JP2530743Y2 - Thick film type thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention is widely used in a thermosensitive color recording device or a thermal transfer recording device, and is a thick film type in which a heating resistor is formed through a printing and firing process. The present invention relates to a thermal head, and more particularly to a thick-film type thermal head capable of obtaining high image quality in halftone printing with little variation in the center of a print dot.

(Prior Art) As a thick film type thermal head used in a recording section of a thermosensitive color recording apparatus or a thermal transfer recording apparatus, for example, the one shown in FIG. 6 is conventionally known.

This is because a plurality of overhang portions 12a overhang in the sub-scanning direction from the common electrode 12 continuous in the main scanning direction on the insulating substrate 11,
On the other hand, a plurality of individual electrodes 13 project from a position facing the common electrode in the sub-scanning direction, and a plurality of overhangs 12a and a plurality of individual electrodes 13 alternately protrude between the individual electrodes or between the overhangs without contact. Are sequentially and alternately opposed on both sides in the main scanning direction.

A strip-shaped heating resistor in the main scanning direction is provided on an opposing portion near the tip of the plurality of overhangs 12a and the plurality of individual electrodes 13.
14 are formed by printing and firing. This strip-shaped heating resistor 14 has a width slightly larger than the feed width in the sub-scanning direction, and the opposing length between the protruding portion 12a of the common electrode and the individual electrode 13 is larger than the width of the heating resistor 14. ing.

In such a thick film type thermal head, the common electrode
When a voltage is selectively applied between the individual electrode 13 and the individual electrode 13, current flows between the protruding portion of the opposing common electrode on both sides of the selected individual electrode, and the heating resistor on the opposing portion generates heat. To print.

Further, in the thick film type thermal head disclosed in Japanese Patent Application Laid-Open No. 63-149165, a heating resistor formed on a portion where a plurality of projecting portions of a common electrode and a plurality of individual electrodes face each other has a structure in a sub-scanning direction. It has a width that is sufficiently larger than the feed width, and has a width such that the upper surface becomes flat without being mountain-shaped even when formed by printing and baking.

On the other hand, the facing length of the plurality of projecting portions of the common electrode and the plurality of individual electrodes is smaller than the width of the strip-shaped heating resistor in the sub-scanning direction, and the size of the print dot is defined by the facing length.

In such a thick-film type thermal head, since the thickness of the heating resistor is uniform, the shape and size of the printing dot can be set with high accuracy by the portion where the electrodes face each other.

(Problems to be Solved by the Invention) However, in the conventional thick film type thermal head shown in FIG. 6, the common electrode 12 and the individual electrode 13 are connected to each other over the entire width of the strip-shaped heating resistor. Sometimes, a heat spot is generated in a portion where a large amount of current flows due to uneven film thickness. Therefore, if a dot smaller than the feed width in the sub-scanning direction is printed, as shown in FIG. 7, the variation in position within the width of the heating resistor becomes large, and the dot shape becomes uneven.
The width direction of the heating resistor at this time, for example, as shown in FIG.
The temperature distribution on the ab line is as shown in FIG. 8, and when the location is changed in the main scanning direction, the position of the heat spot varies within the range shown in the figure. When the density gradation is represented by the density modulation method, a problem arises in that good image quality cannot be obtained due to the above-described variation in dot position.

On the other hand, in the conventional example described in JP-A-63-149165, it is necessary to increase the width of the heating resistor in the sub-scanning direction, and the thermal head becomes large.

Also, the dot size can be set by adjusting the opposing portions of the electrodes at the time of design, but this does not improve the image quality in halftone printing by the density modulation method.

The present invention has been made in view of the above-described problem, and has a thin film type thermal head capable of obtaining good halftone printing when the density gradation is expressed by a density modulation method with little variation in print dot position. The purpose is to gain.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a plurality of overhanging portions extending from a common electrode in a sub-scanning direction on an insulating substrate, and individual electrodes overhanging from a position opposed thereto. And
The protruding portions alternately protrude in a non-contact manner between a plurality of individual electrodes or a plurality of protruding portions, and both end portions are alternately arranged in the main scanning direction to face each other, and the main scanning direction In the thick film type thermal head having a band-shaped heating resistor having a width slightly larger than the feed width in the sub-scanning direction, the plurality of individual electrodes and the plurality of projecting portions of the common electrode are alternately arranged. The facing length of the opposed portion in the sub-scanning direction is equal to or less than the feed width in the sub-scanning direction and about 1/2 or more of the feed width.

