JPH11129513A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of crease or kink on a recording medium by a constitution wherein a plurality of grooves are formed on a head cover where the recording medium is slidably contacted such that the grooves are radially provided in a sliding direction of the recording medium. SOLUTION: In a thermal head, a head substrate 1 having a heating resistor array 2 consisting of a plurality of heating resistors provided on the top face and a printed wiring plate 3 having wiring conductors to be electrically connected to the heating resistors are provided on a radiation plate 4. The connection sections between the head substrate 1 and printed wiring plate 3 is covered by a head cover 5 fixed to the radiation plate 4. When printing an image, the recording medium is slidably contacted to a part of the surface of the head cover 5, then the recording medium is guided on the heating resistor array 2. A plurality of grooves 6 or projection lines are radially provided on the surface A of the head cover 5, where the recording medium is contacted, in a sliding direction Z of the recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Detailed description of the invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head incorporated as a printer mechanism for a word processor, a facsimile or the like.

[0003]

2. Description of the Related Art Conventionally, as shown in FIG. 6, a thermal head incorporated as a printer mechanism such as a word processor has a head substrate 11 having a heating resistor array 12 composed of a plurality of heating resistors on an upper surface, and the heating substrate. A printed wiring board 13 having a wiring conductor electrically connected to a resistor via a conductive layer or the like (not shown) is placed on a heat dissipation plate 14 made of aluminum. 13 is covered with a head cover 15 attached to the heat sink 14 by screws or the like.

In such a thermal head, for example, when an ink ribbon is used as a recording medium, a predetermined power is applied to a heating resistor of a head substrate 11 via a wiring conductor of a printed wiring board 13 so that a printing signal is applied to the heating resistor. And Joule heat is individually generated based on the above, the generated heat is conducted to the ink ribbon conveyed on the heating resistor array 12, and the ink of the ink ribbon is heated and melted and transferred to paper. Thus, a predetermined print is formed.

The head cover 15 not only serves to protect the connection between the head substrate 11 and the printed wiring board 13 from the application of an external force, but also allows the recording medium such as an ink ribbon to slide on the surface thereof. The recording medium sliding contact surface A 'also has a role of guiding the heating resistor array 12 and is formed to be a flat surface.

[0006]

However, in this conventional thermal head, if the head cover 15 is warped or the mounting position is slightly displaced, the ink ribbon is moved to the recording medium sliding surface A 'of the head cover 15. When the ink ribbon was brought into sliding contact, "wrinkles" and "streaking" occurred on the ink ribbon. Such "wrinkles" and "skews" of the ink ribbon often remain as they are without being removed even when the ink ribbon is conveyed onto the heating resistor array 12.
In this case, the ink ribbon cannot be pressed with substantially the same strength over the length direction of the heating resistor array 12, which causes "density unevenness" or "blurring" of the print.

[0007]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and a thermal head according to the present invention comprises a head substrate having a plurality of heating resistors attached and arranged on an upper surface thereof.
A printed wiring board having a wiring conductor electrically connected to the heating resistor is mounted on a heat sink, and a connection between the head substrate and the printed wiring board is formed by a head cover attached to the heat sink. A thermal head, comprising: a recording medium that slides on a partial surface of the head cover during printing, thereby guiding the recording medium onto the heating resistor array. A plurality of grooves or a plurality of ridges are formed on the surface of the recording medium so as to radially expand in the sliding direction of the recording medium.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a perspective view showing one embodiment of the thermal head of the present invention, FIG. 2 is a side view of the thermal head of FIG. 1 viewed from the X direction, and FIG. 3 is a cross-sectional view of a head cover used in the thermal head of FIG. Yes, 1 is a head substrate,
2 is a heating resistor, 3 is a printed wiring board, 4 is a heat sink, 5 is a head cover, and 6 is a groove formed on the surface of the head cover 5.

The head substrate 1 has a structure in which a heating resistor array 2 and the like are attached to an upper surface of an insulating substrate made of alumina ceramic or the like.

The heating resistor array 2 is formed by linearly arranging a plurality of heating resistors made of tantalum nitride or the like.
When external power is applied through a conductive layer or the like (not shown) or a wiring conductor or the like of the printed wiring board 3 described later, Joule heat is generated, and a predetermined temperature required to melt the ink of the ink ribbon I, for example, The temperature is 300 ° C.

