JPH02172757A - Recording head and thermal recorder using such head - Google Patents

Abstract

PURPOSE:To easily record in multiple gradations by so forming a glazed layer as to be thick at a part of a heat generating resistor connected to an electrode having a narrower effective width than the resistor and thin at the substantially central part of the heat generating resistor. CONSTITUTION:In a thermal head 10, a glazed layer 16 is formed as a heat accumulator on an alumina board 17, a resistance layer 15, electrode layers 12, 13 are further formed thereon, partly cut out to form the electrodes 12, 13 and a heat generating element 11, which are covered with a wear resistant layer 14. Here, the width of the electrode at the connecting part of the heat generating element 11 to the electrodes 12, 13 is narrow, and the glazed layer 16 corresponding to the width of the electrode is so formed as to protrude at the connecting part of the heat generating element 11 to the electrodes 12, 13 as a vertex. Accordingly, the shape of the heat generating element 11 is formed in a protruding shape to remarkably concentrate its heat generating temperature. Thus, a recording in multiple gradations can be easily realized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a recording head capable of expressing halftones when recording an image on a recording medium, and a thermal recording device using the recording head. .

[Prior Art] Recording devices such as printers and facsimile machines use multiple dot forming elements provided in a recording head to record information (image signals).
A dot pattern is formed on a recording sheet (a recording medium such as a recording paper or a thin plastic plate) while being selectively driven based on the following information. The formats of such recording devices include a serial type that records while moving the recording head in the width direction of the sheet, a line print type that records a predetermined length in the row direction, and a line print type that records one page at a time. There are page print types that do this.

In addition, recording methods include thermal, inkjet, and wire dot methods. Among these, the thermal method is
It can be divided into a thermal transfer method, which uses an ink sheet to transfer ink to plain paper, and a thermal method, which uses a thermal head to heat the thermal paper to develop color.

2. Description of the Related Art Conventionally, a halftone recording method has been employed to express density differences during color recording or image recording using multiple colors such as cyan, magenta, yellow, and black. Such conventional halftone recording generally employs a method based on the principle of binary recording. To express gradation using this method, multiple dots are treated as one unit,
A method of expressing pseudo-halftones using an area gradation method such as a dither method, in which halftones are expressed by the on/off (binary) ratio of dots in the unit, has been used.

[Problem to be solved by the invention] However, when the above-mentioned area gradation method is adopted, the number of dots required for one pixel increases in order to express many gradations, resulting in a decrease in image resolution. There is a problem with doing so. In order to obtain, for example, an image with 64 gradations and a resolution of about 6 pixels/mm by this area gradation method, the resolution of the recording head needs to be about 48 dots/mm. To achieve this with a thermal printer, 4
An 8 dot/mm thermal head is required, but
It is extremely difficult to manufacture such a high-density thermal head, and even if it were possible to manufacture it, the number of elements would be enormous, which would require a large-scale drive circuit to drive the thermal head, making it impractical. In other words, there is a limit to the ability to obtain high-quality gradation recording with binary recording, and there has been a need to put into practical use multi-value gradation recording that expresses the size of one dot in multiple gradations by some method. .

Conventionally, in recording by thermal melt transfer using a commonly used thermal head, density changes corresponding to changes in applied energy are as shown in FIG. 14(A). That is, the rate of change in recording density with respect to applied energy is large;
Furthermore, the variation in recording density was large, as shown by the length of the vertical line in the graph, so it was difficult to achieve an intermediate density. In the conventional thermal head shown in FIG. 14(B), the heating element 101 and the electrode 102 are shaped to have the same width, so the distribution of the current flowing through the heating element 101 is almost uniform. Note that 103 indicates the direction in which the current flows. For this reason, the temperature distribution of the heating element 101 is such that the central portion of the heating element 101, where the amount of heat dissipated is relatively small, has a slightly higher temperature. Therefore, by changing the application time of the pulse voltage applied to the electrode 102, the heating element 1°1
Even if the temperature distribution of 111A and 112A (applying time is IIIA<112A) is changed as shown in FIG. 14(B), the temperature of the heating element 101 is higher than the melting point T1 of the thermal transfer ink. Whether it is or not is,
It is extremely delicate depending on its location. Therefore, Fig. 14 (
As shown in A), the same applied energy is applied to the heating element 101.
Even if the voltage is applied to the heating element, the recording density will differ due to the slight difference in the position of the heating element. For this reason,
Since the conventional thermal transfer recording method using a thermal head can only perform binary recording, it has been desired to improve gradation reproducibility.

The present applicant proposed a thermal head capable of multilevel recording in Japanese Patent Laid-Open No. 63-54261. According to this, the width of the electrode at the connection point between the electrode and the heating element is made equal to or less than the effective recording width of the heating element.

