JP2002046297A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compatibly speed up and miniaturize a thermal printer. SOLUTION: A heating part 15 for preheating is formed on a flat glaze of an alumina substrate 12. A heating part 16 for printing is set to the rear of the heating part for preheating. The heating part 16 has a partial glaze 22 swollen in an arc, with heating elements 23 and 24 formed to a position closer to the heating part 15 than to the top. Since the heating part 15 for preheating is formed on the flat glaze and the heating part 16 for printing is formed on the partial glaze 22, a thermal head 10 is stabilized in touching even when a radius of curvature of a platen roller or the partial glaze 22 is made small. The heating part 15 for preheating and the heating part 16 for printing are driven by separate power supply circuits. A voltage change by simultaneous driving is thus prevented and a density irregularity is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head, and more particularly, to a thermal head for preheating and a heating unit for printing.
The present invention relates to a thermal head provided with two heat generating sections.

[0002]

2. Description of the Related Art Thermal recording includes thermal transfer recording in which the ink of an ink film is transferred to recording paper, and thermal recording in which heat-sensitive recording paper is heated to develop color. For example, in the color thermosensitive recording method, a color thermosensitive recording paper in which a yellow thermosensitive coloring layer (Y), a magenta thermosensitive coloring layer (M), and a cyan thermosensitive coloring layer (C) are sequentially provided on a support is used. Each heat-sensitive coloring layer is colored by heating with a thermal head to record a full-color image. In order to selectively color each thermosensitive coloring layer, each thermosensitive coloring layer has a different heat energy required for coloring, and the deeper the thermosensitive coloring layer, the higher the heat energy required. Then, the Y layer is not colored when the M layer is recorded, and the Y layer is not colored when the C layer is recorded.
Immediately after the recording of the layer and the M layer, each layer is irradiated with an ultraviolet ray or a violet visible light in a wavelength range peculiar to the layer to perform light fixing.

In order to cause each of the thermosensitive coloring layers to develop a desired density, the thermal energy immediately before the coloring (hereinafter referred to as bias thermal energy) is replaced by the thermal energy for developing the desired density (hereinafter referred to as gradation expression thermal energy). ) Is required. The thermal head has
Heating elements corresponding to the number of line pixels are arranged in one row in the main scanning direction. For example, when thermal recording is performed on a pixel having a density level of "N", the heating element is first energized for a certain period of time (time A) to apply bias thermal energy to the color thermal recording paper. Next, N pulse currents are supplied to the heating element within a predetermined time (time B), and thermal energy for gradation expression is applied to the color thermosensitive recording paper to thermally record the pixels having the density level "N". I do. The recording time for one line is
The time (A + B + C) is obtained by adding the cooling time (time C) of the heating element to these times.

If the line cycle is shortened in order to shorten the printing time, the temperature of the heating element becomes too high, and the surface of the recording paper is damaged by heat and the gloss is deteriorated. In order to improve this, there is a method of providing two types of heating units and heating the recording paper twice to make the temperature per heating element equal to that in low-speed printing. For example, Japanese Patent Application Laid-Open No. Hei 5-2
Japanese Patent No. 61953 describes a thermal head in which first and second thick-film-type heat generating portions are provided in parallel on a substrate. These two types of heat generating portions are close to each other, and the color thermosensitive recording paper sequentially passes through the first heat generating portion and the second heat generating portion. Each heating part is on a cylindrical glaze layer,
A heating element array in which a large number of heating elements (resistance elements) are formed at a constant pitch is provided. In addition, + and-electrodes are connected to both ends of each heating element. The first heat generating unit applies bias heat energy to the color thermosensitive recording paper,
The second heat-generating section gives thermal energy for gradation expression and performs color recording at a predetermined density.

Japanese Patent Laid-Open Publication No. Hei 10-138541 discloses a thermal head in which first and second heating element arrays are formed on one glaze layer having a large radius of curvature. The first heating element array generates bias heat energy and stores the heat in the glaze layer. When the second heating element array generates the gradation thermal energy, the thermal energy and the stored thermal energy are given to the ink ribbon, and the dye of the ink ribbon is transferred to the recording paper to record dots of a predetermined density. I do.