(Operation) In the thick-film type thermal head having such a configuration, the facing length between the plurality of overhanging portions of the common electrode and the plurality of individual electrodes is as follows.
The current is less than the feed width in the sub-scanning direction, and when printing with low density or halftone printing, the current flows through the shortest distance in the heating resistor when power is applied by adjusting the amount of power applied between them. The portion within the length range generates heat, and only this portion is printed. If the voltage is increased or the energization time is increased when printing a high density portion, the heat generation range is expanded from the opposite long portion to both sides in the sub-scanning direction, and the range of the print dot is also widened, so that density gradation expression can be performed.

When printing dots smaller than the feed width in the sub-scanning direction as described above, the area through which current flows even though the thickness of the heating resistor is slightly uneven because the facing length is smaller than the feed width. Limited, and the variation of the printing dots is reduced.

As the opposing length between the vicinity of the tip of the overhanging portion of the common electrode and the vicinity of the tip of the individual electrode is shortened, the region where the current flows is reduced and the dot position variation is reduced. However, when the feed width in the sub-scanning direction is less than about 1/2, the energization area becomes narrower, so that printing of large dots cannot be performed and the connection between dots in the sub-scanning direction deteriorates.

Therefore, if the facing length is in a range from about 1/2 of the feed width in the sub-scanning direction to the feed width or less, high-quality halftone images can be obtained, and printing with good continuity in the sub-scanning direction can be obtained.

(Example) Hereinafter, an example of the present invention is described using a drawing.

FIG. 1 is an explanatory view showing the configuration of a thick film type thermal head according to an embodiment of the present invention.

A common electrode 2 made of Au and a plurality of individual electrodes 3 are formed on a ceramic substrate 1 whose entire surface is glazed. The common electrode 2 has a plurality of overhangs 2a overhanging in the sub-scanning direction, and is continuous at the base thereof in the main scanning direction.

On the other hand, the plurality of individual electrodes 3 are connected to the common electrode 2 in the sub-scanning direction.
Projecting from a position opposed to the main electrode, one each protrudes between the plurality of projecting portions 2a of the common electrode 2, and the vicinity of the tip of the projecting portion 2a and the individual electrode 3 oppose each other in the main scanning direction on both sides. They are arranged alternately over the entire length.

The center spacing between the plurality of overhangs 2a of the common electrode and the plurality of individual electrodes 3 is the same as the feed width in the sub-scanning direction.
The facing length (indicated by L in FIG. 1) in the sub-scanning direction, which is opposed to the vicinity of the tip of the overhang portion 2a near the tip of the individual electrode 3, is set to 70 μm. The value is set to a value slightly larger than 1/2 of the feed width of 125 μm.

The heating resistor 4 is formed in a belt-like shape having a width of 140 μm in the sub-scanning direction over the entire length in the main scanning direction on a portion where the projecting portion 2a of the common electrode 2 and the individual electrode 3 are opposed to each other.

A glass wear-resistant layer (not shown) is formed on the heating resistor 4 so as to cover the entire surface.

In such a thick-film type thermal head, when a voltage is selectively applied between the common electrode 2 and the individual electrode 3, a current flows between the common electrode 2 and the overhanging portion of the common electrode opposed on both sides of the selected individual electrode. The thermal recording is performed on a sheet of paper in which the heating resistors on the opposing portions generate heat and are pressed onto the wear-resistant layer.

FIG. 2 is an enlarged view of dots when halftone printing is performed by the above-mentioned thick film type thermal head.
Compared with the printing by the conventional thick film type thermal head shown in FIG. 7, the variation in the dot position is reduced and the shape is made uniform, so that good halftone printing is obtained.

In the above embodiment, the opposing length L between the common electrode extension 2a and the individual electrode 3 is different from 30, 50, 70, 90, 110, and 130 μm, and halftone printing is performed by each. As shown in FIG.

In FIG. 3, the horizontal axis represents the common electrode overhang 2a and the individual electrode 3
And the vertical axis represents the variation of the dot center position, and these relationships are shown. As shown in the figure, the opposing length L is set to be equal to or less than the feed width in the sub-scanning direction, and as the size is reduced, the variation in the dot center tends to decrease. Become.