Such a heating resistor array 2 is formed by employing a conventionally known sputtering method or photolithography technique so that a plurality of heating resistors are linearly arranged on the upper surface of the insulating substrate. The head substrate 1 is manufactured by the attachment and formation.

On the upper surface of the head substrate 1, in addition to the heating resistor array 2, a driver IC for controlling the energization of the heating resistor, and power and signals are supplied to the driver IC and the heating resistor. And a plurality of conductive layers for providing the same. Some of these conductive layers are:
One end thereof is led out to one side of the head substrate 1 and is electrically connected to a wiring conductor of a printed wiring board 3 described later.

On the other hand, the printed wiring board 3 has a plurality of wiring conductors electrically connected to the heating resistor of the head substrate 1 described above. Specifically, by connecting the wiring conductor of the printed wiring board 3 to a conductive layer led out to one side of the head substrate 1 via a brazing material such as solder, the head substrate 1
It is designed to be electrically connected to the heating resistor of
The printed wiring board 3 supplies electric power and signals from an external electric circuit to the heating resistor and the like via the above-described conductive layer and the like.

Incidentally, as such a printed wiring board 3, for example, a plurality of wiring conductors formed of copper foil or the like are adhered to a flexible film made of a polyimide resin, and one end of each of these wiring conductors is provided. And a flexible printed wiring board or the like, in which is led out to one side of the film.

The printed wiring board 3 and the above-mentioned head substrate 1 are mounted on a heat radiating plate 4 made of metal such as aluminum or SUS.

The heat radiating plate 4 supports the head substrate 1 and the printed wiring board 3 on the upper surfaces thereof, and absorbs a part of the heat in the head substrate 1 so that the temperature of the head substrate 1 is reduced by the temperature of the heating resistor 2. It functions to effectively prevent the temperature from being excessively high due to the generated heat. For example, it is manufactured by forming an ingot (a lump) made of aluminum or the like into a predetermined shape by employing a conventionally known metal working method.

A head cover 5 is attached to the heat radiating plate 4 so as to cover the connecting portion between the head substrate 1 and the printed wiring board 3 described above. The head cover 5 includes a connection portion between the head substrate 1 and the printed wiring board 3,
Specifically, by covering the solder joint between the conductive layer of the head substrate 1 and the wiring conductor of the printed wiring board 3, the portion functions as a protection member for protecting this portion from the application of external force, and the ink ribbon I is formed on the outer surface. The ink ribbon I has a function as a guide member that guides the ink ribbon I onto the heating resistor array 2 by being slid on a part (recording medium sliding contact portion A), and has a predetermined shape made of metal such as aluminum or SUS. It is formed to form.

Further, a plurality of grooves 6 are formed on the recording medium sliding contact surface A of the head cover 5 so as to radially extend in the sliding direction Z of the ink ribbon I or the like.

Since these grooves 6 are formed so as to radially spread in the sliding direction Z of the ink ribbon I or the like, when the ink ribbon I is brought into sliding contact with the sliding surface A of the head cover 5, the ink both sides of the ink ribbon I by radial grooves 6 described above is the ribbon I (Y _1, Y ₂ direction in FIG. 3)
When the head cover 5 is warped or the mounting position of the head cover 5 is slightly shifted, "wrinkles" or "skews" are generated on the ink ribbon I. No ink ribbon I
Is always conveyed onto the heating resistor array 2 in a good state, and a predetermined print without "density unevenness" or "blurring" can be formed.

Further, the plurality of grooves 6 described above correspond to the ink ribbon I.
Are formed radially in the sliding contact direction Z, and each portion of the ink ribbon I passes over at least one or more grooves 6 at the time of printing. Even if dust adheres to the lower surface of the ribbon I (head cover 5 side), the dust can be dropped into the groove 6 by hitting the side surface or the corner of the groove 6. This reduces the possibility of dust being caught between the heating resistor array 2 and the ink ribbon I, and can also improve the reliability of the thermal head. In order to reliably remove such dust on the head cover 5, it is preferable to attach a rubber, sponge, ceramic blade, or the like to the edge of the groove 6 on the side of the heating resistor row 2.

Further, if the corner formed by the recording medium sliding contact surface A of the head cover 5 and the side surface of the groove 6 is an R surface, no sharp corner is formed from the sliding contact surface A. When the sheet is brought into sliding contact with the sliding surface A of the head cover 5, the lower surface of the ink ribbon I is not damaged, and a good print can be formed on paper. The radius of curvature of such an R surface is formed in the range of 0.1 to 0.5 mm. Therefore, it is preferable that the corner formed by the recording medium sliding contact surface A of the head cover 5 and the side surface of the groove 6 be an R surface.