[0006]

In the former thermal head, which is a thick film type having two glaze layers,
In order to press the two heat-generating portions against the color thermosensitive recording paper, a platen roller having a diameter of several tens of millimeters is required. Further, in the latter thermal head, since two heating element arrays must be provided in parallel on one glaze layer, the radius of curvature of the glaze layer becomes large, the pressing force of the head becomes insufficient, and the granularity is reduced. Has the drawback that it becomes worse.

In any thermal head, since the two heating element arrays are connected in parallel, when driven simultaneously, the first heating section or the second heating element array is reduced due to a voltage drop by the second heating section or the second heating element array. Since the bias thermal energy generated in one heating element array fluctuates, density unevenness may occur. Furthermore, since the heating time during the bias heating is short, ridges are formed on the resin layer on the surface, so that the head touch of the second heating portion or the second heating element array becomes unstable during the gradation expression heating, and the graininess is reduced. It will deteriorate.

An object of the present invention is to provide a thermal head capable of reducing the size of the thermal printer and improving the graininess by reducing the radius of curvature of the glaze layer or the diameter of the platen roller. Is what you do.

Another object of the present invention is to provide a thermal head capable of preventing the occurrence of density unevenness by preventing a voltage drop in a heat generating portion that generates thermal energy for expressing gradation. .

[0010]

In order to achieve the above object, a thermal head according to the present invention is directed to a thermal head in which a heating part for preheating and a heating part for printing are formed on a substrate and extend in parallel with the main scanning direction. , The printing heating section is formed on a partial glaze in which the heating elements bulge in an arc shape, and the preheating heating section is located on the paper feeding side of the printing heating section, and a single heating element or the number of printing heating elements is provided. A smaller number of heating elements are formed on a plane glaze having a smaller thickness than a partial glaze. Further, the heating element of the printing heat generating unit is formed at a position closer to the preheating heating unit than the top of the partial glaze, and the preheating heating unit and the printing heating unit are driven by separate power supply circuits.

In the preheating heating section, one heating element extends in a line in the main scanning direction, and in the printing heating section, a large number of heating elements are arranged at a predetermined pitch in the main scanning direction.
In addition, the heating part for preheating extends in the main scanning direction in parallel with the linear heating element, and is connected over the entire length of the heating element.
The first and second preheating electrodes are folded back along both sides of the substrate in the main scanning direction.

In the printing heat generating unit, there are a case where one pixel is recorded by two heating elements and a case where one pixel is recorded by one heating element. The former includes a plurality of electrodes connected to one end of each heating element in the sub-scanning direction, and a U-shaped connection line connecting the other ends of two adjacent heating elements. In the latter, a plurality of first electrodes connected to one end of each heating element in the sub-scanning direction, and each first electrode connected to the other end of each heating element and passing between adjacent heating elements. A plurality of alternately arranged second electrodes.

[0013]

FIG. 1 is a perspective view showing the appearance of a thermal head according to the present invention. The thermal head 10 includes an alumina substrate 12 and a printed substrate 13 on a head substrate 11.
Is attached. On the alumina substrate 12, a heating part 15 for preheating and a heating part 16 for printing are provided.
The heating part 15 for preheating is formed on a plane glaze of the alumina substrate 12, and includes a heating element 18 and lead electrodes 19 and 20.
It is composed of The print heating unit 16 includes a partial glaze 22 bulged in an arc shape, a large number of heating elements 23 and 24 formed thereon at a constant pitch, and each heating element 2.
Lead electrodes 25 and 26 connected to one ends of the terminals 3 and 24,
And a connection line 27 connected to the other end of each of the heating elements 23 and 24. Here, the odd-numbered heating elements are denoted by reference numeral 23, and the even-numbered heating elements are denoted by reference numeral 24. The same applies to the lead electrodes 25 and 26.

