JPH0684083B2 - Thermal recording head - Google Patents

Description

The present invention relates to a thermal recording head used for printers, facsimiles, etc., and particularly to thermal recording for enabling good printing on plain paper or rough paper. Regarding the head.

[Prior Art] Generally, in heat-sensitive recording, recording paper having high smoothness is used. This is because when recording on rough paper, the unevenness of the paper is large and the adhesion between the head and recording paper is poor.
This is because a part that does not develop color, that is, white spots are generated, and a rough recording state occurs, and the print or print image quality deteriorates. Further, even if a recording paper having a high smoothness is used, a 1-dot heating resistor has a high-temperature portion and a low-temperature portion within 1 dot depending on its shape, and in particular, the temperature is low at the end of the heating resistor. In addition, white streaks and white spots are generated between the recorded dots, which causes the print image quality to deteriorate. Especially when recording video images that require halftone recording,
The lower the density, the more easily the non-colored portion is generated and the image quality is deteriorated. Therefore, it is necessary to increase the color development area of one dot as much as possible.

It is effective to increase the contact pressure between the recording paper and the head in order to reduce the influence of the unevenness of the recording paper. One method is to provide a heating resistor on a convex partial glaze substrate. Has been converted.

This is 1m wide with a semi-cylindrical cross section on a ceramic substrate.
A maze layer (glass layer) of about m is provided and a heating resistor is formed on it, and the recording paper wound around the platen or drum and the heating resistor of the head (ink paper may intervene. ), The contact between the cylinders is a cylinder-to-cylinder contact, so that the contact pressure becomes large and the adhesion can be improved. However, the diameter of the platen or drum around which the recording paper is wrapped is often 25 mm or more, while the curvature of the glaze is about 5 mm, and it is slightly convex in the area of the heating resistor length (200 to 300 μm). However, it was not possible to obtain a contact pressure sufficient to print on a rough surface paper with large unevenness.

As a method for further increasing the contact pressure to the recording paper, for example, in Japanese Patent Laid-Open No. 58-59865, an upper glaze layer is formed in a mochi-like manner on a normal partial glaze layer, and a heating element is formed thereon. An example of providing is shown. According to this structure,
Since the curvature of the glaze layer can be made smaller, the heat-generating part strongly adheres to the recording paper, and even if the recording paper has large irregularities, the convex parts are crushed to some extent and it is easy to bite into the concave parts, so printing on rough paper is also possible. There is an advantage to be.

However, when the glaze layers are formed in a dough-like shape, the contact stress concentrates only on the center of the heating element, so that the center portion wears quickly, and the central portion of the heating element, which has the highest temperature, strongly adheres to the recording paper. Since the adhesion of the end portion of the heating element having a low temperature is not so improved, there is a large difference in density between the central portion and the end portion of the color-developed dot, and there is a drawback that the color-developed area on the rough surface paper cannot be made sufficiently large.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal head capable of printing even on rough surface paper with large irregularities, in consideration of the density difference and the color development area within the color-developing dot, which have been problems in the above-mentioned prior art.

That is, it is an object of the present invention to provide a thermal recording head capable of printing even on rough surface paper having large irregularities, the coloring dots having a sufficient size, and having a small density difference within the coloring dots.

[Means for solving problems]

In order to achieve the above object, the thermal recording head of the present invention,
The sectional shape of the heating element in the lengthwise direction of the partial glaze layer in the region where the heating resistor is formed is formed into a plurality of protrusions.
In addition, the projections and the recesses between the projections are formed at positions corresponding to the highest temperature portion of the heating resistor.

[Action]

By providing a plurality of protrusions on the partial glaze layer and forming the heating resistors on the protrusions, the contact pressure between the heating element and the recording paper becomes large at the protrusions. Therefore, even with roughened paper having large irregularities, the convex portions of the paper are crushed to some extent, the protrusions of the head are likely to be caught in the concave portions, and the adhesion is improved. Since there are a plurality of protrusions, they stick to each other at a plurality of places, and thus are less likely to be affected by the unevenness of the recording paper.

