14 of the head base 5 than the top line 13 of the glaze layer convex portion, and the driving IC 2 is further provided on the head substrate 1 on which the heat generating region 11 is formed. Since it is mounted on the circuit board 3 as a separate body from the heat-sensitive medium 11, the contact angle of the heat-sensitive medium (the contact area between the surface of the head substrate 5 or the circuit board 3 and the platen roller) (E.g., an angle formed with a tangent line) within a range of, for example, 0 to 30 °, so that high printing efficiency can be obtained even when a color image is formed. The wires and the protective film 18 covering them are formed in the heating region 1.
5, a single platen roller B can be used for application to color printing, such as yellow, magenta, or the like, as shown in FIG. When performing image formation with three colors of cyan, the thermal print heads AY, AM, and AC according to the present invention can be easily provided at a contact angle of 0-30 ° with respect to the platen roller B, respectively. A large degree of freedom can be secured.

Next, a method of manufacturing the thermal print head according to the present embodiment will be described. First, a groove extending from the glaze layer to the inside of the substrate material is formed by a dicer along a division line for division from above a ceramic substrate material having a glaze layer formed on the upper surface and capable of taking a plurality of head substrates 5. Then, the substrate is heated to a temperature of about 850 ° C. for about 20 minutes, so that a flat portion 6a extending substantially parallel to the surface of the substrate material and a convex portion 6b rising near the groove higher than the flat portion are formed.
Can be obtained. In addition, as described above, the glaze layer replaces the convex portion 6b with the flat portion 6b.
May be formed so that the thickness is reduced in an arc shape in a cross-sectional view toward the side wall of the groove without being raised to the surface of the groove. A resistive film containing tantalum nitride as a main component is formed to a thickness of about 0.1 μm by reactive sputtering on the glaze layer 6 having such convex portions 6b, and a common electrode and an individual electrode are further formed thereon. After forming an Al film by sputtering for formation, the common electrode, individual electrodes, and A
The l film and the resistor film are removed by etching, and then the Al film in the portion where the heating region is to be formed is removed by etching, thereby forming the heating region 11 including the common electrode 8, the individual electrode 9, and the resistor film 7. . When the common electrode 8 is formed, as described above, it is desirable to form only the tip portion other than the common connection portion. However, the whole or a part of the common connection portion may be formed together with the tip portion. Good. After the necessary common and individual electrodes 8 and 9 and the heat generating region 11 are formed in this way, a protective film 16 for covering and protecting these electrodes and the exposed resistive film 7 of the heat generating region 11 is formed by S.
formed by laminating an iO2 film and a Ta2O5 film,
The substrate material is divided into individual head bases 5 along the division line, and the exposed end 8a of the common electrode is exposed to the side.

Next, a metal film 1 made of a conductive metal such as Al is electrically connected to the exposed end 8a of the common electrode.
7 is formed on each end face and back face of the head base 5 by sputtering. The sputtering of the metal film 17 is performed from the back side of the head base 5 so that the metal particles appropriately wrap around each end face side of the base, and have an appropriate layer thickness, for example, about 2 μm on the end face and the back face of the head base 5. It is formed to a layer thickness.

After forming the head substrate 1 as described above,
A circuit board 3 made of ceramic or the like, on which a circuit pattern made of a conductor is formed, is mounted in an electrically connected state using a conductive adhesive containing silver particles or the like.
After mounting the drive IC 2 on top and providing the necessary wiring, etc.,
Protective film 1 for covering and protecting these driving ICs 2 and wirings
By forming No. 8, the thermal print head according to the present embodiment can be obtained.

In the above embodiment, the metal layer 17 is provided on the end face and the back face of the base after the formation of the protective film. However, the present invention is not limited to this. It may be formed on the end face and the back face of the head base 5 so as to be connected to each other, and then the protective film 18 may be formed on the front side and the end face of the base in necessary regions.

[Brief description of the drawings]

FIG. 1 is a side view of a thermal printhead according to an embodiment of the present invention.

FIG. 2 is a sectional view of a head substrate of the thermal print head of FIG.

FIG. 3 is an enlarged plan view of a main part of the head substrate of FIG. 2;

FIG. 4 is an enlarged plan view of a main part of a modified example of the head substrate of FIG. 2;

FIG. 5 is a diagram showing an application of the thermal print head of the present invention to color image formation.

FIG. 6 is a side view of a conventional thermal print head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Head board 2 Drive IC 3 Circuit board 5 Head base 6 Glaze layer 7 Resistor film 8 Common electrode 9 Individual electrode 10 Head substrate surface 11 Heat generation area 12 Common center line 13 Top line 15 Heat sensitive medium 17 Metal layer

Continuation of the front page (56) References JP-A-4-338556 (JP, A) JP-A-1-299060 (JP, A) JP-A-2-27344 (JP, U) JP-A 64-4647 (JP) , U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) B41J 2/345 B41J 2/335

Claims (1)

(57) [Claims] 1. A flat portion having a substantially flat surface and the flat portion
A head substrate on which a glaze layer having a raised protruding portion is formed, a common electrode formed on the head substrate and having a common connection portion connected in common, and an individual formed corresponding to the common electrode. An electrode, a heating resistor formed between the corresponding common and individual electrodes and on the convex portion of the glaze layer so as to provide a heating area, and a driving resistor electrically connected to the individual electrode. IC and
Wherein the heating area has a common center line at the head.
A thermal print formed so as to extend from a top line of a convex portion of the glaze layer on the substrate to a position closer to an end face of the head substrate and higher than an upper surface of the driving IC. head.