JP2951178B2 - Structure of line type 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 structure of a line type thermal print head which is used for facsimile and the like and which has a high printing density.

[0002]

2. Description of the Related Art Conventionally, a line type thermal print head of this type has been described in, for example, Japanese Patent Application Laid-Open No. 60-192666, and has a head substrate 11 made of ceramic or the like as shown in FIGS. On the upper surface, a large number of first electrode patterns 12 arranged in a comb shape, and a large number of second electrode patterns 13 similarly arranged in a comb shape, 13 are formed so as to enter between the first electrode patterns 13, and a thick-film heating resistor 14 extending in a line shape crosses both the first electrode pattern 12 and the second electrode pattern 13. By forming the heating resistor 14, a portion of the heating resistor 14 between the first electrode pattern 12 and the second electrode pattern 13 is formed by one print dot 14a (in FIG. Those constructed as a portion).

The printing density of the line type thermal print head is controlled by the linear heating resistor 14.
Is determined by the number of print dots 14a present per unit length along the longitudinal direction of the first electrode pattern 12 and the first electrode pattern 12 and the second electrode pattern 13 in order to increase the print density. S and the first electrode patterns 12 and the second electrode patterns 13
It is necessary to reduce the pitch interval P between them.

[0004]

By the way, each of the first
As is well known, the electrode patterns 12 and the second electrode patterns 13 are formed by a photolithography method in which a thin metal layer formed on the upper surface of the head substrate 11 by screen printing or sputtering is photoetched. Therefore, the pitch interval P in each of the first electrode patterns 12 and each of the second electrode patterns 13
And the width dimension S indicate the printing density, for example, 400 dpi.
(The number of print dots 14a per inch along the longitudinal direction of the linear heating resistor 14 is 400
) Can be relatively easily adapted to a high density.

However, on the other hand, the linear heating resistor 14 is, as shown in FIG.
4, a screen plate A having a slit slot A1 having a width W corresponding to the head substrate 11 on which the first electrode patterns 12 and the second electrode patterns 13 are formed in advance. Is formed by a screen printing method in which the material paste of the heating resistor 14 is filled in the slit slot A1 and then the screen plate A is removed. According to this screen printing method, the heating resistor 14 The minimum value in the width dimension W is limited to 130 to 140 microns, and cannot be reduced below this value (if it is less than this, a part or all of the paste filled in the slit slot A1 may be screened). When the plate A is removed from the head substrate 11, the heating resistor 14 is removed together with the screen. Yield rate of in forming at printing is greatly reduced).

Therefore, the pitch P between the first electrode patterns 12 and the second electrode patterns 13 is set to 40
Even if the print density is set to 31.75 microns, which can realize a print density of 0 dpi, each print dot 14a formed between each first electrode pattern 12 and each second electrode pattern 13
Can not be smaller than the minimum width dimension W of the heating resistor 14 in the direction perpendicular to the longitudinal direction of the heating resistor 14.
Is a rectangle elongated in the longitudinal direction of the linear heating resistor 14, in other words, the print dot size in the direction perpendicular to the longitudinal direction of the linear heating resistor 14 is Is much larger than the print dot size along.

That is, in the conventional line type thermal print head, since the print dot size in the direction perpendicular to the longitudinal direction of the linear heating resistor cannot be reduced, the print density is increased.
There was a problem that there was a certain limit value.

The present invention is directed to a line-type printing apparatus capable of reliably increasing the printing density without increasing the printing dot size in the direction perpendicular to the longitudinal direction of the linear heating resistor in each printing dot. An object of the present invention is to provide a thermal print head.

[0009]

In order to achieve this technical object, the present invention provides a method of forming a first electrode pattern on a top surface of an insulating head substrate, the first electrode pattern being arranged in a comb shape, and the first electrode pattern being arranged in a comb shape. The two-electrode pattern is the second of these two electrode patterns.
Each of the electrode patterns is formed so as to enter between the second electrode patterns, and a heating resistor extending in a linear shape is formed so as to cross both the first and second electrode patterns. Line type thermal print head. "A groove having a substantially V-shaped, U-shaped, or substantially semicircular cross section is formed in a portion of the heating resistor on the lower surface of the head substrate, and the groove is formed of the heating resistor. extending along a longitudinal direction and the
The deepest part of the groove is the width of the heating resistor.
To engraved on so that sit in a range of. ".

[0010]

[Operation] In this type of thermal printhead, the heat generated at each print dot on the heating resistor is
Through the head substrate, heat is transferred to a heat radiating plate applied to the lower surface of the head substrate.At this time, as described above, grooves are formed on the heating resistor portion of the lower surface of the head substrate, The groove extends along the heating resistor ,
The deepest part of the groove is the heating resistor.
By engraved on so that you located within the width of, because heat transfer to the heat sink from the printed dots in the heating resistor, the hindered by the presence of the groove strip, the heating resistor The heat can be accumulated in the portion of each print dot in.

In this case, for example, the groove is
As described in JP-A-63-173656, etc., when the cross-section is rectangular and the width of the groove is substantially equal to the width of the heating resistor, the heat storage effect of the groove is obtained. Is spread over the entire width of the groove, so that each print dot on the heating resistor is maintained at the same temperature over the entire print dot.