Further, since the protrusion is formed so that the highest temperature portion of the heating element is concave, the adhesion is improved in the heating portion where the heating temperature is relatively low, and the color density within one dot is significantly increased only in the central portion. There is no such thing. Therefore, the difference in color density within one dot can be reduced, and the color development area can be expanded due to the presence of a plurality of closely contacting portions.

〔Example〕

 An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a view showing a cross section of a heat generating portion of a thin film type thermal recording head according to the present invention.

In FIG. 1, reference numeral 1 is an insulating substrate made of alumina ceramic or the like, and 2 is a partial glaze layer formed thereon. The cross section of the glaze layer 2 in the lengthwise direction of the heating element is formed in the shape of two protrusions, and the central portion thereof is formed to be concave. The glaze layer having such a shape can be formed by a method such as ordinary printing and baking, followed by molding by etching, or a method of printing two rows of partial glazes and then melting and bonding after baking. 3 is a resistor layer, 4 and 4'are electrode layers, and the resistor layer 6 between 4 and 4'becomes a heating resistor. Reference numeral 5 is a protective layer for the heating resistor. Resistor layer 3, 3 ', electrode layer 4,
4 ', the protective layer 5 can be formed by ordinary vapor deposition, sputtering and photoetching.

Next, the contact state between the thermal recording head according to the present invention shown in FIG. 1 and a recording paper having large surface irregularities such as rough surface paper will be described with reference to FIGS. 3 and 4 in comparison with a conventional head.

FIGS. 3 (a) and 3 (b) are explanatory views schematically showing a contact state of a thermal recording head using a conventional overlapping mochi-like partial glaze with a rough surface paper, and FIGS. 4 (a) and 4 (b). ) Is an explanatory view schematically showing a contact state of a thermal recording head according to the present invention in which two projections are provided in a partial glaze with a rough surface paper, and the head and the recording paper are contacted with each other at a predetermined pressing pressure. It shows the state at the time of contact printing. In the case of transfer-type thermal recording using ink paper, the ink paper is interposed between the head and the recording paper, but it may be considered that the ink paper has the same shape as the glaze.

In FIGS. 3 and 4, reference numeral 7 is a schematic waveform showing the unevenness of the surface of the rough paper, 9 is the concave portion of the recording paper, and 10 is the convex portion of the recording paper. (A) is an example when the central portion of the head heating element is aligned with the concave portion 9 of the recording paper, (b)
Shows an example when it coincides with a convex portion. If the surface roughness of the currently used recording paper is about 1 μm and that of plain paper is about 5 μm, FIGS. 3 and 4 show the contact state on the recording paper having a considerably rough surface. Assuming that the convex portion of the recording paper is crushed while the head is being pressed, the shaded area in the figure is the contact area, and the recording paper corresponding to this area is colored.

From FIGS. 3 and 4, the heating element according to the present invention in which two projections are provided in the glaze shows that the contact area between the head and the recording paper per dot is larger than that in the conventional overlapping mochi type glaze. You can see that the range of Since the central portion of the heating element is concave, the adhesion at the central portion when the concave portion of the recording paper coincides with the central portion of the heating element as shown in FIG. 4 (a) is disadvantageous. Since there are two convex portions, the adhesiveness in areas other than the central portion is advantageous. Therefore, the width of the contact area is expanded, and the color development area can be increased even if the recording paper has irregularities.

FIG. 2 is a plan view of the head according to the present invention shown in FIG. 1 and a diagram showing a heat generation temperature distribution in the lengthwise direction of the heating element.
4'is an electrode and 6 (between A and B) is a heating element. The heat generation temperature shows the highest temperature in the central portion C between A and B, and the closer it is to the electrode ends A and B, the lower the heat because of the greater heat radiation. In the head according to the present invention, since the central portion C of the heating element is concave, it hardly contacts the recording paper, or the contact pressure is small even if it makes contact. Further, since the contact pressure at the D and E portions, which have a lower temperature than the central portion C of the heating element, is the largest, there is no possibility that only the central portion of the color-developing dots will develop a high density color as in the case of the overlapped mochi type head. Thus, it is possible to obtain a color-developed dot shape with a small density difference and a wide spread.

FIG. 5 shows the color-developing shape of one dot of the thermal recording head according to the present invention in comparison with that of the conventional head. FIG. 5 (a) is based on the conventional overlapping mochi type partial glaze, and FIG. This is due to the partial glaze provided with two protrusions of the invention. This figure shows an ideal color-developing shape on a smooth recording paper.When recording on rough surface paper, a non-color-developing area occurs partially, but for the reasons described above, the density difference is smaller than that of the conventional head. However, there is no change in that a color-developed dot shape with a wide spread can be obtained.

Although the heating element plane shape of the embodiment shown in FIG. 2 is a simple rectangle, the heating temperature distribution in the width direction of the heating element is provided by providing slits 12 of an insulator as shown in FIG. 6, for example. Can be close to flat. If the glaze cross-sectional shape of the thermal recording head having the planar shape of the heating element shown in FIG. 6 is formed in the shape of two protrusions as shown in FIG. 1, the color-developed shape of one dot becomes the shape shown in FIG. Further, it is possible to obtain better print image quality.

FIG. 8 is a plan view and a sectional view in the longitudinal direction of a partial glaze heating element showing another embodiment of the thermal recording head according to the present invention.

In FIG. 8, 4,4 'are electrodes, and a portion between a and b corresponds to a 1-dot heating element. Reference numeral 4 ″ denotes an intermediate electrode provided in the center of the heating element, whereby a one-dot heating element is divided into two heating elements 6, 6 ′. Since the intermediate electrode 4 ″ does not generate heat, The hottest parts are points d and e.
In the embodiment shown in FIG. 8, the glaze cross-sectional shape 2'in the area where the heating element is formed is convex at the intermediate electrode 4 ", and the highest temperature portion d, e.
It is formed in the shape of three protrusions that are concave.
Since the relatively low temperature protrusion strongly abuts the recording paper, the same effect as described above can be obtained in the recording on the rough surface paper.

The planar shape of the heating element is not limited to the above-described embodiment, and various shapes other than the combination of the above-described embodiments are conceivable. In any case, it is the gist of the present invention that the partial glaze cross-sectional shape of the portion of the heating element where the heat generation temperature is the highest is concave and the convex projection is provided in the other portion.

FIG. 9 is a plan view and a sectional view in the longitudinal direction of a partial glaze heating element showing another embodiment of the thermal recording head according to the present invention.

In FIG. 9, reference numerals 4 and 4'represent electrodes, and 6 a heating element. FIG. 9 shows a cross section 2 ″ of the glaze formed into four protrusions having a concave central portion of the heating element. The number of protrusions, the height of the protrusions, etc. are the surface roughness of the recording paper and the glaze. It may be designed optimally in consideration of the moldability and the like.

〔The invention's effect〕

According to the present invention, since the sectional shape of the partial glaze layer in the region where the heating resistor is formed in the lengthwise direction of the heating element is formed as a plurality of protrusions such that the highest temperature portion of the heating element is concave, a rough surface with large unevenness is formed. It can be closely attached to a surface paper, can print on a rough surface paper, and the colored dots have a sufficient size to obtain good print quality with a small density difference within the colored dots. it can.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG.
3 is a plan view of the embodiment shown in FIG.
The figure is an explanatory view showing the contact state between the conventional head and the recording paper,
FIG. 4 is an explanatory view showing a contact state between the head and the recording paper in the embodiment of FIG. 1, and FIG. 5 is an explanatory view showing a comparison of a 1-dot color development shape of a conventional head and a head according to the present invention. FIG. 6 is a plan view of another head to which the present invention is applied, FIG. 7 is an explanatory view showing a color-developing shape by the head, and FIGS. 8 and 9 are plan views showing another embodiment of the present invention. FIG. 1 ... Insulating substrate 2,2 ', 2 "... Glaze layer 3 ... Resistor layer 4,4', 4" ... Electrode (layer) 5 ... Protective layer 6,6 '... Heating element

Claims (1)

[Claims] 1. On a partial glaze layer formed on a substrate, 1
In a thermal recording head having a heating resistor for each dot, the cross-sectional shape of the glaze layer region in the heating element length direction corresponding to the heating resistor for one dot corresponds to the highest temperature heating portion of the heating resistor. The thermal recording head is characterized in that the heating element lengthwise surface shape of the glaze layer region is formed to include a plurality of convex protrusions by forming the concave portions as the concave portions.