The heating element 18 has one heating element formed linearly in the main scanning direction. Lead electrodes 19, 2
0 is connected over the entire length of the heating element 18 in the main scanning direction. One lead electrode 19 is made of alumina substrate 1
2 is folded back along the side edge in the main scanning direction to form an L-shape, and the other lead electrode 20 is formed into a U-shape so as to surround the print heating section 16. Lead electrode 19,
When a current is passed between 20, the heating element 18 generates bias thermal energy. The heating elements 23 and 24 are formed at positions closer to the preheating heating section 15 than the top of the partial glaze 22. One end of the heating elements 23 and 24 is connected to the lead electrodes 25 and 26, and the other end is connected in series by a connection line 27 formed in a U-shape. Record the pixels. Lead electrode 2
When a current is applied between the heating elements 5 and 26, the heating elements 23 and 24 generate thermal energy for gradation expression.

FIG. 2 shows the thermal head 10 shown in FIG.
FIG. 4 is a sectional view taken along line AA of FIG. A partial glaze 22 is formed on the alumina substrate 12. Resistors 28 a are formed at a constant pitch on the partial glaze 22, and the resistors 28 a are formed on the alumina substrate 12 in parallel with the partial glaze 22.
b is formed. The lead electrode 25 and the connection line 27 are formed on the resistor 28a at predetermined intervals. Lead electrodes 19 and 20 are formed on the resistor 28b at a predetermined interval. The heating element 23 is constituted by the portion of the resistor 28a between the lead electrode 25 and the connection line 27. Lead electrode 1
The heating element 18 is constituted by the portion of the resistor 28b between the elements 9 and 20. Although not shown, the resistor 28 located between the lead electrode 26 and the connection line 27 is similar to the above.
The heating element 24 is constituted by the portion a. further,
Resistors 28a, 28b, lead electrodes 19, 20, 25,
A protective film 29 made of silicon oxide, silicon nitride, or the like is formed on the connection lines 26 and the connection lines 27.

The color thermosensitive recording paper 30 is sandwiched between the thermal head 10 and the platen roller 31, and is conveyed in the direction of the arrow in FIG. Lead electrodes 19, 2
When a current is applied between 0 and between the lead electrodes 25 and 26, the heating element 18 and the heating elements 23 and 24 generate bias heat energy and gradation expression heat energy, respectively. As a result, the color thermosensitive recording paper 30 develops a color and an image is recorded. Each heating element 2
The positions and sizes of 3, 24 are appropriately determined according to the pixel density, the contact pressure of the thermal head 10, the radius of curvature of the partial glaze 22, and the diameter of the platen roller 31. The position and size of the heating element 18 are appropriately determined according to the contact pressure of the thermal head 10 and the diameter of the platen roller 31.

As shown in FIG. 1, the printed circuit board 13 has a transistor 33 for turning on / off the power to the heating element 18 and a driver I for controlling the heating elements 23 and 24.
C34. The electrodes 35 and 36 are connected to the transistor 33 and the power supply circuit, respectively, and are electrically connected to the lead electrodes 19 and 20 by wire bonding 37. The lead electrode 25 of the heating element 23 is electrically connected to the connection terminal 38 of the driver IC 34, and the lead electrode 26 of the heating element 24 is electrically connected to the electrode 39 by wire bonding 37.

FIG. 3 is a schematic diagram showing the configuration of a color thermal printer using the thermal head of the present invention. The color thermal printer 40 includes a paper feed unit 41, a print unit 42, a light fixing unit 43, a cut unit 44, and a system controller 45.
It is composed of The color thermosensitive recording paper 30 is wound in a roll and stored in a recording paper magazine 46. The color thermosensitive recording paper 30 is sent out of the recording paper magazine 46 by the rotation of the paper feed roller 47. A first transport roller pair 48 is disposed outside the recording paper magazine 46, and conveys the color thermosensitive recording paper 30 to the printing unit 42 while nipping the recording paper 30.

The printing section 42 includes a thermal head 10,
It is composed of a platen roller 31, a second transport roller pair 49, and a paper sensor 50, and is provided in order from the upstream side in the printing direction indicated by arrow A in the figure. The thermal head 10 moves between a printing position where it contacts the color thermosensitive recording paper 30 with an appropriate contact pressure during printing and a retracted position that is separated from the color thermosensitive recording paper 30 and retracted upward during non-printing. A shift mechanism 51 is provided. A platen roller 31 is disposed below the thermal head 10 and supports the color thermosensitive recording paper 30.

