JP2629007B2 - Thermal head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head of a thermal printing apparatus used as a printer of a word processor or a typewriter, or used in a facsimile receiver or the like.

Prior Art A typical prior art is shown in FIG. The thermal head 1 basically includes a head substrate 2 and a head cover 3 that covers the head substrate 2.
The head substrate 2 has a large number of heating resistors 4 arranged in one row for forming heating dots, and external terminals 5 for applying an electric signal for causing the heating resistors 4 to selectively generate heat.
Terminals 7 a formed on the wiring conductors 7 of the wiring board 6 are superimposed on the external terminals 5 of the head substrate 2, and both are mounted on the support plate 8. The head substrate 2 and the wiring substrate 6 are sandwiched and pressed by the head cover 3 and the support plate 8.

The thermal recording paper 9 is fed in a direction (arrow A direction) perpendicular to the row in which the heating resistors 4 are arranged. When the recording paper 9 is fed, the heating resistor 4 is selectively energized and generates heat, thereby forming dots on the recording paper 9 pressed by the platen 10 and printing.

The heating resistors 4 are grouped into a plurality of groups, and the electrodes 11 connected to the heating resistors 4 are connected to integrated circuit elements 14 for each group provided on the substrate 12. The integrated circuit element 14 is supplied with an electric signal from an external electric circuit via an external terminal 5 formed on the substrate 12. The integrated circuit element 14 is covered with a silicone rubber 15 having excellent water resistance and chemical resistance in order to protect the integrated circuit element 14 and its connection.

The wiring conductor 6 is formed by printing the wiring conductors 7 on the surface of the film 16 made of a synthetic resin having electrical insulation and facing the head substrate 2. The tip of the wiring conductor 7 is a terminal 7a. The external terminal 5 and the terminal 7 a are overlapped and pressed by a pressing member 17 fixed to the head cover 3. The pressing member 17 is made of an elastic synthetic resin material, and extends over the entire length of the region where the terminals 5, 7a are arranged.

An insertion hole 18 is formed in the head cover 3, and an insertion hole 19 is formed in the wiring board 6, and a bolt 20 is loosely inserted into these insertion holes 18, 19. A screw hole 21 is formed in the support plate 8, and the bolt 20 is screwed into the screw hole 21. Therefore, when the terminal 7a of the wiring board 6 and the terminal 5 of the head substrate 2 are placed on the support plate 8 so as to overlap with each other, and the head cover 3 is fixed to the support plate 8 with bolts 20, both terminals 5, 7a become Head cover 3 and support plate 8
Are connected by being sandwiched and pressed.

Problems to be Solved by the Invention The terminals 5 of the head substrate 2 and the terminals 7a of the wiring substrate 6 are connected by being pressed by the pressing members 17 as described above. Therefore, in order to prevent the connection state from shifting due to an external impact force, the pressing force acting on the lower side of the pressing member 17 must be increased, and the pressing member 17
The thickness d4 of the upper head cover 3 must be formed so as to withstand the pressing force. Also, a pressing member
The pressing force on 17 can be obtained by screwing the bolt 20, but since it is necessary to prevent the connection between the terminals 5, 7a from being hindered, the bolt 20 must be separated from the vicinity of the terminals 5, 7a. It is necessary to provide in the position where it was. Therefore, the thickness d5 between the bolt 20 and the pressing member 17 in the head cover 3 must also be increased to some extent.

Further, the integrated circuit element 14 is covered with a silicone rubber 15 to protect it. Since this silicone rubber 15 is soft, when a slight external force acts,
There is a risk that the integrated circuit element 14 will be crushed and that the connection between the terminals 5, 7a will be disconnected. Therefore, the tip of the head cover 3 extends so as to cover above the silicone rubber 15. For this reason, the head cover 3 becomes large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal head which can solve the above-mentioned problems, can strengthen the connection state of each terminal of the head substrate and the wiring substrate with a simple configuration, and can further reduce the configuration. To provide.

