JPS6149864A - Line-type thermal head with auxiliary heating element - Google Patents

Abstract

PURPOSE:To eliminate the shortage of temperature rise during the heating period as well as remove hot lines by providing auxiliary heating dot and paired cells on an upper layer or lower layer through an insulator layer rather than the layer with dot groups in the position in the vertical direction. CONSTITUTION:A thin resistor film of Ta2N, NiC, etc., having a thickness of 0.07mum is laminated on the whole surface of a grazed alumina base plate G by vacuum vapor deposition, etc. A patterning is made in such a way as to leave a belt zone A of 145mum width in the boundary between blocks by photo-etching method. Later, two-layer structures of cell materials (e.g., NiCr/Au, etc.) having a thickness of 1mum are laminated and then a given pattern is formed by photo- etching in order to form an auxiliary heating element dot A and paired cells E to supply electric current to the dot A. The belt resistor positioned between the cells E becomes the dot A to be electrically energized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a line type thermal head used for thermal image recording, and particularly relates to an improvement of a block drive type line type thermal head.

[Background of the invention]

2. Description of the Related Art Methods of reproducing images in the form of hard copies such as photographs from electrical image signals obtained from televisions, video cameras, video discs, electronic cameras, etc. are being actively researched. The most powerful method among these is the thermal image recording method.
This is a thermal recording paper (
This includes not only heat-sensitive color-forming types but also those in which an image-receiving sheet and a heat-transferable ink sheet are stacked) is moved, and only predetermined heating element dots are energized to generate heat based on the input image signal. 1 on the recording paper due to heat
One two-dimensional image is completed by printing pixels for a row and sequentially printing each row of pixels.

In this case, the number of heating element dots corresponding to one row of pixels may reach, for example, 1280, depending on the size of the image. However, when there are many dots like this,
The maximum current that flows when all the dots generate heat is extremely large, so a large power source is required.

Therefore, a method has been proposed in which a group of heating element dots is divided into a plurality of blocks, for example, two blocks, and each block is heated by lightning at different times. Although this method increases the time required to print one row of pixels,
The required maximum current value is 1/2 or less.

By the way, the temperature distribution when one heating element dot is made to generate heat shows a mountain-shaped distribution as shown in Figure 2, and if each block is made to generate heat, if all the dots in the block are made to generate heat, Heat generating block B as shown in Figure 3A
n (dot area with hatching) and non-heat generating block Bn-1-1 (dot area without hatching)
The heat generation temperature at the boundary between the two is low. This is because the outside of the boundary is a non-heat generating block Bn-1-1, so the temperature is low and therefore heat escapes, and this phenomenon cannot be avoided. This phenomenon also occurs when the energization and heat generation operation of the t4 block Bn is completed and the energization and heat generation operation of the next block Bn+l is performed, resulting in a temperature distribution as shown in FIG. 3B. Therefore, the heat generation temperature at the boundary between the blocks is not high enough in either the first operation or the next operation (see Figure 3C).
, Therefore, the printed pixels become discontinuous at the boundary, resulting in white dots.

These white spots naturally appear in the printed image as white streaks (referred to by the inventors as white lines) in the direction of movement of the recording paper, etc.

This white line becomes a fatal drawback when creating images such as photographs.

[Purpose of the invention]

Therefore, an object of the present invention is to improve a thermal head that prints one line of pixels by dividing a group of heating element dots into a plurality of blocks and generating heat by energizing each block at different times in order. The goal is to eliminate the line.

[Summary of the invention]

As a result of intensive research, the present inventor found that when a group of heating element dots is divided into a plurality of blocks, the white line can be eliminated by providing an auxiliary heating element between or near the two blocks. , we have achieved the present invention.

Therefore, the present invention consists of a large number of heating element dot groups and a pair of electrode groups for energizing each dot, the heating element dot group is divided into a plurality of blocks, and each block is energized and heated at different times. Therefore, in a block drive type line thermal head that prints one line of pixels, the horizontal position is at or near the boundary between the blocks, and the vertical position is at the boundary between the blocks. No white line occurs, characterized in that one or several auxiliary heating elements and a pair of electrodes for energizing them are provided at a position above or below a certain layer via an insulating layer. We provide line-type thermal heads.

The auxiliary heating element dots characteristically provided according to the invention are:
'When one or both of two adjacent blocks are driven, they are simultaneously driven to generate heat.

If the heating time of each dot is different for gradation expression, the auxiliary heating element dot is made to generate heat for the same heating time as the dot facing the boundary.

This solves the problem that the temperature between the blocks does not rise sufficiently when heat is generated, and as a result, the white line is eliminated.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

(Example) First, a glazed alumina substrate (G) is prepared, and a thin film resistor material such as Ta2N or NiCr is laminated on one surface thereof with a thickness of 0.07 μm by vacuum evaporation or sputtering. By photo-etching, the first A
As shown in Figure (a), patterning is performed to leave a strip (A) having a width of 145 μm at the boundary between blocks. FIG. 1B (a) is a cross-sectional end view taken along arrows x and -x in FIG. 1A (a).

After that, similarly, a 1 μm thick electrode material such as NiCr was used.
A two-layer structure made of /Au is laminated and then processed into a predetermined pattern shown in FIG. 1A (b) by photo-etching. As a result, the auxiliary heating element (A) and each pair of electrodes (E) for supplying electricity to these are formed. The band-shaped resistor material located between a pair of electrodes is a heating element) (
A) and generates heat.

