JP3038944B2 - Thick film type thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an individual facing type thick film type thermal head, and more particularly to a thick film type thermal head having a heating resistor structure for improving the printing quality of a recording device such as a sublimation printer. Related to a thermal head.

[0002]

2. Description of the Related Art As a recording head used in a recording device of a recording apparatus such as a thermal printer or a facsimile, a recording head called a so-called thick-film type thermal head is widely used because of its easy production. As one type of thermal recording apparatus, a sublimation recording apparatus that forms an image or a character on a recording medium by heating and sublimating the ink of an ink donor film is known. FIG. 5 is an explanatory view of a main part of a sublimation type recording apparatus using a thick film type thermal head as a print head, wherein 1 is a substrate made of an insulating material such as ceramics, 2 is a common electrode,
Reference numeral 3 denotes an individual electrode, 4 denotes a heating resistor, and 6 denotes an overglaze layer serving as a protective layer. These constituent layers constitute a thick-film type thermal head 10. Reference numeral 7 denotes a platen, 8 denotes a recording medium, and 80 denotes an ink donor film. In the drawing, the recording medium 8 is sandwiched and pressed between the thick film type thermal head 10 and the platen 7 in the direction of the arrow P during recording, and the dye sublimated by the heating of the ink donor film 80 is transferred to perform recording. . The thermal head is classified according to the electrode arrangement structure, and an individually opposed type thermal head in which a common electrode and an individual electrode are arranged facing each other in the sub-scanning direction, and a common electrode and the individual electrode are arranged in a comb shape in the main scanning direction. It is roughly divided into the arranged alternate read type thermal head.

FIG. 6 is a plan view of an essential part for explaining the structure of an individual opposed type thick film type thermal head according to the prior art.
010 is a thick film type thermal head, 01 is a ceramic substrate, 02 is a common electrode, 03 is an individual electrode, 04 is a heating resistor, and 06 is an overglaze layer which is a protective layer. This type of thick-film type thermal head is manufactured by a lift-off method in which a material for forming an electrode layer or a material for forming a resistance layer serving as a heating element is printed as a paste, applied and baked to obtain a desired constituent layer. 7A and 7B are cross-sectional views of the thick film type thermal head shown in FIG. 6, wherein FIG. 7A is a cross-sectional view in the sub-scanning direction along the line AA in FIG. 6, and FIG. 2 shows a cross section along the main scanning direction. As shown in FIGS. 3A and 3B, the heating resistor 04 is formed by forming a common electrode 02 and an individual electrode 03 and bridging over these two electrodes. Accordingly, in the individual facing type thick film type thermal head manufactured by this type of lift-off method, since the cross-sectional shape of the heating resistor 04 in the sub-scanning direction is convex in the recording medium direction, the overglaze layer 06 is also convex. Has made. Japanese Patent Application Laid-Open Nos. 1-123756 and 64-44762 can disclose the conventional thick film type thermal head. The thick-film type thermal head disclosed in each of the above publications has a uniform heating distribution of the heating resistor by making the shape of the heating resistor a rectangular cross section in each of the main scanning direction and the sub-scanning direction. The shape reproducibility, that is, dot reproducibility is improved. However, no consideration is given to the structure of a thick-film type thermal head suitable for a sublimation recording apparatus.

[0004]

In this conventional main thick-film type thermal head, the common electrode 02 and the individual electrodes 0 are used.
3 and the width d of the heating resistor 04 in the sub-scanning direction do not have a large difference. Therefore, when the heating resistor 04 is energized via the common electrode 02 and the individual electrode 03, the heating resistor 04 has its edge. Heated over its entire length. for that reason,
The entire protruding portion up to the edge of the overglaze layer 06 is also heated. When printing such as printing is performed on a sublimation type recording medium by mounting the thermal head on a sublimation type recording apparatus, the entire convex portion of the overglaze layer on the heating resistor is heated together with the heat generated by the heating resistor. The surface of the ink is heated, and the dye of the ink is transferred to a central portion where the temperature of the ink donor film reaches a temperature at which the dye is sublimated, whereby recording is performed.