Means for Solving the Problems The present invention provides a head substrate on which a heating resistor array and an integrated circuit element for selectively driving the heating resistor array are mounted, a wiring substrate connected to the head substrate, A head cover that covers a connection portion with the wiring substrate and is inclined so that an end portion on the head substrate side is lowered; and a support plate on which the head substrate and the wiring substrate are mounted on an upper surface, and the head cover is attached. A thermal head for forming a print while sequentially transporting a thermosensitive recording paper from above a head cover onto a row of heating resistors of a head substrate, wherein the integrated circuit element on the head substrate is formed of a hard material having a Shore hardness of 60 or more. And a rounded portion formed at the tip of the inclined portion of the head cover in the direction of transport of the thermal recording paper than the top of the protective member. And arranged on the side, a thermal head is characterized in that the formation of the guide portion of the recording paper in the inclined portion of the head cover and the protective member.

According to the present invention, the integrated circuit element is covered with a protective member having a mountain-shaped cross section and made of a hard material having a Shore hardness of 60 or more. As a result, the integrated circuit element and the connection portion thereof can be protected only by this protection member, and there is no need to cover the protection member with a head cover. Therefore, the size of the head cover can be reduced. Further, since it is not necessary to cover the protection member with the head cover, the rounded portion at the tip of the inclined portion of the head cover is arranged upstream of the top of the protection member in the direction of transport of the thermal recording paper, and the inclined portion of the head cover and the protection Since the guide portion of the thermal recording paper is formed by the members, the configuration of the apparatus can be simplified, the size can be reduced, and the thermal recording paper is not damaged or caught, The thermosensitive recording paper can always be stably transported in a good state.

Embodiment FIG. 1 is a longitudinal sectional view showing the structure of a thermal head 31 according to an embodiment of the present invention, and FIG.
FIG. 3 is an exploded perspective view of FIG. The thermal head 31 is a heating resistor
A head substrate 34 having an integrated circuit element 32, a wiring substrate 35, a reinforcing plate 36 for reinforcing the wiring substrate 35, and a reinforcing plate 36;
And a support plate 37 on which the head substrate 34 is placed, and a head cover 38 covering these.

In the head substrate 34, a heating resistor 32 is formed on a flat substrate 39 made of an electrically insulating material, for example, an alumina-based ceramic, by vapor deposition as a thin film technique or screen printing as a thick film technique. Conductors 40 and 41 are formed as electrodes on the heating resistor 32, and power is applied to the conductors 40 and 41 to cause the heating resistor 32 to generate Joule heat.

The heating resistors 32 are grouped into a plurality of groups, and the conductors 40 connected to the heating resistors 32 are connected to the integrated circuit elements 33 provided for the respective groups provided on the substrate 39. The integrated circuit element 33 is supplied with an electric signal from an external electric circuit through a conductor 44 formed on the substrate 39. The conductor 44 includes a conductor portion 42 and an external terminal 43, and the integrated circuit element 33 selectively heats the heating resistor 32 via the conductor 40 by an electric signal from the external terminal 43. Then, energizing power is supplied to the selected heating resistor 32.

The wiring substrate 35 includes a substrate 45 made of, for example, a flexible synthetic resin material having an electrical insulation property, and a surface (a lower surface in FIG. 1) of the substrate 45 facing the head substrate 34. And a plurality of wiring conductors 48 formed to individually correspond to the terminals 43. The wiring conductor 48
Terminals individually connected to the conductor portion 46 and the external terminal 43
47.

The terminals 47 are individually connected to the external terminals 43 by solders 49. Therefore, the two terminals 47 and 43 can maintain a strong connection state without being pressed by the pressing member as described in the section of the related art, and the connection state can be shifted by an external impact force. Is prevented.

The reinforcing plate 36 for reinforcing the wiring board 35 is made of a material such as paper phenol or glass epoxy.

The head substrate 34 and the reinforcing plate 36 are bonded to a supporting plate 37 by a soft adhesive 50 described later. The support plate 37 is made of, for example, aluminum, and the head substrate 34
Functions as a heat radiating plate for radiating a part of the heat generated by the resistance heating element 32 to prevent the temperature of the head substrate 34 from becoming abnormally high.