FIG. 4 shows the temperature distribution in the sub-scanning direction on the surface of the heating resistor when performing the printing shown in FIG. 2, for example, the temperature distribution at the position indicated by the cd line in FIG. In the vicinity of the center between the protruding portion of the common electrode and the opposing individual electrode, the temperature distribution shown in FIG. A heat spot is generated within the range of the length L.

FIG. 5 shows another embodiment of the present invention, which similarly has a common electrode, an individual electrode, a heating resistor, and a wear-resistant layer. The arrangement interval in the main scanning direction) and the center interval between the individual electrodes (the arrangement interval in the main scanning direction) are 100 μm.
This shows the relationship between the opposing length L and the variation in the dot center position when the feed width in the sub-scanning direction is also 100 μm. The width of the heating resistor in the sub-scanning direction is 140 μm.

The results shown in FIG. 5 show the same tendency as the results shown in FIG. 3, and the variation of the dot position becomes smaller as the facing length L becomes shorter, and the variation of the dot position becomes about 2 μm in the range of 50 μm or less. And good halftone printing can be obtained.

For the halftone printing shown in the above embodiment,
The opposing length L between the common electrode extension and the individual electrode is set to be equal to or less than the feed width in the sub-scanning direction. As the opposing length L decreases, the dot position variation decreases and the image quality tends to improve. If the width is not more than about 1/2, the connection between dots in the sub-scanning direction is deteriorated. Therefore, the facing length L between the common electrode extension and the individual electrode is set to about 1/2 of the feed width in the sub-scanning direction. As a result, a good halftone display can be obtained, and a thick film type thermal head having good connection between dots in the sub-scanning direction can be obtained.

(Effects of the Invention) As described above, in the thick-film thermal head of the invention, the facing length between the overhanging portion of the common electrode and the individual electrode is:
Since the width is smaller than the feed width in the sub-scanning direction, the area where current flows when a voltage is applied to the heating resistor from the common electrode and the individual electrode is limited, and the thickness of the heating resistor by printing is somewhat inconsistent. Even if there is evenness, there is little variation in the dot center position, and high-quality halftone printing can be obtained.

In addition, since the opposing length of the protruding portion of the common electrode and the individual electrode is larger than about 1/2 of the feed width in the sub-scanning direction, continuity between dots in the sub-scanning direction is improved, and the density modulation method is used. A thick film type thermal head suitable for the expression of density gradation by the method can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the configuration of a thick film type thermal head according to an embodiment of the present invention. FIG. 2 is an enlarged view of a dot for halftone printing by the thick film type thermal head of the above embodiment. FIG. 4 is a diagram showing the relationship between the variation of the center of the dot when the facing length of the common electrode and the individual electrode is changed in the above embodiment. FIG. 4 is a diagram showing the sub-scanning direction of the heating resistor in the above embodiment. FIG. 5 is a diagram showing the temperature distribution in the present embodiment, and FIG. 5 is a diagram showing the relationship between the variation of the dot center when the facing length of the common electrode and the individual electrode is changed in another embodiment of the present invention. FIG. 1 is an explanatory view showing the configuration of a conventional thick film type thermal head. FIG. 7 is an enlarged view of a dot for halftone printing by the conventional thick film type thermal head. FIG. 8 is a conventional thick film type thermal head. Shows the temperature distribution in the sub-scanning direction of the heating resistor in FIG. DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 2 ... Common electrode 3 ... Individual electrode 4 ... Heating resistor

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-149165 (JP, A) JP-A-1-214453 (JP, A) JP-A 1-267058 (JP, A) JP-A-1- 133756 (JP, A) JP-A 1-238955 (JP, A) JP-A 1-214456 (JP, A)

Claims (1)

(57) [Scope of request for utility model registration] A plurality of overhanging portions extending from a common electrode and a plurality of individual electrodes overhanging from a position opposite to the plurality of overhanging portions in the sub-scanning direction on the insulating substrate; Protrude in a non-contact manner between the two electrodes, and both ends are alternately arranged in the main scanning direction to face each other, and on a portion where the tips of the common electrode and the individual electrodes face each other,
In a thick film type thermal head in which a heating resistor is formed in a band shape having a width slightly larger than a feed width in a sub-scanning direction in the main scanning direction, the plurality of individual electrodes and a plurality of overhangs of a common electrode are alternately arranged. Characterized in that the facing length in the sub-scanning direction of the portion arranged and facing in the sub-scanning direction is not more than the feed width in the sub-scanning direction and is not less than about 1/2 of the feed width.