FIG. 8 is a schematic view for explaining a recording state using an individual facing type thick film type thermal head.
For example, in a thermal head of 10 dots / mm, the main scanning width of the heating resistor is 70 μm, and the width between the electrodes is 140 μm.
On the other hand, the heating resistor sub-scanning width is conventionally set to about 170 μm. In this case, the indentation of the heating resistor projection (projection of the overglaze layer) itself becomes a recess 11 in which the shape of the edge of the projection is transferred, and as a result, the periphery of the indentation becomes convex. In the case of the above-mentioned heating resistor size of 10 dots / mm, since the paper feed is 0.1 mm / line, 70
An overlapping margin of the concave 11 of μm occurs, and the irregularity of the surface of the recording medium becomes severe at the overlapping margin. The indentation on the recording medium due to the convex shape of the edge of the heating resistor (overglaze layer) is due to the fact that heat is transmitted to the edge of the heating resistor in the sub-scanning direction end, and hence to the edge of the overglaze layer, and sublimation recording This is because all the areas of the medium surface that are hit by the edge are easily deformed. That is, since the surface of the recording medium 8 for sublimation recording tends to be easily deformed by heat, when printing is performed by the above-described thermal head, as shown in FIG. The convex shape due to the edge of the heating resistor 4 of the thick film type thermal head, that is, the edge of the overglaze layer 6 having substantially the same size as the edge of the heating resistor 4 is directly transferred as the concave portion 11. Then, the dye 9 of the ink, which has reached the sublimation temperature and sublimated, moves to the center of the concave portion 11. The recording medium portion to which the dye 9 has been transferred swells and becomes slightly convex as shown in the figure. Then, in the next recording operation, the concave portion 11 is further overlapped with the concave portion 11 formed by the previous recording as shown in (b), and the concave portion 11 and the swollen portion are successively formed as shown in (c). You. For this reason, the surface of the recording medium 8 has severe irregularities, and the dot reproducibility is impaired. As a result, there is a problem that the image quality is deteriorated.

An object of the present invention is to provide an individual facing type thick film type thermal head by a lift-off method, in which the edge of the resistor in the sub-scanning direction (that is, the edge of the overglaze layer in the sub-scanning direction) generates heat of the heating resistor. An object of the present invention is to improve the image quality by eliminating the unevenness on the surface of the recording medium recorded by the sublimation recording apparatus without deteriorating the dot reproducibility by not being affected.

[0007]

In order to achieve the above object, the present invention provides a common electrode (2) and a plurality of common electrodes (2) arranged independently of each other and arranged in the main scanning direction. On the upper surface of the plate-like substrate (1) on which the individual electrodes (3) are formed, a plurality of bridges are formed in each of the common electrode (2) and the individual electrodes (3) in the sub-scanning direction and formed by a lift-off method. Of the heating resistor (4) and the common electrode (2),
In a thick-film type thermal head having an individual electrode (3) and a protective layer (6) covering a plurality of heating resistors (4), a facing distance between the common electrode (2) and the individual electrode (3). Is D, and when the sub-scanning width of each of the heating resistors (4) is d, 2D ≦ d.

[0008]

By setting the width d of the heating resistor (4) in the sub-scanning direction at least twice the facing distance D between the common electrode (2) and the individual electrode (3) which is bridged by the heating resistor, heat is generated. Even if the center of the resistor reaches the sublimation temperature at which the dye of the ink donor film forming the recording dots sublimates, the edge of the heating resistor (4), that is, the edge of the overglaze layer (6) heats and deforms the recording medium. Never reach temperature. Therefore, the image does not deteriorate as described with reference to FIG.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view of an essential part for explaining an embodiment of a thick film type thermal head according to the present invention, wherein 1 is a ceramic substrate, 2 is a common electrode, 3 is an individual electrode, and 4 is a heat generated by a lift-off method. The resistor 6 is an overglaze layer. 2 is a cross-sectional view of the thick-film type thermal head shown in FIG. 1, (a) is a cross-sectional view in the sub-scanning direction along the line AA in FIG. 1, and (b) is a BB in FIG. It is sectional drawing along the line. In the embodiment of the present invention, as a result of performing printing with the heating resistor sub-scanning width set to 210 μm, 280 μm, and 350 μm, the width of the heating resistor in the sub-scanning direction and the distance between the common electrode and the individual electrode are selected at a specific ratio. It was done.

FIG. 3 shows (a) a surface view and (b) a cross-sectional view of a recording medium recorded by the thermal head of this embodiment. In the thermal head having a width between electrodes of 140 μm, the heating resistor in the sub-scanning direction is used. In the case where the width is 280 μm or more, that is, twice or more the width between the electrodes, as shown in the figure, the edge (overglaze layer 6
No indentation (concave) due to the edge of the sublimation dye is observed, and the sublimation dye transfer section 9 is slightly swollen. Therefore, the surface state of the recording medium becomes extremely smooth as compared with that of the conventional thermal head, and good image quality can be provided.

