JPS61164856A - Recording head and half tone recording method using the same - Google Patents

Abstract

PURPOSE:To enable highly stable half tone recording, by mounting a recording element of which the length to the direction crossing a paper feed direction or the moving direction of a recording head at right angles is twice or more the length to the moving direction and driving the same plural times. CONSTITUTION:A plurality of resistor elements 12 are arranged to the whole of a thermal head in a direction X and the part effective to thermal recording of each resistor element 12 is shown by an L1XL2 part and the longitudinal direction of L1 coincides with a paper feed direction Y and L2 is set to twice or more L1. In first printing, a dot (a) or a dot (b) having density higher than that of said dot (a) and larger than said dot (a) is obtained and, after recording paper is fed by P1 in the paper feed direction Y, printing is again performed to obtain a dot (c) or a dot (d) having density higher than that of said dot (c) and larger than said dot (c). If energy control is performed, for example, in two stages in printing as mentioned above, gradation of 5 stages is obtained.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a recording head such as a thermal head, a liquid crystal shutter array head, and an LED array head that are driven by an electronic switch, and to a recording head that performs halftone recording using such a recording head. It is about how to do it.

(Prior Art) In grayscale recording and color recording, pseudo-halftone recording methods such as dithering methods, and density/area gradation methods are used.

In the former, one pixel is made up of a plurality of dots, and shading is achieved by changing the number of dots present.

At this time, the recording density and size of each dot are constant.

Since each dot records a binary value of "0" or "1", the temperature stability is high, but since it requires a high-density recording head, the recording head itself is expensive, and it is difficult to say that it is a good method. For example, 4 pixels/mm, pixel configuration 4 dots x 4
In terms of dots, the recording dot density is 16 dots/m
m, the recording head.

The signal processing circuit also becomes expensive. Note that an IC (integrated circuit) used as a drive circuit accounts for a considerable portion of the price of a recording head.

On the other hand, in the density/area gradation method, by controlling the energy supplied to the recording element electrically or temporally, both the density and area of the recording dots can be made variable, thereby producing intermediate tones.

For example, if the recording dot density is 4 dots/mm, it is possible to obtain the same resolution as when the recording dot density is 16 dots/mm, which was shown as an example of the pseudo halftone recording method described above.

In this way, the density/area gradation method uses a low-density recording head, which reduces the price of the recording head, but it has the disadvantage of low temperature stability because the energy applied to the recording element must be controlled in an analog manner. have.

A resistor element as a recording element used in a thermal head as an example of a recording head is composed of a thick film or a thin film, and an example of the shape of a thin film type resistor element is shown in FIG. These are typically formed on ceramic substrates.

FIG. 2A shows a rectangular type resistor element 2. FIG.

In this case, the electrodes 4 and 6 are extended in the paper feeding direction (Y direction), and the length Q+ of the resistor element 2 in the paper feeding direction is the length Q+ of the resistor element 2 in the direction perpendicular to the paper feeding direction (X direction). It is longer than the length Q2. This takes into account the loss of efficiency due to heat escaping to the electrodes.

This is to improve the durability of the resistor.

Furthermore, as shown in FIGS. 2(B) and 2(C), a method of increasing the resistance by making the resistor elements 8, 10 long and thin by forming them into a meandering shape has also been used. This method has the advantage of increasing durability because the resistor film thickness can be increased. However, in both cases, Q1≧Q2.

(Objective) An object of the present invention is to provide an inexpensive halftone recording head and a highly stable halftone recording method using the recording head.

(Structure) In the present invention, the length L2 in the direction perpendicular to the paper feeding direction or the direction perpendicular to the moving direction of the recording head is at least twice the length Ll in the paper feeding direction or the moving direction of the recording head. This is a print head equipped with a print element.

Further, the present invention is a halftone recording method that uses the above recording head and performs recording of one pixel by driving the recording head multiple times and moving the recording paper or the recording head multiple times.

Examples of the present invention will be described in detail below.