The integrated circuit element 33 is covered with a protective member 51 made of a hard material having a Shore hardness of 60 or more, for example.
The protection member 51 protects the panel from external impact. If the Shore hardness is less than 60, it is too soft, and sufficient protection against the external force of the integrated circuit element 33 and its connection portion cannot be provided. The surface roughness of the protective member 51 is formed smoothly so as to be, for example, 60 μm or less, so that the heat-sensitive recording paper 52
Slides smoothly on the protection member 51,
Is suppressed. When the surface roughness exceeds 60 μm,
The surface of the protective member 51 comes into frictional contact with the thermal recording paper 52 to make the thermal recording paper 52 fluff, and the protective member 51 wears faster.

The head cover 38 is made of, for example, a polypropylene-based synthetic resin material, and has an inclined portion for guiding the thermal recording paper 52.
53, a top 54, and a support piece 55 for supporting the head cover 38.
And The lower surface of the top 54 of the head cover 38 (first
On the lower side of the figure, two to three right columnar projections 56 are provided on the mounting base 57 at regular intervals in the longitudinal direction (perpendicular to the plane of FIG. 1).

Insertion holes 58 and 59 are formed in the wiring board 35 and the reinforcing plate 36 at positions corresponding to the positions where the protrusions 56 are provided. The support plate 37 has a notch on the left side in FIG.
An attachment portion 61 formed by the notch 60 has an attachment hole 62 for attaching the projection 56.
Are formed.

The projection 56 includes a straight cylindrical shaft portion 63 and a head portion 64, and the head portion 64 has a notch 65 that is open toward its free end.
Are formed to extend in the axial direction of the shaft portion 63. head
A guide inclined surface 66 is formed at the free end of the head 64, and a support inclined surface 67 is formed near the shaft 63 of the head 64. The bottom 65a of the notch 65 extends closer to the base end of the shaft 63 than the inclined support surface 67.

The projection 56 having such a configuration is inserted into the insertion holes 58 and 59 formed in the wiring board 35 and the reinforcing plate 36, and is attached to the attachment hole 62 of the attachment portion 61. When the projection 56 is inserted into the insertion holes 58 and 59 and the mounting hole 62, the head 64
The free end of the notch 65 is guided and inserted through the guide inclined surface 66 of the head 64 with the free end thereof slightly closed. In the state where the projection 56 is mounted, the lower end of the mounting hole 62 is in contact with the support inclined surface 67 of the head 64, and in this state, the notch 65 is opened downward by the force of the notch 65. The repulsive force acts on. As a result, the end surface 57a of the mounting base 57 is
To the wiring board 35, the reinforcing plate 36, and the supporting plate.
37 is pressed and held between the end face 57a and the head 64 of the projection 56.

Further, since the wiring board 35 is pressed downward by the elastic force of the projection 56, when printing is continuously performed,
Even when the heat of the heat generating resistor 32 is conducted to the wiring board 35 to cause a bending or the like, the bending state is suppressed by the elastic force of the projection 56.

The notch 60 of the support plate 37 is a free end surface of the protrusion 56 when the head 64 of the protrusion 56 is attached to the support plate 37.
56a is flush with the end face 37a of the support plate 37 or the lower end face 37
The support plate 37 is formed so as to be on the inner side in the thickness direction of the support plate 37 than a.

The tip of the inclined portion 53 of the head cover 38 has a rounded portion 53a.
And is located on the upstream side (left side in FIG. 1) in the transport direction of the thermal recording paper 52 from the top of the protective member 51 of the integrated circuit 33, and guides the thermal recording paper 52 together with the protective member 51. The guide unit is configured. Further, the rounded portion 53a is formed in a circular arc shape having a roundness of about 0.3 to 0.4 mm in a cross section perpendicular to the axis. This is to prevent the thermal recording paper 52 guided by the inclined portion 53 from being damaged. On the other hand, as described above, the protective member 51 for protecting the integrated circuit element 33 has a smooth surface with a surface roughness of 60 μm or more, and the heat-sensitive recording paper 52 conveyed from the guide member 53 has Protection member 51
When the contact is made, the leading end of the thermal recording paper 52 is prevented from fluffing.

The thermal recording paper 52 guided by the protection member 51 is pressed against the heating resistor 32 by a rubber platen 68 and is conveyed in the direction of arrow P.