FIG. 4 shows a recording medium in which recording is performed by changing the ratio between the width of the common electrode and the individual electrode in the sub-scanning direction (electrode interval) and the width of the heating resistor in the sub-scanning direction (resistor width). It is explanatory drawing of the heat distribution on the surface. In the figure, when the above-mentioned electrode interval is D and the width of the heating resistor is d, (a) is d.
<2D, (b) d = 1.5D, (c) d = 2D,
(D) shows the heat generation temperature distribution on the surface of the recording medium of the thermal head where d> 2D. In the drawing, T is the heat generation temperature, and To is the critical temperature at which the recording medium undergoes thermal deformation.
That is, in the thermal head in which d <2D in (a), the temperature of the edge of the heating resistor (the edge of the overglaze layer) in the sub-scanning direction greatly exceeds the critical temperature To,
The surface of the recording medium is deformed to generate an indentation (concave), and the surface of the recording medium becomes extremely uneven. In the thermal head with d = 1.5D in (b), although the temperature is lower than that of the thermal head in (a), the temperature of the edge of the heating resistor (the edge of the overglaze layer) in the sub-scanning direction. Still greatly exceeds the critical temperature To, the surface of the recording medium is deformed, and an indentation (concave) is generated.

However, in the thermal head in which (c) d = 2D, the temperature of the edge of the heating resistor (the edge of the overglaze layer) in the sub-scanning direction is substantially equal to the critical temperature To, and the ambient temperature Depending on conditions such as humidity, humidity, and operating time of the recording apparatus, slight indentation may occur, but the recording medium maintains a substantially smooth surface state. And
(D) In the thermal head where d> 2D, the edge of the heating resistor in the sub-scanning direction (the edge of the overglaze layer)
Is below the critical temperature To, so that no indentation occurs on the surface of the recording medium. That is, when the resistor sub-scanning width d is twice or more the interelectrode width D, the edge at the sub-scanning direction end is heated to a temperature at which the surface of the sublimation recording medium is deformed. I do not reach. In the above embodiment, the present invention is applied to an individually opposed type thick film type thermal head. However, the present invention is not limited to this, and the present invention is applied to an alternate lead type thick film type thermal head. It is also possible to replace the length of the common electrode and the individual electrode in the sub-scanning direction with the length D of the electrode in the above embodiment. Further, by applying the present invention to a thick film type thermal head used in an ink fusion transfer type thermal recording device using an ink ribbon and plain paper, recording dots smaller in size in the sub-scanning direction of the heating resistor can be formed. A recording device can also be provided.

[0013]

As described above, according to the present invention,
The heating resistor sub-scanning width d in the sub-scanning direction is set to the interelectrode width D.
Is twice or more, the edge of the heating resistor in the sub-scanning direction, that is, the edge of the overglaze layer does not reach a temperature at which the recording medium is deformed. The surface state of the recording medium can be kept substantially smooth, and recording with good image quality can be performed.

[Brief description of the drawings]

FIG. 1 is a plan view of an essential part for explaining an embodiment of a thick film type thermal head according to the present invention.

FIG. 2 is a cross-sectional view of FIG. 1 illustrating an embodiment of a thick film type thermal head according to the present invention.

3A and 3B are a front view and a cross-sectional view of a recording medium recorded by a thermal head according to an embodiment of the present invention.

FIG. 4 shows a case where recording is performed by changing the ratio of the width of the common electrode and the individual electrode of the thick film type thermal head in the sub-scanning direction (electrode interval) to the width of the resistor in the sub-scanning direction (resistance body width). FIG. 3 is an explanatory diagram of a heat distribution on a surface of a recording medium.

FIG. 5 is an explanatory view of a main part of a sublimation type recording apparatus using a thick film type thermal head as a print head.

FIG. 6 is a plan view of a principal part for explaining the structure of an individual facing type thick film type thermal head according to the related art.

7A and 7B are a cross-sectional view in the sub-scanning direction along line AA and a cross-section in the main scanning direction along line BB in FIG. 6 for explaining the structure of the conventional individually opposed thick film type thermal head.

FIG. 8 is a schematic diagram microscopically showing a recording state using an individual facing type thick film type thermal head according to the related art.

[Explanation of symbols]

 Reference Signs List 1 ceramic substrate 2 common electrode 3 individual electrode 4 heating resistor 6 overglaze (protective layer)

Continuation of the front page (56) References JP-A-60-58876 (JP, A) JP-A-2-276652 (JP, A) JP-A 2-144443 (JP, U) JP-A 1-110928 (JP) , U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B41J 2/345

Claims (1)

(57) [Claims] 1. A common electrode and a plurality of individual electrodes which are opposed to the common electrode independently from each other and are arranged in a main scanning direction are formed on an upper surface of a plate-shaped substrate. A thick film type thermal head in which a plurality of heating resistors bridged in the sub-scanning direction and formed by a lift-off method, and a protective layer covering the common electrode, the individual electrodes and the plurality of heating resistors are formed. 2D ≦ d, where D is the distance between the common electrode and the individual electrode facing each other, and d is the sub-scanning width of each heating resistor.