FIG. 1(A) shows one resistor element 12 in an embodiment in which the present invention is applied to a thin film type thermal head.In the thermal head as a whole, a plurality of resistor elements 12 are arranged in the X direction. be done.

4.6 is an electrode.

The part of this resistor element 12 that is effective for thermal recording is LI
This is the L2 portion, and the length direction of LI coincides with the paper feeding direction (Y direction). And in the effective resistor element part.

L2≧2L1 It becomes.

When performing recording using this resistor element 12, by applying an appropriate amount of energy, a dot pattern 14 having a size close to the size LAXL2 of the resistor element 12 can be obtained as shown in FIG. 1(B). It will be done.

Note that the shape of the resistor element 12 is not limited to a meandering shape, and may be a rectangular shape, for example, if a rectangular shape with high resistance can be obtained.

FIG. 2 shows an embodiment in which the present invention is applied to a thick film type thermal head. In this embodiment, a strip resistor 16 is formed by a method such as screen printing, and individual strip resistors 16 are formed by a method such as screen printing. Electrodes 18 and common electrodes 20 are arranged alternately.

The area between the individual electrodes 18 and the common electrode 20 forms a resistor element for one dot.

In this embodiment as well, the relationship between the dimension L1 of the resistor element for one dot in the sheet feeding direction (Y direction) and the dimension L2 in the direction perpendicular thereto (X direction) is L2≧2L+.

Next, a halftone recording element using a thermal head equipped with these resistor elements will be explained with reference to FIGS. 3 and 4.

In FIG. 3, the size of the final print pixel is L3XL3, which is close to a square. First, the first print is the symbol a.
Obtain a dot with the density and size indicated by , or a dot with a higher density and larger size, then feed the recording paper by Pl in the paper feeding direction (Y direction), and then print again. Let us obtain a dot with the density and size shown by symbol C, or a dot with symbol d which has a higher density and larger size. In this way, if the two-stage energy-4 control is performed during printing, five gradations will be obtained as shown in the table below.

FIG. 4 shows an example in which pixels of the same size as those in FIG. 3 are formed by feeding the paper twice, and the feeding pitch of the recording paper at this time is P2. If two-step energy control is performed as in FIG. 3, nine gradations will be obtained.

If more gradations are required, increase the number of energy control steps, or increase the size ratio L2/L of the recording element to 3 or more, and increase the number of paper feeds per pixel. good.

In the above embodiments, a thermal head is used as an example of the recording head, but the present invention can be similarly applied to recording heads such as a liquid crystal shutter array head or an LED array head.

In addition, although the embodiment describes a method in which the recording head is fixed and the recording paper is fed, it can be similarly applied to a method in which the recording paper is fixed and the recording head is moved. .

Next, a circuit for driving the recording head of the present invention is shown in FIG. 5, which is a basic circuit of a direct drive type thermal head. Rr ”Rn is a resistor element,
Joule heat is generated in each of the resistor elements R+-Rn in accordance with recorded information to perform thermal coloring. First, print data is DI
Shift register 2 at the timing of clock signal GK.
2, and when the transfer of data for -line is completed, it is transferred in parallel to the latch 24 by the load signal LD. Next, switching transistors T1 to Tn connected to each resistor element R+=Rn are controlled on/off by a printing control signal (strobe) SB via AND gates Gl-Gn, and heating for recording is performed.

Usually, part A indicated by a chain line is composed of an IC.

An example of a method for controlling the drive energy in multiple stages when driving a thermal head using such a drive circuit will be described with reference to FIGS. 6 and 7. This method is a method for controlling the number of pulses applied to the resistor element.

In FIG. 6, 30 is the thermal head shown in FIG. 5, 32 is an A/D converter that converts analog image information into a digital signal, 34 is a RAM that stores the digital signal, and 36 is a load signal LD. 38 is an oscillator that generates a pulse signal for the printing control signal n; 40 is a gradation level; RO that stores the program that converts the number of pulses into the number of pulses
M, 42 is a counter that counts the number of pulses applied as the print control signal SB based on the number of pulses set by the ROM 40. A thermistor 44 is incorporated in the oscillator 38, and the cycle of the pulse signal applied as the print control signal (2) is controlled in accordance with the temperature.

The operation when performing 8-gradation recording using the circuit shown in FIG. 6 will be explained with reference to the time chart shown in FIG. 7.

The image information is converted into a digital signal line by line by the A/D converter 32 and stored in the RAM 34. When the image information is input to the data input terminal DI of the thermal head 30 as data for each gradation, it is sent from the controller 36. The number of pulses corresponding to gradation 0 is set from the ROM 40 to the counter 42 by the signal, and the load signal LD is applied from the controller 36 to the thermal head 30, and the oscillator 3
A print control signal 1 is applied to the thermal head from 8 to start energizing the resistor. When the counter 42 counts a predetermined number of pulses, the controller 36 next
The data for gradations 1 to 4 are input to the thermal head, and in the same manner as described above, a pulse signal of only pulses corresponding to gradation 1 stored in the ROM 40 is applied to the resistor element.

Similarly, when the pulse signal application up to floor 117 is completed, the recording paper is fed by a predetermined pitch, and data for the next line is written into the RAM 34 during the paper feeding period.
In this example, in order to shorten the recording time, recording is performed by one overlapping strike (sum of the number of pulses), and data transfer and pulse application are performed in parallel. For further details, please refer to the patent application in 1973.
8-116428.

In the examples shown in FIGS. 6 and 7, energy control is controlled by the number of pulses of the print control signal, but it may also be controlled by changing the pulse width of the print control signal.

Furthermore, such an energy control circuit can be applied not only to thermal heads but also to other recording heads.

(Effects) According to the present invention, it is possible to reduce the number of ICs that account for a major part of the price of the print head, thereby making it possible to achieve a low-cost print head. For example, 4 dots/m
It is possible to obtain performance close to that of the conventional 8 dot/mm configuration recording head. In that case 208m
A conventional recording head with a width of 208 mm and a width of 8 dots/mm requires 26 64-bit ICs, but the recording head of the present invention with a width of 208 mm and a width of 4 dots/mm, which has the same performance, requires 26 64-bit ICs. , only 13 64-bit ICs are required.
In this way, the price of IC will be halved.

Further, according to the present invention, it is possible to perform halftone recording more stably than the density/area gradation method.

As described above, according to the present invention, the thermal head, the LE
In a recording head such as a D array head or a liquid crystal shutter head, halftone recording with high accuracy can be achieved at low cost.

[Brief explanation of the drawing]

FIG. 1(A) is a plan view showing a resistor element of one embodiment, FIG. 1(B) is a plan view showing a printed dot pattern by the resistor element, and FIG. 2 is a plan view of a resistor element of another embodiment FIGS. 3 and 4 are schematic diagrams explaining the recording method of the present invention, FIG. 5 is a block circuit diagram showing a thermal head drive circuit, and FIG. 6 is a circuit for energy control. 7 is a time chart showing the operation of the circuit diagram of FIG. 6. FIGS. 8(A) to 8(C) are plan views showing conventional resistor elements, respectively. 12.16...Resistor element as a recording element,
Y: Paper feeding direction, X: Direction perpendicular to the paper feeding direction.

Claims (4)

[Claims] (1) Equipped with a recording element in which the length L_2 in the direction perpendicular to the paper feeding direction or the direction perpendicular to the recording head movement direction is more than twice the length L_1 in the paper feeding direction or the printing head movement direction. recording head. (2) The recording head according to claim 1, wherein the recording element is a resistive element of a thermal head. (3) Equipped with a recording element in which the length L_2 in the direction perpendicular to the paper feeding direction or the direction perpendicular to the recording head movement direction is more than twice the length L_1 in the paper feeding direction or the printing head movement direction. A halftone recording method in which one pixel is recorded by driving the recording head multiple times and moving the recording paper or the recording head multiple times. (4) The halftone recording method according to claim 3, wherein energy control is performed in multiple stages when driving the recording head.