As a result, in one heating element, it is possible to generate heat intensively, especially in the heating element part near the connection point with the electrode, so by changing the energy applied to the thermal head, the heating element part can be heated centrally. The transferred area can be changed. In this way, by adjusting the applied energy in accordance with the gradation, it is possible to realize halftone expression by area modulation. However, even with a thermal head configured like this, sufficient gradation cannot be obtained when recording on recording paper with an uneven surface, and there is a desire to create a thermal head with even better gradation. Ta.

The present invention has been made in view of the above-mentioned conventional examples, and an object of the present invention is to provide an inexpensive recording head capable of multi-level recording and easily realizing multi-gradation recording, and a thermal recording device using the recording head. With the goal.

[Means for Solving the Problems] In order to achieve the above object, the recording head of the present invention has the following configuration. That is, a plurality of heating resistors arranged in a row, an electrode whose width is narrower than the effective width of each of the heating resistors and for supplying electrical energy to each of the heating resistors, and The heating resistor has a glaze layer that is thick at a portion where the resistor and the electrode are connected and thin at a substantially central portion of the heating resistor.

Further, a thermal recording apparatus using the recording head of the present invention that achieves the above object has the following configuration. That is, a plurality of heating resistors arranged in a row, an electrode whose width is narrower than the effective width of each of the heating resistors and for supplying electrical energy to each of the heating resistors, and A recording head is provided with a glaze layer that is thick at the portion where the resistor and the electrode are connected and thinner at approximately the center of the heat generating resistor; a gradation determining means for determining the gradation of image data to be recorded by each heating element of the recording head in accordance with the gradation; and a recording means for recording by energizing each heating element of the recording head according to the gradation. have

[Function] With the above configuration, the thermal recording device inputs a multi-value image signal and determines the gradation of image data to be recorded by each heating element of the recording head in accordance with the gradation of the multi-value image signal. do. Then, according to this gradation level, each heating element of the recording head is energized to perform recording.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments described below will be explained using a thermal recording method using a thermal head as an example, but the present invention is not limited to this. For example, an image can be recorded by ejecting an ink liquid using heat. It can also be applied to a recording method that records an image using heat, such as an inkjet recording method.

[Description of the thermal head (Figs. 1 to 3)] Fig. 1 is a diagram showing the shapes of one heating element 11 and electrodes 12, 13 of the thermal head 10 of the first embodiment. A)
is its enlarged front view, and Fig. 1 (B) is E- of Fig. 1 (A).
A cross-sectional view showing the cross-sectional shape of E', FIG. 1(C) is similar to FIG.
It is a sectional view showing the cross-sectional shape of FF' of A).

In FIG. 1, reference numeral 11 denotes one heating element of the thermal head 1o, and this thermal head 10 includes this heating element 11.
Image recording is performed by selectively energizing these heating elements in accordance with recording data. 12 is a common electric bridge for supplying power to each heating element, and 13 is a signal electrode provided corresponding to each heating element. By changing the voltage level in accordance with recorded data, the heating element Power supply control to 11 is executed.

Next, the heating element 11 and electrodes 12 and 13 of the thermal head 10 of this embodiment will be explained based on FIGS. 1(B) and 1(C). A glaze layer 16 as a heat storage portion is formed on the alumina substrate I7. Furthermore, films of a resistance layer 15 and an electrode layer 12 (13) are formed thereon by vacuum evaporation, sputtering, or the like. Then, a part of the electrode and the resistance layer is cut out by photolithography, photoetching, etc. to form the electrode 12, 13 and the heating element 11,
Further, a wear-resistant layer [14] is formed thereon by sputtering or the like. The portion called the heating element 11 here refers to the resistor N15 portion between the electrodes 12 and 13. Note that the wear-resistant layer includes all layers that function as a protective film, such as an anti-oxidation layer.

As is clear from FIG. 1, the heating element 11 and the electrode 12.
The electrode width of the connection portion to which 13 is connected is narrower than the width of heating element 11. In addition, these electrodes 12.13
The glaze layer has a width equivalent to that of the heating element 11 and the electrode 12.1.
Since the heating element 11 protrudes with the connecting portion with 3 as the apex, the shape of the heating element 11 is convex at this portion.

FIG. 2(A) shows an electrode 1 which is narrower than the width of the heating element 11 of the thermal head 10 shown in FIG.
2.13 is a diagram showing the flow of current when a pulse voltage is applied through.

In FIG. 2(A), 20 indicates the current flowing through the heating element 11, and the density of the current flowing through the heating element 11 is large near the connection point between the narrow electrode 12.13 and the heating element 11. It becomes.