The second transport roller pair 49 includes a capstan roller 49a and a nip roller 49b. The paper sensor 50 detects the leading end of the color thermosensitive recording paper 30 and sends a leading end detection signal to the system controller 45. The rotation of the pulse motor 52 is controlled by the system controller 45 via the driver 53.
The forward rotation of the pulse motor 52 causes the capstan roller 49 to rotate.
a is rotated clockwise, and the color thermosensitive recording paper 30 is
Send in the print direction indicated by. At this time, thermal recording is performed on each of the thermosensitive coloring layers of the color thermosensitive recording paper 30 by the thermal head 10. In addition, the capstan roller 49a rotates counterclockwise by the reverse rotation of the pulse motor 52, and feeds the color thermosensitive recording paper 30 in the return direction indicated by the arrow B.

The drive pulses to the pulse motor 52 are counted by a pulse counter 54, and based on this, the system controller 45 specifies a print start position, a recording paper return position, a cut position, and the like. Pulse counter 54
Counts up the drive pulse when the pulse motor 52 rotates forward, and counts down the drive pulse when the pulse motor 52 rotates reversely. It should be noted that instead of counting the driving pulses of the pulse motor 52, the capstan rollers 49a
May be provided with a rotary encoder, and the number of pulses proportional to the feed amount of the color thermosensitive recording paper 30 may be counted to specify various control positions.

On the downstream side of the thermal head 10 in the printing direction, an optical fixing device 55, a cutter 56,
7 are arranged in order. The optical fixing device 55 includes a yellow fixing lamp 55a, a magenta fixing lamp 55b, a reflector 55c, and an optical fixing device driving section 58. The yellow fixing lamp 55a emits violet visible light having a light emission peak in a wavelength range of 420 nm. The magenta fixing lamp 55b emits ultraviolet light having an emission peak of 365 nm. At the time of yellow recording, the system controller 45 turns on the yellow fixing lamp 55a via the optical fixing device driving unit 58 to optically fix the yellow thermosensitive coloring layer.
Also, during magenta recording, the system controller 45
Is a magenta fixing lamp 55 through an optical fixing device driving unit 58.
b is turned on, and the magenta thermosensitive coloring layer is optically fixed. Further, even during cyan recording, the magenta fixing lamp 55b is turned on to bleach unrecorded areas having a yellow tint.

The cutter 56 is driven and controlled by the system controller 45 via a driver 59, and cuts the color thermosensitive recording paper 30. The paper discharge roller pair 57 discharges the cut and recorded color thermosensitive recording paper 30 to the outside of the printer.

FIG. 4 shows a cross section of the color thermosensitive recording paper 30. Cyan thermosensitive coloring layer 6 on support 61
2, magenta thermosensitive coloring layer 63, yellow thermosensitive coloring layer 6
4. The protective layer 65 is sequentially provided. As the support 61, opaque coated paper or plastic film is used. The cyan thermosensitive coloring layer 62 contains an electron-donating dye precursor and an electron-accepting compound as main components,
It develops cyan when heated. The magenta thermosensitive coloring layer 63 contains a diazonium salt compound having a maximum absorption wavelength of about 365 nm and a coupler which reacts with the diazonium salt to form a magenta color. Photodegradation causes loss of color-forming ability. The yellow thermosensitive coloring layer 64 contains a diazonium salt compound having a maximum absorption wavelength of about 420 nm, and a coupler that reacts with the diazonium salt to form a yellow color. Is photodegraded and loses its coloring ability.

FIG. 5 shows the coloring characteristics of the thermosensitive coloring layers 62, 63 and 64. In the color thermosensitive recording paper 30 of this embodiment, the yellow heat-sensitive coloring layer 64 has the lowest coloring heat energy and the cyan heat-sensitive coloring layer 62 has the highest coloring heat energy. When the yellow (Y) pixel is thermally recorded, color thermal energy (BY + GY1) obtained by adding gradation thermal energy GY1 to bias thermal energy BY is applied to the color thermosensitive recording paper 30. The bias heat energy BY is energy immediately before the yellow thermosensitive coloring layer 64 develops a color, and is a constant value. The gradation expression heat energy GY1 is determined according to the color density of the pixel to be recorded. Since the same applies to magenta (M) and cyan (C), only symbols are given.