Figure 1B (a) and Figure 1B (b-1
), and the Y, -Y, and arrow sectional end faces are shown in Figure 1B (b-2
). On top of that is an insulating layer (I) such as StO
2+ S + Cb I 3N4 T A, Z20,
s T a F O to a thickness of about 2 μm.

Further, a thin film resistor material having a thickness of 0.07 μm is added and processed into a predetermined pattern shown in FIG. 1A (C) by photo-etching. The width of the resistor (D) is 145 μm and the interval is 30 μm.

Fig. 1B (
Shown in c).

Next, an electrode material having a thickness of 1 μm is laminated, and then processed into a predetermined pattern shown in FIG. 1A (d) by photo-etching. This forms a group of heating element dots (D) and a pair of electrodes (E) for energizing them. 1st A
xa-x3 and Shown in d-2).

On top of that, as a protective FfJ(P), for example, an anti-oxidation layer (
A two-layer structure of 5in2)/wear-resistant layer (Ta2O,) is formed to a thickness of 2μm/5μm to complete the thermal head (see Figure 1).

Here, move the Kamisuke heating element (A) to the block on the left (B
If heat is generated at the same time when driving the right block (Bn-)-1), the temperature distribution (Tn) shown in Fig. 1C will be obtained.
The temperature distribution (Tn+t) shown in Figure D is shown. Therefore, the temperature at the time of heat generation is sufficiently high even at the boundary between block (Brr) and block (Bn+1), and on the contrary, the heat generation time becomes longer near the auxiliary heating element (A), resulting in darker printing. . In order to avoid this, the auxiliary heating element (Drag) (A) is made to generate heat for half the heat generation time of the right end (D) when the left block (Bn) is driven, and when the next right block (CBn+1) is driven. leftmost dora)
The heat may be generated for only half of the heat generation time in (D). If halving the heat generation time is troublesome due to the circuit configuration, you can make only the auxiliary heating element with a material with twice the resistance value, and when driven at constant voltage, the heat generation amount will be halved for the same time. become.

4 and 5 are partial cross-sectional end views of a thermal head showing other embodiments. In the case of FIG. 5, the auxiliary heating element (Dra) (A) generates heat simultaneously when the block (Bn) is driven. and does not generate heat when the block (Bn-1-1) is driven. In this case as well, blocks (Bn) and (Bn-
1-1) The problem of the white line at the boundary is resolved.

FIG. 6 is also a partially sectional end view of a thermal head showing another embodiment. In this embodiment, unlike the other embodiments, the auxiliary heating element dots (A) are provided above the heating element dots (D) group via the insulating layer (I). Therefore, the heat utilization efficiency of the heating element group (D) decreases, and this has a large effect.

(Effects of the Invention) As described above, according to the present invention, since the auxiliary heating element dots are provided at or near the boundaries of blocks, the insufficient temperature rise during heat generation is solved, and as a result, the white line problem is solved.

[Brief explanation of the drawing]

FIG. 1 is a partial end view of a cross section obtained by cutting a thermal head according to an embodiment of the present invention perpendicular to the main scanning direction. FIGS. 1A to 1D are partial plan views of each manufacturing process of the thermal head according to the above-described embodiment. Figure 1B (a) is X, -X in Figure 1A (a) and (b)
, is a cross-sectional end view taken in the direction of arrows. FIG. 1B (b-1) is a cross-sectional end view taken along the line X2-X2 in FIG. 1A (b). FIG. 1B (b-2) is a cross-sectional end view taken along Y--Y in FIG. 1A (b). FIG. 1B (C) is a cross-sectional end view taken along arrows X and -X3 in FIG. 1A (C) and FIG. 1A (d). Figure 1B (d-t) is X4-X in Figure 1A (d). FIG. FIG. 1B (d-2) is a sectional end view taken along Y2-Y2 in FIG. 1A (d). FIG. 1C shows a block (Bn
) is a graph showing the temperature distribution when driving to generate heat. FIG. 1D shows a block (Bn
1) is a graph showing the temperature distribution when driving and generating heat. FIG. 1E is a composite diagram of FIGS. 1C and 1D. FIG. 2 is a graph showing the temperature distribution when one heating element (D) is heated. The MaA diagram shows a conventional thermal head block (Bn
) is a graph showing the temperature distribution when driving to generate heat. FIG. 3B shows an adjacent block (B) of a conventional thermal head.
FIG. FIG. 3C is a composite diagram of FIGS. 3A and 3B. 4 to 6 are partial end views of cross sections obtained by cutting a thermal head according to another embodiment of the present invention perpendicular to the main scanning direction. [Explanation of symbols of main parts] A: Auxiliary heating element dot or resistor material therefor. D... Heating element dot or resistor material therefor. E... Electrode. ■・・・Insulating layer. G... Glazed alumina substrate. P...Preservation layer.

Claims (1)

[Claims] Consisting of a large number of heating element dot groups and a pair of electrode groups for energizing each dot, the heating element dot group is divided into a plurality of blocks, and by energizing and generating heat at different times for each block, one row's worth of heat can be generated. In a block-driving line type thermal head that prints pixels, the horizontal position is at or near the boundary between the blocks, and the vertical position is at the insulating layer below the layer where the dot groups are located. A line-type thermal head that does not produce a white line, characterized in that an auxiliary heating element dot and a pair of electrodes for energizing the dot are provided at a position corresponding to the upper layer or the lower layer via the auxiliary heating element dot.