FIG. 2(B) is a diagram showing the temperature distribution near the electrode 12 in the heating element 11 (in the GG' cross section of FIG. 2(A)).

Near this electrode 12 (or electrode 13) (near the connection point)
The temperature of the heating element 11 is particularly high among the heating elements 11, and the temperature difference with other parts of the heating element 11 is large. Then, in order to change the energy applied to the heating element 11, when the application time of the pulse signal applied to the heating element 11 is gradually lengthened, the temperature distribution in the width direction in the xx' cross section of the heating element 11 becomes , curve 21- in FIG. 2(B)
It changes like 22-23. In Figure 2 (B), T
, indicates the melting point of the ink on the ink sheet, and in a temperature range higher than this, the ink on the ink sheet will be melted and transferred to the recording sheet.

Here, the wear-resistant layer 14 of this thermal head 10 is shaped to swell with the connection point between the heating element 11 and the electrode 12.13 as the apex, and the center of the heating element 11 is slightly concave, so that The pressing force applied between the head 10 and the recording paper is concentrated at and in the vicinity of the connection between the electrode 12.13 and the heating element 11. Furthermore, since the glaze layer 14 is thicker in that area, heat storage in that area increases, and the effect of concentration of heat generation temperature becomes more pronounced. This makes it easier for the ink on the ink sheet to be transferred in this area.

As a result, as shown in FIG. 2(C), among the heating elements 11 of the thermal head 10, the temperature region (transfer region) higher than the melting temperature Tffi of the ink on the ink sheet is
21 in Fig. 2(C) corresponding to the temperature distribution in Fig. 2(B).
A, 22A, 23A. Further, as shown in FIG. 1, since the heating element 11 has a convex shape, the transfer and reproducibility in the low recording density region where the dot area is small is excellent.

FIG. 3 is a diagram showing the relationship between applied energy and recording density in this thermal head IO.

In FIG. 3, the slope (rate of change) of the recording density with respect to the magnitude of the applied energy applied to the thermal head 10 is sufficiently smaller than in the case of FIG. 15(A), and the recording density with respect to each applied energy is The variation has also become smaller, as shown by the length of the vertical line in the graph. As a result, halftones can be expressed by controlling the applied energy, and it can be seen that variations in recording density in halftone recording are sufficiently small and stable.

[Description of other thermal heads (Figs. 4 to 13) Fig. 4 is a diagram showing the shapes of the heating element 11a, common electrode 12b, and signal electrode 13b of the thermal head 24 of the second embodiment. Fig. 4(A) is an enlarged front view thereof, Fig. 4(CB) is a sectional view showing the cross-sectional shape of Fig. 4(A) along line H-H',
FIG. 4(C) is a sectional view showing the cross-sectional shape taken along line II' in FIG. 4(A).

In this thermal head 24, the width of the electrodes 12a and 13a is narrower than the width of the heating element 11a, similar to the heating element 11 shown in FIG. The structure of the heating element 11a will be explained with reference to FIGS. 4(B) and 4(C). A glaze N16a as a heat storage portion is formed on an alumina substrate 17a.

Furthermore, films of a resistance layer 15a and an electrode layer 12a (13a) are formed thereon by vacuum evaporation, sputtering, or the like. Then, by cutting out a part of the electrode layer and the resistance layer by photolithography, photoetching, etc., the electrode 12a,
13a and the heating element 11 are formed, and a wear-resistant layer 14a is further formed thereon by sputtering or the like. Here, the portion called the heating element 11a is the electrode layer 12a and 13
This refers to the portion of the resistance layer 15a between the portions a.

Further, as shown in FIG. 4(C), the glaze layer 16a at the center of the heating element 11a is thin, and thicker at the bottom of the electrodes 12a and 13a, so that the center of the heating element 11a is concave. . As a result, the amount of heat stored near the connection between the electrode and the heating element 11a, which is the center of heat generation, increases.
The amount of heat dissipated from the central portion (concave portion) of the heating element 11a increases. Therefore, as described in the first embodiment, the transfer area expands around the connection portion, and by controlling the energy applied to the head, halftone expression can be achieved.

FIG. 5 is a diagram showing the shapes of one heating element 11b and electrodes 12b, 13b of a thermal head 25 of the third embodiment.
FIG. 5(A) is an enlarged front view thereof, FIG. 5(B) is a sectional view showing the cross-sectional shape of J-J' in FIG. 5(A), and FIG.
) is a cross-sectional view showing the cross-sectional shape of FIG. 5(A).