As described above, in the present invention, a hard material is used for the protection member 51 for protecting the integrated circuit element 33. Therefore, the integrated circuit element 33 can be protected by only the protection member 51, and the protection member 51 Need not be covered by the head cover 38. Therefore, the inclined portion of the head cover 38
53 can be shortened, can be configured as a guide for the thermal recording paper 52 together with the protective member 51, and the inclined portion 53 of the head cover 38 can be reduced in size.

Further, since the head cover 38 is attached to the support plate 37 by the projection 56, not only the structure is simplified, but also the bending of the wiring board 35 can be prevented by the downward elastic force of the projection 56. Further, since the terminals 47 of the wiring board 35 and the terminals 43 of the conductors 44 are connected by solder 49, it is not necessary to apply an external force separately in order to maintain these connection states. As described above, the thickness of the corresponding portion of the head cover 38 can be made as small as possible, and the related portion, that is, the portion between the connection position of the terminals 43 and 47 and the portion where the projection 56 is formed, is provided. Of the head cover can be made as small as possible. In this way, according to the present invention, the head cover 38 can be downsized, and accordingly, the configuration of the thermal head 31 can be downsized.

The head substrate 34 and the support plate 37 are bonded by the soft adhesive 50 as described above. Here, the reason why the soft adhesive is used is that the difference in thermal expansion coefficient between the head substrate 34 and the support plate 37 is absorbed by the soft adhesive 50. The head substrate 37 is not only bonded to the support plate 37 with the soft adhesive 50 but also fixed near the longitudinal center of the head substrate 37 with a hard adhesive (lumps) at short intervals. This is to prevent the position of the head substrate 34 from changing with respect to the support plate 37 due to thermal expansion.

FIG. 3 is a graph showing an experimental result for obtaining a suitable shear adhesive strength of the soft adhesive 50. Hereinafter, an experimental method performed by the present inventor and a result thereof will be described.

The head substrate 34 provided with the heating resistor 32 may be heated to, for example, about 80 degrees when continuous printing is performed. At this time, the amount of heat of the head substrate 34 is transmitted via the adhesive 50 to the support plate 37 serving as a radiator plate. In such a case, the head substrate 34 and the support plate 37 are curved as shown in FIG. 4 due to the difference in thermal expansion coefficient between the substrate 39 made of alumina ceramic material and the aluminum support plate 37. I do. It is considered that the maximum displacement d2 caused by such bending changes depending on the shearing adhesive strength of the adhesive bonding the head substrate 34 and the support plate 37.

Then, the present inventor used various adhesives to obtain the shear adhesive strength, that is, the adhesive strength when a force was applied to the head substrate 34 and the support plate 37 in the directions of arrows A1 and A2 shown in FIG. Investigating the strength, when using adhesives having various shear bond strengths, the maximum displacement in the curved state
d2 was measured.

The support plate 37 as a heat sink is 19 mm wide and 240 m long
m, using a thickness of 5.0 mm, the alumina-based ceramic substrate 39, width 18.8 mm, length 232 mm, thickness 0.65 mm
The size was used. In this experiment, room temperature 25
The head substrate 34 ° C. was heated up to the expected maximum temperature of 80 ° C., that is, the difference from the normal temperature reached 55 ° C., and the maximum displacement d2 in the curved state was measured. This measurement result is the third
This is shown in the graph of the figure.

Referring to FIG. 3, the above-mentioned shear adhesive strength is 25 kg / cm ²
When the following adhesive is used, the maximum displacement d2 is 0.
And at 1mm or less, the shear adhesive strength exceeds 25 kg / cm ^2,
The maximum displacement d2 rises sharply and the shear bond strength is 50
When an adhesive of kg / cm ² or more is used, the maximum displacement d2 is approximately 1.2 mm, and thereafter becomes saturated. on the other hand,
The allowable range of the maximum displacement amount d2 in which a normal printing operation is performed using the curved head substrate 34 is 0.1 mm. Therefore, as is clear from the graph of FIG.
The shear adhesive strength of the adhesive used for the soft adhesive 50 is 25 kg
/ cm ² or less is desirable.