In FIG. 6, a heating element 18 is connected to a transistor 33 and a power supply 70,
Reference numeral 24 is connected to the driver IC 34 and the power supply 71. The driver IC 34 includes a shift register 72, a latch circuit 73, and an AND gate 74. The transistor 33 is turned on by a bias signal (ON / OFF) from the system controller 45. During printing, the transistor 33 is turned on, and the heating element 18 connected thereto generates bias thermal energy. The power supplies 70 and 71 include a rectifier for rectifying commercial AC,
And a voltage controller, and the output voltage is adjusted according to the type of the thermosensitive coloring layer to be recorded.

1 sent from the system controller 45
The drive data (DATA) for the line includes data of a number corresponding to the number of pixels and the gradation steps. For example, 256
In the case of pixels and 64 gradations, the drive data for one line is composed of 256 × 64 data rows, and each data row is composed of 256 drive data. In the system controller 45, drive data for one line is created as follows. First, the comparison data indicating the first gradation is compared with the image data of each pixel, and when the latter is larger, “1” is output, and when the latter is smaller, “0” is output. This comparison is performed for all pixels in one line, and the image data is converted into serial drive data. This serial drive data (DATA) is transmitted from the system controller 45 at a constant period of a clock signal (CL).
The data is sent to the shift register 72 in synchronization with K) and is converted into parallel drive data for one line.

The drive data converted into parallel signals by the shift register 72 is latched by a latch circuit 73 by a latch signal (LATCH). AND gate 74
Outputs an "H" signal when the latched drive data is "1" when a strobe signal (STB) is input. A transistor 75 is connected to each output terminal of the AND gate 74. When the output signal is "H", the transistor 75 is turned on. Each transistor 75 is connected to each heating element 2 via each connection terminal 38.
3 and 24, and when the transistor 75 is turned on, the heating elements 23 and 24 generate thermal energy for gradation expression.

Subsequently, the comparison data indicating the second gradation is compared with the image data of each pixel, and the data is converted into drive data as described above. The heating elements 23 and 24 are selectively heated according to the converted drive data.
In this way, in the case of 64 gradations, the drive data for one line is read out in 64 times, and each of the heating elements 23 and 24 is selectively heated by the 64 strobe signals, so that the 64th step is performed. A tone image is represented.

Next, the operation of the above embodiment will be described. In FIG. 3, the power supply of the color thermal printer 40 is turned off.
When N, the feed roller 47 and the first and second transport roller pairs 48 and 49 rotate forward to transport the color thermosensitive recording paper 30 to the print unit 42. At this time, the thermal head 10 is set to the retracted position by the shift mechanism 51 so as not to be an obstacle when the leading end of the color thermosensitive recording paper 30 passes. When the leading end of the color thermosensitive recording paper 30 reaches the paper sensor 50, the conveyance of the color thermosensitive recording paper 30 is stopped, and the printer enters a print standby state.

When print start is instructed, the thermal head 10 is set at the print position by the shift mechanism 51. The color thermal recording paper 30 is
And the platen roller 31 to start the thermal recording of the yellow image. First, a bias signal (ON / OF
F) turns on the transistor 33, and the heating element 18
, And the bias thermal energy BY of the first line is applied to the color thermosensitive recording paper 30 to perform the bias heating.
When the bias heating is completed, the color thermosensitive recording paper 30 is transported by one line, and the bias heating of the next line is performed.
At this time, since the heating element 18 and the heating elements 23 and 24 are formed separated from each other by several lines, only the bias heating is performed until the first line reaches the heating elements 23 and 24.

When the first line subjected to the bias heating reaches the heating elements 23 and 24, the driver IC 34 supplies a number of pulse currents corresponding to the image data to the heating elements 23 and 24, and outputs the pulse current to the color thermosensitive recording paper 30. The gradation expression heat energy GY1 for each pixel is applied to develop a color to a desired density. 1
When the recording of the line is completed, the color thermosensitive recording paper 30 is conveyed by one line, and the thermal recording of the next line is performed in the same manner. Thus, the thermal recording and the transport of the color thermosensitive recording paper 30 are repeated until the recording of the yellow image is completed. When the portion where the yellow image is thermally recorded reaches the optical fixing unit 55, the yellow fixing lamp 55a which is turned on by the system controller 45 via the optical fixing unit driving unit 58.
Thereby, the yellow thermosensitive coloring layer 64 is optically fixed.