In FIG. 5, llb is one heating element of the thermal head 25, and this thermal head 25 is one heating element of the thermal head 25.
Image recording is performed by selectively energizing these heating elements in accordance with recording data. 12b is a common electrode for supplying power to each heating element, and 13b is a signal electrode provided corresponding to each heating element.By changing the voltage level in accordance with recorded data, the heating element 11b Power supply control is executed.

Next, based on FIGS. 5(B) and 5(C), the heating element 11b and electrodes 12b, 13 of the thermal head 25 of the third embodiment will be explained.
Part b will be explained. As in the previous embodiment, a glaze layer 16b serving as a heat storage portion is formed on an alumina substrate 17b. Further, a resistive layer 15b, an electrode layer 12b (13
Form the film b). Then, electrodes 12b, 13b and heating element 11 are formed by cutting out a part of the electrode layer and resistance layer by photolithography, photoetching, etc., and a wear-resistant layer 14b is further formed thereon by sputtering, etc. The part called heating element 11b here is
This refers to the portion of the resistance layer 15b between the electrode layers 12b and 13b.

As is clear from FIG. 5, the heating element 1.1b and the electrode 1
The electrode width of the connecting portion where 2b and 13b are connected is narrower than the width of the heating element 11b, and these electrodes 12b
, 13b [14b is the heating element 11b]
Since the heat generating element 11b protrudes with the connecting portion between the electrodes 12b and 13b as the apex, this portion has a convex shape.

FIG. 6(A) is a diagram showing the flow of current when a pulse voltage is applied to the heating element 11b of the thermal head 25 shown in FIG. 5 through electrodes 12b and 13b narrower than the width of the heating element 11b. be. In FIG. 6(A), 26 indicates the current flowing through the heating element 11b, and the density of the current flowing through the heating element 11b is determined by the narrow electrode 1.
It is large near the connection point between 2b, 13b and heating element 11b.

FIG. 6(B) is a diagram showing the temperature distribution near the electrode 12b in the heating element 11b (in the LL' cross section of FIG. 6(A)).

The temperature near the second electrode 12b (or electrode 13b) (near the connection point) is particularly high among the heating elements 11b, and the temperature difference with other parts of the heating elements 11b is large. Then, in order to change the energy applied to the heating element 11b, the application time of the pulse signal applied to the heating element 11b is gradually lengthened (and the L of the heating element 11b is changed).
The temperature distribution in the width direction in the -L' cross section changes as shown by curves 42-43-44 in FIG. 6(B). In FIG. 6(B), T indicates the melting point of the ink on the ink sheet, and in a temperature range higher than this, the ink on the ink sheet will be melted and transferred to the recording sheet.

Here, the wear-resistant layer 14b of this thermal head 25 is
Since the heating element 11b has a shape that rises up with the connection point between the heating element 11b and the electrodes 12b and 13b as its apex, and the center of the heating element 11b is slightly concave, the pressing force applied between the thermal head 25 and the recording paper is The heat is concentrated at the connection portion between the electrodes 12b, 13b and the heating element 11b and the vicinity thereof. Also,
Since the wear-resistant layer 14b is thicker in that portion, heat storage in that portion increases, and the effect of concentration of heat generation temperature becomes more pronounced. This makes it easier for the ink on the ink sheet to be transferred in this area.

As a result, as shown in FIG. 6(C), among the heating elements 11b of the thermal head 250, the temperature region (transfer region) where the melting temperature T of the ink of the ink sheet is higher is as shown in FIG. 6(B). 42A in Fig. 6(C) corresponding to the temperature distribution.
, 43A, 44A. Further, as shown in FIG. 5, since the heating element 11b has a convex shape, the transfer and reproducibility in the low recording density region where the dot area is small is excellent. The relationship between the energy applied by the thermal head 25 formed in this manner and the recording density is as shown in FIG. 3 described above.

Further, this thermal head 25 is also excellent in durability. This is because, in general, the thermal head and recording paper (
The deterioration of the thermal head due to friction with the ink sheet (or ink sheet) tends to progress more rapidly as the temperature of the head increases. On the other hand, in the heating element 11b of the thermal head 25 of this embodiment, the wear-resistant layer 14b is thickened near the connection portion between the electrodes 12b, 13b and the heating element 11b, where heat is generated intensively and the temperature rises. Therefore, the thermal head 25 as a whole has excellent wear resistance.

FIG. 7 is a diagram showing the shapes of one heating element 11c and electrodes 12c, 13c of a thermal head 27 of the fourth embodiment.
FIG. 7(A) is an enlarged front view thereof, FIG. 7(B) is a sectional view showing the cross-sectional shape of FIG. 7(A) along line N-N', and FIG. 7(C
) is a cross-sectional view showing the cross-sectional shape taken along line MM' in FIG. 7(A).

