JPH02286357A - Recording head and thermal recording device using the same recording head - Google Patents

Abstract

PURPOSE:To bias the density of current conducted through heat generating resistant bodies and permit the representation of medium tone by a method wherein a second electrode, separated from a first electrode connected to one side of the heat generating resistant bodies and connected to two sides of the same except the opposing side of the same body which is connected to the first electrode, is provided in the title recording head. CONSTITUTION:Resistant bodies 3 generate heat by electric current which flows from a common electrode 12, impressing a voltage on the heat generating resistant bodies 3 respectively, to a signal electrode 1. Since the current, conducted through the heat generating resistant bodies 3, has a tendency to flow through the shortest part of a distance between electrodes, the temperature of an area (a) becomes high when an impressing energy is small. When the impressing energy is increased gradually, the area, whose temperature becomes high, is shifted in the sequence of c d e and, finally, all of the areas of the heat generating resistant bodies 3 become high-temperature areas substantially. Accordingly, the area of ink, molten and transferred in thermal transfer recording, is increased as such high-temperature area is increased. Recording density is increased linearly as the impressing energy is increased. According to this method, the area of the transferred ink may be controlled depending on the magnitude of the impressing energy whereby gradation may be represented while utilizing one dot as one printing element and medium tone recording of high resolution may be represented.

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] FIG. 2 shows the shape of a heating element of a conventional thermal head. This thermal head is constructed by arranging a plurality of such heating elements, and each of the heating resistors 3 has a signal electrode 1 and a common electrode 2 whose signal level is changed in accordance with the image signal to be recorded. It is composed of a shape sandwiched between. The heat generating element of a thermal head intended for halftone recording has a shape in which the central part of the heat generating resistor is narrowed down, as shown in 60-58877.

[Problems to be Solved by the Invention] However, in the conventional thermal head as shown in FIG. The temperature is only slightly higher in the center of the heating elements 3, where the number of heating elements 3 is smaller. Therefore,
When melting the ink on an ink sheet and transferring and recording onto recording paper, etc., there is a so-called binary process: depending on the magnitude of the applied energy, either an area of ink approximately equal to the area of the heating resistor is transferred, or no ink is transferred at all. It was a record. For this reason, if you try to record halftones in the conventional example, it is necessary to record using a pseudo gradation expression method using dither method, density pattern method, etc., and only images with coarse resolution per pixel can be obtained. Ta.

In addition, in conventional configurations in which the central part of the heating resistor, which is a thermal head for recording halftones, is constricted, the current is excessively concentrated in the constricted part, and the temperature repeatedly rises and falls, resulting in poor durability. There was a problem.

The present invention has been made in view of the above conventional example, and provides a recording head that makes it possible to express halftones by biasing the density of the current flowing through the heating resistor, and a thermal recording device using the recording head. The purpose is to

[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, in a recording head having a plurality of heat generating elements each formed by providing a heat generating resistor between a pair of electrodes, a first electrode connected to one side of the heat generating resistor and a first electrode connected to one side of the heat generating resistor; The heating resistor has a second electrode that is separated from the first electrode and connected to two sides other than the opposite side of the heating resistor to which the first electrode is connected.

Further, a thermal recording device using the recording head of another invention has the following configuration. That is, a first electrode connected to one side of the heating resistor;
a second electrode connected to two sides other than the opposite side of the heating resistor to which the electrode is connected; and a third electrode connected to the opposite side of the heating resistor to which the first electrode is connected. a recording head having a plurality of electrodes, an electrode selection means for selecting either the first electrode or the second electrode, and a multivalued image signal inputted to select the first electrode or the second electrode of the recording head in accordance with the gradation level of the image signal; It has a gradation determining means for determining the gradation of each of the heat generating resistors, and a recording means for applying electricity to each of the heat generating resistors according to the gradation to record information through the electrode selected by the electrode selection means.

[Function] In the above configuration, the recording head has a first electrode connected to one side of the heating resistor, and the first electrode is separated from the first electrode, and the recording head is connected to the opposite side of the heating resistor to which the first electrode is connected. and a second electrode connected to the other two sides, and by passing current between the first electrode and the second electrode, the current density in the heating resistor is changed to perform gradation recording. be able to.

Further, a thermal recording apparatus equipped with such a recording head inputs a multivalued image signal and determines the gradation level of each of the heating resistors of the recording head in accordance with the gradation level of the image signal. Then, electricity is applied to each of the heating resistors according to the gradation level through the electrodes of the recording head to perform recording.

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

FIG. 1 is an enlarged view showing the heat generation and electrode portions of the thermal head 10 of this embodiment, and parts common to the conventional example of FIG. 2 are designated by the same numbers.

In FIG. 1, 1 is a signal electrode for changing the applied voltage according to the image signal and energizing the heating resistor 3;
is a common electrode that applies a voltage to each of the heating resistors 3. Reference numeral 3 denotes a heat generating resistor which has a higher resistance value than the electrode and generates heat due to the current flowing from the common electrode 12 to the signal electrode l side. The signal electrode 1, the common electrode 12, and the heating resistor 3 form one heating element of the thermal head 10. The signal electrode l is a rectangular heating resistor 3
The common electrode is connected to one side 3a of the side 3a, and the common electrode extends from the vertex on the opposite side of the side 3a to which the signal electrode 1 is connected, on the two sides 3b of length y adjacent to that side 3a, to the length of X. 12 are connected. Moreover, 13 is an opening or an insulating part, and no electrode is connected to the opposite side 3c of the side 3a to which the signal electrode 1 is connected. A plurality of such heating elements are arranged in a line to constitute the thermal head 10.

Next, changes in the transfer area of the heating resistor 3 of the thermal head 10 having the above configuration will be explained with reference to FIG. 3.

When the energy applied to the heating resistor 3 of the heating element having the configuration shown in FIG. 1 is gradually increased, the ink transfer area increases as shown in FIG.
Since the current flowing through the heating resistor 3 tends to flow through the part where the distance between the electrodes is the shortest, the region shown in a in FIG. 3 becomes high in temperature when the applied energy is small. The density distribution of the current flowing through the heat generating resistor 3 is densest in the areas indicated by 301 and 302, and becomes coarser toward the center line of the heat generating resistor 3.

Therefore, as the applied energy is gradually increased, the portion of the heating resistor 3 that becomes high temperature transitions to the state shown in b in FIG. The area c in Figure 3
-x d→e, and finally almost the entire region of the heating resistor 3 becomes a high temperature region. Therefore, as the high temperature area increases, the area of ink that is melted and transferred in thermal transfer recording also increases.

FIG. 4 is a diagram showing the relationship between applied energy and recording density in a conventional heating resistor, and it can be seen that the recording density rises rapidly at a certain applied energy E1, indicating that this method can only be applied to binary recording.

On the other hand, FIG. 5 is a diagram showing the relationship between the applied energy to the heating resistor 3 of the thermal head 10 of the embodiment and the recording density, in which the recording density increases linearly as the applied energy increases.

Therefore, by using the configuration of the thermal head of this embodiment, the area of the ink to be transferred can be controlled by the magnitude of the applied energy. High-resolution halftone recording can be achieved using the sheet.

In addition, high durability can be achieved because there is no part where current is excessively concentrated, such as in a heat generating element that is narrowed down in the center of the heat generating resistor.

[Other Embodiments (Fig. 6)] Fig. 6 is a diagram showing the shape of a heating element in another embodiment of the present invention, in which 12-1 and 12-3 are divided common electrodes, and the signal electrode l is connected to the side 3b adjacent to the side 3a to which it is connected. 12-3 is a common electrode connected to the opposite side 3c of the side 3a to which the signal electrode 1 is connected.

In the configuration of FIG. 6, common electrodes 12-1, 12-2.
12-3 can be selectively used depending on the situation. That is, when it is desired to perform halftone recording using an ink sheet coated with fusible ink as in the above-described embodiment, exactly the same effect can be achieved by connecting the common electrodes 12-1 and 12-3. can get. On the other hand, when sublimable ink is used, the sublimable ink sublimates in an analog manner compared to the applied energy, so gradation recording can be performed without locally concentrated heating as in the above example. realizable.

Therefore, when using sublimation ink, it is preferable to have a structure that generates heat uniformly like the conventional heating element shown in FIG. 2, but if the structure shown in FIG. -2 and by not energizing the electrodes 12-1 and 12-3, it can be used in the same way as the conventional product.

It is convenient for the control operation of this embodiment to follow the configuration shown in FIG. 7.6 FIG. 3 are connected to a common power supply line 71 via an analog switch 70.
The transistor TR for driving the thermal head is turned on and off by the recording signal. For example, when using this thermal head for halftone recording using an ink sheet of meltable ink, the analog switch 7
0 switches 70a and 70c are made conductive, and the common electrode 12
-1.Turn on the power to 12-3.

On the other hand, when using sublimable ink, only 70b of the analog switch 70 is turned on, and electricity is applied to the heating resistor 3 through the electrode 12-2.

FIG. 8 is a diagram showing a modification of the thermal head of the first embodiment described above, in which parts common to the heating element of the embodiment described above are designated by the same numbers.

12a is a common electrode, 1 is a signal electrode, and 301 is a heating resistor. The electrode 12a is inserted into the side of the heating resistor 301 adjacent to the side 3a on the signal electrode side, so that the width of the heating element 301 is slightly narrowed. In this case as well, as in the first embodiment described above, the transfer area can be expanded by changing the applied energy as shown in FIG.

Next, an example of a thermal transfer recording device in which the thermal head 10 of the above-described embodiment is mounted will be described.

In FIG. 9, 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 transport device for picking up and transporting plain paper from the cassette 110. It's a motor. 1
A stepping motor 23 rotationally drives the platen 34 via a deceleration mechanism (not shown). Reference numeral 131 denotes a motor for raising/lowering the thermal head 10. When the motor 131 is driven, the thermal head 1° is pressed against the platen 34 (down state) through the ink sheet 32 and recording magazine, or is pressed against the platen 34 through the ink sheet 32 and the recording magazine. Separated (up state). Also, 139 is the ink sheet 32
The rotation of the motor 139 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 for temporarily storing input image data; 36 is an image data read out from the buffer memory 35;
- Image data conversion table for converting images, usually RO
It consists of lookup tables such as M.

37 is a head drive pulse control circuit whose details are shown in FIG.

FIG. 11 is a block diagram showing the configuration of the thermal head IO.

In the figure, reference numeral 11 denotes a heat generating element, and each heat generating element is made "C" based on the above-mentioned embodiment, and is provided for one line in the width direction of the recording paper. Reference numeral 70 denotes a heat generating element configured as shown in FIG. This is an analog switch used to switch the common electrodes in a thermal head equipped with an element.As shown in FIG.
-3:12-2). 233 is 1
A latch circuit that latches recorded data for a line, 234
is a shift register which 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 latched by the latch circuit 233 by the latch signal 235 and converted into parallel data. In this way, the recording data corresponding to each heating element is transferred to the latch circuit 233.
is maintained. Then, the timing and time of voltage application are determined by the strobe signal 5TB445, and the output transistor 231 connected to the AND circuit 232 with data is turned on. As a result, the common electrode 12 (or 12-1, 12-
2 or 12-2), the signal electrode 1 is energized to cause the heating element to generate heat.

Next, referring to FIG. 10, 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. It is. 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. With this, for example, when processing a color image, Y.

A gradation conversion decoder 440 performs gradation conversion for each of M and C colors.

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
In the case of a fusible ink sheet, MOD16 (4 bits) is counted. The gradation conversion decoder 440 compares the count value from the gradation counter 441 and the input pixel data, and when the pixel data is greater or equal, outputs "1" as the gradation data 444, and the pixel data is When is smaller, “0”
is outputting. The strobe signal generation circuit 442 generates the strobe signal 5TB4 a little later than the latch signal 235.
45, which drives the heating element and performs recording.

When using the thermal head shown in FIG. 6, the analog switch 70 switches the common electrode to 12-2 or 12-1 using the signal 446 to energize the heating element 3.
By switching to 12-3, it is possible to record a gradation image corresponding to, for example, the type of ink sheet used or the characteristics of image data.

FIG. 12 is a diagram showing the driving of the thermal head IO and the timing of the strobe signal STB in the embodiment.

The thermal head 10 is a line type head, and 120 is a 1
It shows the recording timing for each 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, the first STB signal B of one line of data is stored in the shift register 234.
, the gradation data 444 for , is transferred, and the latch signal 2
35, it is latched by the latch circuit 233. Next, strobe signal B1 is output to drive the heating element.

During this heat generation drive, the next gradation data 444 is input to the shift register 234, and when the STB signal 445 falls, it is latched into the latch circuit 233 by the latch signal 235. In this way, the STB signal is then output on B2. This operation is repeated 64 times (STB signal B l-8
114) is executed and recording of one line is completed.

That is, the gradation conversion decoder 440 inputs image data,
When the value of the m-th image data of the line to be recorded in the image is "20", the value of the gradation counter 441 is set to the m-th stage of the shift register 234 corresponding to the position of the pixel data. While referring to , data 444 is output a total of 64 times 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 B signal is output. The strobe signal generation circuit 442 executes such pulse width adjustment of the strobe signal STB.
It is. As described above, this strobe signal generation circuit 442 generates gradation data 4 corresponding to the type of ink sheet 2.
The width and period of the signal 445 are adjusted by inputting the signal 44 using a corresponding ROM table or the like.

FIG. 13 is a flowchart showing the recording process in the thermal transfer recording apparatus of the embodiment, which is stored in the ROM of the CPO 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 type of ink sheet 32 used is determined. For example, in the case of a thermal head equipped with a heat generating resistor as shown in FIG. 1
Switch the common electrode of o. The type of ink sheet 32 may be specified by a switch on an operation unit (not shown), or may be automatically determined by reading a mark attached to the ink sheet 32.Next, step S4 is performed. Then, the recording paper is picked up from the cassette 110 and conveyed to the recording position, and in step S5 the ink sheet 32 is conveyed so that the desired position of the ink sheet 32 is at the recording position. Next, proceed to step s6,
The printer 131 is driven to lower the thermal head 10.

In step S7, 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 12th
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 10 generates heat, and transfer recording is performed on the recording paper. Next, the process advances to step S8, where the recording paper and ink sheet 32 are conveyed by one line, and step S9
Check whether the recording process for one page is completed. Then, if the recording of one page is not completed, step S7
returns to the buffer memory 35 and stores the pixel data of the next line in the buffer memory 35.
, and the recording process described above 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 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 conveyed. Also, the platen 34 is rotated once and returned to its original position, and recording is performed in a different color.
Color recording can be performed on recording paper by performing this for the three colors. Also, depending on the type of ink sheet 32 and recording sheet used, the above-mentioned gradation data 44
The gradation width of 4, the pulse width of the strobe signal STB, etc. may be changed.

As mentioned above, by selectively using electrodes, it is possible to support both halftone recording using melt-type ink and halftone recording using sublimation ink, so one recording device can perform two types of recording. This has the effect of being compatible with other recording methods.

In the above embodiments, the heating resistors were all rectangular, but
The shape of the heat generating resistor is not limited to this in any way as long as it can be connected to electrodes on three sides.

Moreover, it is not necessarily necessary that all eight directions are straight lines, and furthermore, in this embodiment, nothing is connected to the opposite side of the heating resistor 3 to which the signal electrode 1 is connected, but some or all of the common electrode 12 may be connected.

[Effects of the Invention] As explained above, according to the present invention, a heating resistor, a signal electrode connected to one side thereof, and a signal electrode connected to two sides other than the opposite side of the heating resistor to which the signal electrode is connected. By configuring the heating element using the common electrode, it is possible to perform gradation recording on a dot-by-dot basis, thereby providing a recording head suitable for high-resolution halftone recording.

Furthermore, by providing an independent common electrode on the opposite side in addition to the above configuration, a recording head suitable for sublimable ink can be provided.

Furthermore, according to the present invention, the recording head can be adjusted to suit the type of ink sheet used, which has the effect of increasing the adaptability of the apparatus.

Furthermore, the thermal recording apparatus of this embodiment has the effect of being able to record images with good gradation.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the shape of the heat generating resistor and electrodes of the thermal head of the first embodiment, Fig. 2 is an enlarged view of the heat generating part of the conventional thermal head, and Fig. 3 is a diagram showing the heat generating resistor of Fig. 1. Figure 4 shows the relationship between applied energy and recording density when recording with a conventional thermal head. Figure 5 shows the relationship between applied energy and recording density when recording with a conventional thermal head. FIG. 6 is a diagram showing the relationship between applied energy and recording density when recording is performed using the thermal head of the example. FIG. 6 is a diagram showing another embodiment of the present invention. FIG.
An equivalent circuit diagram of the circuit that energizes the heating resistor shown in the figure, Figure 8 is a diagram showing an example of a thermal head in which the heating resistors of another embodiment share a common electrode, and Figure 9 is an example of the embodiment. 10 is a block diagram showing a schematic configuration of a head drive pulse control circuit; FIG. 11 is a diagram showing an electrical configuration of the thermal head; 12 The figure is a timing diagram showing the timing of signals applied to the thermal head, and FIG. 13 is a flowchart showing the recording process in the thermal transfer recording apparatus of the embodiment. In the figure, 1...Signal electrode, 12.12a...Common electrode, 3,301...Heating resistor, 10...Thermal head, 12-1.12-2.12-3... Divided common electrode, 13...insulating section, 70...analog switch.

Claims (4)

[Claims] (1) In a recording head including a plurality of heat generating elements formed by providing a heat generating resistor between a pair of electrodes, a first electrode connected to one side of the heat generating resistor; A second electrode separated from the first electrode and connected to two sides other than the opposite side of the heating resistor to which the first electrode is connected.
A recording head comprising: an electrode. (2) The recording head according to claim 1, wherein the opposite side of the heating resistor to which the first electrode is connected and the second electrode are insulated. (3) In a recording head including a plurality of heating elements formed by providing a heating resistor between a pair of electrodes, a first electrode connected to one side of the heating resistor; and a first electrode connected to one side of the heating resistor; a second electrode connected to two sides other than the opposite side of the heating resistor to which the electrode is connected; and a third electrode connected to the opposite side of the heating resistor to which the first electrode is connected. A recording head characterized by having: (4) a first electrode connected to one side of the heating resistor; a second electrode connected to two sides other than the opposite side of the heating resistor to which the first electrode is connected; a recording head having a third electrode connected to the opposite side of the heating resistor to which the electrode is connected; electrode selection means for selecting either the first electrode or the second electrode; gradation determining means for inputting an image signal and determining the gradation of each of the heating resistors of the recording head in accordance with the gradation of the image signal; and electrodes selected by the electrode selecting means. A thermal recording device comprising: recording means for recording by energizing each of the heating resistors according to the gradation.