When the light fixing of the yellow thermosensitive coloring layer 64 is completed, the first and second conveying roller pairs 48 and 49 rotate in the reverse direction to return the color thermosensitive recording paper 30 to the magenta image recording start position in the direction indicated by the arrow B. Transport. During the thermal recording of the magenta image, the heating element 18 causes the color thermosensitive recording paper 3
Zero bias thermal energy BM is applied. Further, the heat generating elements 23 and 24 apply the gradation expressing heat energy GM1 corresponding to the image data to the color thermosensitive recording paper 30. Here, the coloring heat energy (B) of the magenta image
M + GM1) is the heat energy (B) for developing a yellow image.
Y + GY1), but the yellow thermosensitive coloring layer 64
Does not develop color because it is already light-fixed. Then, when the portion where the magenta image is thermally recorded reaches the optical fixing device 55, the magenta thermosensitive coloring layer 63 is optically fixed by the magenta fixing lamp 55b turned on by the optical fixing device driving section 58.

When the light fixing of the magenta thermosensitive coloring layer 63 is completed, the first and second transport roller pairs 48 and 49 are again rotated again to return the color thermosensitive recording paper 30 to the cyan image recording start position as indicated by the arrow B. Transport to At the time of thermal recording of a cyan image, the color thermosensitive recording paper 3 is
Zero is applied to the bias heat energy BC. Further, the heat generating elements 23 and 24 apply the gradation expressing heat energy GC1 corresponding to the image data to the color thermosensitive recording paper 30. In the cyan thermosensitive coloring layer 62, the coloring heat energy (BC + GC1) has a value that does not cause coloring in a normal storage state. For this reason, although the optical fixing property is not given, the portion where the cyan image is thermally recorded is the optical fixing device 5.
When the number reaches 5, the unrecorded area having a yellow tint is bleached by the lit magenta fixing lamp 55b.

The color thermosensitive recording paper 30 is conveyed even after the thermal recording and the light fixing to the thermosensitive coloring layers 62, 63 and 64 are completed, and when the cut position reaches the cutter 56, the cutter 56 operates to cut. Is done. The cut thermal recording paper 30 on which the thermal recording has been performed is discharged outside the printer by a discharge roller pair 57.

In the above embodiment, one heating element 18 formed in a line in the main scanning direction is provided. However, a plurality of heating elements 23 and 24 for printing are divided into a plurality of pieces so as to perform bias heating. May be.

In the above embodiment, the printing heat generating portion 16 is used.
Records one pixel with two heating elements 23 and 24 connected in series, but in order to double the pixel density, as shown in FIG. May be recorded. In this case, an electrode 81 is provided on one side of the heating element 80 and a comb-shaped electrode 82 is provided on the other side.
Is provided. The comb-shaped electrode 82 enters between two adjacent electrodes 81.

In the above embodiment, the color thermosensitive recording paper 30
Flat head substrate 11 arranged substantially parallel to the transfer direction of
An alumina substrate 12 and a printed substrate 13 are provided on the upper side. In the thermal head 85 shown in FIG. 8, an L-shaped head substrate 86 is used, and the alumina substrate 12 is mounted on a horizontal portion thereof and printed on a vertical portion. The substrate 13 may be attached. In this case, as shown in FIG. 3, the capstan roller 49a disposed downstream of the thermal head 10 at a distance L from the thermal head 10 is moved closer to the thermal head 85 by substantially the length of the printed circuit board (PL). Can be arranged.

In the above-described embodiment, the heating part for preheating is arranged on the upstream side in the printing direction, and the heating part for printing is arranged on the downstream side. Conversely, the heating part for printing is arranged on the upstream side and the heating part for printing is arranged on the downstream side. A heating part for preheating may be arranged. Bias heating and gradation expression heating are performed in the printing heat generating portion on the upstream side, and bias heat energy or less is applied in the downstream heating portion for preheating to use for gloss processing. In this case, since the heating is finally uniformly performed by the flat preheating heating section, the surface of the softened color thermosensitive recording paper can be smoothed and a glossing process can be performed.