The present inventor conducted the following experiment. That is, as shown in FIG.
The strength of peeling 34 in the direction perpendicular to the adhesive surface (the direction of arrow B1 in FIG. 6), that is, the so-called 90 ° peel strength, was measured using various adhesives. As a result, the strength is 25
It has been found desirable to use an adhesive that is at least 200 g per mm. That is, if the strength is less than 200 g per 25 mm length, the adhesive strength between the head substrate and the support plate 37 cannot be said to be sufficient, and the durability of the thermal head 31 will be deteriorated.

The thickness of the soft adhesive 50 is desirably 10 to 200 μm. That is, the thickness of the adhesive 50 is 10 μm
If it is less than this, it cannot be said that the adhesive strength for bonding the head substrate 34 and the support plate 37 is sufficient. On the other hand, when the thickness is 20
If the thickness exceeds 0 μm, the heat of the heated head substrate 34 cannot be sufficiently transmitted to the support plate 37, and the head substrate 34 becomes excessively heated, and the quality of printing deteriorates. That is, if the head substrate 34 does not radiate heat appropriately,
An area other than the desired area of the heating resistor 32 is overheated, the desired printing operation is not performed, and the quality of printing deteriorates. For this reason, it is desirable that the thickness of the adhesive 50 be about 10 to 200 μm. Further, as a material of the adhesive 50, for example, an acrylic adhesive may be used.

As described above, in the present embodiment, the head substrate 34 and the support plate 37 are bonded to each other by the adhesive 50 having the above-described properties. In a state where the temperature of the substrate 34 and the support plate 37 is increased, even if the substrate 34 and the support plate 37 are curved due to a difference in their thermal expansion coefficients,
The difference in thermal expansion is absorbed by the soft adhesive 50, and the maximum displacement d2 due to bending is suppressed to a desired level or less, so that printing can be performed continuously without deteriorating the quality of printing.

Effect As described above, according to the present invention, the integrated circuit element is covered with the protective member made of a hard material having a Shore hardness of 60 or more. Therefore, the integrated circuit element and its connection portion are protected only by this protective member. Therefore, there is no need to cover the head cover on the protection member. Therefore, the size of the head cover can be reduced. Also, since there is no need to cover the protection member with the tip of the head cover,
A guide portion for the thermal recording paper can be formed by the rounded portion at the tip of the inclined portion of the head cover and the protective member, which simplifies the configuration of the apparatus and enables downsizing. It can be transported stably in a good state.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a thermal head 31 according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of the thermal head 31, FIG. 3 is a graph showing experimental results of the present inventor,
4 to 6 are diagrams for explaining the experimental technique of the present inventor, and FIG. 7 is a vertical sectional view of a typical prior art. 31: Thermal head, 32: Heating resistor, 33: Integrated circuit element, 34: Head substrate, 35: Wiring substrate, 37 ...
Support plate, 38: Head cover, 39: Substrate, 40, 41 ...
Conductor, 43 external terminal, 47 terminal, 49 solder, 50
… Soft adhesive, 51… Protective member, 52… Thermal recording paper, 53
…… Slope section, 56 …… Protrusion, 57 …… Mounting base section

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-151466 (JP, A) JP-A-61-94773 (JP, A) JP-A-60-19549 (JP, A) JP-A-62 270347 (JP, A) Fully open 63-39542 (JP, U) Fully open 63-197143 (JP, U) Fully open 61-181739 (JP, U) Fully open 59-68956 (JP, U)

Claims (1)

(57) [Claims] 1. A head substrate on which a heating resistor array and an integrated circuit element for selectively driving the heating resistor array are mounted, a wiring substrate connected to the head substrate, and a connecting portion between the head substrate and the wiring substrate. A head cover that is covered and inclined so that the end portion on the head substrate side is lowered; and a support plate on which the head substrate and the wiring substrate are mounted on the upper surface and to which the head cover is attached. A thermal head for forming a print while sequentially transporting from a head cover onto a heating resistor array of a head substrate, wherein the integrated circuit element on the head substrate has a mountain-shaped cross section made of a hard material having a Shore hardness of 60 or more. The head cover is covered with a protective member, and a rounded portion formed at the tip of the inclined portion of the head cover is disposed upstream of the top of the protective member in the transport direction of the thermal recording paper. A thermal recording paper guide formed by the inclined portion and the protective member.