On the other hand, a groove formed in the lower surface of the head substrate so as to extend along the heating resistor on the lower surface of the head substrate is formed into a substantially V-shaped or U-shaped or substantially U-shaped cross section as described above. It is formed in a semicircular shape, and the
Deeper part is located within the width of the heating resistor
In such a case, the heat storage effect of the groove can be concentrated on the deepest portion of the groove, and therefore, among the printing dots of the heating resistor, the heat storage effect of the deepest portion of the groove can be obtained. The temperature can be kept higher than the rest.

As described above, the temperature at the deepest part of the groove among the printing dots in the heating resistor can be maintained at a higher temperature than the other parts, so that when printing with the printing dots, Since the printing in the portion where the temperature is the highest among the printing dots is darker than the printing in the other portions, the printing dot size in the direction perpendicular to the longitudinal direction of the linear heating resistor is substantially reduced. It is.

[0014]

As described above, according to the present invention, the print dot size in the direction perpendicular to the longitudinal direction of the linear heating resistor can be substantially reduced, so that the print density of the line type thermal print head can be reduced. This has the effect that the densification can be reliably achieved without lowering the yield rate when the heating resistor is formed by screen printing.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a first embodiment. In this figure, reference numeral 1 denotes a head substrate made of a heat-resistant insulator such as ceramic. A large number of the first electrode patterns 2 arranged and a large number of the second electrode patterns 3 also arranged in a comb-like shape are used. A thick-film heating resistor 4 formed so as to enter between the electrode patterns 2 and extending in a line shape.
But it is formed across both of the first electrode pattern 2 and the second electrode pattern 3.

A groove 5 having a substantially V-shaped cross section is formed in a portion corresponding to the heating resistor 4 on the lower surface of the head substrate 1, and the groove 5 is connected to the heating resistor 4.
Extending along the longitudinal direction of the
Deep portion 5a is within the range of the width of the heating resistor 4
It is to engraved on so that you located in.

In this configuration, each print dot 4 formed between each electrode pattern 2 and 3 on the heating resistor 4 is formed.
The heat generated at a is transmitted through the head substrate 1 to the heat radiating plate 6 applied to the lower surface of the head substrate 1. A groove 5 is formed on the heating resistor 4 at a position corresponding to the groove 5.
Extends along the heating resistor 4 and the groove 5
The deepest portion 5a of the heating resistor 4 is the width of the heating resistor 4.
By the engraved on so that sit in a range of heat transfer from each of the print dots 4a to the heat sink 6 in the heating resistor 4 is rather time hindered by the presence of the groove line 5, fever Heat can be accumulated in the portion of each print dot 4 a in the resistor 4.

In this case, the groove 4 is made to have a cross section V
Since the heat storage effect of the groove 5 is concentrated on the deepest portion 5a of the groove 5, the heat storage action of the groove 5 among the printing dots 4a of the heating resistor 4 is formed. Can be maintained at a higher temperature in the deepest portion 5a than in the other portions.

Therefore, in printing by the heat generation of each of the printing dots 4a, the printing of the portion of each printing dot 4a where the temperature is the highest becomes darker than the printing of the other portions. The print dot size in the direction perpendicular to the longitudinal direction of the resistor 4 is
It is substantially smaller.

The grooves 5 formed on the lower surface of the head substrate 1 are not limited to have a substantially V-shaped cross section as in the first embodiment, but may have a structure similar to that of the second embodiment shown in FIG. 4, a groove 5 'of a substantially semicircular shape or a third groove shown in FIG.
As in the embodiment, the groove may be formed in a substantially U-shaped groove 5 ″.

In a conventional line type thermal print head, a glaze layer for heat storage is formed on the upper surface of a head substrate, and a heating resistor is formed on the upper surface of the glaze layer. Since the thermal response characteristic of each print dot of the heating resistor is set by increasing or decreasing the thermal resistance, the thermal response characteristic cannot be changed after the thermal print head is manufactured.

On the other hand, in the case of the present invention, by appropriately selecting the width dimension S and the depth dimension H in each of the grooves 5, 5 ', 5 ", each print dot of the heating resistor 4 is selected. Since the heat storage property in 4a can be increased / decreased / changed, the thermal response characteristics of the thermal print head can be set so as to be suitable for any application after the thermal print head is manufactured.

[Brief description of the drawings]

FIG. 1 is an enlarged plan view showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

FIG. 4 is a sectional view showing a third embodiment of the present invention.

FIG. 5 is an enlarged plan view showing a conventional example.

6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 is a perspective view showing a state where a linear heating resistor is formed on a head substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Head board 2 1st electrode pattern 3 2nd electrode pattern 4 Heating resistor 4a Printing dot 5, 5 ', 5 "Groove 6 Heat sink

Claims (1)

(57) [Claims] 1. A comb-shaped first electrode pattern and a comb-shaped second electrode pattern are formed on the upper surface of an insulating head substrate. A line type thermal element which is formed so as to be inserted between the respective second electrode patterns, and wherein a heating resistor extending in a linear shape is formed so as to cross both the first electrode pattern and the second electrode pattern. In the print head, a groove having a substantially V-shaped, substantially U-shaped, or substantially semicircular cross section is formed in a portion of the heating resistor on the lower surface of the head substrate, and the groove is formed of the heating resistor. Extends along the longitudinal direction of the groove, and the deepest portion of the groove is
Structure of the line-type thermal printing head, characterized in that the engraved on so that to position within the width of the heat generating resistor.