28 is a recess provided almost in the center of the heating element 11c, and this part is directly on the alumina substrate 17c, and the wear-resistant layer 1
Since electrodes 12c and 1 are only stacked, electrodes 12c and 1
The current flowing between the two end portions 31.3 of the recess 28
The current density is concentrated around 2, and the current density in this area is high. In the portions 31 and 32 where the current density is high, the thickness of the glaze layer 16c is increased to make it protrude from the surroundings (
Figure 7 (B) (C)). As a result, the thermal head 2
The pressing force between 7 and the recording paper is concentrated in this part, and by increasing the thickness of the glaze P7116c in this part, the heat storage in the heat generating center increases, and the effect of concentrating the heat generating energy becomes more pronounced. As a result, this part 31.32
The transfer area spreads around the center, and by changing the applied energy, the area to be transferred can be changed as shown in FIG.

In FIG. 8, 51 to 53 indicate the transfer area for each applied energy, and by changing the transfer area by the heating element 11c in this way, halftones can be expressed. In addition, in order to adjust the thickness of the glaze, fine particles such as inorganic particles (alumina particles, etc.) may be added to the thickened portion.

FIG. 9 is a diagram showing the shape of one heating element lid and electrodes 12d and 13d of the thermal head 29 of the fifth embodiment.
9(A) is an enlarged front view thereof, FIG. 9(B) is a sectional view showing the cross-sectional shape of PP' in FIG. 9(A), and FIG. 9(C
) is a cross-sectional view showing the cross-sectional shape of YY' in FIG. 9(A).

Since the heating element lid has a constriction in the middle, the current flowing from the common electrode 12d to the signal electrode 13d is concentrated at this constriction. Therefore, the thickness of the wear-resistant layer 14d is increased in the portion where the current density is high to make it protrude from the surrounding area. This increases the pressing force on the recording paper or the like at this protruding portion, improving transferability. In addition, by increasing the thickness of the wear-resistant layer 14d in the central part where heat is generated, heat storage in this part increases, so the effect of concentrating heat energy becomes more pronounced, and the ink on the ink sheet is more easily transferred. .

As a result, by changing the applied energy applied to the thermal head, the area of the dots to be transferred can be changed to 9th.
] It is possible to perform halftone expression by changing as shown in 61 to 63. Furthermore, as explained in the above embodiment, since the wear-resistant layer 14d in the heat generating center is thickened,
The head has excellent durability.

FIG. 11 shows a heating element 1 of a thermal head according to a sixth embodiment.
1e and its electrodes 12e and 13e;
Figure 1 (A) is an enlarged front view, and Figure 11 (B) is the 11th
FIG. 11(C) is a cross-sectional view showing the cross-sectional shape along line QQ' in FIG. 11(A), and FIG. 11(C) is a cross-sectional view showing the cross-sectional shape along line RR' in FIG. 11(A).

In the figure, 71 and 72 are insulating parts provided near the connection parts between the electrodes 12e and 13e and the heating element lie;
The current flowing through the heating element 11e concentrates on the portions of the electrodes 12e and 13e connected to the heating element lie (four corners of the heating element 11e). Therefore, by increasing the thickness of the wear layer 14e [the surface corresponding to the part where the current density increases],
Make that part stand out from its surroundings. This makes it possible to express halftones by changing the area transferred by this thermal head for the same reason as in the above-mentioned embodiment.
By increasing the thickness of the wear-resistant layer 14e at the heat generating center, the durability of the thermal head can also be improved.

Further, FIG. 12 is a diagram showing the shapes of the heating element 11f and its electrodes 12f and 13f of the thermal head of the seventh embodiment. As in the case of FIG. 11, FIG. '
The sectional view taken along line T-T' is shown in FIG. 12(C).

In FIG. 12, since 73 and 74 are insulating parts, the current flowing through the heating element 11f is concentrated at the part where the electrodes 12f and 13f are connected (the four corners of the heating element 11f).
This part becomes the center of heat generation. Therefore, the glaze portion 16f, which is the central portion of heat generation, is made thicker so that it protrudes from the surroundings. As a result, in the same manner as in the embodiment described above, by changing the applied energy and changing the transfer area, it is possible to realize halftone expression by area gradation.

FIG. 13 is a diagram showing the transfer area by the heating element shown in FIGS. 11 and 12 in correspondence with the applied energy. Here, the transfer area spreads out from the four corners of the heating element 11e (11f) in accordance with the amount of applied energy. In this way, by adjusting the applied energy, it is possible to change the transfer area and perform gradation expression.