The above-described embodiment is applied to a thermal printer in which heat recording is performed on a thermosensitive coloring layer of a thermosensitive recording paper and then optically fixed. The thermal head of the present invention uses an ink film to print an image on the recording paper. Can also be applied to a thermal transfer printer that records. Further, the above embodiment is an example applied to a line printer, but can be applied to a serial printer as well.

[0041]

As described above, according to the thermal head of the present invention, the heat generating portion for printing is formed on a partial glaze bulging in an arc shape, and the heat generating portion for preheating is supplied with paper from the heat generating portion for printing. Since a single heating element or a smaller number of heating elements than the number of heating elements for printing are formed on a plane glaze having a smaller layer thickness than a partial glaze, proper head touch can be obtained even when the diameter of the platen roller is small. . In addition, since the heating element for printing is formed at a position closer to the heating part for preheating than the top of the partial glaze, an appropriate head touch can be obtained even if the radius of curvature of the glaze is reduced, and the granularity at the time of printing deteriorates It is possible to reduce the size of the printer without doing this. Also,
Since the heat-generating portion for preheating and the heat-generating portion for printing are driven by separate power supplies, there is no reduction in voltage of each heat-generating portion even when they are driven simultaneously, and there is no density unevenness during printing.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the appearance of a thermal head according to the present invention.

FIG. 2 is a sectional view taken along line AA of the thermal head of FIG.

FIG. 3 is a schematic view of a color thermal printer using the thermal head of the present invention.

FIG. 4 is a cross-sectional view showing a layer structure of a color thermosensitive recording paper.

FIG. 5 is a graph showing coloring characteristics of each thermosensitive coloring layer of a color thermosensitive recording paper.

FIG. 6 is a circuit diagram showing the electrical connection of the thermal head.

FIG. 7 is a perspective view showing another embodiment of the print heating unit.

FIG. 8 is a schematic view showing another embodiment of a thermal head using an L-shaped head substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Thermal head 11 Head substrate 12 Alumina substrate 13 Printed board 15 Heating part for preheating 16 Heating part for printing 18 Heating element 22 Partial glaze 23, 24 Heating element 28 Resistor 29 Protective film 30 Color thermosensitive recording paper 31 Platen roller 33 Transistor 34 Driver IC 40 Color thermal printer 45 System controller 55 Optical fuser

Claims (7)

[Claims] 1. A thermal head in which a heating part for preheating and a heating part for printing extending parallel to the main scanning direction are formed on a substrate, wherein the heating part for printing is a partial glaze in which a heating element bulges in an arc shape. The heating unit for preheating is formed on the paper feed side of the heating unit for printing, and a single heating element or a number of heating elements smaller than the number of heating elements for printing is thinner than the partial glaze. A thermal head formed on a plane glaze. 2. The thermal head according to claim 1, wherein the heating element of the printing heating unit is formed at a position closer to a preheating heating unit than a top of the partial glaze. 3. The heating unit for preheating and the heating unit for printing,
3. The device according to claim 2, wherein the device is driven by a separate power supply circuit.
The described thermal head. 4. The heating element for preheating, wherein one heating element extends linearly in the main scanning direction, and the heating element for printing has a large number of heating elements arranged at a predetermined pitch in the main scanning direction. The thermal head according to any one of claims 1 to 3, wherein: 5. The heating section for preheating extends in the main scanning direction in parallel with the linear heating element, is connected over the entire length of the heating element, and is folded back along both sides of the substrate in the main scanning direction. 5. The thermal head according to claim 4, further comprising a first and a second preheating electrode. 6. The printing heat-generating portion includes: a plurality of electrodes connected to one end of each heat-generating element in a sub-scanning direction;
6. The thermal head according to claim 5, further comprising: a U-shaped connection line connecting the other ends of the heating elements. 7. The printing heat-generating section includes a plurality of first electrodes connected to one end of each heat-generating element in the sub-scanning direction, and a first electrode connected to the other end of each heat-generating element. 6. The thermal head according to claim 5, further comprising: a plurality of second electrodes alternately arranged with each of the first electrodes passing therethrough.