The head cover 5 as described above is manufactured by forming a plate made of a metal such as aluminum or SUS into a predetermined shape by employing a conventionally known press working method. On the other hand, it is attached to the heat sink 4 by screwing.

Thus, in the above-described thermal head, for example, when the ink ribbon I is used as a recording medium, a predetermined electric power is applied to the heating resistor of the head substrate 1 via the wiring conductor of the printed wiring board 3, and the heating resistor is heated. The body is caused to selectively generate Joule heat based on the print signal, and the generated heat is transferred to the ink ribbon I conveyed onto the heating resistor array 2.
And heats and melts the ink of the ink ribbon I and transfers it to paper to form a predetermined print.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the gist of the present invention.

For example, in the above-described embodiment, a plurality of grooves 6 are formed on the recording medium sliding contact surface A of the head cover 5 so as to radially extend in the sliding direction of the recording medium I. As shown in FIG. 4, a plurality of ridges 7 may be formed on the recording medium sliding contact surface A of the head cover 5 'so as to radially spread in the sliding direction of the recording medium. In this case, an R surface having a radius of curvature of 0.2 to 1.0 mm is provided at the tip of each ridge 7 so that the recording medium is not damaged even if the recording medium comes into contact with the ridges 7.

In the embodiment shown in FIG. 4, only a few ridges 7 are provided on the sliding surface A of the head cover 5 ', but instead of this, as shown in FIG. The contact surface A may be filled with a large number of ridges 7 so that the recording medium contacts only the ridges 7. In this case, the head cover 5 has the same effect as the above-described embodiment. Has the advantage that the sliding contact with the recording medium becomes smoother.

Further, in the above embodiment, the center line average roughness Ra is 100 to 200 μm on the bottom surface of the groove 6 of the head cover 5.
If the irregularities are provided, dust falling into the groove 6 is easily caught on the bottom surface of the groove 6, and it is possible to effectively prevent the dust from reattaching to the recording medium. Therefore, the center line average roughness Ra is provided on the bottom surface of the groove 6 of the head cover 5.
It is preferable to provide the unevenness of 100 to 200 μm.

[0028]

According to the thermal head of the present invention, a plurality of grooves are formed on the sliding surface of the head cover so as to radially expand in the sliding direction of the recording medium.
When the recording medium is brought into sliding contact with the sliding surface of the head cover,
A force is applied to the recording medium by the radial grooves to spread the recording medium to both sides, so that even if the head cover is warped or the mounting position of the head cover is slightly displaced, the recording medium is applied to the recording medium. There is no occurrence of "wrinkles" or "distortion", and a predetermined print without "density unevenness" or "blurring" can be formed by always transporting the recording medium on the heating resistor array in a good state. .

According to the thermal head of the present invention, the plurality of grooves are formed radially in the sliding direction of the recording medium. Since dust passes through the upper surface, even if dust adheres to the lower surface (head cover side) of the recording medium due to the action of static electricity or the like, the dust hits the side surface or the corner of the groove and falls into the groove. be able to. As a result, dust is less likely to be caught between the heating resistor array and the recording medium, and the reliability of the thermal head is improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a thermal head of the present invention.

FIG. 2 is a side view of the thermal head of FIG. 1 viewed from an X direction.

FIG. 3 is a sectional view of a head cover used for the thermal head of FIG. 1;

FIG. 4 is a perspective view showing another embodiment of the thermal head of the present invention.

FIG. 5 is a perspective view showing another embodiment of the thermal head of the present invention.

FIG. 6 is a perspective view of a conventional thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Head board 2 ... Heating resistor 3 ... External wiring board 4 ... Heat sink 5 ... Head cover 6 ... Groove

Claims (1)

[Claims] 1. A head substrate having a heating resistor array comprising a plurality of heating resistors on an upper surface and a printed wiring board having a wiring conductor electrically connected to the heating resistor are mounted on a heat sink. And a connecting portion between the head substrate and the printed wiring board is covered with a head cover attached to a heat radiating plate. In printing, the recording medium is slidably in contact with a partial surface of the head cover. A plurality of grooves or a plurality of ridges radially extending in the sliding direction of the recording medium are formed on the recording medium sliding contact surface of the head cover. A thermal head characterized in that: