JPS60240466A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain a thermal head enabled in medium contrast density recording, by forming a concavity to the anti-wear layer directly applied to a heat generating resistor. CONSTITUTION:A concavity 11 is formed to the upper surface of the anti-wear layer 5 directly formed to the heat generating resistor 4 of a printing head. When a pulse with constant voltage is applied between a common electrode 2 and a lead wire 3, the heat generating resistor 4 generates heat and the heat transmitted to the anti-wear layer 5 reaches an ink layer 8 to melt ink while the molten ink is adhered to paper 6 to be transferred to obtain a printing dot. At this time, the ink layer 8 corresponding to the concavity 11 is not melted and an unprinted region 12 is generated to generate a doughnut shaped part. When a pulse width is increased, the unprinted region 12 is reduced and printing density becomes high. Medium contrast density recording is enabled until the unprinted region 12 is lost and adjacent printing dots are fused to record max. printing density.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a thermal head used in facsimiles, thermal printers, and the like.

[Background of the invention]

With the advancement of information society, printers and 7A.

Information recording devices such as tsumiri have also progressed.

There are various recording methods such as a wire dot method, an inkjet method, and a thermal transfer method, but the thermal transfer method is preferable because it generates less noise when the device is driven and has a simple device.

A current problem with thermal transfer recording devices is multi-gradation printing, and the means to achieve this are (1) changing the density itself of printing dots, which are the smallest unit of printing (hereinafter referred to as
(2) The area where one pixel is printed and the printing method, as typified by the dither method and halftone method that use a dot matrix of '71 x n (m and n are integers of 2 or more). The density of the pixel is changed according to the ratio of the areas of the two areas (hereinafter referred to as the area method).

(3) The above three methods of changing the degree and area of the printed dots (hereinafter referred to as the density-area method) have been devised.

FIG. 1 is a cross-sectional view (α), (b) a front view, and (C) a printed dot pattern diagram of a thin film thermal head according to the prior art.

A heating resistor 4, a common electrode 2, and a lead plate 3 are formed on an insulating substrate 1, and a wear-resistant layer 5 is further formed thereon.
These are laminated by vapor deposition and sputtering, respectively, and patterned by photoetching. Heat generating resistance layer 4
The part that generates heat for printing is the area sandwiched between the common electrode 2 and the lead [5]. And a printing driver corresponding to the heat generating area)? 0 is obtained.

FIG. 2 is an explanatory diagram of a printing means when performing thermal transfer recording with the thermal head of FIG. 1. An ink paper 7 coated with an ink layer 8 on the front side of a base paper 9 and a transfer paper 6 are placed together so that the ink layer 8 is in contact with the transfer paper 6, and a heating resistor 4 is placed on the back side of the base paper. During printing, the heat generating resistor 4 generates heat, this heat passes through the base paper 9 and is transmitted to the ink layer 8, the ink layer 8 melts, and this ink adheres to the transfer paper B, thereby forming the printed dot 1o. Form.

To make the heating resistor 4 generate heat, the common electrode 2' and the electrode 3
A pulse pressure is applied between the two, but when the applied pulse width is changed while the voltage is constant, the temperature of the heating resistor 4 changes corresponding to the pulse width, and the amount of melting of the ink layer 8 changes. ,
The density of the printing driver) 10 changes.

However, in conventional thermal transfer recording, the adhesion of ink to the transfer paper 6 is extremely severe, and printing cannot be performed stably on the transfer paper 6 unless the printing driver) 1 (It) becomes at least as large as the heating resistor 4. Therefore, the printing harshness DI of the printing driver (IDN) at this time is incorrect.

In addition, if the applied pulse width is increased to obtain a larger print dot 1ON, the print dot 1ON+1 will be closer to the adjacent print dot 1ON+1, so the print hardness D2 of the print driver ION is a small difference compared to Dl. Therefore, in thermal transfer recording, it is possible to record the intermediate l/l ratio of printed dots in only 2 to 3 gradations, and the number of gradations is insufficient for multi-level printing.

In order to increase the number of recording gradations, there is a way to add a dither method based on the area method and use the density-area method. Because it is one pixel, the pixel becomes larger and the recording resolution decreases, or the size of one pixel is reduced.

6 dots/
Using a thermal head of 11 fc@, the upper limit is about 2 x 3 dot matrix9.6 built-in halftones can be obtained only by the dither method, but in addition to this, 2 to 5 tones can be obtained by the concentration method. When multiplied together, the discernible half-tone number is 12 to 1.
Considering that 5 gradations are required, and nearly 30 gradations are required for practical use, the number of ##l is still insufficient. In particular, there is a lack of gradations in the middle tones of low intensity.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal head capable of recording halftones of 11 by varying the size of printed dots in thermal transfer recording.

[Summary of the invention]

The thermal head of the present invention includes a heating resistor provided on an insulating substrate,
On top of that, a common wire and a lead wire are projected facing each other, a wear-resistant layer is formed on these, and a heating resistor ib is formed.
: A depression is formed in the upper j118-resistant layer. With this, when the ink paper comes into contact with the anti-wear layer during printing, the heat generated by the heat resistor passes through the base paper and melts the ink in the ink layer; Therefore, there is no heat conduction to the ink paper, and the ink layer facing the ink does not melt, resulting in a stable, hollow, donut-shaped printed dot.
Obtaining printing freeze [Dt] As the power input to the heating resistor increases, the amount of melted ink increases, and the printed dots become larger and closer to the adjacent printed dots. On the other hand, with hollow holes, the holes are smaller and the printed dots are uniformly attached to the transfer paper.
The printing surface becomes f02. The difference between printing surface [Dl and D2 is considerably larger than the # slope range exhibited by stable printing dots obtained with a conventional thermal head, and the halftone density recording range is expanded.

[Embodiments of the invention]

The present invention will be explained in detail below.

The third south is a front view ((α) cross-sectional view) of one embodiment of the present invention.
C) Printed dot pattern. A heating resistor layer 4 of Ta3i or Ta2N is formed with a film of about 1 μm on an insulating substrate 1 made of ceramic or the like, and a common electrode 2 of Au or At and a lead a3 are placed on top of the layer 4 facing each other in the sub-scanning direction. Let me 1-
Formed with moderate infarct thickness.

Furthermore, an ms tag layer 5 of 8i0z, Ta2 (75, etc.) is formed to a thickness of about 10 .mu.m on top of this.These are deposited by vapor deposition or sputtering, and patterned by photoetching.

Further, by applying a photoresist of 7 on the wear-resistant layer 5 and etching it, the upper surface of the wear-resistant layer 5 is etched.
A depression 11 with a depth of ~6 μm is formed.

By applying a constant pulse of 1 pressure between the common pole 2 and the lead wire 3, the heating resistor 4 is heated, and the wear-resistant layer 5 is heated. When the ink paper 7 and the transfer paper 6 are pressed together so that the ink layer 8 of the ink paper 7 faces the transfer paper 6, the wear-resistant layer 5 is pressed together.
The heat transmitted through the base paper 9 of the ink paper 7 reaches the ink layer 8 and melts the ink, which adheres to the transfer paper 6 to obtain a printing drum (10).

At this time, the depressions 11 create an air layer between the ink paper 7 and the wear-resistant layer 5 and impede heat transfer, so the ink layer 8 corresponding to the depressions 11 does not melt and the printed dots 10 are placed in the center. A non-printed area 12 is formed in the area, which is donut-shaped.

When the pulse width applied between the common 'wL pole 2 and the lead wire 6 is further increased, the amount of heat xI@heated within the heating resistor 4 increases, and the amount of melted ink layer also increases, resulting in the unprinted area at the center of the printed dot. 12 decreases, and the outer periphery of the printed dot also expands 9,
The print field will be even better.

Then, halftone density recording is possible until the central unprinted area 12 is eliminated and adjacent printed dots are spaced to record the maximum print MU.

FIG. 4 is a front view (a) and a sectional view (b) of another embodiment of the present invention. The structure is the same as that of the embodiment shown in FIG. 3, or there are 11 or 4 dents on the surface of the wear-resistant layer 50.

In this case as well, a similar operation creates an unprinted area 12 within the printed dots, so that the same effect as in the embodiment shown in FIG. 6 can be obtained.

FIG. 5 is a front view (α) and a sectional view (b) of another embodiment of the present invention. A feature is that the dimples 11 formed on the wear-resistant layer 5 are donut-shaped grooves. This embodiment also has the same effect as in FIG. 3.

Although the embodiments have been described above regarding a thin-film thermal head, similar effects can be obtained using a similar configuration for a thick-film thermal head.

〔Effect of the invention〕

According to the present invention, by changing the pulse width applied to the heating resistor, it is possible to record everything from printed dots with unprinted areas inside to small printed dots that may be mistaken for momentary contact printed dots. , lower than conventional -1tt
Halftone density recording in the t range is now possible, and the number of halftone density recordings that can be printed in units of printed dots using thermal transfer has doubled from the conventional 2 to 3 gradations to 5 to 6 gradations. .

If this is combined with a dither method using a 2×3 dot matrix, halftone density recording of 3Q to 66 gradations can be realized.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view (α) of a conventional thin-film thermal head;
b) Front view, (C) Printed dot pattern diagram, Figure 2 Fi
1 is a sectional view of the thermal head, FIG. 5 is an (α) sectional view of an embodiment of the present invention, (b) is a front view, and (C) is a printed dot pattern diagram. (cL) front view, (b) sectional view, and FIG.
α) Front view, (b) l#r drawing. 1... Board 2... Common electrode 3... Lead # (terminal) 4... Heating resistor (in order) 5... Endurance Wear layer 6...Transfer paper 7...Ink paper 8...Ink layer 9...Base paper 10...Printed dots 11. ...Kuhomi 12... Unprinted Area Patent Attorney Akio Takaki 1st (α) (b) (C) Figure 2 Figure 3 (8) (b) (c) 4th (d) Figure 5 ((n

Claims (1)

[Claims] 1. In a thermal head in which heating resistors are arranged in the scanning direction on an insulating substrate, a common electrode and a lead holder are placed facing each other at a certain distance, and a wear-resistant layer is formed on top of the common electrode, the heating resistor is placed directly above the heating resistor. A thermal head characterized in that at least one dent is provided on the surface of the wear-resistant layer.