As explained above, according to the thermal heater of this embodiment, the glaze layer at the heat generating center of the heating element is made thicker to increase the heat storage effect and the pressing force against the ink sheet, etc., so as to cope with the applied energy. This enables accurate gradation expression.

Furthermore, according to the thermal head of this embodiment, the density of the current flowing through the heating element is varied, and the wear-resistant layer is made thicker in the part where the current density becomes large (the part where the current density becomes large) so that it protrudes from the surroundings. By doing so, the pressing force and heat storage effect of the head are increased, and it is possible to express gradations with high precision in response to applied energy.

[Description of thermal transfer recording device (Figs. 15 to 17)] No. 15
The figure is a block diagram showing a schematic configuration of a thermal transfer recording apparatus using the thermal head 10 of the embodiment. Here, the case of the thermal head 10 of the first embodiment is shown, but the thermal head of other embodiments is also shown. The same effect can be achieved by using

In FIG. 15, 110 is a plain paper cassette that holds plain paper as a recording sheet, 111 is a sensor that detects the presence or absence of plain paper, and 106 is a conveyor for picking up and transporting plain paper from the cassette 110. It's a motor.

A stepping motor 123 rotates the platen 34 via a speed reduction mechanism (not shown). 131 is a motor for raising/lowering the thermal head 10;
The thermal head 10 is driven by this motor 131.
It is pressed against the platen 34 via the ink sheet 32 and recording paper (down state), or separated from the platen 34 (up state). Also, 139 is ink sheet 3
The rotation of the motor 13 is transmitted to the drive shaft of the take-up roll 140, and the ink sheet 32 is taken up in the direction of the arrow. Further, 141 is a supply roll for the ink sheet 32.

35 is a buffer memory that temporarily holds input image data; 36 is an image data conversion table that converts the image data read out from the buffer memory 35, and is usually composed of a look-up table in a ROM or the like. 37
16 is a head drive pulse control circuit whose details are shown in FIG.

FIG. 17 is a block diagram showing the configuration of the thermal head 10.

In the figure, reference numeral 11 denotes a heating element, and each heating element is created based on the above-described embodiment, and is provided for one line in the width direction of the recording paper. A latch circuit 233 latches one line of recording data, and a shift register 234 sequentially inputs serial recording data (gradation data) 444 in synchronization with a clock signal CLK. The serial data thus input to the shift register 234 is transmitted to the latch signal 2
35, the data is latched by the latch circuit 233 and converted into parallel data. In this way, the recording data corresponding to each heating element is held in the latch circuit 233. and,
The timing and time for voltage application are determined by the strobe signal 5TB445, and the AND circuit 2 with data
Output transistor 231 connected to 32 is turned on.

As a result, current is applied to the signal electrode 13 of the corresponding heating element 11 from the common electrode 12, and the heating element 11 is driven to generate heat.

Next, referring to FIG. 16, head drive pulse control circuit 3
7 will be explained.

450 is an oscillator that outputs a clock CLK of a predetermined frequency, and 451 is a frequency divider circuit that divides the clock signal CLK and outputs a latch signal 235 every time the number of heating elements in one line of the thermal head 10 is counted, for example. be. 440
is a gradation conversion decoder that corresponds to each pixel of input pixel data and transfers gradation data 444 to each register stage of the shift register 234 in synchronization with the CLK signal. As a result, when processing a color image, for example, the gradation conversion decoder 440 performs gradation conversion for each color of YM and C.

441 is a gradation counter, which counts up every time the latch signal 235 is input, and receives the instruction signal 44 from the CPU 38.
3, for example, when using a sublimation ink sheet, use the mod
64 (6 bits), and when using a fusible ink sheet, mod 16 (4 bits) is used. The gradation conversion decoder 440 compares the counted value from the gradation counter 441 with each input pixel data, and when the pixel data is larger or equal, outputs "1" as the gradation data 444, and If the data is smaller, “
The strobe signal generation circuit 442 outputs the strobe signal 5T a little later than the latch signal 235.
B445 is output, thereby driving the heating element to perform recording.

FIG. 18 is a diagram showing the driving of the thermal head 10 and the timing of the strobe signal STB in the embodiment.

The thermal head 10 is a line type head, and 70 indicates the recording timing for one line.

Assuming that the image data per pixel input to the gradation conversion decoder 440 is composed of, for example, 6 bits, there can be 64 types of data per pixel.

Therefore, in this case, N of N gradations is "64". First, one line of data 444 corresponding to the first STB signal signal is transferred to the shift register 234.
It is latched by the latch circuit 233 by the latch signal 235. Next, the strobe signal B+ is output, and the heating element that outputs data "1" by the pulse width of B1 is driven. During this heat generation drive, the next gradation data 444 is input to the shift register 234, and when the STB signal 445 falls, the latch signal 235 causes the latch circuit 233 to
latched to. In this way, the STB signal is then output on B2. Such an operation is executed 64 times (STB signal -B, 4), and recording for one line is completed.

That is, the gradation conversion decoder 440 inputs image data,
When the value of the m-th pixel data of the line to be recorded in the image is "20", the value of the gradation counter 441 is placed in the m-th stage of the shift register 234 corresponding to the position of the pixel data. With reference, data 444 is output 64 times in total such that the first 20 pieces of data are "1" and the latter 44 (64-20) pieces of data are "0".

However, at this time, it goes without saying that data is set in other stages of the shift register 234 in accordance with the gradation level of the corresponding pixel.

At this time, each strobe signal STB is
The pulse width is changed depending on the number of times the TB signal is output. The strobe signal generation circuit 44 executes such pulse width adjustment of the strobe signal STB.
It is 2. As described above, this strobe signal generation circuit 442 receives the gradation data 444 corresponding to the type of ink sheet 32 from a corresponding ROM table, etc., and receives the STB signal 444 corresponding to the type of ink sheet 32.
The width and period of 45 are adjusted.

FIG. 19 is a flowchart showing the recording process in the thermal transfer recording apparatus of the embodiment, and a control program for executing this process is stored in the ROM of the CPU 38.

When image data is input in step S1, the process proceeds to step S2, and the image data is stored in the buffer memory 35. In step S3, the recording paper is picked up from the cassette 110 and conveyed to the recording position, and in step S4, the ink sheet 32 is conveyed so that the desired position of the ink sheet 32 is at the recording position. Next, the process proceeds to step S5, where the motor 131 is driven to lower the thermal head IO.

In step S6, one line of pixel data is read from the buffer memory 35 and output to the head drive pulse control circuit 37 through the conversion table 36. As a result, the 18th
Gradation data 444, latch signal 235, and strobe signal STB are output at the timing shown in the figure. As a result, the thermal head IO generates heat, and transfer recording is performed on the recording paper. Next, the process advances to step S7, where the recording paper and ink sheet 32 are conveyed by one line, and step S8
Check whether the recording process for one page has been completed. and,
If the recording of one page has not been completed, the process returns to step S6;
The pixel data of the next line is read out from the buffer memory 35, and the above-described recording process is performed again.

In the case of color recording, the recording data of each color is recorded one page at a time, and each time the recording of each color is completed, the colored part of the ink sheet to be recorded next is conveyed to the recording position, and the recording paper is also transferred to the platen. 34, return to the original position, and record in a different color.

By performing this operation for, for example, three colors, Y, M, and C, color recording can be performed on recording paper. Further, the gradation width of the gradation data 444, the pulse width of the strobe signal STB, etc. may be changed depending on the type of ink sheet 32 or recording sheet used.

As explained above, this embodiment has been explained using a thermal recording method using a thermal head as an example, but the present invention is not limited to this. It goes without saying that the present invention can also be applied to a recording method that records an image using heat, such as an inkjet recording method that records images.

As explained above, according to this embodiment, a thermal head is used in which the heat generation temperature distribution can be easily changed by forming the heating elements so that the current density flowing through them differs and changing the applied energy. do. and,
By changing the transfer area by changing the heat generating area of the thermal head in accordance with the gradation level of image data, it is possible to provide a thermal transfer recording device with good gradation reproducibility.

[Effects of the Invention] As explained above, according to the recording head of the present invention, since the recording density can be reliably changed by changing the applied energy, there is an effect that it is suitable for recording halftones.

Further, according to the thermal recording device of the present invention, multivalue recording is possible,
This has the effect of easily realizing multi-gradation recording.

[Brief explanation of the drawing]

FIG. 1(A) is an enlarged front view showing the shape of the heating element and electrode portion of the thermal head of the first embodiment, and FIG. 1(B) is a cross section of the heating element of FIG. 1(C) is a diagram showing a cross section of the heating element of FIG. 1 along line FF', FIG. 2(A) is a diagram showing the current distribution flowing through the heating element of the first embodiment, Figure 2 (B) is a diagram showing the heat generation distribution in the GG' cross section of Figure 2 (A), and Figure 2 (C) is a diagram showing the transfer area corresponding to the applied energy of the heating element of the second embodiment. 3 is a diagram showing the relationship between the recording density and the applied energy in the thermal head of the embodiment, and FIGS. 4(A) to (C) are diagrams showing the shapes of the heating elements and electrodes of the second embodiment. , Figures 5(A) to (C) are diagrams showing the shapes of the heating element and electrodes of the third embodiment, and Figure 6(A) is a diagram showing the current distribution flowing through the heating element of the third embodiment. , FIG. 6(B) is a diagram showing the heat generation distribution in the GG' cross section of FIG. 6(A), and FIG. 6(C) is the transfer area corresponding to the applied energy of the heating element of the third embodiment. Figures 7 (A) to (C) showing
is a diagram showing the shapes of the heating element and electrodes of the fourth embodiment, FIG. 8 is a diagram showing the transfer area when the energy applied by the heating element of the fourth embodiment is changed, and FIGS. (
C) is a diagram showing the shapes of the heating element and electrodes of the fifth embodiment, FIG. 10 is a diagram showing the transfer area when the energy applied by the heating element of the fifth embodiment is changed, and FIG. 11 (A )
- (C) are diagrams showing the shapes of the heating element and electrodes of the sixth embodiment, Figures 12 (A) - (C) are diagrams showing the shapes of the heating element and electrodes of the seventh embodiment, The figure shows the transfer area when the energy applied by the heat generating elements of the sixth and seventh embodiments is changed. Figure 14 (A) shows the relationship between the energy applied by the conventional thermal head and the recording density. , FIG. 14(B) is a diagram showing the shape and temperature distribution of electrodes and heating elements in a conventional thermal head, and FIG. 15 is a block diagram showing a schematic configuration of a thermal transfer recording device using the thermal head of the embodiment.
FIG. 16 is a block diagram showing the schematic configuration of the head drive pulse control circuit, FIG. 17 is a diagram showing the configuration of the thermal head, FIG. 18 is a diagram showing the timing of signals applied to the thermal head, and FIG. 19 is a diagram showing the embodiment. 3 is a flowchart showing recording processing in the thermal transfer recording apparatus of FIG. In the figure, 10, 24, 25, 27. 29... thermal head, 11. Ila~llf... heating element, 12,
12 a to 12 f-... common electrode, 13.13a
~13f...Signal electrode, 14.14a~14f...
Wear-resistant layer, 15. 15a to 15f・”resistance layer, 16
, 16 a ~ 16 f =- Glaze store, 17.17
a ~ 17f... Alumina substrate, 28... Hollow,
71-74... Insulating section, 32... Ink sheet, 3
4...Platen roller, 35...Buffer memory,
36... Image data conversion table, 37... Head drive pulse control circuit, 38... CPU, 39... Display section, 106, 123.131, 139... Motor,
110... Plain paper cassette, 235... Latch signal, 440... Gradation conversion decoder, 442... Strobe signal generation circuit, 444... Gradation data, 445...
...STB signal. Patent Applicant Canon Co., Ltd. Figure (A) Old Figure) Figure (C) Figure (△) Figure (B) Figure (△) Figure (C) Figure (C) Figure 3 Figure (A) Figure 5 (C) Figure (A) Figure (B) Figure (△) Figure (C) Figure 6 (C) Figure 8 Figure 0 (A) d Figure ( C) Figure 12 (A) Figure 12 (C) Figure 11 (A) Figure (C) Figure (△) Figure 13 (B) Figure (C3 Post energy (m'') Figure 14 (A) Figure 16 Figure 17 Figure 19 Procedure 7 Fu official text (method) % formula % Relationship to the case Patent Canon Co., Ltd. Applicant 4゜Representative Tora, Minato-ku, Tokyo No. 105 Gate 2-5 March 28, 1999 (shipped) 6. Brief description of drawings in the specification subject to amendment 7. Contents of amendment

Claims (3)

[Claims] (1) a plurality of heating resistors arranged in a row; an electrode having a width narrower than the effective width of each of the heating resistors and supplying electrical energy to each of the heating resistors; A recording head comprising: a glaze layer that is thick at a portion where the heating resistor and the electrode are connected and thinner approximately at the center of the heating resistor. (2) a plurality of heating resistors arranged in a row; an electrode having a width narrower than the effective width of each of the heating resistors; and an electrode for supplying electrical energy to each of the heating resistors; A recording head comprising: a wear-resistant layer having a convex shape at a portion where the heating resistor and the electrode are connected. (3) a plurality of heating resistors arranged in a row; an electrode having a width narrower than the effective width of each of the heating resistors; and an electrode for supplying electrical energy to each of the heating resistors; a recording head having a glaze layer that is thick at a portion where the heating resistor and the electrode are connected and thinner approximately at the center of the heating resistor; gradation determining means for determining the gradation of image data to be recorded by each heating element of the recording head in accordance with the gradation; and recording means for recording by energizing each heating element of the recording head according to the gradation. A thermal recording device characterized by having the following.